A evolução das redes ópticas para atender o crescimento da demanda por largura de banda tem estimulado a busca por uma maior eficiência na utilização da largura de faixa disponível. O sucesso da implementação prática da técnica de acesso múltiplo por divisão de código (CDMA) em sistemas de comunicações móveis também despertou o interesse por aplicações em redes ópticas (OCDMA). Atributos únicos tais como capacidade flexível sob demanda, segurança na comunicação e alta escalabilidade, incentivaram significativamente as pesquisas. Neste contexto, este trabalho apresenta, primeiramente, uma revisão de várias configurações OCDMA propostas na literatura para qualificar e quantificar códigos válidos, com ênfase nas propriedades de correlação. Em seguida, realiza uma modelagem de sistema óptico abrangendo os subsistemas principais de geração, transmissão e recepção de sinal. O impacto das degradações, referentes à fibra óptica e aos diversos dispositivos que constituem o sistema, é então avaliado e sua influência sobre o desempenho de algumas configurações de codificação é investigado. O conhecimento da forma e das condições de manifestação destas degradações poderá servir de base ao processamento de sinal óptico à luz dos esquemas de codificação. Uma discussão sobre qualidade de serviço (QoS) e sobre flexibilização da aplicação OCDMA em sistemas de comunicação óptica também são também abordadas. / The evolution of optical networks verified in the last few years has been characterized by the search for better bandwidth utilization efficiency. The successful implementation of practical code division for multiple access techniques (CDMA) in mobile communications systems has stimulated new investigations on this topic, particularly in the optical domain (optical CDMA). This is justified due to some remarkable attributes of this technology, such flexibility in code design, capacity on demand, safety, and high scalability. In this context, this dissertation presents, initially, a comprehensive review of several code configurations for OCDMA proposed in the literature, with emphasis particularly on the correlation and users availability properties. Next, it describes the modeling of an optical system consisting of the following three subsystems: generation, transmission, and signal detection. The penalties imposed to the optical codes by the propagating medium, as well as by the devices employed in the system, are accounted for and their influence on the performance of some coding configurations is investigated. The knowledge of how and when these penalties will affect the system is crucial in optical signal processing based on codification schemes. Finally, this work also addresses some aspects related to quality of service (QoS) and flexibility of the OCDMA technology in optical communications systems.

Neste trabalho analisamos e propomos a utilização de TDM (Time Division Multiplexing) nativo canalizado/estruturado em redes PON (Passive Optical Network) com padrão GPON (Gigabit Passive Optical Network), com ênfase na estrutura de transmissão do legado das redes de telefonia. O objetivo principal é obter um aumento na eficiência de banda transmitida através da fragmentação de sinais E1 sem que seja necessário o uso de técnicas de emulação de circuito (que reduzem a eficiência de banda devido à adição de cabeçalhos). Inicialmente, é descrito o transporte TDM em redes GPON, como efetuado pelos equipamentos comerciais atuais através de duas técnicas: CES - Circuit Emulation Service e TDM nativo não estruturado. Em seguida, é introduzido o conceito de comutação digital visando sua aplicação no transporte TDM nativo estruturado em redes GPON. Nesta etapa, é proposta uma solução para este transporte, é descrito o protocolo utilizado bem como seu funcionamento. Por fim, como prova de conceito, é apresentada uma implementação em HDL (Hardware Description Language) para FPGA (Field Programmable Gate Array). / In this work we analyze and propose the use of native channeled /structured TDM (Time Division Multiplexing) in GPON (Gigabit Passive Optical Network), with emphasis on the structure for transmission of the telephone network legacy. The main target is to achieve an increase in transmitted bandwidth efficiency by fragmenting E1 signals, thus avoiding the use of circuit emulation techniques (which reduce the bandwidth efficiency due to overhead addition). Initially, it is described in TDM transport in GPON networks, as it is performed in present commercial equipment by two techniques: CES - Circuit Emulation Service and Native TDM - unstructured. Next, we introduce the concepts of digital switching aiming its application on the transport of native and structured TDM in GPON. At this stage, we propose a transport solution, describe its protocol and functionalities. Finally, for concept proof, we present an implementation in HDL (Hardware Description Language) meant to FPGA (Field Programmable Gate Array) application.

