Direct-sequence spread spectrum time division multiple access with direct detection for latency optimized passive optical network

Abstract

To improve low-latency support of passive optical networks, direct-sequence spread spectrum time division multiple access implements bi-directional byte-interleaved transmission by encoding each bit of a bi-polar sequence with orthogonal chip pattern. Consequently, guard-interval between consecutive up-link bytes can be removed and latency caused by multi-point control protocol interaction can be reduced. However, direct-sequence spread spectrum requires bi-polar signaling, which is not possible with direct detection and several solutions exist, such as, biased and differential transmission. In this work, we investigate the performance of direct-sequence spread spectrum time division multiple access with direct detection and also analyze both up-link and down-link situations. Experimental results of transmission over a 20 km dispersion uncompensated link show: The 31-bits direct-sequence reduces required received signal power to −12 dBm and the performance is limited by dark-current. With differential transmission in up-link direction, modified duo-binary has 5 dB better performance than PAM4. Also, in up-link direction, differential transmission has 3 dB better performance than biased transmission.