Performance Analysis of Subwavelength Switching Optical Networks

A key challenge in today’s networks is to bridge the gap between high-speed optical transmission and limited electronic processing. This can be achieved by enabling payload to be switched directly in the optical domain. A simple solution to provide optical switching is by allocating one wavelength channel to each source-destination pair, a technique called Optical Circuit Switching (OCS). Due to lack of sharing, OCS suffers from limited scalability. To overcome this issue, the capacity of each wavelength channel must be dynamically shared among different source-destination pairs. This requires data to be switched at subwavelength granularity by means of subwavelength switching. In this thesis, we propose several solutions which enable subwavelength switching in optical networks. To show the relevance of the proposed solutions, we analyse their performance in terms of traffic capacity, flow throughput and packet delay. Performance is evaluated both through simulations and by means of appropriate queueing models. We first consider the case of Metropolitan Area Networks (MAN) and we study the performance of synchronous time-slotted Wavelength Division Multiplexing (WDM) ring in which network nodes communicate by inserting and extracting data from time-slots. We present a fully distributed Media Access Control (MAC) protocol designed to ensure fairness. We also propose a burst assembly mechanism able to ensure low assembly delays and high fill rates of the optical time-slots. We then propose subwavelength switching solutions which can be applied in the more general case of asynchronous wide area networks. We first propose to solve the contention problems of conventional Optical Burst Switching (OBS) and the low utilization issue of wavelength-routed OBS by implementing a two-way reservation OBS scheme in which the size of the optical burst increases proportionally with the network load so as to maximize resource utilization. Next, we propose a solution for building an all-optical wide area network based on multipoint-to-multipoint lightpath sharing. We also design an associated MAC protocol and a dynamic bandwidth allocation algorithm and analyse the performance of the proposed solution. By means of a case study, we show that the proposed solution has the potential to considerably reduce power consumption with respect to current router-based architectures. Finally, we propose a novel optical device able to solve contention directly in the optical domain without requiring any optical buffering, electronic signalling or header processing. We show that this simple device can be used as a building block for dynamic and powerefficient short-range optical networks such as access networks or data centers.