Design and simulation of OCDMA encoder and decoder for high capacity in optical networks

Abstract

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 thesis, using Modified Double Weight (MDW) codes are used as signature sequences for SAC-OCDMA systems. The performance analysis of the suggested MWD codes are firstly derived mathematically and subsequently carried out through simulation experiments using OptiSystem software. In spite of the performance enhancement afforded by receiver decoder used to traditional AND subtraction detection. The maximum performance improvement was not achieved. Moreover, in term of cost, the reported technique is considered cost-effective as the LED light source is used to generate the sideband codes.