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20th Anniversary International Conference on
Transparent Optical Networks ICTON 2018
10th Anniversary Sub-Wavelength Photonics Conference SWP 2018


Bucharest, Romania, July 1-5, 2018


Co-located with:

  • 17th European Symposium on Photonic Crystals (ESPC)
  • 17th Workshop on All-Optical Routing (WAOR)
  • 15th Global Optical & Wireless Networking Seminar (GOWN)
  • 14th Reliability Issues in Next Generation Optical Networks Workshop (RONEXT)
  • 14th Optical Wireless Workshop (OWW – former Free-Space Optics Session)
  • 14th Photonic Integrated Components & Applications Workshop (PICAW)
  • 13th Nanophotonics for All-Optical Networking Workshop (NAON)
  • 13th Special Session on Photonic Atoms & Molecules (PAM – former MPM)
  • 13th Special Session on Novel Glasses for photonic devices
  • 11th Special Session on Market in Telecommunications (MARS)
  • 10th Anniversary Workshop on Broadband ACCESS (former ACCORDANCE)
  • 9th Workshop on Communication in Transportation Systems (CTS)
  • 8th Workshop on Green Optical Communications (GOC)
  • 8th Special Session on Microwave Photonics (MWP)
  • 5th Workshop on Big Data Analytics and Network Optimization (BigNeO − former NeO)
  • 4th Workshop on Technology for Data Center Interconnects (DACINT)
  • 4th Workshop on Datacenter Networks (DCN)
  • 4th Workshop on 5G Transport Networks (5GT)
  • 3rd Workshop on Fiber-Wireless Network Technologies and Architectures towards 5G and Beyond (FiWiN5G)
  • 3rd Workshop on Quantum Photonics (QPhot)
  • 3rd Workshop on Multi-Layer Network Orchestration (NetOrch)
  • 2ndWorkshop on Novel Optical Amplifiers (NOA)
  • 2nd Workshop on Label-Free Super-Resolution and Sensing (LFSRS)
  • 2nd Workshop on High Capacity SDM-WDM Optical Networking (SDM-WDM)
  • 2nd Workshop on Flexible and High-Capacity Optical Networks (Flex-ON)
  • 1st Workshop on Optical Microscopy Techniques (OMT)


ICTON invited presentations:

Miguel Andrés

In-fiber fractional signal processing: Recent results and applications
C. Cuadrado-Laborde, L. Poveda-Wong, A. Carrascosa, J. L. Cruz, A. Díez, and M. V. Andrés
Universidad de Valencia, Burjassot, Spain

Photonic signal processing based on mathematical operators -as for example, conventional differentiators and integrators- is particularly well suited to overcome the speed and bandwidth limitations of electronics. In the Laboratory of Fiber Optics of the University of Valencia we work on the development of in-fiber time-domain fractional operators and their applications. In the last years we have made some specific proposals to perform photonic fractional differentiation (PFD), photonic fractional integration (PFI), photonic fractional Hilbert transform (PFHT), and photonic fractional Fourier transform (PFFT), using fiber-based technologies. Recently, we have been able to implement experimentally some of these theoretical proposals, and we have found specific applications for the 0.5th-order differentiation and the photonic fractional Fourier transform in the area of phase recovery of optical pulses.

Hovik Baghdasaryan
Single- and double-mode light generation in DFB fiber laser: Wavelength-scale electromagnetic modelling by the method of single expression
H. Baghdasaryan1, T. Knyazyan1, T. Hovhannisyan1, M. Marciniak2, E. Leitgeb3, S. Sujecki4, S. Taccheo5, and T. Benson6
1National Polytechnic University of Armenia, Yerevan, Armenia
2National Institute of Telecommunications, Warsaw, Poland
3Technische Universitat Graz, Austria
4Wroclaw University of Technology, Poland
5Swansea University, UK
6University of Nottingham, UK

Distributed feedback (DFB) semiconductor and fiber lasers are widely used in different area of science, technology, medicine, etc. Single- and double-mode operation of fiber lasers is very advantageous for telecommunication, spectroscopy, sensors applications, microwave generation, etc. However, there is a lack of a wavelength-scale electromagnetic analysis of such fiber lasers at the single- and double-mode radiation. In the current work the results of correct wavelength-scale electromagnetic analysis of radiation of DFB fiber lasers operating in single- and double-mode are presented. For wavelength-scale analysis the non-traditional method of single expression is used. In accordance with the known information, single- and double-mode radiation from DFB fiber laser is observed at single-phase-shift in the middle of permittivity sinusoidal modulation of an amplifying fiber and equally spaced two-phase-shifts, correspondingly. Numerically obtained wavelength-scale distributions of electric field component and power flow density within the DFB amplifying fiber will be useful in designing single- and double-mode radiating DFB fiber lasers.

Mihai Bănică
ROADM versus OXC architectures and performance
M. Bănică and V. Croitoru
University Politehnica of Bucharest, Romania

The prevalent network node architecture in the currently deployed optical transport networks is the reconfigurable optical add/drop multiplexer (ROADM). To enable a flexible and efficient network configuration, the ROADMs have to be colorless, directionless, and contentionless (CDC). The more flexibility is required, the more complex and costly become the ROADM architectures. An optical cross-connect (OXC) equipped with an optical matrix capable of switching any input port on any output port would provide the benefits of CDC with less architectural complexity. However, until recently OXCs have not been commercially available, and have not been so far deployed. Considering characteristics of realistic transport network topologies, we evaluate in this paper the current prevalence of ROADM. Then, based on the near future challenges of optical transport networks, particularly the Data Center Interconnectivity (DCI) requirements, the scalability of node architectures for both ROADM and OXC is investigated, in order to estimate the practical possibility of OXC deployments in the near future.

Hans Brunner
Precise noise calibration for CV-QKD
H. H. Brunner, S. Bettelli, L. C. Comandar, F. Karinou, D. Hillerkuss, F. Fung, Dawei Wang, S. Mikroulis, A. Poppe, and M. Peev
Huawei Technologies Dusseldorf GmbH, Munich, Germany

Continuous-variable quantum-key-distribution (CV-QKD) devices, conveniently based on standard components from the domain of coherent optical communication, can guarantee an information-theoretic secure-key expansion. Their security analysis assumes that all power lost in the channel, as well as channel noise in excess with respect to the shot noise, is due to an eavesdropper limited only by quantum mechanics. Quantifying the excess noise, which typically has significantly less power than the shot noise, is essential for secure-key generation.  In this article a heterodyne-receiver setup capable of measuring optical power with an extremely high sensitivity (approximately -130 dBm within a 12.5 MHz  bandwidth at 1550 nm , corresponding to a power 40 dB below the shot noise) is analysed and demonstrated in a CV-QKD prototype device. Such accuracy is achieved by means of continuous calibration and long-time averages.

Piero Castoldi
Optical white box: Modeling and implementation
P. Castoldi1, A. Giorgetti1, A. Sgambelluri1, G. Cecchetti1, N. Sambo1, A. Ruscelli1, I. Cerutti1,2, and F. Cugini3
1Scuola Superiore Sant’Anna, Pisa, Italy
2Nokia, Milan, Italy
3CNIT, Pisa, Italy

Disaggregated optical technologies have the potential to provide cost-effective and vendor-neutral optical node solutions particularly suitable for metro networks. Differently with respect to traditional proprietary networks, specific additional design, modelling, control and management operations have to be carefully defined and standardized. In this paper, the most relevant disaggregated optical devices to be supported and controlled are first presented. More specifically, transponders, ROADMs, and optical amplifiers are discussed in terms of vendor-neutral YANG models and NETCONF control. Then, the implementations of the related software agents is presented, together with a Software Defined Networking (SDN) Controller implementation within ONOS. The implementations are validated in a disaggregated optical network testbed, showing successful interoperability and the experimental demonstration of complex transmission and optical power configurations.

Jiajia Chen
Telecom compatibility of QKD in high capacity SDM/WDM systems
R. Lin, A. Udalcovs, O. Ozolins, X. Pang, L. Gan, L. Shen, M. Tang, S. Fu, S. Popov, C. Yang, W. Tong, D. Liu, T. Ferreira da Silva, G. B. Xavier, and J. Chen
KTH Royal Institute of Technology, Sweden

Kostas Christodoulopoulos
DEPLOY tool: Incrementally planning marginless elastic optical networks
A. Kretsis1,2, P. Soumplis1, K. Christodoulopoulos1,2, and E. Varvarigos1,3
1Department of Electrical and Computer Engineering, National Technical University of Athens, Greece
2Computer Technology Institute and Press - Diophantus, Patras, Greece
3Department of Electrical and Computer Systems Engineering, Monash University, Australia
Currently, the hardware (equipment) and software (including planning and operation tools) are both provided by optical equipment vendors, leading to the so called vendor lock. We present DEPLOY, a tool for planning and operating optical networks that uses generic vendor-agnostic models. We demonstrate its capabilities through the use case of incrementally planning an optical network over multiple periods under evolving traffic and physical layer conditions. Using DEPLOY we can evaluate the benefits of planning with reduced as opposed to planning with end-of-life margins.

Virginia D’Auria
A plug-and-play synchronisation scheme for quantum networks
B. Fedrici, L. A. Ngah, O. Alibart, F. Kaiser, L. Labonté, V. D’Auria, and S. Tanzilli
Université Côte d’Azur, CNRS, Institut de Physique de Nice, France
In the context of digital society, quantum information technologies promise data management solutions with performances greatly exceeding those of classical resources. This vision has motivated multiple works towards the realization of quantum networks where remote quantum processors are connected via optical quantum communication channels. In this context, in the last years, extremely encouraging works have reported on long distance quantum teleportation for data transfer in presence of transmission losses and channel de-coherence, and on the demonstration of quantum memories and interfaces for information storage. Nevertheless, to date, no universal protocol has never been demonstrated to allow an accurate and reliable synchronization of the different network building blocks. Synchronization solutions presented so far in the context of quantum teleportation strictly depend on the considered experimental configuration and mostly rely on complex control systems whose performances are limited by feedback signal finite speed and unavoidable timing jitters in opto-electronics conversions. In this work, we present a novel and an extremely simple synchronization scheme that can be easily implemented with current technologies. More in details, our idea exploits the advances of classical telecom technology and non-linear optics to distribute to the different network blocks a plug-and-play, common, all-optical timing reference. Provided adequate non-linear optical stages are available, this solution can be used to supply a clock to any distant quantum device over the network, without being restrained to a specific experimental configuration or number of nodes. As a proof of principle, we demonstrated it with two non-linear optical sources and one relay node as for the case of many entanglement swapping realizations: tests over increasing distance up to 100 km show the reliability of the protocol.

Francesco Da Ros
Nonlinearity compensation through optical phase conjugation for improved transmission reach/rate
F. Da Ros1, M. P. Yankov1,2, E. P. da Silva1, M. Lillieholm1, P. M. Kaminski1, P. Guan1, Hao Hu1, A. T. Clausen1, M. Galili1, and L. K. Oxenløwe1
1DTU Fotonik, Technical University of Denmark
2Fingerprint Cards ApS, Herlev, Denmark

Signal distortion caused by nonlinearity during transmission is one of the key challenges that must be addressed in order to provide the increase in data rates required by the ever growing demand for high-speed connectivity. Several nonlinearity mitigation and compensation techniques have been proposed and investigated throughout the recent years [1] focusing on either the digital [1, 2] or the optical [3-16] domain. While digital nonlinearity compensation through digital backpropagation can effectively erase the distortion caused by intra-channel nonlinearity [2], the available receiver bandwidth prevents it from compensating for inter-channel effects by using practical receivers. Alternatively, inter-channel effects can be compensated for by using all-optical approaches such as optical phase conjugation (OPC) which potentially enables full-band nonlinearity compensation [2]. OPC has been re-discovered in the past few years with several impressive demonstrations being reported [3-9], however a number of challenges still need to be addressed. In this talk, we review our recent efforts on investigating the impact of link non-ideality on the nonlinearity compensation provided by practical implementations of OPC, caused by e.g. the inherent wavelength shift introduced by four-wave mixing-based OPC [10, 11] and sub-optimum positioning of the OPC within the link [12]. Additionally, the potential for joint digital and optical compensation by combining OPC with the powerful probabilistic shaping (PS) will be discussed [13]. Finally, we will touch upon the use of nonlinear material for OPC beyond the more classical highly nonlinear fibers (HNLFs) [2-6, 8-13] and periodically poled lithium niobate (PPLN) [7], by reviewing our recent results on OPC using silicon waveguides [14-16].
[1] A.D. Ellis, et al., Performance limits in optical communications due to fiber nonlinearity, Advances in Optics and Photonics 9(3), 429-503 (2017).
[2] I. Sackey, et al., Kerr nonlinearity mitigation: mid-link spectral inversion versus digital backpropagation in 5x28-GBd PDM 16-QAM signal transmission, Journal of Lightwave Technology 33(9), 1821-1827 (2015).
[3] A.D. Ellis, et al., 4 Tb/s transmission reach enhancement using 10 × 400 Gb/s super-channels and polarization insensitive dual band optical phase conjugation, Journal of Lightwave Technology 34(8), 1717-1723 (2016).
[4] I. Sackey, et al., Kerr nonlinearity mitigation in 5× 28-GBd PDM 16-QAM signal transmission over a dispersion-uncompensated link with backward-pumped distributed Raman amplification, Optics Express 22(22), 27381-27391 (2014).
[5] F. Da Ros, et al., Kerr nonlinearity compensation in a 5× 28-GBd PDM 16-QAM WDM system using fiber-based optical phase conjugation, in Proc. ECOC 2014, paper P. 5.3.
[6] K. Solis-Trapala, et al., Nearly-ideal optical phase conjugation based nonlinear compensation system, in Proc. OFC 2014, paper W3.F.8.
[7] T. Umeki, et al., Simultaneous nonlinearity mitigation in 92 × 180-Gbit/s PDM-16QAM transmission over 3840 km using PPLN-based guard-band-less optical phase conjugation, Optics Express 24(15), 16945-16951 (2016).
[8] Y. Sun, et al., Optical nonlinearity mitigation of 6×10GBd polarization-division multiplexing 16-QAM signals in a field-installed transmission link, in Proc. OFC 2017, paper Th.3.J.2.
[9] H. Hu, et al., Fiber nonlinearity mitigation of WDM-PDM QPSK/16-QAM signals using fiber-optic parametric amplifiers based multiple optical phase conjugations, Optics Express 25(3), 1618-1628 (2017).
[10] I. Sackey, et al., Waveband-shift free optical phase conjugator for spectrally efficient fiber nonlinearity mitigation, Journal of Lightwave Technology, pre-print DOI: 10.1109/JLT.2018.2790799 (2018).
[11] F. Da Ros, et al., Impact of signal-conjugate wavelength shift on optical phase conjugation-based transmission of QAM signals, in Proc. ECOC 2017, paper P1.SC4.66.
[12] F. Da Ros, et al., Link-placement characterization of optical phase conjugation for nonlinearity compensation, in Proc. OFC 2018, paper W3E.3.
[13] M.P. Yankov, et al., Experimental comparison of probabilistic shaping with online PMF optimization and mid-link OPC, submitted to CLEO 2018.
[14] D. Vukovic, et al., Multichannel nonlinear distortion compensation using optical phase conjugation in a silicon nanowire, Optics Express 23(3), 3640–3646 (2015).
[15] A. Gajda, et al., Silicon waveguide with lateral p-i-n diode for nonlinearity compensation by on-chip optical phase conjugation ion, in Proc. OFC 2018, paper W3E.4.
[16] F. Da Ros, et al., Nonlinearity compensation for dual-polarization signals using optical phase conjugation in a silicon waveguide, submitted to CLEO 2018.

Ivan Djordjevic
LDPC codes derived from quasi-cyclic code design suitable for optical communications
Xiaole Sun and I. B. Djordjevic
University of Arizona, Department of Electrical and Computer Engineering, Tucson, USA

We propose a rate-adaptive forward error correction (FEC) scheme based on spatially-coupled (SC) LDPC codes derived from quasi-cyclic (QC) LDPC codes and describe the corresponding field-programmable gate array (FPGA) implementation. By FPGA emulation, we show that, for comparable computational complexity, the proposed LDPC codes provide larger coding gain and lower error floor when compared to the QC-LDPC template code. Thanks to their hardware friendly structure, the proposed class of SC-LDPC codes represents a promising candidate for the next-generation intelligent optical communication systems and networks.

Ivan Djordjevic
Optimal constellation shaping in optical communication systems
Zhen Qu and I. B Djordjevic
University of Arizona, Department of Electrical and Computer Engineering, Tucson, USA

In optical communications systems, Shannon limit can be closely approached by properly chosen constellation shaping schemes. Both probabilistic shaping (PS) and geometric shaping(GS) can be applied to M-ary quadrature amplitude modulation (QAM) to obtain the shaping gain. In this paper, mutual information (MI) is used as a metric to analyze the performances of regular/GS/PS-8/16/32QAM formats. In a linear amplified spontaneous emission (ASE) noise dominated system, our numerical results show that the MI performances of the GS-8/16QAM are better than that of regular 8/16QAM and PS-8/16QAM; the largest shaping gains can be separately reached by PS-32QAM and GS-32QAM. Then we experimentally compare the performances of regular/GS/PS-16QAM formats over a 100km fiber transmission link. Our numerical and experimental results are very useful in selection of the optimal constellation shaping for a given MQAM based optical communication system.

Octavia Dobre
Training-aided joint frame and frequency synchronization for THP FTN coherent optical systems
Shu Zhang1, O. Omomukuyo1, O. A. Dobre1, Xiang Lin1, and Deyuan Chang2
1Memorial University, St. John’s, Canada
2Infinera, Ottawa, Canada

A joint frame and frequency synchronisation algorithm is proposed for Tomlinson-Harashima precoding-based faster-than-Nyquist (FTN) coherent optical systems. The algorithm is developed by using training sequences based on Golay complementary sequences. Simulation results of a 32-Gbaud FTN system show that the algorithm provides accurate estimates over an optical signal-to-noise ratio (OSNR) range from 10 to 25 dB. When considering the first-order polarisation mode dispersion and using these same training sequences for the equaliser, the algorithm works properly and gives performance similar to when the frequency offset is perfectly known. The required OSNR at a bit error rate of 2×10-2 is about 13 dB and 18.8 dB for 4-QAM and 16-QAM systems, respectively.

John Dudley
Real time measurements of ultrafast instabilities in nonlinear fibre optics: Recent advances
J. M. Dudley1, M. Närhi2, P. Ryczkowski2, C. Billet1, J-M. Merolla1, G. Genty2, and P.-A. Lacourt1
1Institut FEMTO-ST, UMR 6174 CNRS-Université Bourgogne Franche-Comté, Besançon, France
2Laboratory of Photonics, Tampere University of Technology, Tampere, Finland

There have been many dramatic advances in the real-time measurement of ultrafast optical instabilities, which have yielded many new insights into the underlying physics. In this paper, we review our recent work using time lens and dispersive Fourier transform techniques to studies of modulation instability, supercontinuum generation and to the transient regime of mode locking in a dissipative soliton laser. We make particular connections where relevant to the field of rogue waves and analogies with other physical systems.

Andrew Ellis
Limits of optical fibre communication systems
A. Ellis, F. Ferreira, Tingting Zhang, and M. Al Khateeb
Aston Institute of Photonic Technologies, Aston University, Birmingham, UK

In this presentation, we will review the historical evolution of performance predictions for optical communication systems, including single channel systems, soliton systems and the so called GN/EGN model. We will describe how such predictions have be made from the outset of optical communications research and their present form, accurately predicting the performance of coherently detected communication systems and establishing the fundamental limits of nonlinearity compensation.

Vincenzo Eramo
Processing and bandwidth resource allocation in multi-provider NFV cloud infrastructures interconnected by elastic optical networks
V. Eramo and F.G. Lavacca
DIET, University of Roma Sapienza, Rome, Italy

The paper proposes and investigates solutions to the computing and bandwidth resource allocation problem in Multi-Provider Network Function Virtualization (NFV) environment. The scenario is characterized by Cloud Infrastructures (CI) managed by different providers and interconnected by an Elastic Optical Networks (EON). The objective is to allocate resources for a given number of Service Function Chains (SFC) known in advance so as to minimize the sum of the processing and bandwidth costs and to take into account both the different processing costs charged by the Cloud Infrastructure (CI) providers and the sub-carrier consecutiveness, spectrum continuity and spectrum clash constraints. In particular we evaluate the operational cost saving that the proposed solutions allow us to obtain with respect to the case in which traditional resource allocation algorithms are applied.

Josep Fàbrega
Optical performance monitoring systems in disaggregated optical networks
J. M. Fàbrega, M. Svaluto Moreolo, and L. Nadal
Centre Tecnològic de Telecomunicacions de Catalunya, CTTC, Castelldefels, Spain
In this talk, optical performance monitoring is presented as enabler to address the key challenges in disaggregated optical networks. In fact, data plane elements for non-intrusive monitoring of different modulation formats will be discussed, reviewing different options based on high resolution spectral analysis. Furthermore, we will report how the information retrieved by these monitoring probes can be used to actually control the transceivers and other data plane elements, emphasizing on the suitable figures of merit to be delivered to the SDN control, orchestration and management planes.

Didier Felbacq
A hybrid method for solving scattering problems by complex bodies
A. Gourdin, P. Genevet, and D. Felbacq
Laboratoire Charles Coulomb, Université de Montpellier, France

The Discrete Dipole Approximation is a well-documented method to solve scattering problems by inhomogeneous or complicatedly shaped bodies. However, it is not well-suited to deal with several disconnected obstacles. In the present work, we present a modified version of the DDA that uses a magnetic and an electric dipole per site to obtain the field scattered by one body. This field is then represented by means of the Method of Fictitious Sources in order to derive an efficient multiple scattering theory that allows to solve the problem of the scattering of a wave by a periodic or aperiodic collection of resonators.

Filipe Ferreira
Impact of linear mode coupling on the nonlinear transmission performance of few-mode fibres
F. M. Ferreira, C. S. Costa, S. Sygletos, and A. D. Ellis
Aston Institute of Photonic Technologies, Aston University, Birmingham, UK

This paper reviews and extends the study of nonlinear transmission performance of few-mode fibre links operating in all different linear mode coupling regimes for different mode delay maps. The optimum link configurations minimizing the nonlinear penalty at practical levels of equalization complexity are presented. Finally, the limits of the extension of the single-mode Manakov approximation to the multi-mode case are accurately validated against a fully stochastic model.

Fatima Garcia Gunning
Impact of analogue pre-filtering for spectral roll-off improvement in spectral efficient transmitters
A. Kaur and F. C. Garcia Gunning
Tyndall National Institute, Cork, Ireland
Spectral Shaping plays a significant role in increasing the spectral efficiency of optical transmission systems. However, most of the spectral shaping methods reported so far have remained very complex using digital processing techniques that requires large number of filter taps for optimal performance. In this paper, we proposed a solution for reducing spectral roll-off factor using wavelength selective switch (WSS) to reduce number of digital filter taps. The talk will focus on the impact on reducing the spectral roll-off with the WSS’s resolution and bandwidth.

Olivier Gauthier-Lafaye
Fabrication of doubly-corrugated zero-contrast-grating for broadband pixelated filtering in the mid‑IR range
L. Macé1,2, O. Gauthier-Lafaye1, A. Monmayrant1, H. Camon1, P. Dubreuil1, L. Mazenq1, M. Oussalah2, A. Hervy2, F. Pradal2, and H. Leplan2
1LAAS-CNRS, Université de Toulouse, CNRS, France
2Safran Reosc, Saint-Pierre-du-Perray, France

Zero-contrast grating filters (ZCG) car be used to implement efficient bandpass transmission filter with narrow bandwidths of a few nanometers. In a precedent article [1], we have illustrated the validity of the ZCG approach for the mid-IR range using germanium and calcium fluoride, as well as the possibility to increase both the bandwidth and the angular acceptance of such filters by a decade or more using a double corrugation scheme for the grating. However, when it comes to fabricating such devices, conventional semiconductor methods can’t be straightforwardly applied because of the specific requirements of the infrared materials used. Adapting specific methods of the semiconductor industry, we manage to fabricate such devices. A first optical characterization is performed.
[1] B. Portier, F. Pradal, M. Oussalah, H. Sik, J. Fleury, and P. Laprat, Pixelated thin film coating on detector for multispectral infrared imaging, in Conference on Optical Interference Coatings, OSA Technical Digest, 2016, paper MC.8.

Ivan Glesk
Chirp management in communication systems with picosecond data carriers using SOA
M. S. Ahmed and I. Glesk
Electronics and Electrical Engineering Department, University of Strathclyde, Glasgow, UK

To preserve the integrity of fiber transmission in incoherent systems using picosecond carriers the dispersion must be controlled with high accuracy. This can be very challenging task in a multi-wavelength environment under changing conditions. Under these circumstances the tuneability of the control mechanism is desired. In this respect we have investigated the use of Semiconductor Optical Amplifier (SOA) for the multicolor tuneable dispersion control via chirp modification of data carriers. The successful demonstration of this technique was conducted in a 16 km long outdoor fiber testbed.

Miguel Gonzalez-Herraez
Transforming the fiber-optic network into a dense and ultrasensitive seismic sensor array
A. Garcia-Ruiz, R. Magalhães, L. Costa, F. J. Cobo, H. F. Martins, M. R. Fernández-Ruiz, S. Martin-Lopez, and M. Gonzalez-Herraez
Dept. of Electronics, University of Alcalá, Madrid, Spainin

We show a technology capable of performing position-resolved measurement of nanostrain perturbations along a conventional optical fiber cable, with meter-scale resolution. This technology can be deployed in already existing networks to achieve a dense and ultrasensitive seismic sensor array. Applications ranging from seismic protection to intrusion detection in critical infrastructures are explored.

Ortwin Hess
Ultraslow waves and photonic quantum dynamics on the nanoscalee
O. Hess, The Blackett Laboratory, Imperial College London, UK
Recent broad interest in the physics and applications of ultraslow waves in nanoscale structures range from light-waves or surface plasmons in nanoplasmonic devices to sound waves in acoustic-metamaterial waveguides, as well as plasmons and phonon polaritons in graphene and van der Waals crystals. Here we highlight that combining ultraslow waves with active photonic quantum materials opens up new domains for science, materials physics and engineering, providing the foundation for novel photonic quantum and communication technologies and nanolasing. We will outline the underlying physics of ultraslow waves on the nanoscale and discuss far-reaching opportunities resulting from a combination of ultraslow waves and active photonic quantum materials enabling single quantum emitter strong coupling. The ultrafast spatio-temporal dynamics of cavity-free stopped-light nanolasing and surface plasmon polariton condensation in nanoplasmonic heterostructures are yet further reflections of the special properties of light in the vicinity of stopped-light singularities, while a combination of stopped-light modes with epsilon-near-zero and topological materials with vanishing refractive index offer further exciting possibilities for nanophotonics.

Adrian Ionescu
The future of electronics: Silicon to cloud technologies
A. M. Ionescu, Nanolab, Ecole Polytechnique Fédérale de Lausanne, Switzerland
We will present and discuss some of the great research challenges and opportunities related to 21st century energy efficient computing and sensing devices and systems, in the context of the Internet of Things (IoT) revolution. In the future, major innovations will require holistic approaches encompassing silicon and cloud technologies. There is still an important role to be played by innovations in energy efficient technologies, devices, and system design, building on the success of silicon CMOS. Electronic and optoelectronic technologies may co-exists and boost the performance of future systems performing computing, sensing and communications in a new ecosystem centered on big/abundant data.

Joseph Kahn
Improving the capacity of terrestrial and submarine systems via channel power optimization
J. Krause Perin, I. Roberts, and J. M. Kahn
Stanford University, E. L. Ginzton Laboratory, Department of Electrical Engineering, Stanford, USA
Channel power optimization can yield significant improvements in system capacity and margin with virtually no additional complexity. We review techniques for channel power optimization in terrestrial and submarine links. For terrestrial systems, either in mesh networks or point-to-point links, optimizations maximizing capacity or minimum margin can be cast as convex optimization problems, with the SNR in each channel expressed as a convex function of the channel powers. Kerr nonlinearities are modeled using a discretized version of the Gaussian noise model. These optimizations lead to significant gains over flat power allocation. For example, in the 14-node NSFNET network, a margin gain of 1.5 dB on average is achieved through power optimization, as compared to an optimized spectrally flat power allocation. In ultra-long submarine links, the capacity is ultimately limited by the electrical power fed from the shores to the undersea amplifiers. Recent works have focused on maximizing capacity by optimizing the number of spatial dimensions. We show, however, that modeling erbium-doped fiber amplifier physics and optimizing over wavelength as well as spatial dimensions yields significantly higher capacity. Although this problem is not convex, robust solutions can be obtained by using global optimization techniques such as particle swarm optimization.

Aleksandra Kaszubowska-Anandarajah
Reconfigurable microring resonator-based optical transmitter for elastic optical networks
P. Doddaballapura Lakshmijayasimh1, M. Hammad1, C. Blumm2, A. Moscoso-Martir3, F. Merget3, J. Witzens3 J. van de Belt4, P. M. Anandarajah1, and A. Kaszubowska-Anandarajah4
1School of Electronic Engineering, Dublin City University, Glasnevin, Ireland
2Optical & Quantum Laboratory, Huawei German Research Centre, Munich, Germany
3Integrated Photonics Laboratory, RWTH Aachen University, Germany
4Connect Centre, Trinity College Dublin, Ireland

Increasing data traffic and the shrinking profit margins force network operators to look for intelligent methods of increasing the effective capacity of the transmission systems. This could be achieved through a two-step approach: (1) the introduction of novel transmission techniques, allowing to send more data in the same spectral bandwidth, (2) improving resources utilisation, by dynamically reconfiguring the network to match the current conditions and requirements. Advanced multicarrier transmission techniques such as Nyquist wavelength division multiplexing (NWDM), coherent optical orthogonal frequency division multiplexing (CO-OFDM) or time-frequency packing (TFP) utilise closely spaced multiple channels to increase spectral efficiency and achieve terabit scale transmission. On the other hand, elastic optical networks (EON) aim to maximize the utilisation of the network resources by dynamically adapting the transmission parameters to suit the current network conditions and requirements. In this article we investigate a reconfigurable transmitter based on an optical frequency comb and microring resonators, capable of satisfying vital requirements of both methods (mentioned above) of increasing the capacity of a network. We will demonstrate a high-stability multicarrier optical source for transmission of advanced signals such as NWDM, Co-OFDM etc. In addition, an efficient and simple reconfiguration, allowing to adjust the spectral granularity/channel spacing to fit the traffic requirements, will also be addressed.

Tsuyoshi Konishi
Intensity jitter suppression and quantum fluctuation for resolution improvement in photonic analog-to-digital conversion
T. Konishi and Y. Yamasaki
Osaka University, Osaka, Japan

This talk discusses suppression of intensity jitter due to not only classical but also quantum noises, which is one of serious issues for resolution improvement in photonic analog-to-digital conversion.

Julien Lumeau
Technology of complex optical interference filters: A survey and outlook
J. Lumeau, T. Begou, F. Lemarchand, F. Lemarquis, and A. Moreau
Aix-Marseille Univ., CNRS, Centrale Marseille, Institut Fresnel, Marseille, France
Over the last 15 years, there have been tremendous progress in the technology of optical interference filters. Nowadays, it is more and more common to fabricate optical interference filters that can combine several tens to several hundreds of layers in order to produce more and more complex optical functions. These progresses are the result of improved multilayer structures modeling and design procedures, the introduction of Virtual Deposition Process, and the development of performant physical vapor deposition machines associated with in-situ optical monitoring. In this paper, I will present actual state-of-the-art of these technologies and some typical examples of filters. I will then present some of the actual challenges and outlook in order to produce more and more performant optical components.

Anatole Lupu
Optimal switching operation of PT-symmetric dimmers with nonuniform gain/loss and coupling profiles
A. Lupu1, V. V. Konotop2, and H. Benisty3
1Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Orsay, France
2Centro de Física Teórica e Computacional and Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Portugal
3Laboratoire Charles Fabry de l’Institut d’Optique, CNRS, Univ. Paris Saclay, Palaiseau, France

We assess through a variational optimization approach the optimal gain-loss profile for a non-uniform PT-symmetric coupler allowing the realization of a binary transfer function and minimizing the deviation of the total traveling light intensity as compared to that holding in a conservative system. We bring evidence that the gain-loss profile fulfilling this requirement corresponds to a non-conventional situation when light intensity is conserved in every point along the propagation distance in the PT-symmetric system. Furthermore, the optimal profile thus found corresponds to a practically important case of optical switching operation achieved with a minimal amount of amplification level. We show that switching architectures using such type of gain-loss profiles are very substantially advantageous as compared to conventional uniform PT-symmetric couplers. Furthermore, this type of optimal profile turns out to be robust with respect to fabrication imperfections. This opens new prospects for functional applications of PT-symmetric devices in photonics.

Uri Mahlab
Non-orthogonal multiple access for long-haul elastic optical networks
E. Omiyi, D. Dahan, and U. Mahlab
Holon Institute of Technology (HIT), Israel

We investigate a method of non-orthogonal multiple access (NOMA) as a promising technique to simplify wavelength assignment in long-haul elastic optical networks. The proposed method allows the full overlap of multiple independent and unsynchronised optical signals on the same wavelength, where different signals are coded with a block forward-error-correction (FEC) code and allocated different power levels. The signals are separated using the method of successive-interference-cancellation (SIC) at the receiver. This study focuses on the impact of chromatic dispersion and carrier frequency offset on the optical link performance.

Ilya Polishchuk
Guided modes in periodical arrays of waveguides
A. A. Anastasiev, A. L. Burin, M. I. Gozman, I. Ya. Polishchuk, Yu. I. Polishchuk, and E. A. Tsyvkunova
National Research Nuclear University, MEPhI, Moscow, Russia

We consider a formation of a new kind of guided mode in plane arrays of metallic waveguides. We study arrays made of Ag in order to be able to compare to the results obtained in Ref. [1]. A dispersion law for optical propagating modes is found for different propagation constant β, which is a wave vector component parallel to the waveguide axes. Note that in Ref. [1] the arrays made of Ag are investigated and guided modes for β = 0 are considered. Our analysis reveals that the waveguide array manifests a new kind of guided mode for β ≠ 0. This mode is occurred to cover a part of the visible spectrum and infrared region for ω < β. A behavior of this mode is essentially determined by the propagation constant β. The approach makes use of the multiple-scattering [2], based on the formally exact solution for the electromagnetic wave scattering problem by a separate infinite cylinder wave-guide [3].
[1] S. Belan, S. Vergeles , J. Opt. Soc. Am., 2014.
[2] I. Ya. Polishchuk et al., Phys. Rev. A. 2017, 053847, P 95.
[3] H. C. Van de Hulst, “Light scattering by small particles,” Dover Publications, Inc., New York, 1981.

Quan Pham Van
Monitoring intent for optical channel defragmentation in software-defined elastic optical networks
Q. Pham_Van1, D. Verchere1, P. Layec1, A. Dupas1, F. Ilchmann2, L. Dembeck2, H. Tran-Quang3, and D. Zeghlache3
1Nokia Bell Labs, Nozay, France
2Nokia Bell Labs, Stuttgart, Germany
3Telecom Sud-Paris, Évry, France

As optical networks become more and more elastic to adapt to data traffic demands, knowing the health of the network is of key interest. We propose a monitoring intent framework to facilitate the development of control functions exploiting the monitored optical parameters. We then demonstrate an optical channel defragmentation control function deployed as an SDN application taking advantages of a centralized view of SDN controller to optimize the spectrum utilization.

Danish Rafique
Interplay of pulse shaping and pre-emphasis for high symbol rate coherent transmission systems
D. Rafique, ADVA Optical Networking SE, Munich, Germany
Digital pre-emphasis (DPE) in optical communications has been proposed to counteract transceiver bandwidth limitations, enabling higher symbol rate transmission with low bandwidth opto-electronic components. However, system design trade-offs for diverse regimes of weak and strong pre-emphasis largely remain unexplored.  In this paper, we model 32Gbaud commercial transceivers’ component behaviour to enable DPE-aided 64Gbaud operation, as opposed to high bandwidth components’ utilization. We systematically investigate the interplay of DPE parameters for multi-component pre-emphasis, and its impact on available transmitter output power and transmission performance. In particular, we consider 64Gbaud dual polarization quadrature amplitude modulation (DP-x-QAM), x = 4, 16, 64, enabling 200Gb/s, 400Gb/s and 600Gb/s line rates, and show that DPE may offer performance gains of up to ~4.6dB, compared to no DPE, however with an associated output power loss of up to ~9dB. Furthermore, we report that at -16dBm target optical output power, DP-QPSK shows highest net performance loss, compared to maximal performance, followed by DP-16QAM and DP-64QAM.

André Richter
Rotationally-invariant multi-dimensional trellis coded modulation for optical transmission systems
S. Alreesh, S. Dris, and A. Richter
VPIphotonics GmbH, Berlin, Germany
We review the principle of multidimensional (multi-D) trellis coded modulation (TCM). We describe the structure of multi-D TCM schemes and discuss their main advantages. Numerical simulations show that multi-D TCM combined with simple hard-decision forward error correction (HD-FEC) codes are of practical interest, as they can provide a better trade-off between complexity and performance, compared to soft-decision (SD-)FEC alternatives. Moreover, the scheme is resilient to cycle-slip events due to its 90° phase rotation-invariant property.

Henrique Salgado
Experimental evaluation of resonant tunnelling diode oscillators employing advanced modulation formats
J.S. Tavares, L.M. Pessoa, and H. M. Salgado
Centre for Telecommunications and Multimedia, INESC Porto, Faculdade de Engenharia, Universidade do Porto, Portugal
In this work we experimentally evaluate and compare the performance of Resonant Tunnelling Diode (RTD) Oscillators with an optical window when transmitting modulated signals using advanced modulation formats.

François Sanchez
New mechanism of generation of high energy pulses from passively mode-locked fiber laser
F. Ben Braham1,2, G. Semaan1, A. Niang1, M. Salhi1, A. Komarov3, K. Komarov3, and F. Sanchez1
1Laboratoire de Photonique d’Angers, Université d’Angers, France
2Laboratoire Systèmes Électroniques et Réseaux de Communications (SERCOM), Ecole Polytechnique de Tunisie, Université de Carthage, Tunisia
3Institute of Automation and Electrometry, Russian Academy of Sciences, Novosibirsk, Russia
We demonstrate the possibility to generate wave breaking free optical pulses from a new design of passively mode-locked fiber laser. We have successfully obtained high energetic pulses in the microsecond range without wave breaking for any available pumping power. Our experimental results open a new way for energy scaling in passively mode-locked fiber lasers.

Michela Svaluto Moreolo
Optical technology options for programmable S-BVT
M. Svaluto Moreolo, J. M. Fàbrega, L. Nadal, and L. Martín
Centre Tecnològic de Telecomunicacions de Catalunya, Barcelona, Spain

Optical technology options for programmable sliceable bandwidth-variable transceivers (S-BVT) will be presented in this talk, reviewing our proposals based on adaptive multicarrier modulation. Special attention will be devoted to data plane solutions with high degree of (re)configurability and flexibility for the optical metro network segment. Transceiver architectures based on modular design will be proposed to target grow-as-needed approach and optical domain disaggregation, identifying data plane elements that can be considered as separate management and functional entities, as well as functionalities that can be moved to software. Our work in this direction will be presented focusing on the S-BVT features, functional identification and capabilities, taken into account the optical system and its interrelationship with other elements of the network.

Jarosław Turkiewicz
Out of the 1550 nm window transmission
J.P. Turkiewicz , Institute of Telecommunications, Faculty of Electronics and Information Technology, Warsaw University of Technology, Warsaw, Poland
For years the majority of the telecommunication traffic have been transmitted in the 1550 nm window. That resulted from the minimum attenuation (0.2 dB/km) as well as the superior 1550 nm amplification technology (EDFA/Raman). Recently, new application areas of for the optical fibre transmission have emerged, which can be successfully by supported by other transmission windows. The paper presents analysis of the 850 nm and 1310 nm windows and their applicability to the selected optical transmission applications in particular to the short and medium haul data interconnects.

Ricard Vilalta
Zero-touch network slicing through multi-domain transport networks
R. Vilalta, P. Alemany, R. Casellas, R. Martínez, C. Parada, J. Bonnet, F. Vicens, and R. Muñoz
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Castelldefels, Spain

The concept of network slicing is gaining a lot of interest and being under notable discussion within SDOs such as 3GPP, ETSI and IETF. A Network Slice is a set of network functions, and the resources to run these network functions, forming a complete instantiated logical network, which meets certain network characteristics. In this paper, we provide an overview of operationalization and deployment of the different data and control plane technologies used for both Network Slicing and Network Virtualization, which are two key enablers of future 5G networks.

Naoya Wada
High-frame-rate single-shot spectrum measurement for ultrafast optical pulses based on optical signal processing
N. Wada, H. Furukawa, and J. M. Delgado Mendinueta
National Institute of Information and Communications Technology (NICT), Tokyo, Japan

The pulse-by-pulse single-shot spectrum measurement for high-repetition rate optical pulses with femtosecond or picosecond pulse width is important for capturing non-repetitive and rare phenomena of substances. Conventional optical spectrum analyzers cannot acquire the spectrum for each pulse at high-repetition rate without missing due to the low processing speed. Several high-speed optical signal processing techniques can help to acquire pulse-by-pulse single-shot spectrum. The high-speed spectrum measurement using a fiber chromatic dispersion-based time stretch dispersive Fourier Transform (TS-DFT) technique is a powerful tool for such measurements. In this paper, we present a record pulse-by-pulse single-shot spectrum measurement for 1 GHz repetition-rate optical pulses with a less than 67-pm spectral resolution based on the TS-DFT technique.

Cédric Ware
Network-level strategies for best use of optical functionalities
C. Ware, Institut Mines-Télécom, Télécom ParisTech, CNRS LTCI, Paris, France
Optical functionalities, such as optical packet switching and wavelength conversion, have had little use in practice despite their potential benefits to data networks by lifting performance bottlenecks and curbing energy consumption. Enabling them requires network-level handling strategies to exploit their full capability in ways that are compatible with network paradigms. We explore such strategies, and quantify some of their benefits at the network level.

Guang Wu
Recent progresses in Chinese telecom and photonic
Shaomin Yan and Guang Wu
Great progresses have been made over past decades on photonics, optical networks as well as telecommunications in China. In this mini-review, recent progresses are presented from academic settings and industrial sectors with respect to research, economic development, global positioning, etc. Attention is also given to the current policies on the development of optical network in China.

Xu Wang
40 Gb/s secure optical communication system based on optical code technology
Xu Wang1, Zhensen Gao2, Bo Dai2, and G. Buller1
1The Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK
2Engineering Research Center of Optical Instrument and System, the Ministry of Education, Shanghai Key Lab. of Modern Optical System, University of Shanghai for Science and Technology, China
Various approaches for secure optical communication have been proposed over the past years, such as quantum key distribution, chaotic communication and optical code (OC) based secure communication. In this paper, we review the advances of spectral phase encoding (SPE) optical code technology based for 40 Gb/s OOK and DPSK secure optical communication systems.

Xu Wang
Anti-aliasing and data compressing techniques for time-stretch imaging system
Xu Wang1 and Bo Dai2
1The Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK
2Engineering Research Center of Optical Instrument and System, the Ministry of Education, Shanghai Key Lab. of Modern Optical System, University of Shanghai for Science and Technology, China
Time-stretch imaging is a novel ultrafast imaging technique based on space-to-time-to-wavelength mapping. Optical time-division multiplexing technique can used in this system for anti-aliasing and improve the imaging quality with low bandwidth electronics. With this TDM based anti-aliasing technique, we can acquire a large amount of image information by using relatively low-sampling-rate electronic digitizer. Numerical analysis shows that the image quality can be improved by 4.16 dB comparing to that without using the anti-aliasing technique and at least 2.3 dB comparing to those digital signal processing techniques such as bilinear, bicubic and nearest-neighbour interpolation and Lanczos resampling techniques. Experimental demonstration of line-scan imaging system, which has the scan rate of 38.88 MHz is carried out. Defects and scratches on the object that were not identifiable originally can be clearly distinguished after using the TDM based  anti-aliasing technique.

Moshe Zukerman
Comparison of different multicast approaches in elastic optical networks
Anliang Cai, Kai Xu, and M. Zukerman
City University of Hong Kong, China

Significant research efforts have been directed in recent years towards the development of elastic optical networks (EONs) to improve the efficiency of future networks beyond current WDM networks. In addition, multicast services, including live internet video delivery and inter-datacenter database synchronization, are gaining popularity, and usually generate large volume traffic. We focus on routing and spectrum allocation for the multicast traffic in EONs considering distance-adaptive transmission. Existing studies focus on using light-tree and lightpath solutions for provision of multicast services in optical network (both WDM and EONs), while there were very few publications on using light-trail in EONs. In particular, since the light-tree and the light-trail inherently support optical multicasting, a multicast service can be provisioned either by a single light-tree/light-trail or by multiple light-trees/light-trails, while for the lightpath technology, a lightpath is utilized for each multicast destination. In this paper, we compare the effectiveness, in term of spectrum and transmitter usage, of light tree, lightpath and light trail approaches in provisioning of multicast services. We also evaluate, in EONs, the benefit of having distance-adaptive transmission for these schemes. Numerical results based on MILP illustrate their performances for a range of cases.

