• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 73
  • 70
  • 25
  • 14
  • 9
  • 9
  • 6
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 237
  • 103
  • 52
  • 43
  • 39
  • 36
  • 35
  • 33
  • 29
  • 27
  • 27
  • 25
  • 24
  • 22
  • 21
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Modelagem de diodos laser de Fabry-Pérot travados por injeção de sinal óptico externo para uso em redes WDM-PON. / Modelling of diodes lasers Locked Fabry-Pérot óptical signal injection for use in external networks WDM-PON.

Duarte, Ulysses Rondina 14 April 2011 (has links)
A disponibilização de fontes ópticas multi-comprimento de onda de baixo custo certamente é um dos aspectos fundamentais para viabilizar a implantação de redes WDMPON (Wavelength Division Multiplexing-Passive Optical Network). Na literatura, são encontradas propostas de algumas tecnologias para a construção de tais dispositivos como a utilização de fontes ópticas sintonizáveis, uso de um vetor de lasers DFB (Distributed Feedback Laser) ou, até mesmo, o fatiamento espectral de uma fonte de banda larga. Contudo, essas propostas apresentam custo elevado, ou limitações de operação, tornando-se inapropriadas para a aplicação de interesse. Uma alternativa que vem sendo amplamente utilizada é o travamento óptico de diodos laser de Fabry-Pérot (FP-LD - Fabry-Pérot laser diode), realizado por meio da injeção de sinal óptico externo provindo do fatiamento espectral de uma fonte de banda larga. O travamento óptico possibilita o controle espectral do FP-LD, e o seu baixo custo torna essa fonte óptica atrativa na implantação de redes WDM. O entendimento do mecanismo de travamento torna-se, então, crucial na descrição da dinâmica de tais fontes ópticas. Desta forma, nesta dissertação, foi desenvolvido o estudo dos modelos matemáticos que descrevem a dinâmica de lasers travados, assim como foi investigado o desempenho de redes WDM-PON empregando estas fontes ópticas. / The availability of low cost multi-wavelength optical sources is certainly one of the fundamental aspects to allow the deployment of WDM-PON networks. Several technologies for the implementation of such optical sources are discussed in the literature, including tunable lasers, DFB arrays and spectral slicing of a broadband light source. However, those propositions suffer from high cost or operational limitations. One alternative is the optical injection locking of a Fabry Pérot laser diode (FPLD), in which the external optical injection signal is obtained from the spectral slicing of a broadband light source. This option has been widely investigated because the optical injection locking process allows for the FP-LD optical spectral control and wavelength selection. In addition, the low cost of such device makes this optical source an attractive solution for WDM-PON widespread deployment. In this context, the understanding of the locking mechanism becomes important in the optimization of such optical sources. Thus, in this dissertation, we conducted a study of mathematical models that describe the dynamics of locked lasers as well as investigated the performance of WDM-PON based on those optical sources.
92

All-Optical Multicast Routing under Optical Constraints / Routage multicast tout-optique sous contraintes optiques

