Dynamically reconfigurable optical access network

This dissertation presents the research results on a fiber-optic high-bitrate access network which enables dynamic bandwidth allocation as a response to varying subscribers' demands and bandwidth needs of emerging services. The motivation of the research is given in Chapter 1 "Introduction" together with a brief comparative discussion on currently available and future access networks. The idea of wavelength reconfigurability in the last-mile networks is described as a solution for more efficient bandwidth utilization and a subject of the Broadband Photonics project. Chapter 2 "Wavelength-flexible WDM/TDM access network - architecture" provides a comprehensive description of the proposed solution with each network element being analyzed in terms of its functionalities. This includes a colorless optical network unit and a reconfigurable optical add/drop multiplexer. An estimation of power budget is followed by the choice of wavelength set and network control and management layer overview. In Chapter 3 "Reflective transceiver module for ONU" after discussing different communication schemes and modulation formats three approaches to a colorless high-bitrate transmitter are analyzed in detail. This includes experiment and simulation results on a reflective semiconductor optical amplifier, reflective electro-absorption modulator and a Michelson-interferometer modulator. The Chapter is concluded with a comparative discussion. Chapter 4 "Reconfigurable optical add/drop multiplexer" discusses another key element in the proposed network architecture which is an integrated structure of micro-ring resonators providing wavelength reconfigurability. The measured characteristics assess the applicability of the device able to support unicast and multicast transmission. A range of possible sources of signal degradation in the access links are analyzed in Chapter 5 "Transmission and network impairments in the access network". An estimation of potential power penalties resulting from such impairments in the proposed system follow afterwards. Special attention is paid to optical in-band crosstalk penalties and improvement methods in Chapter 6 "Interferometric crosstalk in the access network with an RSOA". This subject is treated extensively with the support of mathematical considerations and experimental results. Proof-of-concept experiments of the proposed network architecture are presented in Chapter 7 "Reconfigurable WDM/TDM access network - experiments". The results of bidirectional transmission of high-bitrate WDM signals in different wavelength allocation schemes are discussed in detail. From there, by means of simulations the behavior of a full-scale network is assessed. In Chapter 8 "Migration towards WDM/TDM access network" the migration scenario from currently deployed fiber-optic access networks towards the novel solution is proposed. Afterwards, a short dispute on the economics of last-mile fiber technologies is included. Finally, the work is concluded and potential future research ideas based on this thesis are given in Chapter 9 "Conclusions and further work"

Green radio communication networks applying radio-over-fibre technology for wireless access

Wireless communication increasingly is becoming the first choice link to enter into the global information society. It is an essential part of broadband communication networks, due to its capacity to cover the end-user domain, outdoors or indoors. The use of mobile phones and broadband has already exceeded the one of the fixed telephones and has caused tremendous changes in peoples life, as not only to be recognised in the current political overthrows. The all-around presence of wireless communication links combined with functions that support mobility will make a roaming person-bound communication network possible in the near future. This idea of a personal network, in which a user has his own communication environment available everywhere, necessitates immense numbers of radio access points to maintain the wireless links and support mobility. The progress towards “all-around wireless” needs budget and easily maintainable radio access points, with simplified signal processing and consolidation of the radio network functions in a central station. The RF energy consumption in mobile base stations is one of the main problems in the wireless communication system, which has led to the worldwide research in so called green communication, which offers an environmentally friendly and cost-effective solution. In order to extend networks and mobility support, the simplification of antenna stations and broadband communication capacity becomes an increasingly urgent demand, also the extension of the wireless signal transmission distance to consolidate the signal processing in a centralised site. Radio-over-Fibre technology (RoF) was considered and found to be the most promising solution to achieve effective delivery of wireless and baseband signals, also to reduce RF energy consumption. The overall aim of this research project was to simulate the transmission of wireless and baseband RF signals via fibre for a long distance in high quality, consuming a low-power budget. Therefore, this thesis demonstrated a green radio communication network and the advantage of transmitting signals via fibre rather than via air. The contributions of this research work were described in the follows: Firstly, a comparison of the power consumption in WiMAX via air and fibre is presented. As shown in the simulation results, the power budget for the transmission of 64 QAM WiMAX IEEE 802.16-2005 via air for a distance of 5km lies at -189.67 dB, whereas for the transmission via RoF for a distance of 140km, the power consumption ranges at 65dB. Through the deployment of a triple symmetrical compensator technique, consisting of SMF, DCF and FBG, the transmission distance of the 54 Mbps WiMAX signal can be increased to 410km without increasing the power budget of 65dB. An amendment of the triple compensator technique to SMF, DCF and CFBG allows a 120Mbps WiMAX signal transmission with a clear RF spectrum of 3.5 GHz and constellation diagram over a fibre length of 792km using a power budget of 192dB. Secondly, the thesis demonstrates a simulation setup for the deployment of more than one wireless system, namely 64 QAM WiMAX IEEE 802.16-2005 and LTE, for a data bit rate of 1Gbps via Wavelength Division Multiplexing (WDM) RoF over a transmission distance of 1800km. The RoF system includes two triple symmetrical compensator techniques - DCF, SMF, and CFBG - to obtain a large bandwidth, power budget of 393.6dB and a high signal quality for the long transmission distance. Finally, the thesis proposed a high data bit rate and energy efficient simulation architecture, applying a passive optical component for a transmission span up to 600km. A Gigabit Optical Passive Network (GPON) based on RoF downlink 2.5 Gbps and uplink 1.25Gbps is employed to carry LTE and WiMAX, also 18 digital channels by utilising Coarse Wavelength Division Multiplexing (CWDM). The setup achieved high data speed, a low-power budget of 151.2dB, and an increased service length of up to 600km