5GT invited presentations:

Adrian Farrel
Recent developments in service function chaining (SFC) and network slicing in backhaul and metro networks in support of 5G
A. Farrel, Old Dog Consulting, UK
I would focus on three strands: – latest work on these technologies at the IETF, – progress on the application of network slicing to the metro network as exposed by the H2020 Metro-Haul project, ­ thought leadership from Old Dog Consulting.

Nathan Gomes
Optical fronthaul options for meeting 5G requirements
N. J. Gomes and P. Assimakopoulos
Communications Research Group, University of Kent, Canterbury, UK

New functional splits for the 5G Radio Access Network have been identified so that fronthaul will no longer need to transport sampled time-domain waveforms. However, the different functional split points place differing demands on the fronthaul transport, while also posing different constraints to 5G techniques, such as massive MIMO. According to these conflicting demands, it is likely that in many cases, more than one split point may be needed in the same radio access network.

Lei Guo
Planning of resilient OFDM-PON in support of 5G backhaul
Yejun Liu and Lei Guo
School of Computer Science and Engineering, Northeastern University, Shenyang, China

Orthogonal Frequency Division Multiplexing Passive Optical Network (OFDM-PON) has been regarded as one of the promising solutions for 5G backhaul due to its excellence in spectral efficiency and transmission stability. However, the vulnerability of OFDM-PON to link failure cumbers its applicability in 5G backhaul, which is expected to offer enhanced network resilience. Although link duplication has evolved as a common practice for the protection of PON against link failure, the compromise between expenditure for backup link and QoS guarantee remains an open issue. In this paper, we focus on the cross-layer network planning of resilient OFDM-PON and propose an ingenious subcarrier exchange mechanism to effectively mediate between network deployment expenditure and QoS degradation at both PHY and MAC layers. On basis of the subcarrier exchange mechanism, we derive an optimal subcarriers allocation and backup fiber deployment mathematically using integral linear programming.

Roberto Sabella
Photonic systems and devices for 5G
R. Sabella1 and L. Potì2
1Ericsson Research, Pisa, Italy
2PNTLab, CNIT, Pisa, Italy

5G requirements and opportunities strongly benefit for and influence the development of new photonic devices with increased functional complexity at a reduced cost. At the same time, innovative system techniques contribute to support the fast evolution of network segments over different geographical scales driven by new concepts and applications needed in a connected world. The paper will address key aspects, constraints, limitations and perspectives in a single mindful vision.

Salvatore Spadaro
End-to-end 5G service deployment and orchestration in optical networks with QoE guarantees
R. Montero, F. Agraz, A. Pagès, and S. Spadaro
Universitat Politècnica de Catalunya, Barcelona, Spain

The upcoming 5G deployments will impose stringent requirements. Optical networks control and resource orchestration is set to potentially turn into software-defined approaches in order to address such requirements. As a result, there rises a need for an architectural scheme capable of supporting the different types of services defined for 5G verticals. We present in this paper an architecture enabling end-to-end (E2E) provisioning and monitoring of such 5G services over optical network segments. In particular, the scenario considers the coordination of various optical enabled network segments by a higher level E2E Orchestrator, which provides of network slice deployment and is able to guarantee agreed levels of Quality of Experience (QoE). Moreover, we discuss an example of 5G service provisioning using the proposed architecture to demonstrate its behaviour in front of different network events.

Idelfonso Tafur Monroy
Testing facilities for end-to-end test of vertical applications enabled by 5G networks: Eindhoven 5G Brainport testbed
I. Tafur Monroy1, T. R. Raddo1, S. Rommel1, C. Okonkwo1, N. Calabretta1, U. Johannsen2, G. Dubbelman2, J. Scholtes2, and B. Rutten2
1Institute for Photonic Integration, Eindhoven University of Technology, the Netherlands
2Eindhoven University of Technology,  the Netherlands

The key-performance indicators (KPIs) that will be delivered by 5G networks such as extremely low-latency, high capacity, robustness and highly flexible network are key enablers for applications such as autonomous driving, cooperative robotics, transport and processing of large volumes of video and images, to name but a few. This paper presents the ongoing build up and deployment of the Eindhoven based 5G-Brainport testbed towards an open environment for validation and test of end-to-end applications benefitting from the 5G KPIs.

Luca Valcarenghi
Encapsulation techniques and traffic characterisation of an Ethernet-based 5G fronthaul
F. Civerchia1, K. Kondepu1, F. Giannone1, S. Doddikrinda2, P. Castoldi1, and L. Valcarenghi1
1Scuola Superiore Sant'Anna, Pisa, Italy
2Università degli Studi dell’Aquila, Italy
This paper first overviews how in the 5G New
Radio Access Network (New RAN) the Next generation NodeB (gNB) functions are split into Radio Unit (RU), Distributed Unit (DU), and Central Unit (CU). Then it overviews the proposed fronthaul transport solutions, such as Common Packet Radio Interface (CPRI), eCPRI, IEEE P1914.3 and their relationship with the Ethernet protocol. Finally a characterisation of the traffic generated by the fronthaul is presented. Such characterisation may guide in the selection of the right network for fronthaul transport.


ACCESS invited presentations:

Marcelo Abbade
A new DSP-based physical layer encryption technique applied to passive optical networks
M. L. F. Abbade, L. Silva Lessa, M. de Oliveira Santos, A. J. do Prado, and I. Aldaya
State University of São Paulo, Campinas, Brazil
Point-to-multipoint architecture poses serious security problems to passive optical networks (PONs). In this paper, we propose the use of a new digital signal processing (DSP)-based technique to improve the confidentiality of signals traveling through PONs. The technique consists of phase-shifting and delaying the spectral components of baseband signals that further modulate optical carriers. Our simulation analysis encompasses the application of the technique to binary phase-shift keying (BPSK) and to quadrature phase-shift keying (QPSK) signals in an intensity modulated-direct detection (IM-DD) system. Results reveal that the encrypted signals may be properly decoded even under a high-loss regime.

Ivan Cano
Direct phase modulation for UDWDM ONU with beat signals
J. C. Velásquez, I. N. Cano, J. Tabares, V. Polo, and J. Prat
Universitat Politècnica de Catalunya, Barcelona, Spain
An ONU transmitter for UDWDM PONs based on direct phase modulated distributed feedback lasers (DFB) through digital beat signals is proposed and experimentally tested. The amplitude and duty cycle of the modulating signal are optimized for a DPKS signal. We achieved sensitivities of -50.5 dBm, and -45 dBm for bit rates of 2.5 Gb/s, and 5 Gb/s respectively at BER = 4×10-3 with an intradyne coherent receiver.

Roberto Gaudino
Towards 50 Gb/s in high-speed PON: Optimization of modulation formats using pre-chirping
P. Torres-Ferrera, H. Wang, V. Ferrero, R. Mercinelli, and R. Gaudino
Politecnico di Torino, Dipartimento di Elettronica, Torino, Italy
High-Speed (HS) Passive Optical Network (PON) alternatives with single-wavelength capacity higher than 10 Gb/s, such as 25 and 50 Gb/s, are currently under investigation, development and standardization in IEEE and ITU-T. Modulation formats based on intensity modulation and direct detection (IM-DD) are still preferred to implement next generation HS-PON due to their advantages in terms of complexity and costs compared to coherent solutions. Among IM-DD solutions, conventional Non-Return-to-Zero (NRZ) format, as well as four-level Pulse Amplitude Modulation (PAM-4) and Electrical Duo-Binary (EDB), have emerged as the most promising ones. In previous works, our group has shown that none of these formats is anyway feasible for the transmission of 50 Gb/s using currently available 25 Gb/s NRZ transceiver technology when operating in C-band (i.e. around 1550 nm) in single mode fibre (SMF) for typical PON distances (i.e., 20 km), while NRZ is not feasible even in the O-band (i.e. around 1300 nm). In this contribution, we introduce the use of pre-chirping technique in order to overcome this reach limitation. By means of simulations, we compare the achievable performance of NRZ, PAM-4 and EDB under demanding band-limited and dispersive conditions on the transmission of 50 Gb/s using adaptive equalization at the receiver, with and without pre-chirping. We investigate on the feasibility of the transmission of 50 Gb/s through 20-km of SMF using NRZ in O- and PAM-4 in C-band, showing that the target can be reached only when pre-chirping is employed.

Hamid Hemmati
Backhaul communications at 10’s of Gbps data-rate
H. Hemmati, Sr. Director of Engineering for Telecom Infrastructure Facebook Inc.
Nearly 3.8 billion of the world’s population are either unconnected or have poor access to the Internet. The cumulative data-rate to provide Internet access to this population is at 100’s of Tbps. Cost effective technology advancements at a variety of communications bands and for various telecom scenarios is required.

Carmen Mas Machuca
XGPON statistical multiplexing analysis with heterogeneous users
A. Gupta, A. Dixit, and C. Mas Machuca
Technische Universität München, Germany
Optical access networks are evolving mainly driven by the higher bandwidth requirements. XGPON is one of the most cost effective solution to upgrade existing GPON since it reuses existing Optical Distribution Networks. However, in order to increase the cost savings, these networks are planned to connect heterogeneous types of users such as base stations, residential or business users. Statistical multiplexing of XGPON allows assigning different bandwidth to the different users based on their demands and always guaranteeing the agreed Service Level Agreements. This work aims at evaluating the impact to packet delay and throughput of different XGPON scenarios for different user distributions. Furthermore, the paper evaluates the flexibility to cope with extra traffic caused by existing protection schemes.

Josep Segarra
Flexible mobile fronthaul with coherent UDWDM-PON
J. Segarra, V. Sales, and J. Prat
Universitat Politècnica de Catalunya, UPC, Barcelona, Spain
Ultra-Dense Wavelength Division Multiplexing (UDWDM) has been proposed for future Passive Optical Networks (PONs) to support the increase of access traffic, furnishing an improved capacity while introducing point-to-point logical connections with the Wavelength-To-The-User (WTTU) concept, enabled by low cost coherent transceivers with high sensitivity. Furthermore, considering wireless networks, a centralized processing in a Cloud-Radio Access Network (C-RAN) needs reconfigurable abilities to bring benefits to mobile systems with dynamic demands of huge bandwidth between Remote Radio Heads (RRHs) at base stations and Baseband Units (BBUs) at the central office. To achieve this goal in the access network, we propose a flexible architecture design of an UDWDM-PON, which adapts the available bandwidth to different users and classes of services and can reconfigure the connections between RRHs and BBUs.

Massimo Tornatore
Filterless and semi-filterless solutions in a Metro-HAUL network architecture
O. Ayoub, S. Shehata, F. Musumeci, and M. Tornatore
Department of Electronics, Information and Bioengineering, Politecnico di Milano, Italy

Filterless optical networks based on broadcast-and-select nodes have been proven to be a cost-effective alternative to active photonic network solutions in core networks. However, due to the emergence of novel metro-based high-bandwidth cloud-based services (e.g., Virtual Reality, 4K Video-on-Demand, etc.), filterless solutions have started to attract research attention also in the metro area. In this paper, we evaluate the performance of fully-filterless and semi-filterless (i.e., hybrid solutions between fully-filterless and active photonic architectures) optical-network architectures in terms of cost of network elements and spectrum utilization, in a metro-network scenario. Our evaluations show that, due to the ring-based hierarchical nature of metro networks, fully-filterless architectures tend to require excessive spectrum utilization as the broadcast effect spreads among all hierarchical rings. On the contrary, semi-filterless network architectures seem more promising due to the presence of filters that fend off the propagation of unfiltered channels. The results also show that it is more advantageous to deploy filters at nodes of the lower network levels than at nodes of higher network levels.

Elaine Wong
Supporting low-latency applications through hybrid cost-optimised cloudlet placement
S. Mondal, G. Das, and E. Wong
University of Melbourne, Australia

Low-latency applications such as augmented reality, cognitive assistance, and context-aware computation are better supported by augmenting cloud networks with cloudlet enabled edge computing solution. This overcomes the high-transmission latency arising from the edge devices in the access segment to cloud servers located in the core. In this talk we review our proposed hybrid cost-optimization framework for optimal cloudlet placement over existing passive optical access networks, subject to capacity and latency constraints. We formulate a mixed-integer non-linear program to identify ideal locations (either at the central office, remote node, or in the field) for cloudlet placement over three areas of differing population densities. Our results point to the fact that the installation of more RN and CO-located cloudlets will yield an improved cost optimal solution than the installation of field cloudlets alone, and that the percentage of the incremental energy budget arising from the installation of cloudlets are low.


BigNeO invited presentations:

Josep Lluis Berral
When and how to apply statistics, machine learning and deep learning techniques
J. L. Berral, Barcelona Supercomputing Center, Spain
Machine Learning has become 'commodity' in engineering and experimental sciences, as did calculus and statistics before. After the hype produced during the 00's, machine learning (statistical learning, neural networks, etc.) has become a solid and reliable set of techniques available to the general researcher population to be included in their common procedures, far from the mysticism surrounding this field when only ML experts could solve modeling and prediction problems using such novel algorithms. But while knowledge on this field has settled among professionals, novice ML users still have trouble to decide when determined techniques could and should be applied to solve a given problem, sometimes ending with over-complicated solutions for simplistic problems, or complex problems partially solved by simplistic methods. This tutorial wants to introduce the most common techniques on statistical learning and neural networks, next to use cases where such techniques can be applied, looking towards showing the proper techniques for each given scenario.

Fabien Boitier
Automated optical networks with monitoring and machine learning
F. Boitier and P. Layec
Nokia Bell Labs Paris-Saclay, Nozay, France
We briefly review monitoring techniques for coherent optical networks. We leverage the collected information with machine learning and show how optical networks can benefit from such techniques. We review how the optical network could be automated with learning techniques based on different use cases and associated architectures, ranging from low latency to high cognition requirements.

Ramon Casellas
Enabling data analytics and machine learning for 5G services within disaggregated multi-layer transport networks
R. Casellas, R. Martínez, L. Velasco, R. Vilalta, P. Pavón, D. King, and R. Muñoz
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels (Barcelona), Spain
Recent advances, related to the concepts of Artificial Intelligence (AI) and Machine Learning (ML) and with applications across multiple technology domains, have gathered significant attention due, in particular, to the overall performance improvement of such automated systems when compared to methods relying on human operation. Consequently, using AI/ML for managing, operating and optimizing transport networks is increasingly seen as a potential opportunity targeting, notably, large and complex environments. Such AI-assisted automated network operation is expected to facilitate innovation in multiple aspects related to the control and management of future optical networks, and is a promising milestone in the evolution towards autonomous networks, where networks self-adjust parameters such as transceiver configuration.

Ramón Durán
Genetic algorithm for effective service mapping in the optical backhaul of 5G networks
L. Ruiz1, R. J. Durán1, I. de Miguel1, P. S. Khodashenas2, J. J. Pedreno-Manresa3, N. Merayo1, J. C. Aguado1, P. Pavon-Marino3, S. Siddiqui2, J. Mata1, P. Fernández1, R. M. Lorenzo1, and E. J. Abril1
1Optical Communications Group, Universidad de Valladolid, Spain
2i2CAT Foundation, Barcelona, Spain
3Universidad Politécnica de Cartagena, Spain
A genetic algorithm is proposed to map virtual network functions in computing resources over 5G networks with optical backhauling system. The algorithm outperforms other proposals in terms of blocking ratio and active CPU cores utilization.

Paolo Festa
Performance evaluation of the VNT reconfiguration algorithm based on traffic prediction
F. Morales1, P. Festa2, M. Ruiz1, and L. Velasco1
1Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
2Dipartimento di Matematica e Applicazioni “R. Caccioppoli”, Università degli Studi di Napoli Federico II (UNINA), Napoli, Italy

In a previous work, the Virtual Network Topology Reconfiguration problem based on Traffic Prediction (VENTURE) was proposed as a means of efficiently adapting core virtual network topology (VNT) to the near-future traffic. Although the benefits obtained by the VENTURE algorithm compared to using a purely reactive VNT reconfiguration approach seems to be clear, margin for improvement still remain and alternative solving methods for the VENTURE problem need to be considered. In this paper, the original VENTURE algorithm is compared against two state-of-the-art metaheuristics for combinatorial network optimization. The two metaheuristics are first presented and then adapted for the VENTURE problem. Finally, the performance of the VENTURE algorithm and the two proposed metaheuristics is numerically evaluated using an exact solving method as reference.

Lluís Gifre
CASTOR: A monitoring and data analytics architecture to support autonomic domain and slice networking
L. Gifre1, M. Ruiz2, and L. Velasco2
1Universidad Autónoma de Madrid (UAM), Madrid, Spain
2Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Network slices combine resource virtualization with the isolation level required by future 5G applications. In addition, the use of Monitoring and Data Analytics (MDA) helps to maintain the required network performance, while reducing total cost of ownership. In this paper, we present CASTOR, an architecture to enable autonomic domain and slice networking. MDA agents use data analytics to make local decisions close to network devices, whereas MDA controllers collate and export metered data transparently to customer controllers, all of them leveraging customizable and isolated data analytics processes. Discovered knowledge can be applied for both proactive and reactive network slice reconfiguration, triggered either by service providers or customers, thanks to the interaction with state-of-the-art software-defined networking controllers and planning tools.

Jose-Luis Izquierdo-Zaragoza
Optimization-as-a-service for traffic-engineering SDN applications
J.-L. Izquierdo-Zaragoza and L. Velasco
Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
The evolution of SDN controllers into network operating systems is risking their role as one-stop shops for basic network services, beyond consolidation of control planes from multiple devices into a single entity, i.e., for path computation. An illustrative example of killing application is intent-based provisioning. Here, business logic is based on the definition of service requests including endpoints as well as other constraints like bandwidth or QoS requirements, then leveraging the SDN controller for allocation, generally based on shortest path provisioning. In order to apply smarter network allocation algorithms as well as more sophisticated like service reallocation, integration with external PCEs is mandatory. In this paper, we present a framework for integration between SDN controllers and planning tools opening the door not only to applications like smarter intent-based provisioning but also in-operation network planning and reconfiguration, thanks to the integration with monitoring and data analytics platforms. A use case based in multilayer service provisioning and operation is presented to validate our framework.

Brigitte Jaumard
Make-before-break wavelength defragmentation
B. Jaumard1, H. Pouya1, and D. Coudert2
1CSE, Concordia University, Montreal, Canada
2Université Côte d'Azur, Inria, CNRS, I3S, UNS, Sophia Antipolis, France

Future optical networks, in particular Software Defined Optical Networks (SDONs), are expected to provide reconfigurable services while maintaining an efficient usage of wavelength resources. In this paper, we propose a Make-Before-Break (MBB) wavelength defragmentation process which minimizes the bandwidth requirement of the resulting provisioning. We next compare the latter provisioning with a minimum bandwidth provisioning that is not subject to MBB.  The resulting solution process is thoroughly tested on various data and network instances. Numerical experiments show that, on average, the best seamless lightpath rerouting is never more than 5% away (less than 1% on average) from an optimal lightpath provisioning.

Guido Maier
Deep learning-based traffic prediction for network optimization
S. Troia, R. Alvizu, Y. Zhou, G. Maier, and A. Pattavina
Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Italy

In recent years, researchers realized that the analysis of traffic datasets can reveal valuable information for the management of mobile and metro-core networks. That is getting more and more true with the increase in the use of social media and Internet applications on mobile devices. In this work, we focus on deep learning methods to make prediction of traffic matrices that allow us to proactively optimize the resource allocations of optical backbone networks. Recurrent Neural Networks (RNNs) are designed for sequence prediction problems and they achieved great results in the past years in tasks like speech recognition, handwriting recognition and prediction of time series data. We investigated a particular type of RNN, the Gated Recurrent Units (GRU), able to achieve great accuracy (<7.4 of mean absolute error). Then, we used the predictions to dynamically and proactively allocate the resources of an optical network. Comparing numerical results of static vs. dynamic allocation based on predictions, we can estimate a saving of 66.3% of the available capacity in the network, managing unexpected traffic peaks.

Rui Morais
Evaluating machine learning models for QoT estimation
R. M. Morais1,2 and J. Pedro1,3
1Coriant, Amadora, Portugal
2Instituto de Telecomunicações, Aveiro, Portugal
3Instituto Superior Técnico, Instituto de Telecomunicações, Lisboa, Portugal
This work evaluates the effectiveness of various machine learning (ML) models when used to predict the Quality of Transmission (QoT) of an unestablished lightpath, speeding up the process of lightpath provisioning. Three network scenarios to efficiently generate the knowledge database used to train the models are proposed as well as an overview of the most used ML models. The considered models are: K nearest neighbors (KNN), logistic regression, support vector machines (SVM), and artificial neural networks (ANN). Results show that, in general, all ML models are able to correctly predict the QoT of more than 95% of the lightpaths. However, ANN is the model presenting better generalization, correctly predicting the QoT of up to 99.9% of the lightpaths.

Antonio Napoli
Maximizing the capacity of installed optical fiber infrastructure via wideband transmission
J. K. Fischer1, M. Cantono2, V. Curri2, R.-P. Braun3, N. Costa4, J. Pedro4, E. Pincemin5, P. Doaré6, C Le Boüetté7, and A. Napoli8
1Fraunhofer Institute for Telecommunications Heinrich-Hertz-Institute, Berlin, Germany
2Politecnico di Torino, Torino, Italy
3Deutsche Telekom AG, Germany
4Coriant Portugal, Amadora, Portugal
5Orange Labs, Lannion, France
6Keopsys, Lannion, France
7Ekinops, Lannion, France
8Coriant R&D GmbH, Munich, Germany
Optical wideband communication systems aim at transmitting over several, if not all, of the low-loss windows of single-mode fibre, i.e. the O-, E-, S-, C-, and L-band. Recently, there has been a clear trend in the industry to support additional bands beyond C-band. While C+L-band solutions are close to commercialization and first products are emerging, the research focus is shifting to supporting also the S-band and, finally, the whole O- to L-band (resulting in a total transmission bandwidth of 365 nm). This contribution highlights the perspectives of wideband communication systems for optical networks, providing a realistic roadmap for their deployment. Particular emphasis is paid on a first analysis to estimate the maximum transmittable capacity over these systems.

Pablo Pavon-Marino
Net2Plan-GIS: An open-source Net2Plan extension integrating GIS data for 5G network planning
J.L. Romero-Gazquez1, M.V. Bueno-Delgado1,2, F.J. Moreno-Muro1, and P. Pavon-Marino1,2
1Universidad Politécnica de Cartagena, Spain
2E-lighthouse Network Solutions, Cartagena, Spain
In this paper, we present Net2Plan-GIS: an open-source extension of the Net2Plan network planning tool. Net2Plan-GIS permits importing data from Geographical Information Systems (GIS) databases, making them available for network optimization. A use case is presented making use of the GIS data in the city of Cartagena (Spain). User traffic demands and potential antenna locations are estimated from the city layouts. They feed a tentative dimensioning of a 5G backhaul segment.

Carla Raffaelli
Distributed location algorithms for flexible BBU hotel placement in C-RAN
C. Raffaelli, B. M. Khorsandi, and F. Tonini
University of Bologna, Italy
Distributed location algorithms, as a practical approach to optimally locate virtual functionalities in C-RAN, are presented and compared to conventional optimization techniques, with application to BBU Hotel placement and dynamic evolution of C-RAN configuration.

Danish Rafique
Machine learning based optimal modulation format prediction for physical layer network planning
D. Rafique, ADVA Optical Networking SE, Munich, Germany
Physical layer network design and planning process is a cumbersome one. It includes laying out all possible combinations of modulation formats, fiber types, forward error correction codes, channel spacing, etc., conducting exhaustive simulations and lab experiments to come up with carefully tuned engineering rules, and finally using these approximate models to propose transmission feasibility. Besides being cumbersome, there are two fundamental issues in conventional network planning approach, firstly it almost exclusively offers conservative design, leading to resource underutilization, and secondly it’s not scalable – neither from planning viewpoint nor computationally – to next-generation highly granular and flexible networks. Machine learning, an artificial intelligence toolset, may be applied to solve aforementioned issues by allowing data-driven model development, and consequent transmission quality prediction. While network planning is an extensive topic, in this paper, we focus on neural network based modulation format classification, autonomously identifying best possible modulation format for a given link configuration.

Marc Ruiz
Soft failure localization in elastic optical networks
A.P. Vela, B. Shariati, M. Ruiz, J. Comellas, and L. Velasco
Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Soft failure localization to early detect service level agreement violations is of paramount importance in elastic optical networks (EONs), while it allows anticipating possible hard failure events. Nowadays, effective and automated solutions for soft failure localization during lightpaths’ commissioning testing and operation are still missing. In this paper, we focus on presenting soft failure localization algorithms based on two different active monitoring techniques. First, the Testing optical Switching at connection SetUp timE (TISSUE) algorithm is proposed to localize soft failures during commissioning testing phase by elaborating the estimated bit-error rate (BER) values provided by low-cost optical testing channel (OTC) modules. Second, the FailurE causE Localization for optical NetworkinG (FEELING) algorithm is proposed to localize failures during lightpath operation using cost-effective optical spectrum analyzers (OSAs) widely deployed in network nodes. Results are presented to validate both algorithms in the event of several soft failures affecting lasers and filters.

Behnam Shariati
Spectrally and spatially flexible optical networks: Recent developments and findings
B. Shariati1, D. Klonidis2, J. Comellas1, L. Velasco1, and I. Tomkos2
1Universitat Politècnica de Catalunya (UPC), Barcelona, Catalonia, Spain
2Athens Information Technology (AIT), Marousi, Greece
Space division multiplexing (SDM) has been proposed as the ultimate solution to address the capacity crunch of optical transport networks. The efficient utilization of SDM requires some forms of spatial integration which is expected to bring huge cost savings for the deployment of SDM-based optical networks. Spatially integrated components with different characteristics have been largely explored and demonstrated for the realization of SDM networks, including; transmission media, transceivers with sophisticated digital signal processing (DSP) units, amplifiers, and ultimately optical switching nodes which are the key elements for the realization of transparent optical networks exploiting SDM technologies. As a consequence, in contrast to the currently deployed optical networks based on standard single mode fibers (SSMF), the next generation of optical networks exploiting SDM technologies can be realized utilizing various kinds of transmission media and the other corresponding elements. However, due in part to the physical properties of different components, their complexity, and the technology limitations not all of them meet the economic feasibility and a desired level of network-wide performance. Therefore, careful analysis should be done revealing the most appropriate and cost-effective solutions. In this work, we review the recent developments and findings which pave the way for a simplified and efficient implementation of the spectrally and spatially flexible optical networks.

Alba Vela
Examples of machine learning algorithms for optical network control and management
A. P. Vela, Marc Ruiz, and Luis Velasco
UPC, Barcelona, Spain
Machine learning offers a variety of algorithms in order to assist us in making decisions with big datasets. In particular, for optical networks, the use of machine learning algorithms might be applied for prediction and to detect patterns, among others. Those predictions and pattern discovery can help to understand the behaviour of optical connections and facilitate improving the performance of the network. In this paper, we will review main supervised and unsupervised machine learning algorithms including linear regression, support vector machines, Bayesian networks, and k-means. Illustrative examples of the reviewed algorithms applied to optical networks will be presented.

Luis Velasco
Anticipating BER degradation in optical networks
A. P. Vela, M. Ruiz, and L. Velasco
Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
Optical connections support virtual links in MPLS-over-optical multilayer networks and therefore, errors in the optical layer impact on the quality of the services deployed on such networks. Monitoring the performance of the physical layer allows verifying the proper operation of optical connections, as well as detecting bit error rate (BER) degradations. Anticipating BER degradation facilitates self-decision making to keep committed service level. In this paper, we analyze several failure causes affecting the quality of optical connections and propose the BANDO algorithm focused on detecting significant BER changes in optical connections. BANDO runs inside the network nodes to accelerate degradation detection and sends a notification to the centralized controller. Results show significant improvement anticipating maximum BER violation.

Mateusz Żotkiewicz
Optimizing backup fibers in passive optical networks
M. Żotkiewicz, Institute of Telecommunications, Warsaw University of Technology, Warsaw, Poland
We consider a problem of optimizing a number of backup fibers in passive optical networks (PON). We assume that trenching costs successfully discourage operators from deploying alternative routes for the majority of their non-critical clients; thus, these clients are protected only from partial cable cuts thanks to backup fibers in affected cables. We discuss the problem of dimensioning the number of these backup fibers having in mind expenses, on the one hand, and resiliency, on the other hand.

CTS invited presentations:

Silvio Abrate
Remotized control of power electronic devices exploiting a plastic optical fiber photonic bus
A. Varatharajan1, P. Savio2, E. Vizzaccaro3, S. Abrate2, G. Pellegrino2, and V. Curri3
1DENERG, Politecnico di Torino, Italy
2Istituto Superiore Mario Boella, Torino, Italy
3DET, Politecnico di Torino, Italy
The Internet of Things paradigm and the ubiquitous diffusion of Power Electronic Converters in many fields of application are suggesting the possibility of new ICT services associated to advanced power conversion. This work investigates the feasibility of shared centralized control and communications units able to control and synchronize different power converters, enabling real-time control and telemetry with a cloud approach on the Internet. Our research is focused on defining a proper communication bus making communications between devices and their remote control and telemetry possible in such a challenging environment.

Noureddine Boudriga
An optical wireless communication based 5G architecture to enable smart city applications
W. Boubakri, W. Abdallah, and N. Boudriga
Communication Networks and Security Research Lab., University of Carthage, Tunisia

One of the main objective of smart city is to enable efficient management of resources using advanced information and communication capabilities of the telecommunication infrastructure. One of the main challenge is to enable seamless connectivity between the different components composing the city infrastructure and users. Current communication approaches in smart cities applications are based on radio frequency (RF) transmission technology which cannot satisfy data rate demand and transmission delay requirement of smart city applications. The 5G communication network is being proposed to enhance the QoS provided by the mobile infrastructure which can contribute in the deployment of smart city applications. In particular, optical wireless technologies are envisioned by many research communities as a promising solution to provide the needed broadband connectivity and satisfy the quality of service (QoS) requirements of users. The main objective of this paper is to propose a communication architecture that can seamlessly integrate the optical wireless technology in the 5G communication networks to enable smart city applications deployment. The proposed network architecture is structured into three layers integrating different optical wireless technologies. More precisely, we study the deployment of optical access points (OAPs) in specific locations of interest in the city (such as road intersections, lighting systems, and signalling equipment) in order to enhance the performances of the sensing, tracking, and communication services. Furthermore, we propose to integrate a backhaul network composed of optical access points which is structured into a grid topology to enable communication using free space optical (FSO) transmission. The optical access points are expected to implement code-word based all-optical switching capability to forward traffic between optical access points. Moreover, access control using OFDMA are investigated to distribute connectivity between users belonging to the same VLC cell. Finally, issues related to cell dimensioning, wavelengths management and technology integration are discussed and some alternatives are proposed.

Joan García-Haro
Deployment of air quality monitoring sensors over a delay tolerant mobile ad-hoc network in public transportation systems
R. Asorey-Cacheda1, A. J. Garcia-Sanchez2, C. Zúñiga-Cañón3, P. Marco-Jornet2, P. A. Moreno-Riquelme2, and J. Garcia-Haro2
1Centro Universitario de la Defensa (University of Vigo), Spain
2Department of Information and Communication Technologies, Universidad Politécnica de Cartagena (UPCT), Spain
3Research Group COMBA I+D, Santiago de Cali University, Cali, Colombia
Poor air quality in urban environments is one of the major problems of modern cities. This paper presents a crowd-sensing approach that leverages the mobility of public transportation to monitor air quality in different inner city areas over the course of a day. To meet this objective, we present a system architecture for the compilation of environmental data using low-cost mobile sensor devices equipped in public transport vehicles. Thus, the network topology has been designed to be robust and reliable, tackling connectivity problems through the use of delay-tolerant networks and Bluetooth ad-hoc gateways, and to be flexible, dealing with changing topologies through the use of mobile ad-hoc networks. The tests carried out in the public transportation of Cartagena (Spain) show the feasibility of the proposed architecture for this vehicle to infrastructure service and the effectiveness of deploying a mobile measurement system instead of fixed stations, which is the usual solution for many smart cities.

Kira Kastell
Automated network selection for moving devices with respect to user preferences
K. Kastell, Fachhochschule Frankfurt am Main – University of Applied Sciences, Germany
The amount of different access networks rises. Although the networks have been designed for different purposes they all may serve different needs of moving devices. For the moving devices the choice of the best available network determines the quality of the transmission. Besides the network parameters, which should not only be considered as standardized values but also with real measurement data, the user preferences are also taken important for the acceptance of the choice. Depending on the communication need, mobile users may prefer a slower but more secure connection or a fast but less reliable one. Therefore we designed algorithm considering network parameters and user preferences. This can easily be extended to further networks as soon as they are emerging.

Tetsuya Kawanishi
90-GHz linear-cell systems for public transportation systems
T. Kawanishi1,2, A. Kanno2, and N. Yamamoto2
1Waseda University, Tokyo, Japan
2National Institute of Information and Communications Technology (NICT), Tokyo, Japan
This paper reviews 90-GHz high-speed wireless links and high-resolution radars based on linear-cell systems consisting of radio-over-fibre for waveform distribution. We also focus on applications for public transportation systems including airport runways, railways, etc.

José Antonio Lázaro
5G connected vehicles supported by optical fiber access
J. A. Lazaro, M. Coves, S. Sarmiento, J. A. Altabas, and A. Lerín
Universitat Politècnica de Catalunya, Barcelona, Spain

Future autonomous vehicle will require a high level of computation, communication, sensing and fast response actuation. Communication among vehicles and vehicles to infrastructure accessing to remote systems and services will help to reduce other requirements in computation and sensing. This paper revise current state of the art of wireless technologies as: LTE, LTE-A Pro, IEEE802.11p and 5G, as well as optical fiber access technologies as: TDM, WDM, D-WDM and uD-WDM, for the different communications requirements in diverse scenarios as: Vehicle-to-Infrastructure (V2I), Vehicle-to- Vehicle (V2V), Vehicle-to-Pedestrian (V2P) and Vehicle-to-Network (V2N).

Alicia Lopez
On the variability of launching and detection in POF transmission systems
A. López1, M. A. Losada1, J. Mateo1, and J. Zubia2
1Photonics Technology Group (GTF), Aragón Institute of Engineering Research (i3A), Universidad de Zaragoza, Spain
2University of the Basque Country, Bilbao, Spain
POF commercial active devices present a variety of designs where the coupling to the fibres is achieved by different types of connectors whose parameters determine their input and output angular power distributions. The particular design and connector type define the distance range of the fibre to the optical source and to the photodetector. Therefore, they establish the launching angular power distribution and the amount of power reaching the detector at a given angle, respectively. Moreover, the tolerances in these design parameters and connectors combined with other POF specific factors such as high numerical aperture and strong mode coupling produce a very high variability in the launching and detection conditions. As a result, a strong impact on POF transmission properties (attenuation and bandwidth) is expected. Here, our aim is to assess the variability of several optical sources and photodetectors and its effect over fibre transmission properties and also, to complete the matrix model for POFs and devices in order to accommodate source and detector variability, introducing a new model for the detector.

Vladimir Rastorguev
Algorithm for determining road boundaries in the radar system of an unmanned car
Bui Shi Han, V. V. Rastorguev, and V. Schneider
Moscow Aviation Institute (National Research University), MAI, Moscow, Russia

The algorithm for determining road boundaries in the automotive radar system (AR) of prevention collisions of an unmanned car in conditions of limited or no optical visibility is considered. The method of constructing this algorithm is based on the results of a statistical analysis of the characteristics of radar signals reflected from the road surface and its boundaries in the AR. The results of applying this algorithm to the processing of radar images (RI) of the road situation are presented, which are obtained as a result of full-scale testing of the experimental sample of AR. The results of this processing made it possible to estimate the accuracy of determining the road boundaries in the AR and to justify the requirements for algorithms for autonomous control of an unmanned vehicle.

Vladimir Rastorguev
Possibilities to observe small-size UAVs in the prospective airfield radar
A. E. Ananenkov, D. V. Marin, V. M. Nuzhdin, V. V. Rastorguev, and P. V. Sokolov
Moscow Aviation Institute (National Research University), MAI, Moscow, Russia

In this paper the actual problem of monitoring the movement of small-sized unmanned aerial vehicles (UAVs) flying within the airport territory, including near buildings and structures is considered. The possibilities of solving this problem using multifunctional airfield radar - Surface Movement Radar (SMR), are estimated. In accordance with ICAO requirements, this radar is designed to detect and control the movement of aircraft and vehicles on the territory of an airport in all weather conditions. Therefore, in addition to its main tasks, this radar should effectively detect and control the movement of small-size UAVs, especially in the airport's closed flight zones. The problems of technology for creating and selecting parameters for such radars are discussed. For a justified choice of the radar parameters, the results of the estimation of the effective scattering surface (Radar Cross-Section) values of the observed UAV are presented. The results of field tests of the experimental sample of the airfield radar for the detection of small UAVs under intense reflections from the underlying ground surface are presented.


DACINT invited presentations:

Prince Anandarajah
Multi-section semiconductor optical amplifiers for data centre networks
M. Hammad1, A. Anchal1, S. O’Duill1, P. Landais1, A. Kaszubowska-Anandarajah2, and P. M. Anandarajah1
1School of Electronic Engineering, Dublin City University, Glasnevin, Ireland
2Connect Centre, Trinity College Dublin, Ireland

The ever-growing Internet based services and applications, involving a huge amount of computing and storage resources, have been powered by data centres (DC) [1]. The storage and movement of data within the DCs is driving the requirement for cost-effective, higher capacity inter- and intra- next generation DC networks [2]. Within the context of these next generation DC networks, the ability to transmit very high data rates (100-400 Gb/s) over both short and long distances (intra or inter DC fibre links) is one of the main challenges (within the optical sector. The modulation format that is currently touted as the most suitable for such high capacities is 4-level pulse amplitude modulation (PAM4), which carries 2 bits per symbol. Optical amplification is needed for reach extension for inter- and intra- DC communications, Semiconductor optical amplifiers (SOAs) are needed to realize a low cost amplification solution. SOAs possess many advantages, including low power consumption, small footprint, wide bandwidth, being integrateable, and the ability to accommodate wavelength ranges beyond the scope of Erbium doped fibre amplifiers. However, the use of SOAs for linear amplification of C-band optical signals is still relatively limited, mainly due to the relatively large noise figure (NF) associated with them compared to erbium doped fiber amplifiers and low saturation powers of about 10 mW. Multi-section SOAs are known to possess superior NFs and larger saturation powers than an equivalent single-section SOA [3], and hence may provide performance benefit for reach extension for DC networks. In this work, we examine the use of a multi-section semiconductor optical amplifier (MS-SOA) [3] to provide an improvement in its use as a linear amplifier compared to a single section SOA. The MS-SOAs have been shown to have superior noise and linearity performance compared with single section SOAs. We configure the MS-SOA to operate in the low-NF mode with high saturation power mode and the equivalent single-section SOA. We compare the input power dynamic range for the MS-SOA and equivalent single-section SOA. We expect an improvement in the input power dynamic range of at least 3 dB [4]. The combination of a lower NF and higher saturation power enables crosstalk-free amplification of simultaneous multi-wavelength channels using the same SOA device.
[1] Cisco global cloud index: Forecast and methodology, 2014–2019, White Paper, Cisco, San Jose, CA, USA, Oct. 2015.
[2] C. Kachris and I. Tomkos, A survey on optical interconnects for data centers, IEEE Commun. Surveys Tuts., vol. 14, no. 4, pp. 1021–1036, 2012.
[3] R. Lennox, K. Carney, R. Maldonado-Basilio, S. Philippe, A. L. Bradley, and P. Landais, Impact of bias current distribution on the noise figure and power saturation of a multicontact semiconductor optical amplifier, OSA Optics Letters, vol. 36, no. 13, 2011.
[4] S O’Duill, P. Landais, and L. P. Barry, Estimation of the performance improvement of pre-amplified PAM4 systems when using multi-section semiconductor optical amplifiers, Applied Sciences 7, no. 9, 908, Sep. 2017.

Yossef Ben-Ezra
Application of all-optical memory for advanced modulation formats in communication intra-datacenter networks (intra-DCNs)

Y. Ben Ezra1,2 and B.I. Lembrikov1
1Faculty of Electrical Engineering and Electronics, Holon Institute of Technology, Israel
2MER Cello, Holon, Israel
New applications of optical communications generate enormous amount of data traffic which requires the time-sensitive analysis and processing of these big data at high performance computing infrastructures (HPCs), the storage and transport of all associated traffic by huge inter/intra exchanges in datacenters (DCs) [1]. As a result, the performance of the intra-datacenter networks (DCNs) must be improved [1]. Optical signal processing is an alternative to electronic techniques for processing information because it can substantially increase the processing speed of devices, the capacity and reach of optical links, and reduce the energy consumption and latency of communication systems [1]. In particular, all-optical memory is necessary for the elimination of the electronic bottleneck in modern optical communication networks [2]. Recently, we proposed a novel architecture of an ultra-fast all-optical memory loop based on the Mach-Zehnder interferometer (MZI) with quantum dot semiconductor optical amplifiers (QD SOA) as nonlinear components and investigated theoretically the proposed all-optical memory loop for the case of the 4 level PAM (4-PAM) format [3], [4]. In this paper, we investigated theoretically the application of this ultra-fast all-optical memory loop for the advanced modulation formats such as 8-PAM and quadrature amplitude modulation (QAM) in intra-datacenter networks (DCNs). We solved numerically the QD-SOA rate equations and the equations for MZI [4] in the case of the 8-PAM and QAM modulation formats. The simulation results show that for 8-PAM and QAM modulation formats the input signal and the same signal after the transmission over the memory loop are practically identical, and the pattern effect is absent.
[1] E. Agrell, M. Karlsson, A.R. Chraplyvy, et al., Roadmap of optical communications, Journal of Optics, vol. 18, no. 6, p. 063002, 2016.
[2] X. Yang, Q. Weng, W. Hu, High-speed all-optical memory using SOA MZIs: simulation and experiment, Optics Communications, vol. 285, pp. 4043-4047, 2012.
[3] Y. Ben Ezra, B.I. Lembrikov, All-optical memory based on quantum dot semiconductor optical amplifiers (QD-SOAs) for advanced modulation formats, ICTON 2016, paper Tu.A5.3 1-3.
[4] Y. Ben Ezra, B.I. Lembrikov, Ultra-fast all-optical memory based on quantum dot optical amplifiers (QD-SOA),. in: Optical Fiber and Wireless Communications, INTECH, 2017, pp. 279-293.

Enrico Ghillino
The Synopsys software environment to design and simulate photonic integrated circuits: A case study for 400G transmission
E. Ghillino1, E. Virgillito5, P. V. Mena1, R. Scarmozzino1, R. Stoffer2, D. Richards3, A. Ghiasi4, A. Ferrari5, M. Cantono5, A. Carena5, and V. Curri5
1Synopsys, Inc., Ossining, NY, USA
2Synopsys, Inc., Enschede, the Netherlands
3College of Staten Island, CUNY, Staten Island, NY, USA
4Ghiasi Quantum LLC, Cupertino, CA, USA
5DET, Politecnico di Torino, Italy
To afford the dramatic intra- and inter-datacenter traffic growth envisioned for the decade, the IEEE P802.3bs Task Force is targeting the standardization of 200 Gb/s and 400 Gb/s Ethernet. Transceivers adopting this standard will need to substantially reduce cost and power consumption with respect to similar equipment that are currently the state-of-the-art for long-haul networks. The most promising solution for such a challenging objective is offered by integrated photonics, a state-of-the-art technology capable of providing high-speed components and large-scale circuits with high-volume, high-yield, and low-cost manufacturing.  Synopsys proposes an integrated software (SW) environment capable of assisting with virtual prototyping and testing of the circuit before proceeding with the physical implementation. It is the integration of the OptSim Circuit tool for schematic-driven photonic integrated circuit (PIC) design, with the PhoeniX OptoDesigner photonic layout tool, and the RSoft Photonic Component Design Suite, thus providing a single modeling solution at the circuit, layout, and device levels of abstraction. In this work, we first present this integrated SW environment, focusing on its potential and usability. Then, we use the APSUNY Silicon Photonics Integrated Circuit Process Design Kit (PDK) library sponsored by AIM Photonics to model a PM-16QAM transceiver with a 400G transmission data rate.

Madeleine Glick
Transceiver scaling and the IPSR-I roadmap
M. Glick, College of Optical Sciences, University of Arizona, Tucson, USA
As part of the Integrated Photonic Systems Roadmap International effort to define future needs, gaps and research directions, we explore transceiver scaling technologies to data rates > 100Tb/s for data centers and high performance computing.

