Development of a new class of zero cross correlation codes for optical CDMA systems
Mohd Rashidi, Che Beson
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In this thesis, presented a method for development of a new class of optical code for Optical Code Division Multiple Access (OCDMA) system using Spectral Amplitude Coding. The proposed code is called Modified Zero Cross Correlation Code (MZCC) and Modified Non Zero Cross Correlation Code (MNZCC). From theory, the proposed method is to construct optical codes with simple code construction for any number of users, any cross correlation and for a given weights having minimum length. MZCC code has been designed with cross correlation is equal to zero due to eliminating the effects of Multi Access Interference (MAI) thus to prevent from overlapping of spectra from each users. These codes is easily to construct, simple and have better noise performance compared with existing optical codes such as ZCC code. While, MNZCC code presented in this thesis is to have unfixed cross correlation and it can be designed with any desired cross correlation. MNZCC have minimum code length, easier to constructed and the ability of this code is better than existing optical codes. The requirement in OCDMA systems to have minimum code length with any desired cross correlation is the reason of these codes has been designed. The performances of proposed codes were simulated using commercial simulation software, OptiSystem Version 6.0. The performance of the systems was characterized by referring to the Bit Error Rate (BER). From the simulation results, at distance 25km with bit rate 155Mbps, MZCC code have better BER 10-12 as opposed to BER for ZCC code is equal to 10-5 which is not error rate for standard optical communication systems threshold.