Overlapped-Subcarrier Multiplexing for WDM Passive Optical Networks: Experimental Verification and Mathematical Analysis

An innovative overlapped-subcarrier multiplexing (O-SCM) technique is proposed for single-feeder wavelength-division multiplexed (WDM) passive optical networks (PONs). Allowing a certain amount of spectral overlap between the uplink and the downlink maximizes the spectrum usage of bandwidth-limited reflective semiconductor optical amplifier (RSOA)-based optical network units (ONUs), while reducing the effect of Rayleigh backscattering. In this paper, we report successful experimental demonstrations up to 2.5 Gb/s symmetrical bit rates over a ~20 km bidirectional PON, using a ~2 GHz bandwidth RSOA. Moreover, we mathematically address the major design issues and tradeoffs. Our simulation results show good agreement with the experiment.