Helmut Griesser
PAM-4 and DMT for inter-data center connections and 5G fronthaul applications
H. Griesser1, N. Eiselt2, A. Dochhan2, M. Eiselt2, and J.-P. Elbers1
1ADVA Optical Networking SE, Munich, Germany
2ADVA Optical Networking SE, Meiningen, Germany
Modulation formats with intensity modulation (IM) and direct detection (DD) are attractive due to the simple optical configuration, the low power consumption and a small footprint. We revisit the performance of 56Gb/s and 112Gb/s four-level multilevel intensity modulation (PAM-4) and discrete multitone transmission (DMT) for wavelength multiplexed high speed connections with distances up to 80-100km between data centers and for future 5G fronthaul architectures with a reach of 10-20km. Enabled by digital signal processing (DSP) DMT as well as PAM-4 and its partial response variant are shown to be suitable for the proposed applications. The paper will discuss the specific pros and cons with respect to component properties and the required signal processing effort.
[1] Eiselt, et al. (2016), Experimental comparison of 56Gbit/s PAM-4 and DMT for data center interconnect applications, in Proc. ITG-Symp. Photonic Networks.
[2] Eiselt et al. (2017), Real-time 200 Gb/s (4 x 56.25 Gb/s) PAM-4 transmission over 80 km SSMF using quantum-dot laser and silicon ring-modulator, in Proc. OFC.
[3] Eiselt, et al. (2016), Real-time evaluation of 26-GBaud PAM-4 intensity modulation and direct detection systems for data-center interconnects, in Proc. OFC.
[4] Eiselt, et al. (2016), Experimental demonstration of 112-Gbit/s PAM-4 over up to 80km SSMF at 1550nm for inter-DCI applications, in Proc. ECOC.
[5] Eiselt et al. (2016), First real-time 400G PAM-4 demonstration for inter-data center transmission over 100km of SSMF at 1550nm, in Proc. OFC, paper W1K.5.
[6] Eiselt, et al. (2016), Evaluation of Real-Time 8x56.25Gb/s (400G) PAM-4 for Inter-Data Center Application over 80km of SSMF at 1550nm, Journal of Lightwave Technology.
[7] Eiselt, et al. (2018), Performance comparison of 112 Gb/s DMT, Nyquist PAM4 and partial-response PAM4 for future 5G Ethernet-based fronthaul architecture, Journal of Lightwave Technology.

Kambiz Jamshidi
Design trade-offs of high-speed energy-efficient modulators for short-range optical interconnect
S. Hosseini, N. K. Kamutam, M. Catuneanu, and K. Jamshidi
Technische Universität Dresden, Faculty of Electrical and Computer Engineering, Germany
Data center and high-performance computers need quick distribution of tasks and information amongst a large number of nodes. Therefore, reconfigurable energy-efficient optical interconnects for the rack to rack, board to board, chip to chip and intra-chip communication is required. The electro-optical modulator is the key component for this purpose which needs to be optimized at the component level. Performance analysis of the modulators is necessary to enable system designers to choose proper designs which satisfy system level parameters such as loss, bandwidth, and energy efficiency, taking into account link budget limitations. In this paper, the performance trade-offs of Mach-Zehnder, corrugated waveguide, and ring modulators are investigated in terms of physical parameters, like drive voltage, length, and doping levels.

Diego Perez-Galacho
Silicon modulators for the generation of advanced modulation formats
D. Perez-Galacho1,2, L. Bramerie3, C. Baudot4, M. Chaibi3, S. Messaoudène4, N. Vulliet4, L. Vivien2, F. Boeuf4, C. Peucheret3, and D. Marris-Morini2
1ITEAM research institute, Universitat Politècnica de València, Spain
2Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, C2N-Orsay, France
3Université Rennes, CNRS, FOTON – UMR 6082, Lannion, France
4ST Microelectronics, Crolles, France
Silicon photonics has appeared in the recent years as the best suited technology for fulfilling the demands of future optical interconnects. In this framework, modulators are key elements in the performance of an optical link. In order to achieve modulation in silicon the Free-Carrier Plasma Dispersion (FCPD) effect is normally used. In fact, silicon modulators based on carrier depletion have been demonstrated with outstanding performance up to 40Gbps. However, keeping up with bandwidth demands will require the use of more complex modulation formats like PAM4 or QPSK. At the same time, in order to avoid dispersion compensation circuits, the use of the O-Band (1260nm-1360nm) is preferred for short range optical communications. In this work we present our results on the generation of BPSK/QPSK signals using silicon modulators.

Roberto Llorente
Multidimensional multiplexing in multicore fibre for hybrid optical backhaul provision: The XCORE approach
R. Llorente1, M. Morant1, J. S. Bruno2-3, V. Almenar2, J. L. Corral1, J. M. Fuster1, and J. Valls2
1Nanophotonics Technology Center, Universitat Politècnica de València (UPV), Spain
2Instituto de Telecomunicaciones y Aplicaciones Multimedia (ITEAM), UPV, Spain
3Laboratorio Procesamiento Digital (DPLab), Universidad Tecnológica Nacional, Buenos Aires, Argentina

In this paper a critical overview of the required technologies to open up multi-core fibre as a valid solution leveraging optical access networks infrastructure already deployed on the field for hybrid radio-optical backhaul is reported. Optical transmission using multi-core fibre (MCF) has been already proposed as an interesting solution for optical access network, providing a lower installation cost and higher transmission capacity. In this work, we propose and evaluate experimentally the joint use of SSMF and MCF for and hybrid backhaul solution supporting single-carrier (SC) and multi-carrier OFDM connectivity for cellular service and radio transport provision, respectively. The two modulations schemes are supported as a multidimension modulation employing space-dimension multiplexing at the same wavelength over different cores of the MCF, in particular, we compare the performance of single-carrier (SC) and multi-carrier OFDM signals. SC-QAM signals over 2 GHz bandwidth can provide up to 14.22 Gb/s using 256QAM modulation, while OFDM signals with 512 subcarriers over the same bandwidth provide up to 14.36 Gb/s per channel. The optical performance is evaluated for an optical link comprising 10 km on standard single-mode fibre (SSMF) and 150 m multi-core fibre (MCF) for the final connectivity stage considering different received optical power levels. Experimental results confirm that both OFDM and SC-QAM signals meet error-free BER thresholds for modulation orders up to 256QAM, although OFDM requires higher received power levels compared to SC-QAM implementation.

Oskars Ozolins
Short reach optical interconnects with single externally modulated laser operated in C-band
O. Ozolins1, Xiaodan Pang2,1, A. Udalcovs1, Lu Zhang2, R. Schatz2, U. Westergren2, G. Jacobsen1, S. Popov2, and Jiajia Chen2
1RISE Acreo, Kista, Sweden
2KTH Royal Institute of Technology, Stockholm, Sweden

Datacenters experience massive traffic growth due to expansive growth of cloud services and online gaming [1]. This trend leads to technical and economic challenges to keep up scalability for bandwidth in short reach optical interconnects. It is of critical importance to enable a cost-efficient solution for 400 Gbps links [2]. Solution for 400 GbE based on four optical lanes [3] or even two optical lanes [4] may be more attractive to reduce power consumption and complexity of parallelism. This requires InP and silicon opto-electronic components with more than 70 GHz bandwidth [2]. In this talk, we report on several experimental demonstrations for short reach optical interconnects in C-band. We review demonstrations of up to 200 Gbit/s 4-pulse amplitude modulation (PAM) [4] and up to 200 Gbit/s discrete multitone (DMT) [5] transmission with a cost-efficient monolithically integrated externally modulated laser (EML) with large bandwidth. Related digital signal processing techniques are also discussed in terms of practical implementation and complexity, paving the way for cost-effective interconnects using high speed advanced modulation formats.
[1] O. Ozolins, et al., High-speed optical interconnects with integrated externally modulated laser,” in Proc. ICTON 2017, invited paper Tu.B3.3.
[2] O. Ozolins, et al., 100 GHz externally modulated laser for optical interconnects, J. Lightwave Technol., Invited paper, vol. 35, no. 6, pp. 1174-1179 (2017).
[3] X. Pang, et al., Experimental study of 1.55-µm EML-based optical IM/DD PAM-4/8 short reach systems, Photonics Technology Letters, 29(6), 523-526 (2017).
[4] O. Ozolins, et al., 100 Gbaud 4PAM link for high speed optical interconnects, in Proc. ECOC 2017, paper P2.SC5.6.
[5] L. Zhang, et al., Nonlinearity-aware 200-Gbit/s discrete multi-tone transmission for C-band short-reach optical interconnects with a single packaged EML, Opt. Lett. 43(2), pp. 182-185 (2018).

Ioannis Tomkos
Cost and power consumption comparison of 400Gbps intra-datacenter transceiver modules
T. Rokkas, I. Neokosmidis, and I. Tomkos
inCITES Consulting SARL, Strassen, Luxembourg
Athens Information Technology (AIT), Marousi, Greece
We make a quantitative comparison, in terms of cost and power consumption, of future 400G transceiver modules that could be used for intra-data center communication. The current characteristics of proposed transceiver modules, along with their advantages and drawbacks, are initially presented. Possible migration paths towards 400G and beyond transceivers are also discussed. Estimations for the cost and power consumption for scaling a DC using the Facebook’s Fabric architecture using different modules are also presented.

David Thomson
Towards high speed and low power silicon photonic data links
D. J. Thomson1,  K. Debnath1,4, Weiwei Zhang1, Ke Li1, Shenghao Liu1, Fanfan Meng1, A. Z. Khokhar1, C. Littlejohns1, J. Byers2, L. Mastronardi1, M. K. Husain2, F. Y. Gardes1, S. Saito2, Xia Chen1, M. M. Milosevic1, Y. Franz1, A. F. J. Runge1, S. Mailis1, A. C. Peacock1, P. Wilson3, and G. T. Reed1
1Optoelectronics Research Centre, University of Southampton, UK
2Faculty of Physical Sciences and Engineering, University of Southampton, UK
3Department of Electronic and Electrical Engineering, University of Bath, UK
4Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology, India

Silicon is a low-cost material platform in which it is possible to form photonic integrated circuits serving a number of applications from optical communications to sensing. For optical communications applications, e.g. short reach data communication within data centres, the optical modulator is a key component with its capabilities having a significant bearing on the overall performance of the photonic circuit. In this paper we report our recent work on optical modulators in silicon and their integration with CMOS electronics on silicon.

Juan Jose Vegas Olmos
400G Interconnects for data centres and high-performance computing – What is now and what is next?
J.J. Vegas Olmos1, J.J. Mohr1, S.B. Christensen1, K.E. Skouby2, and J.P. Turkiewicz3
1Mellanox Technologies, Roskilde, Denmark
2Aalborg University, Center for Communications, Media and Information Technologies, Copenhagen, Denmark
3Institute of Telecommunications, Warsaw University of Technology, Poland
In this talk, different aspects of scaling interconnect systems beyond 400Gbit/s towards 1Tbit/s capacity are examined and discussed. We will explain the current evolution from NRZ to PAM-4 as modulation format of choice in high-capacity interconnects, and highlight some key challenges to be resolved. Furthermore, alternative advanced modulation formats which can expand even further the capacity per single lane will be presented, including experimental demonstrations on 850nm VCSELs. Role playing devil’s advocate for different approaches, ultimately we concede on three points: we will need to provide more capacity soon, any roadmap in terms of modulation format is blurry right now, and optics is plateauing in terms of performance while electronics keep going.


DCN invited presentations:

Antonella Bogoni
The orbital angular momentum of light for ultra-high capacity data centers
M. Scaffardi1, M. N. Malik1,2, Jiangbo Zhu3, G. Goeger4, Ning Zhang5, C. Klitis5, Yabin Ye4, P. Rydlichowski6, V. Toccafondo1, M. Lavery5, N. Andriolli2, Siyuan Yu3, M. Sorel5, and A. Bogoni2
1CNIT, Pisa, Italy
2Scuola Superiore Sant’Anna, Pisa, Italy
3University of Bristol, UK
4Huawei Technologies Dusseldorf GmbH, Munich, Germany
5University of Glasgow, UK
6Poznan Supercomputing and Networking Center (PSNC), Poland

The potential of orbital angular momentum (OAM) of light in data center scenarios is presented. OAMs can be exploited for short reach ultra-high bit rate fiber links and as additional multiplexing domain in transparent ultrahigh capacity optical switches. Recent advances on OAM integrated photonic technology are also reported.  Finally demonstration of OAM-based fiber links (aggregate throughput 17.9Tb/s) and two layers OAM-WDM based optical switches are presented exploiting OAM integrated components and demonstrating the achievable benefits in terms of size, weight and power consumption (SWaP) compared to different technologies.

Nicola Calabretta
Performance assessment of OPSquare data center network with elastic allocation of WDM transceivers
Xuwei Xue, Fulong Yan, Bitao Pan, and N. Calabretta
IPI – Institute of Photonic Integration, Eindhoven University of Technology, The Netherlands

Under realistic OPSquare data center traffic model, the impact of the packet loss ratio and sever end-to-end latency of elastic allocation of WDM transmitters at top of rack (ToR) is numerically investigated. Results show that with limited 50 KB buffer, a sever end-to-end latency lower than 2µs and packet loss ratio below 10-6 could be guaranteed for different traffic patterns and loads when the WDM transmitters at ToRs are adaptively allocated. An analyses on costs and power consumption indicate that the elastic allocation of WDM transmitters will not cause dramatic fluctuation in power consumption, while cost will increase with more usage of transmitters.

Taisir El-Gorashi
On energy efficiency of networks for composable datacentre infrastructures
O. Ajibola, T. E. H. El-Gorashi, and J. M. H. Elmirghani
School of Electronic and Electrical Engineering, University of Leeds, UK

This paper evaluates the optimal scale of datacentre (DC) resource disaggregation for composable DC infrastructures and investigates the impact of present day silicon photonics technologies on the energy efficiency of different composable DC infrastructures. We formulated a mixed integer linear programming (MILP) model to this end. Our results show that present day silicon photonics technologies enable better network energy efficiency for rack-scale composable DCs compared to pod-scale composable DCs despite reported similarities in CPU and memory resource power consumption.

Jaafar Elmirghani
Experimental evaluation of passive optical network based data centre architecture
A. E. A. Eltraify, M. O. I. Musa, A. Al-Quzweeni, and J. M. H. Elmirghani
School of Electronic and Electrical Engineering, University of Leeds, UK

Passive optical networks (PONs) technology is increasingly becoming an attractive solution in modern data centres as it provides energy efficient, high capacity, low cost, scalable, and flexible connectivity. In this paper we report the implementation of a PON based data centre architecture that provides high resilience and high speed interconnections by providing alternative communication routes between servers in different racks. Each rack is divided into several groups of servers and connects to other racks and the OLT through a set of server that acts as relay servers. We implement the switching and routing functionalities within servers using 4x10GE Xilinx NetFPGA, and demonstrate end-to-end communication using IP cameras live video streaming over up to 100 km optical connections through WDM nodes and the PON network.

Roberto Gaudino
Direct-detection single-sideband systems: Performance comparison and practical implementation penalties
D. Pilori and R. Gaudino
Politecnico di Torino, Dipartimento di Elettronica, Italy
There is a growing research interest towards high-capacity communication systems for inter data-center (~80 km) communications. While coherent systems are a mature and high-performance technology, its cost is still very high compared to simpler direct-detection solutions. Recently, advanced digital signal processing (DSP) techniques, such as Single Side-Band (SSB) transmission and Kramers-Kronig (KK) receivers have been proposed to increase both spectral efficiency and reach of such direct-detection systems. Apart from the DSP techniques, the main drawback of these solutions is the requirement of a strong (i.e. several decibels higher than the signal) carrier added at the transmitter. This solution inevitably decrease the overall optical signal-to-noise ratio (OSNR) and potentially increase the impact of fiber Kerr non-linearities. In this contribution, after a thorough literature review, will provide further insights on the practical implementation penalties which arise from the addition of such carrier. In particular, we will focus on the modulator biasing technique to add such carrier, and on the impact of fiber Kerr non-linearities to the transmission of a SSB-DMT signal.

Young Lee
Auto-scaling mechanism in the ICT converged cross stratum orchestration architecture for zero-touch service and network management
Young Lee1, R. Vilalta2, R. Casellas2, R. Martínez2, and R. Muñoz2
1Huawei Technologies, Plano, USA

2Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels (Barcelona), Spain
This paper is aimed to provide a novel approach for an auto-scaling mechanism that are applied in the ICT converged cross stratum orchestration (CSO) architecture. CSO refers to an end-to-end orchestration across Application orchestration, Data Center SDN orchestration, and WAN SDN orchestration so that applications can be created seamlessly and optimally for operators and their customers. The auto-scaling mechanism presented in this paper is built on active monitoring of both DC compute/storage/network resources and DCI Transport network resources and then provides dynamically configurable auto-scaling and resource re-allocation. This mechanism will help tremendously the operators to control and manage their networks in an automated fashion.

Ronald Romero Reyes
Infrastructure cost evaluation of intra-data centre networks
R. Romero Reyes and T. Bauschert
Technische Universität Chemnitz, Germany

This paper presents a cost evaluation of five modern Intra-data center network architectures, namely Brocade leaf/spine, fat-tree, hybrid-fat-tree, Facebook 4- post and Facebook fabric. Those architectures are evaluated in terms of their performance along with the Capex required to build them. Finally, a cost evaluation of future data center networks scenario is introduced.

Christos Spatharakis
NEPHELE: Vertical integration and real time demonstration of an optical datacenter network
C. Spatharakis1, K. Tokas1, I. Patronas1,2, P. Bakopoulo3, D. Reisis1,2, and H. Avramopoulos1
1Photonics Communications Research Laboratory, National Technical University of Athens, Greece
2Electronics Laboratory, Faculty of Physics, National and Kapodistrian University of Athens, Greece
3Mellanox Technologies, Yokneam, Israel

Riding on Moore’s law, established datacenter network infrastructure technologies are scaling up rapidly; however, increasing concerns are being expressed by the industry that these technologies could be outpaced in the near future by the sheer growth of the traffic and new technologies are sought. In this backdrop, optical switching is gaining momentum as a potential path for gracefully scaling datacenter networks, due to its inherent speed, energy efficiency and transparency to bitrate and protocol. European project NEPHELE is developing an optical network infrastructure that leverages optical switching within a software-defined networking (SDN) framework to overcome the bandwidth and energy scaling challenges of datacenter networks. Within this project, a vertically integrated optical datacenter network test-bed prototype was set up and its operation was demonstrated in lab environment. Different scenarios using the NEPHELE dataplane are reported, underpinning the feasibility of the proposed network architecture. Moreover, dynamic allocation of network resources is also envisaged, leveraging the slotted operation of the reported optical datacenter network. Finally, the evaluation of a Wavelength Selective Switch (WSS) based on commercial off-the-self-components is reported, scaling up to eight wavelengths and enabling optical switching in ultra-fast dynamic operation.

Weiqiang Sun
Planning of geo-distributed cloud data centers in fast developing economies
Ruiyun Liu, Weiqiang Sun, and Weisheng Hu
Shanghai Jiao Tong University, China

In recent years, with the rapid development of big data, artificial intelligence and cloud computing, the construction of cloud data centers has entered into a fast-growing period, especially in fast developing economies. The placement for geo-distributed cloud data centers has a great impact on costs and performance. In this paper, we propose a framework to determine the optimal placement of geo-distributed cloud data centers, taking into considering both cost minimization and network performance. In we apply this framework to the placement to cloud data centers in China. We show how the DC placement may be affected by network performance requirements. We also show how factors like population mobility and adoption of clean energy, typical in fast developing economies, may affect DC placement. We research provides insights to the long term DC planning in fast developing economies.


ESPC invited presentations:

Walter Belardi
Hollow core antiresonant fibers: Novel designs, materials and applications
W. Belardi, A. Lewis, F. De Lucia, and P. J. Sazio
Optoelectronics Research Centre, University of Southampton, UK

The development of hollow core optical fibers based on the antiresonant optical principle is gaining a significant interest within the optical fiber research community due, among others, to their broadband transmission, mid-infrared and ultra-violet operation, as well as their unique ability to handle high optical power. In this work, we will offer an update on our recent activities related to the introduction of novel hollow core fiber designs and the fabrication and development of hollow optical fibers based on composite materials. These novel forms of optical fibers may unable a range of novel, still unexplored applications.

Ignac Bugar
Ultrafast all-optical switching using all-solid dual-core photonic crystal fiber
I. Bugar1, M. Longobucco1,2, J. Cimek1,2, L. Curilla3, D. Pysz1, and R. Buczynski1,2
1Institute of Electronic Materials Technology, Warsaw, Poland
2Department of Geophysics, Faculty of Physics, University of Warsaw, Poland
3Optics11, Amsterdam, Netherlands
Propagation of femtosecond solitons is studied in a novel dual-core all-solid photonic crystal fibre combining two thermally matched soft glasses, which ensures highly nonlinear interaction. The microstructure of the fibre was designed by optimization of the fibre dispersion and coupling properties with aim to ensure switchable self-trapping of high-order solitons. We present preliminary numerical simulations of the nonlinear propagation at different excitation wavelengths with various ratios of the anomalous dispersion and coupling length values. According to the results spectral intensity switching potential of the new all-solid dual-core photonic crystal fibre is predicted applying 1700 nm excitation wavelength at 14 mm fibre length.

Maciej Dems
Optical modes in monolithic high contrast gratings
M. Dems, M. Gębski, and T. Czyszanowski
Institute of Physics, Lodz University of Technology, Poland
In this work, we present the analysis of optical modes in monolithic high contrast gratings (MHCGs). We model the reflected wave and investigate the diffraction of the light incident at the high-refractive-index side. When properly designed, MHCGs show no reflected light scattering, We explain this phenomenon and present its application for modern high-speed telecommunication lasers.

Niels Gregersen
Which computational methods are good for analyzing large photonic crystal membrane cavities?
R. Malureanu, J. Rosenkrantz de Lasson, L. Hagedorn Frandsen, P. Gutsche, S. Burger, O. S. Kim, O. Breinbjerg, A. Ivinskaya, Fengwen Wang, O. Sigmund, T. Häyrynen, A. V. Lavrinenko, J. Mørk, and N. Gregersen
DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Lyngby, Denmark
By introducing defects into an otherwise periodic photonic crystal lattice, high quality (Q) factor cavities may be formed. However, the size and the lack of simplifying symmetries in the photonic crystal membrane make these types of cavities exceptionally hard to analyze using numerical simulation methods. In this work, we consider two different line defect cavities and we compute their Q factors using state-of-the-art optical simulation tools. We show that certain simulation methods perform much better than others in the analysis of these challenging structures.

Romuald Houdré
Finite‐size and disorder effects on slow‐light propagation in an extended photonic crystal coupled‐cavity waveguides with group-index bandwidth product exceeding 0.47
M. S. Abdel-Aliem1, Yiming Lai2,3, M. Minkov1,4, V. Savona1, A. Badolato5, and R. Houdré1
1Institute of Physics, Ecole Polytechnique Fédérale de Lausanne EPFL, Switzerland
2Department of Physics and Astronomy, University of Rochester, USA
3Current address: DiCon Fiberoptics, Richmond, CA, USA
4Current address: Ginzton Laboratory, Stanford University, CA, USA
5Department of Physics and Max Planck Centre for Extreme and Quantum Photonics, University of Ottawa, Canada

Slow light propagation through engineered band dispersion in photonic structures is a highly promising tool for realizing integrated optical delay lines and efficient photonic devices through enhanced optical nonlinearities. A primary goal is to achieve devices over the largest possible bandwidth with large group index and minimal dispersion (i.e. approximately constant group index), flat transmission spectrum, which otherwise would hinders their use for pulse propagation, with setbacks such as pulse distortion and generation of echoes, thus enabling multimode and pulsed operation. We present an experimental proof of record-high group-index bandwidth product (GBP = ng ∆ω⁄ω) in genetically optimized coupled-cavity waveguides (CCWs) made of staggered modified L3 photonic crystal cavities. The optimization procedure was applied to the unit cell to achieve maximal GBP combined with low losses. The resulting designs were realized in Si slabs, where CCWs of length ranging between 50 and 800 cavities were fabricated. The samples were characterized by measuring the CCW transmission, the mode dispersion and the group index ng through Fourier-space imaging. Various cavity designs were investigated, with theoretical group index ranging from ng = 37 to ng > 100. Record-high GBP = 0.47 was demonstrated over a bandwidth approaching 20 nm, with ng = 37, a very homogeneous flat-top transmission profile and losses value below 67 dB/ns. On a different design, an average ng = 107 with 15 % variation over 7.4 nm was measured. These values range among the best ever demonstrated for a silicon device. Through Fourier-space imaging, slow light properties are directly extracted by reconstructing the dispersion maps, allowing distinguishing finite-size effects from those arising due to structural disorder. We elucidate the influence of the CCW length and design on the adherence of the dispersion to the theoretically predicted periodic-boundary profile. Limitations on slow-light propagation are identified in terms of decay length and the onset of diffusive light transport, considering state-of-the-art fabrication. For such systems where light propagation relies on a resonant tunnelling mechanism, we show that disorder has a cumulative effect on the device response, ultimately capping the achievable slow-down factor. With the aid of Raman spectroscopy, we further explain how the mitigation of stress in the layer is mandatory towards preventing light trapping in the waveguide, in order to retrieve the full operational bandwidth.

Jesper Mørk
Fano resonances for realizing compact and low energy consumption photonic switches
D. A. Bekele, Yi Yu, Hao Hu, L. K. Oxenløwe, K. Yvind, and J. Mørk
DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Lyngby, Denmark
Fano resonances in photonics have recently enabled demonstrations of interesting applications such as optical switching, lasing and sensing. They occur as a result of the interference between discrete states and continuum band of states. Discrete modes of interest can be implemented in cavity structures while continuum set of modes can be realized in optical waveguides. The possibility of designing high quality factor nanocavities and low-loss waveguides in photonic crystal structures offers a suitable platform for the realization of Fano resonances in photonic integrated circuits. Here, we present our recent experimental investigations of InP photonic crystal Fano resonances for wavelength conversion, non-reciprocal transmission, optical-time domain demultiplexing, pulse carving and lasing applications. Device physics, limitations and future perspectives will also be presented.


FiWiN5G invited presentations:

Bogdan Andrus
Performance evaluation of NETCONF-based low latency cross-connect for 5G C-RAN architectures
 B. Andrus1,2, A. Autenrieth1, S. Pachnicke3, S. Zou1, J. J. V. Olmos4, and I. T. Monroy5
1ADVA Optical Networking, Martinsried, Germany
2Technical University of Denmark, Department of Photonics Engineering, Lyngby, Denmark
3Kiel University (CAU), Kiel, Germany
4Mellanox Technologies, Roskilde, Denmark
5Technical University of Eindhoven, Department of Electrical Engineering, Netherlands
The development of 5G wireless technology is in progress looking to cope with the increasing demands for high capacity, low latency, and ubiquitous mobile access. Cloud/Centralized Radio Access Networks (C-RAN) has been proposed as a promising approach to address the 5G benchmarks. C-RAN is a rising mobile network architecture based on the centralization and pooling of baseband processing elements, with the scope of increasing resource utilization efficiency and air-interface performance gains with fast scaling multi-cell coordination. In this paper we focus on proposing and evaluating a flexible low-latency cross-connect (XC) switch that allows a dynamic scheduling of networking resources between baseband units (BBUs) and remote radio heads (RRHs) in C-RAN deployments. On the one hand, we develop a control plane mechanism for manipulating the XC configuration and state data based on a custom YANG model and Network Configuration (NTCONF) protocol. Using a standard open NETCONF interface, automation of heterogeneous C-RAN resource assignment can be facilitated for 5G architectures. Secondly, we evaluate the performance of our XC in relation to the C-RAN stringent requirements and show that the latency and jitter introduced have negligible influence compared to radio interface limits. The impact of switching delay on the performance of a live system has yet to be tested however, a measured average switching time of 252 ms could still disrupt the on-going connections.

George Kalfas
Medium-transparent packet-based fronthauling for 5G Hot-spot networks
G. Kalfas1, P. Maniotis1, A. Mesodiakaki1, S. Papaioannou1, Ch. Vagionas1, M. Gatzianas1,2, E. Kartsakli3, and J. Vardakas3
1Department of Informatics, Aristotle University of Thessaloniki, Greece
2International Hellenic University, Thessaloniki, Greece
3Iquadrat Informatica, Barcelona, Spain

Ultra-dense networking (UDN) is one of the most important and ambitious research directions currently lying in the spotlight of 5G innovation. In order to meet the traffic density requirement and cope with the technical challenges of hot-spot scenarios exhibiting extreme user density in very confined geographical areas, the 5G networks must undergo radical technological and architectural innovations that support a broad solution portfolio. This solution mix includes expansion of the spectrum to the millimeter wave (mmWave) band, massive Multiple Input Multiple Output (mMIMO) antennas and network densification through Small-Cell (SC) deployment. Since the current CPRI-based mobile fronthaul cannot cope with massive mmWave multi-Gbps traffic streams, it is imperative to introduce a novel centralized and converged 5G architecture, specifically designed to facilitate mmWave access to massive amounts of users. To this end, we propose a Medium Transparent MAC (MT-MAC) protocol specifically designed to operate over a converged mmWave analog FiWi fronthaul infrastructure. The proposed protocol and underlying architecture allow for fast and direct negotiation of wavelength, frequency and time resources between the centralized unit and the mmWave wireless terminals, while offering fast on-demand link formation following closely the demand fluctuation at the picocell level. In this paper we investigate the functional and physical consolidation as well as the respective performance of MT-MAC-enabled fronthaul and report on its application and suitability for mmWave ultra-dense 5G access networks.

Paulo Monteiro
Millimeter-wave real-time all-digital transmitter with electro-optical upconversion
S. S. Pereira, A. Lorences-Riesgo, D. C. Dinis, A. S. R. Oliveira, J. N. Vieira, and P. P. Monteiro
Instituto de Telecomunicações / Universidade de Aveiro - DETI, Campus Universitário de Santiago, Aveiro, Portugal
In this work, we demonstrate a real-time architecture for enabling the use of all-digital transmitters in mm-wave frequency bands. We propose the combination of delta-sigma modulation techniques and electro-optical upconversion stages to ease the stringent requirements in the design of RF front-ends. In our proof-of-concept demonstration, the real-time delta-sigma modulation technique is synthesised and prototyped into a field-programmable gate array (FPGA). Experimental results are reported in the range from 27 GHz up to 63 GHz and evaluated in terms of error-vector magnitude (EVM). The promising results demonstrate the scalability and flexibility of the proposed technique towards the design of highly-integrated and agile front-ends for next generation of communications.

Filippo Ponzini
Optical access network solutions for 5G fronthaul
F. Ponzini1, K. Kondepu2, F. Giannone2, P. Castoldi2, and L. Valcarenghi2
1Ericsson Research, Pisa, Italy
2Scuola Superiore Sant’Anna, Pisa, Italy

This paper first highlights the capacity and latency requirements of the 5G mobile fronthaul and the fronthaul architecture detailing also the motivations for these requirements. The it overviews the optical access network solutions that could be used for the fronthaul and for which functional split they are deemed more appropriate. Finally, an evaluation of some solutions in a lab testbed is presented.

Christos Verikoukis
A C-RAN based 5G platform with a fully virtualized, SDN controlled optical/wireless fronthaul
K. Ramantas1, A. Antonopoulos2, E. Kartsakli1, P.-V. Mekikis1, J. Vardakas1, and C. Verikoukis2
1Iquadrat Informatica S.L., Barcelona, Spain
2Telecommunications Technological Center of Catalonia (CTTC/CERCA), Castelldefels, Spain

This paper will detail the design of a 5G platform based on the C-RAN architecture, with a fully virtualized Radio Access Network (RAN) and an optical/wireless fronthaul. The wireless and optical domains are controlled by an hierarchy of SDN controllers, which are responsible for end-to-end optimization of the platform, including the fronthaul and 5G air interfaces. The proposed architecture adopts a modular eNB design, where virtualized BBU and RRH entities are implemented with Commercial Off-Τhe-Shelf (COTS) components. Moreover, a mmWave RAU is connected to the BBU via a feeder optical fiber, interconnecting one or more RRH units with the BBU over mmWave interfaces. COTS components and Ethernet interfaces are employed for C-RAN prototyping of our platform, facilitating flexibility, cost reduction and increased scalability.


Flex-ON invited presentations:

Silvio Abrate
Quality of transmission estimator enabling the transparency paradigm in legacy IMDD networks
E. Virgillito1, S. Straullu2, M. Cantono1, A. Castoldi3, R. Pastorelli3, P. Savio2, S. Abrate2, and V. Curri1
1Politecnico di Torino, Torino, Italy
2Istituto Superiore Mario Boella, Torino, Italy
3SM-Optics, Vimercate, Italy

Optical transmission based on IMDD modulation and dispersion-managed links is still of interest for the community because of its low-cost. Although the optical technologies deployed for this networking scenario are well-consolidated, operators are still requiring software-based orchestration capabilities. To this purpose, the line system and in general the network management software need to rely on a Quality-of-Transmission Estimator (QoT-E) enabling a quick evaluation of lightpath performance for the optical feasibility and network optimization. In this work, we propose a QoT-E considering the joint effect of SPM, XPM and FWM.

Alex Alvarado
Geometrically-shaped 64-point constellations via achievable information rates
Bin Chen1;2, C. Okonkwo1, D. Lavery3, A. Alvarado1
1Department of Electrical Engineering, Eindhoven University of Technology (TU/e), The Netherlands
2School of Computer and Information, Hefei University of Technology (HFUT), Hefei, China
3Department of Electronic and Electrical Engineering, University College London (UCL), London, UK

Achievable information rates (AIRs) are discussed as a performance metric to design optimized geometrically-shaped constellations. Mutual information and generalized mutual information are used to maximize the AIRs of 64-point constellations.

António Eira
On the capacity and scalability of metro transport architectures for ubiquitous service delivery
A. Eira1, N. Costa1, and J. Pedro1,2
1Coriant Portugal, Amadora, Portugal
2Instituto de Telecomunicações, Instituto Superior Técnico, Lisboa, Portugal
The underlying architectures of 5G services impose a wide array of requirements on the transport networks of the future. On one hand, edge functions are progressively being offloaded onto data-centers in the cloud, while on the other the data-centers themselves are increasingly more distributed in re-purposed central offices. As a result, transport networks in the metro space face traffic requirements increasing in scale and dynamism. As traffic engineering becomes intertwined with storage and compute resource dimensioning, it is important to put into question which type of metro architectures are able to cost-efficiently address these requirements. This paper presents a comparative analysis of reconfigurable/fixed optical add/drop multiplexer (ROADM/FOADM) and filterless architectures in metro ring scenarios, evaluating how the raw capacity requirements, coupled with the more complex traffic patterns induced by virtual network function placement towards the network edge, respond in terms of scalability and flexibility.

Mirosław Klinkowski
Impact of crosstalk estimation methods on the performance of spectrally and spatially flexible optical networks
M. Klinkowski1 and K. Walkowiak2
1National Institute of Telecommunications, Warsaw, Poland
2Wrocław University of Science and Technology, Poland

We focus on a crosstalk-aware lightpath planning problem in a spectrally and spatially flexible optical network (SS-FON) in which spectral super-channels (SChs) are carried over multi-core fibers (MCFs) and distance-adaptive transmission is considered. The problem concerns establishing lightpath connections for a set of traffic demands in such a way that the inter-core crosstalk (XT) impairment affecting the quality of transmitted signals does not exceed allowable threshold levels. The aim of this work is to compare the methods ensuring required XT levels. In particular, we analyze two basic methods: a) based on worst-case XT and b) using precise XT estimation. Both methods are implemented in a XT-aware routing, spatial mode, and spectrum allocation (RSSA) algorithm, which is applied to solve the planning problem. The obtained numerical results show the impact of considered XT estimation methods on network performance.

Krzysztof Walkowiak
Scalability analysis of spectrally-spatially flexible optical networks with back-to-back regeneration
K. Walkowiak1, M. Klinkowski2, and P. Lechowicz1
1Wroclaw University of Science and Technology, Poland
2National Institute of Telecommunications, Poland
Space division multiplexing (SDM) is perceived as a future solution to overcome the possible capacity crunch problem in optical backbone networks. The main goal of SDM is to use the additional spatial dimension in order to ensure a significant increase in the transmission system capacity. In SDM, optical signals are transmitted in parallel through spatial resources (fibers, cores or modes), thus co-propagating in the same optical fiber structure. In this paper, we focus on a spectrally-spatially flexible optical network (SS-FON) with back- to-back regeneration considering a dynamic traffic scenario. In more detail, for signal regeneration we apply transceivers operating in back-to-back configurations (i.e., with interconnections at the client side). Accordingly, the transmission path is divided into transparent segments and results in a translucent (i.e., regenerated) lightpath. We consider three alternative regeneration scenarios that differ in the way in which dynamic translucent lightpath connections are provisioned. A reference scenario assumes that the use of regenerators is minimized and the modulation conversion is not allowed, two other scenarios apply intentional B2B regeneration. The main goal of this paper is to present a detailed scalability analysis of an SS-FON considering various B2B regeneration scenarios. e assume that the SS-FON uses bundles of single mode fibers with different number of fibers per link. We report and discuss results of extensive numerical experiments run on two representative network topologies with realistic physical assumptions. We focus on the bandwidth blocking probability (BBP) as the main performance metric. In more detail, we report the results of accepted traffic obtained for 1% threshold of BBP, i.e., the maximum traffic that can be provisioned in the network with BBP not greater than 1%, which is a commonly acceptably threshold for BBP. Moreover, we provide a detailed scalability analysis showing performance of SS-FON considering different number of fibers per link and different number of transceivers available in the network.


GOC invited presentations:

Luca Chiaraviglio
Optimal design of 5G networks in rural zones with UAVs, optical rings, solar panels and batteries
L. Chiaraviglio1,2, L. Amorosi2, N. Blefari-Melazzi1,2, P. Dell’Olmo3, C. Natalino4, and P. Monti4
1EE Department, University of Rome Tor Vergata, Italy
2Consorzio Nazionale Interuniversitario per le Telecomunicazioni, Italy
3DSS Department, University of Rome Sapienza, Italy
4KTH Royal Institute of Technology, Sweden
We focus on the problem of designing a 5G network architecture to provide coverage in rural areas. The proposed architecture is composed of 5G Base Stations carried by Unmanned Aerial Vehicles (UAVs), and supported by ground sites interconnected through optical fiber links. We also consider the dimensioning of each site in terms of the number of Solar Panels (SPs) and batteries. We then formulate the problem of cost minimization of the aforementioned architecture, by considering: i) the cost for installing the sites, ii) the costs for installing the SPs and the batteries in each site, iii) the costs for installing the optical fiber links between the installed sites, and iv) the scheduling of the UAVs to serve the rural areas. Our results, obtained over a representative scenario, reveal that the proposed solution is effective in limiting the total costs, while being able to ensure the coverage over the rural areas.

Abhishek Dixit
Models for evaluating power saving techniques in flexible optical access networks
S. Garg and A. Dixit
Bharti School of Telecommunication Technology and Management, Indian Institute of Technology Delhi, New Delhi, India
Increased use of power in telecommunication networks has not only increased the cost of operation but also increased the carbon footprint and the environmental hazards. In this paper, we propose models for evaluating power saving techniques in flexible passive optical access networks. In addition, the power model of their sleep modes are proposed and are extended to analyse the power saving potentials of state-of-art dynamic bandwidth allocation (DBA) algorithms like sleep mode aware (SMA) and hybrid sleep mode aware (HSMA).

Paola Parolari
Long wavelength VCSELs exploitation for low-cost and low-power consumption metro and access networks
P. Parolari, A. Gatto, and P. Boffi
Politecnico di Milano, PoliCom – Dip. Elettronica Informazione e Bioingegneria, Milano, Italy
Long wavelength VCSELs are demonstrated to be able to support metro and access networks in order to achieve low-cost and low-power consumption transceivers. In particular the exploitation of discrete multitone direct modulation allows to achieve high transmission capacities and the availability of widely tuneable MEMS-VCSELs to sustain agility, reconfigurability and colourless features of networks.

Shuaib Siddiqui
Design considerations for an energy-aware SDN-based architecture in 5G EPON nodes
H. Khalili1,2, P. S. Khodashenas1, D. Rincon2, S. Siddiqui1, J. R. Piney2, and S. Sallent1
1i2CAT Foundation, Barcelona, Spain
2Department of Network Engineering, Universitat Politècnica de Catalunya (UPC), Castelldefels, Barcelona, Spain
In the evolution of telecommunication industry towards 5G, Ethernet Passive Optical Networks (EPON) technology, with some unique features such as high capacity, low latency, and minimum cost per bit, positions itself as an interesting option for backhauling solution in the Multi-access Edge Computing (MEC) scenarios. It became evident that the converged optical-radio nodes will play a crucial role on the realization of envisioned 5G connected world. To maximize the benefits of the 5G EPON networks, besides all other challenges, it is essential to address two main issues, i.e. energy efficiency and softwarization. To this end, in this paper, initially we introduce an algorithm that minimizes the energy consumption of EPON networks without imposing additional packet delay. Then we introduce a framework to have an open control layer based on SDN (Software-Defined Networks), able to prepare the EPON backhaul to deal with the 5G applications and services. As a future work, we plan to combine both concepts in an energy-aware SDN controller for 5G EPON nodes.


GOWN invited presentations:

Tibor Berceli
Enhanced capacity of radio over fiber links using polarization multiplexed signal transmission
N. Badraoui and T. Berceli
Department of Broadband Infocommunications and Electromagnetic Theory, Budapest University of Technology and Economics, Hungary

The future vision of integrating back- and front-haul links in 5G mobile networks requires the design of high capacity network transport architecture, enabling flexible management service with high fidelity. This paper presents an approach of using Radio over Fiber technology for 5G back- and front-haul applications. The proposed design was verified by using polarization multiplexing (Pol-Mux) transmission method to investigate the performance and reliability for long-haul transmission. Our simulation results show better performance at high data rate which can significantly increase the system capacity for 5G radio access and core network functions, due to the polarization multiplexing technique in the optical domain. We discuss the major transmission impairments of the RoF system applying the Pol-Mux technique. We analyse the performance of the QAM signal transmission using numerical simulation in single sideband Pol-Mux RoF system. This approach will play a major role for future 5G integrated transport system designs.

Anne-Laure Billabert
Performance analysis of radio over-fiber-based on phase-modulation and direct-detection for the future 5G network
M. Emmaeinna, S. Faci, A.-L. Billabert, A. Kabalan, C. Algani, and M. L. Diakité
CNAM, Paris, France
Access transport network plays a vital role in actual mobile network. Their design considers the need for supporting high data rates, real time services and spectrum efficiency. For future 5G networks, there are more constraints on the access network performances. In this article, we propose a radio-over-fiber transmission scheme based on optical phase modulation for the uplink direction. The analog performances of the link will be studied and then, digital modulated signal transmission over the link is carried out for a complete link performances analysis.

Giannis Giannoulis
Analog radio-over-fiber solutions for 5G communications in the beyond-CPRI era
G. Giannoulis, N. Argyris, N. Iliadis, G. Poulopoulos, K. Kanta, H. Avramopoulos, and D. Apostolopoulos
National Technical University of Athens, Greece

Current research efforts on 5G RAN strongly focus on pico-cells deployment based on mmWave radio, optical/wireless convergence to support massive-MIMO and a cloud-centric operation of BBUs. Industrial and academic institutions concur that it is of great importance to develop evolutional paradigms that ensure the functional combination of the above technologies into a 5G cellular architecture and its associated ecosystems providing new vertical services. This paper aims to explore the role of Analog RoF solutions moving beyond CPRI implementations for future 5G architectures, highlighting the impact of digital-signal-processing to proposed network implementations. Α DSP-assisted IFoF concept to support 60-GHz multi-band wireless connectivity is successfully demonstrated through preliminary experiments showing 12 Gb/s downlink connectivity with centralized processing at BBU side.

Marco Grande
Graphene for optically transparent telecommunication devices
M. Grande, Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, Italy
In this paper we will review the latest achievements in graphene‐based devices devoted to telecommunication applications and will discuss the possibility for new perspectives. Then we will report on design and characterization of radiation elements, operating over a wide operating bandwidth (> 3.5 GHz) simultaneously covering the WiFi, Bluetooth and 5G bands, that exploit highly conductive CVD graphene [1-2].
[1] M. Grande, G. V. Bianco et al., Scientific Reports, 5 (2015) 17083.
[2] M. Grande, G. V. Bianco et al., Optics Express, 24 (2016) 22788‐22795.

Daniel King
A comparative analysis of community developed resource models for the optical transport network: A series of findings from the field
D. King and D. Hutchison
Lancaster University, UK

The TOUCAN and Metro-Haul projects are deploying smart optical metro infrastructure able to support traffic originating from heterogeneous radio access networks, addressing the anticipated capacity increase and its specific characteristics, e.g., mobility, low latency, low jitter etc. This infrastructure requires suitable optical transport models to support a wide variety of services and use cases with special emphasis on services from various industries vertical to the ICT. The comparative analysis discusses the suitability of various community developed resource models and their subsequent strengths and weaknesses when evaluated for the TOUCAN and Metro-Haul projects.

