Comparison and analysis of codes for remodulation WDM-PON with adaptive code selection

In a remodulation PON, the upstream signal quality can be improved when the downstream signal is coded. But low code efficiency may result in network congestion in downlink. Based on the downlink traffic, a self-adapting PON can select the proper downstream modulation codes to achieve the optimal network performance. With adaptive code selection, network congestion can be avoided and the remodulated upstream signal suffers minimal performance degradation. Some codes of various coding efficiency are required to be selected in this self-adapting PON. These codes should induce as little crosstalk to the upstream signal as possible. Several candidate codes with coding efficiencies from 50% to 80%, such as Manchester code, 3b5b code, 4b5b code, 4b6b code and 6b8b code are tested through simulation and experiment in this paper, and their performances are compared. The results show that the optimum code for downstream modulation depends on the downlink traffic and the upstream bit rate. The results will help the self-adapting remodulation WDM-PON to select the proper downstream modulation codes in different traffic situations.