Unleashing 100-km Multi-Channel PDM Self-Homodyne Coherent Transmission by SOAs and All-Optical Nonlinear Distortion Mitigations

Cost-efficient coherent-lite solutions are highly desired in short-reach datacenter networks (DCNs). Self-homodyne coherent (SHC) scheme holds promise due to its compatibility with legacy coherent infrastructure and substantially reduced cost and power dissipation. Unfortunately, the inherent loss, resulting from the signal modulation and the propagations of both the signal and remote local oscillator (LO), poses a significant limitation on its link budget and hinders its application in metro-DCNs. In this paper, we propose to unleash the application of multi-channel polarization-division-multiplexed (PDM) SHC transmission in metro-DCNs by semiconductor optical amplifiers (SOAs) and two all-optical nonlinear distortion mitigation techniques. We show that by employing multi-wavelength remote LOs for multi-wavelength gain clamping (MW-GC), SOA-induced nonlinear amplitude and phase distortions can be significantly reduced. Additionally, it is demonstrated that SOA-induced nonlinear phase distortion on the signal can be compensated by the experienced nonlinear phase of orthogonally polarized remote LO after PDM-SHC detection (PDM-SHCD). Using these proposed techniques, we successfully demonstrate a 4-channel 50-GBd 16QAM PDM-SHC transmission over 100-km standard single-mode fibers and achieve a remarkable link loss budget of 25 dB, where only 9.8-dBm transmitter laser power is required per lane. Besides, we assess the impact of four-wave mixing-induced inter-channel interference in the multi-wavelength gain-clamped SOA and prove it to be negligible on the system performance when using a 200-GHz channel grid.