Protection in space division multiplexing elastic optical networks

Orientador: Nelson Luis Saldanha da FonsecaTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: A multiplexação por divisão espacial é uma solução promissora para que as redes ópticas elásticas possam lidar com o esgotamento esperado da capacidade das redes de único núcleo. A introdução da multiplexação por divisão espacial em redes ópticas traz novos desafios para proteção de redes, uma vez que um caminho de luz pode abranger uma alta capacidade e transmitir dados a diferentes taxas. Adicionalmente, a enorme quantidade de tráfego nestas redes provocam a necessidade de proteção contra falhas, uma vez que essas são relativamente frequentes; atualmente, a taxa de falha de um corte de fibra é uma a cada quatro dias. Muitos estudos sobre redes ópticas têm sido desenvolvidos e relatados na literatura. No entanto, apenas recentemente, o estudo de multiplexação espacial para redes ópticas elásticas tem sido considerado. Nesse contexto, embora algoritmos de roteamento e alocação de núcleo e espectro tenham sido propostos na literatura, poucos trabalhos consideram proteção. Além disso, o compartilhamento de recursos de backup não é considerado. Nesta tese, propõe-se soluções de proteção em redes ópticas elásticas com multiplexação espacial, visando a redução do bloqueio de requisições para estabelecimento de conexão, o melhoramento da utilização dos recursos em redes ópticas elásticas com multiplexação espacial, considerando diferentes cenários de carga e topologias. Para tal, o problema de proteção destas redes levará em consideração a utilização de caminhos de proteção, diferentes formatos de modulação, o uso de agregação de tráfego, o uso de sobreposição de espectro em caminhos de proteção, interferência mínima e roteamento multicaminho. Diversos algoritmos foram propostos e avaliados para prover 100% de proteção contra ocorrência de uma falha, bem como um algoritmo para proteção contra duas falhas simultâneas. Os resultados indicam que os algoritmos propostos produzem um melhor desempenho quando comparado ao desempenho dos algoritmos existentes na literaturaAbstract: Spatial division multiplexing is a promising solution proposed for elastic optical networks to cope with the expected depletion of the capacity of single core networks. The introduction of space division multiplexing in optical networks brings new challenges for network protection since a lightpath can span high capacity and transmit data at different rates. In addition, there is the great need for protection mechanisms against failure due to the high volume of traffic carried in these networks. Failure is quite frequent in operational optical networks, it is estimated that there is a failure every four hours. Several studies on optical networks have been carried out but, only recently, the study of spatial division multiplexing for elastic optical networks has been considered. In this context, although routing, spectrum, and core allocation algorithms have been proposed in the literature, only a few papers consider protection. In addition, sharing of backup resources is not considered. In this thesis, it is proposed to provide protection solutions in spatial division multiplexing elastic optical networks, for reducing the blocking of requests for connection establishment, as well as improving the use of resources, considering different load scenarios and topologies. For this, the protection problem of these networks will take into consideration the use of protection paths, different modulation formats, the use of traffic grooming, the use of spectrum overlap in protection paths, minimum interference and multipath routing. Several algorithms are proposed in this thesis to provide 100% protection against a single failure and one algorithm for two simultaneous failure. results indicate that these algorithms overperform existing onesDoutoradoCiência da ComputaçãoDoutor em Ciência da Computação165446/2015-3CNPQCAPE

Data transport over optical fibre for ska using advanced modulation flexible spectrum technology

Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA.We optimise the flexible spectrum for real-time dynamic channel wavelength assignment, to ensure optimum network performance. We needed to identify and develop novel hardware and dynamic algorithms for these networks to function optimally to perform critical tasks. Such tasks include wavelength assignment, signal routing, network restoration and network protection. The antennas of the Square Kilometre Array (SKA) network connect to the correlator and data processor in a simple point-to-point fixed configuration. The connection of the astronomer users to the data processor, however, requires a more complex network architecture. This is because the network has users scattered around South Africa, Africa and the whole world. This calls for upgrade of the classical fixed wavelength spectrum grids, to flexible spectrum grid that has improved capacity, reliable, simple and cost-effectiveness through sharing of network infrastructure. The exponential growth of data traffic in current optical communication networks requires higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilisation and resolve wavelength contention associated with the flexible spectrum. Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA. Each DWDM channel is capable of 10 Gbps transmission rate, which is sliceable into finer flexible grid 12.5 GHz granularity to offer the network elastic spectrum and channel spacing capable of signal routing and wavelength switching for the scalability of aggregate bandwidth. The variable-sized portions of the flexible spectrum assignment to end users at different speeds depend on bandwidth demand, allowing efficient utilisation of the spectrum resources. The entire bandwidth of dynamic optical connections must be contiguously allocated. However, there is an introduction of spectrum fragmentation due to spectrum contiguity related to the optical channels having different width. Thus large traffic demands are likely to experience blocking regardless of available bandwidth. To minimise the congestion and cost-effectively obtain high performance, the optical network must be reconfigurable, achievable by adding wavelength as an extra degree of freedom for effectiveness. This can introduce colourless, directionless and contentionless reconfigurability to route individual wavelengths from fibre to fibre across multiple nodes to avoid wavelength blocking/collisions, increasing the flexibility and capacity of a network. For these networks to function optimally, novel hardware and dynamic algorithms identification and development is a critical task. Such tasks include wavelength assignment, signal routing, network restoration and network protection. In this work, we for the first time to our knowledge proposed a spectrum defragmentation technique through reallocation of the central frequency of the optical transmitter, to increase the probability of finding a sufficient continuous spectrum. This is to improve network resource utilisation, capacity and resolve wavelength contention associated with a flexible spectrum in optical communication networks. The following chapter provides details on a flexible spectrum in optical fibre networks utilising DWDM, optimising transmitter-receivers, advanced modulation formats, coherent detection, reconfigurable optical add and drop multiplexer (ROADM) technology to implement hardware and middleware platforms which address growing bandwidth demands for scalability, flexibility and cost-efficiency. A major attribute is tunable lasers, an essential component for future flexible spectrum with application to wavelength switching, routing, wavelength conversion and ROADM for the multi-node optical network through spectrum flexibility and cost-effective sharing of fibre links, transmitters and receivers. Spectrum slicing into fine granular sub-carriers and assigning several frequency slots to accommodate diverse traffic demands is a viable approach. This work experimentally presents a spectral efficient technique for bandwidth variability, wavelength allocation, routing, defragmentation and wavelength selective switches in the nodes of a network, capable of removing the fixed grid spacing using low cost, high bandwidth, power-efficient and wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) transmitter directly modulated with 10 Gbps data. This to ensure that majority of the spectrum utilisation at finer channel spacing, wastage of the spectrum resource as caused by the wavelength continuity constraint reduction and it improves bandwidth utilisation. The technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency

Data transport over optical fibre for ska using advanced modulation flexible spectrum technology

Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA.We optimise the flexible spectrum for real-time dynamic channel wavelength assignment, to ensure optimum network performance. We needed to identify and develop novel hardware and dynamic algorithms for these networks to function optimally to perform critical tasks. Such tasks include wavelength assignment, signal routing, network restoration and network protection. The antennas of the Square Kilometre Array (SKA) network connect to the correlator and data processor in a simple point-to-point fixed configuration. The connection of the astronomer users to the data processor, however, requires a more complex network architecture. This is because the network has users scattered around South Africa, Africa and the whole world. This calls for upgrade of the classical fixed wavelength spectrum grids, to flexible spectrum grid that has improved capacity, reliable, simple and cost-effectiveness through sharing of network infrastructure. The exponential growth of data traffic in current optical communication networks requires higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilisation and resolve wavelength contention associated with the flexible spectrum. Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA. Each DWDM channel is capable of 10 Gbps transmission rate, which is sliceable into finer flexible grid 12.5 GHz granularity to offer the network elastic spectrum and channel spacing capable of signal routing and wavelength switching for the scalability of aggregate bandwidth. The variable-sized portions of the flexible spectrum assignment to end users at different speeds depend on bandwidth demand, allowing efficient utilisation of the spectrum resources. The entire bandwidth of dynamic optical connections must be contiguously allocated. However, there is an introduction of spectrum fragmentation due to spectrum contiguity related to the optical channels having different width. Thus large traffic demands are likely to experience blocking regardless of available bandwidth. To minimise the congestion and cost-effectively obtain high performance, the optical network must be reconfigurable, achievable by adding wavelength as an extra degree of freedom for effectiveness. This can introduce colourless, directionless and contentionless reconfigurability to route individual wavelengths from fibre to fibre across multiple nodes to avoid wavelength blocking/collisions, increasing the flexibility and capacity of a network. For these networks to function optimally, novel hardware and dynamic algorithms identification and development is a critical task. Such tasks include wavelength assignment, signal routing, network restoration and network protection. In this work, we for the first time to our knowledge proposed a spectrum defragmentation technique through reallocation of the central frequency of the optical transmitter, to increase the probability of finding a sufficient continuous spectrum. This is to improve network resource utilisation, capacity and resolve wavelength contention associated with a flexible spectrum in optical communication networks. The following chapter provides details on a flexible spectrum in optical fibre networks utilising DWDM, optimising transmitter-receivers, advanced modulation formats, coherent detection, reconfigurable optical add and drop multiplexer (ROADM) technology to implement hardware and middleware platforms which address growing bandwidth demands for scalability, flexibility and cost-efficiency. A major attribute is tunable lasers, an essential component for future flexible spectrum with application to wavelength switching, routing, wavelength conversion and ROADM for the multi-node optical network through spectrum flexibility and cost-effective sharing of fibre links, transmitters and receivers. Spectrum slicing into fine granular sub-carriers and assigning several frequency slots to accommodate diverse traffic demands is a viable approach. This work experimentally presents a spectral efficient technique for bandwidth variability, wavelength allocation, routing, defragmentation and wavelength selective switches in the nodes of a network, capable of removing the fixed grid spacing using low cost, high bandwidth, power-efficient and wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) transmitter directly modulated with 10 Gbps data. This to ensure that majority of the spectrum utilisation at finer channel spacing, wastage of the spectrum resource as caused by the wavelength continuity constraint reduction and it improves bandwidth utilisation. The technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency