Digital signal processing optical receivers for the mitigation of physical layer impairments in dynamic optical networks

IT IS generally believed by the research community that the introduction of complex network functions—such as routing—in the optical domain will allow a better network utilisation, lower cost and footprint, and a more efficiency in energy usage. The new optical components and sub-systems intended for dynamic optical networking introduce new kinds of physical layer impairments in the optical signal, and it is of paramount importance to overcome this problem if dynamic optical networks should become a reality. Thus, the aim of this thesis was to first identify and characterise the physical layer impairments of dynamic optical networks, and then digital signal processing techniques were developed to mitigate them. The initial focus of this work was the design and characterisation of digital optical receivers for dynamic core optical networks. Digital receiver techniques allow for complex algorithms to be implemented in the digital domain, which usually outperform their analogue counterparts in performance and flexibility. An AC-coupled digital receiver for core networks—consisting of a standard PIN photodiode and a digitiser that takes samples at twice the Nyquist rate—was characterised in terms of both bit-error rate and packet-error rate, and it is shown that the packet-error rate can be optimised by appropriately setting the preamble length. Also, a realistic model of a digital receiver that includes the quantisation impairments was developed. Finally, the influence of the network load and the traffic sparsity on the packet-error rate performance of the receiver was investigated. Digital receiver technologies can be equally applied to optical access networks, which share many traits with dynamic core networks. A dual-rate digital receiver, capable of detecting optical packets at 10 and 1.25 Gb/s, was developed and characterised. The receiver dynamic range was extended by means of DC-coupling and non-linear signal clipping, and it is shown that the receiver performance is limited by digitiser noise for low received power and non-linear clipping for high received power

Birefringent and diffractive devices for implementing multi-Gbit/s transmission systems using visible WDM over SI-POF technology

Mención Internacional en el título de doctorNew optical devices are indispensable for the development of the future SI−POF high speed short−range communication networks and as well as in many sensors applications based on SI−POFs. These devices are not well established to date due to the physical and multimodal characteristics of the SI−POF technology as well as the characteristics of the SI−POF visible WDM systems. Therefore, the main objective that has been established for this research work is to develop new optical components based primarily on liquid crystals and diffractive elements for applications in advanced optical communication systems with plastic optical fibers, ensuring an optimized power consumption to reduce the carbon footprint of ICTs.Se necesitan nuevos dispositivos ópticos en el rango visible para el desarrollo de las futuras redes de comunicación de alta velocidad y corto alcance basadas en SI−POF. Estos dispositivos también son de gran utilidad en muchas aplicaciones de sensores basados en POF. Los diseños de estos dispositivos no están bien establecidos hasta la fecha debido a las características físicas y multimodales de la tecnología SI−POF, así como las características de los sistemas WDM en el visible. Por lo tanto, el principal objetivo que se ha establecido para este trabajo de investigación es el desarrollo de nuevos dispositivos ópticos basados principalmente en cristales líquidos y elementos de difracción para aplicaciones en sistemas avanzados de comunicaciones ópticas con fibras ópticas de plástico de salto de índice, lo que garantiza un consumo de energía optimizado para reducir la huella de carbono en esta tecnología en el sector TIC.Programa en Ingeniería Eléctrica, Electrónica y AutomáticaPresidente: Rajeev J. Ram.- Vocal: Bruno Fracasso.- Secretario: Javier Mateo Gascó

1995 BRAC Commission

Data Call - Naval Command, Control and Ocean Surveillance Center, Research Development Test Evaluation Division - San Diego, CA. Data Call #5. Box 186, L-118