Novel Coding Formats for Upstream Remodulation to Achieve Colorless Onus

Two novel coding formats (PAM complement coding and amplitude-variable line-coding) are proposed to achieve colorless ONUs for PONs applying wavelength division multiplexing (WDM). The colorless ONU is achieved by remodulating the upstream signal on the downstream carrier. The novel coding formats combine the spectrum shaping coding and pulse amplitude modulation (PAM). Spectrum shaping coding suppresses the low-frequency component of the downstream signal and thus reduces the crosstalk to the remodulated upstream signal. PAM increases the code efficiencies in the proposal. The downstream signals could be received by traditional binary receivers, even PAM is applied. The remodulation schemes based on the proposed coding formats are demonstrated by simulation. The performance of the 625Mb/s and 1.25Gb/s upstream signals remodulated on 10Gb/s downstream signal is tested. The crosstalk to the remodulated signals is much reduced and the code efficiencies of the downstream signals are increased compared with previous proposals.