Technologies for future wavelength division multiplexing passive optical networks

This study reviews key technologies of next generation wavelength division multiplexing passive optical networks (WDM‐PONs). The authors have studied WDM‐PONs with centralised lightwave source and direct detection, where a wavelength‐reuse system is employed to transmit the uplink data by using a colourless transmitter at the optical network unit (ONU). WDM‐PON system was demonstrated using a Fabry–Perot laser diode as a colourless transmitter at the ONU for differential phase‐shift keying (DPSK) downlink signals and on–off keying uplink signals. The constant‐amplitude feature of the DPSK modulation could retain a great extinction ratio of the downlink signal and decrease the noise to the uplink signal. The proposed scheme offers a promising solution for future PONs.