In den letzten Jahrzehnten ist das globale Kommunikationssystem in einem immer größerem Maße ein integraler Bestandteil des täglichen Lebens geworden. Optische Kommunikationssysteme sind die technologische Basis für diese Entwicklung. Nur Fasern können die riesige benötigte Bandbreite bereitstellen. Während für die ersten optischen Übertragungssysteme die Faser als "flacher" Kanal betrachtet werden konnte, machen Wellenlängenmultiplex und steigende Übertragungsraten die Einbeziehung von immer mehr physikalischen Effekten notwendig. Bei einer Erhöhung der Kanaldatenrate auf 40 Gbit/s und mehr ist die statische Kompensation von chromatischer Dispersion nicht mehr ausreichend. Die intrinsische Toleranz der Modulationsformate gegenüber Dispersion nimmt quadratisch mit der Symbolrate ab. Daher können beispielsweise durch Umwelteinflüsse hervorgerufene Dispersionsschwankungen die Dispersionstoleranz der Modulationsformate überschreiten. Dies macht eine adaptive Dispersionskompensation notwendig, was gleichzeitig auch Dispersionsmonitoring erfordert, um den adaptiven Kompensator steuern zu können. Vorhandene Links können mit Restdispersionskompensatoren ausgestattet werden, um sie für Hochgeschwindigkeitsübertragungen zu ertüchtigen. Optische Kompensationstechniken sind unabhängig von der Kanaldatenrate. Daher wird eine Erhöhung der Datenrate problemlos unterstützt. Optische Kompensatoren können WDM-fähig gebaut werden, um mehrere Kanäle auf einmal zu entzerren. Das Buch beschäftigt sich mit optischen Delay-Line-Filtern als eine Klasse von optischen Kompensatoren. Die Filtersynthese von solchen Delay-Line-Filtern wird behandelt. Der Zusammenhang zwischen optischen Filtern und digitalen FIR-Filtern mit komplexen Koeffizienten im Zusammenhang mit kohärenter Detektion wird aufgezeigt. Iterative und analytische Methoden, die die Koeffizienten für dispersions- und dispersions-slope-kompensierende Filter produzieren, werden untersucht. Genauso wichtig wie die Kompensation von Dispersion ist die Schätzung der Dispersion eines Signals. Mit Delay-Line-Filtern können die Restseitenbänder eines Signals genutzt werden, um die Dispersion zu messen. Alternativ kann nichtlineare Detektion angewandt werden, um die Pulsverbreiterung, die hauptsächlich von der Dispersion herrührt, zu schätzen. Mit gemeinsamer Dispersionskompensation und Dispersionsmonitoring können Dispersionskompensatoren auf die Signalverzerrungen eingestellt werden. Spezielle Eigenschaften der Filter zusammen mit der analytischen Beschreibung können genutzt werden, um schnelle und zuverlässige Steueralgorithmen zur Filtereinstellung bereitzustellen. Schließlich wurden Prototypen derartiger faseroptischen Kompensatoren von chromatischer Dispersion und Dispersions-Slope hergestellt und charakterisiert. Die Einheiten und ihr Systemverhalten wird gezeigt und diskutiert. / Over the course of the past decades, the global communication system has become a central part of people's everyday lives. Optical communication systems are the technological basis for this development. Only fibers can provide the huge bandwidth that is required. Where the fiber could be regarded as a flat channel for the first optical transmission systems wavelength multiplexing and increasing line rates made it necessary to take more and more physical effects into account. When the line rates are increased to 40 Gbit/s and higher static chromatic dispersion compensation is not enough. The modulation format's intrinsic tolerance for dispersion decreases quadratically with the symbol rate. Thus, environmentally induced chromatic dispersion fluctuations may exceed the dispersion tolerance of the modulation formats. This makes an adaptive dispersion compensation necessary implying also the need for a monitoring scheme to steer the adaptive compensator. Legacy links that are CD-compensated by DCFs can be upgraded with residual dispersion compensators to make them ready for high speed transmission. Optical compensation is independent from the line rate. Hence, increasing the data rates is inherently supported. Optical compensators can be built WDM ready compensating multiple channels at once. The book deals with optical delay line filters as one class of optical compensators. The filter synthesis of such delay line filters is addressed. The connection between optical filters and digital FIR filters with complex coefficients that are used in conjunction with coherent detection could be shown. Iterative and analytical methods that produce the coefficients for dispersion (and also dispersion slope) compensating filters are researched. As important as the compensation of dispersion is the estimation of the dispersion of a signal. Using delay line filters, the vestigial sidebands of a signal can be used to measure the dispersion. Alternatively, nonlinear detection can be used to estimate the pulse broadening which is caused mainly by dispersion. With dispersion compensation and dispersion monitoring, dispersion compensators can be adapted to the signal's impairment. Special properties of the filter in conjunction with an analytical description can be used to provide a fast and reliable control algorithm for setting the filter to a given dispersion and centering it on a signal. Finally, prototypes of such fiber optic chromatic dispersion and dispersion slope compensation filters were manufactured and characterized. The device and system characterization of the prototypes is presented and discussed.