Le, Dinh Danh 27 March 2015 (has links)
Au cours de la dernière décennie, le trafic dans les réseaux a connu une croissance explosive en double environ tous les trente trois mois. Les sources à l'origine de cette croissance proviennent de nombreuses applications à grande vitesse qui impliquent la transmission de données dans des groupes de multicast. Pour réaliser la multicast optique, les routeurs optiques peuvent avoir des répartiteurs de lumière spéciaux pour diviser des signaux lumineux et des convertisseurs de longueur d'onde pour modifier les longueurs d'onde où c'est nécessaire. Cependant, la division réduit l'énergie du signal qui nécessite alors une amplification ou une régénération qui nécessitent du matériel coûteux. Les convertisseurs de longueurs d'onde aussi ne sont pas suffisamment matures pour être largement déployés dans les technologies optiques actuelles. Par conséquent, dans les réseaux tout-optique, les unités de transformation des routeurs sont souvent hétérogènes et les algorithmes de routage doivent en tenir compte tout en parvenant à des solutions de compromis coût-performances qui satisfassent les exigences de bande passante et les contraintes optiques.Dans cette thèse, nous étudions les problème de routage multicast tout-optique (AOMR) dans les réseaux tout-optique hétérogènes. L'hétérogénéité provient principalement de l'absence / présence de séparateurs de lumière et de convertisseurs de longueur d'onde et de la répartition inégale des longueurs d'onde dans les liens du réseau. En général, les problèmes de AOMR sont NP-difficiles. L'objectif de la thèse est d'analyser et de formuler les problèmes sous différentes contraintes optiques, pour rechercher des solutions optimales ou proposer des heuristiques efficaces. Les deux contextes possibles, la demande unique ou multiple de multicast, sont examinés. Toutes les propositions présentées dans la thèse sont validées par des simulations approfondies. Les principales contributions peuvent être résumées comme il suit.1) Nous identifions les structures des routes optimales pour les problèmes de l'AOMR dans les réseaux WDM hétérogènes. Comme indiqué dans la thèse, les solutions optimales ne sont plus basées sur des arbres de lumière classiques, mais sur une structure arborescente plus générale appelée hiérarchie. Certaines formes de hiérarchie pour la multicast WDM sont des parcours optiques, des hiérarchies optiques, des hiérarchies-araignée optiques ou encore des ensembles de ces routes optiques. Les algorithmes exacts et les heuristiques proposés dans la thèse sont principalement basés sur les hiérarchies.2) Dans le cas du problème de multicast avec une seule demande dans des réseaux partiellement équipés de diviseurs de lumière, nous proposons une heuristique efficace dont les résultats font le compromis entre la consommation de longueur d'onde, le coût total, et le délai de bout-en-bout.3) Dans le même cas mais dans des réseaux non équipés de diviseurs de lumière, nous prouvons la NP-difficulté, exprimons les problèmes au moyen d'un programme linéaire (ILP) pour trouver les solutions exactes et proposons plusieurs heuristiques pour calculer de bonnes solutions.4) Pour le cas de demandes multicast multiples, nous nous concentrons sur les modèles de trafic statiques dans des réseaux partiellement équipés de diviseurs mais sans convertisseurs de longueur d'onde. Tout d'abord nous proposons une formulation ILP sur la base de hiérarchies optiques afin de rechercher la solution optimale. Ensuite, utilisant un modèle de graphe en couches, nous développons plusieurs heuristiques adaptatives pour calculer des hiérarchies optiques de solutions approximatives. Ces algorithmes adaptatifs surpassent les techniques de routage existants pour minimiser la probabilité de blocage.Dans l'ensemble, la thèse souligne que les solutions optimales pour les problèmes de l'AOMR considérés correspondent à des hiérarchies, que ce soit pour une seule demande ou des demandes multiples. / Over the past decade, network traffic levels experienced an explosive growth at about double amount in approximately every thirty months. The sources accounting for this growth come from numerous high-speed applications (e.g., video-on-demand, high-definition television) which involve the data transmission in multicast groups. To realize optical multicasting, optical routers should have light splitters to split light signals and wavelength converters to change the wavelengths wherever needed. However, the splitting reduces the energy of the output signal which in turn requires the costly power amplification or regeneration. Wavelength converters are also immature to be deployed widely in current optical technologies. Consequently, in all-optical networks, routers are often heterogeneous in their processing units, which challenges the routing. Therefore, it is crucial to design efficient multicast routing strategies at the backbone optical networks, in order to achieve cost-performance tradeoff solutions while satisfying the ever-increasing bandwidth demands and optical constraints.In this thesis, we investigate the all-optical multicast routing (AOMR) problems in heterogeneous optical networks. The heterogeneity mainly comes from the absence/presence of light splitters and wavelength converters and the uneven distribution of wavelengths in the network links. In general, AOMR problems are often NP-hard. The objective of the thesis is to analyze and formulate the problems, to search for the optimal solutions, and to propose efficient heuristics to solve the problems under different optical constraints. Both possible contexts, i.e., single-multicast request and multiple-multicast requests, are examined. All the reported results in the thesis are supported by extensive and careful simulations. The major contributions can be summarized as follows.1) We identify the optimal route structures for AOMR problems under heterogeneous mesh WDM networks. As shown in the thesis, the optimal solutions are no longer based on conventional light-trees, but a more general tree-like structure called hierarchy. Some forms of hierarchy realized for WDM multicasting are light-trails, light-hierarchies, light-spider hierarchies and a set of these light-structures. The exact and heuristic algorithms proposed in the thesis are mainly based on hierarchy. 2) For single-multicast with sparse-splitting case, we propose an efficient heuristic algorithm to produce a good tradeoff solution among wavelength consumption, channel total cost and end-to-end delay.3) For single-multicast with non-splitting case, we prove the NP-hardness, identify the optimal solution as a set of light-spider hierarchies, formulate the problems by means of Integer Linear Program (ILP) formulations to find the exact solution, and propose several cost-effective heuristic algorithms to compute the approximate solutions. 4) For the case with multiple-multicast requests, we focus on static traffic patterns under sparse-splitting without wavelength conversion case. First, an ILP formulation based on light-hierarchies is proposed to search for the optimal solution. By applying the layered graph model, we then develop several adaptive heuristic algorithms to compute light-hierarchies for approximate solutions. These adaptive algorithms outperform the existing fixed routing ones in minimizing the blocking probability. Overall, the thesis points out that the optimal solutions for heterogeneously constrained AOMR problems correspond to hierarchies, regardless of request multiplicity consideration.
93

Roteamento de tráfego e alocação de recursos em redes ópticas WDM com base em economia de energia / Energy-aware traffic routing and resource allocation in WDM optical networks

