Research on QPSK carrier recovery based on OPLL in inter-satellite coherent laser communication

Doppler frequency shift, laser linewidth, phase noise and other interference in inter-satellite coherent laser communication pose new challenges to system carrier recovery. In this paper, a new optical phase-locked loop based on the loose tail phase discrimination method is applied to the QPSK homodyne coherent receiving system, and its modeling analysis is carried out. The optical phase-locked loop can achieve carrier recovery, which meets the high accuracy requirements of QPSK modulation for frequency and phase. The simulation analysis shows that the optical phase-locked loop can track the frequency offset of 10MHz/s, and can still work normally when the signal optical power is -50dBm, which is 5dB higher than the classical Costas optical phase-locked loop. It is one of the solutions for carrier recovery in coherent laser communication receiving system under QPSK modulation system, and provides a reference for coherent demodulation verification of QPSK homodyne coherent laser communication system.