A evolução das redes ópticas para atender o crescimento da demanda por largura de banda tem estimulado a busca por uma maior eficiência na utilização da largura de faixa disponível. O sucesso da implementação prática da técnica de acesso múltiplo por divisão de código (CDMA) em sistemas de comunicações móveis também despertou o interesse por aplicações em redes ópticas (OCDMA). Atributos únicos tais como capacidade flexível sob demanda, segurança na comunicação e alta escalabilidade, incentivaram significativamente as pesquisas. Neste contexto, este trabalho apresenta, primeiramente, uma revisão de várias configurações OCDMA propostas na literatura para qualificar e quantificar códigos válidos, com ênfase nas propriedades de correlação. Em seguida, realiza uma modelagem de sistema óptico abrangendo os subsistemas principais de geração, transmissão e recepção de sinal. O impacto das degradações, referentes à fibra óptica e aos diversos dispositivos que constituem o sistema, é então avaliado e sua influência sobre o desempenho de algumas configurações de codificação é investigado. O conhecimento da forma e das condições de manifestação destas degradações poderá servir de base ao processamento de sinal óptico à luz dos esquemas de codificação. Uma discussão sobre qualidade de serviço (QoS) e sobre flexibilização da aplicação OCDMA em sistemas de comunicação óptica também são também abordadas. / The evolution of optical networks verified in the last few years has been characterized by the search for better bandwidth utilization efficiency. The successful implementation of practical code division for multiple access techniques (CDMA) in mobile communications systems has stimulated new investigations on this topic, particularly in the optical domain (optical CDMA). This is justified due to some remarkable attributes of this technology, such flexibility in code design, capacity on demand, safety, and high scalability. In this context, this dissertation presents, initially, a comprehensive review of several code configurations for OCDMA proposed in the literature, with emphasis particularly on the correlation and users availability properties. Next, it describes the modeling of an optical system consisting of the following three subsystems: generation, transmission, and signal detection. The penalties imposed to the optical codes by the propagating medium, as well as by the devices employed in the system, are accounted for and their influence on the performance of some coding configurations is investigated. The knowledge of how and when these penalties will affect the system is crucial in optical signal processing based on codification schemes. Finally, this work also addresses some aspects related to quality of service (QoS) and flexibility of the OCDMA technology in optical communications systems.

Neste trabalho analisamos e propomos a utilização de TDM (Time Division Multiplexing) nativo canalizado/estruturado em redes PON (Passive Optical Network) com padrão GPON (Gigabit Passive Optical Network), com ênfase na estrutura de transmissão do legado das redes de telefonia. O objetivo principal é obter um aumento na eficiência de banda transmitida através da fragmentação de sinais E1 sem que seja necessário o uso de técnicas de emulação de circuito (que reduzem a eficiência de banda devido à adição de cabeçalhos). Inicialmente, é descrito o transporte TDM em redes GPON, como efetuado pelos equipamentos comerciais atuais através de duas técnicas: CES - Circuit Emulation Service e TDM nativo não estruturado. Em seguida, é introduzido o conceito de comutação digital visando sua aplicação no transporte TDM nativo estruturado em redes GPON. Nesta etapa, é proposta uma solução para este transporte, é descrito o protocolo utilizado bem como seu funcionamento. Por fim, como prova de conceito, é apresentada uma implementação em HDL (Hardware Description Language) para FPGA (Field Programmable Gate Array). / In this work we analyze and propose the use of native channeled /structured TDM (Time Division Multiplexing) in GPON (Gigabit Passive Optical Network), with emphasis on the structure for transmission of the telephone network legacy. The main target is to achieve an increase in transmitted bandwidth efficiency by fragmenting E1 signals, thus avoiding the use of circuit emulation techniques (which reduce the bandwidth efficiency due to overhead addition). Initially, it is described in TDM transport in GPON networks, as it is performed in present commercial equipment by two techniques: CES - Circuit Emulation Service and Native TDM - unstructured. Next, we introduce the concepts of digital switching aiming its application on the transport of native and structured TDM in GPON. At this stage, we propose a transport solution, describe its protocol and functionalities. Finally, for concept proof, we present an implementation in HDL (Hardware Description Language) meant to FPGA (Field Programmable Gate Array) application.

