This paper investigates the theoretical performance analysis for a subcarrier
multiplexed (SCM) wavelength division multiplexing (WDM) optical transmission
system in presence of optical beat interference (OBI) which occurs during the
photo detection process. We have presented a comparison for improving the
performance of SCM-WDM system in presence of OBI. Non-return-to zero (NRZ),
Manchester and Miller code (MC) line coding are used for performance
investigation of SCM-WDM system. A suitable signal bandwidth is selected and
200 KHz is considered as channel bandwidth.