Llerena Valdivia, Nereida Celina 28 November 2014 (has links)
O crescimento do tráfego de serviços de telecomunicações tem aumentado o consumo de energia e, em consequência, aumentado as emissões de CO2 que tem efeitos nocivos sobre o meio ambiente. É assim que a economia de energia torna-se um fator chave no planejamento de redes de telecomunicações. Para garantir a disponibilidade e confiabilidade, as redes possuem arquitetura redundante e são projetadas para suportar a demanda de pico de tráfego. Redes com mecanismos de proteção como proteção dedicada de caminhos (DPP), proveem caminhos alternativos para cada demanda de conexão. Os elementos da rede que suportam esses caminhos estão em estado ativo (consumindo energia), apesar de, na maior parte do tempo, não transportarem tráfego efetivo. Um método para diminuir o gasto de energia é utilizar roteamento adaptado à carga real de tráfego baseado em modo suspenso (estado de baixo consumo de energia que pode passar a estado ativo rapidamente). Assim, o tráfego é roteado com vistas à maximizar a quantidade de componentes que são parte de caminhos de proteção, que podem ser postos em modo suspenso. Neste trabalho, as redes usadas para os testes são a rede europeia Cost239, a rede estadunidense UsNet e a rede brasileira Ipê. Abordamos o problema de economia de energia em redes WDM com DPP através de quatro estratégias de roteamento. Cada uma tem objetivos diferentes, a Shortest Path-DPP (SP-DPP) faz o roteamento por caminho mais curto, a Energy Aware-DPP (EA-DPP) aloca as demandas por enlaces que estejam ativos, a Energy Aware-DPP with Mixing (EA-DPP-MixS) evita que caminhos principais sejam roteados por enlaces que já são parte de caminhos de proteção e a Energy Aware-DPP with Differentation (EA-DPP-Dif) evita a mistura de caminhos por um mesmo enlace. Em nossas simulações computacionais observamos que a EA-DPP-Dif economiza energia de maneira eficiente, mas a probabilidade de bloqueio aumenta. A EA-DPP-MixS diminui o bloqueio em detrimento da energia economizada. Já a SP-DPP e a EA-DPP são menos eficientes na diminuição da energia consumida. É assim que propomos um roteamento com busca de recursos mais ampla, usando cada uma das estratégias. A proposta será chamada de roteamento intensivo. A EA-DPP-Dif-Intensivo diminui a probabilidade de bloqueio e economiza energia mediante modo suspenso. Neste trabalho, analisamos o desempenho das estratégias para cada uma das redes e avaliamos o impacto da energia economizada sobre a probabilidade de bloqueio. A proposta de roteamento i>intensivo diminui a energia consumida em até 50%, diminuindo a probabilidade de bloqueio. Porém, os resultados estão diretamente relacionados com a carga de rede e as características particulares da topologia de cada rede. / The growth of data traffic in telecommunication networks has increased energy consumption and hence increased CO2 emissions, with harmful effects on the environment. Thus, energy saving becomes a key and a differential factor when planning telecommunication networks. In order to guarantee availability and reliability, core networks have redundant architecture and are designed to support peak-hour traffic demand. Networks with dedicated path protection (DPP) mechanisms provide alternative paths for each connection request. Network elements supporting these paths are in active state (consuming energy), although most of the time they dont carry traffic. One technique to decrease energy waste is by adaptive real traffic routing using sleep mode (a low energy consumption state which is able to rapidly change to an active state). Thus, traffic is routed in order to maximize the amount of network components used by protection paths, which can be set in sleep mode. In this work, European Cost239, American UsNet and Brazilian Ipê networks were used in computational simulations. We addressed the energy saving problem in WDM networks with DPP through four routing strategies, each with different goals. The Shorthest Path-Dedicated Path Protection (SP-DPP) technique uses shortest path for routing, Energy Aware-Dedicated Path Protection (EA-DPP) allocates demands in active links, Energy Aware-Dedicated Path Protection with Mixing (EA-DPP-MixS) prevents primary paths to be formed by links that are already part of the protection paths and Energy Aware-Dedicated Path Protection with Differentation (EA-DPP-Dif) prevents mixing primary and protection paths through the same link. We observe that EA-DPP-Dif efficiently saved energy, however blocking probability has increased. EA-DPP-MixS reduced blocking rather than saved energy. At least, SP-DPP and EA-DPP are less efficient in reducing energy consumption. Hence, we propose a wider resource search routing, the in-depth routing, using each of these strategies. Thus, EA-DPP-Dif-In-depth decreased blocking probability while maintaining energy saving through sleep mode. In this work, we analyze the strategies performance for each network and evaluate the impact of energy saved on the blocking probability. Our in-depth routing strategy reduced the energy consumption up to 50%, decreasing blocking probability. However, the results are directly related with the network load and the specific properties of each network topology.
94

Topologias WDM-PON utilizando auto-alimentação com dupla cavidade óptica para Fronthaul analógico de redes 5G / Double-cavity self-seeding WDM-PON topologies as 5G networks analog Fronthaul

