Abstract- This paper investigates the performance of direct detection technique for zero cross correlation code in Optical Code Division Multiple Access (OCDMA) which is a better technique to reduce Multi Access Interference (MAI). MAI is the main reason for performance degradation in optical CDMA especially when large numbers of users are involved. The implementation of direct detection whereby only a pair of decoder and detector is required as opposed with two pairs in the AND subtraction detection technique. OptiSystem Ver.7 has been used for simulation on system’s performance.It is possible since the code properties posses’ one clean signal chip for each of the channels. Subsequently, phase-induced intensity noise (PIIN) is suppressed at the receiver, thus the system performance is improved in term of signal to noise ratio and bit error rate. It has been shown that by using direct detection technique is better compare with other technique such as AND subtraction technique in ZCC code system as the varying the number of user is related to the power level of the received power is lower for BER 10-9. A larger number of users have higher insertion loss and smaller output power. For ZCC code, direct detection technique can support higher number users than the conventional technique because the number of filters at the receiver is reduced, thus a smaller power loss.
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