A pilot-symbols-aided unscented Kalman filter for carrier phase recovery in the wide-linewidth short-range coherent optical transmission systems

Abstract

Abstract In this paper, we propose a pilot-symbols-aided unscented Kalman filter (UKF) for carrier phase recovery in the wide-linewidth short-range coherent optical transmission systems. The UKF algorithm is used to estimate and compensate the phase noise, and the pilot symbols as the initial phase noise of UKF can improve the convergence speed and eliminate the error propagation caused by cycle slip. The proposed algorithm is verified in 448 Gb/s polarization division multiplexing 16 quadrature amplitude modulation (PDM-16QAM) coherent optical transmission system over a 20 km standard single-mode fiber (SSMF). Compared with the commonly used extended Kalman filter (EKF) and UKF, the pilot-symbols-aided UKF has more accurate phase noise estimation ability and higher laser linewidth tolerance. It can enhance the linewidth symbol duration product from 6.5 × 10 - 5 (EKF) and 8.7 × 10 - 5 (UKF) to 1.35 × 10 - 4 . Thus the pilot-symbols-aided UKF will be a feasible carrier phase recovery method in the low-cost wide-linewidth short-range coherent optical transmission systems.