Rayleigh Backscattering Rejection in Single-Laser Homodyne Transceiver for UD-WDM Using λ-Shifting

With the aim of using a single laser per transceiver in single fiber splitter-based passive optical networks (PON) with coherent homodyne receivers, we apply wavelength shifting in an ultra-dense wavelength division multiplexing (UD-WDM) scheme. The studied architecture is based on a dual-parallel Mach-Zehnder Modulator (DP-MZM) operating in carrier-suppressed single-sideband (CS-SSB). In this configuration, a single laser feeds both the coherent homodyne receiver, and the transmitter, simplifying the wavelength management in the PON. The modulator carries out both data modulation and wavelength shifting. In this study, a bit rate of 4 Gb/s in QPSK is used to test several roll-off factors and channel spacing configurations. The results show that power budget gains of 18 dB are achievable with a channel spacing equal to only the symbol rate.