Optical fibre has become the dominant theme of transmission in long haul, high data rate communication systems due to its tremendous bandwidth and low loss. Radio over Fibre (RoF) technology facilitates the seamless integration between wireless and optical communication systems and found to be the most promising solution to meet the exponential bandwidth demands expected for the upcoming years. However, the main bit-rate/distance limitation in RoF systems is the chromatic dispersion. In this thesis, the two generations of RoF technologies, namely Analogue RoF (ARoF) and Digital RoF (DRoF) are investigated. The overall aim of this research is to optimise the optical bandwidth utilisation of these two approaches for a typical transmission of the fronthaul link proposed in the next generation Centralised Radio Access Network (C-RAN). Consequently, a number of physical layer design scenarios for the optimised transmission of the Radio Frequency (RF) signals over a Standards Single Mode Fibre (SSMF) are demonstrated. Firstly, for an ARoF transmission, where the analogue RF signals are transported over SSMF using an optical carrier, a bidirectional link transmitting four Downlink/Uplink channels in a chromatic dispersion limited scenario is designed. Simulation results have shown a clear constellation diagram of a 2.5 Gb/s RF signal transmission over 120 km fibre length. Secondly, a DRoF system with reduced optical bandwidth occupancy is proposed. This system employs an optical Duobinary transmission to the digitised RF signal at the transmitter side to reduce its spectrum and to address the chromatic dispersion effect, simultaneously. Simulation results demonstrate the capability of the proposed system to maintain high-quality transmission of the digitised signals over 70 km of fibre distance without dispersion compensation requirements. Finally, an advanced DRoF transmission link based on integrating digital Optical Single Sideband (OSSB) transmission with Duobinary encoding scheme is designed. Simulation results have clearly verified system's robustness against transmission impairments and have better performances in terms of the obtained BER and EVM with respect to the 3GPP standardised values. Moreover, the results show that both transmission distance and power budget are furtherly improved in comparison with two other digital transmission scenarios.

This thesis studies and mathematically models nonlinear interactions among channels of modern high bit rate (amplitude/) phase modulated optical systems. First, phase modulated analogue systems are studied and a differential receiving method is suggested with experimental validation. The main focus of the rest of the thesis is on digital advanced modulation format systems. Cross-talk due to fiber Kerr nonlinearity in two-format hybrid systems as well as 16-QAM systems is mathematically modelled and verified by simulation for different system parameters. A comparative study of differential receivers and coherent receivers is also given for hybrid systems. The model is based on mathematically proven assumptions and provides an intuitive analytical understanding of nonlinear cross-talk in such systems. / Graduate

Esta dissertação de mestrado investiga os formatos de modulação óptica alternativos ao tradicional formato binário de intensidade (NRZ - Non-return-to-zero), ditos avançados, como tecnologia chave para atender às exigências do mercado atual de telecomunicações por transporte de grande volume de dados e alta largura de banda, associados com a redução do custo da informação transmitida por bit. Os formatos avançados de modulação óptica fazem parte das tecnologias que estão sendo investigadas intensamente com o objetivo de superar os desafios impostos pela nova geração de sistemas ópticos com taxas a partir de 40 Gb/s. Este trabalho focaliza o estudo dessa tecnologia, apresentando uma visão geral dos formatos mais discutidos atualmente, suas características e tecnologias de implementação. Foram realizadas simulações utilizando o software comercial Optisystem versão 7.0 da empresa canadense Optiwave Systems Inc., para analisar o desempenho de alguns formatos de modulação de intensidade e de fase com respeito à sensibilidade do receptor, resistência ao cascateamento de filtragem óptica e a efeitos dispersivos e não-lineares. Procurou-se avaliar os formatos em enlaces reais, com características necessárias à sua possível utilização. Também é feita uma breve consideração dos custos associados aos formatos de modulação analisados neste trabalho. Dentre os formatos analisados, os RZ (Return-to zero) apresentaram maior sensibilidade do receptor e melhor tolerância aos efeitos não-lineares que os seus equivalentes NRZ, porém baixa tolerância aos efeitos dispersivos e ao cascateamento de filtragem óptica. O formato duobinário mostrou fraco desempenho de sensibilidade, mas provou ser o mais tolerante à dispersão cromática e à concatenação de filtragem óptica. Os formatos de modulação de fase mostraram ser bem resistentes aos efeitos não-lineares e aos efeitos dispersivos. / This MSc thesis investigates optical modulation formats as an alternative to the use of the traditional intensity binary format NRZ (Non-return-to-zero). Those formats, classified as advanced, represent one of the key technologies aimed to enable the high data volume and broadband, demanded by the present telecommunication market, with cost reduction of transmitted information per bit. Those technologies have been intensevely studied with purpose of overcoming the challenges imposed by the new generation of optical systems, with bit rates from 40 Gb/s. This work focuses on the study of modulation formats most discussed currently, presenting an overview of their main characteristics and implementation techniques. The performance of some intensity and phase formats, in terms of receiver sensitivity, optical filtering cascading, dispersion and nonlinear effects robustness, have been theoretically analyzed from simulations carried out with the commercial software Optisystem v. 7.0, of the Canadian company Optiwave Systems Inc. The analysis has been applied to real optical links, with characteristics that, potentially, demand their use. A cost analysis, based on estimated values associated to devices required for implementing the formats investigated in this work, is also presented. Among the formats studied, those based on RZ (Return-to zero) presented the highest receiver sensitivity and best tolerance to nonlinear effects, in comparison to their equivalent formats, based on NRZ. However, they are less tolerant to dispersive effects and optical filtering cascading. The duobinary format (DB) has shown a weak performance in terms of sensitivity, though has been proved to be the most tolerant to chromatic dispersion and filtering cascading effects. Among all formats, the phase modulation ones presented the highest resistance against nonlinear and dispersive effects.