This master’s thesis deals with the impact of atmospheric turbulence on phase changes of a free space optical signal. This problematic is investigated by the interferometric method. A part of the thesis is focused on the phenomenon of atmospheric turbulence. Then the physical effect of interference is discussed and optical interferometers are described. The experimental part of the thesis is focused on measurement of phase shift of optical signal by interferometric method. The result of the thesis is to determine how phase shift of an optical beam depends on the strength of turbulence.

[pt] Este trabalho apresenta o estudo de comunicação óptica quântica no infravermelho, utilizando um sistema híbrido fibra-óptica – espaço-livre, como prova de princípio para o estabelecimento de chaves secretas a fim de utilização em criptografia do tipo one-time pad. Ao modular a polarização da luz de um laser em polarizações ortogonais, podem-se codificar os bits clássicos 1 e 0 em cada uma dessas polarizações, sendo detectadas por detectores contadores de fótons únicos, e, assim, utilizar o canal quântico para transmissão dos bits quânticos entre dois interlocutores, utilizandoos para o estabelecimento da chave criptográfica, que pode ser usada em qualquer tipo de informação a ser transmitida por um canal clássico ou quântico. Ao realizar a transmissão em espaço-livre, sujeita a variações climáticas, como temperatura atmosférica, luz solar, presença de nuvens, chuva e vento, foi também estudada a influência destes fenômenos na qualidade da transmissão e dos dados obtidos. Os resultados experimentais demonstraram consistência com a teoria e com outros trabalhos publicados na área até esta data com relação às taxas de erro de bit quântico e também à taxa de transmissão de bits. As taxas de erro obtidas, por estarem abaixo do limiar teórico para segurança da informação em comunicação quântica, provam, ainda, a possibilidade de estabelecimento de chave secreta para criptografia através do uso de distribuição quântica das chaves (QKD). Os resultados também apresentaram boa qualidade da informação recuperada após a descriptografia. / [en] This work presents the study of optical quantum communication in the infrared region, using a hybrid optical-fiber – free-space system, as proof of principle for the agreement on secret keys by two parties for use in one-time pad encryption. By modulating the polarization of laser light into orthogonal polarizations, one can encode the classic bits 1 and 0 in each of these polarizations, being detected by single photon counter detectors, and can use the quantum channel to transmit the quantum bits between two interlocutors. It is then possible to use those bits to establish the cryptographic key, which can be used in any type of information to be transmitted by a classic or quantum channel. While carrying out transmission in free space optics, subject to climatic variations, such as atmospheric temperature, sunlight, presence of clouds and rain, and the presence of wind, the influence of these phenomena on the quality of transmission and on the data obtained was also studied. The experimental results showed consistency with the theory and with other works published to date with regard to quantum bit error rates and to the bit rate. The error rates obtained, being below the theoretical threshold for information security in quantum communication, further proves the possibility of establishing a secret key for encryption through the use of quantum key distribution (QKD). It also presented good quality on the information recovered after decryption.

