Overview of high-speed TDM-PON beyond 50 Gbps per wavelength using digital signal processing [Invited Tutorial]

The recent evolution of passive optical network standards and related research activities for physical layer solutions that achieve bit rates well above 10 Gbps per wavelength (lambda) is discussed. We show that the advancement toward 50, 100, and 200 Gbps/lambda will certainly require a strong introduction of advanced digital signal processing (DSP) technologies for linear, and maybe nonlinear, equalization and for forward error correction. We start by reviewing in detail the current standardization activities in the International Telecommunication Union and the Institute of Electrical and Electronics Engineers, and then we present a comparison of the DSP approaches for traditional direct detection solutions and for future coherent detection approaches. (c) 2022 Optica Publishing Grou

Towards Higher Speed Next Generation Passive Optical Networks

L'abstract è presente nell'allegato / the abstract is in the attachmen

Telecommunication Systems

This book is based on both industrial and academic research efforts in which a number of recent advancements and rare insights into telecommunication systems are well presented. The volume is organized into four parts: "Telecommunication Protocol, Optimization, and Security Frameworks", "Next-Generation Optical Access Technologies", "Convergence of Wireless-Optical Networks" and "Advanced Relay and Antenna Systems for Smart Networks." Chapters within these parts are self-contained and cross-referenced to facilitate further study

Analysis and optimisation of semiconductor reflective modulators for optical networks

Reflective modulators based on the combination of an electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA) are attractive devices for applications in long reach carrier distributed passive optical networks (PONs) due to the gain provided by the SOA and the high speed and low chirp modulation of the EAM. Integrated R-EAM-SOAs have experimentally shown two unexpected and unintuitive characteristics which are not observed in a single pass transmission SOA: the clamping of the output power of the device around a maximum value and low patterning distortion despite the SOA being in a regime of gain saturation. In this thesis a detailed analysis is carried out using both experimental measurements and modelling in order to understand these phenomena. For the first time it is shown that both the internal loss between SOA and R-EAM and the SOA gain play an integral role in the behaviour of gain saturated R-EAM-SOAs. Internal loss and SOA gain are also optimised for use in a carrier distributed PONs in order to access both the positive effect of output power clamping, and hence upstream dynamic range reduction, combined with low patterning operation of the SOA Reflective concepts are also gaining interest for metro transport networks and short reach, high bit rate, inter-datacentre links. Moving the optical carrier generation away from the transmitter also has potential advantages for these applications as it avoids the need for cooled photonics being placed directly on hot router line-cards. A detailed analysis is carried out in this thesis on a novel colourless reflective duobinary modulator, which would enable wavelength flexibility in a power-efficient reflective metro node