Esta dissertação de mestrado investiga os formatos de modulação óptica alternativos ao tradicional formato binário de intensidade (NRZ - Non-return-to-zero), ditos avançados, como tecnologia chave para atender às exigências do mercado atual de telecomunicações por transporte de grande volume de dados e alta largura de banda, associados com a redução do custo da informação transmitida por bit. Os formatos avançados de modulação óptica fazem parte das tecnologias que estão sendo investigadas intensamente com o objetivo de superar os desafios impostos pela nova geração de sistemas ópticos com taxas a partir de 40 Gb/s. Este trabalho focaliza o estudo dessa tecnologia, apresentando uma visão geral dos formatos mais discutidos atualmente, suas características e tecnologias de implementação. Foram realizadas simulações utilizando o software comercial Optisystem versão 7.0 da empresa canadense Optiwave Systems Inc., para analisar o desempenho de alguns formatos de modulação de intensidade e de fase com respeito à sensibilidade do receptor, resistência ao cascateamento de filtragem óptica e a efeitos dispersivos e não-lineares. Procurou-se avaliar os formatos em enlaces reais, com características necessárias à sua possível utilização. Também é feita uma breve consideração dos custos associados aos formatos de modulação analisados neste trabalho. Dentre os formatos analisados, os RZ (Return-to zero) apresentaram maior sensibilidade do receptor e melhor tolerância aos efeitos não-lineares que os seus equivalentes NRZ, porém baixa tolerância aos efeitos dispersivos e ao cascateamento de filtragem óptica. O formato duobinário mostrou fraco desempenho de sensibilidade, mas provou ser o mais tolerante à dispersão cromática e à concatenação de filtragem óptica. Os formatos de modulação de fase mostraram ser bem resistentes aos efeitos não-lineares e aos efeitos dispersivos. / This MSc thesis investigates optical modulation formats as an alternative to the use of the traditional intensity binary format NRZ (Non-return-to-zero). Those formats, classified as advanced, represent one of the key technologies aimed to enable the high data volume and broadband, demanded by the present telecommunication market, with cost reduction of transmitted information per bit. Those technologies have been intensevely studied with purpose of overcoming the challenges imposed by the new generation of optical systems, with bit rates from 40 Gb/s. This work focuses on the study of modulation formats most discussed currently, presenting an overview of their main characteristics and implementation techniques. The performance of some intensity and phase formats, in terms of receiver sensitivity, optical filtering cascading, dispersion and nonlinear effects robustness, have been theoretically analyzed from simulations carried out with the commercial software Optisystem v. 7.0, of the Canadian company Optiwave Systems Inc. The analysis has been applied to real optical links, with characteristics that, potentially, demand their use. A cost analysis, based on estimated values associated to devices required for implementing the formats investigated in this work, is also presented. Among the formats studied, those based on RZ (Return-to zero) presented the highest receiver sensitivity and best tolerance to nonlinear effects, in comparison to their equivalent formats, based on NRZ. However, they are less tolerant to dispersive effects and optical filtering cascading. The duobinary format (DB) has shown a weak performance in terms of sensitivity, though has been proved to be the most tolerant to chromatic dispersion and filtering cascading effects. Among all formats, the phase modulation ones presented the highest resistance against nonlinear and dispersive effects.