Técnicas alternativas para amplificação de Raman em telecomunicações

Doutoramento em FísicaO presente trabalho centra-se no estudo dos amplificadores de Raman em fibra ótica e suas aplicações em sistemas modernos de comunicações óticas. Abordaram-se tópicos específicos como a simulação espacial do amplificador de Raman, a equalização e alargamento do ganho, o uso de abordagens híbridas de amplificação através da associação de amplificadores de Raman em fibra ótica com amplificadores de fibra dopada com Érbio (EDFA) e os efeitos transitórios no ganho dos amplificadores. As actividades realizadas basearam-se em modelos teóricos, sendo os resultados validados experimentalmente. De entre as contribuições mais importantes desta tese, destaca-se (i) o desenvolvimento de um simulador eficiente para amplificadores de Raman que suporta arquitecturas de bombeamento contraprogantes e bidirecionais num contexto com multiplexagem no comprimento de onda (WDM); (ii) a implementação de um algoritmo de alocação de sinais de bombeamento usando a combinação do algoritmo genético com o método de Nelder- Mead; (iii) a apreciação de soluções de amplificação híbridas por associação dos amplificadores de Raman com EDFA em cenários de redes óticas passivas, nomeadamente WDM/TDM-PON com extensão a região espectral C+L; e (iv) a avaliação e caracterização de fenómenos transitórios em amplificadores para tráfego em rajadas/pacotes óticos e consequente desenvolvimento de soluções de mitigação baseadas em técnicas de clamping ótico.The present work is based on Raman Fiber Amplifiers and their applications in modern fiber communication systems. Specific topics were approached, namely the spatial simulation of Raman fiber amplifiers, the gain enlargement and equalization the use of hybrid amplification approaches by association of Raman amplifiers with Erbium doped fiber amplifiers (EDFA) and the transient effect on optical amplifiers gain. The work is based on theoretical models, being the obtained results validated experimentally. Among the main contributions, we remark: (i) the development of an efficient simulator for Raman fiber amplifiers that supports backward and bidirectional pumping architectures in a wavelength division multiplexing (WDM) context; (ii) the implementation of an algorithm to obtain enlargement and equalization of gain by allocation of pumps based on the association of the genetic algorithm with the Nelder-Mead method; (iii) the assessment of hybrid amplification solutions using Raman amplifiers and EDFA in the context of passive optical networks, namely WDM/TDM-PON with extension the C+L spectral bands; (iv) the assessment and characterization of transient effects on optical amplifiers with bursty/packeted traffic and the development of mitigation solutions based on optical clamping