János Ladvánszky
On upper bound for the third order intercept point of mixers
J. Ladvánszky, Ericsson Telecom Hungary, Budapest, Hungary

Christina Lim
Design and planning for fiber-based small cell backhauling
C. Lim, C. Ranaweera, E. Wong, and A. Nirmalathas
Department of Electrical and Electronic Engineering, Melbourne School of Engineering, The University of Melbourne, Australia

With the next generation of wireless technology migrating towards smaller cell deployment in order to cope with the traffic demand, the issues with regards to backhauling has to be carefully considered. To achieve a smooth upgrade and transition, small cells and backhaul infrastructure have to be planned simultaneously to ensure optimal cost and performance can be achieved. In this paper, we review the framework to simultaneously plan the small cell locations in conjunction with the optical fiber backhaul networks to achieve cost optimal solution while meeting the network coverage and capacity requirements.

Carmo Medeiros
Semiconductor laser models suitability to assess laser noise effects on optically generated millimeter wave signals
B. M. Oliveira, P. Almeida, and M. C. R. Medeiros
IT-Instituto de Telecomunicações – Pólo de Coimbra, Departamento de Engenharia Eletrotécnica e de Computadores, Universidade de Coimbra, Portugal

Microwave photonic techniques (MP), such as optical heterodyning of two correlated laser sources upon photo-detection, have been proposed to generate high purity millimeter (mm) wave signals. This approach is particularly suitable for RF frequencies where electronic alternatives are costly and difficult to implement. Additionally, MP allows the efficient remote delivery of the mm-wave signal by transmitting the reference optical signals though low loss high bandwidth optical fiber links. Laser characteristics, such as relative intensity noise and phase noise together with optical fiber characteristics are of key importance in such applications. This paper discusses and compares laser models with different degrees of complexity and assess their suitability for the design of optical heterodyning and delivery of high purity mm-wave signals.

Mehdi Shadaram
A method to increase the capacity of a millimeter wave radio-over-fiber system
M. K. Eghbal1, F. Aminian2, M. Shadaram1
1University of Texas at San Antonio, USA
2Trinity University, One Trinity Place, San Antonio, USA
We propose a W-band wavelength division multiplexed (WDM)-over-optical code division multiple access (OCDMA) radio-over-fiber system operating at various frequencies within the E-band and the performance measurements are presented. The system offers an extended capacity for millimeter wave signals by incorporating optical encoding with WDM technique. The millimeter wave signal is generated in a tandem dual-electrode Mach Zehnder Modulator. Two optical tones, having a frequency difference equal to the millimeter wave frequency of choice are selected from the output spectrum of the tandem modulators. One frequency component is data-modulated and optically encoded while the other tone is kept unmodulated and uncoded. Both optical tones are then transmitted through an optical fiber to the receiver. At the receiver, two tones are heterodyned at a photodiode to generate the millimeter wave signal at the E-band. The performance of the system is measured with software simulation of three channels each carrying six users’ encoded data. The outcome of this study is depicted in bit-error-rate and eye-diagram figures. The best result is achieved for channel three with BER of 10-6 for a received power of 6.9 μW. The obtained results are analyzed for each wavelength channel. Finally, the analysis of the obtained results is presented.

Luis Velasco
Flexible fog computing and telecom architecture for 5G networks
L. Velasco and M. Ruiz
Optical Communications Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
We review a novel, secure, highly distributed and ultra-dense fog computing infrastructure, which can be allocated at the extreme edge of a wired/wireless network for a telecom operator to provide multiple unified, cost-effective and new 5G services, such as Network Function Virtualization (NFV), Mobile Edge Computing (MEC), and services for third parties (e.g., smart cities, vertical industries or Internet of Things (IoT)). The distributed and programmable fog technologies are expected to strengthen the position of the Mobile Network and cloud markets; key benefits are the dynamic deployment of new distributed low-latency services. The architecture consists of three main building blocks: a) a scalable node, that is seamlessly integrated in the telecom infrastructure; b) a controller, focused on service assurance, that is integrated in the management and orchestration architecture of the telecom operator; and c) services running on top of the telecom infrastructure.


LFSRS invited presentations:

Vasily Astratov
Plasmonics and superresolution in microspherical nanoscopy
V. N. Astratov1, A. Brettin1, F. Abolmaali1, L. Poffo2, and A. V. Maslov3
1Department of Physics and Optical Science, Center for Optoelectronics and Optical Communications, University of North Carolina at Charlotte, USA
2UMR FOTON, CNRS, Université de Rennes 1, Lannion, France
3University of Nizhny Novgorod, Russia

It is shown that the resolution in microspherical nanoscopy is increased with decreasing the period of nanoplasmonic arrays used for illumination of nanoscale objects. It is demonstrated that the maximal resolution about λ/6- λ/7, where λ is the wavelength responsible for the image formation, is possible under resonance with localized surface plasmon excitations in nanoplasmonic arrays. Under these conditions, superresolution can be realized without post-imaging processing.  To study the nanoplasmonic contributions to the resolution of nanoscale structures in microspherical nanoscopy, we investigated several combinations of spectral emission peaks positions of nanoscale objects (blue, green, and red fluorescent (FL) nanospheres) with various spectral positions of plasmonic excitations in the Au and Al arrays located in close proximity to nanospheres. It is shown that the contrast of the super-resolved images of nanospheres in a confocal mode is determined by their FL properties. It is demonstrated that the maximal resolution about λ/6 can be obtained under resonance conditions between the emission and localized surface plasmon (LSP) excitation.

Paola Borri
Imaging and tracking single plasmonic nanoparticles in 3D background-free with four-wave mixing interferometry
P. Borri, G. Zoriniants, N. Giannakopoulou, F. Masia, I. Pope, and W. Langbein
Cardiff University, UK

Imaging and tracking single nanoparticles using optical microscopy are powerful techniques with many applications in biology, chemistry, and material sciences. Despite significant advances, imaging single particles in a scattering environment as well as localizing objects with nanometric position precision remains challenging. Applied methods to achieve contrast are dominantly fluorescence based, with fundamental limits in the emitted photon fluxes arising from the excited-state lifetime as well as photobleaching. Here, we show a new four-wave-mixing interferometry technique, whereby single nonfluorescing gold nanoparticles are imaged background-free even inside biological cells, and their position can be determined with nanometric precision in 3D. The technique is also uniquely sensitive to particle asymmetries of only 0.5% ellipticity, corresponding to a single atomic layer of gold, as well as particle orientation. This method opens new ways of unraveling single-particle trafficking within complex 3D architectures.

Shi-Wei Chu
Unlimited resolution of saturated excitation microscopy with unusual nonlinear responses
Shi-Wei Chu, National Taiwan University, Taipei, Taiwan
Super-resolution imaging has made significant impacts in various biological fields in the last decade. However, the resolution improvement is difficult to sustain in a biological tissue due to intrinsic scattering/aberration. Here we demonstrate that saturated excitation (SAX) microscopy achieves at least 3-fold resolution enhancement in a highly scattering tissue throughout 200um depth, only limited by the objective working distance. Combined with unusual nonlinear responses, we show theoretically that SAX microscopy may provide resolution down to lambda/50, paving the way toward deep-tissue super-resolution applications.

Katsumasa Fujita
Surpassing the diffraction limit in Raman microscopy
K. Fujita, Osaka University, Japan
Super-resolution techniques are widely available in fluorescence microscopy but still have not been well explored in Raman microscopy. In our research, we implemented the structured illumination technique in line-illumination Raman microscopy to achieve both high spatial- and temporal-resolutions in hyperspectral Raman imaging. We also examined the use of nonlinear excitation of coherent Raman scattering for improving the spatial resolution. Inducing saturation in vibrational excitation, highly-nonlinear coherent Raman signal localizes within a laser spot. We have confirmed the improvement of spatial resolution in CARS and SRS imaging. We also confirmed that the technique can also improve the spectral resolution over the bandwidth of the excitation laser.

Pietro Gucciardi
In-liquid SERS detection of biomolecules by optical aggregation of plasmonic nanoparticles
P. G. Gucciardi, CNR – Istituto per i Processi Chimico-Fisici, Messina, Italy
In this talk I will review different strategies for SERS sensing in liquid environment. SERS-active hot spots are obtained through the aggregation of metal nanoparticles in a solutions containing the target analyte. These new approaches offer several advantages with respect to conventional “dry” SERS methods in terms of high sensitivity, reproducibility, ease of use and practical applications to biomolecular detection. Aggregation can be achieved by simple evaporation or, in a more controlled manner, using chemical agents or light-induced effects, among which thermophoretic effects and optical forces. Optical forces, in particular, enable the controlled manipulation, trapping and accumulation of metal particles in a contactless and chemically free way, which provides a unique advantage with respect to other routes. Exploiting the mechanical interaction between light and matter, it is in fact possible to trap or push metal nanoparticles in the spot of a tightly focused laser beam in a very simple way, creating 2D or 3D aggregates that can be used for high sensitivity SERS spectroscopy in liquid environment. These new strategies have already allowed scientists to achieve single molecule sensitivity on dye molecules, and sensitivities in the nM or even in the pM range in the detection of biomolecules. A strong impact is expected for the development of future integrated analytical platforms such as in ‘lab-on-chip’ devices, finalized to the label-free detection of pollutants, chemical agents, explosives and biomolecules with ultra-low sensitivity. Specificity can potentially be added to these methodologies by using NPs functionalized with aptamers or antibodies capable to capture the target biomolecules in liquid, thus enabling specific detection of pathology biomarkers in liquid environment.

Mikko Huttunen
Label-free super-resolution microscopy with coherent nonlinear structured-illumination
M. J. Huttunen, A. Abbas, J. Upham, and R. W. Boyd
Tampere University of Technology, Finland

Conventional structured-illumination microscopy provides up to a two-fold improvement in the achievable lateral resolution by spatially modulating the intensity profile of the illumination beam. However, the conventional structured-illumination scheme cannot be directly combined with label-free nonlinear coherent imaging modalities. Here we propose a way to overcome this limitation by generalizing the concept of structured-illumination microscopy to coherent nonlinear wide-field modalities, where the phase of the illumination beam is spatially modulated while interferometrically measuring the complex-valued scattered field. We demonstrate numerically how by using nonlinear processes of second-harmonic generation and third-harmonic generation up to four- and six-fold increases in the lateral resolution are possible, respectively. Since coherent nonlinear imaging modalities do not require use of labels, the demonstrated approach provides possibilities for biomedical applications benefitting from minimal sample preparation.

Alessio Lugnan
Integrated dielectric scatterers for speeding up classification of cell diffraction patterns
A. Lugnan1,2, J. Dambre3, and P. Bienstman1,2
1Photonics Research Group, UGent – imec, Belgium
2Center for Nano- and Biophotonics (NB-Photonics), Ghent University, Belgium
3IDLab, UGent - imec, Belgium

The computational power required to classify diffraction pattern images of biological cells is a major limit to the implementation of fast label-free cell sorting based on digital holographic microscopy. This work aims to demonstrate that the performance of a computationally cheap linear classifier can be significantly improved by the scattering action of a simple collection of integrated dielectric pillars. FDTD simulations show that the error of cell classification based on nucleus size can be decreased by a factor 5 when dielectric scatterers are employed and cells are made to flow in a suitable optical cavity.

Cristiana Grigorescu
Nanoplasmonics and surface enhanced Raman scattering for in vivo label free diagnosis in oncologic surgery
C.E.A. Grigorescu1, M.I. Rusu1, C. R. Stefan (Iordanescu)1, L.O. Scoicaru1, C. Rizea2, B. A. Vitalaru3, A. Tonetto4, R. Notonier4
1National Institute of Research and Development for Optoelectronics INOE 2000, Magurele, Romania
2ROXY VETERINARY S.R.L. Magurele, Romania
3Faculty of Veterinary Medicine-University of Agronomic Sciences and Veterinary Medicine, Bucharest, Romania
4Aix-Marseille Université´, Centrale Marseille, CNRS, Federation Sciences Chimiques Marseille (FR 1739) – PRATIM, Marseille, France

Surface-enhanced Raman scattering (SERS) has been for more than 40 years the most striking effect related to optical phenomena in nanostructured metal systems owing to the spectacular amplification of the Raman signal trough electromagnetic and chemical fields. The capability of some one-electron metals e.g. silver, gold, copper to generate surface plasmons that hold the energy of light concentrated on the nanoscale has found a wide range of applications in various fields like for instance physical and chemical research and biomedicine. Our work is devoted to the study of silver and gold nanostructured surfaces used as SERS substrates for in vivo label free diagnosis in oncologic surgery. We aim at shedding some light on the mechanisms competing for the signal enhancement in the particular case of tissue/bare nanostructured metal interface when using the 632nm Raman excitation wavelength. A choice between silver and gold as good plasmonic metals for our purpose can be done starting from ellipsometry measurements on the nanostructured surfaces we have produced.

Radu Malureanu
High aspect plasmonic nanotrench structures as sensors in the near- and mid-IR frequency range
E. Shkondin, T. Repän, R. Malureanu, A. V. Lavrinenko, and O. Takayama
Department of Photonics Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark

Titanium nitride (TiN) and aluminum-doped zinc oxide (AZO) high-aspect trench structures are fabricated using a combination of deep reactive ion etching and atomic layer deposition. These structures may be used as sensors in the near-infrared (IR, 820 – 900 nm wavelength range) and mid-IR (8 μm wavelength), respectively. We show that the refractive index sensitivity reached values up to 430 nm/RIU for TiN trenches in the near-IR region and enhanced sensitivity of molecules in AZO trenches for mid-IR wavelengths.

Paul Montgomery
Microsphere-assisted microscopy: From 2D to 3D super-resolution imaging
P. Montgomery, S. Perrin, and S. Lecler
Engineering Science, Computer Science and Imaging Laboratory (ICube), University of Strasbourg-CNRS, France
Here we present a new unlabelled far field optical imaging technique using microspheres to enhance the lateral resolution in optical microscopy. Both 2D and 3D super-resolution imaging using microspheres are considered, providing results of 2D and 3D imaging of surfaces with vastly improved lateral resolution and nanometric axial resolution for the 3D mode. Results are shown on narrow etched gratings in Si, nanotextured stainless steel surfaces and Ag nanodots.  The main results demonstrate improvements of up to 3 times in lateral resolution, showing details of 300 nm for a microscope that would normally have a limit of 850 nm. Microsphere-assisted microscopy is a major new type of far field optical microscopy with great potential for high resolution imaging, characterisation and nanometrology in materials science and the biological sciences.

Arno Rauschenbeutel
Systematic wavelength-scale errors in the localization of nanoscale emitters due to spin-orbit coupling of light
J. Volz1, S. Walser1, G. Araneda2, Y. Colombe2, D. B. Higginbottom2,3, R. Blatt2,4, and A. Rauschenbeutel1,5
1Vienna Center for Quantum Science and Technology, Atominstitut,TU Wien, Vienna, Austria
2Institut für Experimentalphysik, Universität Innsbruck, Austria
3Centre for Quantum Computation and Communication Technology, Research School of Physics and Engineering, The Australian National University, Canberra, Australia
4IQOQI Innsbruck, Österreichische Akademie der Wissenschaften, Innsbruck, Austria
5Institut für Physik, Humboldt-Universität zu Berlin, Germany

The precise determination of the position of sub-wavelength scale emitters using far-field optical imaging techniques is of utmost importance for a wide range of applications in medicine, biology, astronomy, and physics. Modern super-resolution techniques allow one to determine the positions of individual emitters in principle with arbitrary precision. In recent years, different technical effects have been discussed that, in such applications, can give rise to an apparent shift of the emitter’s position of a few ten nanometres. In my talk, I will demonstrate a novel and fundamental physical effect that leads to systematic, wavelength-scale position errors when imaging elliptically polarized emitters. The effect stems from the orbital angular momentum carried by the light field due to spin-orbit coupling. By imaging a single trapped atom as well as a single gold nanoparticle, we demonstrate that this effect leads to shifts between the emitters' measured and actual positions which are comparable to the optical wavelength.

Bertrand Simon
Isotropic-resolution tomographic diffractive microscopy
B. Simon1, M. Debailleul2, M. Houkal3, C. Ecoffet3, J. Bailleul2, J. Lambert2, A. Spangenberg3, Hui Liu4, O. Soppera3, and O. Haeberlé2
1Institut d’Optique – Graduate School, IOGS - Laboratoire Photonique, Numérique et Nanosciences LP2N - JRU 5298, Bordeaux, France
2Institut de Recherche en Informatique, Automatique, Automatique et Signal IRIMAS – EA7499 Université de Haute-Alsace (UHA), France
3Institut de Science des Matériaux de Mulhouse IS2M, Université de Haute-Alsace (UHA), CNRS UMR 7361, France
4Institut de Génétique et de Biologie Moléculaire et Cellulaire IGBMC, Université de Strasbourg (UniStra), CNRS UMR 7104, INSERM U964, France

Microscopy techniques based on recording of the optical field diffracted by the specimen, in amplitude and phase, like Digital Holographic Microscopy (DHM) have been a growing research topic in recent years. Tomographic acquisitions are possible if one is able to record information, while controlling variations of the specimen illumination. Classical approaches consider either illumination variation, simple to implement, but suffering from the classical “missing cone” problem, or sample rotation, delivering images with quasi-isotropic, but lower resolution. We have developed an original-, combined tomographic diffractive microscope setup, making use of specimen rotation as well as illumination rotation, which is able to deliver images with an almost isotropic resolution better than 200 nm.


MARS invited presentations:

Germán Arévalo
Techno-economics for optimal deployment of optical fronthauling for 5G in large urban areas
G. Arévalo1, R. Gaudino2, and M. Tipan1
1Universidad Politécnica Salesiana, Ecuador
2Politècnico di Torino, Italy

In this work we employ our previously published Optimal Topology Search (OTS) algorithm to study, from a techno-economic point of view, the optimal deployment of 5G networks in large urban areas, focusing on the allocation of the remote radio heads and their correspondent low-cost optical fronthauling topologies. We compare the costs of deploying 5G networks based on traditional CPRI fronthauling with a DSP-assisted fronthauling solution. Results show that the DSP-assisted solution provides effective connectivity from the Central Offices up to the remote radio heads at a lower cost in comparison with the CPRI-fronthauling deployment.

Marco Forzati
The social-economic impact of fiber broadband penetration: a hype or a reality?
Jie Li and M. Forzati
Networking and Transmission Laboratory, RISE Acreo, Kista, Sweden

The social-economic impact of broadband penetration has been studied extensively. The general consensus is that basic broadband penetration (from none or upgraded from 256 kbps to the order of 2-6 Mbps) indeed has positive impact on economic growth and performance in terms of e.g. GDP and employment. Nevertheless, studies on the social-economic impact of high-speed broadband access (20-30 Mbps and beyond) are far more controversial showing a mixed picture. In this paper, we investigated fiber broadband access impact on the employment rate, population evolution, reduced driving distance per capita and new company registrations at the municipality level in Sweden using multiple regression analysis. Based on the availability of historical fiber network deployment data, analyses can be carried out by regressing current values of social-economic indicators under study on the fiber penetration levels 4 years earlier, hence reverse causality in the regression analyses can be tackled effectively. Our results show that, given all the other significant factors remain the same and with at least 90% confidence interval, 10% increase of fiber broadband penetration would result in 0.17% population increase, 0.32% employment rate enhancement, 28.7 km reduced driving distance per capita per year, and one new company among 17857 inhabitants.

Jordane Thouras
Introduction of 12 cores optical amplifiers in optical transport network: Performance study and economic impact
J. Thouras1, E. Pincemin1, D. Amar2, P. Gravey2, M. Morvan2, and M.-L. Moulinard2
1Orange Labs, Lannion, France
2IMT Atlantique, Plouzané, France

We investigate the techno-economic impact of the introduction of 12-core Multicore Erbium-Ytterbium doped fiber amplifiers (MC-EYDFA) in optical transport networks. We evaluate the CAPEX gain involved by their utilization as line amplifiers and the energy consumption reduction induced by the pump sharing between the 12 cores. We also evaluate the impact of the inter-core crosstalk in the MC-EYDFA on the quality of transmission through the use of the Gaussian noise model.


MWP invited presentations:

Mario Armenise
Integrated microphotonic tunable delay lines for beam steering in phased array antennas
C. Ciminelli, G. Brunetti, D. Conteduca, F. Dell’Olio, and M. N. Armenise
Optoelectronics Laboratory, Politecnico di Bari, Italy

Beam steering in phased array antennas for some demanding terrestrial and space applications needs ultra-wide band true-time tunable delay lines preventing the beam squint phenomenon. Recent advances in the field of integrated microphotonics have allowed the demonstration of compact chip-scale delay lines with fast and low-power tuning mechanisms. For the tuning, several approaches have been theoretically and experimentally investigated and among them, very promising results have been obtained by using graphene in resonant delay lines based on the slow light effect. In this paper, after a brief review on resonant microphotonic tunable delay lines, some selected recent results on an ultra-compact graphene-based optical delay line including a silicon Bragg grating, are proposed.

Guillermo Carpintero
Modulation transparent wireless data link using photonic-based transmitter and envelope detector
G. Carpintero, R. Guzman, A. Rivera, L.-E. García, H. Lamela, and D. Segovia
Carlos III University, Madrid, Spain

In this paper, we demonstrate a photonic-enabled wireless data transmission, operating at 73 GHz carrier wave, generated by optical heterodyne technique. Through modulation in the photonic domain, using a 10 GHz bandwidth optical modulator, we show the transmission of two different types of signals. On one hand, a 1080 HDMI video signal coded in 2.970 Gbit/s OOK signal from a HDTV camera, and on the other, a 4K video signal coded as an DVB-T 16-QAM-OFDM signal with error below FEC-limit (BER<10-3). In both scenarios, successful real-time video transmission is achieved.

Robert Minasian
Microwave photonic advances for photonic signal processing
R. Minasian and Xiaoke Yi
University of Sydney, Australia

Microwave photonics offers the prospect of overcoming a range of challenging problems in the processing of signals. Its intrinsic advantages of high time-bandwidth product and immunity to electromagnetic interference (EMI) have led to diverse applications in the microwave and sensing fields. Future systems require wideband frequency shifting capabilities to millimetre wave frequencies with low spurious generation and with tunable capabilities, which is a difficult task using conventional approaches. An all-optical frequency shifter based on stimulated Brillouin scattering (SBS) is described. The SBS principle is highly attractive because SBS is all-optical, which means that it can operate and be tuned over extremely wide microwave and millimetre-wave bandwidths. The structure does not involve any electrical components and uses normal Mach Zehnder modulators, which can have 100 GHz bandwidth, hence it enables very high frequency shifts to be realised well into the millimetre wave frequency range. Experimental results demonstrate a 20 GHz frequency shift with 25 dB signal-to-noise ratio, as well as a widely tunable frequency shifting operation. Also, an integrated photonic sensor based on a microwave photonic optoelectronic oscillator (OEO) with an on-chip sensing probe that is capable of realizing highly sensitive and high-resolution optical sensing is presented. The key component is an integrated silicon-on-insulator (SOI) based microring resonator which is used to implement a microwave photonic bandpass filter to effectively suppress the side modes of the OEO, thus generating a peak RF signal that maps the detected optical change into a resulting shift in the oscillating frequency. Due to the thermo-optic effect, the refractive index of the SOI ring changes with temperature, moreover the high thermal coefficient of the SOI based microring resonator that functions as an on-chip sensing probe causes a small temperature change to generate a large RF frequency shift in the OEO output which can be measured with very high resolution. Experimental results demonstrate a linear relationship between the temperature change and RF frequency shift, with the microwave photonic OEO frequency varying between 5.5 – 18 GHz, thus achieving an ultra-high sensitivity of 7.7 GHz/°C. The compact and nanoscale nature of the optical microring notch filter makes it ideal to be used as a nanochip sensor probe element that can be easily integrated into any measuring device, and which also enables point sensing.

Salvador Sales
Generation of mmWave 5G signals using microwave photonics
D. Perez-Galacho, V. Nacher-Castellet, and S. Sales
ITEAM research institute, Universitat Politècnica de València, Spain

Bandwidth constraints is, nowadays, a mayor problem in the implementation of next generation 5G networks. In order to cope with increasing bandwidth demands, the use of the millimeter-wave (mmWave) spectrum, together with Radio over Fiber (RoF) technology has been proposed. In this work, we will present our recent advances in the generation of mmWave signals for 5G using Microwave Photonics.

Christos Tsokos
Performance analysis of analog optical link array with optical Blass matrix beamformer for multi-beam operation
C. Tsokos1, P. Groumas1,2, E. Mylonas1, V. Katopodis1, L. Gounaridis1, H. Avramopoulos1, and Ch. Kouloumentas1,2
1National Technical University of Athens, Greece
2Optagon Photonics, Athens, Greece

An optical beamforming network (OBFN) based on an optical M×N Blass matrix is capable of simultaneously steering M-beams at different angles by feeding an antenna with N antenna elements with appropriate excitation signals. Each node of the Blass matrix comprises a Mach-Zehnder interferometer (MZI) and a subsequent phase shifter. The configuration of the OBFN relies on the proper tuning of the coupling coefficients of the MZIs and the induced phase shift by the phase shifters, with respect to the number of the beams, the corresponding steering angles and the degree of the side lobe suppression. We present the required optical techniques for the use of a Blass matrix and we assess its performance through simulation studies. To this end, an analog optical link array is deployed, including a laser source, an array of electro-absorption modulators (EAMs), band-pass filters and photodetectors. Optical single-side band signals carrying microwaves with 28.5 GHz carrier and quadrature amplitude modulation up to 64-QAM, are used as input to the OBFN. The output signals are detected by the photodetector array and are transmitted by a linear multi-element antenna at the selected steering angles. The evaluation of the OBFN is performed through the calculation of the bit-error-rate (BER) of the received signals at the corresponding observation angles in the case of different modulation and beamforming parameters.

Borja Vidal Rodríguez
Photonic-assisted G-band wireless links for 5G backhaul
B. Vidal Rodríguez, Nanophotonics Technology Center, Universitat Politècnica de Valencia, Spain
Mobile networks face a strong pressure to provide ubiquitous connectivity with increasing data bitrates. High cell densification is the natural evolution for 5G networks to reach these goals. This requires a high density backhaul network. The envisaged traffic demands require bandwidths that are not available in the microwave region. The G-band (230-330 GHz) in the sub-THz region offers very large continuous and unregulated bandwidth that can be exploited for 5G backhauling. The flexibility and bandwidth of fibre optic technology, which can be easily integrated in telecom core networks, can be employed in the development of sub-THz wireless networks in combination with other technologies such as solid state and vacuum electronics. This combination of different technologies is the strategy pursued in the European Project ULTRAWAVE. Here, the potential of photonics to assist in the deployment of wireless backhaul networks for 5G networks in the G-band is reviewed.


NAON invited presentations:

Aimi Abass
Tailoring disordered structures for light management
A. Abass1, S. Nanz2, P. M. Piechulla3, A. Sprafke3, R. B. Wehrspohn3,4, and C. Rockstuhl1,2
1Institute of Nanotechnology, Karlsruhe Institute of Technology, Germany
2Institute of Theoretical Solid State Physics, Karlsruhe Institute of Technology, Germany
3Institute of Physics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
4Fraunhofer Institute for Microstructure of Materials and Systems, Halle (Saale), Germany

In the efforts to enhance absorption in thin film solar cells, a plethora of scattering nanostructures and surface textures to enhance light incoupling and light trapping have been explored. One consistent finding in many different studies is the fact that employing disorder can be beneficial by virtue of inducing a more broadband response. Having disorder populates the Fourier spectrum of the geometry, which in turn leads to more available scattering pathways into the absorber medium for light over an extended spectral domain. However, not all disordered structures are equivalent. Not just the availability, the scattering strength to the different pathways is also important. Disorder may also enhance light scattering within the escape cone and weaken resonant optical responses resulting in less absorption enhancement. Therefore, obtaining the most out of introducing disorder requires care and remains a major design challenge due to huge computational costs in numerically addressing the problem. Here, we give an overview of our recent efforts in tackling these challenges. We present an analytical inverse modeling formalism to deduce optimum surface textures for light trapping purposes and beyond, even with incommensurable components. We show how the inverse problem can be formulated as coupled multivariate polynomial equations of the surface texture Fourier amplitudes. We further present a bottom-up large-area-compatible fabrication strategy for disordered surface textures using nanospheres of different sizes as building blocks.

Alicja Anuszkiewicz
Structured light in optical components with arbitrary index distribution
A. Anuszkiewicz1,2, K. Świtkowski3,4, A. Filipkowski1,2, J. Lisowska1,2, D. Pysz1, R. Stępień1, W. Królikowski4,5, and R. Buczyński1,2
1Glass Department, Institute of Electronic Materials Technology, Warsaw, Poland
2Faculty of Physics, University of Warsaw, Poland
3Faculty of Physics, Warsaw University of Technology, Poland
4Science Program, Texas A&M University at Qatar, Doha, Qatar
5Laser Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, Australia

The ability in shaping the refractive index profile of optical component holds a key to fully play with its optical properties and future application. We present recently proposed approach for the development of optical components with arbitrary index distribution obtained with nanostructurization method. The method is based on effective medium theory and applied for distribution of two types of subwavelength glass rods in fibrous component. Arbitrary index profile not limited to the circular symmetry, as it is i.e. for optical fibers, is a consequence of refractive index difference between the glasses and designed glass rods distribution. We present the recent progress in development of nanostructured optical components such as GRIN lenses, axicons and phase masks. We proved that with use of nanostructured phase element it is possible to produce structured light beam, i.e. supporting optical singularity as optical vortex. We show the nanostructurization approach allow development of arbitrary refractive index distribution since a perfect match between theoretically analysed, designed and measured optical properties of fabricated structures is obtained.

Louise Bradley
Nonradiative energy transfer and photocurrent enhancements in hybrid quantum dot-MoS2 devices
J. J. Gough, N. McEvoy, M. O’Brien, A. P. Bell, J. McManus, D. McCloskey, J. B. Boland, J. N. Coleman, G. S. Duesberg, and A. L. Bradley
Department of Physics and CRANN, Trinity College Dublin, College Green, Ireland

The energy transfer mechanism leading to highly efficient nonradiative energy transfer (NRET) from quantum dots (QDs) to monolayer MoS2 devices has been investigated via a spectral dependence study. The spectral dependence of the NRET from three spectrally separated QD ensembles to monolayer MoS2 devices reveals that the trends in NRET rates follow the trends in the spectral overlap between the QD emission and MoS2 absorption spectra, thus verifying that the mechanism for the energy transfer is Förster-type NRET. Furthermore, the dependence of the photocurrent enhancement on the MoS2 film properties is also explored.

Péter Dombi
Ultrafast nanooptical near-field probing with photoelectrons
P. Dombi, Wigner Research Centre for Physics, Budapest, Hungary
Probing nanooptical near-fields is a major challenge in plasmonics. I will introduce a new experimental method utilizing ultrafast photoemission from plasmonic nanostructures that is capable of probing the maximum nanoplasmonic field enhancement in any metallic surface environment. Directly measured field enhancement values for various samples are in good agreement with detailed finite-difference time-domain simulations. Our results [P. Rácz et al., Nano Lett. 17, 1181 (2017)] establish ultrafast plasmonic photoelectrons as versatile probes for nanoplasmonic near-fields and deliver important insight on plasmon-plasmon coupling, as well.

Ramon Herrero
Stabilization of broad area semiconductor amplifiers and lasers by double modulation of pump and refractive index
W. W. Ahmed1, S. Kumar1, J. Medina1, M. Botey1, R. Herrero1, and K. Staliunas2
1Departament de Física, Universitat Politècnica de Catalunya, Spain
2Institució Catalana de Reserca i Estudis Avançats (ICREA), Spain

Broad area semiconductor amplifiers and lasers display instability of the homogeneous state typically related with self-focusing nonlinearities, inducing multi-transverse mode operation and filamentation that deteriorates the beam quality. We show that the emission of these amplifiers and lasers can be efficiently stabilized by introducing simultaneous modulations of pump and refractive index in transverse and longitudinal directions. The pattern forming instabilities are efficiently suppressed even for the case of large linewidth enhancement factors by the intertwinement between both inphase modulations leading to stable beams.

Włodzimierz Nakwaski
Quantum-cascade vertical-cavity surface-emitting laser (QC-VCSEL)
W. Nakwaski, M. Dems, R. P. Sarzała, S. Grzempa, and T. Czyszanowski
Photonics Group, Institute of Physics, Lodz University of Technology, Poland

The first semiconductor lasers have been manufactured as edge-emitting lasers (EELs). They emit radiation of relatively high power but their simultaneous excitation of many longitudinal modes and extremely divergent output beam exhibiting astigmatism are their most crucial disadvantages. Vertical-cavity surface-emitting lasers (VCSELs), on the other hand, exhibit many advantages: they inherently emit single longitudinal-mode radiation, their emission beam is very narrow and without astigmatism, it is possible to test quality of VCSEL structures before any processing, which reduces their manufacturing costs. But their possible emission band depends on discovering matching semiconductor materials, i.e. semiconductors of suitable energy gaps and creating structures close to the ideal lattice-matched ones. Intraband emission of quantum-cascade (QC) lasers, on the other hand, does not depend on used semiconductors, they may be designed for required wavelengths by a change of parameters of their quantum wells (QWs), in which emission takes place as a result of transitions between QW levels. But QC lasers exhibit also the above disadvantages of EEL lasers. It is well known that radiation of standard VCSELs cannot be used to stimulate laser emission in QC structures because the vector of their electrical field does not have a required perpendicular component. However, let us consider a completely new quantum-cascade VCSEL structure (QC VCSEL) with a quantum-cascade embedded within its sub-wavelength high-contrast-grating (HCG) mirror. Then, in these new lasers, the transverse-magnetic (TM) radiation of such a required perpendicular polarization is induced. Therefore the above QC VCSELs with the above sub-wavelength HCG laser mirror seem to be expected structures of new semiconductor lasers, structures exhibiting all advantages of both VCSELs and QC lasers without their drawbacks. Physical analysis of optical, thermal and electrical phenomena taking place within possible structures of QC VCSELs and leading to designing their most appropriate configuration is a subject of proposed research.

Masaya Notomi
Femto-farad optoelectronic coupling and low-latency nanophotonic computing
M. Notomi1,2, K. Nozaki1, S. Kita1, and A. Shinya1
1Nanophotonics Center, NTT Basic Research Laboratories, Atsugi, Japan
2Department of Physics, Tokyo Institute of Technology, Japan

We demonstrate that the capacitance of OE/EO conversion devices, such as photo-detectors and electro-optic modulators, can be reduced down to a fF level by use of photonic crystals. This enables us to drastically reduce the energy efficiency of OE/EO conversion. We show that on-chip high-speed photo-receivers can be operated without any electrical power, and  pseudo-all-optical-nonlinear devices can be realized by a combination of a fF photodetector and a fF electro-optic modulator.  Integrated nanophotonics technologies, including those fF-optoelectronic devices, will enable optical pass-gate logic circuits for low-latency optical computation. We present our novel designs for various examples including optical full adder circuits. In addition, we show linear optic gates for logic functions which enable extremely small latency.

Mauro Pereira
Efficient algorithms for optical properties of short period semiconductor superlattices
M. F. Pereira, Department of Condensed Matter Theory, Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
Semiconductor superlattices (SSLs) are ideal systems to study quantum transport and optics under controlled conditions and recent research on frequency multiplication [1, 2] have further highlighted their potential for the GHz-THz range. This talk will deliver a review of a set of analytical equations for both luminescence and absorption of SSLs, that have proven efficient to describe dilute semiconductors and which can be a powerful tool for superlattices and other effective three dimensional materials treated with the anisotropic medium approach [2-5], which are useful from the terahertz and mid infrared (TERA-MIR)  to the near visible ranges  [5, 6].
[1] M.F. Pereira et al, Phys. Rev. B 96, 045306 (2017).
[2] M.F. Pereira et al, J. Nanophoton. 11 (4), 046022 (2017).
[3] M.F. Pereira, Opt. Quant. Electron. 47, 815 (2015).
[4] C.I. Oriaku and M.F. Pereira, J. Opt. Soc. Am. B 34, 321 (2017).
[5] M.F. Pereira, Materials 11, 2 (2018).
[6] M.F. Pereira and I.A. Faragai, Optics Express 22 (3), 3439 (2014).

Ana Quirce
VCSEL-based optical frequency combs: study of its polarization dynamics under gain switching and polarization selective optical injection locking
A. Quirce1, C. de Dios2, A. Valle3, E. Prior2, L. Pesquera3, K. Panajotov1,4, J. Palací5, P. Meissner6, and P. Acedo2
1Vrije Universiteit Brussel, Brussels Photonics B-PHOT, Brussels, Belgium
2University Carlos III, Madrid, Spain
3Instituto de Física de Cantabria (CSIC-University of Cantabria), Santander, Spain
4Institute of Solid State Physics, Sofia, Bulgaria
5Luz Wavelabs S.L. Leganés, Spain
6Technische Universität Darmstadt, Germany

First, we report on a theoretical study of the polarization dynamics of a 1550 nm Vertical-Cavity Surface-Emitting Laser (VCSEL) subject to large amplitude gain switching (GS) modulation in order to get optical frequency combs (OFC). Our results show that thanks to the generation of two orthogonal linearly polarized combs the resulting overall optical frequency comb is much wider that the one of the main polarization. The theoretical dependences of the two combs on the amplitude, frequency modulation and linear dichroism are also analysed. Our simulations are in good agreement with previous experiments already reported in the literature. Next, we study experimentally the polarization frequency comb dynamics of gain-switched VCSEL under parallel, orthogonal and combined optical injection locking (OIL). When parallel OIL is applied to the GS-VCSEL, the parallel comb is only affected at high OIL ratios and the orthogonal comb is enhanced improving the symmetry of the overall comb. For orthogonal OIL, the overall comb is narrower and dominated by the orthogonal comb as the quality of the parallel comb is quickly degraded. For a combined optical injection, the quality of the total comb in terms of span and flatness improves. Remarkably, a 10% wider frequency comb is obtained in this case. Period doubling is observed for the three types of OIL.

Judy Rorison
Spin-orbit interaction and phonon-mediated spin dynamics in quantum dots
M. Vaughan and J.M. Rorison
Department of Electrical and Electronic Engineering, University of Bristol, UK
Spin effects in III-V semiconductor quantum dot devices are being exploited in both ‘classical’ photonic devices (such as spin VCSELs and as an additional label in photonic communication systems) and in classical photonic devices. The modelling formalisms for the two regimes are often very different due to the high temperature (room temperature) regime of the former and the low temperature (milli-Kelvin) regime of the latter. In this talk we unite the two approaches into a simpler formalism and investigate the similarities.  Model expressions for the spin-orbit interaction (SOI) in a quantum dot are obtained. The resulting form does not neglect cubic terms and allows for a generalized structural inversion asymmetry. We also obtain analytical expressions for the coupling between states for the electron-phonon interaction and use these to derive spin-relaxation rates, which are found to be qualitatively similar to those derived elsewhere in the literature. We find that, due to the inclusion of cubic terms, the Dresselhaus contribution to the ground state spin relaxation disappears for spherical dots. A comparison with previous theory and existing experimental results shows good agreement thereby presenting a clear analytical formalism for future developments. Comparative calculations for potential materials are presented.

Michael Scalora
Spin-orbit interaction and phonon-mediated spin dynamics in quantum dots
M. Scalora, M.A. Vincenti, D. de Ceglia, N. Akozbek, M. J. Bloemer, C. De Angelis, J. W. Haus, R. Vilaseca, J. Trull, and C. Cojocaru
Charles M. Bowden Research Facility, AMRDEC, US Army RDECOM, USA

We present a study of linear and nonlinear optical effects that occur when light interacts with metallic surfaces and generic structures with nanometer-scale features. Our model and calculations suggest that the nonlinear optical analysis of metals, conductive oxides, nano-antennas and meta-surfaces, etc. should always be performed by including nonlocal effects (viscosity and pressure); linear and nonlinear contributions of bound (inner-core) electrons to the dielectric constant; linear and nonlinear quantum tunneling currents if gaps between nanoparticle is nanometer and sub nanometer size; and conditions generally reflective of discontinuous free electron densities, such as may occur at the surface of a metal or in transition regions between a metal and a conductive oxide. For this purpose we will use a modified hydrodynamic model to re-evaluate harmonic generation (SHG and THG) from a gold mirror, and from a gold mirror covered with a conductive oxide like ITO, where epsilon-near-zero conditions may be found and exploited.

Oksana Shramkova
Localized photonic jets generated by step-like dielectric microstructures
O. Shramkova, V. Drazic, M. Damghanian, A. Boriskin, V. Allié, and L. Blondé
Technicolor R&D France, Rennes, France

In this contribution we reveal how the step-like topology of microstructure can contribute to the formation of a single high-intensity nano-jet beam located on the axis of symmetry of the system. We investigate the dependence of generated beam on the step size, shape and material.

Ganapathi Subramania
Photonic topological structures at optical frequencies
G. Subramania , Sandia National Laboratories, Albuquerque, USA
Topological photonic structures possess topologically protected photonic modes that can propagate unidirectionally without scattering and can exhibit extreme photonic density of states (PDOS). These properties can provide new functionalities in nanophotonics much like those predicted for electronic systems. Such properties can be transformative for quantum information processing applications such as single photon transport and optical communications. There has been a growing interest in enabling such properties at optical frequencies and on chip-scale relevant to practical applications of such phenomena. We present recent work towards the goal of optical frequency chip-scale nanophotonic structures with topological properties. We will discuss implementation and measurement of topological photonic behavior in such structures fabricated in semiconductor based systems (e.g. Si, GaAs and GaN).

Shumin Wang
Progress on III-V-Bi alloys and light emitting devices
Shumin Wang1,2,3, Li Yue1,3, Lijuan Wang1,3,4, Yanchao Zhang1,3,5, Chang Wang1,3,5, Xiaolei Zhang1,3,5, Chaodan Chi1,3,4, Hao Liang1,3,4, Xiaoyan Wu1, Juanjuan Liu1,3,4, Wenwu Pan1, Chunfang Cao3, and Yaoyao Li1,3
1Key Laboratory of Terahertz Solid-State Technology, CAS, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, China
2Department of Microtechnology and Nanoscience, Chalmers University of Technology, Goteborg, Sweden
3State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, China
4University of Chinese Academy of Sciences, Beijing, China
5School of Physical Science and Technology, ShanghaiTech University, Shanghai, China

In this invited talk, we will present some recent progresses on epitaxial growth of III-V-Bi alloys and light emitting devices. Aluminum containing bismides including AlAsBi and AlSbBi have been epitaxially grown for the first time and their physical properties will be reported. New designs of using delta-doping in quantum wells and type-II quantum wells are investigated to effectively extend light emission wavelength. Finally, GaAs and InP based light emitting diode and laser diodes will be presented.


NetOrch invited presentations:

Ramon Casellas
Metro-Haul: SDN control and orchestration of disaggregated optical networks with model-driven development
R. Casellas, R. Martínez, R. Vilalta, and R. Muñoz
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels (Barcelona), Spain

SDN solutions for optical transport networks are often associated to single-vendor optical domains, managed as single entities, in a deployment model that is commonly referred to as fully aggregated. Such controllers do export and expose interfaces for the limited control of abstracted resources and operations via north-bound interface (NBI) to operations/business support systems (OSS/BSS), but such APIs are often vendor specific and internal control aspects related to provisioning, monitoring and resource management remain proprietary and not disclosed. Disaggregation of optical networks refers to a deployment model of optical systems, by composing and assembling open, available components, devices and sub-systems. This disaggregation is driven by multiple factor (the mismatch between the needs of operators and the ability to deliver adapted solutions by vendors or the increase in hardware commoditization) and disaggregated networks are an excellent use case for open and standard interfaces, showing the benefits of a unified, model-driven development. In this paper, we address the SDN control of a disaggregated optical networks and its role in a wider Control Management and Orchestration (COM) architecture to offer ETSI NFV Network Services in a metropolitan infrastructure, characterized by multiple geographical locations and NFVI. We highlight the main use cases and the implemented extensions to the ONOS Platform for the aforementioned purpose. We detail the design of the controller (core systems and applications); the approach taken for model driven-development, including the YANG modelling language for the different optical devices and the NETCONF protocol to remotely configure the devices and, finally, the experimental validation of the approach and implementation with selected scenarios.

