CO-OFDM系统中的相位噪声补偿算法

为了提高相干光正交频分复用（coherent optical orthogonal frequency division multiplexing，CO-OFDM）系统的性能，针对系统中产生的相位噪声，例如公共相位误差（common phase error，CPE）噪声与子载波间干扰（inter-carrier interference，ICI），提出了一种新的CO-OFDM系统中相位噪声补偿算法，该算法是基于循环前缀（cyclic prefix，CP）插值算法与容积卡尔曼滤波（cubature Kalman filter，CKF）结合的相位噪声补偿算法。在第一阶利用CP进行线性插值，消除了公共相位误差（common phase error，CPE）噪声，对一阶补偿后的信号进行预判决，通过划分次符号，消除了部分载波间干扰（inter-carrier interference，ICI），利用CKF对信号残余的相位噪声进行处理，经过两阶补偿，有效地抑制相位噪声。仿真结果表明，所提出的算法能有效降低相位噪声对系统的影响，在线宽较大时能改善CO-OFDM系统对激光器线宽的容忍度，降低错误平层，有效提高系统的性能。

Phase noise compensation algorithm for CO-OFDM systems

In order to improve the performance of coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems, we propose a new phase noise compensation algorithm in CO-OFDM system for the phase noise generated in the systems, such as common phase error (CPE) and inter-carrier interference (ICI). This algorithm is a phase noise compensation algorithm based on the combination of the cyclic prefix (CP) interpolation with the cubature Kalman filter (CKF). In the first stage, this algorithm uses the cyclic prefix to interpolate and eliminates the CPE noise. The signal is pre-judged after the first-stage compensation, and then the part ICI is eliminated by dividing the sub-symbols. Finally, CKF is used to deal with the signal''s residual phase noise, and the phase noise is effectively suppressed after two-order compensation. Simulation results show that the proposed algorithm can effectively suppress the influence of the phase noise on the signal, improve the tolerance of the CO-OFDM system to the laser linewidth under the larger linewidth, reduce the error floor and effectively enhance the performance of the system.