Advances in local area optical data communication systems

This paper reviews optical fibre technology for local area optical communications systems. Technologies used in local systems include single and multimode fibre, single and multimode lasers, optical modulators, photodetectors, wavelength division multiplexing, multilevel modulation formats, electronic packet switching, electronic equalization and error correction. These methods have enabled the local area optical link data rate to increase from 0.1 Gb/s in 1990 to nearly a Tb/s in 2019. The challenges to increasing link data rates further, whilst reducing the transmitted power per bit, at reduced cost are discussed. Potential technical solutions and newly proposed methods which might address these challenges are highlighted

Applications of Ring Resonators and fiber delay lines for sensors and WDM Networks

En esta tesis doctoral, se presentan diversas aportaciones científicas en el ámbito de las aplicaciones de la fibra óptica y de las comunicaciones ópticas. En primer lugar, la tesis doctoral describe nuevas técnicas de medida remota y multiplexación en longitud de onda (WDM), a través de fibra óptica monomodo, para sensores ópticos. Las técnicas de medida están orientadas a sensores de intensidad óptica y se basan en configuraciones ópticas implementadas mediante redes de Bragg en fibra y líneas de retardo en fibra recirculantes (anillo resonante) y no recirculantes. En el documento se describen matemáticamente dichas técnicas y se presentan medidas experimentales que verifican los modelos teóricos. En segundo lugar, la tesis contiene diversas contribuciones novedosas al diseño y simulación por ordenador de filtros fotónicos compuestos basados en el anillo resonante con interferómetro Sagnac, para la compensación de la dispersión cromática en enlaces de transmisión digital con fibra óptica. Por último, el documento incluye un listado de todas las referencias empleadas, un listado de los acrónimos empleados, así como las publicaciones y patentes obtenidas por el autor hasta la fecha.Los proyectos de la Comisión Interministerial de Ciencia y Tecnología (CICYT): TIC2003-03783 (DISFOTON) y TEC2006-13273-C03-03-MIC (FOTOCOMIN). El programa de I+D+i de la Comunidad Autónoma de Madrid: FACTOTEM-CM (S-0505/ESP/000417). La Acción Integrada Hispano-Portuguesa del Plan Nacional de I+D+i 2004-2007: Self-referenced fibre optic intensity configurations for single and multi-sensors (HP2007-0093). El proyecto cofinanciado por la Universidad Carlos III de Madrid y la Comunidad Autónoma de Madrid: Fotónica en visualización, comunicaciones y sensores (CCG06-UC3M/TIC-0619). Las ayudas a la movilidad de investigadores en formación que me concedió la Universidad Carlos III de Madrid en 2006 y 2007. La Red Temática Europea SAMPA (HPRN-CT-2002-00202) del 5º Programa Marco de la Unión Europea. La Acción Europea FIDES (COST Action 299) del 6º Programa Marco de la Unión Europea. Y las Redes de Excelencia Europea ePhoton/ONe+ (FP6-IST-027497) y BONE (FP7-ICT-216863), del 6º y 7º Programa Marco de la Unión Europea, respectivamente

Semiconductor Optical Amplifiers and mm-Wave Wireless Links for Converged Access Networks

Future access networks are converged optical-wireless networks, where fixed-line and wireless services share the same infrastructure. In this book, semiconductor optical amplifiers (SOA) and mm-wave wireless links are investigated, and their use in converged access networks is explored: SOAs compensate losses in the network, and thereby extend the network reach. Millimeter-wave wireless links substitute fiber links when cabling is not economical

