Novel Detection Techniques for SAC-OCDMA Systems

Optical Code Division Multiple Access (OCDMA) systems are outstanding candidates for flexible implementation in the optical access networks because they offer many attractive features, such as asynchronous access ability, enhanced information security, and differentiated Quality of Service (QoS). However, conventional OCDMA systems are plagued with Multiple Access Interference (MAI) that originates from other simultaneous users. This in turn ultimately limits the number of active users in a given OCDMA system. Among incoherent OCDMA systems, Spectral Amplitude Coding (SAC) is a promising multiple access scheme for future high speed access networks, mainly due to MAI suppression abilities and low cost. Indeed, it was shown that it is possible to alleviate MAI in SAC-OCDMA systems by using subtraction detection techniques with fixed in-phase cross-correlation codes. Another limiting factor in the performance of incoherent SAC-OCDMA systems is the Phase Induced Intensity Noise (PIIN). PIIN severely restricts the data transmission rate of each user, impairs the communication quality, and limits the capacity of incoherent SAC-OCDMA systems. In this thesis, two novel detection techniques, namely, Modified-AND subtraction detection and Single Photodiode Detection (SPD) are proposed for mitigating both MAI and PIIN noises in incoherent SAC-OCDMA systems. Modified Double Weight (MDW) codes are used as signature sequences for SAC-OCDMA systems.