[pt] Neste trabalho realizamos uma prova da viabilidade de um sistema de comunicação óptica com capacidade de transmissão de 50 Gbit/s em uma largura de banda de 50 GHz utilizando o legado dos sistemas com taxas de 10 Gbit/s. Uma série de configurações experimentais foi testada em uma ordem de complexidade crescente para verificar separadamente as etapas e as técnicas aplicadas para o aumento da capacidade de transmissão de dados e a eficiência espectral. Em alguns casos, a curva característica resultante da configuração backto- back do analisador de taxa de erro de bit média foi utilizada como referência para comparação das configurações experimentais realizadas durante o trabalho. / [en] In this work we perform a proof of feasibility of 50 Gbit/s transmission within a 50 GHz optical bandwidth exploring the 10 Gbit/s legacy. A series of experimental configurations were tested in an order of increasing complexity to verify separately the steps and applied techniques for increasing data transmission capacity and spectral efficiency. In some cases, the comparison of experimental configuration was made using the back-to-back configuration of the Bit Error Rate Tester.

Neste trabalho propomos e analisamos algoritmos de alocação dinâmica de banda para rede óptica passiva (PON) de acesso padrão GPON (Gigabit PON). Estes algoritmos utilizam dados oriundos de SLA (service level agreement) para gerenciar a alocação de banda e classificar em 4 contêineres de tráfego (T-CONT) o tráfego gerado em 16 ONUs (optical network unit). Na transmissão upstream é utilizada a técnica de multiplexação por divisão de tempo (TDM) para gerenciar o acesso ao meio, evitando colisões. O primeiro algoritmo proposto aloca banda garantida para as ONUs e distribui a banda não utilizada de acordo com critério baseado em três SLAs. A taxa de bit upstream é 1,25 Gbps e o desempenho do algoritmo é analisado com base na variação do atraso de pacotes em função do tráfego gerado nas ONUs. O segundo algoritmo proposto utiliza ponderação de tráfego. Neste, analisamos o comportamento dos atrasos e a quantidade de banda solicitada e atendida por ONU quando as bandas garantida e extra são alteradas. Por fim, acrescentamos em nossa implementação um intervalo para o processamento do algoritmo de alocação dinâmica de banda (DBA) e resposta do hardware relacionado ao ciclo de interrogação. Então, analisamos o atraso de pacotes quando variamos o intervalo de processamento do DBA. Ao final, propomos uma solução preliminar para minimizar estes atrasos. Os resultados obtidos por meio de simulação computacional mostram a versatilidade dos algoritmos. / In this work we propose and analyze the performance of dynamic bandwidth allocation algorithms for optical passive networks (PON) in GPON standard (Gigabit PON). These algorithms use data from SLA (service level agreement) to manage bandwidth allocation and classify in 4 traffic containers (T-CONT) the traffic generated by 16 ONUs (optical network unit). In the upstream transmission the time division multiplexing (TDM) technique is used to manage the medium access, avoiding collisions. The first proposed algorithm allocates guaranteed bandwidth for the ONUs and distributes the bandwidth not used according to the criteria based on three SLAs. The upstream bit rate is 1.25 Gbps and the algorithm performance is analyzed based on the packets delay variation versus the traffic generated by ONUs. The second proposed algorithm uses weighted traffic. In this, we analyze the delay performance and the required bandwidth for each ONU and how much it is served when the guaranteed and extra bandwidth are changed. Finally, we added in our implementation an interval for the processing of the dynamic bandwidth allocation algorithm (DBA) and response of the hardware related to the interrogation cycle. In the end, we propose a preliminary solution to minimize these delays. The results obtained by means of computational simulation show the versatility of the algorithms.

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.