Extending OWns to include protection functionality

The objective of this dissertation is to enhance the functionality of an existing simulation package that is used to simulate fiber optic networks. These enhancements include the capability to simulate protection mechanisms following link failure, which is a necessity in real-world optical networks to ensure the continued flow of information following a failure in a part of the network. The capability for network traffic to choose from additional paths is also an addition to the software. The enhanced, as well as the original simulation software, are open source: this allows anyone to freely modify and improve the source code to suit his or her requirements. This dissertation will focus on mesh-based optical network topologies, which are commonly found in regional optical backbone networks, but which are also increasingly found in metropolitan areas. The regional networks all make use of wavelength division multiplexing (WDM), which consists of putting multiple different wavelengths of light on the same physical fiber. A single fiber breakage will therefore disrupt multiple fiber-optic connections. A fiber-optic network designer has to satisfy various conflicting requirements when designing a network: it must satisfy current and predicted future traffic requirements, it must be immune to equipment failure, but it must also be as inexpensive as possible. The network designer therefore has to evaluate different topologies and scenarios, and a good network simulator will provide invaluable assistance in finding an optimal solution. Protection and restoration need to be looked at in conjunction with routing and wavelength assignment (RWA), to ensure that resources in a network are used at maximum efficiency. Connection restoration time will also be looked at: this should be minimised to ensure minimal network downtime and ensuing loss of revenue. The chosen alternate connection path should also be as short as possible to minimise use of resources and maximise the carrying capacity of the network. Blocking probability (the inability to establish a connection due to a congested network) is a crucial factor and is also investigated. The topologies investigated in this dissertation consist of various mesh based real-world regional WDM fiber-optic networks. The impact of various link failures, the addition of additional alternate paths, as well as the effect of a protection mechanism on these topologies are also investigated. The proposed goals were all successfully achieved. The capability of simulating single as well as multiple link failures was introduced to the simulation package. The blocking probability of various network topologies was compared to each other in the presence of link failures. Success was also achieved in the introduction of a third alternate path to the simulation package.Dissertation (MEng(Electronic))--University of Pretoria, 2005.Electrical, Electronic and Computer Engineeringunrestricte

Reconfigurable nodes for passive optical networks (PON)

Mestrado em Engenharia Electrónica e TelecomunicaçõesRecentemente , as redes ópticas de nova geração têm sido motivo de acesa discussão nos meios científicos. Com o aumento verificado nos últimos anos do numero de utilizadores e o aparecimento de novos serviços disponibilizados através das redes de acesso, torna-se cada vez mais claro que a fibra óptica é a única solução para disponibilizar a largura de banda necessária. Neste trabalho é apresentado um novo método passivo capaz de aumentar os níveis de escalabilidade e reconfigurabilidade destas redes. O método consiste no controlo da quantidade de potência de bomba entregue a um amplificador ou conjunto de amplificadores remotos em série, permitindo o controlo independentemente do ganho fornecido por cada amplificador. Utilizando o método proposto consegue-se evitar o uso de componentes activos, ou mais complexos, para controlo da quantidade de potência de bomba a fornecer aos amplificadores remotos, tornando o processo de amplificação simultaneamente passivo e reconfigurável. Foi também desenvolvido, no âmbito deste trabalho, uma ferramenta de simulação baseada em algoritmos genéticos, capaz de simular e determinar a melhor solução para diversos cenários, optimizando os diversos parâmetros. Foi também realizada a caracterização de uma fibra óptica dopada com érbio, onde foi estudado o comportamento do ganho da fibra dopada quando bombeada por um sinal de bomba diferente dos comprimentos de onda nominais, 980nm e 1480nm. Ainda, o caso de bombeamentos com diferentes comprimentos de onda multiplexados foi motivo de estudo. ABSTRACT: Recently, the new generation optical networks are being the focus of several discussions in the scientific forums. With the observed increase of users in the last years, and the emergence of new services supplied through the access networks, it became even clearer that optical fiber is the best solution to provide the required bandwidth. In this work it is presented a new passive method capable to improve the scalability and reconfigurability of those networks. The method consist in controlling the amount of pump power to be supplied to one or various remotely pumped optical amplifiers disposed in series, and by this, adjust independently the gain of each. Using the proposed method, it is possible to dismiss the use of active or/and complex components, to control the remote amplifiers conditions, making all this amplification process passive and reconfigurable. It was also developed during this work, a simulation tool based in genetic algorithms, capable to simulate and reach the best solution for different network scenarios, optimizing the several parameters. A laboratory characterization of an erbium doped fiber amplifier it was also performed, where it was studied the gain behaviour of the doped fiber, when it is pumped by a signal which wavelength is different of the nominal wavelengths, 980nm and 1480nm. In this characterization it was also studied the gain behaviour when the amplifier is pumped with multiple multiplexed pump signals