Equal weight code sequence per slot for optical PPM-CDMA communication systems

The performance of direct detection optical fiber pulse position modulation (PPM) code division multiple access (CDMA) communication systems with equal weight code sequence per slot (EWPS) is investigated. Upper bounds of bit error rates for such multibit transmission with multiple access schemes are estimated considering multiple-user interference (MUI) in the analysis. We investigate the performance with the assumption of Poisson shot noise model for the PIN photodiode and synchronization between users symbols. It is shown that the EWPS-PPM scheme outperforms the former on-off orthogonal (OOO)-PPM system especially when the pulse position multiplicity is low with average power constraint on the laser.