Performance analysis of multi-wavelength optical CDMA system over atmospheric turbulence FSO channel using SIK receiver

Abstract

An analytical study is carried out for evaluating the effect of atmospheric turbulence (AT) on the bit error rate (BER) performance of a multi-wavelength optical code division multiple access (CDMA) free space optical (FSO) system using optical domain encoder and Sequence Inverse Keying (SIK) balanced photodetector receiver. The analysis is represented to derive the expression of the signal current, multi-access interference (MAI) current and cross-talk current at the output of the SIK receiver considering the effect of AT due to FSO channel. The expression of average BER is found out by averaging the conditional BER over the effect of probability density function (PDF) of the AT. The numerical performance results are evaluated for different code length, number of simultaneous user, link distance and other system parameters. It is found that, the performance of a multi-wavelength optical CDMA system with a SIK receiver is degraded significantly due to AT effect and suffers considerable amount of power penalty at a given BER. The penalty is found to be 1 dB to 9.5 dB for link distance ranges from 500 m to 4000 m with user number 16 and code length 1024 at BER=10−9.