Esta dissertação apresenta uma análise realista de redes OCDMA (acesso múltiplo por divisão de código) baseadas em dois formatos de modulação distintos, qual sejam, OOK (chaveamento on-off) e PPM (modulação por posição de pulso). O desempenho desses formatos de modulação sob dois esquemas de codificação bidimensionais (2-D), isto é, pulsos únicos por linha (SPR) e múltiplos pulsos por linha (MPR) também são avaliados. Em ambos os casos, os efeitos simultâneos de muitos mecanismos dispersivos e ruídos (incluindo a interferência de acesso múltiplo, MAI) que prejudicam o desempenho geral do sistema foram também considerados. Outros mecanismos de degradação foram também incluídos, tais como o ruído de intensidade relativa (RIN) na etapa de transmissão, efeitos dispersivos da fibra óptica, como as dispersões de velocidade de grupo (GVD) e dos modos de polarização de primeira ordem (PMD), assim como os ruídos de batimento, APD, e térmicos na recepção. O efeito da GVD e PMD, bem como a influência dos ruídos, sobre o desempenho dos códigos SPR e MPR também são investigados. Outro efeito estudado nesta dissertação é a influência do fotodetetor APD sobre o ruído de batimento da rede OCDMA não-coerente. Para mitigar os ruídos do sistema e a BER, o algoritmo FEC RS (255,239) foi adotado em ambas as redes analisadas. Novas expressões para a taxa de erro de bit (BER) incluindo todos os ruídos e mecanismos de dispersão são apresentadas para os códigos SPR e MPR. Os resultados indicam que os esquemas de modulação OOK e PPM sem mecanismos adicionais de mitigação da MAI e de outros efeitos de ruídos não são suficientes para acomodar 32 usuários simultâneos em meio livre de erros (BER < \'10 POT.-12\'). Isto ocorre devido à alta BER na entrada do decodificador FEC, que afeta severamente a correção de erros na deteção. / This dissertation presents a comprehensive analysis of an OCDMA (optical code division multiple access) network based on two distinct modulation formats, namely, OOK (on-off keying) and PPM (pulse position modulation). We also investigate how each of these modulation formats performs under two distinct two dimensional (2-D) coding schemes, i.e., single-pulse per row (SPR) and multiple-pulse per row (MPR). For both cases, we have accounted for the simultaneous effect of many different dispersion and noise mechanisms (including multiple access interference, MAI) that impair the overall system performance. We have included the laser relative intensity noise (RIN) at the transmitter side, the fiber dispersive effects, such as group velocity dispersion (GVD) and first order polarization mode dispersion (PMD), as well as beat, APD, and thermal noises at the receiver side. The effect of GVD and PMD, as well as the influence of noises, on the performance of SPR and MPR codes is also investigated. Another effect studied in this dissertation is the influence of the avalanche photodetector (APD) photodetector on the beat noise of an incoherent OCDMA network. To mitigate systems noises and bit error rate (BER), we have adopted a FEC RS (255,239) algorithm in both networks investigated here. New expressions for the BER with all noises and dispersion mechanisms were also derived for the SPR and MPR code schemes. Results indicated that OOK and PPM modulation schemes without additional mechanisms to mitigate MAI and other noise effects are not sufficient to accommodate 32 simultaneous users in an error-free environment (BER < \'10 POT.-12\'). This occurs due to the already high BER at the FEC decoder input, which severely affects forward error corrections at the receiver side.

La demande en capacité liée à la transmission de tout type d’information (voix, vidéos, données, etc.) ne cesse de croître. Afin de répondre à cette demande croissante, de nouvelles générations de systèmes de communication multiplexés en longueur d’onde transmettant des débits élevés d’information par canal (100 Gbit/s ou plus) doivent être conçues. En plus des fibres ayant de très faibles pertes, des amplificateurs à fibre dopée à l’Erbium et du multiplexage en longueur d’onde, des technologies sont mises en place, comme notamment le multiplexage en polarisation, la détection cohérente, les formats de modulation multi-niveaux et plus récemment le multiplexage spatial. Des interrogations résident sur l’impact du multiplexage en polarisation ainsi qu’un développement vers des formats de modulation plus évolués incluant modulation de phase et multiplexage en polarisation. Dans cette thèse, afin de contribuer à l’augmentation du produit capacité x distance dans les systèmes de transmission Nx100 Gbit/s par fibre optique également multiplexés en polarisation et utilisant la détection cohérente, nous avons étudié d’une part, la mise en forme spectrale des signaux à l’émission pour augmenter la densité spectrale d’information (ISD: Information Spectral density). Dans cette optique, nous avons étudié l’impact du filtrage étroit gaussien du second ordre et de la mise en forme spectrale en racine de cosinus surélevé (RRC: Root Raised Cosine) sur les signaux émis dans le cas de modulations en Polarization Division Multiplexed-Quaternary Phase Shift Keying (PDM-QPSK) et Polarization-Switched-Quaternary Phase Shift Keying (PS-QPSK). Ceci a été réalisé en simulation numérique en considérant un espacement spectral entre les différents canaux variable. Nous avons montré qu’en tenant compte à la fois du facteur de qualité maximal et de la densité spectrale d’information, l’application de la mise en forme RRC sur des signaux modulés en PS-QPSK, fournit de meilleures performances de