Joint Doppler and Phase Noise Compensation Method for Inter-Satellite Coherent Laser Communication

The rapid relative motion between low Earth orbit satellites leads to fast-varying Doppler shifts, and the laser linewidth which caused by the frequency instability of the laser source induces phase noise in laser communication links. Facing these challenges in optical communication, methods capable of accurate phase tracking under large laser linewidth conditions are needed. We propose an ephemeris-driven dual-loop integrated Doppler and phase noise compensation method. It achieved accurate compensation for wide-range frequency offsets and Wiener phase noise to enable phase synchronization under timevarying Doppler shifts. The simulation results show that the proposed method can estimate frequency offsets of up to 8 GHz. The performance degradation is less than 0.5 dB under a frequency offset variation rate of $150 \mathrm{MHz} / \mathrm{s}$ and Wiener phase noise corresponding to a laser linewidth of 10 kHz. The method maintains its effectiveness at an energy per bit to noise power spectral density ratio of 3 dB, which plays a key role in enabling reliable inter-satellite laser communication.