Souza, Adelcio Marques de 10 September 2018 (has links)
As futuras redes de acesso sem-fio, como a quinta geração de telefonia celular (5G), estão introduzindo e consolidando diversas tecnologias, tais como a operação em ondas milimétricas, picocélulas e o emprego massivo de antenas para diversidade espacial e temporal. Todas essas mudanças trazem desafios para a capacidade dos enlaces presentes nessas redes, como o backhaul e fronthaul. Nas últimas gerações, o ifronthaul tem utilizado Rádio-sobre-Fibra Digital (D-RoF, Digital Radio-over Fiber). Entretanto, neste novo paradigma, o processo de digitalização pode vir a consumir uma largura de banda excessiva e a transmissão analógica dos sinais de RF sobre a fibra se torna uma solução mais atrativa. Ao mesmo tempo, WDM-PON (Wavelength-Division-Multiplexing Passive-Optical-Network) é uma proeminente alternativa para o futuro das PONs, especialmente considerando o seu emprego como fronthaul. Para reduzir a necessidade de diversos transmissores diferentes, várias técnicas de auto-alimentação para obtenção de fontes ópticas agnósticas em comprimento de onda têm sido propostas. O presente trabalho faz um estudo de topologias de auto-alimentação com dupla cavidade para operarem como fronthaul analógico nas futuras redes de acesso sem-fio. Simulações numéricas utilizando o software Optisystem demonstram a viabilidade destas topologias em diversos cenários previstos para estas redes de acesso, especialmente considerando a operação em ondas milimétricas. Transmissões bem sucedidas foram obtidas para sinais ASK, M-PSK e M-QAM em frequências de microondas (1,25, 2,5 e 5 GHz) e ondas milimétricas (38 e 60 GHz) com vazões de 155 Mbps a 10 Gbps utilizando modulação direta e modulação externa. / Future radio access networks, such as the fifth generation mobile network (5G), are introducing and consolidating disruptive technologies, such as millimeter wave operation, dense picocell coverage and massive use of antennas for spatial and temporal diversity. These new technologies present a challenge for the capacity of the links that are present on these networks, including backhaul and fronthaul. In the latest cellular network generations, the fronthaul was typically implemented by Digital Radio-over-Fiber (D-RoF) technique. However, in this future context, the digitalization process would require a prohibitive bandwidth and the analog transmission of RF signals over the fiber can be a more attractive solution when compared to D-RoF. At the same time, Wavelength-Division-Multiplexing PON (WDM-PON) is prominent alternative for the future of PONs, especially considering its use as fronthaul. In order to avoid employing numerous distinct transmitters, several self-seeding techniques have been proposed to achieve colorless optical sources. This dissertation presents a numerical study of double-cavity self-seeding topologies to serve as analog fronthaul for future radio access networks. Numerical simulations using the software Optisystem demonstrate the feasibility of these topologies in various scenarios envisioned for these access networks, especially considering operation in millimeter waves. Successful transmission was achieved for ASK, M-PSK and M-QAM signals at microwave (1.25, 2.5 and 5 GHz) and millimeter wave (38 and 60 GHz) frequencies with throughput of 155 Mbps to 10 Gbps using direct and external modulation.
95

Architectures and protocols for sub-wavelength optical networks: contributions to connectionless and connection-oriented data transport