Barbara Martini
Latency-aware network service orchestration over an SDN-controlled multi-layer transport infrastructure
S. Fichera1, R. Martínez2, B. Martini3, M. Gharbaoui3, R. Casellas2, R. Vilalta2, R. Muñoz2, and P. Castoldi1
1Scuola Superiore Sant’Anna, Pisa, Italy
2Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Barcelona, Spain
3National Inter-University Consortium for Telecommunications (CNIT), Pisa, Italy

In this paper, we present latency-aware orchestration strategies that jointly consider satisfying both the allocation of computing resources (in distributed DCs) and the bandwidth and latency networks requirements, which are experimentally evaluated within a Multi-Layer (Packet over Optical Flexi-Grid) Transport Network and considering different DC set-ups and capabilities.

Raul Muñoz
Hierarchical and recursive NFV service platform for end-to-end network service orchestration across multiple NFVI domains
R. Muñoz1, R. Vilalta1, R. Casellas1, R. Martínez1, F. Vicens2, J. Martrat2, V. López3, and D. López3
1Centre Tecnològic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels (Barcelona), Spain
2ATOS, Madrid and Barcelona, Spain
3Telefónica I+D, Madrid, Spain

The ETSI network function virtualisation (NFV) management and orchestration (MANO) architectural framework defines an NFV service platform composed of an NFV orchestrator and virtualised network function (VNFs) managers that are responsible to provide NFV network services. Network services can be defined as the joint instantiation of VNFs and the provisioning of required network connections between the different VNFs to jointly realise a more complex function (e.g. service function chaining). In general, it is assumed that a single service platform is governing the whole NFV infrastructure (NFVI) domain from the edge to the core of the network, composed of multiple edge computing and core DCs interconnected by heterogeneous optical access, metro and core transport networks. However, network operators will fragment their transport networks and DCs into multiple NFVI domains for scalability, administrative, or security issues. Each NFVI domain can be provided by different vendors relying on their own NFV service platforms or leveraging open source solutions such as SONATA, OSM, or ONAP. In this paper, we propose a hierarchical and recursive network service orchestration architecture to compose end-to-end network services by aggregating network services provided by per-domain NFV service platforms together with VNFs.


NOA invited presentations:

Juan Diego Ania-Castañón
Polarization control in closed cavity Raman fiber lasers
G. Rizzelli, P. Corredera Guillén, and J. D. Ania-Castañón
Instituto de Óptica “Daza de Valdés”, CSIC, Madrid, Spain

Polarization control in fiber optics systems has been demonstrated through the exploitation of the polarization pulling phenomenon [1,2]. The stimulated Raman scattering effect generated in optical fibers with low polarization mode dispersion (PMD) allows to achieve the concurrent amplification and polarization of initially unpolarized light, thanks to the polarization dependence of the Raman gain [3]. In recent works, we have highlighted the possibility to improve the conversion efficiency of conventional Raman polarizers in half-open cavity random distributed feedback (rDFB) fiber lasers with highly polarized pumps and low-PMD spun fiber [4]. Here we present the experimental analysis of the polarization properties of Raman polarizers based on a closed cavity configuration, where different fibers ranging from low-PMD single mode fiber to high-PMD dispersion compensation fiber, are used as the gain medium. The output spectrum, output DOP and SOP evolution of the generated first Stokes component in both propagation directions is investigated as the input SOP of the pump is scrambled. Our findings expose a remarkable improvement in pumping efficiency and output DOP even in the worst-case scenario of a cavity encompassing a high-PMD fiber.
[1] S. Pitois, J. Fatome, and G. Millot, Polarization attraction using counter-propagating waves in optical fiber at telecommunication wavelengths, Optics Express, vol. 16, no. 9, pp. 6646–6651, 2008.
[2] J. Fatome, S. Pitois, P. Morin, and G. Millot, Observation of light-by-light polarization control and stabilization in optical fibre for telecommunication applications, Optics Express, vol. 18, no. 15, pp. 15311–15317, 2010.
[3] M. Martinelli, M. Cirigliano, M. Ferrario, L. Marazzi, and P. Martelli, Evidence of Raman-induced polarization pulling, Optics Express, vol. 17, no. 2, pp. 947–955, 2009.
[4] J. Nuño, G. Rizzelli, F. Gallazzi, F. Prieto, C. Pulido, P. Corredera, S. Wabnitz, and J. D. Ania-Castañón, Open-cavity spun fiber Raman lasers with dual polarization output, Scientific Reports, vol. 7, no. 1, pp. 13681 (2017).

Peter Horak
Multi-band nonlinear Schrödinger equation for efficient simulation of parametric optical amplifiers and oscillators
I. Begleris and P. Horak
Optoelectronics Research Centre, University of Southampton, UK

Coupled nonlinear Schrödinger equations for the simulation of optical parametric amplifiers with a wide wavelength separation between pump, signal, and idler have been developed. The simulation is made efficient by only considering narrow wavelength ranges around the relevant bands with high wavelength resolution, which in addition to parametric amplification allows the inclusion of intra-band nonlinear effects. As an example, we simulate and analyse the properties of a fibre optical parametric oscillator.

Pascal Landais
Nonlinearity mitigation of DQPSK signal by frequency-shift free spectral inversion using counter-propagating dual pump four-wave mixing in a semiconductor optical amplifier
A. Anchal1, P. Kumar2, S. O’Duill3, P. M. Anandarajah3, and P.Landais3
1Department of Applied Physics, The Selim and Rachel Benin School of Computer Science and Engineering, The Hebrew University of Jerusalem, Israel
2Department of Electrical Engineering, Indian Institute of Technology Kanpur, Kanpur, India
3School of Electronic Engineering, Dublin City University, Ireland

We present a scheme of nonlinearity mitigation of DQPSK signal in transmission fiber using frequency-shift free mid-span spectral inversion (MSSI). MSSI is obtained by using counter-propagating dual pump four-wave mixing in a semiconductor optical amplifier (SOA). Frequency-shift between signal and conjugate is avoided by keeping two pump frequencies symmetrical about the signal frequency. We examine the performance of MSSI by scrutinizing the improvement of the Q-factor of a 100 Gbps DQPSK signal transmitted over standard single mode fiber, as a function of launched power for different span lengths and number of spans. We demonstrate a 7.8 dB improvement in input power dynamic range and an almost 92 % increase in transmission length for optimum MSSI parameters of -2 dBm pump power and 400 mA SOA current.

João Pedro
Strategies for optimized Raman amplification deployment in DWDM mesh networks
J. Pedro1,2 and N. Costa1
1Coriant Portugal, Amadora, Portugal
2Instituto de Telecomunicações, Instituto Superior Técnico, Lisboa, Portugal

Raman amplification can be critical for the feasibility of the most performance-demanding lightpaths in regional and long-haul networks, minimizing the need to deploy expensive 3R regenerators and/or enabling to use more spectral efficient channel formats. Hybrid Raman/EDFA amplifiers can cost-effectively exploit the benefits of Raman amplification. However, these amplifiers are costlier than simple EDFAs. Hence, their deployment should be optimized such that the resulting capacity increase and cost reduction (due to saving 3R regenerators) outweighs the additional cost of introducing these amplifiers. Achieving this goal can be a complex task in DWDM mesh networks, in view of the different lightpaths that overlap at each fibre span. This paper overviews optimization strategies to place hybrid Raman/EDFA amplifiers in DWDM networks with the objective of minimizing the overall network capital expenditures. The performance of these strategies is evaluated using reference long-haul networks. Results show that an optimized placement strategy enables to maximize the benefit of deploying hybrid Raman/EDFA amplifiers while still keeping their number to a minimum.

Mingming Tan
RIN transfer mitigation technique using broadband incoherent pump in distributed Raman amplified transmission systems
M. A. Iqbal, Mingming Tan, and P. Harper
Aston Institute of Photonic Technologies, Aston University, Birmingham, UK

The paper reviews the recent advances on RIN transfer mitigation techniques used in distributed Raman amplified long-haul coherent transmission systems. The use of a broadband first order pump in substantial pump to signal RIN transfer mitigation has been demonstrated experimentally in both bidirectional and backward only pumping schemes. The generation process of a novel broadband, low RIN and incoherent pump is also reported in details. In a 10×120Gb/s DP-QPSK WDM transmission system, our proposed pumping schemes shows maximum transmission reach up to 8332km and significant reach extensions compared with conventional low RIN and narrowband Raman pump sources.

Feng Wen
Mitigation of amplitude and phase distortions by using conjugate-NOLM regenerator
Feng Wen1,2, Baojian Wu2, Feng Yang3, and S. Sygletos1
1Aston Institute of Photonic Technologies, Aston University, Birmingham, UK
2Key Lab of Optical Fiber Sensing and Communication Networks, Ministry of Education, University of Electronic Science and Technology of China, Chengdu, China
3Lab of Holographic Optical Sensing, Marolabs Co., Ltd, Chengdu, China

In this paper we propose a conjugate nonlinear optical loop mirror scheme (Conj-NOLM) by cascading two NOLMs with an intermediate optical phase conjugator stage (OPC). This new configuration utilizes mid-span spectral inversion to cancel out the nonlinear phase distortion that is introduced by the two NOLM units. Moreover, numerical investigation has been carried out for 16-QAM signals demonstrating increased robustness against accumulated amplitude and phase distortions in the transmission links.


Novel Glasses invited presentations:

Trevor Benson
The effects of deformation in large step index fibres
D. S. Kumar1, S. C. Creagh2, S. Sujecki1, and T. M. Benson1
1George Green Institute for Electromagnetics Research, Faculty of Engineering, University of Nottingham, UK
2School of Mathematical Sciences, University of Nottingham, UK

Progress in the modelling of ray-based dynamics in large step-index fibres (SIF) is reported. In the model developed the propagation of a light distribution through the fibre is achieved by discretising the mixed phase space and employing an iterative finite operator. The model allows for the deformation of the core and/or cladding cross-sectional boundaries of the SIF.  In the presence of such deformations the light distribution in the mixed phase space reveals the relationship between the input light distribution and the net ray flux entering the core.

Camille-Sophie Brès
Enhancing optical nonlinear processes performance of silicon nitride waveguides
C-S. Brès, E. Takgoudi, and D. Grassani
Ecole Polytechnique Fédérale de Lausanne, Photonic Systems Laboratory (PHOSL), Lausanne, Switzerland

Silicon nitride has recently attracted significant interest for nonlinear integrated optics. In addition to its excellent linear properties, silicon nitride offers a bandgap larger than silicon, and a wide transparency window spanning the visible to the mid infrared. As such, research efforts have been focused on leveraging these properties in order to achieve efficient nonlinear wave-mixing of the third and second order. In this paper we will show how mid infrared light can be efficiently generated in large cross section silicon nitride waveguides through careful dispersion engineering and how second order nonlinearities can be significantly enhanced through an all-optical poling process.

Animesh Jha
Near-IR laser and Raman spectroscopy of colon mucosal tissues: A comparative study on metabolite characterisations for early diagnosis of inflammation and ulceration
J. G. Addis1, N. Mohammed2, O. Rotimi3, V. Subramanian2, and A. Jha1
1Institute for Materials Research, School of Chemical and Process Engineer, University of Leeds, UK
2Molecular Gastroenterology, St James University Hospital, University of Leeds, UK
3Department of Histopathology, St James University Hospital, University of Leeds, UK

Mucosal tissues exhibit extended near-IR transparency in the 900-1300 nm window, which overlaps nicely with the technologies developed for optical communication systems operating in the 800 – 1700 nm range. By taking advantage of the off-the-shelf components technology, we have used the single-mode 976 nm diode laser for pumping bulk Yb3+-ion doped glass. For histopathological microscopic application, in the first instance, lasing in a narrow window of 1050 – 1055 nm was demonstrated. The tuneability was limited due gain medium design. The light scattering properties of the inflamed and healthy bowel human tissues, excised from patients with ulcerative colitis, were characterised between 940 nm and 1055 nm. The ultimate goal of this research is to use laser ex vivo for a comparative study for near-IR transmission (scattering) and Raman spectroscopy for differentiating between the inflamed and inactive (healthy) mucosal lining. The data for near-IR light scattering of mucosal tissues are reported and compared with other vascularised tissue with similar morphological features. Besides IR scattering measurements, the Raman spectroscopic data for each type of tissue was correlated statistically with the healthy and inflamed tissues and from the analysis of 60 tissue samples, a clear difference was identified in the concentrations of carotenoids, which were twice as strong in the inflamed tissues. The comparative spectroscopic data demonstrated the carotenoids, as one of the key metabolites, which were strongly upregulated, whereas the phospholipids were found to be downregulated in inflamed tissue. Myoglobin was another metabolite which was also identified. The results were also compared with the cancerous tissues where the upregulation of carotenoids is commonly featured in the metabolic pathways. Using multivariate statistical analysis, we show that the intensities of five peaks (three carotenoid peaks at Raman shifts of 1003, 1155 and 1518 cm-1 and two phospholipid peaks at 1440 and 2762 cm-1 can be used to discriminate between endoscopically inactive and inflamed tissue. In this way, we demonstrate the utility of Raman spectroscopy as an early diagnosis tool for assessing the presence of inflammation or mucosal healing in patients with ulcerative colitis.

Marcin Kochanowicz
1.5 – 2.1 mm broadband ASE in rare-earth co-doped glasses and double-clad optical fibers
M. Kochanowicz1, J. Żmojda1, P. Miluski1, D. Mazur1, A. Baranowska1, M. Sołtys2, W. A. Pisarski2, J. Pisarska2, T. Ragin1, M. Ferrari4,5, G. C. Righini5,6, M. Jäger7, M. Sitarz3, and D. Dorosz3
1Bialystok University of Technology, Bialystok, Poland
2Institute of Chemistry, University of Silesia, Katowice, Poland
3AGH University of Science and Technology, Krakow, Poland
4IFN - CNR CSMFO Lab. and FBK, Povo, Trento, Italy
5Enrico Fermi Centre, Roma, Italy
6MipLAB. IFAC - CNR, Sesto Fiorentino, Italy
7Leibniz Institute of Photonic Technology (IPHT), Jena, Germany

Broadband ASE (amplified spontaneous emission) optical fiber sources as well as fiber lasers emitting radiation in the eye-safe range (>1.5 μm) have attracted extensive interest because of their applications in surgery, remote sensing, lidar and atmospheric pollution monitoring. The most popular silica fibers are characterized by low losses, but due to high phonon energy the efficiency of donor – acceptor energy transfer in e.g. Yb3+/Ho3+, Tm3+, is strongly limited. Searching a new low phonon, thermally, low phonon energy glasses for optical fiber technology is still a scientific hot topic. Presented germanium based glasses and optical fibers due to low phonon energy (800 cm-1) and high transparency up to 5.5 µm range enable to achieve 1.5 – 2.1 µm emission corresponding to radiative transitions of Er3+: 4I13/24I13/2, Tm3+: 3F43H6 and Ho3+: 5I75I8. The presentation will show possibility of obtaining broadband luminescence in low phonon germanate glasses and double-clad optical fibers co-doped with Yb3+/Ho3+, Yb3+/Tm3+/Ho3+ and Er3+/Tm3+/Ho3+. Moreover, experimental results of silica-free germanium based Tm3+/Ho3+ co-doped fiber laser pumped at 796 nm will be presented.
[1] M. Kochanowicz et al., Proc of IEEE (2016), doi: 10.1109/ICTON.2016.7550634.
[2] M. Kochanowicz et al., Proc. of SPIE, vol. 9816 (2015).
[3] Y. Tian, L. Zhang, S. Feng, R. Xu, L. Hu, and J. Zhang, Opt. Mater. 32(11) (2010) 1508–1513.

Martin Leich
Photodarkening in Yb-doped silica fibers – Mitigation by co-doping and thermal effects
M. Leich, S. Jetschke, S. Unger, A. Schwuchow, and M. Jäger
Leibnitz-Institut für Photonische Technologien e.V., Jena, Germany

Photodarkening in rare-earth doped fibers has been subject of intense research over the last decade as the main issue limiting high power performance and long-term stability of fiber lasers. Reviewing previous and current experiments on Yb-doped silica fibers, the relationship between photodarkening mitigation, refractive index control and fiber heat load for will be discussed for the most prominent co-dopants. The main focus of attention will be paid on the mitigation of Photodarkening by co-doping with aluminum, phosphorous, cerium and germanium. Beside this, we dedicate ourselves on the thermal properties of NIR-pumped fibers and show that especially for high pump intensities PD mitigation can also result in a temperature enhancement of the active fiber. This can even become a critical issue for high power laser performance, e.g. by lowering the thermal mode instability threshold of LMA fibers.

Jarmila Müllerová
Thin films of barium strontium titanate from the viewpoint of light-based applications
J. Müllerová1, P. Šutta2, L. Prušáková2 , and R. Medlín2
1Institute of Aurel Stodola, Faculty of Electrical Engineering, University of Žilina, Slovak Republic
2New Technologies – Research Centre, University of West Bohemia, Plzeň, the Czech Republic

In this paper we report results from optical transmittance spectroscopy complemented with data on structure from XRD measurements to determine optical properties of a series of as-deposited and annealed (at 900 °C) BaSrTiO3 (BST) thin films deposited by RF magnetron sputtering. The members of the series differ by the substrate temperature and additional oxygen to accompany argon in the deposition chamber. The perovskite structure with weak preferred (110) orientation was detected for annealed BST thin films whilst the as-deposited films were amorphous. Dispersive optical properties – refractive indices, absorption coefficients and optical band gaps were determined from transmittance spectra. After annealing refractive indices increase to prove the densification of material accompanied by the thickness shrinkage. Optical band gaps calculated either by Tauc procedure or determined as iso-absorption levels are also found to be deposition dependent.

Laeticia Petit
Processing and characterization of bioactive borosilicate glasses and scaffolds with persistent luminescence
P. Roldán Del Cerro1, M. Saarinen2, J. Massera2, I. Norrbo3, M. Lastusaari3,4, and L. Petit1
1Photonics Laboratory, Tampere University of Technology, Finland
2Tampere University of Technology, BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Finland
3University of Turku, Department of Chemistry, Finland
4Turku University Centre for Materials and Surfaces (MatSurf), Finland

We report our latest results on the development of borosilicate glasses with persistent luminescence (PeL). Those PeL glasses were processed by adding PeL microparticles (MPs) in the glass using the direct doping method. First, we explain the challenges to balance the survival and dispersion of MPs when preparing borosilicate glasses using this method. Then, we show that scaffold can be obtained using the sintering process from these glasses but also by adding PeL microparticles (MPs) in the glass powder prior to sintering. Finally, we discuss the impact of the scaffold fabrication process on the PeL properties of the MPs. Keywords: borosilicate glasses, SrAl2O4:Eu2+,Dy3+ microparticles, persistent luminescence, direct particles doping method, sintering.

Markus Pollnau
Energy-transfer processes among non-homogeneously distributed rare-earth ions and impact on amplification and lasing
I. Carrasco1, L. Agazzi2, P. Loiko3, and M. Pollnau1,2,3
1Advanced Technology Institute, Department of Electrical and Electronic Engineering, University of Surrey, UK
2Integrated Optical Micro Systems, MESA+ Institute, University of Twente, The Netherlands
3Department of Materials and Nano Physics, School of Information and Communication Technology, KTH – Royal Institute of Technology, Kista, Sweden

Energy-transfer processes such as energy-transfer upconversion are often detrimental to the performance of rare-earth-doped amplifiers and lasers on the typical luminescence transitions in the near-infrared spectral region between 1 – 2 µm. In order to quantify the influence of these interionic processes on amplification and lasing, not only luminescence decay curves have to be measured, but also the population dynamics of the electronic level scheme need to be modeled. The usually encountered non-homogeneous ion distributions complicate the situation. Here we present a stochastic model of energy-transfer processes that takes a statistical ion distribution into account. The influence of energy-transfer upconversion and cross-relaxation on amplification and lasing on the 1.06 µm transition in Nd3+, the 1.53 µm transition in Er3+, or the 1.84 µm transition in Tm3+ under these conditions is investigated.

Francesco Prudenzano
Continuous-wave and pulsed optical fiber lasers for medium infrared applications
M. C. Falconi1, D. Laneve1, M. Bozzetti1, T. T. Fernandez2, G. Galzerano2, and F. Prudenzano2
1Department of Electrical and Information Engineering, Politecnico di Bari, Italy
2IFN-CNR, Department of Physics, Politecnico di Milano, Italy

In this paper, a CW amplifier and a gain-switched Dy3+-doped ZBLAN fiber laser, in-band pumped, are modeled. An ad-hoc refined finite difference time method (FDTD) approach has been followed in order to integrate the time-dependent rate equations coupled to the power propagation equations. In-band pumping at 2.8 μm wavelength is employed for simulating the emission of optical pulses at 3 μm wavelength. A time-modulated pump beam allows obtaining a gain switching regime. Preliminary simulation results promise that a pulsed laser, providing stable single-pulse operation at 10 kHz with a peak power close to 8 W and a full wave at half maximum (FWHM) less than 800 ns, for an input pump of 1 W with 30% duty cycle, could be constructed.

Diego Pugliese
Multicomponent rare earth-doped phosphate glasses for compact lasers and amplifiers
D. Pugliese, N. G. Boetti, E. Ceci-Ginistrelli, D. Gallichi-Nottiani, D. Janner, J. Lousteau, and D. Milanese
Politecnico di Torino, Italy

Thanks to its very high solubility in laser-active rare earth ions and outstanding thermo-mechanical properties, phosphate glass host represents a genuine alternative to the more traditional and employed silica glass platform to develop compact active devices, such as lasers and amplifiers. In particular, multicomponent phosphate glasses can withstand up to 1021 rare earth ions/cm3, typically about 50 times more than the silica glass matrix, without showing clustering effects. In this work we will report the ongoing activities and the recent results obtained by our research group on the design, processing and characterization of novel Er-, Nd- and Yb-doped and Yb/Er co-doped custom phosphate glasses to be used as active medium for compact laser systems and optical amplifiers.

Billy Richards
Glass thin films for planar optical components fabricated using ultrafast laser plasma doping
B. D. O. Richards1, E. K. Barimah1, T. Mann1, E. H. Dos Santos1, A. Boontan1, C. Russell2, P. Steenson2, and G. Jose1
1Applied Photon Science Group, School of Chemical and Process Engineering, University of Leeds, UK
2School of Electrical and Electronic Engineering, University of Leeds, UK
Ultrafast pulsed lasers with pulse durations of 40-100 fs are used to deposit rare earth doped tellurite glass onto silica glass substrates in a pulsed laser deposition (PLD) chamber. Under certain conditions, the tellurite glass plasma mixes with the silica glass network producing a thin glass film of tellurite-modified-silica which produces some unique physical, and when doped with rare earth ions, spectroscopic properties. Layers of tellurite-modified-silica glass up to 2 µm thick have been produced with refractive indices of around 1.65, compared to 1.46 and 2.0 for the silica substrate and tellurite target glasses, respectively. Rare earth ions can be doped into these layers in concentrations which are higher than would be possible in pure silica glass without clustering, and Er3+ for example exhibits unusually long 1.535 µm fluorescence lifetimes in these thin films. Tm3+ ions have also been doped into these layers, yielding fluorescence with wavelength up to around 2 µm.

Elena Romanova
Novel approach for design of fiber-based evanescent wave sensors for the mid-infrared spectroscopy
E. Romanova1, S. Korsakova1, A. Rozhnev1,2, A. Velmuzhov3, and  V. Shiryaev3
1Saratov State University, Russia
2Saratov Branch of the Institute of Radio-Engineering and Electronics of RAS, Russia
3Institute of Chemistry of High Purity Substances of RAS, Nizhny Novgorod, Russia
For creation of the fiber-optic spectroscopic tools in the mid-IR, broadband sources of coherent radiation and sensing elements based on optical fibers are to be designed as two counterparts of one problem of the mid-IR spectral range exploration. We present a theoretical approach based on the electromagnetic theory of optical fibers for design of the sensing elements (made of multimode chalcogenide fibers) of various shapes and refractive index profiles. We focus on discussion of sensitivity and output characteristics of the sensors designed for chemical analysis of liquids, in the theory and in spectroscopic measurements in the range of wavelengths of 2 – 10 microns.

Sławomir Sujecki
Time domain modeling of multimode selenide-chalcogenide glass fiber based mid infrared spontaneous emission sources
S. Sujecki1,2, L. Sojka1, Z. Tang2, E. Barney2, D. Furniss2, T. M. Benson2, and A. B. Seddon2
1Department of Telecommunications and Teleinformatics, Faculty of Electronics, Wroclaw University of Science and Technology, Wroclaw, Poland
2George Green Institute for Electromagnetics Research, The University of Nottingham, Nottingham, UK

We develop time domain models of selenide-chalcogenide glass fibre based MIR spontaneous emission sources. The modelling parameters used are derived from the experimentally obtained data. The models are based on the rate equations approach to simulate the distribution of ions between the relevant energy levels. The optical power distribution within the fibre is calculated by solving a set of partial differential equations using specially developed finite difference schemes that allow for a direct inclusion of the step discontinuities appearing at the fibre facet. The results obtained are compared with simple models, which have been so far used for the purpose of time domain modelling of lanthanide doped ion fibres. We also study the effect of achieving equilibrium population according to Boltzmann distribution on the time dependence of spontaneous luminescence emitted by various radiative transitions.


Optical Microscopy invited presentations:

Paolo Bianchini
Tunable and multimodal microscopy from fluorescence to label free
1Nanoscopy, Istituto Italiano di Tecnologia, Genoa, Italy
2Department of Physics, University of Genoa, Italy
3Nikon Imaging Center @ Istituto Italiano di Tecnologia, Genoa, Italy

Optical microscopy uniquely provides non-invasive imaging of biological specimens and has become an essential tool in life sciences. The 3D (x,y,z) space is the natural environment where life takes place. Nevertheless, most of the times, life science researchers study molecular and cellular processes on cell cultures grown on flat substrates, in a 2D (x,y) fashion. Although such a situation is undesirable, it could be the most convenient also because microscopy required it to achieve the best performances. Luckily, the remarkable progress in microscopy together with the ability to grow three-dimensional multicellular constructs that mimic in vivo tissues, i.e., organoids [1], allows attacking, from a different perspective, still open universal questions in cellular and molecular biology. Moreover, non-linear optical processes have captured the attention of scientists for the development of novel super-resolved microscopy techniques. In particular, the non-linearity of saturation was exploited in fluorescence microscopy in order to overcome the diffraction limit. Super-resolution techniques like stimulated emission depletion (STED) [2], [3] and saturated excitation (SAX) [4] microscopy were developed, taking advantage of the photophysical properties of fluorescent molecules. So far, innovations proceed also with the exploitation of the near-infrared (near-IR) part of the spectrum, which allows to image at increased depth, to achieve greater resolution, contrast and molecular specificity, and furthermore to investigate label-free capabilities [5], [6]. Here, we propose an innovative approach that has the merit of the realization of a brand new multiscale and multimodal microscope allowing different simultaneous mechanism of contrast available in the image formation process [7]. Its success depends on the introduction of a robust polarization based label-free approach, a solution to improve the temporal resolution by an acousto-optic based selective plane illumination microscopy [8], and maintaining super-resolution capability with linear or non-linear interaction within a pump-probe scheme [5], [6]. We demonstrate the correlation of different mechanism of contrast applied to a variety of specimens, namely: isolated nuclei, cellular spheroids, living and fixed cells. Expansion microscopy samples will be imaged, too.
[1] Method of the year 2017: Organoids, Nat. Meth., vol. 15, no. 1, pp. 1–1, Jan. 2018.
[2] S. W. Hell and J. Wichmann, Breaking the diffraction resolution limit by stimulated emission: Stimulated-emission-depletion fluorescence microscopy, Opt. Lett., vol. 19, no. 11, pp. 780–782, 1994.
[3] G. Vicidomini, P. Bianchini, and A. Diaspro, STED super-resolved microscopy, Nat. Meth.
[4] K. Fujita, M. Kobayashi, S. Kawano, M. Yamanaka, and S. Kawata, High-resolution confocal microscopy by saturated excitation of fluorescence, Phys. Rev. Lett., vol. 99, no. 22, pp. 228105–4, 2007.
[5] N. Liuet al., Far-field subdiffraction imaging of semiconductors using nonlinear transient absorption differential microscopy, ACS Photonics, vol. 3, no. 3, pp. 478–485, 2016.
[6] P. Bianchini, C. Peres, M. Oneto, S. Galiani, G. Vicidomini, and A. Diaspro, STED nanoscopy: a glimpse into the future, Cell Tissue Res., vol. 360, no. 1, pp. 143–150, 2015.
[7] K. Korobchevskaya, C. Peres, Z. Li, A. Antipov, C. J. R. Sheppard, A. Diaspro, and P. Bianchini, Intensity weighted subtraction microscopy approach for image contrast and resolution enhancement, Sci. Rep., vol. 6, no. 1, p. 25816, 2016.
[8] M. Duocastella, G. Sancataldo, P. Saggau, P. Ramoino, P. Bianchini, and A. Diaspro, Fast inertia-free volumetric light-sheet microscope, ACS Photonics, vol. 4, no. 7, pp. 1797–1804, 2017.

Paola Borri
Coherent Raman scattering microscopy: Technology developments and biological applications
I. Pope, F. Masia, J. Bradley, K. Ewan, A. Karuna, L. Payne, I. Guschina, J. Harwood, K. Swann, T. Dale, P. Watson, W. Langbein, and P. Borri
Cardiff University, UK

Optical microscopy is an indispensable tool that is driving progress in cell biology, and is still the only practical means of obtaining spatial and temporal resolution within living cells and tissues. Coherent Raman Scattering (CRS) microscopy has emerged in the last decade as a powerful multiphoton microscopy technique which overcomes the need of fluorescent labelling and yet retains biomolecular specificity and intrinsic 3D resolution. We have developed in our laboratory several home-built CRS microscopes featuring innovative excitation/detection schemes and quantitative image analysis. Our second-generation CRS instrument is based on a single 5 fs Ti:Sa laser source with 350 nm bandwidth capable of exciting a wide vibrational range from 1000 /cm to 3500 /cm, thus enabling hyperspectral microscopy. It is also a multimodal system featuring simultaneous detection of CRS, two-photon fluorescence and second harmonic generation for correlative studies. Our latest technology developments include high-content high-throughput label-free quantitative chemical imaging via Bessel beam illumination and sparse sampling. Our latest biological applications feature quantitative imaging of intra-cellular lipid droplets in live mouse oocytes and early embryos.

Georges Boudebs
Optimizing dark field Z-scan for third order optical nonlinear measurements in a microscopic configuration
M. Chis1, C. Cassagne2, Hongzhen Wang2, C. Ciret2, and G. Boudebs2
1ESAIP, St-Barthélemy d'Anjou Cedex, France
2Université d’Angers, LPhiA, Laboratoire de Photoniques d’Angers, France

This study deals with the numerical simulations to optimize the parameters in general of the newly introduced Dark Filed Z-scan in a microscopic configuration for third order nonlinear (NL) refraction measurements into thin films. The method allows dynamic transparent nonlinear phase shifts to be clearly visible. The simulation of such images are obtained for very low induced refractive indices. Darkfield illumination requires blocking out of the central light which ordinarily passes through and around (surrounding) the NL specimen. A table to approximate opaque stop size versus magnification will be given depending on the numerical aperture of both the objective and the focusing lens into the tested material.

Juan Bueno
Which information can be obtained from collagen-based tissues imaged with polarization-sensitive second harmonic microscopy?
J. M. Bueno, F. J. Ávila, and P. Artal
Laboratorio de Óptica, Universidad de Murcia, Spain

Second Harmonic Generation (SHG) imaging microscopy of collagen-based samples was early reported to show a particular behaviour when using different types of polarized light. Polarization-sensitive (PS) SHG microscopy improves the visualization of different features within the samples and provides interesting information of structures with local anisotropy. This response to polarization can be used to further explore the physical properties of biological tissues at different scales (micro or external, and nano or internal) independently of the arrangement of the collagen fibers. In this invited talk the last advances in PS-SHG microscopy will be shown and discussed.

Adrian Cernescu
Near-field optical microscopy: Imaging and spectroscopy at 10 nm spatial resolution
A. Cernescu, neaspec GmbH, Germany
Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) allows to overcome the diffraction limit of conventional light microscopy or spectroscopy enabling optical measurements at a spatial resolution of 10nm, not only at visible frequencies but also in the infrared or terahertz spectral range.  s-SNOM employs an externally-illuminated sharp metallic AFM tip to create a nanoscale hot-spot at its apex. The optical tip-sample near-field interaction is determined by the local dielectric properties (refractive index) of the sample and detection of the elastically tip-scattered light yields nanoscale resolved near-field images simultaneous to topography.  Development of a dedicated Fourier-transform detection module for analysing light scattered from the tip which is illuminated by a mid-IR broadband laser source enables IR spectroscopy of complex nanomaterials. Applications presented demonstrate analysis of engineered polymer nanostructures and interfaces or functional semiconductor nanostructures. Detailed optical signal analysis enables quantitative nanoscale determination of free carrier concentration and mobility in low-dimensional structures. A modular system design enables straight forward pump-probe near-field optical measurements. Latest development of the cryo-neaSNOM systems allows nanoscopic optical measurements at below 10 K temperatures.

Shih-Hsuan Chia
Deep tissue multiphoton microscopy based on advanced femtosecond fiber sources
Shih-Hsuan Chia1,2, Hsiang-Yu Chung2, Wei Liu2, F. X. Kärtner2,3, and Guoqing Chang2,4
1Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan
2Center for Free-Electron Laser Science, DESY, and Physics Department, University of Hamburg, Germany
3The Hamburg Center for Ultrafast Imaging, Germany
4Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, China

The use of multiphoton microscopy has proven its potential on deep tissue virtual biopsy for early diagnosis and neuronal processes imaging. However, the capability of multiphoton microscopy strongly depends on the availability of easily operated femtosecond laser sources. By precise management of fiber-optic nonlinearity, we have demonstrated the way to generate nearly transform-limited femtosecond sources with the tunable wavelength range of 0.9 µm – 1.2 µm, covering both the GFP two-photon-excitation band and transparency window of common bio-tissues. The demonstrated approach is fully energy scalable to sub- 100 nJ level of pulse energy with the spectral tunable range down to 1.31 µm, which paves the way to capture deep-tissue imaging contrast from third harmonic generation and three-photon-excited GFP fluorescence. We applied such an energetic source to a proof-of-principle study of ex vivo human skin based on harmonics (i.e., second-harmonic generation and third-harmonic generation) imaging. This new type of fiber-format energetic ultrafast source will be performed as a robust solution for multiphoton microscopy applications, as well as studying the damage assessments from thermal heating and multiphoton absorption during the imaging process.

Alberto Diaspro
LIQUITOPY®: Liquid tunable microscopy towards a new paradigm in optical microscopy
A. Diaspro1,2,3
1Department of Nanophysics, Istituto Italiano di Tecnologia, Genoa, Italy
2Department of Physics, University of Genoa, Italy
3Nikon Imaging Center, Genoa, Italy

The possibility of integrating different light-matter interactions for producing optical microscopy images is the starting point for the design and realization of a brand new multiscale and multimodal optical microscope that has been recently named LIQUITOPY®, liquid tunable microscopy [1]. Three-dimensional optical sectioning, confocal and two-photon laser scanning microscopy and F-methods (FRAP, FLIM, FCS, FRET) coupled with image scanning microscopy, expansion microscopy, light-sheet microscopy and non-linear approaches are robust and at a high level of ripeness. The peak has been reached with the advent of super resolved fluorescence microscopy methods able to circumvent the diffraction limit [2, 3]. Two popular methods are related to the 2014 Nobel prize assignments, namely: “targeted” switching that confines the fluorescence emission to an area smaller than the diffraction of light – for example, STED [4] – and “stochastic” switching that implements single molecule localization exploiting the photo-switchable behavior of fluorescent molecules – for example, PALM or STORM [5]. Moreover, there is a trend towards label free methods like Mueller matrix and CIDS microscopy [6, 7]. Within this scenario, LIQUITOPY® is designed to integrate simultaneous acquisition of different contrast mechanisms taking a potential advantage from deep learning strategies [8] and to foster a brand new way of forming images from a full multiscale and multimodal approaches.
[1] A. Diaspro et al., Biophysical Journal 114 (3):347a (2018).
[2] A. Diaspro, Il Nuovo Saggiatore 30 (5-6): 45-51.
[3] S.W. Hell et al. Journal of Physics D: Applied Physics 48 (44): 443001 (2014).
[4] G. Vicidomini et al., Nature Methods 15(3): 190 (2018).
[5] H. Deschout et al., Nature methods 11 (3): 253 (2014).
[6] N. Mazumder et al., Journal of Optics 19 (2): 025301 (2017).
[7] A. Diaspro et al., IEEE Transactions on Biomedical Engineering 38 (7):670-678 (1991).
[8] F. Piccinini et al., Cell Systems 4:651–655 (2017).

Fu-Jen Kao
Coherent narrow-band light source for ultraslim endoscopes
Zhan-Yu Chen1, Ankur Gogoi1,2, Shao-Yu Lee1, Yuan Tsai-Lin1, Po-Wei Yi1, Ming-Kuan Lu1, Chih-Cheng Hsieh3,4, Jin Chang Ren5, Stephen Marshall5, and Fu-Jen Kao1
1Institute of Biophotonics, National Yang-Ming University, Taiwan
2Department of Physics, Jagannath Barooah College, Assam, India
3Division of Thoracic Surgery, Taipei Veterans General Hospital, Taiwan
4Department of Surgery, National Yang-Ming University, Taiwan
5Department of Electronic and Electrical Engineering, University of Strathclyde, UK

Background: ultraslim endoscopes with diameter less than 1 mm present an interesting frontier, for their applications in cholangiopancreatoscopy and procedures that would require very thin caliber. With the advent of miniature CMOS image sensors of outer diameter as small as 0.8 mm (after packaging) [1] and the emergence of high definition imaging guide (HDIG) [2], the bottleneck in further reducing the total diameter of the endoscope depends critically on the footprint of the matching light source. The Method: The output of an RGB laser module is coupled efficiently through a few light guiding fiber (~30 µm in diameter) to provides high coherence and high luminosity illumination. The laser is synchronized with a monochrome CMOS camera in a time lapsed manner for color image acquisition and reconstruction. In this way, high spatial resolution (than a comparable color CMOS camera), higher sensitivity, and narrow spectral band imaging are simultaneously realized, to facilitate differentiation of certain biological tissues or components. The speckle, as a result of the RGB laser’s coherence, which affects the illumination uniformity, is removed through mechanical stress modulation on light guiding fibers at acoustic frequency.
[1] M.K. Lu et al., J Biomed Opt. 19 (10), 105004-1-105004-4(2014).
[2] M.K. Lu et al., Biomedical Opt. Express 7(9), 3335-3344(2016).

Fu-Jen Kao
Time resolved imaging with stimulated emission in pump-probe microscopy
Subir Das, Bo-Wei Ho, and Fu-Jen Kao
Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan

Pump-probe microscopy has become a common platform for imaging based on nonlinear optical processes, such as stimulated emission (SE), ground state depletion (GSD), and excited state depletion (ESD). The capacity includes molecular specificity, improved resolution, and enhanced penetration depth [1]. In the past years, stimulated emission based pump-probe microscopy has demonstrated dark chromophore detection [2] and fluorescence lifetime imaging [3]. In this work, a pump-probe microscope is configured for the simultaneous detection of stimulated gain and spontaneous loss. We have used a pulsed diode laser, λpu = 635 nm as the pump (excitation) beam and a mode-locked Ti-sapphire laser, λpr = 780 nm, as the probe (stimulation) beam. The time delay (τ) between the pump and probe pulses are precisely controlled by adjusting the length of the triggering cables and setting the delay generator. The probe beam pulses are passed through two 15-cm long dispersive glass rods (SF-6) for extending into a pulse width of 1.5 ps. Both beams are coupled into the scanner and focused on the sample by an objective lens (10×, NA=0.3). For stimulated gain, the pump beam is modulated at a frequency, f1, and the probe beam is demodulated accordingly to extract the signal in the transmission direction with a photodiode as the detector (PDA 36A, Thorlabs). For spontaneous loss, the probe beam is modulated at frequency, f2, the spontaneous loss signal is than demodulated from the fluorescence detected in the reflection mode by a PMT. In all cases, a high performance lock-in amplifier (HF2LI, Zurich Instruments) is used. The output signal of the lock-in amplifier is then fed to the A/D channel of the scanning unit for image reconstruction. The scan rate is set at a frequency 500 Hz, to match the time constant (1.99 ms) of the lock-in amplifier. By demodulating fluorescence signal, the fluorescence lifetime and optical section images can be obtained with greatly reduced background, in which shot noise is attributed. Additionally, this technique improves signal-to-noise ratio and enhances penetration depth like multiphoton microscopy, without expansive femtosecond lasers.
[1] Martin C. Fischer, Jesse W. Wilson, Francisco E. Robles, and Warren S. Warren, “Invited Review Article: Pump-probe microscopy,” Rev. Sci. Instrum. 87, 031101 (2016).
[2] W. Min, S. Lu, S. Chong, R. Roy, G. R. Holtom, and X. S. Xie, "Imaging chromophores with undetectable fluorescence by stimulated emission microscopy," Nature 461, 1105-1109 (2009).
[3] P.-Y. Lin, S.-S. Lee, C.-S. Chang, and F.-J. Kao, "Long working distance fluorescence lifetime imaging with stimulated emission and electronic time delay," Optics Express 20, 11445-11450 (2012).

Rafał Kotyński
Single-pixel imaging with random sampling of the feature space
K. Czajkowski, A. Pastuszczak, and R. Kotyński
University of Warsaw, Faculty of Physics, Warsaw, Poland

Recent years bring a rapid development of indirect imaging techniques known as single-pixel or computational imaging. The range of their applications includes hyper-spectral imaging, polarimetric imaging, three-dimensional imaging, holographic imaging, optical encryption and imaging through scattering media. Microscopic single-pixel imaging offers novel routes to superresolution with use of spatial-frequency mapping and multispectral detection. We will focus on the progress in the sampling methods for single-pixel detectors, which can be utilized in microscopic techniques. Morlet wavelets are known to optimize the uncertainty principle in terms of being localized in the image space and spatial frequency spaces at the same time. We have proposed a sampling method for single-pixel detectors which is equivalent to a random sampling of a predetermined part of the feature space obtained with the Morlet wavelet representation of the image. The proposed sampling functions have a rich spatial and frequency content. Individually, each has a characteristic dimension, orientation and modulation frequency, but combined together they sample the image uniformly in a feature space spanned over these parameters. The proposed method offers an important improvement for single-pixel imaging at very high compression rates.

Régis Orobtchouk
Photonic integrated nanojet
A. Belarouci1, M. Calvo2, A. Mavel2, P. Rojo Romeo1, and R. Orobtchouk2
1Lyon Institute of Nanotechnologies INL, CNRS UMR 5270, Ecole Centrale de Lyon, Université de Lyon, France
2Lyon Institute of Nanotechnologies INL, CNRS UMR 5270, INSA de Lyon, Université de Lyon, France

We report the direct experimental observation of photonic nanojets created by single SixNy microdisks illuminated by a waveguide. High intensity sub-wavelength spots and low divergence nanojets are observed at a wavelength of 1550 nm. Light scattered from the disk is observed by imaging from above. The electromagnetic distributions inside and outside the microdisk are calculated by using finite-difference-time-domain method and compared to the experimental image. Such novel platform provides new pathways for high-resolution optical imaging, biophotonics, plasmonics, and optical data storage and offers exciting prospects for integration.

Igor Minin
Anomalous apodization effect on a mesoscale particle-lens with subwavelength resolution
I. V. Minin, et al., Siberian State University of Geosystems and Technologies, Russia
It is known that classical apodization method, in the form of an amplitude pupil-mask centrally situated on a particle-lens, can further reduce the waist of a photonic nanojet, however, it usually lowers the intensity at the focus due to blocking the incident light. In this report, the anomalously intensity-enhanced apodization effect was discovered for the first time via numerical simulation of focusing of the different shape particle-lenses, and a greater than 100% peak intensity increase was realised for the produced photonic nanojets. Experimental investigations confirm this effect.

Adrian Podoleanu
Advances in optical coherence tomography
A. Podoleanu, Applied Optics Group, School of Physical Sciences, University of Kent, Canterbury, UK
Traditionally applied to imaging the eye, optical coherence tomography (OCT) is now being extended to fields outside ophthalmology and optometry. The tremendous increase in acquisition speed of the spectral domain OCT technology in the last decade has enabled the OCT community to contemplate real time volume display, has opened the field of no-dye angiography and that of fast interrogation of deformation patterns in elastography. The presentation will review the OCT applications in ophthalmology and endoscopy as well as the dynamic field of broadband and fast tunable optical sources for OCT. Current research in Kent combined spectral domain and time domain OCT principles into a new method, Master/Slave OCT, that delivers fast display of any number of en-face OCT images. The Master/Slave method simplifies the OCT technology, the signal processing as well as gives parallel, direct access to information from multiple depths in the tissue.