Redes ópticas de acesso de nova geração : tecnologias e economia

Doutoramento em Engenharia Eletrotécnica - TelecomunicaçõesThe work presented herein, studies Next Generation Optical Access Networks (NG-OAN) economically (e.g. energy consumption) and technologically (e.g. rate, reach and dedicated/shared bandwidth). The work is divided into four main topics: energy efficiency in optical access architectures, novel spectrally efficient Long-Reach Passive Optical Networks (LR-PON), crosstalk impacts in heterogeneous and homogenous access networks and hybrid optical wireless transmissions. We investigate the impact of user profiles, optical distribution network topologies and equipment characteristics on resource sharing and power consumption in LR-PON. To have a clear vision on the energy consumption evolution of each part of NG-OAN, a model is proposed to evaluate the energy efficiency of optical access technologies. A spectrally efficient bidirectional Ultra-Dense Wavelength Division Multiplexing (UDWDM) PON architecture is developed using Nyquist shaped 16-ary quadrature amplitude modulation, offering up to 10 Gb/s service capabilities per user or wavelength. Performance of this system in terms of receiver sensitivity and nonlinear tolerance under different network transmission capacity conditions are experimentally optimized. In bi-directional transmis-sion, using frequency up/down-shifting of Nyquist pulse shaped signal from optical carrier, a full bandwidth allocation and easy maintenance of UDWDM networks as well as reduction of Rayleigh back-scattering are achieved. Moreover, self-homodyne detection is used to relax the laser linewidth requirement and digital signal processing complexity at the optical network unit. Simplified numerical model to estimate the impact of Raman crosstalk of multi-system next generation PONs in video overlay is proposed. Coexistence of considered G.98X ITU-T series and coherent multi-wavelength systems is considered and assessed. Additionally, the performances of bidirectional hybrid optical wireless coherent PONs over different optical distribution network power budgets and hybrid splitting ratios are evaluated.O trabalho aqui apresentado estuda redes óticas de acesso de próxima geração (NG-OAN) nas vertentes económica (consumo de energia) e tecnológica (taxa, alcance e largura de banda dedicada/partilhada). O trabalho está dividido em quatro grandes temas de investigação: a eficiência energética em arquiteturas de acesso ótico, as redes óticas passivas de longo alcance (LR-PON) com nova eficiência espetral, o impacto da diafonia em redes de acesso heterogéneas e homogéneas e as transmissões ópticas híbridas com tecnologias sem fio. Investiga-se o impacto dos perfis dos utilizadores, as tipologias da rede de distribuição ótica, as características do equipamento de partilha de recursos e o consumo de energia em LR-PON. Para se ter uma visão clara sobre o consumo de energia de cada parte das NG-OAN, é proposto um modelo para avaliar a eficiência energética das tecnologias de acesso óticas. Desenvolve-se uma arquitetura PON bi-direcional com elevada eficiência espetral, recorrendo a multiplexagem por divisão de comprimento de onda ultra-densa (UDWDM), modulação de amplitude em quadratura com formato de impulso de Nyquist, oferecendo até 10 Gb/s por utilizador/comprimento de onda. O desempenho deste sistema em termos de sensibilidade do recetor e da tolerância à resposta não linear do canal de comunicação, sob diferentes condições de transmissão, é avaliado experimentalm-ente. Em transmissão bi-direcional, utilizando desvio de frequência (cima/baixo) do impulso com formato de Nyquist relativo à portadora ótica conseguiu-se uma alocação de largura de banda completa e uma manutenção mais simplificada de redes UDWDM, bem como a redução do espalhamento de Rayleigh. Além disso, a deteção auto-homodina é usada para relaxar o requisito de largura de linha do laser e a complexidade do processamento digital de sinal nas unidades da rede ótica. Propõe-se um modelo numérico simplificado para estimar o impacto da diafonia de Raman em sistemas PON de próxima geração, com sobreposição do sinal de vídeo. É analisada a coexistência da série G.98X ITU-T e são considerados e avaliados sistemas coerentes multi-comprimento de onda. Adicionalmente avaliam-se os desempenhos de PONs bi-direcionais híbridas, considerando tecnologia coerente e propagação por espaço livre, para diferentes balanços de potência e taxas de repartição na rede ótica de distribuição