Triay Marquès, Joan 07 October 2011 (has links)
La ràpida evolució d’Internet i l’àmplia gamma de noves aplicacions (per exemple, multimèdia, videoconferència, jocs en línia, etc.) ha fomentat canvis revolucionaris en la manera com ens comuniquem. A més, algunes d’aquestes aplicacions demanden grans quantitats de recursos d’ample de banda amb diversos requeriments de qualitat de servei (QoS). El desenvolupament de la multiplexació per divisió de longitud d’ona (WDM) en els anys noranta va fer molt rendible la disponibilitat d’ample de banda. Avui dia, les tecnologies de commutació òptica de circuits són predominants en el nucli de la xarxa, les quals permeten la configuració de canals (lightpaths) a través de la xarxa. No obstant això, la granularitat d’aquests canals ocupa tota la longitud d’ona, el que fa que siguin ineficients per a proveir canals de menor ample de banda (sub-longitud d’ona). Segons la comunitat científica, és necessari augmentar la transparència dels protocols, així com millorar l’aprovisionament d’ample de banda de forma dinàmica. Per tal de fer això realitat, és necessari desenvolupar noves arquitectures. La commutació òptica de ràfegues i de paquets (OBS/OPS), són dues de les tecnologies proposades. Aquesta tesi contribueix amb tres arquitectures de xarxa destinades a millorar el transport de dades sub-longitud d’ona. En primer lloc, aprofundim en la naturalesa sense connexió en OBS. En aquest cas, la xarxa incrementa el seu dinamisme a causa de les transmissions a ràfega. A més, les col·lisions entre ràfegues degraden el rendiment de la xarxa fins i tot a càrregues molt baixes. Per fer front a aquestes col·lisions, es proposa un esquema de resolució de col·lisions pro actiu basat en un algorisme d’encaminament i assignació de longitud d’ona (RWA) que balanceja de forma automàtica i distribuïda la càrrega en la xarxa. En aquest protocol, el RWA i la transmissió de ràfegues es basen en l’explotació i exploració de regles de commutació que incorporen informació sobre contencions i encaminament. Per donar suport a aquesta arquitectura, s’utilitzen dos tipus de paquets de control per a l’encaminament de les ràfegues i l’actualització de les regles de commutació, respectivament. Per analitzar els beneficis del nou algorisme, s’utilitzen quatre topologies de xarxa diferents. Els resultats indiquen que el mètode proposat millora en diferents marges la resta d’algorismes RWA en funció de la topologia i sense penalitzar altres paràmetres com el retard extrem a extrem. La segona contribució proposa una arquitectura híbrida sense i orientada a connexió sobre la base d’un protocol de control d’accés al medi (MAC) per a xarxes OBS (DAOBS). El MAC ofereix dos mètodes d’accés: arbitratge de cua (QA) per a la transmissió de ràfegues sense connexió, i pre-arbitratge (PA) per serveis TDM orientats a connexió. Aquesta arquitectura permet una àmplia gamma d’aplicacions sensibles al retard i al bloqueig. Els resultats avaluats a través de simulacions mostren que en l’accés QA, les ràfegues de més alta prioritat tenen garantides zero pèrdues i latències d’accés molt baixes. Pel que fa a l’accés PA, es reporta que la duplicació de la càrrega TDM augmenta en més d’un ordre la probabilitat de bloqueig, però sense afectar en la mateixa mesura les ràfegues sense connexió. En aquest capítol també es tracten dos dels problemes relacionats amb l’arquitectura DAOBS i el seu funcionament. En primer lloc, es proposa un model matemàtic per aproximar el retard d’accés inferior i superior com a conseqüència de l’accés QA. En segon lloc, es formula matemàticament la generació i optimització de les topologies virtuals que suporten el protocol per a l’escenari amb tràfic estàtic. Finalment, l’última contribució explora els beneficis d’una arquitectura de xarxa òptica per temps compartit (TSON) basada en elements de càlcul de camins (PCE) centralitzats per tal d’evitar col·lisions en la xarxa. Aquesta arquitectura permet garantir l’aprovisionament orientat a connexió de canals sub-longitud d’ona. En aquest capítol proposem i simulem tres arquitectures GMPLS/PCE/TSON. A causa del enfocament centralitzat, el rendiment de la xarxa depèn en gran mesura de l’assignació i aprovisionament de les connexions. Amb aquesta finalitat, es proposen diferents algorismes d’assignació de ranures temporals i es comparen amb les corresponents formulacions de programació lineal (ILP) per al cas estàtic. Per al cas de tràfic dinàmic, proposem i avaluem mitjançant simulació diferents heurístiques. Els resultats mostren els beneficis de proporcionar flexibilitat en els dominis temporal i freqüencial a l’hora d’assignar les ranures temporals. / The rapid evolving Internet and the broad range of new data applications (e.g., multimedia, video-conference, online gaming, etc.) is fostering revolutionary changes in the way we communicate. In addition, some of these applications demand for unprecedented amounts of bandwidth resources with diverse quality of service (QoS). The development of wavelength division multiplexing (WDM) in the 90's made very cost-effective the availability of bandwidth. Nowadays, optical circuit switching technologies are predominant in the core enabling the set up of lightpaths across the network. However, full-wavelength lightpath granularity is too coarse, which results to be inefficient for provisioning sub-wavelength channels. As remarked by the research community, an open issue in optical networking is increasing the protocol transparency as well as provisioning true dynamic bandwidth allocation at the network level. To this end, new architectures are required. Optical burst/packet switching (OBS/OPS) are two such proposed technologies under investigation. This thesis contributes with three network architectures which aim at improving the sub-wavelength data transport from different perspectives. First, we gain insight into the connectionless nature of OBS. Here, the network dynamics are increased due to the short-lived burst transmissions. Moreover, burst contentions degrade the performance even at very low loads. To cope with them, we propose a proactive resolution scheme by means of a distributed auto load-balancing routing and wavelength assignment (RWA) algorithm for wavelength-continuity constraint networks. In this protocol, the RWA and burst forwarding is based on the exploitation and exploration of switching rule concentration values that incorporate contention and forwarding desirability information. To support such architecture, forward and backward control packets are used in the burst forwarding and updating rules, respectively. In order to analyze the benefits of the new algorithm, four different network topologies are used. Results indicate that the proposed method outperforms the rest of tested RWA algorithms at various margins depending on the topology without penalizing other parameters such as end-to-end delay. The second contribution proposes a hybrid connectionless and connection-oriented architecture based on a medium access control (MAC) protocol for OBS networks (DAOBS). The MAC provides two main access mechanisms: queue arbitrated (QA) for connectionless bursts and pre-arbitrated (PA) for TDM connection-oriented services. Such an architecture allows for a broad range of delay-sensitive applications or guaranteed services. Results evaluated through simulations show that in the QA access mode highest priority bursts are guaranteed zero losses and very low access latencies. Regarding the PA mode, we report that doubling the offered TDM traffic load increases in more than one order their connection blocking, slightly affecting the blocking of other connectionless bursts. In this chapter, we also tackle two of the issues related with the DAOBS architecture and its operation. Firstly, we model mathematically the lower and upper approximations of the access delay as a consequence of the connectionless queue arbitrated access. Secondly, we formulate the generation of the virtual light-tree overlay topology for the static traffic case.
96

Évaluation d’un module électro-optique hybride combinant la photonique sur silicium et sur verre pour des applications de multiplexage en longueur d’onde (WDM) / Assessment of an hybrid electro-optic module combining silicon and ions exchange glass photonics in order to address high speed Wavelength Division Multiplexing applications (WDM)

