Interference mitigation using successive interference cancellation in optical CDMA systems

Performance of optical code division multiple access (O-CDMA) system is influenced by multiple access interference (MAI) resulted from the overlapping between the users. To overcome this problem, successive interference cancellation (SIC) scheme is applied to O-CDMA systems. In this paper we apply successive interference cancellation technique to a spectral amplitude coding (SAC) system that uses modified quadratic congruence (MQC) codes as signature sequence codes. The system is analyzed for two cases: same effective power for all the users and different effective power from each user. It is shown that under ideal effective power the SIC/SAC optical CDMA systems have potential to suppress the intensity noise and mitigate multiple access interference. Hence, using SIC/SAC cancellation scheme, the system can accommodate much more number of users as compared to the one without cancellation. Further, under ideal power the system using SIC scheme with direct sequence encoding (SIC/DS) shows much lower BER performance as compared to the one without cancellation (i.e. conventional receiver) or to SIC/SAC cancellation scheme. Hence, much more number of users can be accommodated by SIC/DS receiver system. Furthermore, SIC/DS scheme still shows much lower BER performance as compared with SIC/SAC scheme under different effective power.