Gabriel Popescu
Label-free imaging of thick specimens using gradient light interference microscopy (GLIM)
G. Popescu, Quantitative Light Imaging Laboratory, Department of Electrical and Computer Engineering, Beckman Institute of Advanced Science and Technology, University of Illinois at Urbana-Champaign, USA
Light scattering limits the quality of optical imaging of unlabeled specimens: too little scattering and the sample is transparent, exhibiting low contrast and too much scattering washes the structure information altogether. As a result, current instruments, target specifically either the thin (low-scattering) specimens or the optically thick (multiply scattering) samples. We developed gradient light interference microscopy (GLIM) to extract 3D information from both thin and thick unlabeled specimens. GLIM exploits the principle of low-coherence interferometry to extract phase information, which in turn yields strong, intrinsic contrast of transparent samples, such as single cells. Because it combines multiple intensity images that correspond to controlled phase shifts between two interfering waves, GLIM is capable of suppressing the incoherent background due to multiple scattering. Due to the specific, common path interferometric geometry used, the two interfering fields are affected identically by multiple scattering and remain comparable in power even in deep tissue, thus, allowing them to interfere with great contrast. Thus, GLIM yields real-time tomography of optically thick samples via full field imaging. These results indicate that GLIM can become a valuable label-free analysis tool for in-vitro fertilization, where contrast agents and fluorophores may impact the viability of the embryo. We demonstrate the use of GLIM to image various samples, including standard micron size beads, single cells, cell populations, and thick bovine embryos. GLIM operates as an add-on to a conventional microscope and overlays seamlessly with the existing channels (e.g., epi-fluorescence).

Chrysanthe Preza
Recent advances in 3D structured illumination microscopy
A. Doblas1, H. Shabani1, G. Saavedra2, and C. Preza1
1Department of Electrical and Computer Eng. University of Memphis, USA
2Department of Optics, Universitat de València, Burjassot, Spain

In structured illumination microscopy (SIM) the sample under investigation is illuminated using a structured illumination (SI) pattern. This SI pattern encodes high spatial frequencies of fine features within the sample, which usually are not transferred by the conventional three-dimensional (3D) optical transfer function (OTF) of the imaging system and fills the missing cone of frequencies in the OTF for better discrimination of the out-of-focus light. Thereby, SIM provides super-resolution (SR) performance beyond the diffraction limit and optical-sectioning (OS) capability with the use of data post-processing approaches. 3D structured patterns that include lateral and axial variations in the illumination have attracted more attention recently as they provide OS and SR enhancement in three dimensions. In this paper, we review recent implementations in generating a 3D SI pattern with tunable modulation frequency (independently of both the objective lens and the wavelength used) using a Fresnel biprism or a Wollaston prism. From the raw SIM images, final SIM images with simultaneous OS and SR are retrieved without artifacts due to coherent noise.

Genaro Saavedra
Recent advances in digital holographic microscopy
G. Saavedra1, M. Martinez-Corral1, J. I. Garcia-Sucerquia2, E. Sanchez-Ortiga1, and A. Doblas3
13D Imaging & Display Laboratory, Department of Optics/Optometry and Vision Science, Universitat de València, Burjassot, Spain
2School of Physics, Universidad Nacional de Colombia-Sede Medellin, Medellin, Colombia
3Department of Electrical & Computer Eng., The University of Memphis, Memphis, USA

In digital holographic microscopy (DHM) a hologram is captured in the image space provided by a microscope. The transfer of the phase and amplitude structure in the original sample to the hologram is in fact strongly affected by the use of the imaging microscope. A big research effort has been devoted to correct these distortions both by numerical and optical compensation. In this contribution, we present several proposals to improve the performance of classical DHM architectures by an a priori approach to compensate physically these perturbations. Experimental results are also presented to validate the proposed techniques.

George Stanciu
A new technique in scanning near field optical microscopy used for investigations on the biological samples
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
2Microbiology Immunology Department, Faculty of Biology, University of Bucharest, Romania

We present a new technique based on apertureless near field microscopy using a femtosecond Ti:sapphire laser that is used for the investigations on biological samples. This technique is integrated in a multimodal microscopy system. The beam of a Ti:sapphire laser  is focused by using the objective of an inverted microscope on the surface sample.  Electric field of the laser beam oscillates in a parallel plan with the sample surface and electric dipoles created by the electric field emit a radiation that is modulated by the AFM tip. This radiation is collected by the objective of the s-SNOM module, placed above the sample being sent to the detector. The images shown a better good contrast compared to those in s-SNOM.

Stefan Stanciu
Towards automated tissue characterization using parallel bag-of-features experts dealing with two-photon excitation fluorescence and second harmonic generation microscopy datasets
S. G. Stanciu1, R. Hristu1, A. Dumitru2, R. M. Buga1, T. Totu1, M. Popescu1, and M. Costache2
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
2Department of Pathology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania

Label-free tissue imaging with Multiphoton Microscopy (MPM) techniques such as Two-Photon Excitation Fluorescence Microscopy (TPEF) or Second Harmonic Generation Microscopy (SHG) can provide cues of similar pathologic relevance to the information collected for characterization / confirmation purposes with traditional histopathology protocols based on fixation and staining. To date, various approaches for the automated characterization of MPM datasets have been proposed, but usually these address the outputs of a single technique, while MPM imaging sessions can simultaneously yield multiple information categories associated to distinct modalities. We discuss here the main concepts of the Bag-of-Features (BoF) paradigm used for automated image classification and retrieval, and a series of past experiments that dealt with BoF based tissue characterization. Further on, we present some of our connected efforts placed on the problem of human epithelial tissue characterization with TPEF & SHG and introduce a concept for MPM data classification based on multiple BoF experts that utilize in a parallel manner complementary information categories.

Denis Tranca
Nanoscale investigations of optical fiber by using scattering scanning near-field optical microscopy
D. E. Tranca1, R. Hristu1, S. G. Stanciu1, C. V. Sammut2, and G. A. Stanciu1
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
2Department of Physics, Faculty of Science, University of Malta, MSIDA, Malta

Scattering Scanning Near-field Optical Microscopy (s-SNOM) was used for imaging the transversal surface of different optical fibers. The s-SNOM images were then processed in order to map pixel-by-pixel the refractive index of the optical fibers transversal surface. The s-SNOM imaging technique is widely known for its capability to reach nanoscale resolution, therefore the obtained maps of refractive index based on s-SNOM data are as well characterized by nanoscale resolution. We used a multimodal microscopy system to obtain the topographic images acquired by Atomic Force Microscopy (AFM) simultaneously with a s-SNOM. The technique proves to be a powerful tool for characterization of refractive index profile of optical fibers, but also to check the optical fibers quality or other types of optical waveguides at nanoscale.

Shi-Wei Chu
Super-resolution microscopy based on nonlinear plasmonics
Shi-Wei Chu, National Taiwan University, Taipei, Taiwan
During the past decade, the diffraction limit of resolution was beautifully overcome by manipulating the on/off switching of fluorophores, or by saturation of fluorescence emission, resulting in resolution below 100 nm. Nevertheless, fluorescence exhibits intrinsic photobleaching issue. The on/off switching techniques require repeated excitation of a single fluorophore while the saturation techniques need strong incident power, both leading to faster bleaching of labeling. In this report, we feature the first observation of interesting nonlinearities of SPR scattering, including saturation, reverse saturation, and all-optical switching, in an isolated plasmonic nanostructure. These nonlinear behaviors are successfully applied to imaging, and bring the spatial resolution down to lambda/8, which is enough to resolve the wavelength of surface plasmon polariton in nanoscale optoelectronic devices. Potential applications range from biomedical imaging and functional plasmonic nanostructures. We also anticipate our demonstration to be a stimulating example in finding more exotic contrast agency for improving optical resolution.

George Stanciu
Changes in the collagen structure of thyroid nodule capsules determined by polarization-resolved second harmonic generation microscopy
R. Hristu1, B. Paun2, L. Eftimie1,3,4, S. G. Stanciu1, D. E. Tranca1, and G. A. Stanciu1
1Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Romania
2Faculty of Automation and Computer Science, Technical University of Cluj-Napoca, Romania
3Central Military Hospital, Pathology Department, Bucharest, Romania
4University of Medicine "Carol Davila" Bucharest, Romania

Thyroid carcinomas represent a challenging problem as their differentiation from the much more frequent benign pathologies can be sometimes difficult. Automatic diagnostic approaches that can differentiate between malignant and benign thyroid nodules would be of great benefit for addressing thyroid pathologies. In this study we have used polarization-resolved second harmonic generation microscopy to investigate collagen organization in the fibrillar capsules surrounding human benign and malignant thyroid nodules. We demonstrate that imaging the collagen capsules at different laser beam polarization angles and fitting the second harmonic generation intensity with a theoretical curve can yield information on the nonzero components of the second order susceptibility tensor and the orientation of the collagen fibers. We have used this approach to differentiate between capsules surrounding the thyroid follicular adenoma and papillary carcinoma nodules. These results indicate that polarization-resolved second harmonic generation microscopy can provide additional information about the collagenous capsule surrounding thyroid nodules, which may complement intensity-based quantitative second harmonic generation microscopy and eventually traditional histopathologic examination.


OWW invited presentations:

Slavisa Aleksić
Estimating the modulation characteristics of white LEDs by their color temperature
K. Richter, S Aleksic, and C.-A. Bunge
Hochschule für Telekommunikation Leipzig (HfTL), Germany

It is obvious that white light-emitting diodes (LEDs) for lighting applications can also be used for data transmission. While most manufacturers of LEDs provide data on lighting properties, there is little information about their communication characteristics. Most white LEDs consist of a blue emitter with a yellow-converting phosphorescent coating, which limits the LED’s bandwidth. In this article, a connection between LED’s photometric and communication parameters will be analyzed. A newly-developed model will be presented, which is not only able to predict the blue-yellow distribution by only knowing the correlated color temperature (CCT), but is also capable of estimating the LED’s modulation bandwidth.

Nikos Bamiedakis
High-bandwidth organic light-emitting diodes for ultra-low cost visible-light communication links
P. de Souza1, N. Bamiedakis1, K. Yoshida2, P. P. Manousiadis2, G. A. Turnbull2, I. D. W. Samuel2, R. V. Penty1, and I. H. White1
1Electrical Engineering Division, Department of Engineering, University of Cambridge, UK
2Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, UK

Visible light communications (VLC) have attracted considerable interest in recent years due to increasing need for data communication links in home and enterprise environments. Organic light-emitting diodes (OLEDs) are widely used in display applications and in consumer electronics owing to their high brightness, high quality colour-rending capability and low cost. As a result, they are attractive candidates for the implementation of ultra-low cost visible light optical links in free-space and guided-wave communications. However, OLEDs need to exhibit a bandwidth of at least ~MHz to be able to support the modest data rates (~Mbps) required in these applications. Although fluorescent OLEDs typically exhibit shorter photon lifetimes than inorganic LEDs, the bandwidth performance of the large size OLEDs used in display applications are limited by their electrical characteristics. In the work presented therefore, we report on new OLED devices that exhibit 3dB bandwidths (BW3dB) larger than 10 MHz and investigate their bandwidth performance as a function of device size. It is demonstrated that the reduction of the device size results in a significant bandwidth improvement with a large BW3dB of 44 MHz obtained for a 0.12 mm2 device. A small signal equivalent circuit is employed to match the impedance characteristics of the OLEDs and estimate their frequency response. The model provides an insight into the basic electrical properties of the devices and demonstrates that the bandwidth improvement for the smaller size is due to the reduction of the electrical capacitance of the devices. More detailed modelling studies are underway to correlate these experimental results with simulation results and understand the fundamental limitations in bandwidth performance of such devices.

Rafael Gutierrez
An optical network communication system performance using silicon photo multipliers (SiPM)
R. M. Gutierrez and A. I. Hernandez
Centro de Investigaciones en Ciencias Básicas y Aplicadas (CICBA), Universidad Antonio Nariño, Bogotá, Colombia
Achieving high speed efficient information rate transfer is a mayor challenge for visible light communications in the presence of back light, due to the difficulty in isolating signal from noise. This paper presents experimental results for communication performance tests of a Visible Light Communication (VLC) system based in a Silicon Photomultiplier (SiPM) receiver, in a relevant environment with the presence of back light and without the need of optical filters. The VLC system was tested for information transfer rate using a white led emitter to recreate environmental background lighting conditions, corresponding to standard office working conditions with lighting complying with international lighting standards for indoor working places. Results are oriented towards a VLC device design, giving useful information to determine adequate relations between emitter power, back light intensity, signal to noise ratio and transfer speed. Our findings show that the capabilities of the tested SiPM based system to operate under back light conditions overcomes the reported performance of former technologies.

Norbert Hanik
Variable data rate for free space optical low earth orbit downlinks (OLEODL)
A. Shrestha1, D. Giggenbach1, and N. Hanik2
1Deutsches Zentrum für Luft und Raumfahrt e.V., Weßling, Germany
2Technische Universität München, Germany

Low-Earth-orbit (LEO) satellites for Earth observation have typical orbit altitudes of 400 to 600km. Since their on-board sensors resolution is advancing, the need for very high rate satellite downlink is increasing to up to several gigabits per second. Free-space optical communication is ideal for such applications, as it offers very high data rate, while allowing smaller satellite terminals and avoiding spectral regulation constraints. However, the key challenges in optical LEO downlinks (OLEODL) are the varying free space loss due to distance changes during a downlink contact, atmospheric attenuation, and the fast signal scintillation due to atmospheric index-of-refraction turbulence (IRT). This paper will briefly explain OLEODL technology, its challenges, and suitable mitigation techniques. The paper will focus on how varying the data rate according to channel state can maintain error-free transmission.

Jan Latal
Simulation and measurement of atmospheric effect on optical beam
J. Latal, J. Vitasek, M. Bojko, J. Skrinsky, T. Stratil, Z. Wilcek, and J. Kolar
VSB-Technical University of Ostrava, Czech Republic

The basic atmospheric phenomena (mainly fog and rain) influencing the optical beams which are generated by laser diodes at wavelengths of 650 and 850 nm will be introduced in this presentation. Also the possibilities of the Software Defined Radio utilization which can create the different types of modulation (M-QAM, M-PSK) and can be used for evaluation of the influences of artificial atmospheric effects on the modulated optical beam in the acrylate box will be presented. The result from the real measurements compared with ANSYS software models will be shown as well.

Erich Leitgeb
Optical wireless communications and optical sensing and detection technologies for increasing the reliability and safety in autonomous driving scenarios
E. Leitgeb2, T. Plank2, P. Pezzei2, H. Ivanov2, and R. Pérez-Jiménez2
1Institute of Microwave and Photonic Engineering, Graz University of Technology, Austria
2IDeTIC, Las Palmas University of Technology, Spain

Among the different types of lasers and light sources for Communications, new components are becoming more and more important also for Optical Wireless and Optical Sensing applications. In this contribution combinations of Optical- and RF-Wave Propagation are illustrated, considering also new technologies of lasers and fibre lasers. The presentation includes Optical Wireless Communication (OWC, well known as Free Space Optics (FSO)) as hybrid transmission methods with telecommunication technologies (like WIFI, RF- and Satellite Communications, and also Sensing Technologies (like LiDAR and radar combinations). The contribution deals with possible fields of application for optical wireless in conjunction with automated driving. The scope considers requirements (including infrastructural view and law), differences of Optical and RF-Wave Propagation and promising combinations of optical techniques with conventional wireless technologies.

Vincenzo Petruzzelli
On-chip wireless optical communication: From antenna design to channel modelling
G. Calò1, G. Bellanca3, F. Fuschini2, M. Barbiroli2, A. E. Kaplan3, M. Bozzetti1, B. Alam1, P. Bassi2, and V. Petruzzelli1
1Department of Electrical and Information Engineering, Polytechnic of Bari, Italy
2Dept. of Electrical, Electronic and Information Eng. “G. Marconi”, University of Bologna, Italy
3Dept. of Engineering, University of Ferrara, Italy
Optical Wireless Networks on-Chip are promising solutions to overcome problems of miniaturization and energy consumption in a multicore on-chip environment. In this paper, we report the results of the design of an integrated plasmonic Vivaldi antenna fed by a silicon waveguide for on-chip wireless connection, which can be easily integrated into optical networks on-chip to achieve a hybrid wired/wireless signal transmission. Moreover, the optical wireless channel is modeled through a ray tracing approach, and the relationship between the optical antennas gain and the communication range in the on-chip propagation environment is investigated.

Jan Vitásek
Illumination and communication characteristics of YAG:Ce phosphor powders
J. Vitasek, J. Jargus, J. Latal, T. Stratil, and Z. Wilček
Faculty of Electrical Engineering and Computer Science, Department of Telecommunications, VSB-Technical University of Ostrava, Czech Republic

This article deals with a comparison of illumination and communication characteristics of white light which is created by excitation of phosphor powder by blue power LED. There are tested two phosphor powders with little different chemical composition. The communication parameters are rise, fall, and photoluminescence decay times. Illumination parameters are colour coordinates and Colour Correlated Temperature. These characteristics are important for VLC technology. The phosphor powders were mixed with Poly-Di-Methyl-Siloxane (PDMS).

Ke Wang
High-speed and secure indoor infrared optical wireless communication technology
Ke Wang1,3, Tingting Song2, Tian Liang2, A. Nirmalathas2, C. Lim2, E. Wong2, Hongtao Li3, K. Alameh4, and E. Skafidas2
1School of Engineering, Royal Melbourne Institute of Technology (RMIT University), Australia
2Department of Electrical and Electronic Engineering, The University of Melbourne, Australia
3School of Electronic and Optical Engineering, Nanjing University of Science and Technology, China

The optical wireless technology has been widely investigated to provide high-speed wireless connectivity in indoor applications. In this paper, our recent progress on high-speed indoor optical wireless communications with enhanced security feature is presented. The high-speed data transmission is achieved by combining limited mobility with the indoor user localisation, and the secure optical wireless link is realised by adding random chaotic phase. Demonstration experiments are carried out and results show that secure high-speed optical wireless communications can be achieved. In addition, the power penalty due to the added random phase security is shown to be negligible. Keywords: optical wireless technology, indoor wireless communications, random phase noise, secure wireless transmissions.

Scott Watson
InGaN/GaN laser diodes and their applications
S. Watson1, S. Gwyn1, S. Viola1, G. Giuliano1, T. J. Slight2, S. Stanczyk3, S. Grzanka3, A. Yadav4, D. Rowe5, L. Laycock5, K. E. Docherty6, E. Rafailov4, P. Perlin3, S. Najda3, M. Leszczynski3, and A. E. Kelly1
1University of Glasgow, School of Engineering, Glasgow, UK
2Compound Semiconductor Technologies Global Ltd, Hamilton, UK
3TopGaN Lasers, Warsaw, Poland
4Aston University, Birmingham, UK
5BAE Systems, Applied Intelligence Laboratories, Great Baddow, Chelmsford, UK
6Kelvin Nanotechnology Ltd, Glasgow, UK

Gallium nitride (GaN) laser diodes are becoming popular sources not only for lighting but for applications ranging from communications to quantum. This paper presents the use of a commercial, off-the-shelf laser diode, with an emission wavelength of 450 nm, for visible light communication, both in free space and for underwater scenarios. Data rates up to 15 Gbit/s have been achieved by making use of orthogonal frequency division multiplexing (OFDM). In addition, distributed feedback (DFB) lasers have been realised emitting at a single wavelength which lend themselves towards applications where high spectral purity is crucial such as atomic clocks or filtered free space transmission systems. These devices have the grating structure etched into the sidewall of the ridge and work is ongoing to measure the linewidth of these lasers with the intended application of cooling Sr+ ions.


PAM invited presentations:

Kyungwon An
Superabsorption as a time-reversal of superradiance
Kyungwon An, Department of Physics and Astronomy, Seoul National University, Korea
We report experimental realization of superabsorption as a time reversed process of superradiance. In contrast to ordinary absorption, the rate of which is proportional to the number of atoms, in superabsorption, the absorption rate is proportional to the square of the number of atoms. Although superradiance has been realized in many systems such as atomic ensemble, solid-state systems and individually-controlled-qubits, superabsorption has not been realized yet. This is mainly because spontaneous emission always makes the collective emission process stronger than the collective absorption process for correlated atoms under normal conditions. In order to overcome this difficulty, we prepare two-level atoms in a superposition state of the ground and excited states with a pre-defined phase so that the atoms would collectively interact with light. By injecting an input field whose phase is opposite to that of the radiation that atoms would emit otherwise, we can then reverse the radiation process to realize the superabsorption. Our experiment is based on the cavity-QED microlaser system employing a beam of two-level atoms (barium-138). A nanohole-array atomic beam aperture fabricated with the focused ion beam technique is used to localize atomic positions for a well-defined phase. The period of the nanohole array is matched with the transition wavelength (791nm) of 1S0-3P1 transition of atomic barium. The latest experimental data and analysis will be presented.

Takehiro Fukushima
Modal interactions in microstadium optical cavities
T. Fukushima, Department of Information and Communication Engineering, Okayama Prefectural University, Japan
The morphological dependence of resonance modes in microstadium optical cavities was investigated numerically using the finite element method by changing the length of the straight segments, which connect two half-circles. Two mechanisms resulting in deformation of the mode patterns were confirmed. One is the morphological effect of the cavity and the other is modal interactions such as mode mixing and mode exchange. When the cavity size is much larger than the resonance wavelength, the modal interactions become prominent due to an increase in the mode density, playing a significant role in the formation process of wave chaotic modes that exhibit very complicated mode patterns in microstadium optical cavities.

Misha Sumetsky
Ultraprecise resonance nanophotonics at the fibre surface
M. Sumetsky, Aston Institute of Photonics Technologies, Aston University, Birmingham, UK
Solution of several exciting problems of modern photonics (e.g., creation of practical miniature slow light devices) is challenged by insufficient fabrication precision and attenuation of light. This presentation reviews recent progress in Surface Nanoscale Axial Photonics (SNAP) which allows to create photonic circuits at the fibre surface with unprecedented sub-angstrom precision and ultralow loss. The propagation of light in SNAP circuits is described by one-dimensional Schrödinger equation and imitates the basic phenomena of quantum mechanics (quantum wells, tunnelling, turning points, etc.) Recent and potential applications of SNAP ranging from miniature optical delay lines, buffers and frequency comb generators to microfluidics are discussed.


PICAW invited presentations:

Alessandro Aimone
Programmable transfer function optical-DAC using an InP segmented Mach-Zehnder modulator
A. Aimone1, S. Dris2, J. Sundermeyer3, Jung Han Choi1, C. Zerna3, A. Richter2, and K.-O. Velthaus1
1Fraunhofer Heinrich Hertz Institute HHI, Berlin, Germany
2VPIphotonics GmbH, Berlin, Germany
3Fraunhofer Institut für Integrierte Schaltungen, Erlangen, Germany

A programmable InP-based Tbit optical-DAC transmitter is discussed. Through electro-optic co-design and simulation of the transmitter’s components, the performance is evaluated. The comparison with a traditional DAC plus linear driver approach is presented, with a significant advantage of the optical DAC for complex modulation schemes. Low power (1.3 pJ/bit) transmission of a 56 Gbaud dual-polarization probabilistically-shaped 256-QAM signal is shown.

Lucio Claudio Andreani
Slow light in waveguide gratings on silicon-on-Insulator platform
M. Passoni1, D. Gerace1, L. O’Faolain2,3, and L. C. Andreani1
1Department of Physics, University of Pavia, Italy
2Centre for Advanced Photonics and Process Analysis, Cork Institute of Technology, Ireland
3Tyndall National Institute, Cork, Ireland

Slow light phenomena have been of considerable interest in recent years because of the fundamental interest in controlling light propagation, and for boosting advanced functionalities in optical devices, especially in photonic integrated circuits on a silicon platform. In this work we present a systematic analysis of slow light properties arising at the band edge in integrated silicon grating waveguides. By employing a combination of numerical methods and perturbation theory, we are able to explore a wide space of parameters with a reasonable computational effort. We show that the slow light bandwidth has a critical dependence on the geometrical structure parameters and that it can be improved by reducing the width of the thinner section in the grating. The best performance is obtained in the limit a thinner section going to zero (i.e., for the lattice of trenches), an optimal compromise is found by considering the requirement that the structure can be connected to a standard silicon waveguide by an adiabatic taper. We also show that the slow-light bandwidth can be further increased by reducing the thickness of silicon in the cladding region.

Laurence Cahill
Optical signal processing based on 4x4 multimode interference structures
Duy-Tien Le, Trung-Thanh Le, and L. W. Cahill
La Trobe University, Melbourne, Australia

All-optical logic gates have attracted considerable attention over the past decade. They have found application as adders, subtractors, header recognizers, parity checkers and in encryption systems. In this paper, we present a new structure based on cascaded 4x4 and 2x2 multimode interference (MMI) couplers for implementing optical XOR, XNOR, NAND and OR logic gates. The emphasis of the design is on optimising bandwidth and fabrication tolerance. Such a design would be useful for optical label swapping and recognition in optical packet switching networks. We use silicon on insulator (SOI) waveguides that are compatible with the CMOS technology, for designing the whole device. The Beam Propagation Method (BPM) and the Eigenmode Expansion Method (EEM) are used for numerical simulations. We show that the contrast ratios for logic 1 and logic 0 for XOR, XNOR, NAND, and OR gates are from 18 dB to 28 dB for a bandwidth of 30 nm, respectively. A large fabrication tolerance of ±500 nm can be achieved by using this structure.

Victor Dolores-Calzadilla
Open innovation development for photonic integration technology: A practical case of RF interconnects
V. Dolores-Calzadilla1, Weiming Yao1, T. de Vries2, and K. Williams3
1Photonic Integration Technology Centre, Eindhoven, The Netherlands
2Nanolab@TUe, Eindhoven, The Netherlands
3Photonic Integration Group, Eindhoven University of Technology, Eindhoven, The Netherlands

Photonic integrated circuit (PIC) platforms are in continuous development to offer higher performance and increased functionality. Through an open innovation model for photonics, developments for next technology nodes can be carried out within a collaborative framework. As an example, we present a case in which we develop low loss radio-frequency interconnects for an InP foundry partner. The technology development is expected to enable high modulation data rates using a generic PIC platform.

Maria Ferreira André
Electro-optic organic-inorganic hybrids for signal modulation
A. R. N. Bastos1-3, C. M. S. Vicente1,2, M. Lima2,3, P. S. André4, and R. A. S. Ferreira1
1Physics Department and CICECO - Aveiro Institute of Materials, University of Aveiro, Portugal
2Instituto de Telecomunicações, University of Aveiro, Portugal
3Department of Electronics, Telecommunications and Informatics, University of Aveiro, Portugal 4Department of Electrical and Computer Engineering and Instituto de Telecomunicações, Instituto Superior Técnico, University of Lisboa, Portugal
Organic-inorganic hybrids have gained considerable attention in the last years as low-cost materials for photonic integrated circuits (PICs). Featuring electro-optic (EO) applications, such as telecommunications switching devices for coherent optical systems, the EO coefficient (r33) was measured by an interferometric methodology. In particular, a Mach-Zehnder interferometer was patterned by direct laser writing in the surface of a di-ureasil siloxane-based organic-inorganic thin film. The measured r33 is 39.9±0.5 pm/V, and the Vp parameter is 2.9±0.3 V. These values resemble those reported for LiNbO3 and silicon-based materials, highlighting the potential of di-ureasil for PICs based on optical modulators, with the additional advantages of easy processing and cost effective approach, to cope with the requirements of the next generation optical access networks.

Robert Halir
Designing anisotropy with waveguide sub-wavelength structures
R. Halir, A. Herrero-Bermello, J. M. Luque-González, A. Ortega-Moñux, G. Wangüemert-Pérez, A. V. Velasco, Í. Molina-Fernández, J. H. Schmid, and P. Cheben
Universidad de Málaga, Spain

Silicon sub-wavelength structures have become a versatile design tool for practical, high-performance integrated optical devices, ranging from highly efficient grating couplers to ultra-broadband beam-splitters. Recently, some of the basic anisotropic properties these structures have proposed for advance device design. Here we explore these properties in detail, from the underlying physics to promising applications in on-chip polarization management.

Christian Koos
Efficient coupling interfaces in photonic systems enabled by printed free-form micro-optics
C. Koos1,2,3, W. Freude1,2, S. Randel2, P.-I. Dietrich1,2,3, M. Blaicher1,2, Y. Xu1,2, M. Billah1,2, T. Hoose1,2, M. Trappen1,2, A. Hofmann4
1Institute of Photonics and Quantum Electronics (IPQ), Karlsruhe Institute of Technology (KIT), Germany
2Institute of Microstructure Technology (IMT), Karlsruhe Inst. of Technology (KIT), Eggenstein-Leopoldshafen, Germany
3Vanguard Photonics GmbH, Eggenstein-Leopoldshafen, Germany
4Institute for Applied Computer Science (IAI), Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany

In this presentation, we give an overview of our recent progress in exploiting direct-write two-photon lithography for additive 3D fabrication of freeform micro-optical elements. These elements can printed with highest precision in direct contact with the facets of photonic integrated circuits or optical fibers, thereby greatly simplifying alignment and improving coupling efficiency. The approach offers new perspectives for a wide variety of applications, ranging from advanced photonic multi-chip modules for high-speed communications and optical sensing to highly efficient astro-photonic systems. We are currently working on transferring the concept from laboratory demonstrations to industrial manufacturing.

Sylwester Latkowski
Test methods and processes in manufacturing chain of photonic integrated circuits
S. Latkowski, D. Pustakhod, Weiming Yao, X. Leijtens, and K. Williams
Institute for Photonic Integration, Eindhoven University of Technology, The Netherlands

Access to fabrication of photonic integrated circuits is enabled via multi-project wafer runs offered by foundries. Such services open a path for proof-of-concept demonstrators and advanced prototypes. However, the technology processes behind those services need extensive developments in order to be scalable and suitable for volume production. Those developments are in a vast part related to test, assembly and packaging across the full PIC manufacturing chain. Standardization and automation of the test methods and equipment is essential for better statistical process control and scalability. When implemented, these will allow for early known-good-die identification, optimization of fabrication process window, improved yield and volume production.  The challenges related to PIC testing will be discussed and current developments in our labs towards standardization and automation of test methods from a design phase to system level functional module evaluation will be presented.

Paulo Marques
Fabrication of monolithic Add-Drop filters in pure silica by femtosecond laser writing
P. V. S. Marques1,2, V. A. Amorim1,2, J. M. Maia1,2, D. Alexandre1,3, and D. Viveiros1,2
1Center for Applied Photonics (CAP), INESC TEC, Porto, Portugal
2Department of Physics and Astronomy, University of Porto, Portugal
3Department of Physics, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal

This talk will review the fabrication of monolithic integrated optical devices by laser direct writing with femtosecond pulsed laser sources, starting with the description of experimental procedures and optimal conditions to fabricate low loss optical waveguides, directional couplers, Y-junctions and first order Bragg gratings by point-by-point writing methods. Finally, the characterization results of a fully operational Add-Drop filter in pure fused silica are described.

Geert Morthier
InP-on-silicon electronically tunable lasers
S. Dhoore, G. Roelkens, and G. Morthier
Photonics Research Group, INTEC, Ghent University-IMEC, Ghent, Belgium

In this paper we present our recent results on heterogeneously integrated InP-on-silicon tunable lasers. DBR-, DFB- and AWG-based laser structures on SOI are discussed. Emphasis is laid on electronically tunable laser types, which can allow for (sub-) nanosecond fast wavelength tuning. The discussed laser devices are expected to find application in future advanced optical networks for intra- and inter-data center communication.

Liam O'Faolain
Thermally stable external cavity laser based on silicon nitride periodic nanostructures
S. Iadanza1,2, A. Bakoz1,2, D. Panettieri2, A. Tedesco3, G. Giannino3, M. Grande1, L. O’Faolain1,2
1Tyndall Institute of Technology, Cork, Ireland
2Cork Institute of Technology, Ireland

3Dipartimento di Ingegneria Elettrica e dell’Informazione (DEI) Politecnico di Bari, Italy
In this paper we demonstrate a thermally stable silicon nitride external cavity (SiN EC) laser based on a 250 µm sized Reflective Semiconductor Optical Amplifier (RSOA) butt-coupled to a series of Si3N4 Bragg gratings acting as wavelength selective reflectors. The laser shows power outputs over 3 mW, a very low lasing threshold of 12 mA and with a typical Side-Mode Suppression Ratio of 45 dB. In this configuration a mode-hop free lasing regime over a range of 47 mA has been achieved (from 15 mA to 62 mA). Thermal stability of the lasing wavelength at temperatures up to 80°C is demonstrated. Further on, experimental results on a passive chip based on new 1D photonic crystal cavities are shown to have higher Q-Factors. This paves the way to avoiding thermal wavelength drifts and unlocks the possibility for these devices to be integrated in Dense WDM and optical-interconnect technologies, where transceivers must operate over a wide temperature range without active cooling.

Joan Ramirez
Ge-rich graded-index SiGe alloys: exploring a versatile platform for mid-IR photonics
J. M. Ramirez1, Q. Liu1, V. Vakarin1, J. Frigerio2, A. Ballabio2, D. Chrastina2, X. Le Roux, C. Alonso-Ramos, G. Isella2, L. Vivien1, and D. Marris-Morini1
1Centre de Nanosciences et de Nanotechnologies, Université Paris Sud, CNRS, Université Paris Saclay, France
2L-NESS, Dipartimento di Fisica, Politecnico di Milano, Polo di Como, Italy

Mid-IR integrated photonics is recently gaining attention due to the wide range of applications foreseen including chemical and biological sensing, thermal imaging, early medical diagnosis or secure communications [1]. Among others, the possibility to use the mature CMOS technology to develop novel photonic integrated circuits exploiting the unique molecular mid-IR absorption bands present in several chemical substances rises as one of the driving forces pushing this research field. This approach would enable ultra-sensitive label-free photonic integrated sensors which could be integrated along with other components in a single photonic chip, hence opening the route towards multifunctional photonic systems. For that, however, a suitable platform capable of integrating several photonic components such as waveguides, Bragg filters, resonators or Mach-Zehnder interferometers should be implemented. Promising mid-IR integrated platforms to carry out this task stand for Ge-on Si, suspended Si or SiGe alloys with tailored Ge concentration, among others [2-4]. This latter approach is expected to offer high versatility and broadband transparency [5], and important photonic building blocks such as low-loss waveguides and wideband Mach-Zehnder interferometers have already been demonstrated in the mid infrared [6, 7]. In spite of the progress achieved so far using SiGe alloys, there are still several open questions that require further exploration, such as the disclosure of the platform transparency bandwidth or the investigation of the nonlinear properties in the mid-IR, taking advantage from the absence of two-photon absorption [8]. Thus, we will present our latest results on the development of a novel mid-IR photonic integrated platform based on Ge-rich graded-index SiGe alloys with compact dimensions. Compact waveguides were fabricated in this platform, showing broadband and flat low-loss propagation of 2-3 dB/cm over a wavelength range from λ = 5.5 µm to 8.5 µm. Moreover, waveguide dispersion engineering was performed to obtain broadband tight mode confinement and flat anomalous condition in the mid-IR [9]. These waveguides show promising features to be used as mid-IR nonlinear optical sources exploiting the third-order nonlinearities for supercontinuum generation [10].
[1] R. Soref, Mid-infrared photonics in silicon and germanium, Nature Photonics, pp. 495-497 (2010).
[2] A. Malik, Germanium-on-silicon mid-infrared arrayed waveguide grating multiplexers, IEEE Photonics Technology Letters, 25(18), 1805-1808 (2013).
[3] Z. Cheng, Mid-infrared suspended membrane waveguide and ring resonator on silicon-on-insulator, IEEE Photonics Journal, 4(5), 1510-1519 (2012).
[4] M. Brun, Low loss SiGe graded index waveguides for mid-IR applications, Optics Express, 22(1), 508-518 (2014).
[5] J. M. Ramirez, et al., Ge-rich SiGe waveguides for mid-infrared photonics, Proc. SPIE 10108 (2017).
[6] J. M. Ramirez, et al., Low-loss Ge-rich Si 0.2 Ge 0.8 waveguides for mid-infrared photonics, Optics Letters 42 (1), 105-108 (2017).
[7] V. Vakarin, et al., Ultra-wideband Ge-rich silicon germanium integrated Mach Zehnder interferometer for mid infrared spectroscopy, Optics Letters, pp. 3482-3485 (2017).
[8] F. De Leonardis, et al., Germanium-on-silicon waveguide engineering for third harmonic generation in the mid-infrared, Journal of Lightwave Technology 33 (24), 5103-5113 (2015).
[9] J. M. Ramirez et al., “Ge-rich graded-index Si1-xGex waveguides with broadband tight mode confinement and flat anomalous dispersion for nonlinear mid-infrared photonics, Optics Express, pp. 6561-6567 (2017).
[10] S. Serna, et al., Nonlinear properties of Ge-rich Si 1− x Ge x materials with different Ge concentrations, Sci. Rep. 7(1), 14692 (2017).

Pablo Sanchis
Transparent conducting oxides for optoelectronics and biosensing applications
J. Parra1, I. Olivares1, J. L. Frieiro2, O. Blázquez2, S. Hernández2, B. Garrido2, and P. Sanchis1
1Nanophotonics Technology Center, Universitat Politècnica de València, Spain
2Departament d’Enginyeries: Secció Electrònica, Universitat de Barcelona, Spain

Transparent conducting oxides have excellent electrical and optical properties that can be exploited to enhance the performance of devices for a large variety of applications such as integrated optoelectronics, biosensing, light detection or resistive memories. In addition, they have also shown the ability to be integrated in silicon CMOS devices and therefore the potential for mass production. In this work, we will focus on ITO and ZnO for different application fields of integrated optoelectronics, memristors and biosensing.

Luigi Sirleto
Towards applications of Stimulated Raman scattering in nanophotonics
L. Sirleto1, M. A. Ferrara1 and A. Vergara2
1Consiglio Nazionale delle Ricerche (CNR), Istituto per la Microelettronica e Microsistemi, Napoli, Italy
2Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte Sant’Angelo, Napoli, Italy
Concerning nanophotonics, one of the most recent challenges is the investigation of ‘nonlinear optical phenomena at nanoscale’. This is a recent fascinating research field of great importance, with significant implications from both fundamental and applicative point of view. Nowadays, photonics components, currently used in optical interconnects, are relatively large and not ideally suited to on-chip integration. A reduction in the size of integrated optical devices, while maintaining a high level of performance, is a key challenge in photonics. On this line of argument, the ability to construct nano-objects is expected to have a significant impact in the future, leading to the development of fully functional nanodevices, such as nanoscale optical sources. The aim of this talk is to review accomplishments in the field of stimulated Raman scattering in nanostructures, to delineate the state of the art, and to identify the emerging trends and remaining challenges [1,2,3].
[1] L. Sirleto, A. Vergara, and M. A. Ferrara, Advances in stimulated Raman scattering in nanostructures, Advanced in Optics and Photonics, vol. 9, no. 1, pp. 169-217, (2017).
[2] L. Sirleto, M. A. Ferrara, and A. Vergara, Toward an ideal nanomaterial for on-chip Raman laser, Journal of Nonlinear Optical Physics and Material, (2017).
[3] L. Sirleto, M. A. Ferrara, T. Nikitin, S. Novikov, and L. Khriachtchev, Giant Raman gain in silicon nanocrystals, Nat. Commun. 3, 1220 (2012).

Isaac Suárez
Polymer halide perovskites-waveguides integrated in nanocellulose as a wearable amplifier-photodetector system
I. Suárez,1,2, E. Hassanabadi2,3, A. Maulu1, N. Carlino4, C. A. Maestri4, M. Latifi3, P. Bettotti4, I. Mora-Seró2, and J. P. Martínez-Pastor1
1UMDO, Instituto de Ciencia de los Materiales, Universidad de Valencia, Spain
2Institute of Advanced Materials (INAM), Universitat Jaume I, Castelló, Spain
3Textile Excellence & Research Centers, Amirkabir University of Technology, Tehran, Iran
4Nanoscience Laboratory, Department of Physics, University of Trento, Povo (TN), Italy

Semiconductor organometallic halide (CH3NH3PbX3, X=Cl, Br, I) perovskites (MHP) have emerged as a very high promising material for optoelectronics. Their large absorption coefficients, high electronic mobilities, excellent quantum yield of emission at room temperature and tunable band-gap with the composition resulted in a new generation of photovoltaics and electronic devices. In this work, HPVK materials are successfully incorporated on a nanocellulose (NC) substrate with the intention to exploit the interesting properties of HPVK materials to construct wearable devices. In particular, a bilayer Poly(methyl methacrylate) /HPVK deposited on NC  resulted in a suitable waveguide to demonstrate amplification of the spontaneous emission (ASE) with a threshold as low as 3-4 nJ.  Moreover, when a photodetector system is integrated within the waveguide, the device provides a photocurrent useful to monitor the light/ASE propagated/generated along the structure. This approximation paves the road of new wearable systems with a broad range of applications.

Dimitris Tsiokos
CMOS-compatible plasmonics integrated with Si3N4 photonic waveguides
D. Tsiokos1, G. Dabos1, A. Manolis1, E. Chatzianagnostou1, D. Ketzaki1, L. Markey2, J.C. Weeber2, A. Dereux2, A. L. Giesecke3, C. Porschatis3, B. Chmielak3, and N. Pleros1
1Center for Interdisciplinary Research and Innovation, Aristotle University of Thessaloniki, Greece
2Laboratoire Interdisciplinaire Carnot de Bourgogne, CNRS-Université de Bourgogne, France
3AMO GmbH, Advanced Microelectronic Center Aachen (AMICA), Germany

Co-integration of CMOS plasmonics and photonics on monolithic chips will pave the way for volume manufacturing of plasmonic-augmented photonic integrated circuits offering new functionalities and unprecedented performances. Plasmonics can naturally interface photonics with electronics while offering strong mode confinement, enabling ultra-compact on-chip data interconnects, as well as high-sensitivity biosensors when exposing Surface-Plasmon-Polariton (SPP) modes in aqueous environments. In this direction, CMOS compatible material platforms and manufacturing processes need to be exploited in order to accelerate practical deployment. In this paper we discuss the progress on the investigation of CMOS-compatible metals including copper, aluminum and titanium nitride, their performance when used in silicon nitride-based SPP waveguides and how those compare to gold, as well as practical examples when such structures are exploited in sensing and optical interconnects applications.

Shogo Ura
Cavity-resonator-integrated guided-mode resonance filters for compact WDM light source
J. Inoue1, S. Ura1, and K. Kintaka2
1Kyoto Institute of Technology, Japan
2National Institute of Advanced Industrial Science and Technology, Japan

A cavity-resonator-integrated guided-mode resonance filter (CRIGF) consisting of a grating coupler (GC) with a waveguide cavity resonator on a transparent substrate shows a narrowband reflection spectrum for a vertically incident free-space wave of a small diameter. CRIGF can act as not only a wavelength-selective reflector but also an input waveguide coupler. Integration of such CRIGFs for different wavelengths in a waveguide is proposed to give an array of external mirrors and a wavelength division multiplexer for constructing a compact multi-wavelength light source. Four CRIGFs of 10-μm-size aperture with a wavelength spacing of 15 nm were designed and fabricated. CRIGF integrated on a reflective layer via an optical buffer layer is also discussed. Optimization of buffer-layer-thickness is theoretically investigated to maximize a waveguide-coupled lasing power.


Quantum Photonics invited presentations:

Daryl Beggs
Integrated quantum photonics in compound semiconductors
D. Beggs, University of Cardiff, UK

Mark Fox
On-chip quantum photonics using integrated quantum dot emitters
A. M. Fox, Department of Physics and Astronomy, University of Sheffield, UK
On-chip quantum photonics relies on the integration of efficient single-photon sources with advanced quantum-optical circuits. In this presentation, I will review progress at the University of Sheffield on a chip-compatible III-V semiconductor platform in which InGaAs quantum-dot (QD) single-photon emitters are integrated into GaAs photonic circuits. The presentation will have two parts. I will first discuss progress towards the generation of highly coherent indistinguishable photons by using the Purcell effect to enhance the radiative decay rate for an InGaAs QD coupled to an H1 photonic crystal nano-cavity [1]. Under resonant π-pulse excitation, an on-chip, on-demand single-photon source with a radiative lifetime of 22.6 ps has been demonstrated that exhibits high purity and indistinguishability without spectral filtering. In a related experiment on a dot coupled to a photonic crystal waveguide, a resonant transmission dip of 40% has been measured, indicting very high coupling to the waveguide mode and low decoherence [2]. In the second part of the presentation, I will discuss chiral coupling between QDs and nano-photonic waveguides in which both chiral emission and exciton spin initialization has been demonstrated [3,4]. In the most recent work, non-reciprocal transmission has been measured, and explained by a model that incorporates realistic parameters for the dot [5]. These results rely on the precise positioning of dot within the nano-photonic structure, and lay the foundations for developing on-chip spin networks with spin qubits localized in different QDs.
[1] F. Liu, A. J. Brash, J. O’Hara, L. M. P. P. Martins, C. L. Phillips, R. J. Coles, B. Royall, E. Clarke, C. Bentham, N. Prtljaga, I. E. Itskevich, L. R. Wilson, M. S. Skolnick, and A. M. Fox, "High Purcell factor generation of coherent on-chip single photons," arXiv 1706.04422.
[2] D. Hallett, A. P. Foster, D. L. Hurst, B. Royall, P. Kok, E. Clarke, I. E. Itskevich, A. M. Fox, M. S. Skolnick, and L.R. Wilson, "Electrical control of nonlinear quantum optics in a nanophotonic waveguide," arXiv 1801.09958.
[3] R. J. Coles, D. M. Price, J. E. Dixon, B. Royall, E. Clarke, P. Kok, M. S. Skolnick, A. M. Fox, and M. N. Makhonin, "Chirality of nanophotonic waveguide with embedded quantum emitter for unidirectional spin transfer," Nat. Commun. 7, 11183 (2016).
[4] R. J. Coles, D. M. Price, B. Royall, E. Clarke, M. S. Skolnick, A. M. Fox, and M. N. Makhonin, "Path-dependent initialization of a single quantum dot exciton spin in a nanophotonic waveguide," Phys. Rev. B 95, 121401 (2017).
[5] D. M. Price, D. L. Hurst, C. Bentham, M.N. Makhonin, B. Royall, E. Clarke, P. Kok, L. R. Wilson, M. S. Skolnick, and A. M. Fox, "Non-reciprocal transmission and reflection of a chirally-coupled quantum dot," arXiv 1711.00652.

