BER performance analysis of a FSO OCDMA communication system with receive diversity using SIK dual photodetector receiver

Abstract

An analytical approach is represented to evaluate the bit error rate (BER) performance results of an optical CDMA (OCDMA) free space optical (FSO) communication system with receive diversity using multiple photodiode dual-detect Sequence Inverse Keying (SIK) receiver. The analysis is presented to find the expression for the signal current and multi access interference (MAI) current at the output of an equal gain combiner (EGC) in presence of atmospheric channel effect, atmospheric turbulence and pointing error. The performance results in terms of BER are evaluated for different values of code lengths, number of receiver antennas, number of simultaneous user and the system parameters. It is found that, significant degradation in the receiver BER performance due to the atmospheric channel effect and in presence of pointing error can be substantially reduced by increasing the number of photodetectors. Further improvement in the receiver sensitivity can be obtained by increasing the optical code length for a given number of user at a given BER of 10−9. For example, at a BER of 10−9 and number of user K=16 sensitivity improvement due to receive diversity is found to be 2.15 dB, 2.35 dB, 2.6 dB corresponding to processing gain of 64, 256 and 512 respectively for number of photodetector receiver of 4.