Este trabalho faz uma extensa e detalhada análise de sistemas ópticos coerentes baseados na tecnologia de acesso múltiplo por divisão de código, com ênfase naqueles em que o processo de codificação do sinal óptico é realizado por meio de deslocamentos de fase no domínio espectral (SPECTS-OCDMA). Apesar de ser um estudo numérico, esforços são concentrados na tentativa de aproximar estes cenários simulados aos cenários mais realistas, implementados em laboratórios. Nesse contexto, levando em consideração o impacto dos efeitos dispersivos e nãolineares da fibra óptica em sistemas SPECTS-OCDMA, são modelados diversos dispositivos que constituem o sistema de recepção do sinal óptico (nonlinear optical loop mirror e nonlinear thresholder), e mostradas suas influências no desempenho do sistema. Isso permite identificar o exato grau de interferência que cada código de uma determinada família de códigos causa nos outros códigos da mesma família. Esta análise é diferente de tudo previamente reportado para os sistemas OCDMA, porque até então sempre se supôs que todos os códigos de uma mesma família têm o mesmo desempenho. Também é demonstrado que uma escolha ótima do conjunto de códigos reduz consideravelmente a taxa de erro de bit (BER). Os conjuntos ótimos de códigos são obtidos em termos do padrão de interferência causado por todos os códigos no usuário de interesse. Isso permite mostrar que o uso de conjuntos ótimos de códigos não só melhora o desempenho geral do sistema em termos de BER, mas também elimina a quebra de ortogonalidade (nunca levada em consideração em análises anteriores de sistemas OCDMA) devido à diafonia (crosstalk). Este aspecto também é resolvido com detalhes neste trabalho uma vez que ele compromete seriamente a segurança do sistema contra espiões (intencionais e não intencionais). Ainda visando a modelagem de dispositivos voltados para sistemas ópticos coerentes, também foi investigado neste trabalho a evolução de pulsos ultracurtos e de alta potência (com fase modulada no domínio espectral) em fibras altamente não-lineares. Esse fenômeno conhecido por geração de luz supercontínua é caracterizado por um forte alargamento espectral induzido por efeitos não-lineares no meio óptico, e que encontra uma grande variedade de aplicações, como tomografia por coerência óptica, espectroscopia e metrologia de frequência. Entretanto, o ajuste do espectro obtido após a propagação para uma dessas aplicações requer uma escolha correta da fibra óptica e da fonte de pulsos ultracurtos utilizados. Uma vez que esses parâmetros estão definidos, fica muito difícil conseguir um ajuste fino do espectro obtido. Dessa forma, a vantagem da utilização de pulsos modulados é a possibilidade de se realizar uma sintonia fina do espectro obtido para uma aplicação desejada. Além disso, essa técnica permite a geração de pentes de frequências ópticos (optical frequency combs) sintonizáveis. / In this work we perform a comprehensive analysis of a spectral phase-encoded time spreading optical code division multiple access (SPECTS-OCDMA) system. Despite being a numerical study, efforts were concentrated on the investigation of more realistic scenarios using as much information as possible from implemented test-beds in laboratories. In this context, after take into account the impact of dispersive and nonlinear effects of optical fiber in SPECTS-OCDMA systems, some devices of the optical signal reception subsystem are modeled (nonlinear optical loop mirror and nonlinear thresholder), and their influences on system performance are shown. This allowed for the first time in the OCDMA literature the identification of the exact degree of interference that each code of a particular family of codes causes on other codes of the same family. This analysis considerably advances the common sense adopted in the literature in which all codes of the same family perform equally. It is demonstrated that an adequate (optimal) choice of codes can reduce considerably the bit error rate (BER). The optimal code-sets are obtained in terms of the interference pattern caused by every code on the code of interest. Furthermore, it is shown that the use of optimal code-sets not only improves the overall system performance in terms of BER, but also eliminates the orthogonality failure (never accounted for in previous OCDMA analysis) due to crosstalk. This issue is also addressed in details in this work since it seriously compromises the security of the system against (intentional or unintentional) eavesdroppers. Still aiming at modeling devices for coherent optical systems, it is investigated the evolution of ultrashort high-power pulses (spectrally phase modulated) in high nonlinear fibers. This phenomenon known as supercontinuum generation is characterized by strong spectral broadening induced by nonlinear effects in optical medium, and finds a wide range of applications such as optical coherence tomography, spectroscopy and frequency metrology. However, tailoring the supercontinuum (SC) spectra to a specific application requires the correct choice of the optical fiber and the ultrashort pulse source. Once these parameters are defined, it becomes very difficult to achieve a fine tune of the generated spectra. Therefore, an alternative is to phase modulate the input pulse to adjust the generated spectra to a specific application. Also, we show that this technique allow us to generate tunable optical frequency combs simply by adjusting the modulation parameters.

