20-Gb/s polarization division multiplexed WDM PON transmitter based on self seeded RSOAs

Reflective semiconductor optical amplifier (RSOA)-based self-seeded (SS) transmitters have proved to be compact self-tuning transceivers for wavelength division multiplexed passive optical networks (WDM PONs). The small electro-optical bandwidth of currently available RSOA devices limits the maximum bit-rate for each transmitter. We thus propose a self-tuning WDM PON multilevel transmitter based on self-seeding in two RSOAs co-located at the network end (e.g. at the optical network unit (ONU)). The architecture takes advantage of a single cavity which sustains two mode families with orthogonal polarizations, thanks to the exploitation of the Faraday rotator mirror (FRM)-based retracing optical circuit. The multilevel transmission allows a capacity doubling, overcoming the RSOA bandwidth limitations. We analyse the build up and the modulation response of the proposed transmitter when exploiting two O-band RSOAs, showing spectra and output eye diagrams. The polarization division multiplexed transmitter performance from 5 Gb/s to 20 Gb/s are presented with propagation over up to 50-km standard single mode fibre, demonstrating BER below the FEC limit.