Ayi-Yovo, Folly Eli 05 April 2017 (has links)
La demande sans cesse croissante des besoins des télécommunications a mis en relief les limites intrinsèques de l’électronique. La photonique s’est révélée comme une solution appropriée à ses limitations. STMicroelectronics a développé une plateforme photonique sur silicium dénommée PIC25G permettant une transmission monocanale à 25 Gb/s. Cependant, l’augmentation du débit avec du multiplexage en longueur d’onde (WDM) se heurte à certaines contraintes. La solution suggérée repose sur une approche hybride intégrant la photonique sur silicium et sur verre par échange d’ions développée au laboratoire IMEP LaHC. La solution consiste en un interposeur verre sur lequel est assemblée une puce photonique sur silicium. Les études ont d’abord porté sur les composants de la puce silicium en particulier sur l’optimisation des coupleurs à réseau et les multiplexeurs à base d’interféromètres de Mach Zehnder cascadés. Ensuite, les composants passifs optiques et électriques de l’interposeur verre ont aussi été étudiés et réalisés. La faisabilité d’un couplage optique entre la puce silicium et l’interposeur a été démontrée. Enfin, les structures de tests nécessaires à la validation de la solution proposée ont été étudiées. Ces structures de tests ont permis de transmettre des signaux radiofréquences jusqu’à 40 GHz entre la puce silicium et l’interposeur verre. Une nouvelle approche de fabrication des guides d’onde optiques de l’interposeur a été suggérée et réalisée afin de répondre aux problèmes du procédé de fabrication. A terme, elle permettra d’avoir un module électro-optique pour des applications haut-débit. / The ever-increasing demand for telecommunications needs has highlighted the intrinsic limitations of electronics. Photonics has proven to be a suitable solution to its limitations. STMicroelectronics has developed a silicon photonic platform called PIC25G that allows single-channel transmission at 25 Gb/s. The data rate increase with wavelength division multiplexing (WDM) encounter some constraints. The proposed solution is based on a hybrid approach integrating silicon photonics and glass ions exchanged photonics developed at the IMEP-LaHC laboratory. The solution consists of a glass interposer on which a silicon photonics chip is assembled. First, the studies focused on the components of the silicon chip especially on the optimization of grating couplers and (de)-multiplexers based on cascaded Mach Zehnder interferometers. Then, the optical and electrical passive components of the glass interposer were studied and realized. The feasibility of an optical coupling between the silicon chip and the glass interposer has been demonstrated. Finally, the test structures needed to validate the proposed solution were studied. These test structures allowed to transmit radiofrequency signals up to 40 GHz between the silicon chip and the glass interposer. A new approach to realize the optical waveguides of the interposer has been suggested and carried out in order to address the fabrication issues. Ultimately, this approach will provide an electro-optical module for high-speed applications.
97

Study of converged 60 GHz radio over fiber with WDM-PON access networks / Optical heterodyne detection of 60 GHz UWB signals

