Mitigation of MAIs by the second encoding scheme in TTFR-based optical CDMA systems

In optical code division multiple access(CDMA) networks, the system which equips tunable transmitters and fixed receivers (i.e. TTFR) achieves simple configuration and protocols. However, when there are other simultaneous users who transmits pulses with the same code, large amount of multiple access interferences(MAIs) cause serious performance degradation. In this paper, we propose second encoding scheme in which first-encoded optical pulses are further encoded by the second optical orthogonal code(OOC) assigned to the transmitter. The proposed system with second encoding scheme can achieve higher processing gain in the correlator than the conventional system without second encoding scheme because the number of weights increases due to the second encoding. This results in the mitigation of the effect of MAIs. We analyze performance of the proposed system and show that the proposed system with second coding scheme can achieve better bit error probability than the conventional system without second encoding scheme.