transmission dans une configuration où toute la dispersion est compensée en fin de propagation, pour toutes les valeurs d’espacement spectral étudiées. D’autre part, nous nous sommes intéressés aux effets non-linéaires qui limitent la portée de ces systèmes en dégradant pendant la propagation, les symboles émis, par les interactions entre des symboles d’un même canal, entre canaux ou modes de polarisation. La compréhension et la réduction de l’impact des effets non-linéaires est indispensable lorsqu’on veut utiliser certaines technologies pour augmenter la densité spectrale d’information. L’utilisation du multiplexage en polarisation par exemple, se heurte aux dégradations causées par les effets non-linéaires car de nouvelles interactions entre symboles sont présentes pendant la propagation. Par conséquent le développement des futurs systèmes ayant des débits plus élevés de 400 Gbit/s et 1 Tbit/s par canal passe par une diminution de l’impact des effets non-linéaires. Nous avons établi dans ce travail de thèse, des règles de conception permettant de réduire l’impact des effets non-linéaires entre polarisation dans les systèmes de transmission optiques considérés / The ever-increasing demand of capacity in very high bit rate coherent optical transmission systems has paved the way towards the investigation of several techniques such as the use of ultra-low loss fibers, Erbium doped fiber amplifiers, polarization and wavelength division multiplexing (WDM), coherent detection, multi-level modulation formats, spatial division multiplexing, etc. However, there are questions concerning polarization division multiplexing and a development towards some advanced modulation formats including phase modulation and polarization division multiplexing. In this thesis, in order to increase the capacity-by-distance product of future optical coherent systems using wavelength and polarization division multiplexing, we first study spectral shaping of the transmitted signals to increase the information spectral density. For this purpose, we have numerically investigated the multi-channel transmission performance of Polarization Switched Quadrature Phase Shift Keying (PSQPSK) and we have compared it to the performance of Polarization-Division-Multiplexed QPSK (PDM-QPSK), using Root Raised Cosine (RRC) spectral shaping, in the context of a flexible channel grid. In addition we have presented the advantage of PS-QPSK against PDM-QPSK as a function of the system parameters, while we have also discussed the benefit of a RRC spectral shaping against a tight filtering at the transmitter side with a 2nd order super-Gaussian-shaped filter. Furthermore, we have focused on nonlinear effects that limit the transmission distance by degrading the transmitted symbols during propagation. Analyzing and reducing the impact of nonlinear effects is essential when using technologies that increase the information spectral density such as polarization division multiplexing which causes new nonlinear effects due to additional interactions between symbols during the propagation through the fiber. Therefore a reduction of the impact of nonlinear effects is necessary for the development of future systems with higher bit rates of 400 Gbit/s and 1 Tbit/s per channel. We have established in this thesis, design rules to reduce the impact of nonlinear effects in the optical WDM transmission systems at 100 Gbit/s per channel that use polarization multiplexing

Esta dissertação apresenta uma análise realista de redes OCDMA (acesso múltiplo por divisão de código) baseadas em dois formatos de modulação distintos, qual sejam, OOK (chaveamento on-off) e PPM (modulação por posição de pulso). O desempenho desses formatos de modulação sob dois esquemas de codificação bidimensionais (2-D), isto é, pulsos únicos por linha (SPR) e múltiplos pulsos por linha (MPR) também são avaliados. Em ambos os casos, os efeitos simultâneos de muitos mecanismos dispersivos e ruídos (incluindo a interferência de acesso múltiplo, MAI) que prejudicam o desempenho geral do sistema foram também considerados. Outros mecanismos de degradação foram também incluídos, tais como o ruído de intensidade relativa (RIN) na etapa de transmissão, efeitos dispersivos da fibra óptica, como as dispersões de velocidade de grupo (GVD) e dos modos de polarização de primeira ordem (PMD), assim como os ruídos de batimento, APD, e térmicos na recepção. O efeito da GVD e PMD, bem como a influência dos ruídos, sobre o desempenho dos códigos SPR e MPR também são investigados. Outro efeito estudado nesta dissertação é a influência do fotodetetor APD sobre o ruído de batimento da rede OCDMA não-coerente. Para mitigar os ruídos do sistema e a BER, o algoritmo FEC RS (255,239) foi adotado em ambas as redes analisadas. Novas expressões para a taxa de erro de bit (BER) incluindo todos os ruídos e mecanismos de dispersão são apresentadas para os códigos SPR e MPR. Os resultados indicam que os esquemas de modulação OOK e PPM sem mecanismos adicionais de mitigação da MAI e de outros efeitos de ruídos não são suficientes para acomodar 32 usuários simultâneos em meio livre de erros (BER < \'10 POT.