Multiplier-free QPSK phase recovery for coherent intersatellite optical wireless communication

In this paper, a quadrature phase shift keying (QPSK) phase-recovery algorithm is presented for coherent intersatellite optical wireless communication (IsOWC). From a theoretical perspective, we explain the process of the multiplier-free algorithm. Through simulations, we analyze key parameters and provide guidance on their optimal selection. Additionally, the proposed algorithm maintains stable phase tracking at bit energy to noise power spectral density (Eb/N0) as low as 4 dB. In an ob2b transmission test, our algorithm achieved a sensitivity of -49 dBm @5 Gbps QPSK [hard-decision forward-errorcorrection (HD-FEC) limit]. Compared to the Viterbi and Viterbi phase-recovery (V&V) algorithm, its receiving sensitivity is improved by 1 dB, resulting in a link distance extension of 1100 km. Our multiplier-free and robust algorithm meets the requirements of IsOWC systems and shows promise for future applications.