Shao, Tong 25 June 2012 (has links)
Récemment, la convergence des techniques radio à 60 GHz sur fibre optique (radio over fiber - RoF) et des réseaux d’accès optiques passifs à multiplexage en longueurs d’ondes (wavelength division multiplexing-WDM) a suscité un très grand intérêt dans la communauté scientifique. L’objectif de cette thèse est d’étudier les solutions pour faire converger les systèmes RoF à 60 GHZ et les réseaux passifs optiques (passive optical network – PON) utilisant le WDM, appelés dans la suite PON-WDM. Les résultats principaux de cette thèse axée sur la technologie des systèmes RoF et l’intégration des systèmes RoF avec les réseaux d’accès PON-WDM sont les suivants : Un système RoF utilisant un démultiplexeur WDM, compatible avec les réseaux d’accès PON-WDM, est proposé dans cette thèse. Nous avons mené une étude théorique complète du bruit de phase. Elle inclut la contribution des bruits de phase des générateurs de signaux électriques et celle de la conversion de bruit de phase optique en bruit d’intensité. Cette dernière conversion est due à la détection de deux signaux cohérents, retardés l’un par rapport à l’autre si les longueurs optiques entre les deux canaux optiques se recombinant sont différentes. La densité spectrale de puissance du signal millimétrique généré optiquement est analysée théoriquement et démontrée expérimentalement. Son étude donne une méthode pour compenser un éventuel délai optique │τd│. L’amplitude du vecteur d’erreur (error vector magnitude –EVM) est théoriquement calculée et expérimentalement démontrée, en fonction du rapport │τd│/τcOP où τcOP est la durée de cohérence de la source optique utilisée. Cela donne une règle de conception pour insérer le démultiplexeur optique dans le système d’hétérodynage optique.  Nous avons validé expérimentalement la technique d’hétérodynage optique qui utilise un démultiplexeur pour générer un signal millimétrique respectant le standard ECMA 387. Nous avons proposé un système combinant une partie RoF et un réseau PON-WDM, permettant la génération simultanée d’un signal millimétrique respectant le standard ECMA 387 et la transmission d’un signal en bande de base à plusieurs gigabits par seconde. Nous avons réalisé expérimentalement avec succès la transmission simultanée d’un signal à 60 GHZ, modulé avec une modulation BPSK par un signal à 1588 Mbit/s et celle d’un signal en bande de base à 10 Gbit/s.  Nous avons proposé une nouvelle technique de modulation multi-bandes : la modulation de phase parallèle utilisant un unique modulateur de Mach-Zehnder. Cette technique présente des avantages significatifs comparée à n’importe quelle autre technique de modulation multi-bandes. Il n’y a aucun impact de la modulation en bande de base sur la génération millimétrique. L’impact de la modulation RF sur la transmission en bande de base (impact dû à la non-linéarité de la modulation de phase) est limité. Le taux d’erreurs binaires du signal en bande de base intégrant l’effet du signal RF a été théoriquement calculé et expérimentalement validé. Cela donne des règles de conception pour la technique de modulation de phase parallèle avec un unique modulateur de Mach-Zehnder. Nous avons proposé une architecture et réalisé un démonstrateur d’un système bas-coût bidirectionnel pour la transmission RoF. Ce système utilise le mélange optoélectronique et la technique d’hétérodynage optique. Nous avons prouvé que :  Des signaux à 60 GHz modulés à 397 Mbit/s et 794 Mbit/s avec une modulation BPSK sont convertis vers la bande basse de fréquence en utilisant la technique de mélange optoélectronique : les contraintes du standard ECMA 387 sont respectées.  Pour la liaison descendante utilisant la technique d’hétérodynage optique, aucune pénalité sur l’EVM n’est causée par le choix du régime non linéaire de la photodiode. / Recently, convergence of 60 GHz radio over fiber (RoF) technique with wavelength division multiplexing (WDM) passive optical networks (PON) has raised great interests because it provides the possibility for simultaneous broadband 60 GHz signal generation and multi-gigabit per second wireline transmission. The objective of the thesis is to study the solutions for converged 60 GHz RoF and WDM-PON technique. In this thesis, we have made the following achievements for RoF technology and the integration of RoF technology with WDM-PON access networks: A RoF system using WDM DEMUX which is supposed to be compliant with WDM-PON access networks is proposed in this thesis. Phase noise including optical phase to intensity noise conversion contribution due to the delayed coherent detection induced by the different optical lengths between the two optical channels and the phase noise contribution due to the electrical generators has been theoretically studied. PSD of the optical mmW is theoretically analyzed and experimentally demonstrated, which gives a solution to compensate different optical delay │τd│ EVM as function of │τd│/τcOP is theoretically derived and experimentally proved, which gives a design rule for optical heterodyning using WDM DEMUX The optical heterodyning technique using WDM DEMUX for mmW generation respecting ECMA 387 standard is validated by the experiment. We proposed a simple combination of RoF with WDM-PON supporting mmW generation respecting ECMA 387 standard and multi-gigabit per second baseband transmission. Simultaneous transmission of 1588 Mbps BPSK 60 GHz signal and 10 Gbps baseband signal is experimentally proved. A novel WDM-RoF-PON access networks with multi-band modulation technique is proposed in order to lower the cost of infrastructure. We propose a novel parallel phase modulation technique with a single MZM. This technique can offer several significant advantages compared to any other multi-band modulation technique. No impact from baseband modulation to mmW generation. Limited impact from RF modulation to baseband transmission due to the non-linearity of the phase modulation. BER of baseband signal with RF impact is theoretically studied and experimentally demonstrated, which gives a design rule for parallel phase modulation technique with a single MZM A low-cost bidirectional RoF transmission using optoelectronic mixing and optical heterodyning technique is proposed and experimentally demonstrated. It has been proved that: 397 Mbps and 794 Mbps BPSK 60 GHz uplink signal is down-converted to IF band respecting the ECMA 387 standard by using the optoelectronic mixing technique. No EVM penalty is paid to the non-linearity biased PD for downlink transmission by optical heterodyning technique. 6 dB power penalty need to be paid for the non-linear biased PD, which can be compensated by using high gain LNA after the PD.
98

[en] CYCLIC RANDOM VARIABLES AND THEIR APPLICATION IN THE STUDY OF INTERFEROMETRIC NOISE / [es] VARIABLES ALEATORIAS CÍCLICAS Y SU APLICACIÓN EN EL ESTUDIO DEL RUIDO INTERFEROMÉTRICO / [pt] VARIÁVEIS ALEATÓRIAS CÍCLICAS E SUA APLICAÇÃO NO ESTUDO DO RUÍDO INTERFEROMÉTRICO

MARCELO ROBERTO BAPTISTA PEREIRA LUIS JIMENEZ 28 September 2001 (has links)
[pt] O ruído interferométrico é um fator limitante cada vez mais importante nos sistemas óticos, principalmente nas ligações de longa distância em redes óticas transparentes. O presente trabalho analisa modelos para este tipo de ruído, dando um tratamento matemático novo para o modelo não-gaussiano. A teoria matemática é desenvolvida em detalhes e comrigor. O modelo gaussiano foi usado a fim de fazer previsões quanto aos valores de chão da taxa de erro de bits. Os dois modelos foram simulados em computador e comparados com os testes realizados em laboratório e os resultados são apresentados. / [en] The interferometric noise is becoming a serious limiting factor in optical systems,notably on long distance connections in transparent optical networks. The present work analyzes models for this kind of noise, giving a new mathematical treatment to the non-gaussian model. The mathematical theory is developed in detail and rigorously. The gaussian model was used in order to make predictions relative to bit error rate floors. Both models were simulated in computer and compared with the tests made in laboratory and the results are presented. / [es] EL ruido interferométrico es un factor limitante cada vez más importante en los sistemas ópticos, principalmente en las llamadas a larga distancia en redes ópticas transparentes. EL presente trabajo analiza modelos para este tipo de ruido, dando un nuevo tratamiento matemático para el modelo no gausiano. La teoría matemática es desarrollada en detalles y con rigor. EL modelo gausiano fue usado para efectuar previsiones de las cotas inferiores de la tasa de error de bits. Los dos modelos fueron simulados en computador y comparados con las priuebas de laboratorio y se presentan los resultados.
99