-12\'). Isto ocorre devido à alta BER na entrada do decodificador FEC, que afeta severamente a correção de erros na deteção. / This dissertation presents a comprehensive analysis of an OCDMA (optical code division multiple access) network based on two distinct modulation formats, namely, OOK (on-off keying) and PPM (pulse position modulation). We also investigate how each of these modulation formats performs under two distinct two dimensional (2-D) coding schemes, i.e., single-pulse per row (SPR) and multiple-pulse per row (MPR). For both cases, we have accounted for the simultaneous effect of many different dispersion and noise mechanisms (including multiple access interference, MAI) that impair the overall system performance. We have included the laser relative intensity noise (RIN) at the transmitter side, the fiber dispersive effects, such as group velocity dispersion (GVD) and first order polarization mode dispersion (PMD), as well as beat, APD, and thermal noises at the receiver side. The effect of GVD and PMD, as well as the influence of noises, on the performance of SPR and MPR codes is also investigated. Another effect studied in this dissertation is the influence of the avalanche photodetector (APD) photodetector on the beat noise of an incoherent OCDMA network. To mitigate systems noises and bit error rate (BER), we have adopted a FEC RS (255,239) algorithm in both networks investigated here. New expressions for the BER with all noises and dispersion mechanisms were also derived for the SPR and MPR code schemes. Results indicated that OOK and PPM modulation schemes without additional mechanisms to mitigate MAI and other noise effects are not sufficient to accommodate 32 simultaneous users in an error-free environment (BER < \'10 POT.-12\'). This occurs due to the already high BER at the FEC decoder input, which severely affects forward error corrections at the receiver side.

La demande en bande passante des systèmes de communication optique ne cesse de croitre. Des débits de données de l’ordre de plusieurs centaines de TBit/s sont attendus dans un futur proche. La photonique silicium est une technologie majeure pour faire face à ces besoins croissants. Sa compatibilité avec les technologies CMOS permet naturellement une co-intégration photonique/électronique sur les mêmes circuits. A court terme, l’augmentation des débits de données dans les générations futures de système de communication optique passe par l’utilisation de formats de modulation avancés, et l’augmentation du nombre de bits par symbole transmis. A plus long terme, de nouvelles techniques de multiplexage sont nécessaires. Le multiplexage de modes est actuellement une solution attractive à l’étude dans ce but.Dans ce travail de thèse, différents moyens pour implémenter ces nouveaux systèmes de communication optiques sont étudiés au niveau de l’émetteur. Ces travaux incluent dans une première partie la modélisation, conception et caractérisation des modulateurs silicium. Dans une seconde partie, de nouveaux composants pour manipuler les modes sur circuits intégrés photoniques sont proposés, conçus et caractérisés, avec pour application le multiplexage de modes.Une nouvelle méthode a été proposée pour la modélisation des modulateurs optiques silicium. Cette méthode permet de réduire le temps de simulation de 2 ordres de grandeur, en maintenant un bon niveau de précision. En utilisant ce modèle, des modulateurs basés sur des diodes PN latérales et interdigitées ont été conçus pour fonctionner en bande O des communications optiques. Les résultats expérimentaux ont permis la mise en évidence de diagrammes de l’œil avec des taux d’extinction de 10 dB pour des modulations de type OOK (ON-OFF Keying) à 10Gbit/s. De plus des modulations de type BPSK (Binary Phase Shift Keying) ont également été démontrées à 10Gbit/s.De nouveaux convertisseurs de modes et multiplexeurs ont été proposés, conçus, fabriqués et caractérisés, pour être utilisés dans des systèmes de multiplexage modal. Les résultats expérimentaux ont permis de mettre en évidence des fonctionnements large bande passante avec de grands taux d’extinction. / Bandwidth demand in optical communication systems is continually growing. Data rate values in the order of several hundreds of TBps are expected in the near future. In order to cope with those expectations silicon based technologies are believed to be the best suited. Its naturally compatibility with CMOS easily enables the electronics and photonics co-integration. In the short-term the way increase data rates in next generation optical communication systems goes through using advanced modulation format and increase symbol rates. In the long-term view, new multiplexing techniques will be required. In this sense, mode division multiplexing is nowadays an attractive approach under consideration.In this Thesis work, the way to implement these new optical communication schemes is studied from the transmitter point of view. It includes, on a first part the modeling, design and characterization of silicon modulators. And in a second part, it includes the proposition, design and characterization of novel mode handling devices for mode division multiplexing.A new way of modeling silicon modulators has been developed. This new model permits to reduce the computation time of modulator analysis up to two orders of magnitude, while maintaining a good level of accuracy. Using the model, modulators based on lateral PN junctions and interdigitated PN junctions were designed to work in the O-Band of optical communications. Characterization work has been performed on these modulators with good results. Wide-open OOK (On Off Keying) eye diagrams with 10 dB extinction ratio were obtained at 10GBps. Furthermore, BPSK (Binary Phase Shift Keying) modulation was also demonstrated at 10GBps.New kind of mode converters and multiplexers, intended to work as mode division multiplexing subsystems have been proposed, designed, fabricated and characterized. Measured results show broad bandwidth operation with high extinction ratio.

