Multi-user detection for the OCDMA: Optical parallel interference cancellation with optical limiter

Optical Code Division Multiple Access Multiple (OCDMA) is considered as the strongest candidates for the future ultra-high speed optical networks due to the huge bandwidth offered by the system. However, Multiple Access Interference (MM) which is originated from other simultaneous users is the major reason for the system degradation in the OCDMA systems. MAI increases with the number of simultaneous users, resulting in higher bit error rate and limits the maximum number of simultaneous users in the OCDMA system. Several techniques have been proposed and discussed in the literature aiming at lowering the effect of MAI. In particular, Optical Parallel Interference Cancellation (OPIC) has been extensively studied for the sake of reducing the MAI. In this paper, an Optical Hard Limiter (OHL) has been used in front of the receiver side to reduce the effects of MAI. OHL improves the performance of OPIC system because of its ability to exclude some combinations of interference patterns from becoming heavily localized in a smaller part of non-zero positions of signature codes. Moreover, it is found that high performance of OPIC can be obtained by selecting the minimum threshold value for the desired user. The results reveal that, the optical hard limiter improves the performance of the conventional OPIC while reducing the effect of MAI. Concurrently the system. ©2001 IEEE.