Algoritmos para alocação de rota e comprimento de onda com restrições de energia e da camada física em redes ópticas

Nogueira, Pedro Henrique Tolentino de Melo 15 August 2014 (has links)
Made available in DSpace on 2015-05-14T12:36:49Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2456764 bytes, checksum: 4ac348983da5718e79b705aa01b9aa0a (MD5) Previous issue date: 2014-08-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This dissertation proposes two new algorithms for routing and wavelength allocation EA-RWA (Energy Aware Routing and Wavelength Assigment) and IEA-RWA (Impairment and Energy Aware Routing and Wavelength Assigment). The algorithms have the characteristic, improve energy efficiency in dynamic transparent optical networks, the first being simpler, because it does not care about the imperfections of the physical layer. The EA-RWA is compared with a traditional RWA / classic that does not take into account at the time of admission of the physical layer connections restrictions nor energy consumption algorithm. Have the IEA-RWA is compared with a RWA algorithm that takes into account the constraints (IA-RWA) physical layer. Numerical simulations show that the IEA-RWA performs better in many aspects / Esta dissertação propõe dois novos algoritmos de roteamento e alocação de comprimento de onda, a saber, o EA-RWA (Energy Aware Routing and Wavelength Assigment) e o IEA-RWA (Impairment and Energy Aware Routing and Wavelength Assigment). Os algoritmos terão como característica, melhorar a eficiência energética em redes ópticas transparentes dinâmicas, sendo o primeiro mais simples, pois não se preocupa com as imperfeições da camada física. O EA-RWA é comparado com um algoritmo RWA tradicional/clássico que não leva em conta, no momento de admissão de conexões, restrições da camada física e nem consumo de energia. Já o IEA-RWA é comparado com um algoritmo RWA que leva em conta restrições da camada física (IA-RWA). As simulações numéricas mostram que o IEA-RWA apresenta melhor desempenho em vários aspectos
100

Topologias WDM-PON utilizando auto-alimentação com dupla cavidade óptica para Fronthaul analógico de redes 5G / Double-cavity self-seeding WDM-PON topologies as 5G networks analog Fronthaul

Adelcio Marques de Souza 10 September 2018 (has links)
As futuras redes de acesso sem-fio, como a quinta geração de telefonia celular (5G), estão introduzindo e consolidando diversas tecnologias, tais como a operação em ondas milimétricas, picocélulas e o emprego massivo de antenas para diversidade espacial e temporal. Todas essas mudanças trazem desafios para a capacidade dos enlaces presentes nessas redes, como o backhaul e fronthaul. Nas últimas gerações, o ifronthaul tem utilizado Rádio-sobre-Fibra Digital (D-RoF, Digital Radio-over Fiber). Entretanto, neste novo paradigma, o processo de digitalização pode vir a consumir uma largura de banda excessiva e a transmissão analógica dos sinais de RF sobre a fibra se torna uma solução mais atrativa. Ao mesmo tempo, WDM-PON (Wavelength-Division-Multiplexing Passive-Optical-Network) é uma proeminente alternativa para o futuro das PONs, especialmente considerando o seu emprego como fronthaul. Para reduzir a necessidade de diversos transmissores diferentes, várias técnicas de auto-alimentação para obtenção de fontes ópticas agnósticas em comprimento de onda têm sido propostas. O presente trabalho faz um estudo de topologias de auto-alimentação com dupla cavidade para operarem como fronthaul analógico nas futuras redes de acesso sem-fio. Simulações numéricas utilizando o software Optisystem demonstram a viabilidade destas topologias em diversos cenários previstos para estas redes de acesso, especialmente considerando a operação em ondas milimétricas. Transmissões bem sucedidas foram obtidas para sinais ASK, M-PSK e M-QAM em frequências de microondas (1,25, 2,5 e 5 GHz) e ondas milimétricas (38 e 60 GHz) com vazões de 155 Mbps a 10 Gbps utilizando modulação direta e modulação externa. / Future radio access networks, such as the fifth generation mobile network (5G), are introducing and consolidating disruptive technologies, such as millimeter wave operation, dense picocell coverage and massive use of antennas for spatial and temporal diversity. These new technologies present a challenge for the capacity of the links that are present on these networks, including backhaul and fronthaul. In the latest cellular network generations, the fronthaul was typically implemented by Digital Radio-over-Fiber (D-RoF) technique. However, in this future context, the digitalization process would require a prohibitive bandwidth and the analog transmission of RF signals over the fiber can be a more attractive solution when compared to D-RoF. At the same time, Wavelength-Division-Multiplexing PON (WDM-PON) is prominent alternative for the future of PONs, especially considering its use as fronthaul. In order to avoid employing numerous distinct transmitters, several self-seeding techniques have been proposed to achieve colorless optical sources. This dissertation presents a numerical study of double-cavity self-seeding topologies to serve as analog fronthaul for future radio access networks. Numerical simulations using the software Optisystem demonstrate the feasibility of these topologies in various scenarios envisioned for these access networks, especially considering operation in millimeter waves. Successful transmission was achieved for ASK, M-PSK and M-QAM signals at microwave (1.25, 2.5 and 5 GHz) and millimeter wave (38 and 60 GHz) frequencies with throughput of 155 Mbps to 10 Gbps using direct and external modulation.

Page generated in 0.0512 seconds