Journal Paper

Coherent technology provides the high spectral efficiency and enhanced receiver sensitivity required to support 100/200/400 Gb/s per wavelength in next-generation passive optical networks (PONs). Moreover, the power budget of coherent PONs can be further increased by employing semiconductor optical amplifier (SOA)-based boosted transmitters, enabling extended reach and higher split ratios. However, SOAs introduce strong nonlinear distortions under saturation. We experimentally demonstrate a low-complexity DSP-based nonlinear compensator (SOA-NLC) to mitigate SOA-induced impairments in coherent PONs. The approach combines a simplified physical model with BER-driven parameter optimization and is compatible with practical receiver DSP. Power budget extensions of up to 14 dB are achieved for 200 Gb/s dual-polarization 16-QAM signals, with up to 2 dB additional gain enabled by SOA-NLC. The results show that, when using 16-QAM modulation, implementing nonlinear compensation is more effective than increasing the carrier phase recovery (CPR) pilot overhead. However, when employing QPSK modulation, using only CPR already effectively mitigates the impact of SOA-induced phase distortions.