A débit de données élevé, typiquement supérieur à 10 Gsymboles/s, les lignes de<p>télécommunication optique à fibre monomode souffrent de façon accrue des distorsions<p>inhérentes à la fibre et à l’architecture de transmission. Nous pouvons classer les<p>effets de fibre en plusieurs catégories:<p>– Les effets linéaires. La dispersion chromatique est entraînée par la dépendance en<p>fréquence de l’indice de réfraction de la fibre. Il en résulte un élargissement des<p>bits optiques. La dispersion des modes de polarisation prend son origine dans<p>la biréfringence de la fibre. La modélisation de cet effet est compliquée par son<p>caractère stochastique et variable dans le temps.<p>– Les effets non linéaires prennent leur origine dans un indice de réfraction de<p>fibre qui dépend du champ optique. Ces effets peuvent être classés en deux<p>catégories. Premièrement, les effets intérieurs à un canal dont le plus influant<p>est l’automodulation de phase qui découle de l’effet Kerr optique :l’intensité<p>d’une impulsion lumineuse influence sa propre propagation. Deuxièmement, il<p>existe des conséquences de l’effet Kerr par lesquelles les différents canaux, se<p>propageant au sein de la même fibre, s’influencent mutuellement. Le phénomène<p>le plus influent parmi ces derniers est la modulation de phase croisée :l’intensité<p>d’un canal influence la propagation dans un canal voisin.<p>– Les pertes par diffusion Rayleigh sont compensées par les amplificateurs distribués<p>le long de la ligne de transmission. L’amplification optique par l’intermédiaire<p>d’émission stimulée dans des dispositifs dopés aux ions Erbium est<p>accompagnée d’émission spontanée amplifiée. Ceci entraîne la présence d’un<p>bruit blanc gaussien se superposant au signal à transmettre.<p>– La gestion des canaux dans le réseau optique implique la présence dans les noeuds<p>du réseau de filtres de sélection, des multiplexeurs et démultiplexeurs.<p>Nous examinerons aussi les effets de ligne non inhérents à la fibre mais à l’architecture<p>de transmission. Les modèles de l’émetteur et du récepteur représentent les imperfections<p>d’implémentation des composants optiques et électroniques.<p>Un premier objectif est de définir et évaluer un format de modulation robuste aux<p>imperfections introduites sur le signal par la fibre optique et par l’émetteur/récepteur.<p>Deux caractéristiques fondamentales du format de modulation, determinants pour la<p>performance du système, sont étudiés dans ce travail :<p>– La forme d’ onde. Les symboles complexes d’information sont mis en forme par<p>un filtre passe-bas dont le profil influence la robustesse du signal vis-à-vis des<p>effets de ligne.<p>– La distribution des fréquences porteuses. Les canaux de communication sont<p>disposés sur une grille fréquentielle qui peut être définie de manière électronique<p>par traitement de signal, de manière optique ou dans une configuration hybride.<p>Lorsque des porteuses optiques sont utilisées, le bruit de phase relatif entre lasers<p>entraîne des effets d’ influence croisée entre canaux. En revanche, les limites des<p>implémentations électroniques sont données par la puissance des architectures<p>numériques.<p>Le deuxième objectif est de concevoir des techniques de traitement numérique du<p>signal implémentées après échantillonnage au récepteur afin de retrouver l’information<p>transmise. Les fonctions suivantes seront implémentées au récepteur :<p>– Les techniques d’estimation et d’égalisation des effets linéaires introduits par la<p>fibre optique et par l’émetteur et le récepteur. Le principe de l’égalisation dans<p>le domaine fréquentiel est de transformer le canal convolutif dans le domaine<p>temporel en un canal multiplicatif qui peut dès lors être compensé à une faible<p>complexité de calcul par des multiplications scalaires. Les blocs de symboles<p>émis doivent être rendus cycliques par l’ajout de redondance sous la forme d’un<p>préfixe cyclique ou d’une séquence d’apprentissage. Les techniques d’égalisation<p>seront comparées en termes de performance (taux d’erreurs binaires, efficacité<p>spectrale) et en termes de complexité de calcul. Ce dernier aspect est particulièrement<p>crucial en vue de l’optimisation de la consommation énergétique du<p>système conçu.<p>– Les techniques de synchronisation des signaux en temps/fréquence. Avant de<p>pouvoir égaliser les effets linéaires introduits dans la fibre, le signal reçu devra<p>être synchronisé en temps et en fréquence sur le signal envoyé. La synchronisation<p>est généralement accomplie en deux étapes principales :l’acquisition réalisée<p>avant de recevoir les symboles d’information don’t l’objectif est une première<p>estimation/compensation des effets de manière "grossière", le tracking réalisé en<p>parallèle à l’estimation des symboles d’information dont l’objectif est l’estimation<p>/compensation des effets de manière "fine". Les algorithmes d’acquisition et<p>de tracking peuvent nécessiter l’envoi d’informations connues du récepteur.<p>– Les techniques d’estimation et de compensation des imperfections de fonctionnement<p>de l’émetteur et du récepteur. Une structure de compensation des effets<p>introduits par les composants optiques et électroniques sera développée afin de<p>relâcher les contraintes d’implémentation de l’émetteur et du récepteur.<p>Etant donné la très haute cadence à laquelle les échantillons du signal sont produits<p>(plusieurs dizaines de Gech/s), une attention particulière est portée à la complexité de<p>calcul des algorithmes proposés. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

This work deals with questions of space assembling of several optics beams. There are mentioned the base features and values of space distribution of beam intensity in laser beam. The forms of diffusion of space localized light that is described by beam optics. There is a characterization of Gaussian beam, and diffraction of several beams. There is mentioned a simulation an assembling of two and more beams. It contains model of assembling incoherent beams. The work also includes suggestion of final layout of laser beams, which form optical transmitter with radiating characteristics, resistant to defects evoked by atmosphere.

