All-optical router with PPM header processing in high speed photonic packet switching networks

Rapidly growing internet traffic volume is the major driving force behind the development of optically-transparent and ultra high-capacity photonic packet-switching networks. In such networks, the packet routing decision at each router is made by sequentially correlating an incoming packet header address with addresses in all entries of the router's look-up routing table. The routing task is achieved in the optical domain using all-optical logic gates and optical correlator technologies which have been predominantly replacing the existing low-speed electronic processing devices. Nevertheless when a network is expanded, a larger routing table is required thus exponentially increasing header processing time, which results in the increases in routing latency and complexity. This research aims to significantly reduce the size of the routing table and the number of optical devices required in a router by mapping both the packet header address and the look-up routing table entries into the pulse-position-modulation format, where more than one address could be located in a single entry of a new pulse-position routing table. By simply carrying out a single correlation of the packet header address with pulse- position routing table entries, the router can instantly obtain the routing decision, thus significantly reducing the processing time and neglecting the gain recovery time in existing optical logic gates. The structure of the pulse-position routing table also offers flexibility in the transmission mode including unicast, multicast or broadcast embedded in the optical (physical) layer. In the thesis, a new router based on the pulse-position¬modulation scheme will be introduced. Essential router modules including high on-off contrast-ratio clock extraction, pulse position routing table, header processing and optical switch are proposed and analysed. In addition, the thesis investigates and improves the switching window profile and residual crosstalk performance of the all- optical Mach-Zelmder switches as a building block for the implementation of the above router modules. A number of new variants of Mach-Zehnder-based switches are also introduced to enhance switching inter-output contrast ratio and reduce the complexity in multiple-channel OTDM demultiplexing

1 x M packet-switched router based on the PPM header address for all-optical WDM networks

This paper presents an all-optical 1xM router architecture for simultaneous multiple-wavelength packet routing, without the need for wavelength conversion. The packet header address is based on the pulse position modulation (PPM) format, which allows the use of only a single-bitwise optical AND gate for fast packet header address correlation. The proposed scheme offers both multicast and broadcast capabilities. We’ve demonstrated a high speed packet routing at 160 Gb/s in simulation, with a low channel crosstalk (CXT) of ~ -27 dB with a channel spacing of > 0.4 THz and a demultiplexer bandwidth of 500 GHz. The output transfer function of the PPM header processing (PPM-HP) module is also investigated in this paper

All Optical Packet Processing in Optical Network

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Photonic logic-gates: boosting all-optical header processing in future packet-switched networks

Las redes ópticas de paquetes se han convertido en los últimos años en uno de los temas de vanguardia en el campo de las tecnologías de comunicaciones. El procesado de cabeceras es una de las funciones más importantes que se llevan a cabo en nodos intermedios, donde un paquete debe ser encaminado a su destino correspondiente. El uso de tecnología completamente óptica para las funciones de encaminamiento y reconocimiento de cabeceras reduce el retardo de procesado respecto al procesado eléctrico, disminuyendo de ese modo la latencia en el enlace de comunicaciones. Existen diferentes métodos de procesado de datos para implementar el reconocimiento de cabeceras. El objetivo de este trabajo es la propuesta de una nueva arquitectura para el procesado de cabeceras basado en el uso de puertas lógicas completamente ópticas. Estas arquitecturas tienen como elemento clave el interferómetro Mach-Zehnder basado en el amplificador óptico de semiconductor (SOA-MZI), y utilizan el efecto no lineal de modulación cruzada de fase (XPM) en los SOAs para realizar dicha funcionalidad. La estructura SOA-MZI con XPM es una de las alternativas más atractivas debido a las numerosas ventajas que presenta, como por ejemplo los requisitos de baja energía para las señales de entrada, su diseño compacto, una elevada relación de extinción (ER), regeneración de la señal y el bajo nivel de chirp que introducen. Este trabajo se ha centrado en la implementación de la funcionalidad lógica XOR. Mediante esta función se pueden realizar diversas funcionalidades en las redes ópticas. Se proponen dos esquemas para el reconocimiento de cabeceras basados en el uso de la puerta XOR. El primer esquema utiliza puertas en cascada. El segundo esquema presenta una arquitectura muy escalable, y se basa en el uso de un bucle de realimentación implementado a la salida de la puerta. Asimismo, también se presentan algunas aplicaciones del procesado de cabeceras para el encaminamiento de paquetes basadas en el uso dMartínez Canet, JM. (2006). Photonic logic-gates: boosting all-optical header processing in future packet-switched networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1874Palanci

