A high dynamic carrier acquisition and tracking algorithm for space coherent optical communication

Abstract

In coherent optical communication, the Doppler frequency offset reaches several GHz, which seriously affects the performance of the coherent demodulation system and increases the bit error rate. In this paper, a novel carrier acquisition and tracking algorithm for spatial coherent optical communication is proposed. The algorithm adopts the dual-locked frequency loop that the CPAFC tracking algorithm is effectively combined with the ODAFC tracking algorithm. The CPAFC tracking algorithm can be used for frequency offset gradually change capture and tracking, and the ODAFC tracking algorithm can capture large frequency offset, and according to the locked state control the working state of the two FLL loops. In the condition of stable locked, use only the CPAFC tracking algorithm to capture the gradually changing frequency offset; in the other condition, use two FLL loops together. The experimental results show that the 5Gbps BPSK laser communication performance loss is less than 1.5 dB when the Doppler frequency offset is 2.5 GHz, and the carrier frequency offset change rate is 20 MHz/s.