Tato diplomová práce pojednává o charakteristikách laserových diod, difrakcí a o vlastnostech gausovského svazku. Je určen útlum vazby vysílací dioda - vysílací apertura v závislosti na velikostech apertury a na velikosti svazku v programu MATLAB. Jsou stanoveny optimální parametry vazby apertura-dioda.

The dissertation thesis deals with a free space optical links, especially is focused directly to the transmission optical beams. The influence of environmental conditions like atmospheric turbulence, buildings movement and vibration is described. As a possibility to reduce these undesirable influences, the generation of the transmission beam by the help of the two-mode optical fiber is proposed. A possibility to drive the shape of the resulting transmission beam by means of the change of power ration of individual modes in fiber is described. The coherence features of the proposed beam are analyzed considering the possibility to reduce the influence of atmospheric turbulence. In the thesis there are introduced beam quality parameters that enable to evaluate the quality of the optical beam for the free space optical link. These parameters give the relationship between the shape of the optical beam and the power balance of the optical link and the statistical evaluation of the optical link.

This dissertation documents works on two projects, which are broadly related to photonic integration using III-V semiconductor platform for fiber-based optical communication. Our principal project aims to demonstrate continuous variable quantum key distribution (CV-QKD) with InP-based photonic integrated cir cuit at the 1550 nanometer of optical wavelength. CV QKD protocols, in which the key is encoded in the quadrature variables of light, has generated immense interest over the years because of its compatibility with the existing telecom infrastructure. In this thesis, we have proposed a design of a photonic inte grated circuit potentially capable of realizing this protocol with coherent states of light. From the practical perspective, we have basically designed an optical transmitter and an optical receiver capable of carrying out coherent communi cation via the optical fiber. Initially, we established a mathematical model of the transceiver system based on the optical transfer matrix of the foundry spe cific (Fraunhofer Heinrich Hertz Institute-Germany) building blocks. We have shown that our chip design is versatile in the sense that it can support multiple modulation schemes. Based on the mathematical model, we estimated the link budget to assess the feasibility of on-chip implementation of our protocol. Then we ran a circuit level simulation using the process design kit provided by our foundry to put our analysis on a better footing. The encouraging result from this step prompted us to generate the mask layout for our transceiver chips, which we eventually submitted to the foundry. The other project in the thesis grew out of a collaboration with one of our industry partners. The goal of the project is to enhance the performance of a distributed feedback laser emitting at the 1310 nanometer of optical wavelength by optimizing its design. To that end, we first derived the expression for transmission and reflection spectrum for the laser cavity. Those expressions contained parameters which needed to be obtained from the transverse and the longitudinal mode analysis of the laser. We performed the transverse mode analysis and the longitudinal mode analysis with commercially available numerical solvers. Those mode profiles critically depend on the grating physical parameters. Therefore by tweaking grating dimensions one can control the transmission characteristics of the laser.

To accommodate the growing demand on higher speeds, low latencies and low energy consumption, the interconnections within and between data centers are supposed to be implemented as optical fiber and waveguide interconnects in future. Optical fiber interconnects provide several advantages over their electrical counterparts as they enable higher bandwidth densities and lower losses at high frequencies over distances longer than few centimeters. However, nowadays optical fiber interconnects are usually not very energy-efficient. The systems in optical networks are mostly optimized for running at their peak performance to transmit the information with the highest available error-free data rate. But the work load of a processor system and hence of an optical link is not constant and varies over time due to the demand of the running applications and users. Therefore, optical interconnects consume the same high power at all times even if lower performance is required. In this paper a new method for the tuning of optical interconnects for on-board and board-to-board optical communication is described. In this way the performance of the transceiver systems of the link is adapted to the present transmission workload and link requirements. If for example lower data rates are required, the bandwidth and therefore the power consumption of the systems can be reduced. This tuning is enabled by the integrated circuitry of the optical link. Different methods for such an adaptive tuning are described and several practical examples are reviewed. By using adaptive bandwidth reduction in the circuits, more than 50 % of the consumed power can be saved. These savings can result in tremendous reductions of the carbon footprint and of the operating costs produced by data centers.