High-speed low-power modulator driver arrays for medium-reach optical networks

The internet is becoming the ubiquitous tool that is changing the lives of so many citizens across the world. Commerce, government, industry, healthcare and social interactions are all increasingly using internet applications to improve and facilitate communications. This is especially true for videoenabled applications, which currently demand much higher data rates and quality from data networks. High definition TV streaming services are emerging and these again will significantly push the demand for widely deployed, high-bandwidth services. The current access passive optical networks (PONs) use a single wavelength for downstream transmission and a separate one for upstream transmission. Incorporating wavelength-division multiplexing (WDM) in a PON allows for much higher bandwidths in both directions. While WDM technologies have been successfully deployed for many years in metro and core networks, in access networks they are not commonly used yet. This is mainly due to the high costs associated with deploying entire WDM access networks. However, the present optical networks cannot be simply and cost-effectively scaled to provide the capacity for tomorrow’s users. As an effect there is a strong need for new WDM access components which are compact, cost-competitive and mass-manufacturable. Increasing the number of wavelengths for WDM-PON automatically leads to an increase in the number of single pluggable transceivers, which brings substantial design challenges and additional costs. The multitude of TXs and RXs for different wavelength channels increases the total footprint considerably. Photonic integration of transceivers into arrays will significantly reduce the footprint and cost. However, the total power consumption of an array device is an issue. To avoid the use of a thermoelectric cooler, the integration density of components is severely limited by the heat dissipating capabilities offered by their package. As a result the WDM-PON philosophy necessitates the reduction of the transceiver’s power dissipation. From this plea it is apparent that the main technology challenges for realizing future-proof optical (access) networks are reducing active component power consumption, shrinking form factors and lowering assembly costs. In this perspective an over 100 Gb/s throughput component, composed of 10 channels at 11.3 Gb/s per wavelength channel would be a great contribution to the expansion of customer bandwidth. It can provide increased line rates to the end users at speeds of 10 Gb/s per wavelength. As RXs typically consume much less power than externally modulated TXs, they can relatively easily be integrated into an array. Mainly high speed optical transmitters have significant power consumptions and the heat generation caused by power dissipation forms a critical obstacle in the development of a 10-channel transmitter, which again underlines the importance of power reduction. Alongside the introduction of WDM in access networks, also inter-office point-to-point connections in data center environments could benefit from the WDM philosophy. As data center operators often suffer from fiber scarcity or do not own their fiber infrastructure, WDM technologies are essential to deliver reach and capacity extension for these scenarios. Interdata center communication also benefits from cost-, footprint- and energyefficient components operating at high speed to maximize the throughput. As an effect integrated over 100 Gb/s transceivers, such as 4 channels at 28 Gb/s, are highly desirable. The research described in this dissertation was partly funded by the European FP7 ICT project C3PO (Colourless and Coolerless Components for low Power Optical Networks) and the UGent special research fund. The C3PO project aimed to develop a new generation of green Si-photonic compatible components with record low power consumption, that can enable bandwidth growth and constrain the total cost. C3PO envisioned building high-capacity access networks employing reflective photonic components. To achieve this, cost-competitive reflective transmitters based on electroabsorption modulators (EAM) needed to be closely integrated into arrays. A multi-wavelength optical source provides the required wavelength channels for both downstream and upstream signals in the WDM-PON. Chapter 1 gives a short overview of a PON and describes the main implementations of a WDM-PON access network. It introduces integrated low power transmitter arrays for a cost-effective architecture of WDM-PONs and inter-data center communication. Chapter 2 compares different optical transmitters and gives a short overview of their most important characteristics. External modulation through both Mach-Zehnder modulators (MZMs) and EAMs is described. It shows that EAMs are the best choice for low power transmitter array integration, thanks to their lower drive voltage and smaller form factor, compared to MZMs. To achieve a reduced consumption, the electronic modulator driver topology is studied in chapter 3. The challenge in designing modulator drivers is the need to deliver very large currents in combination with high voltage swings. Four distinct output configurations are compared and techniques to reduce the power consumption of the drivers are described. Chapter 5 presents duobinary (DB), a modulation scheme that is gaining interest in today’s optical transmission. As the required bandwidth is about half that of NRZ, it softens the constraints on the transmitter bandwidth. Thanks to its narrow optical spectrum, it has an improved tolerance to dispersion in long haul single mode links and it can improve the spectral efficiency in WDM architectures. For optical DB a precoder is necessary to assure the received signal is equal to the original binary signal. The conducted research that resulted in this dissertation produced 2 low power EAM driver arrays: A 10-channel 113 Gb/s modulator driver array with state-of-the art ultra-low power consumption. A 2-channel 56 Gb/s duobinary driver array with a differential output with low power consumption. Both designs are elaborately analyzed in chapter 4 and 6 respectively. To the best of our knowledge the 10-channel EAM driver array is the first in its kind, while achieving the lowest power consumption for an EAM driver so far reported, 50% below the state of the art in power consumption. The 2-channel EAM driver array is the fastest modulator driver including on-chip duobinary encoding and precoding reported so far. The final chapter provides an overview of the foremost conclusions from the presented research. It is concluded with suggestions for further research