Phase-Modulation-Based Loopback Scheme for Rayleigh Noise Suppression in 10-Gb/s Carrier-Distributed WDM-PONs

We propose a novel scheme to suppress Rayleigh noise in carrier-distributed wavelength-division-multiplexed passive optical networks, by using differential phase-shift keying (DPSK) as the upstream modulation format. Due to the narrow spectrum of the distributed carrier, the Rayleigh noise towards the optical line terminal (OLT) also has narrow spectrum and can be effectively suppressed by the notch filter-like destructive port of the delay-interferometer at the OLT, which is used to demodulate the upstream DPSK signal simultaneously. Experimental demonstration of the 10-Gb/s upstream signal is achieved with less than 0.2-dB power penalty induced by Rayleigh noise after the transmission of 20-km single-mode fiber.