Optical performance monitoring in optical packet-switched networks

Para poder satisfacer la demanda de mayores anchos de banda y los requisitos de los nuevos servicios, se espera que se produzca una evolución de las redes ópticas hacia arquitecturas reconfigurables dinámicamente. Esta evolución subraya la importancia de ofrecer soluciones en la que la escalabilidad y la flexibilidad sean las principales directrices. De acuerdo a estas características, las redes ópticas de conmutación de paquetes (OPS) proporcionan altas capacidades de transmisión, eficiencia en ancho de banda y excelente flexibilidad, además de permitir el procesado de los paquetes directamente en la capa óptica. En este escenario, la solución all-optical label switching (AOLS) resuelve el cuello de botella impuesto por los nodos que realizan el procesado en el dominio eléctrico. A pesar de los progresos en el campo del networking óptico, las redes totalmente ópticas todavía se consideran una solución lejana . Por tanto, es importante desarrollar un escenario de migración factible y gradual desde las actuales redes ópticas basadas en la conmutación de circuitos (OCS). Uno de los objetivos de esta tesis se centra en la propuesta de escenarios de migración basados en redes híbridas que combinan diferentes tecnologías de conmutación. Además, se analiza la arquitectura de una red OPS compuesta de nodos que incorporan nuevas funcionalidades relacionadas con labores de monitorización y esquemas de recuperación. Las redes ópticas permiten mejorar la transparencia de la red, pero a costa de aumentar la complejidad de las tareas de gesión. En este escenario, la monitorización óptica de prestaciones (OPM) surge como una tecnología capaz de facilitar la administración de las redes OPS, en las que cada paquete sigue su propia ruta en la red y sufre un diferente nivel de degradación al llegar a su destino. Aquí reside la importancia de OPM para garantizar los requisitos de calidad de cada paquete.Vilar Mateo, R. (2010). Optical performance monitoring in optical packet-switched networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8926Palanci

Multi-Granular Optical Cross-Connect: Design, Analysis, and Demonstration

A fundamental issue in all-optical switching is to offer efficient and cost-effective transport services for a wide range of bandwidth granularities. This paper presents multi-granular optical cross-connect (MG-OXC) architectures that combine slow (ms regime) and fast (ns regime) switch elements, in order to support optical circuit switching (OCS), optical burst switching (OBS), and even optical packet switching (OPS). The MG-OXC architectures are designed to provide a cost-effective approach, while offering the flexibility and reconfigurability to deal with dynamic requirements of different applications. All proposed MG-OXC designs are analyzed and compared in terms of dimensionality, flexibility/reconfigurability, and scalability. Furthermore, node level simulations are conducted to evaluate the performance of MG-OXCs under different traffic regimes. Finally, the feasibility of the proposed architectures is demonstrated on an application-aware, multi-bit-rate (10 and 40 Gbps), end-to-end OBS testbed

