Study On Effect Of Dispersion And Nonlinearity On The BER Of OCDMA System

OCDMA system is a new technology which has potential . development .Over TDM and WDM, advantages of OCDMA are free of network control among many users, asynchronous communications access random and need not delay. Its performance affected by simultaneous users and receiver noise. At present, the optical pulse using in optical code-division multiple access (OCDMA) is Gauss signal which breadth is at ps. This kind of signal may be affected by the GVD and SPM when it is transmitted by fiber, accordingly the optical multiple access interference (OMAI) raise and the BER is deteriorated. In this paper, the performance varieties due to GVD and SPM have been studied considering OMAI. The formula of BER modified is given, numeric calculation is done, and the corresponding curve is worked out. The result shows that if users and distance is given, BER will deteriorate 10~2-10~3 when consider GVD and SPM .The threshold higher, the BER better. It is suggested Optical hard limiter and DSF (dispersion-shifted fiber) should be used in order to improve the performance of OCDMA system. The studies provide a significant reference for design and analysis of OCDMA system.