Full-Duplex RSOA-Based PONs Using 4-PAM With Pre-Equalization

We investigate the use of 4-pulsed amplitude modulation (PAM) in reflective semiconductor optical amplifier (RSOA)-based PON implementations. The performance of low-bandwidth RSOAs can be significantly upgraded using 4-PAM together with pre-equalization. We demonstrate 4-PAM external modulation up to 8 Gb/s using a RSOA with a 3-dB bandwidth of 1.2-GHz and 10-km 4-PAM transmission at 8 Gb/s with bit-error-rate below the forward-error-correction (FEC) limit. In the full-duplex 4-PAM transmission, 10-km symmetric performance up to 4 Gb/s is experimentally demonstrated using a downstream signal with strong DC offset for data cancelation and upstream remodulation.