La détection cohérente combinée avec le traitement du signal s’est imposée comme le standard pour les systèmes de communications optiques longue distance à 100 Gb/s (mono-porteuse) et au-delà. Avec l'avènement des convertisseurs numérique-analogique à haute vitesse et haute résolution, la génération de formats de modulation d'ordre supérieure avec filtrage numérique est devenue possible, favorisant l’émergence de transmissions à forte densité spectrale. En outre, la généralisation des liaisons non gérées en dispersion permet une modélisation analytique du canal optique et favorise l'utilisation d’outils puissants de la théorie de l'information et du traitement du signal. En se fondant sur ces outils, de nouveaux formats de modulation à entrelacement temporel dits hybrides et formats multidimensionnels sont étudiés et mise en oeuvre expérimentalement. Leur impact sur les algorithmes de traitement du signal et sur le débit d'information atteignable est analysé en détail. La conception de transpondeurs de prochaine génération à 400 Gb/ s et 1 Tb/s reposant sur des signaux à débit-symbole élevé est également étudiée. Ces systèmes sont intéressants pour réduire le coût par bit en augmentant la capacité émise par transpondeur. L'élaboration d'algorithmes de traitement du signal avancés associés à l’utilisation de composants optoélectroniques à l'état de l'art ont permis la démonstration d’expériences records: d’une part la première transmission mono-porteuse à 400 Gb/s sur une distance transatlantique (pour une efficacité spectrale de 6 b/s/Hz) d’autre part la première transmission à 1 Tb/s basée sur la synthèse en parallèle de plusieurs tranches spectrales (8 b/s/Hz) / Coherent detection in combination with digital signal processing is now the de facto standard for long-haul high capacity optical communications systems operating at 100 Gb/s per channel and beyond. With the advent of high-speed high-resolution digital-to-analog converters, generation of high order modulation formats with digital pulse shaping has become possible allowing the increase of system spectral efficiency. Furthermore, the widespread use of transmission links without in-line dispersion compensation enables elegant analytical optical channel modeling which facilitates the use of powerful tools from information theory and digital signal processing. Relying on these aforementioned tools, the introduction of time-interleaved hybrid modulation formats, multi-dimensional modulation formats, and alternative quadrature amplitude modulation formats is investigated in high-speed optical transmission systems. Their impact on signal processing algorithms and achievable information rate over optical links is studied in detail. Next, the design of next generation transponders based on high symbol rate signals operating at 400 Gb/s and 1 Tb/s is investigated. These systems are attractive to reduce the cost per bit as more capacity can be integrated in a single transponder. Thanks to the development of advanced signal processing algorithms combined with state-of-the-art opto-electronic components, record high-capacity transmission experiments are demonstrated: the first single carrier 400 Gb/s transmission over transatlantic distance (at 6 b/s/Hz) and the first 1 Tb/s net data rate transmission based on the parallel synthesis of multiple spectral slices (at 8 b/s/Hz)

[ES] La red de sexta generación (6G) es la solución potencial para satisfacer los requisitos exponencialmente crecientes de los servicios y aplicaciones emergentes. La plataforma 6G espera ofrecer altas velocidades de datos, conectividad ultra alta y baja latencia en función de los indicadores clave de rendimiento (KPI) requeridos. La tecnología de comunicación por luz visible (VLC) representa una tecnología clave para la red 6G, pero requiere una técnica de modulación avanzada eficiente para cumplir con dichos requisitos. En las últimas décadas, las señales ópticas basadas en el esquema de multiplexación por división de frecuencia ortogonal (OFDM) han atraído mucha atención y se han convertido en la modulación más popular entre varios esquemas de acceso multiportadora, gracias a su robustez y simplicidad frente a la cancelación por trayectos múltiples utilizando el prefijo cíclico (CP). Una de las formas de onda más prometedoras para redes de próxima generación es la técnica de modulación Filter Bank MultiCarrier (FBMC). El principal beneficio del esquema FBMC es que no depende de CP y de un gran número de muestras de banda de guarda, por lo tanto, emplea varias funciones de pulso localizadas en el tiempo con una alta relación de supresión de lóbulos laterales, lo que permite mejorar la eficiencia espectral y el rendimiento del sistema como factores clave en las redes ópticas de próxima generación, y proporciona una buena alternativa a la técnica CP-OFDM. Esta Tesis pretende dar un paso adelante en la propuesta de formatos de modulación para ser utilizados en sistemas VLC como tecnología habilitadora en redes 6G. Por lo tanto, se propone el sistema Flip-FBMC con un algoritmo de