Multi-Level Phase Noise Model for CO-OFDM Spatial-Division Multiplexed Transmission

Spatial division multiplexed (SDM) transmission systems with coherence communication technology have become an important issue in meeting the demands for the capacity of fiber. However, research on the phase noise from lasers is mainly focused on single-channel systems or single-carrier SDM systems. In this paper, a phase noise model comprising common laser phase noise, in addition to the core phase drifts induced by the SDM, is introduced and analyzed for a coherence orthogonal frequency-division multiplexing (CO-OFDM) spatial-division multiplexed transmission (SDM) system. Based on the phase noise model, the applicability of the blind phase search algorithm and the pilot-aided phase estimation algorithm is discussed and demonstrated via simulation. The results show that these two algorithms can work well when considering combined laser linewidths with core phase drifts for CO-OFDM 7-core multi-core fiber (MCF). The results mean that with the SDM phase noise model, phase noise estimation in other cores can be transferred from one core to lower the complexity with the help of the model. This research provides a proper application of the phase noise analysis of large-capacity optical communication based on a weak-coupled MCF.