Bidirectional passive optical network based on optical CDMA technique

A 15 Km in-band bidirectional passive optical network based on optical code division multiple access (OCDMA) system was simulated, using direct detection method, which has been achieved by modulating the carrier wave with a modified quadratic congruence code sequence (MQC). This paper investigates the performance of in-band bidirectional OCDMA system in terms of data rate, channel spacing, transmit power and channel length, 9 subscribers were used for each direction. It has been found that the maximum data rate for in-band bidirectional system cannot exceed 0.15Gbps for small channel spacing at -22dBm receiver sensitivity. This is due to the big influence of Rayleigh Backscattering between the signals propagating in opposite directions which degrade the quality of the signals. The data rate can only be increased if the up/downstream uses different bands.