Adaptive Time Window Control Scheme for Asymmetric Traffic in Hybrid WDM/TDM-PON

Hybrid WDM/TDM-passive optical network (PON) is a modified architecture of the WDM-PON based on gain- saturated reflective semiconductor amplifier (RSOA). In this system, the number of splitting ratios should be limited to four due to remodulation scheme for uplink signals within gain- saturated regime of RSOA. To address this problem, we propose a novel frame format, which doubles splitting ratios by applying shared-time division duplex (TDD) scheme. Moreover, adaptive time window control scheme is designed to find an optimal TDD boundary according to the amount of traffic in each link. Comparing fixed-boundary algorithm, simulation results show that the proposed scheme effectively controls the bandwidth, and thus improves total queueing delay and throughput. In spite of some bandwidth loss when applying this scheme, therefore, it makes no performance degradation to the existing system in asymmetric traffic while increasing the number of capable subscribers.