Stephen Lynch
Giant Rydberg excitons in synthetic and artificial cuprous oxide
S. A. Lynch1, C. Hodges1, W. W. Langbein1, L. Gallagher2, J. Rogers2, C. S. Adams2, M. P. A. Jones2, and R. P. Singh3
1School of Physics and Astronomy, Cardiff University, UK
2Department of Physics, Durham University, Durham, UK
3Department of Physics, Indian Institute of Science Education and Research (IISER) Bhopal, India

In this paper, we report on our recent studies of giant Rydberg excitons in cuprous oxide (Cu2O). Cuprous oxide exhibits an extraordinary exciton spectrum near its 2.17 eV band edge. Unlike most semiconductors, excited states with principal quantum number up to n = 25 have been observed. This contrasts with more conventional semiconductors, where it is common to observe principal quantum numbers up to n = 5. Such large principal quantum numbers imply macroscopic quantum objects that might be harnessed for a host of different quantum technology applications. Until recently, the highest principal quantum number excitons had only been observed in natural cuprite gemstone material recovered from a small number of mines in Africa. We reported cuprous oxide excitons in similar gemstone material with principal quantum numbers up to n = 15 at this conference in 2017. Recently, we have observed excitons in synthetic cuprous oxide. The single crystal material was grown by the optical float zone technique. X-ray characterisation confirms that the material is mostly single crystal. Our first optical characterisation has been promising, and we have observed excitons with similarly large principal quantum numbers seen in natural gemstone material. Our results are particularly important because they indicate a real technological pathway for this extraordinary material.

Khaled Mnaymneh
Integrated quantum photonics using single InAs quantum dots in tapered InP nanowires
K. Mnaymneh, D. Dalacu, J. McKee, J. Lapointe, P. J. Poole, S. Haffouz, G. C. Aers, and R. L. Williams
National Research Council Canada, Quebec, Canada

We present our progress towards the generation and routing of non-classical light sourced by single semiconductor quantum dot nanowire waveguides coupled to conventional integrated photonic circuity. Single InAs quantum dots are nucleated in vertically grown InP nanowire waveguides. After growth, pick-and-place techniques of these nanowires can be used for placement on a variety of integrated photonic material platforms. Optical coupling of single dot emission from the nanowires to chip-based waveguide circuitry is achieved by the nanowire’s taper design established during the epitaxial growth of the dot-nanowire system. Our work facilitates the ability to convert pre-fabricated conventional integrated photonics to quantum photonic fiber-coupled chips that target applications in quantum information processing in local and global optical networks.

Wolfram Pernice
Cavity-enhanced superconducting single photon detectors
J. Münzberg1, A. Vetter1, W. Hartmann2, N. Gruhler2, F. Beutel2, S. Ferrari2, C. Rockstuhl1, W. H. P. Pernice2
1Institute of Theoretical Solid State Physics, Karlsruhe Institute of Technology (KIT), Germany
2Institute of Physics, University of Münster, Germany
The advent of quantum optics and quantum information processing goes hand in hand with the search for adequate active and passive components operating on the single-photon level at telecommunication wavelengths. Among a variety of approaches, a hybrid arrangement of integrated single-photon sources, reconfigurable photonic circuitry, and detectors on a single chip is particularly promising with respect to complexity, compactness, reproducibility, stability, and ease of fabrication. While a multitude of detection technologies are currently investigated, waveguide-integrated superconducting nanowire single-photon detectors stand out due to their near-unity detection efficiencies at outstanding timing accuracy and speed. Here, by exploiting the concept of critical coupling, we present the integration of a short nanowire into a two-dimensional double heterostructure photonic crystal cavity to realize an integrated single-photon detector with excellent performance metric. The complete detector characterization reveals on-chip detection efficiencies of almost 70% at telecom wavelengths, recovery times of 480 ps, and vanishingly low dark count rates. Compared to photonic crystal nanobeam cavities, our overhauled design approach reduces out-scattering losses and can readily be combined with single-photon emitters integrated into on-chip cavities. Our silicon photonics approach paves the way for the implementation of compact on-chip detector arrays and time-multiplexed single-detector schemes.

Eilon Poem-Kalogerakis
Fast, noise-free memory for photon synchronization at room temperature
E. Poem, R. Finkelstein, O. Michel, O. Lahad, and O. Firstenberg
Weizmann Institute of Science, Israel

Future quantum photonic networks require coherent optical memories for synchronizing quantum sources and gates of probabilistic nature. Room temperature operation is also desirable for ease of scaling up. Until now, however, room-temperature atomic memories have suffered from an intrinsic read-out noise due to spontaneous four-wave-mixing. Here we demonstrate a new scheme for storing photons at room temperature, the fast ladder memory (FLAME). In this scheme, stimulated two-photon absorption is used instead of the previously used stimulated Raman scattering. As here the competing spontaneous processes would require spontaneous absorption of an optical photon, rather than emission, the noise is greatly suppressed. Furthermore, high external efficiency is achieved as the control is well separated in frequency from the signal, and could be filtered out using highly efficient interference filters. We run the protocol in both cesium [1] and rubidium [2] vapour, and both on and off single-photon resonance. In [1] we show that stored and retrieved single photon from a down-conversion source completely preserve their non-classical statistics, while in [2], working with weak classical light, we demonstrate very low noise levels, high external efficiency, and a high ratio of storage time to signal pulse width. These experiments pave the way towards the efficient synchronization of probabilistic gates and sources at room temperature, and the controlled production of large quantum states of light.
[1] K. T. Kaczmarek, et al., arXiv:1704.00013 (2017).
[2] R. Finkelstein, et al., Science Advances 4, eaap8598 (2018).

Ruth Oulton
Tamm plasmons and confined Tamm plasmons coupled to telecom wavelengths quantum dots
E. Harbord1, M. Parker2, P. Androsanvitaneas1, A. Young1, E. Clarke3, J. Rarity1, and R. Oulton1,2
1Department of Electrical and Electronic Engineering, University of Bristol, UK
2HH Wills Physics Laboratory, University of Bristol, UK
3EPSRC National Centre for III-V Technologies, University of Sheffield, UK

Quantum dots (QDs) – semiconductor nanostructures confined in all 3 dimensions – are attractive not only as single photons sources (SPS) but also as a gain medium for lasers. They possess close-to-unity internal quantum efficiency. However, practical applications require photonic structures to produce a high external quantum efficiency, and to shape the optical mode of the emitting light. We investigate the Tamm plasmon structure, in which light is confined vertically between a distributed Bragg reflector (DBR) and a thin metallic layer. By patterning the metal on the surface, it is possible to confine the light laterally, forming a confined Tamm plasmon (CTP). This is an ideal way of creating a confined optical state without etching into the semiconductor and forming surface states at the processed interfaces. Our previous work [1] presented a design for telecom wavelength Tamm plasmons to couple to quantum dots. Here, we have realised these designs and measured Tamm plasmon structures coupling high areal density (2 x 1010 cm-2) QDs that emit in the O band at room temperature. We have demonstrated Tamm plasmon emission from the coupled QD, with a 6-fold enhancement of the emission intensity. By using e-beam lithography and evaporative deposition, we also deposit size controlled disks to confine the light laterally. By Fourier microscopy of the emission, we obtain evidence for confinement of the optical mode. These results pave the way for using Tamm plasmons and QDs for telecom wavelength lasers and SPS.
[1] Parker et al., IET Optoelectron., 2018, vol. 12, no. 1, pp. 11-14.

Döndü Sahin
Superconducting single photon detectors for integrated quantum photonics
D. Sahin, M. H. Johnson, B. Slater, N. A. Tyler, J. G. Barreto, and M. G. Thompson
University of Bristol, UK

Single photon detectors based on thin superconducting nanowire are promising for quantum technologies with their unprecedented performance in detection efficiencies, dark count rates, jitter and dead times. We studied nanowire detectors within a ring cavity with the detection efficiency exceeding 95%. With a transmission loss smaller than 0.05 dB and a crosstalk of -28 dB, these detectors can be fabricated in the ring cavity and they are promising to increase the yield for detectors based on crystalline superconductor materials. In addition, their adjustable bandwidth with narrow spectral response is suitable for single photon spectrometers.

Grzegorz Sęk
Recent developments in quantum-dot-based single photon sources at telecom wavelengths
A. Musiał, P. Mrowiński, Ł. Dusanowski, and G. Sęk
OSN Lab, Department of Experimental Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wrocław, Poland

The fully secure communication systems require true single-photon sources (SPS) at wavelengths compatible with existing fibre networks. Nowadays, the efforts are especially devoted to improvement of quantum emitters’ performances and realization of practical devices. In this contribution, there are overviewed the recent achievements in the development of quantum dot (QD)-based SPS in two different material systems of InGaAs/GaAs suitable for 1.3 µm and InAs on InP for 1.3 – 1.55 µm spectral range. The issues of improving the single photon emission purity and their temperature stability are elaborated in view of the underlying physics of excitonic complexes confined in such nanostructures. Placing QDs in photonic structures for controlling the emission extraction efficiency and prospects for realization of compact, cryogenic-free sources operating at telecom wavelengths are also addressed.

Miguel Urbaneja Torres
Radiated fields by polygonal core-shell nanowires
M. A. Urbaneja Torres1, A. Sitek1,2, V. Gudmundsson3, and A. Manolescu1
1School of Science and Engineering, Reykjavik University, Iceland
2Department of Theoretical Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Technology, Poland
3Science Institute, University of Iceland, Reykjavik, Iceland

We calculate the electromagnetic field radiated by tubular nanowires with prismatic geometry and infinite length. The polygonal geometry has implications on the electronic localization; the lowest energy states are localized at the edges of the prism and are separated by a considerable energy gap from the states localized on the facets. This localization can be controlled with external electric or magnetic fields. In particular, by applying a magnetic field transverse to the wire the states may become localized on the lateral regions of the shell, relatively to the direction of the field, leading to channels of opposite currents. Because of the prismatic geometry of the nanowire the current distribution, and hence the radiated electromagnetic field, have an anisotropic structure, which can be modified by the external fields. In this work we study hexagonal, square and triangular nanowires.

Jürgen Volz
Multimode strong coupling of laser-cooled atoms to a nanofiber-based ring resonator
J. Volz1, A. Johnson1, M. Blaha1, A. Ulanov1, P. Schneeweiss1, and A. Rauschenbeutel1,2
1Vienna Center for Quantum Science and Technology, Atominsititut, TU Wien, Austria
2Institut für Physik, Humboldt-Universität zu Berlin, Germany

Coupling neutral atoms to nanoscale waveguides is a promising approach for realizing light-matter quantum interfaces. In combination with resonator enhancement of the guided light, such systems provide powerful tools for a broad range of applications. They even allow one to reach and study new paradigms of light-matter interaction such as the multimode strong coupling regime of resonator quantum electrodynamics (QED), where the atom-resonator interaction strength exceeds the free spectral range of the resonator. In my talk, I will present our current experimental status on the realization of such a novel type of resonator QED system, where we interface a fiber-ring-resonator that contains a nanofiber-part with an ensemble of laser-cooled cesium atoms from a magneto-optical trap.


RONEXT invited presentations:

Vincent Chan
Resilient optical networks
V. W. S. Chan, Massachusetts Institute of Technology, Claude E. Shannon Communication and Network Group, Research Lab of Electronics, Cambridge, USA
Networking resilience is the ability to provide and maintain an acceptable level of service, albeit potentially degraded from nominal, in the face of faults and challenges to normal, including adversarial attacks. This paper explores the concept of resilient optical networks and scopes the important issues to be addressed in a sensible architecture. The solution includes monitoring and probing to determine the states of potentially unreliable network substrates, assessment of resilient network operating regimes, isolation of compromised assets, deployment of mitigation measures that may require communication over unreliable substrates and suggestions for resilient architecture design and improvement. The architecture construct evolves around a robust control plane that uses cognitive techniques to assess network states and automatically reacts to the on-set of impairments and attacks involving all the network layers from the Physical Layer to the Application Layer.

Rebecca Chandy
Reliability of optical components in advanced manufacturing
R. Chandy, European Union Project Partner, Manchester, UK

Camille Delezoide
Pre-emptive detection and localization of failures towards marginless operations of optical networks
C. Delezoide1, K. Christodoulopoulos2, A. Kretsis2, N. Argyris3, G. Kanakis3, A. Sgambelluri4, N. Sambo4, P. Giardina5, G. Bernini5, D. Roccato6, A. Percelsi6, R. Morro6, H. Avramopoulos3, E. Varvarigos2, P. Castoldi4, P. Layec1, and S. Bigo1
1Nokia Bell Labs, Nozay, France
2CTI, Patras, Greece
3NTUA, Athens, Greece
4Scuola Superiore Sant’Anna, Pisa, Italy
5Nextworks, Pisa, Italy
6TIM, Turin, Italy

Operating optical networks much closer to their physical capacity is very tempting but necessarily requires much improvement on the way failures are handled. In this paper, we experimentally demonstrate the ability of the ORCHESTRA solution for early detection and localization of failures, to proactively mitigate their impact and thus guarantee smooth operation without traffic interruption.

Andrea Fumagalli
Combining electronic layer protection and pre-planned optical restoration for improved and resource-efficient reliability
Zhen Lu1, A. Shakeri1, M. Razo1, M. Tacca1, A. Fumagalli1, G. M. Galimberti2, and G. Martinelli2
1Open Networking Advanced Research (OpNeAR) Lab, UT Dallas, USA
2Cisco Photonic, Vimercate, Italy

Wavelength Division Multiplexing (WDM) backbone networks are prone to failures of components such as network fiber, sites, and ports. Even a single network element failure can cause significant traffic loss due to the disruption of many active data flows. Therefore, it is imperative that these networks be fault-tolerant. Fault tolerance refers to the ability of the network to reconfigure and re-establish active data flows affected by an outage. Fault tolerance may be achieved through the use of restoration schemes [1, 2]. To guarantee successful recovery and reduce network traffic and service disruption time during network outages, pre-planned restoration schemes offer the advantage of ensuring readily available resources for provisioning backup paths under certain conditions. In pre-planned restoration, a backup path is computed and its required network resources reserved at the time when the primary path itself is provisioned in the network [1, 2]. For an efficient use of resources, wavelengths and other resources may be shared by multiple backup paths so long as their corresponding primary paths are not in the same Shared-Risk Link Group (SRLG) [3, 4]. It is well-known that in single layer (optical) network such shared restoration schemes effectively reduce the capacity overhead that is necessary to achieve restoration [3, 4]. In this study the authors investigate the efficiency of pre-planned restoration in a two-layer network, consisting of Multiprotocol Label Switching (MPLS) over WDM. In this architecture, the MPLS layer implements a fast reroute (FRR) protection scheme, while the optical layer underneath implements pre-planned restoration of lightpaths. This architecture is increasingly gaining traction due to its offered extra reliability against multiple failures and reduced resource overhead at the optical layer, which is required to achieve said objective.
[1] G. Mohan and C. S. R. Murthy, Lightpath restoration in WDM optical networks, IEEE Network, 2000, pp. 24-32, vol. 14.
[2] G. Mohan and A. K. Somani, Routing dependable connections with specified failure restoration guarantees in WDM networks, IEEE INFOCOM, 2000, pp. 1761-1770, vol. 3.
[3] G. Mohan and C. S. R. Murthy, " Routing and wavelength assignment for establishing dependable connections in WDM networks", IEEE FTCS. 1999, pp. 94-10.
[4] S. Datta, S. Sengupta, et al., Efficient channel reservation for backup paths in optical mesh networks, IEEE GLOBECOM, 2001, pp. 2104-2108, vol. 4.

Ricardo Martínez
Integrated OAM and transport SDN architecture for automatic and dynamic restoration of signal-degraded connections within flexi-grid optical networks
R. Martínez1, R. Casellas1, J. M. Fàbrega1, R. Vilalta1, R. Muñoz1, F. J. Vilchez1, L. Nadal1, M. Svaluto Moreolo1, A. Villafranca2, and P. Sevillano2
1Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Castelldefels (Barcelona), Spain
2Aragon Photonics Labs, S. L., Zaragoza, Spain

The programmability of upcoming transport optical networks is handled by a centralized Transport SDN (T-SDN) controller. For each received optical demand specifying a set of requirements (e.g., bandwidth, latency, etc.), the T-SDN controller dynamically computes and selects the resources to accommodate such as request as well as coordinates the configuration of the involved network elements and devices (i.e., optical switches and transceivers). Additionally, the T-SDN controller should provide management functions to ensure high reliability and correct service status in terms of QoS, QoT, failure detection, etc. during the whole connection duration. These management functions are typically addressed by the operation, administration and maintenance (OAM) Handler. Thereby, the OAM Handler interacts with the monitoring system to gather notifications about connection failures or degradations and trigger the required actions to preserve / recover the services. Focusing on the above framework, this work first overviews the designed and implemented architecture integrating required OAM functions into a deployed T-SDN controller for flexi-grid optical networks. Next, two algorithms for restoring signal-degraded optical connections are presented and discussed. Finally, an exhaustive performance evaluation with respect to different figures of merit such as the blocked bandwidth ratio, restorability and average number of used sub-transceivers is conducted. To this end, both algorithms are benchmarked varying not only the connection request inter-arrival and its duration but also the generation of signal degraded events of existing connections forcing the automatic restoration of them.

Jose Marzo
Resilient controller location under targeted attacks
S. Gomez-Cosgaya, E. Calle, and J. L. Marzo
Universitat de Girona, Spain
Target attacks in telecommunication networks can disrupt the connectivity and services offered. One of the worst scenarios occurs when these attacks are able to broke the networks in different pieces/islands. Moreover, if the network is managed by a low number of controllers (which is the common case) these controllers could become isolated from the rest of the network causing a disruption in the service availability. We analyses different target attack scenarios and propose a more robust strategy to locate the controllers preserving the desired service availability level.

Paolo Monti
A proactive restoration strategy for optical cloud networks based on failure predictions
C. Natalino1, F. Coelho2, G. Lacerda2, A. Braga2, L. Wosinska1, and P. Monti1
1Optical Networks Laboratory (ONLab), KTH Royal Institute of Technology, Stockholm, Sweden
2Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil
Failure prediction based on the anomaly detection/forecasting is becoming a reality thanks to the introduction of machine learning techniques. The orchestration layer can leverage on this new feature to proactively reconfigure cloud services that might find themselves traversing an element that is about to fail. As a result, the number of cloud service interruptions can be reduced with beneficial effects in terms of cloud service availability.  Based on the above intuition, this paper presents an orchestration strategy for optical cloud networks able to reconfigure vulnerable cloud services (i.e., the ones that would be disrupted if a predicted failure happens) before an actual failure takes place. Simulation results demonstrate that, with a single link failure scenario, proactive restoration can lead to up to 97% less cloud services having to be relocated. This result brings considerable benefits in terms of cloud service availability, especially in low load conditions. It is also shown that these improvements come with almost no increase in the cloud service blocking probability performance, i.e., resource efficiency is not impacted.

Hussein Mouftah
Implementing CoS in EON protection and restoration schemes to preserve network resources
M. Stapleton, K. Maamoun, and H. T. Mouftah
School of Electrical Engineering and Computer Science, University of Ottawa, Canada

Elastic Optical Networks (EON) provide an opportunity to efficiently utilize spectrum and resources. In this paper, a novel approach to implementing protection and restoration in EON is proposed by extending current schemes to Network Media Channels (NMC) and incorporating class of service.

Eiji Oki
Performance of hitless defragmentation scheme in quasi 1+1 path protected elastic optical networks
B. C. Chatterjee1,2 and E. Oki3
1Indraprastha Institute of Information Technology, New Delhi, India
2Norwegian University of Science and Technology, Trondheim, Norway
3Kyoto University, Japan
This paper analyses the performance of the defragmentation scheme using path exchanging in 1+1 path protected elastic optical networks (EONs), which is intended to improve the traffic admissibility in the network. The path function of the 1+1 protection is exchanged with the primary to the backup state while the backup becomes the primary by the toggling operation. This allows both lightpaths to be reallocated during the defragmentation process while they work as backup. The defragmentation scheme based on path exchanging offers a hitless defragmentation of the spectrum by applying hitless path protection switching. The simulation results show that the defragmentation scheme based on path exchanging outperforms the conventional one and improves the total admissible traffic in the network. If the required time for reallocation of backup paths and the toggling operations between primary and backup paths is minimized, the performance of the defragmentation scheme is improved.

Silvia Pato
Capacity increase and hardware savings in DWDM networks exploiting next-generation optical line interfaces
J. Pedro1,2 and S. Pato1,3
1Coriant Portugal, Amadora, Portugal
2Instituto de Telecomunicações, Instituto Superior Técnico, Lisboa, Portugal
3Instituto de Telecomunicações, DEEC, Universidade de Coimbra, Portugal

In transport networks, each generation of optical line interfaces brings the prospect of even higher capacity and further reductions in the cost per bit transported. Currently deployed line interface technology already exploits coherent detection and advanced modulation formats to attain high spectral efficiency as well as to flexibly adapt the modulation format to the path characteristics, effectively trading-off capacity for reach. The upcoming generation of optical line interfaces will take these capabilities one step further by enriching the set of modulation formats supported and by doubling the maximum symbol rate at which each line interface can operate. This work presents a preliminary assessment of the network-wide benefits of deploying next-generation line interfaces. Considering two reference transport networks and modelling three different sets of channel formats, which approximately match three consecutive generations of line interface technology, a full design of the network is reported. The network simulation results highlight the capacity increase and the line interface and tributary card savings enabled by the upcoming generation of line interfaces.

Armando Pinto
Generation and distribution of oblivious keys through quantum communications

A. N. Pinto1,2, M. F. Ramos1,2, N. A. Silva1,2, N. J. Muga1,2
1Depart. of Electronics, Telecommunications, and Informatics, University of Aveiro, Portugal
2Instituto de Telecomunicações, Campus de Santiago, Aveiro, Portugal

Oblivious keys are a fundamental resource to support secure multiparty computation. Nevertheless, they are extremely hard to generate due to the high required computational complexity, which have been hindered their utilization. However, using quantum communications they can be generated and distributed with an efficiency similar to secret symmetric keys. This can allow the generalization of applications supported by secure multiparty computation. In this work, we discuss the generation and distribution of oblivious keys using fiber optics technologies. We present a protocol able to generate and distribute oblivious keys and we also present results of its implementation over standard fiber optics.

Marco Tacca
An improved analytical model for the estimation of blocking probability in WDM networks with first-fit wavelength assignment
Tianliang Zhang, A. Samadian, A. Shakeri, M. Razo, M. Tacca, and A. Fumagalli
The University of Texas at Dallas, Richardson, USA

Wavelength Division Multiplexing (WDM) optical networks are often operated using first-fit (FF) wavelength assignment algorithms. In a mesh topology, these FF algorithms have the advantage of reducing wavelength fragmentation in the network links. Unfortunately, analytically quantifying the blocking probability due to fragmentation and lack of wavelength availability is a challenging problem when using the FF wavelength assignment algorithm. Contributing to the model complexity are two factors: the traffic peakedness which is wavelength dependent, and the strong dependency of wavelength availability between link pairs. The former is caused by incoming lightpath requests which overflow from wavelength to wavelength in the order chosen by the FF algorithm. The latter is caused by the wavelength continuity constraint, which must be satisfied in order to avoid the use of costly wavelength converters. In this paper, the authors present an approximate analytical model, which takes both factors into consideration while estimating the blocking probability in a WDM network that operates with a fixed routing scheme, FF wavelength assignment algorithm, and wavelength continuity constraint. The results show that the model can accurately estimate the blocking probability in WDM networks. The model is then applied to estimate the performance gap between two fixed routing schemes, one minimizing the lightpath hop count, and the other minimizing the lightpath signal to noise ratio at the receiver.

Gangxiang (Steven) Shen
Upgrading links with ultra-low loss fibers in a survivable elastic optical network
Yongcheng Li, Kai Xu, Xiaodong Fu, Sanjay K. Bose, and Gangxiang Shen
School of Electronic and Information Engineering, Soochow University, Suzhou, China

The lifespan of a fiber cable is generally limited, typically 20 years. Thus, it is foreseen that there will be a large number of fiber cables expired and requiring to be upgraded in the near future since many fiber cables were deployed in the last century. Ultra-low loss (ULL) fibers promise enhanced transmission performance, which has therefore been considered as an important candidate for replacing old standard single mode fibers (SSMFs). However, upgrading all the fibers in a network in one go will not only be prohibitively costly but will also be difficult to undertake because of the usually limited labor resources. Network operators are expected to upgrade only a partial set of network links at a time, in order to change over progressively to ULL fibers. Thus, how to upgrade network links with ULL fibers efficiently is important to investigate. In this paper, we address this problem for a survivable elastic optical network (EON). We consider three different fiber upgrading strategies – random, physical length based (PL), and least cost based (LC) strategies. We consider the routing, modulation format, and spectrum assignment (RMSA) problem for an EON with partially upgraded fiber links, aiming to minimize the number of frequency slots (FSs) used. The RMSA problem is formulated as a mixed integer linear programming (MILP) model. And also for handling large-size networks, a spectrum window plane (SWP) based heuristic algorithm is developed to incorporate the steps of ULL fiber upgradation and RMSA. Studies show that the number of FSs used decreases when the total link distance replaced increases, and a ULL fiber with a 0.168 dB/km attenuation coefficient is sufficient to achieve good performance and further reducing the coefficient would not bring much performance improvement.

Xuelin Yang
Key generation and distribution using phase fluctuation in classical fiber channel
A. A. E. Hajomer, Xuelin Yang, A. Sultan, Weiqiang Sun, and Weisheng Hu
State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong University, China

We propose a secure key generation and distribution scheme for data encryption in classical optical fiber channel. A Delay interferometer (DI) is used to track the random phase fluctuation inside fiber, while the reconfigurable lengths of polarization-maintaining (PM) fiber are set as the source of optical phase fluctuations. The output signals from DI are extracted as the secret key and shared between the two-legal transmitter and receiver. Because of the randomness of local environment and the uniqueness of fiber channel, the phase fluctuation between orthogonal polarization modes (OPMs) can be used as secure keys to enhance the level of security in physical layer. Experimentally, we realize the random key generation and distribution over 25-km standard single-mode fiber (SSMF). Moreover, the proposed key generation scheme has the advantages of low cost, compatible with current optical fiber networks and long distance transmission with optical amplifiers.


SDM invited presentations:

Pierpaolo Boffi
Impact of crosstalk in SDM short-reach systems in presence of multicarrier transmission
M. Rapisarda, A. Gatto, P. Parolari, and P. Boffi
Politecnico di Milano, Dept. Electronics, Information and Bioengineering – PoliCom Lab, Italy

The effect of the coherent crosstalk in space-division multiplexed (SDM) optical systems is investigated both with simulations and experimentally. Short-reach links based on direct detection are taking into account with multiple-subcarrier modulated signals propagating in few-mode fibers or in multi-core fibers. The limitations induced by the signal beating among the different mode/core channels is evaluated. Countermeasures are proposed, also with suitable experimentation.

George Ellinas
Connection provisioning in spectrally-spatially flexible optical networks with physical layer considerations
G. Savva, K. Manousakis, B. Shariati, I. Tomkos, and G. Ellinas
Department of Electrical and Computer Engineering School of Engineering University of Cyprus, Nicosia, Cyprus

This paper presents efficient connection provisioning techniques for spatial division multiplexed (SDM) flexible grid optical networks utilizing multicore fibers (MCFs) when physical layer effects are taken into consideration. Resource utilization, complexity, and blocking probability metrics are considered during the design of the provisioning techniques while also accounting for quality-of-transmission (QoT) considerations.

Ruben Luís
Recent advances using homogeneous single-mode multicore fibers for spatial division multiplexing
R. S. Luis, G. Rademacher, B. J. Puttnam, Y. Awaji, and N. Wada
Photonic Network System Lab., National Institute of Information and Communications Technology (NICT), Tokyo, Japan
We revise the latest advancements on the use of homogeneous single-mode multicore fibers for long distance and/or ultra-high capacity spatial-division multiplexing transmission systems. Also, we review the limitations imposed by inter-core crosstalk on these systems as well as techniques to overcome them, such as high-order multiple input-multiple output mechanisms.

Paolo Martelli
Crosstalk-induced penalty in coherent space-division multiplexing transmission
P. Martelli and P. Boffi
Politecnico di Milano, Dipartimento di Elettronica Informazione e Bioingegneria, PoliCom Lab, Italy

The impairment due to the in-band crosstalk on space-division multiplexing (SDM) coherent transmission is evaluated in terms of optical-signal-to-noise-ratio (OSNR) penalty. The reaches for optically-amplified SDM medium-long distance coherent systems are then calculated. Different quadrature-amplitude modulation (QAM) formats are considered.

Nelson Muga
Optical and digital key enabling techniques for SDM-based optical networks
N. J. Muga1,3, G. M. Fernandes1,2, M. J. N. Lima1, A. N. Pinto1,2, P. B. André4, M. Facão3, and A. M. Rocha1,3
1Instituto de Telecomunicações, Aveiro, Portugal
2Department of Electronics, Telecommunications, and Informatics, University of Aveiro, Portugal
3i3N Aveiro, Portugal
4Department of Electrical and Computer Engineering, Instituto Superior Técnico, University of Lisboa, Portugal

In order to support, in a cost-effective way, the optical backhaul data capacity required by future 5G networks new and advanced technologies need to be explored, as it is the case of spatial division multiplexing (SDM) along with energy efficient coherent detection based modulation formats. This paper presents the recent results on enabled optical networks based on spatial division multiplexing for optical backhaul in 5G network infrastructure and data center connectivity. In particular, we present and characterize the performance of different digital signal processing (DSP) algorithms for very high capacity optical coherent systems employing SDM, and show results on advanced modulation techniques for optical free-space connections.

Karsten Rottwitt
Nonlinear optical signal processing and generation of quantum states using intermodal four-wave mixing
K. Rottwitt, M. A. U. Castaneda, E. N. Christensen, J. B. Christensen, and J. G. Koefoed
Department of Photonics Engineering, Technical University of Denmark, Lyngby, Denmark

The strong interest in space-division multiplexing of classical communication signals has resulted in development of optical fibers that support propagation of multiple modes. This has paved the way for progress in signal processing using multiple modes and four-wave mixing between these. More specifically, careful design and knowledge of optical properties of individual modes enables phase matching in four-wave mixing that is otherwise not possible with single-mode fibers. This enables signal processing using four-wave mixing between higher-order modes for e.g. frequency conversion over a wide bandwidth. In addition, processing and creation of quantum states has also been demonstrated using four-wave mixing, including generation of photon pairs. In this work we review recent progress in signal processing and generation of quantum states using four-wave mixing.


SWP invited presentations:

Kariem Arof
Solar module using dye-sensitized solar cells
M. H. Buraidah1, L. P. Teo1, Shahan Shah1, M. A. Careem1, I. Albinsson2, B.-E. Mellander3, and A. K. Arof1
1Centre for Ionics University of Malaya, Physics Department, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
2Department of Physics, University of Gothenburg, Sweden
3Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden

Solar module in this work will be fabricated comprising dye sensitized solar cells (DSSC). DSSC is made from transparent conducting oxide glass (TCO) coated with fluorine-doped tin oxide (FTO), two layers of titanium dioxide (TiO2) and ruthenium dye as photoanode, phthaloyl chitosan based gel polymer electrolyte containing iodide/triiodide redox mediator and platinum counter electrode. The two layers of TiO2 have different particle sizes. The first layer (14 nm particle size) acts as blocking layer whereas the second layer (particle size 21 nm) was a mesoporous layer. The current-voltage and impedance measurements were performed on the solar panel. Preliminary results shows that the solar module comprising five DSSC connected in series is capable to produce current around 1.13 mA/cm2, voltage of about 3.5 V and power of ~1.7 mW/cm2 under irradiation exposure of intensity 100 mW cm-2. The feasibility of the solar panel has been tested in practical applications e.g. operating small decorative items that require small power to function.

Jean-Michel Benoit
Effect on the coupling between patterned disordered emitters and surface plasmons
K. Chevrier, J.M. Benoit, C. Symonds, and J. Bellessa
Institut Lumière Matière, Université Claude Bernard Lyon 1, France

In this presentation, we will expose our recent research on light-matter coupling between plasmons and molecular emitters. Depending on the light-matter interaction strength, these hybrid systems can exhibit different behavior: weak or strong coupling. In the weak coupling regime, each parts of the system keeps its optical properties: no hybridization occurs between light and matter. In the strong coupling regime, plasmon/emitter interaction overtakes the damping in the system leading to an emerging new light-matter mixed state. This new state is then delocalized over numerous emitters on a wide distance, typically several microns, and leading to a coherent state, allowing the modification of the material properties. We investigate, in these researches, the consequences of the structuration in plasmon/organic emitters systems. Our system reveals unexpected properties conditioned by several parameters, such as the size pattern. We will then demonstrate that the length of interest is not related to the wavelength but seems to arise from the plasmon propagation length.

Muriel Botey
Cloaking on demand based on scattering cancelation
Z. Hayran1, R. Herrero2, M. Botey3, H. Kurt1, and K. Staliunas2,3
1Nanophotonics Research Laboratory, TOBB University of Economics and Technology, Department of Electrical and Electronics Engineering, Ankara, Turkey
2Departament de Física, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain
3Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain

We propose a feasible invisibility on demand approach. The scattering-cancelation cloaking scheme is based on the design of the scattering response of arbitrary shaped objects by a generalized Hilbert transform, relating he real and imaginary part of the object susceptibility. Following an iterative procedure, it allows to restrict the final object to non-magnetic, purely dielectric and lossy materials.

Caterina Ciminelli
Graphene/silicon Schottky junction solar cells
C. Ciminelli, F. Dell’Olio, G. Brunetti, D. Conteduca, and M. N. Armenise
Optoelectronics Laboratory, Politecnico di Bari, Italy

Several emerging application domains such as Internet of Things (IoT) and wearable electronic microsystems demand flexible solar cells that exhibit simultaneously low cost and high efficiency. Recent advances in the field of graphene-based solar cells have allowed the demonstration of cells with these features. In particular, graphene/silicon Schottky junction solar cells have demonstrated a very interesting performance in this context. The paper, after a review of the graphene-based solar cells, reports on some numerical results on a graphene-on-silicon flexible solar cell having an efficiency > 10 % and two important advantages, the environmental stability and the low complexity of the fabrication process. The design of this solar cell has been carried out through a general and accurate mathematical model, which has been validated by using experimental data reported in literature.

Gabriella Cincotti
Geometrical-optics based spectrophotometry
M. Marsan, M. Lucidi, and G. Cincotti
Engineering Department, University Roma Tre, Italy

Spectrophotometric analysis is routinely used in laboratory experiments to determine the concentration c of a constituent in a liquid, by measuring the optical depth τ = acl, also known as optical density (OD), knowing both the light path l and the extinction constant a. Optical density is related to the absorbance A and transmittance T, according to Beer-Lambert (BL) law T = Ft/Fi = e – τ = 10-A, where Ft and Fi are the transmitted and incident intensity light fluxes, respectively. The BL law assumes that the light is only absorbed, and therefore is valid only if the specimen under observation is a homogenous solution. In the case of microorganism analysis, microbial cells are dispersed in the solution and the BL law is a good approximation of turbidimetry measurements, only in the single-scattering regime. In fact, in general, spectrophotometric analysis does not furnish accurate results for high values of bacterial concentration, due to the multiple scattering effect. We present a geometrical-optics approach to increase the accuracy in OD measurements, using a LED-based photometer. In the case of a homogeneous solution, the corresponding liquid refractive index is evaluated from the measurements of the beam spot-size, using the Snell’s law. To increase the OD accuracy, we consider two different approaches where the ratio Ft/Fi is evaluated pixel-by-pixel, or averaged on the sensor area. In the microorganism growth analysis, instead, we consider two different sensor areas, where the incident Fi and transmitted Ft beams are evaluated. The proposed approach is tested with two different bacterial species: the gram-negative, rod-shaped Escherichia coli DH5α and the gram-positive, round-shaped, conglomerates-grape-like clusters-forming Staphylococcus aureus ATCC25923.

Massimo De Vittorio
Optical tools for controlling cell behavior
B. Spagnolo1, F. Pisanello1, and M. De Vittorio1,2
1Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Arnesano (Lecce), Italy
2Dipartimento di Ingegneria dell’Innovazione, Universita` del Salento, Istituto Nanoscienze- CNR, NNL-National Nanotechnology Laboratory, Lecce, Italy

Recent advances in both optic and genetic engineering fields have led to the realization and optimization of a new class of genetic light-induced tools. On one hand, light-switchable membrane ion channels have been widely used in neuroscience for light-controlled neural activation while, on the other hand, also other proteins can be modified in order to create complex light-inducible biological systems. In particular, 470 nm blue light irradiation is responsible for activation of the flavin chromophore, common to light-oxygen-voltage (LOV) proteins. Our approach, based on the use of blue light for activating a class of proteins related to cell movement, will combine optics and genetic for gaining control over cell mechanical properties involved in cell proliferation, migration and even metastases formation. This will lead to the opportunity of using laser beams to ‘activate’ cellular compartments by light with high spatio-temporal resolution, aiming to better understand and even modulate tumor cell behavior in 3D microenvironments.

Stavroula Foteinopoulou
Phonon-polariton-based route to enhanced directional thermal emission
S. Foteinopoulou1 and G. C. R. Devarapu2
1Electrical and Computer Engineering Department, University of New Mexico, Albuquerque, USA
2Cork Institute of Technology (CIT), Cork, Ireland

Strong phonon-photon coupling leads to a region of forbidden EM propagation in certain ionic bulk materials. This frequency regime, falling in the infrared spectrum is known as the Reststrahlen band. However, Mie scattering from sub-wavelength-sized objects made of such Reststrahlen-band materials can lead to highly localized and enhanced EM field modes. Actually, these infrared Mie phonon-polaritons mimic the properties of Mie plasmons of noble metal nanoparticles at the visible spectrum. We discuss here how Mie phonon-polaritons can be used as the basic building blocks to design platforms with a highly asymmetric absorber response, that is enhanced in one propagation direction and suppressed in the opposite propagation direction. We report that this highly asymmetric absorber response can exist over a broad spectral range within the Reststrahlen band and over a wide angular range, of more than 45 deg. from normal incidence. This behavior can lead to enhanced forward thermal emission that is highly relevant for one-way THz/infrared sources and passive radiative cooling devices.

Eleonora Frau
Modulated 3D cross-correlation dynamic light scattering of magnetic nanoparticle inks
E. Frau and S. Schintke
Laboratory of Applied NanoSciences (COMATEC-LANS), Department of Industrial Technologies, HEIG-VD, University of Applied Sciences Western Switzerland, Yverdon-les-Bains, Switzerland
Dynamic light scattering (DLS) is a versatile tool for sizing nanoparticles (NPs) suspended in fluids. In this paper, we apply and discuss modulated 3D cross-correlation DLS and UV-vis-NIR transmittance spectroscopy for the study of commercial iron oxide NP aqueous suspensions (Fe3O4 and Fe2O3, with nominal average size 10 nm and < 30 nm, respectively) motivated by the aim to use them for the formulation of magnetic NP inks. By analyzing the particle size distribution with the LS Instruments’ CONTIN algorithm, we find that the predominant particle sizes in nanoparticle products can strikingly differ from the values that a user would typically expect according to the provided suppliers’ information. We thus highlight that for application fields of magnetic NPs, such as e.g. ink formulations for nanoelectronics, spintronics or printed electronics, and whenever the particle size matters, the purchase and use of NP materials needs detailed product information and investigation of particle size distributions. Our analysis as a function of NP concentration confirm that modulated 3D cross-correlation DLS can efficiently be used even at high NP concentrations (e.g. 1.17 g/mL Fe2O3 load) without further dilution.

Konstantin Gaikovich
Methods and applications of near-field subsurface diagnostics
K. P. Gaikovich, Institute for Physics of Microstructures RAS, Nizhniy Novgorod, Russia
Methods of near-field diagnostics of subsurface inhomogeneities based on the solution of inverse scattering problems in various statements are presented. This diagnostics that provides a subwavelength resolution includes tomography and holography of 3D distributed inhomogeneities as well as the profiling (retrieval of depth profiles) of one-dimensional inhomogeneities. Developed solving algorithms of corresponding inverse problems involve in analysis scattered signals measured by small (with respect to wavelength) antennas in monostatic or bistatic configuration. The depth sensitivity of this diagnostics is achieved using the dependence of the probing field penetration on frequency, antenna altitude, and size of its aperture (multifrequency, pulse, multilevel and multi-aperture methods). In bistatic measurements, we propose also to use the dependence of the received signal formation on the transmitter-receiver distance (base). These methods can be applied both in electromagnetic and acoustic diagnostics – that demonstrate results of numerical simulations and experimental results that have been obtained for methods based on bistatic measurements with bow-tie antennas and on monostatic measurements with resonant cylinder probes.

Sonia García-Blanco
Al2O3 microresonator based passive and active biosensors
M. de Goede1, L. Chang1, M. Dijkstra1, R. Obregón2, J. Ramón-Azcón2, E. Martínez2, L. Padilla3, J. Adan3, F. Mitjans3, and S. M. García-Blanco1
1Optical Sciences Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
2Institute for Bioengineering of Catalonia, The Barcelona Institute of Science and Technology, Spain
3Health & Biomedicine Unit, LEITAT Technological Center, Barcelona, Spain

Al2O3 microresonators were realized for sensing applications of both passive and active devices. Passive microring resonators exhibited quality factors up to 3.2×105 in air. A bulk refractive index sensitivity of ~100 nm/RIU was demonstrated together with a limit of detection of ~10-6 RIU. Functionalizing their surface allowed for the label-free detection of the biomarker rhS100A4 from urine with a limit of detection of 3 nM. Furthermore, single-mode Al2O3:Yb3+ microdisk lasers were realized that could operate in an aqueous environment. Upon varying the bulk refractive index their lasing wavelength could be tuned with a sensitivity of ~20 nm/RIU and a LOD of  ~3×10-6 RIU.

Dominique Guichaoua
Functionalized methacrylic polymers for optical applications
D. Guichaoua1, K. Waszkowska1, V. Smokal2, O. Kharchenko2, B. Kulyk3, O. Krupka2, A. Migalska-Zalas4, and B. Sahraoui1
1Laboratory MOLTECH-Anjou, CNRS UMR 6200, University of Angers, France
2Department of Chemistry, Taras Shevchenko National University of Kyiv, Ukraine
3Department of Physics, Ivan Franko National University of Lviv, Ukraine
Faculty of Mathematics and Natural Sciences, Institute of Physics, J. Dlugosz Academy of Czestochowa, Poland
The photoactive organic materials containing admixed acceptor-donor (A-π bridge-D) compounds or polymers with A-π bridge-D moieties chemically incorporated into the main chain or in pendant groups attract a lot of attention due to their potential applications in photonic devices [1]. In particular, there have been intense efforts to identify contributions from different structural models of a molecule on the photochemical and optical properties. The methacrylic polymers can be functionalized by doping an NLO chromophore into a polymeric matrix (guest–host system) and covalently attached [2]. Either they are attached as pendant side group to the polymer backbone or incorporated into the main-chain backbone.  Photochromism is one of photochemistry phenomena which involve light induced reversible transformation of a molecule between two states. The interesting aspect concerning polymers with chromophore groups due to their possibility to transform between the generally stable trans form and the metastable cis form upon exposure of the light. The isomerization process of chromophore containing compounds plays significant role in the unique optical properties of materials. Therefore, we report the synthesis details, characterization, optical results obtained from the study of methacrylic polymer.  The new methacrylic monomers has been synthesized and then radically polymerized. The results of photochemical and optical activities of the corresponding polymer are presented herein. The third-order nonlinear optical response of spin deposited thin films has been investigated by means of Maker fringes technique using 30 ps laser pulses at a fundamental wavelength of 1064 nm.
[1] Z. Sekkat, W. Knoll: Photoreactive organic thin films, Academic Press, New York, 2002.
[2] H. El Ouazzani, K. Iliopoulos, M. Pranaitis, O. Krupka, V. Smokal, A. Kolendo, B. Sahraoui, Second- and third-order nonlinearities of novel push-pull azobenzene polymers, J. Phys. Chem. B, vol. 115, pp. 1944-1949, 2011.