In den letzten Jahrzehnten ist das globale Kommunikationssystem in einem immer größerem Maße ein integraler Bestandteil des täglichen Lebens geworden. Optische Kommunikationssysteme sind die technologische Basis für diese Entwicklung. Nur Fasern können die riesige benötigte Bandbreite bereitstellen. Während für die ersten optischen Übertragungssysteme die Faser als "flacher" Kanal betrachtet werden konnte, machen Wellenlängenmultiplex und steigende Übertragungsraten die Einbeziehung von immer mehr physikalischen Effekten notwendig. Bei einer Erhöhung der Kanaldatenrate auf 40 Gbit/s und mehr ist die statische Kompensation von chromatischer Dispersion nicht mehr ausreichend. Die intrinsische Toleranz der Modulationsformate gegenüber Dispersion nimmt quadratisch mit der Symbolrate ab. Daher können beispielsweise durch Umwelteinflüsse hervorgerufene Dispersionsschwankungen die Dispersionstoleranz der Modulationsformate überschreiten. Dies macht eine adaptive Dispersionskompensation notwendig, was gleichzeitig auch Dispersionsmonitoring erfordert, um den adaptiven Kompensator steuern zu können. Vorhandene Links können mit Restdispersionskompensatoren ausgestattet werden, um sie für Hochgeschwindigkeitsübertragungen zu ertüchtigen. Optische Kompensationstechniken sind unabhängig von der Kanaldatenrate. Daher wird eine Erhöhung der Datenrate problemlos unterstützt. Optische Kompensatoren können WDM-fähig gebaut werden, um mehrere Kanäle auf einmal zu entzerren. Das Buch beschäftigt sich mit optischen Delay-Line-Filtern als eine Klasse von optischen Kompensatoren. Die Filtersynthese von solchen Delay-Line-Filtern wird behandelt. Der Zusammenhang zwischen optischen Filtern und digitalen FIR-Filtern mit komplexen Koeffizienten im Zusammenhang mit kohärenter Detektion wird aufgezeigt. Iterative und analytische Methoden, die die Koeffizienten für dispersions- und dispersions-slope-kompensierende Filter produzieren, werden untersucht. Genauso wichtig wie die Kompensation von Dispersion ist die Schätzung der Dispersion eines Signals. Mit Delay-Line-Filtern können die Restseitenbänder eines Signals genutzt werden, um die Dispersion zu messen. Alternativ kann nichtlineare Detektion angewandt werden, um die Pulsverbreiterung, die hauptsächlich von der Dispersion herrührt, zu schätzen. Mit gemeinsamer Dispersionskompensation und Dispersionsmonitoring können Dispersionskompensatoren auf die Signalverzerrungen eingestellt werden. Spezielle Eigenschaften der Filter zusammen mit der analytischen Beschreibung können genutzt werden, um schnelle und zuverlässige Steueralgorithmen zur Filtereinstellung bereitzustellen. Schließlich wurden Prototypen derartiger faseroptischen Kompensatoren von chromatischer Dispersion und Dispersions-Slope hergestellt und charakterisiert. Die Einheiten und ihr Systemverhalten wird gezeigt und diskutiert. / Over the course of the past decades, the global communication system has become a central part of people's everyday lives. Optical communication systems are the technological basis for this development. Only fibers can provide the huge bandwidth that is required. Where the fiber could be regarded as a flat channel for the first optical transmission systems wavelength multiplexing and increasing line rates made it necessary to take more and more physical effects into account. When the line rates are increased to 40 Gbit/s and higher static chromatic dispersion compensation is not enough. The modulation format's intrinsic tolerance for dispersion decreases quadratically with the symbol rate. Thus, environmentally induced chromatic dispersion fluctuations may exceed the dispersion tolerance of the modulation formats. This makes an adaptive dispersion compensation necessary implying also the need for a monitoring scheme to steer the adaptive compensator. Legacy links that are CD-compensated by DCFs can be upgraded with residual dispersion compensators to make them ready for high speed transmission. Optical compensation is independent from the line rate. Hence, increasing the data rates is inherently supported. Optical compensators can be built WDM ready compensating multiple channels at once. The book deals with optical delay line filters as one class of optical compensators. The filter synthesis of such delay line filters is addressed. The connection between optical filters and digital FIR filters with complex coefficients that are used in conjunction with coherent detection could be shown. Iterative and analytical methods that produce the coefficients for dispersion (and also dispersion slope) compensating filters are researched. As important as the compensation of dispersion is the estimation of the dispersion of a signal. Using delay line filters, the vestigial sidebands of a signal can be used to measure the dispersion. Alternatively, nonlinear detection can be used to estimate the pulse broadening which is caused mainly by dispersion. With dispersion compensation and dispersion monitoring, dispersion compensators can be adapted to the signal's impairment. Special properties of the filter in conjunction with an analytical description can be used to provide a fast and reliable control algorithm for setting the filter to a given dispersion and centering it on a signal. Finally, prototypes of such fiber optic chromatic dispersion and dispersion slope compensation filters were manufactured and characterized. The device and system characterization of the prototypes is presented and discussed.