truncamiento para ofrecer una transmisión de alta velocidad con baja latencia Flip-FBMC mediante el uso del algoritmo de transformación ortogonal isotrópica (IOTA) y la capa PHYsical para DYnamic AccesS y filtros de radio cognitiva (PHYDYAS). En esta Tesis se propone la ecualización multitap con el fin de mitigar la Interferencia imaginaria intrínseca (IMI) en un canal con perfiles de retardos elevado en sistemas VLC de interiores. Además, se ha mejorado rendimiento de error de las señales FBMC no coherentes mediante el análisis de la propiedad de la localización de tiempo-frecuencia con la función gaussiana extendida (EGF), donde el factor de dispersión desempeña un papel crucial en la determinación del equilibrio entre las características espectrales y la reconstrucción óptima de la calidad de la señal. Además, la Tesis proporciona el primer análisis teórico que informa de la degradación en la estimación para varios factores de clipping basada en el impacto del nivel de interferencia imaginario fuera de la zona de primer orden que no puede ser estimada mediante el preámbulo de IAM. Sin embargo, se debe enfatizar en el valor de la técnica Flip-FBMC/IAM para proporcionar el modelo unipolar en comparación con el uso del formato FBMC óptico polarizado con corriente continua (DCO-FBMC) que sufre una reducción en la estimación de la precisión. Por lo tanto, se ha demostrado el descenso del rendimiento con el sistema DCO-FBMC debido al IMI inducido fuera de los símbolos de orden cero, y que es más evidente cuando se requieren niveles bajos de corriente DC. Desde esta perspectiva, la técnica de repetición de tramas con señales Flip-FBMC ha demostrado ser una solución importante para minimizar la interferencia inducida. Por lo tanto, en esta Tesis, la modulación Flip-FBMC con repetición de tramas y perfil de filtro PHYDYAS se propone como un candidato viable para hacer frente al rango dinámico restringido del LED, en comparación con el rendimiento de los sistemas Flip-CP-OFDM y Flip-FBMC/IAM en futuras redes 6G basadas en acceso VLC. / [CA] La xarxa de sexta generació (6G) és la solució potencial per a satisfer els requisits exponencialment creixents dels servicis i aplicacions emergents. La plataforma 6G espera oferir altes velocitats de dades, connectivitat ultra alta i baixa latència en funció dels indicadors clau de rendiment (KPI) requerits. La tecnologia de comunicació per llum visible (VLC) representa una tecnologia clau per a la xarxa 6G, però requerix una tècnica de modulació avançada eficient per a complir amb estos requisits. En les últimes dècades, els senyals òptics basats en l'esquema de multiplexació per divisió de freqüència ortogonal (OFDM) han atret molta atenció i s'han convertit en la modulació més popular entre diversos esquemes d'accés multiportadora, gràcies a la seua robustesa i simplicitat enfront de la cancel·lació per trajectes múltiples utilitzant el prefix cíclic (CP). Una de les formes d'ona més prometedores per a xarxes de pròxima generació és la tècnica de modulació Filter Bank MultiCarrier (FBMC). El principal benefici de l'esquema FBMC és que no depén de CP i d'un gran nombre de mostres de banda de guarda, per tant, empra diverses funcions de pols localitzades en el temps amb una alta relació de supressió de lòbuls laterals, la qual cosa permet millorar l'eficiència espectral i el rendiment del sistema com a factors clau en les xarxes òptiques de pròxima generació, i proporciona una bona alternativa a la tècnica CP-OFDM. Esta Tesi pretén fer un pas avant en la proposta de formats de modulació per a ser utilitzats en sistemes VLC com a tecnologia habilitadora en xarxes 6G. Per tant, es proposa el sistema Flip-FBMC amb un algoritme de truncament per a oferir una transmissió d'alta velocitat amb baixa latència Flip-FBMC mitjançant l'ús de l'algoritme de transformació ortogonal isotròpica (IOTA) i la capa PHYsical per a DYnamic AccesS i filtres de ràdio cognitiva (PHYDYAS). En aquesta Tesi, es proposa l'equalització multitap per als sistemes VLC en interiors per a mitigar la interferència imaginària intrínseca (IMI) en un canal amb perfils de retards elevat. A més, el rendiment d'error dels senyals FBMC no coherents es millora mitjançant l'anàlisi de la propietat de la localització de temps-freqüència amb la funció gaussiana estesa (EGF), on el factor de dispersió exercix un paper crucial en la determinació de l'equilibri entre les característiques espectrals i la reconstrucció òptima de la qualitat del senyal. En tal escenari, a causa del rang dinàmic limitat del díode emissor de llum (LED), la millora de la precisió de l'estimació depén dels nivells de potència dels pseudopilots amb l'ús de l'arquitectura del Mètode d'Aproximació d'Interferència (IAM) i per tant, no és adequada en sistemes VLC d'il·luminació i comunicació. A més, la Tesi proporciona la primera anàlisi teòrica que informa de la degradació en l'estimació per a diversos factors de clipping basada en l'impacte del nivell d'interferència imaginari fora de la zona de primer orde que no pot ser estimada mitjançant el preàmbul