Johannes Heitz
Three-dimensional photonic structures fabricated by two-photon polymerization for microfluidics and microneedles
C. Plamadeala1, S. R. Gosain1, S. Purkhart1, B. Buchegger1, W. Baumgartner2, and J. Heitz1
1Institute of Applied Physics, Johannes Kepler University Linz, Austria
2Institute of Biomedical Mechatronics, Johannes Kepler University Linz, Austria

Polymer micro- and nanostructures with various geometries like lines, gratings, woodpiles or dots can be written onto a transparent substrate by the technique of two-photon polymerization by a Ti-sapphire femtosecond-laser, which is focused into a liquid acrylate based resin containing a photo-initiator [1]. The microstructures can be also employed to mimic features found in nature for controlled wetting or liquid transport, as we demonstrated for drop-like structures from the integument of bark bugs which induce a directional transport of an oily liquid in closed capillary channels [2]. Similar structures can be implemented into channels of microfluidic devices to control the transport of fluids therein. In preliminary experiments, we were able to produce biomedical microneedles covered with microstructures which induce the transport of an aqueous liquid to the needle tip.
[1] B. Buchegger, et al., Stimulated emission depletion lithography with mercapto-functional polymers, ACS Nano, vol. 10, pp. 1954–1959, 2016.
[2] C. Plamadeala, et al., Bioinspired polymer microstructures for directional transport of oily liquids, Royal Society Open Science, vol. 4, pp. 160849, 2017.

Satoshi Ishii
Photocurrent generation with transition metal nitrides and transition metal carbides
S. Ishii1, S. L. Shinde1, and T. Nagao1,2
1International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Ibaraki, Japan
2Department of Condensed Matter Physics, Graduate School of Science, Hokkaido University, Sapporo, Japan

Photoexcited hot carriers in metals can be injected into adjacent semiconductors to collect sub-bandgap photons. In the current work, we experimentally demonstrate that transition metal nitrides and transition metal carbides can act as metals and generate hot electrons by optical illumination similar to metals. Since transition metal nitrides and carbides have broad absorption in the visible spectrum, they have the potential to be used for photocatalytic and photovoltaic applications to harvest solar energy.

Polina Kapitanova
All-dielectric metasurfaces as an efficient tool for electromagnetic waves manipulation
P. Kapitanova1, A. Sayanskiy1, M. Odit1, A. Miroshnichenko2, A. Lavrinenko3, and P. Belov1
1ITMO University, St. Petersburg, Russia
2School of Engineering and Information Technology, University of New South Wales Canberra, Australia
3DTU Fotonik, Technical University of Denmark, Lyngby, Denmark
We report on experimental study of a novel type of all-dielectric metalattice which support broadband dominant toroidal dipole response. The metalattice unit cell consists of four rectangular bars made of microwave ceramic with the permittivity of 10. By performing multipole decomposition we found that toroidal dipole response is dominant over a wide frequency range. We also show the correlation between the toroidal dipole response and longitudinal electric field component. By using this feature, as well as, direct near-field mapping we experimentally verify broadband toroidal dipole response of the metalattice. Since the unit cell exhibits C4 rotational symmetry this response is shown to be polarization independent.

Hamza Kurt
Light manipulations with metasurfaces in visible and infrared spectrum: Asymmetric transmission and tunability with phase change materials
H. Kurt1, A. Özer1, and H. Kocer2
1Department of Electrical and Electronics Engineering, TOBB University of Economics and Technology, Ankara, Turkey
2Medical Supply and Maintenance Center, Ankara, Turkey

Metasurfaces are two dimensional planar photonic structures recently proposed to alter amplitude, phase, and polarization of light. Plasmonic and all-dielectric metasurfaces are two different types of structures with comparable advantageous and drawbacks. Three-dimensional nano array of trapezoidal shaped aluminum on a sapphire substrate is designed to construct metasurface for altering the optical behavior of oppositely propagating light. We show that broadband and polarization independent asymmetric light propagation mechanism in metasurface configuration is feasible in the visible spectrum. The underlying physical concept is associated with the Wood-Rayleigh Anomaly such that different number of higher order modes appear upon oppositely incident light. Introducing vanadium dioxide as phase change material into the metasurface structure allows dynamic control over the transmitted light within the mid-infrared (IR) spectrum. Proposed structure can be fabricated with the current nano and micro fabrication techniques and can be utilized in smart front IR windows for protecting delicate sensors used for imaging and target detecting systems.

Maria Kafesaki
Parity-time (PT) symmetry in chiral metamaterials
M. Kafesaki, I. Katsantonis, S. Droulias, E. N. Economou, and C. M. Soukoulis
Foundation for Research and Technology Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), Heraklion, Crete, Greece

We discuss the possibility and conditions to achieve Parity-Time (PT) symmetry in chiral metamaterials, as well as the novel physical phenomena and possibilities appearing by combining the unique effects associated with PT-symmetry (e.g. unidirectional invisibility, coherent perfect absorption or lasing etc.) with the unique polarization control properties and potential achievable with chiral metamaterials.

Andrei Lavrinenko
Initial investigation for the fabrication of hyperbolic metamaterials based on ultra-thin Au layers
J. Sukham, O. Takayama, A. Lavrinenko, and R. Malureanu
DTU Fotonik, Technical University of Denmark, Lyngby, Denmark

In this paper, we will present the fabrication possibilities developed within our group for obtaining multilayer hyperbolic metamaterials (HMMs). The minimum metallic layer thickness reproducibly obtainable with our current technology is down to 6nm, while the dielectric layer can be as low as 4nm. During the talk we will present our approach for obtaining Au layers with better optical properties than the standard techniques. This is achievable by using an adhesion layer whose influence of the metallic properties is minimal compared to the classical Cr or Ti adhesion layers. These organic adhesion layers behave in a dielectric fashion and thus contribute more to the dielectric response rather than the metallic ones. Since the imaginary part of permittivity of these layers is negligible and the real part is very close to the silica one, their contribution to the behaviour of the HMMs is minimal. The optical properties of Au with organic adhesion layers showing a closer to theory response than Au with metallic adhesion layer as well as a possible explanation for this behaviour will be presented. This technique can be further used to obtain metal-dielectric multi-layers that lead to HMMs behaviour. Both fabrication possibilities and optical characterisation of HMMs will be shown and discussed during the talk.

Boris Lembrikov
Nonlinear optical phenomena in silicon-smectic A liquid crystal (SALC) waveguiding structures
B. I. Lembrikov, Y. Ben-Ezra, and D. Ianetz
Department of Electrical Engineering, Holon Institute of Technology, Holon, Israel

Liquid crystals (LCs) are organic materials characterized by a certain degree of ordering and anisotropy in their fluido-dynamic, elastic and electromagnetic properties. LCs possess strong optical nonlinearity. Due to these unique properties, LCs are promising candidates for the development of novel integrated devices for telecommunications and sensing. Nematic liquid crystals (NLCs) are mostly used and studied. However, smectic A liquid crystals (SALCs) have a higher degree of long range order, lower scattering losses in SALC, and they can be useful in nonlinear optical applications. We theoretically studied the nonlinear optical phenomena in a Silicon-SALC waveguide. We have shown that the strong stimulated light scattering (SLS) caused by SALC nonlinearity can occur in the Silicon-SALC waveguide.

Marco Liscidini
Light confinement in resonators based on Bloch surface waves
D. Aurelio, T. Perani, and M. Liscidini
Dipartimento di Fisica, University of Pavia, Italy

Bloch surface waves (BSWs) are electromagnetic modes that propagate at the interface between a truncated periodic multilayer and a dielectric external medium. These modes have been known since the late seventies, yet in the last decades they have attracted a renewed interest thanks to the development of fabrication techniques that allow one to obtain periodic multilayers with tens of periods quite inexpensively. Recently, it has been shown that ring resonators can be obtained starting by etching multilayers supporting Bloch Surface Waves. The design of this and other types of optical resonators based on BSW is particularly challenging due to the hybrid light confinement mechanism characterizing these structures. Yet, these systems are promising in all those situations that require light to be confined near the surface of a device, e.g. optical surface sensors and quantum dots. In this talk we will investigate the features characterizing BSW-based optical resonators in terms of light confinement and field enhancement.

Young Min
Recent advances in unusual optical coatings for flexible device applications
Young Min Song, Gil Ju Lee, and Young Jin Yoo
Gwangju Institute of Science and Technology (GIST), Korea

Optical coatings on the basis of thin-film interference have been widely used as key elements in various optical components and optoelectronic devices. For example, anti-reflection or high-reflection is observed under conditions of constructive or destructive interference achieved by multi-layer stacks of dielectric materials. On the other hand, unusual optical coatings in terms of their geometry and functions have recently been studied for new type of optical devices. In this presentation, we show three different types of optical coatings, i.e.: 1) ultra-thin films with highly absorbent media for coloration, 2) flexible and transparent electrodes based on epoxy-copper-ITO, and 3) tapered nanostructures for super-antireflection. Optical coatings on the basis of thin-film interference have been widely used as key elements in various optical components and optoelectronic devices. For example, anti-reflection or high-reflection is observed under conditions of constructive or destructive interference achieved by multi-layer stacks of dielectric materials. On the other hand, unusual optical coatings in terms of their geometry and functions have recently been studied for new type of optical devices. In this presentation, we show three different types of optical coatings, i.e.: 1) ultra-thin films with highly absorbent media for coloration, 2) flexible and transparent electrodes based on epoxy-copper-ITO, and 3) tapered nanostructures for super-antireflection.

Mauro Pereira
Harmonic generation in semiconductor superlattices with applications to the 100 GHz to the 1 THz range
M. F. Pereira, V. Anfertev, and V. Vaks
Institute of Physics, CAS, Prague, Czech Republic
This talk discusses a concept to study nonlinear optics through controllable nonlinearities in semiconductor superlattices. A predictive microscopic Nonequilibrium Green's Functions approach is used to deliver input to a relaxation-rate approximation approach leading to analytical expressions for the nonlinear polarization at arbitrary orders [1,2]  These results open the possibility of extending the whole field of nonlinear optics to the GHZ-THz range and the potential to  design materials and devices for a large number of applications, including spectroscopy of biomolecules, which typically have strong GHz-THz resonances.
[1] M.F. Pereira et al, Phys. Rev. B 96, 045306 (2017).
[2] M.F. Pereira et al, J. Nanophoton. 11 (4), 046022 (2017).

Silvia Pietralunga
Ultrafast scanning electron microscopy (USEM) to probe charge dynamics at surfaces of oxide thin films
S. M. Pietralunga1,2, V. Sala2,3, C. Manzoni1, G. Cerullo1,3, G. Lanzani2,3, G. Irde2,3, M. Zani3, and A. Tagliaferri2,3
1CNR-IFN, Milano, Italy
2CNST – Polimi, IIT 3, Milano, Italy
3Department of Physics, Politecnico di Milano, Italy
Photon-assisted ultrafast scanning electron microscopy (USEM) is a novel surface-sensitive experimental pump-probe technique featuring ps time resolution and nanoscale spatial resolution. USEM employs synchronized pulsed laser and electron beams, to excite optical transitions and to dynamically probe them in terms of the evolution in secondary electrons (SEs) contrast. Here we will introduced USEM specifically tailored to visualize color center dynamics in insulating oxide thin films. The principles of the technique will be discussed and results obtained on aluminum oxide-on-silicon thin film will be shown as an example.

Ferruccio Pisanello
Tapered fibers technology for multipoint control of neural activity in deep brain regions
F. Pisanello1, F. Pisano1, M. Pisanello1, G. Mandelbaum2, E. Maglie1,3, M. Hyun2, R. Peixoto2, A. Rizzo1,3, A. Balena1,3, E. Bellistri1, B. Sabatini2, and M. De Vittorio1,3
1Istituto Italiano di Tecnologia (IIT), Center for Biomolecular Nanotechnologies, Arnesano (Lecce), Italy
2Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, USA
3Dipartimento di Ingegneria dell’Innovazione, Universita` del Salento, Istituto Nanoscienze – CNR, NNL – National Nanotechnology Laboratory, Lecce, Italy

The possibility to optically interface with the mammalian brain is allowing for unprecedented investigations of functional connectivity of neural circuitry. A new generation of optical neural interfaces is being developed, mainly thanks to the exploitation of micro and nanotechnologies. After reviewing recent advances in this framework, the presentation will focus on a new technology to obtain multisite optical control of neural activity in deep brain regions. It is based on modal demultiplexing properties of tapered optical fibers to adapt light delivery depth to the size of functional structures and to obtain spatial-resolved optogenetic control of neural activity in sub- cortical regions such as the striatum or the thalamus. Depending on the geometry of the volume of interest, the light-confinement properties of the tapered optical fiber can be engineered to obtain both site-selective or wide-volume light delivery, allowing for unprecedented flexibility in in vivo experiments on rodents. The simplicity of this technique, together with its versatility, reduced invasiveness and compatibility with both laser and LED sources, indicate this approach can greatly complement the set of existing tools for light delivery in optogenetic experiments.

Alexander Quandt
Advanced light harnessing features in solar cell device simulations
A. Quandt1, T. Aslan1, I. Mokgosi1, and R. Warmbier2
1School of Physics, DST-NRF Centre of Excellence in Strong Materials and Materials for Energy Research Group, University of the Witwatersrand, Johannesburg, South Africa
2Department of Physics, University of Johannesburg, South Africa

Over the last decade a variety of ultrahigh-efficient solar cells has been presented in the literature [1]. Often the assembly of these novel photovoltaic devices requires substantial modifications in the basic layout of conventional organic and inorganic solar cells. The necessary new light harnessing features, like frequency conversion layers or plasmonic nanoparticles, must also be implemented in existing and future device simulation codes. We will describe the theoretical and numerical background to implement some of these advanced features in state-of-the-art device simulation codes, and we will particularly focus our discussion on frequency conversion layers
[1] A. Polman and H. A. Atwater, Photonic design principles for ultrahigh-efficiency photovoltaics, Nature Materials, vol. 11, pp. 174-177, 2012.

Ivan Richter
Novel effects and functionalities in subwavelength photonic and plasmonic (nano)structures
P. Kwiecien1, I. Richter1, V. Kuzmiak2, J. Čtyroký2, and J. Petráček3,4
1Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Physical Electronics, Czech Republic
2Institute of Photonics and Electronics of the CAS, Prague, Czech Republic
3Brno University of Technology, Faculty of Mechanical Engineering, Institute of Physical Engineering, Czech Republic
4Brno University of Technology, CEITEC - Central European Institute of Technology, Czech Republic

Currently, within our theoretical research under the Czech Science Foundation project, we investigate various novel effects and functionalities, connected with subwavelength (SW) photonic and plasmonic (nano)structures. Based on the development of numerical methods for the analysis of the interaction of the electromagnetic field with such structures, we have recently studied several interesting and potentially perspective problems: novel magnetooptic (MO) guiding structures with non-reciprocal properties, nonlocal response resonances in nanoplasmonic structures, gain-loss guiding structures, and plasmonic structures based on hybrid dielectric plasmonic slot waveguides (with nonlinear properties). In this contribution, we present and discuss several results selected from these problems, with the concentration given to the different special modelling techniques, we have recently developed. First, we have developed a specialized numerical technique - magnetooptic 2D and 3D MOaRCWA, in order to cope successfully with the complexity of wave effects in photonic nonreciprocal (one-way) structures, based on MO effects where unidirectional propagation can appear in the presence of an external magnetic field. We have focused on the investigation of the spectral and transmission properties of structures based on InSb/dielectric waveguides at THz frequencies. Second, we have developed the extension of the numerical RCWA technique capable of treating nonlocal hydrodynamic response which appears when the characteristic dimensions of plasmonic structures are scaled down, and thus the standard local-response approximation is no longer valid, depending on the structure complexity and relation between a characteristic dimension and the interacting wavelength. Third, we have developed the nonlinear coupled-mode theory (NL-CMT) method, as and efficient tool capable of treating the Kerr-nonlinear effects (and recently also other nonlinearities). Using this technique, we have investigated the effect of loss and gain on transmission characteristics of Kerr-nonlinear directional couplers. Selected examples will be presented and discussed.

Gilles Rosolen
Controlling the near-field of metasurfaces for free-electron multi-harmonic hard X-ray sources
G. Rosolen1,2, Liang Jie Wong3, N. Rivera2, B. Maes1, M. Soljacic2, I. Kaminer2,4
1University of Mons, Belgium
2Massachusetts Institute of Technology, USA
3Singapore Institute of Manufacturing Technology, Singapore
4Technion – Israel Institute of Technology, Haifa, Israel

Metasurfaces are subwavelength spatial variations in geometry and material, and offer us an ingenious way of manipulating far-field radiation. Here, we show that their ability to manipulate the near-field is also an extremely powerful lever in controlling nanophotonic photon-electron interactions. Indeed, the metasurface near-field contains high-order spatial harmonics that can be leveraged to generate substantial high harmonic components, whose properties are directly tunable through the metasurface geometry, the electron energy and the incidence angle of the input laser. By developing an analytical theory that produces results in excellent agreement with our ab initio simulations, we show how the design of metasurface-enhanced plasmons can be leveraged to produce bright and highly-directional multi-harmonic emission in the X-ray and the gamma ray range. As an example, we present the design of a four-color X-ray source, and we discuss how to scale up the output intensity using metamaterials.

Bouchta Sahraoui
Third harmonic generation of azo-based thin films
K. Waszkowska1, S. Slassi2, A. Amine2, A. El-Ghayoury1, and B. Sahraoui1
1LUNAM Universite, Universite d'Angers, CNRS UMR 6200, Laboratoire MOLTECH-Anjou, France
2LCBAE, Equipe Chimie Moléculaire et Molécules Bioactives, Université Moulay Ismail, Faculté des Sciences Meknès, Morocco

This paper presents investigation results of the linear and nonlinear optical properties for thin films containing azo-based compounds. Thin films were deposited on a glass substrate using spin coating technique. The linear optical properties were examined by using Absorption method. The nonlinear optical properties as well as Third Harmonic Generation were examined by means of Maker fringe technique by exploiting Nd:YAG laser at a wavelength 1064 nm. Third-order nonlinear optical susceptibility were calculated using theoretical model.

Silvia Schintke
Structuring of magnetic nanoparticle fluids for decorative and functional printing and coating
N. Fosso, E. Frau, and S. Schintke
Laboratory of Applied NanoSciences (COMATEC-LANS), Department of Industrial Technologies, HEIG-VD, University of Applied Sciences and Arts Western Switzerland, Yverdon-les-Bains, Switzerland

Aleksander Smirnov
Second-harmonic generation by Mie-resonant nanoparticles with bulk quadratic nonlinearity
D. A. Smirnova, I. I. Volkovskaya, and A. I. Smirnov
Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia

We study resonantly enhanced second-harmonic generation (SHG) by dielectric nanoparticles made of noncentrosymmetric materials with bulk quadratic nonlinearity. By combining analytical and numerical methods, we analyze the multipolar nature of the second-harmonic generated fields in AlGaAs and BaTiO3 nanoparticles optically excited in the vicinity of the low-order Mie resonances, with a particular focus on the magnetic dipole resonance. We derive selection rules for the multipolar composition of the nonlinear radiation depending on the symmetry of the crystalline structure and polarization of the incident light. The developed description can be instructive for design of highly-efficient nonlinear optical nanoantennas with reconfigurable radiation characteristics.

Kestutis Staliunas
Management of light patterns based on local Hilbert transform
K. Staliunas1,2, W. Ahmed2, M. Botey2, R. Herrero2, Z. Hayran3, and H. Kurt2
1Institució Catalana de Recerca i Estudis Avancats (ICREA), Barcelona, Spain
2Departament de Física, Universitat Politècnica de Catalunya (UPC), Terrassa, Spain

3Nanophotonics Research Laboratory, Department of Electrical and Electronics Engineering, TOBB University of Economics and Technology, Ankara, Turkey
We propose a new approach of optical field management based on a local Hilbert transform, which designs non-Hermitian potentials generating arbitrary vector fields of directionality, p(r), with desired shapes and topologies. We derive a local Hilbert transform to systematically build such potentials, by modifying background potentials (being either regular or random, extended or localized). In particular, we explore particular directionality fields, for instance in the form of a focus to create sinks for probe fields (which could help to increase absorption at the sink), or to generate vortices in the probe fields. Physically, the proposed directionality fields provide a flexible new mechanism for dynamically shaping and precise control over probe fields leading to novel effects in wave dynamics.

Tomasz Stefaniuk
2-level hierarchical metamaterials obtained using segregation process and nanostructurization
T. Stefaniuk1,2
1Faculty of Physics, University of Warsaw, Poland
2Glass Department, Institute of Electronic Materials Technology, Warsaw, Poland

Many novel physical phenomena and application concepts have been demonstrated so far in the fields of plasmonics and metamaterials. However, due to constraints of plasmonic metals further advancing towards real-life devices requires support from material technology. Here, we demonstrate that we can exploit segregation process in order to engineer the properties of constituent materials and thus enhance the optical response of the whole system. For example, up to 2 orders stronger frequency doubling can be achieved even at wavelengths where the interband transitions significantly reduce the nonlinear response of the metal. In the future bottom-up segregation process together with additional top-down nanostructuring might lead to new class of 2-level hierarchical metamaterials with the extended range of linear and nonlinear functionalities.

Rolandas Tomasiunas
Differential charge carrier lifetime investigated in a blue InGaN LED at operational conditions
R. Tomašiūnas1, I. Reklaitis1, L. Krencius1, P. Vitta1, S. Karpov2, H. J. Lugauer3, and M. Strassburg3
1Institute of Photonics and Nanotechnology, Vilnius University, Lithuania
2STR Group Soft-Impact Ltd., St. Petersburg, Russia
3OSRAM Opto Semiconductors GmbH, Regensburg, Germany

Investigation of non-equilibrium charge carrier dynamic properties in a light-emitting diode (LED) under working conditions is of essential importance, since none of the extrapolation methods either from the relative low or high charge carrier supply will give better insight into the processes of LED structure. Optimization of the LEDs requires a deeper insight into the charge carrier transport across the LED structure, electron-hole recombination mechanisms and competition of various recombination channels determining internal quantum efficiency (IQE) of the structures. The ABC-model considering three recombination mechanisms – the Shockley-Read-Hall recombination via defects (coefficient A), the bimolecular recombination (coefficient B) and the Auger recombination (coefficient C) – is a commonly used tool to interpret the processes related to IQE. Evaluation of these coefficients paves the way towards understanding of fundamental mechanisms limiting the LED efficiency and practical optimization of the LED structures. In this work different InGaN/GaN LEDs, emitting in blue, cyan and green spectral regions, were investigated under working conditions by small-signal photoluminescence frequency-domain lifetime measurement (FDLM) technique. Main advantage of this technique is that it combines LED operation under DC injection with resonant optical excitation slightly perturbing the non-equilibrium charge carrier density in the LED active region. Important is that the latter avoids uncertainty to attribute the extracted differential charge carrier lifetime to a specific non-equilibrium charge carrier concentration. FDLM technique confirmed its capability of extracting the ABC recombination coefficients, however, when carried out in a wide range of LED operating current a discrepancy between the DLT measured at lower current (less charge carrier density injected) and that predicted by the ABC-model has been revealed. To overcome the problem charge carrier escape from the quantum well as one of the important factors, which may let to define correctly the recombination coefficients of the ABC-model, was suggested. A more pronounced carrier escape observed for the relative shallower quantum wells of the blue LED may serve as a preliminary experimental proof. An extended study of charge-carrier localization and delocalization in the LEDs structures comprising a system of radiative and several non-radiative recombination channels has been performed by resonantly photo-excited small-signal photoluminescence FDLM.

František Uherek
Polymeric strip to double slot waveguide coupler
J. Chovan1 and František Uherek1,2
1International Laser Centre, Bratislava, Slovakia
2Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Bratislava, Slovakia

Slot waveguides are becoming more and more attractive optical components, especially for chemical and bio-chemical sensing. The problem of coupling light into the slot waveguides decreases performance of sensor systems with slot waveguide. We report on a design and simulation of polymeric strip to double slot waveguide coupler. The coupler was designed on commercial Ormocer polymer platform and operates at a 632.8nm wavelength. The minimal dimensions of coupler’s parts were designed for researcher direct laser writing fabrication by nonlinear two-photon polymerization. The simulation of the coupler was performed by Finite element and Beam propagation method tools. The overall calculated coupling losses of the designed coupler used in two interfaces strip to double slot and back to strip waveguide are 0.017 dB for TE mode and 0.127 dB for TM mode, respectively.

Mikhail Vasilevskiy
Tamm polaritons and cavity modes in the FIR range
J. Silva and M. Vasilevskiy
Centro de Física, Universidade do Minho, Braga, Portugal

Optical Tamm states (OTSs) are formed at the interface between two semi-infinite periodic dielectric structures (Bragg mirrors) or other reflectors. Contrary to usual surface polaritons, OTSs exist inside the "light cone" but their amplitude also decreases exponentially with the distance from the interface. We will discuss the formation of OTSs in the far-infrared (FIR) spectral range, in the reststrahlen band of a polar semiconductor, with the mirror made of a dielectric Bragg reflector or a periodic stack of graphene layers.

Caroline Vigreux
Towards optical sensors for the characterization of liquid sprays
C. Vigreux1, A. Taleb-Bendiab1,2, R. Escalier1, A. Pradel1, R. Kribich3, A. Ducanchez2, and R. Bendoula2
1ChV team, ICGM, UMR CNRS 5253, Université Montpellier, France
2ITAP group, IRSTEA, UMR 1201, Montpellier, France
3TéHO team, IES, UMR CNRS 5214, Université Montpellier, France

The goal of this project is to develop optical sensors for the characterization of the quantity and distribution of liquid sprays, in order to help farmers and in particular winegrowers to optimize the use of phytosanitary inputs. The basic building blocks of the optical sensors to be fabricated are waveguides, and the initial assumption is that droplet deposition on the surface of these waveguides alters their guiding properties. The first step of this work was to carry out simulations, in order to provide a good understanding of the impact of depositing one or more droplets on the waveguide surface. The influence of the size of the deposited drops (volume, covered guide surface), the position of the deposited drops (at the input, at the centre or at the exit of the waveguides) or the number of deposited drops on light absorption was thus studied thanks to simulations performed using a commercial beam propagation method from RSoft. The second step was to fabricate waveguides and to characterise them in terms of shape, refractive index, dimensions, optical confinement and propagation losses with or without drop deposition. To end, these measurement results were confronted to simulation so as to test the validity of the computed tendencies and to compare quantitative results in order to improve the model for further optimisation.

Laurent Vivien
Optical nonlinearities in strained silicon
L. Vivien, Institut d'Electronique Fondamentale, CNRS, Univ. Paris-Sud, Univ. Paris Saclay, Orsay, France

Changyuan Yu
Non-invasive respiration monitoring system based on smart sensor mat embedded with optical fiber interferometer
Changyuan Yu1, Shihang Bian2,3, Ying Shen2,3, Wei Xu4, and Cheungchuen Yu4
1Department of Electronic and Information Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
2School of Electronic & Information Engineering, Soochow University, Suzhou, China
3National University of Singapore (Suzhou) Research Institute, Suzhou China
4Anlight Optoelectronic Technology Inc., Suzhou, China

Respiration monitoring is a key tool in healthcare. Current monitors need invasive electronic sensors attached to user’s body, which is inconvenient and uncomfortable. We demonstrate photonic respiration system based on smart sensor mat embedded optical fiber interferometer. When a user simply lies/sleeps on the sensor mat, his/her breath will introduce slight strain changes on the mat and affect the light propagating within the fiber. Respiration waveforms can be achieved by analyzing the output light with signal processing. The system can collect the user’s signals continuously and remotely to provide big data for health analysis. Our technique is non-invasive, highly sensitive, and immune to electromagnetic interference.

Anna Zawadzka
Nonlinear optical properties of oxide thin films
A. Zawadzka1, P. Płóciennik1, K. Waszkowska1, D. Guichaoua2, and B. Sahraoui2
1Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Toruń, Poland
2University of Angers, MOLTECH-Anjou Laboratory, UMR CNRS 6200, Angers, France

This work contains description of the oxide thin films fabricated by Physical Vapor Deposition technique in high vacuum on transparent (quartz) and semiconductor (n-type silicon) substrates kept at room temperature during the deposition process. Titanium, tin and indium oxides were chosen as the material for investigation. Selected films were annealed after fabrication in ambient atmosphere for 12 hours at the temperature equal to 100°C, 150°C, 250°C and 450°C. Structural properties were examined by optical images and AFM measurements. The films exhibit high structural dependence on the temperature of the annealing process. Quality of the films can be improved by using an appropriate temperature during the annealing process. Nonlinear optical effects were studied using Third Harmonic Generation with Nd:YAG laser at 1064 nm wavelength as a fundamental beam. The values of third-order NLO susceptibilities were calculated and analyzed. We find that the nonlinear optical properties were strictly connected with the morphology. Moreover the temperature of annealing process can change the structural and optical properties of the tested oxide thin films.

WAOR invited presentations:

Theoni Alexoudi
Optical RAM and optical CAM architectures for disintegrated computing and high-speed routing applications
T. Alexoudi, C. Vagionas, P. Maniotis, and A. Miliou
Department of Informatics, Aristotle University of Thessaloniki, Greece

The unprecedented amounts of data and aggregated traffic currently being generated have pushed current computing and networking infrastructure to their limits, challenging their scaling in terms of bandwidth and energy. To sustain constant computational power advances, designers have now resorted to the massive employment of multi-core architectures in combination with deep and complex cache hierarchies, flooding the processor die with on-chip caches. Meanwhile, the increasing number of connected devices has stimulated a steady growth of routing tables, highlighting header processing in Address Lookup (AL) tables as a critical performance bottleneck in network operation, calling for specialized hardware-based memory solutions. Within this context, optical Random-access memories (RAMs) and optical Content-Addressable memories (CAMs) appear as promising solutions to serve for retaining data at high capacities and supporting computing and networking applications at the desired computational rate, while keeping an acceptable power envelope. In this article, we present our recent work on optical RAM and optical CAM architectures for disintegrated computing and routing applications, respectively.

Luiz Bonani
Classes of service defined by soft trunk reservation technique in elastic optical networks
L. H. Bonani, J. C. F. Queiroz, and M. A. Deffert
Universidade Federal do ABC – UFABC, Santo André – SP, Brazil

Elastic Optical Network (EON) is a very promising architecture where services of several bandwidth demands coexist. Without suitable management of spectrum, the natural behavior is that services with wider bandwidth requests suffer higher blocking rates than services with narrower ones. One of techniques to deal with this problem, reaching fairness, is the Trunk Reservation (TR). However, TR can severely degrade the overall network performance depending on the operation scenario. In this work we present a new variant of TR, called Soft Trunk Reservation (STR), to improve the network fairness level with smaller impact on the general network performance. We also show that STR technique can be used to create different classes of service considering the conventional EON operation.

Davide Careglio
ALLIANCE project: Architecting a knowledge-defined 5G enabled network infrastructure
D. Careglio, S. Spadaro, A. Cabellos, J. A. Lazaro, J. Perelló, P. Barlet, J. M. Gené, and J. Paillissé
Universitat Politècnica de Catalunya, Barcelona, Spain

Leaving the current 4th generation of mobile communications behind, 5G will represent a disruptive paradigm shift integrating access networks, ultra-high capacity access/metro/core optical networks and intra-datacentre network and computational resources into a single converged 5G network infrastructure. Thanks to an extensive deployment of network virtualization techniques leveraged by Software-Defined Networking (SDN) and Network Function Virtualization (NFV) technologies, such a 5G network infrastructure will have to be capable of inter-connecting anything anywhere and over a set of network services truly meeting their diverse communication requirements. In this paper, we overview the ALLIANCE project research activities. ALLIANCE ambitiously aims at architecting a converged 5G-enabled network infrastructure investigating several networking solutions such as SDN/NFV, OpenOverlayRouter (OOR) and the clean-slate Recursive Inter-Network Architecture (RINA) covering access, metro, core and datacentre segments. ALLIANCE relies on a Knowledge-Defined Networking (KDN) orchestrator which take advantage of state-of-the-art machine learning techniques to deploy, operate, monitor and troubleshoot networks automatically.

Qixiang Cheng
Advanced routing strategy with highly-efficient fabric-wide characterization for optical integrated switches
Qixiang Cheng, Yishen Huang, M. Bahadori, M. Glick, S. Rumley, and K. Bergman
Lightwave Research Laboratory, Columbia University, New York, USA

Optical switch fabrics are regarded as potential key components for future optical interconnects and access networks to meet the substantial and increasing demand for communications bandwidth. We begin with a review of the state-of-the-art optical switching technologies based on silicon integration platform with special attention to MZI-based switching devices, together with insights on their performance limitations and scalability considerations. We will then discuss the recent progress on the advanced routing strategy to largely improve the worst-case performance of the switch and relax the receiver dynamic range requirements. Furthermore, a highly-efficient fabric-wide method for calibration and characterization process for optical integrated switches without the need for built-in power monitors will be presented. This technique can substantially reduce the cost and complexity for device integration and packaging, which can be leveraged to facilitate the fast generation of routing strategy via the fully automated process.

Jaume Comellas
Periodic defragmentation in elastic optical networks
J. Comellas, L. Vicario, and G. Junyent
Optical Communications Research Group (GCO), Universitat Politècnica de Catalunya (UPC), Barcelona, Spain

The main weakness of Elastic Optical Networks (EON) stems from spectrum fragmentation. A thorough analysis about periodic defragmentation in EONs under dynamic traffic conditions is carried out. The effects of different defragmentation parameters on the EON performance are evaluated, and appropriate values, guaranteeing suitable network performance while keeping the network control complexity at a reasonable point, are obtained through simulations. Different network topologies as well as traffic conditions are simulated to assess the validity of the obtained results.

Ignacio de Miguel
Supervised machine learning techniques for quality of transmission assessment in optical networks
J. Mata1, I. de Miguel1, R. J. Durán1, J. C. Aguado1, N. Merayo1, L. Ruiz1, P. Fernández1, R. M. Lorenzo1, E. J. Abril1, and I. Tomkos2
1Universidad de Valladolid, Spain
2Athens Information Technology (AIT) Center, Greece

We propose and compare a number of machine learning models to classify unestablished lightpaths into high or low quality of transmission (QoT) categories in impairment-aware wavelength-routed optical networks. The performance of these models is evaluated in long haul communication networks and compared to previous proposals. Results show that, especially random forests and bagging trees approaches, significantly reduce the required computing time to classify the QoT of a given lightpath, while accuracy remains around 99.9%.

Jose Delgado Mendinueta
Wavelength and space division packet super-channel switching system for future data center optical networks with a switching capacity of 53.3 Tb/s/port
J. M. Delgado Mendinueta, S. Shinada, Y. Hirota, R. Soares Luís, H. Furukawa, and N. Wada
Photonic Network System Laboratory, National Institute of Information and Communications Technology (NICT), Tokyo, Japan

Data center (DC) traffic is expected to grow at a staggering annual rate over the next years. However, current DC networks, making use of point-to-point optical links and electronical switching systems, may be unable to meet this traffic demand with a reasonable energy consumption. Moreover, DC network traffic, characterized by dense matrices and bursty hot-spots, constitutes an additional challenge for DC networks designers. To address the capacity and energy bottlenecks and meet the traffic demands in future DC networks, this paper proposes a novel high-capacity optical switching system that employs time division multiplexing (TDM), wavelength division multiplexing (WDM), and space division multiplexing (SDM) to realize coherently modulated packet spatial super-channels (pSSCs). This optical switching system is based on three newly developed core-joint switching subsystems: an electro-absorption (EA)-based joint switch with ns switching speed, an acousto-optical modulator (AOM)-based joint switch with µs switching speed, and a free-space mirror-based joint switch with ms switching speed. These switching subsystems are used in a network testbed to experimentally demonstrate a 2x2 switching node with 64 wavelength channels, 7-core pSSCs modulated at 32 GBd. The results confirm a record switching capacity of 53.3 Tb/s/port and network protection in case of a multi-core fiber (MFC) failure in less than 10 ms.

Miquel Garrich
Overview of South-Bound interfaces for software-defined optical networks
M. Garrich1 and A. Bravalheri2
1Technical University of Cartagena, Spain
2High Performance Networks Group, Faculty of Engineering, University of Bristol, UK

In SDN-enabled networks, the control plane and data plane interaction relies on open South-Bound Interfaces (SBI) so that the SDN controller exercises direct control over the data plane elements. In electronic packet networks, OpenFlow is a consolidated SBI used to update packet handling rules in the flow table which governs the switches. In optical networks, the variety of Reconfigurable Optical Add/Drop Multiplexer (ROADM) technologies, vendors and architectures limit a straightforward adoption of a well-defined SBI. In this paper, we review current initiatives of SBI to control optical components which include ad-hoc extensions of OpenFlow and YANG modelling proposals combined with the NETCONF / RESTCONF protocol (e.g. OpenROADM and OpenConfig). Then we overview different tools and frameworks available for quick prototyping and deployment of software services that are compliant with such interfaces. Finally, we discuss the advantages and drawbacks of the reviewed initiatives considered key enablers for standardized end-to-end network programmability.

Ivan Glesk
Analysis of artificial intelligence-based metaheuristic algorithm for MPLS network optimization
M. Masood1, M. M. Fouad2, and I. Glesk1
1Electronics and Electrical Engineering Department, University of Strathclyde, Glasgow, UK
2Arab Academy for Science, Technology, and Maritime, Transport, Cairo, Egypt

Multiprotocol label switched (MPLS) networks were introduced to enhance the networks’ service provisioning and optimize performance. There are number of artificial intelligence-based optimization algorithms that can be used for the optimization of traffic engineering of MPLS networks. This paper proposes a dolphin algorithm, which is a metaheuristic global minima-based technique for the optimization problem in MPLS networks. Then we compare it with a Bat algorithm.

Xavier Hesselbach
Network function virtualization aware offline embedding problem using squatting-kicking strategy for elastic optical networks
A. El-mekkawi, X. Hesselbach, and J.-R. Piney
Dept. Network Engineering, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain

Network Function Virtualization (NFV) has recently become one of the most attractive technologies in telecommunication industry due to its ability to realize Network Services (NSs) on general-purpose hardware hence replacing traditional middleboxes. Therefore, NSs can be put on the market, maintained and upgraded more easily and timely which creates a great potential for increasing the usage value of network resources. This paper exploits this paradigm addressing the NFV architecture provisioning the huge computational capacity required in the NS to support the resource allocation strategy proposed for elastic optical networks (EONs) based on resources utilization optimization using a proposed and analyzed squatting-Kicking model (SKM) strategy.

Brigitte Jaumard
Optimal design of filterless optical networks
B. Jaumard, Yan Wang, and N. Huin
CSE, Concordia University, Montréal, Canada

In this paper, we study the design of filterless optical networks in order that the maximum link network capacity is minimized. We proposed a one-step approach to simultaneously generate tree filterless subnetworks, the provisioning of the requests, and the splitter/combiner requirements. We propose a solution process that allows the exact solution of the proposed one step optimization model, together with a heuristic. Numerical experiments show that the proposed optimization model and algorithm outputs much better solutions than in the previous studies, within reasonable computing times.

David Larrabeiti
Elastic networks thematic network results II: Edge computing and wireless support
X. Masip1, E. Marín1, A. Jurnet1, P. Reviriego2, R. Flores3, C. M. Lentisco3, D. Fernández3, L. Bellido3, S. Gómez4, E. Calle4, G. Otero5, J. A. Hernández5, and D. Larrabeiti5
1Universidad Politécnica de Cataluña, Spain
2Universidad Antonio de Nebrija, Spain
3Universidad Politécnica de Madrid, Spain
4Universitat de Girona, Spain
5Universidad Carlos III de Madrid, Spain

This paper overviews the approach of the Elastic Networks research network to address the challenges posed by the convergence of networking and computing in the edge for a number of scenarios. Firstly, we address reliability in Fog-to-Cloud computing.  Then an architecture for a residential SDN gateway featuring NFV is presented. In addition switching based on SDN in data center is studied for which a high-speed flexible packet matching in hardware is proposed. Finally, a technique for delay analysis in a single node C-RAN scenario is described.

Guido Maier
Enabling multipath optical routing with hybrid differential delay compensation
R. Alvizu1, V. Soto2, S. Troia1, and G. Maier1
1Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Italy
2Facultad de Ingeniería en Electrónica y Computación, Escuela Superior Politécnica del Litoral, Guayaquil, Ecuador

Historically, Internet traffic has been routed over the shortest path: which was convenient for best-effort data traffic; but it is not always suitable for today’s scenario where applications can require bandwidth higher than what is available in a single link, even when provided by an optical wavelength-channel. Multi-path (MP) routing is a network functionality that provides more capacity, reduces the probability of link congestion and increases the availability of the transport service. This paper elaborates on techniques to mitigate the differential delay in all optical networks, recognized as the main problem of multi-path (MP) routing. This work shows how hybrid differential delay compensation (HDDC) can greatly reduce the use of expensive reconstruction buffers in all optical networks implementing MP optical routing. A novel mixed integer linear programming formulation is proposed for the novel wavelength + H-DDC assignment problem: distributed fiber delay lines (FDL)s combined with electronic reconstruction buffers collocated at optical regeneration points. Numerical results based on commercially available (and rack mountable) FDLs demonstrated the effectiveness of H-DDC in medium size transport networks.

Marc Ruiz
Metro-flow traffic modelling for cognitive adaptation of core virtual network topologies
F. Morales, M. Ruiz, and L. Velasco
Universitat Politècnica de Catalunya (UPC), Barcelona, Spain

A successful use case of cognitive networking consists in the reconfiguration of core virtual network topologies (VNTs) based on traffic predictive models obtained by applying data analytics to monitored traffic data. This use case entails long times (several days) to collect enough traffic monitoring samples data at core nodes to allow traffic modelling algorithms (usually at the core controller) to produce accurate models. Notwithstanding, that requirement could not be achieved in the case that metro controllers re-route metro-flows for metro-scope re-optimization purposes. In that case, some metro-flows suddenly change its node entering the core VNT, which drastically impacts on core traffic behaviour. In this paper, we present core-flow traffic models based on the aggregation of metro-flow traffic models. We consider that metro controllers generate traffic models based on monitoring the traffic of the metro-flows and those models are available in a shared repository for the core controller to access them. Moreover, the announcement of metro-flows re-routing from metro controllers to the core controller is assumed to allow fast core-flows models adaptation. Such aggregated models are then used to generate inputs for cognitive core VNT re-optimization purposes.

Josep Solé-Pareta
Elastic networks thematic network results I: Planning and control of flex-grid/SDM
F.J. Moreno-Muro1, R. Rumipamba-Zambrano2, J. Perelló2, P. Pavón-Mariño3, J. Solé-Pareta2, R. Martínez3, R. Casellas3, R. Vilalta3, R. Muñoz3, J. Mata4, L. Ruiz4, N. Merayo4, I. de Miguel4, and R.J. Durán4
1Universidad Politécnica de Cartagena, Spain
2Universitat Politécnica de Catalunya, Spain
3Centre Tecnològic de Telecomunicacions de Catalunya, Spain
4Universidad de Valladolid, Spain
This paper overviews the approach of the Elastic Networks research network for planning and control of flex-grid/SDM optical networks. Firstly, we present the Net2Plan open-source planning tool  capabilities to model Flex-Grid/SDM networks; secondly a PCE-based Transport-SDN controller for packet over flex-grid optical networks is described. Finally results on machine-learning-based QoT classification techniques useful in planning and control are reported.

Kyriakos Vlachos
Performance evaluation of a reconfigurable optical add drop multiplexer design for high-order regular and offset-QAM signals
K. Vlachos, F. Ferreira, and S. Sygletos
Department of Computer Engineering and Informatics, University of Patras, Greece
The conventional Orthogonal Frequency Division Multiplexing (OFDM) and Nyquist pulse shaping signals have the advantage of high spectral efficiency when consisting of super-channels in the Wavelength-Division-Multiplexing (WDM) domain. However, current design of Reconfigurable OADM cannot support the spectrally overlapping sub-channels (in the case of OFDM) or provide high finesse filtering functions for super-Nyquist-WDM channel encoding. Further offset-Quadrature Amplitude Modulation has been proposed to eliminate ISI crosstalk of OFDM sub-channels, using commercial transmitters with typical signal spectral profiles and conventional pulse rise-times. In this work, we present performance evaluation results of a ROADM architecture that can accommodate offset QAM signals and further, we optimized its sub-channel switching performance for critical devices and sub-system parameters.