TTFR-based double time-encoded optical CDMA systems transmitting pulse-sequence with multiple power-levels

In this paper, we propose a mitigation technique of multiple access interference(MAI) for tunable-transmitter / fixed-receiver(TTFR)-based double time-encoded optical code-division multiple-access(CDMA) systems. The proposed system assigns distinct power-levels to each weight of second code-sequence and transmits the pulse-sequence with multiple power-levels. Double optical hard-limiters(DOHLs) with high-level thresholds can effectively eliminate low-power MAI as long as the intensity of incoming optical pulse is lower than the threshold value. By means of theoretical analysis, we show that the proposed system can achieve lower bit error probabilities than the conventional system transmitting the pulse-sequence with only one power-level.