de IAM. No obstant això, s'ha d'emfatitzar en el valor de la tècnica Flip-FBMC/IAM per a proporcionar el model unipolar en comparació amb l'ús del format FBMC òptic polaritzat amb corrent continu (DCO-FBMC) que patix una reducció en l'estimació de la precisió. Per tant, s'ha demostrat el descens del rendiment amb el sistema DCO-FBMC a causa del IMI induït fora dels símbols d'orde zero, i que és més evident quan es requerixen nivells baixos de corrent DC. Des d'esta perspectiva, la tècnica de repetició de trames amb senyals Flip-FBMC ha demostrat ser una solució important per a minimitzar la interferència induïda. Per tant, en esta Tesi, la modulació Flip-FBMC amb repetició de trames i perfil de filtre PHYDYAS es proposa com un candidat viable per a fer front al rang dinàmic restringit del LED, en comparació amb el rendiment dels sistemes Flip-CP-OFDM i Flip-FBMC/IAM en futures xarxes 6G basades en accés VLC. / [EN] The sixth generation (6G) network is the potential solution to meet the exponentially increasing requirements of the emerging services and applications. The 6G platform expects to offer high data rates, ultra-high connectivity, and low latency based on the required key performance indicators (KPIs). The visible light communication (VLC) technology represents a key technology for 6G network but requires an efficient advanced modulation technique to support such requirements. In the last decades, optical signals based on Orthogonal Frequency Division Multiplexing (OFDM) scheme has attracted a lot of attention and become the most popular modulation among several multicarrier access schemes, thanks to its robustness and simplicity against multipath fading using the cyclic prefix (CP). One of the most candidate waveforms that is considered as the promising modulation technique for the next generation requirements and applications is Filter Bank MultiCarrier (FBMC) multiplexing. The major benefit of FBMC scheme is non-reliance on CP and high numbers of guard band samples, thereby, it employs several well time-frequency localized pulse functions with high side-lobe suppression ratio instead, which allows enhancing the spectral efficiency and system performance as key factors in next generation optical networks, and provides a good alternative to CP-OFDM technique. This Thesis aims to make a step forward in proposing modulation formats to be used in VLC systems as enabling technology in 6G networks. Hence, Flip-FBMC system with a truncation algorithm is proposed to offer a high-speed transmission with low latency by tackling the doubled-overhead tails at the subframes of Flip-FBMC burst by the use of the isotropic orthogonal transformation algorithm (IOTA) and PHYsical layer for DYnamic AccesS and cognitive radio (PHYDYAS) filters. Multitap equalization is proposed in this Thesis for the sake of mitigating the intrinsic imaginary interference (IMI) over a channel with high delays profile for indoor VLC system. Moreover, the error performance of non-coherent FBMC signals is enhanced by analysing the property of time-frequency localization with Extended Gaussian Function (EGF), where the spreading factor plays a crucial role in determining the trade-off between the spectral features and optimal reconstruction of signal quality. In such scenario, due to the limited dynamic range of light emitting diode (LED), improving in the accuracy of estimation depends on the power-levels of pseudo pilots with the use of Interference Approximation Method (IAM) architecture. Thereby, the analysis reveals that IAM sequence is not suitable for a real transmission scenario due to high power of IAM over the payload data which conflicts with VLC purposes of illumination and communication simultaneously. Additionally, the Thesis provides the first theoretical analysis reporting the degradation of estimation accuracy for several clipping ratios based on the impact of imaginary interference level outside the first order neighbourhood zone that cannot be estimated by IAM preamble. However, the value of Flip-FBMC/IAM technique in providing the unipolar model must be emphasized compared to the use of Direct Current biased Optical FBMC (DCO-FBMC) format that suffers from a reduction in estimating accuracy. Thereby, the downfall performance with DCO-FBMC system has been reported because of the induced IMI that spreads out the first neighbourhood symbols, which is more evident when low levels of the added DC-bias are required. From such perspective, the frame repetition technique with Flip-FBMC signals has been demonstrated as a major solution for minimizing the induced interference. Therefore, in this Thesis, Flip-FBMC/frame repetition with PHYDYAS profile is proposed as a viable candidate to cope with the restricted dynamic range of the LED, compared to the performance for each Flip-CP-OFDM and Flip-FBMC/IAM system in future 6G networks based on VLC access. / Bahaaelden, MS. (2024). Novel 5G-Modulation Formats and Their Application in Optical Wireless Communications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/204634