Cross-Layer Platform for Dynamic, Energy-Efficient Optical Networks

The design of the next-generation Internet infrastructure is driven by the need to sustain the massive growth in bandwidth demands. Novel, energy-efficient, optical networking technologies and architectures are required to effectively meet the stringent performance requirements with low cost and ultrahigh energy efficiencies. In this thesis, a cross-layer communications platform is proposed to enable greater intelligence and functionality on the physical layer. Providing the optical layer with advanced networking capabilities will facilitate the dynamic management and optimization of optical switching based on performance monitoring measurements and higher-layer attributes. The cross-layer platform aims to create a new framework for networks to incorporate packet-scale measurement subsystems and techniques for monitoring the health of the optical channel. This will allow for quality-of-service- and energy-aware routing schemes, as well as an enhanced awareness of the optical data signals. This thesis first presents the design and development of an optical packet switching fabric. Leveraging a networking test-bed environment to validate networking hypotheses, advanced switching functionalities are demonstrated, including the support for quality-of-service based routing and packet multicasting. The investigated cross-layering is based on emerging optical technologies, enabling packet protection techniques and packet-rate switching fabric reconfiguration. Coupled with fast performance monitoring, the platform will achieve significant performance gains within the endeavor of all-optical switching. Allowing for a more intelligent, programmable optical layer aims to support greater flexibility with respect to bandwidth allocation and potentially a significant reduction in the network's energy consumption. The ultimate deliverable of this work is a high-performance, cross-layer enabled optical network node. The experimental demonstration of an initial prototype creates a dynamic network element with distributed control plane management, featuring fast packet-rate optical switching capabilities and embedded physical-layer performance monitoring modules. The cross-layer box enables an intelligent traffic delivery system that can dynamically manipulate optical switching on a packet-granular scale. With the goal of achieving advanced multi-layer routing and control algorithms, the network node requires an intelligent co-optimization across all the layers. The proposed cross-layer design should drive optical technologies and architectures in an innovative way, in order to fulfill the void between the design of basic photonic devices and the networking protocols that use them. The performance of the entire network -- from the optical components, to the routing algorithms and user applications -- should be optimized in concert. This contribution to the area of cross-layer network design creates an adaptable optical pipe that is extremely flexible and intelligent aware of both the physical optical signals and higher-layer requirements. The impact of this work will be seen in the realization of dynamic, energy-efficient optical communication links in future networking infrastructures

Characterisation and optimisation of the semiconductor optical amplifier for ultra-high speed performance

This research is in the area of high speed telecommunication systems where all- optical technologies are being introduced to meet the ever increasing demand for bandwidth by replacing the costly electro-optical conversion modules. In such systems, all-optical routers are the key technologies capable of supporting networks with high capacity/bandwidth as well as offering lower power consumption. One of the fundamental building blocks in all-optical routers/networks is the semiconductor optical amplifier (SOA), which is used in for clock extraction, wavelength conversion, all-optical gates and optical processing. The SOAs are perfect for optical amplification and optical switching at a very high speed. This is due to their small size, a low switching energy, non-linear characteristics and the seamless integration with other optical devices. Therefore, characterisation of the SOA operational functionalities and optimisation of its performance for amplification and switching are essential and challenging. Existing models on SOA gain dynamics do not address the impact of optical propagating wavelength, the combined input parameters and their adaptation for optimised amplification and switching operations. The SOA operation is limited at high data rates > 2.5 Gb/s to a greater extent by the gain recovery time. A number of schemes have been proposed to overcome this limitation; however no work has been reported on the SOA for improving the gain uniformity. This research aims to characterise the boundaries conditions and optimise the SOA performance for amplification and switching. The research also proposes alternative techniques to maximise the SOA gain uniformity at ultra-high speed data rates theoretically and practically. An SOA model is been developed and used throughout the research for theoretical simulations. Results show that the optimum conditions required to achieve the maximum output gain for best amplification performance depends on the SOA peak gain wavelength. It is also shown that the optimum phase shift of 180º for switching can be induced at lower input power level when the SOA biasing current is at its maximum limit. A gain standard deviation equation is introduced to measure the SOA gain uniformity. New wavelength diversity technique is proposed to achieve an average improvement of 7.82 dB in the SOA gain standard deviation at rates from 10 to 160 Gb/s. Other novel techniques that improved the gain uniformity employing triangular and sawtooth bias currents, as replacements for the uniform biasing, have been proposed. However, these current patterns were not able to improve the SOA gain uniformity at data rates beyond 40 Gb/s. For that reason, an optimised biasing for SOA (OBS) pattern is introduced to maximise the gain uniformity at any input data rates. This OBS pattern was practically generated and compared to the uniform biased SOA at different data rates and with different input bit sequences. All executed experiments showed better output uniformities employing the proposed OBS pattern with an average improvement of 19%