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基于高阶正交幅度调制(QAM)和大线宽相干光正交频分复用(CO-OFDM)系统,提出了一种在时域进行无迹卡尔曼滤波(UKF)的相位噪声补偿算法。该算法在接收端基于训练符号频域卡尔曼滤波实现信道均衡,用较小的频域导频数据开销进行频域扩展卡尔曼滤波,先补偿公共相位误差(CPE)噪声,然后将CPE噪声补偿之后的数据在时域进行载波间干扰(ICI)相位噪声粗补偿。对相位噪声粗补偿后的频域数据进行预判决,结合接收端原始时域数据,在时域对判决后的数据进行UKF以实现ICI相位噪声的精细补偿。对精细补偿之后的频域数据再进行相位噪声粗补偿并进行迭代运算,极大地提高了相位噪声的补偿效果。对50Gbit·s-1的CO-OFDM系统进行了传输距离为100km的仿真,与其他算法相比,所提算法的频谱利用率极高,且具有较好的补偿效果。对激光器线宽为700kHz且调制方式为32QAM的传输信号进行二次迭代后,所提相位噪声补偿算法的误码率性能仍可达到前向纠错上限。所提算法促进了大线宽CO-OFDM系统在长距离接入网和城域网中的应用。
A phase noise compensation algorithm based on Unscented Kalman Filter (UKF) is proposed based on QAM and CO-OFDM systems. . The algorithm achieves channel equalization based on training symbol frequency-domain Kalman filtering at receiving end and performs frequency-domain extended Kalman filtering with smaller pilot data overhead in frequency domain, compensates for common phase error (CPE) noise first, and then compensates CPE noise Subsequent data are coarsely compensated for inter-carrier-interference (ICI) phase noise in the time domain. The pre-judgment of the frequency-domain data after rough compensation of phase noise is carried out. Combined with the original time-domain data of the receiving end, the UKF is performed on the judged data in the time domain to finely compensate the phase noise of the ICI. The coarse phase noise compensation and iterative calculation are performed on the frequency domain data after fine compensation, which greatly improves the compensation effect of phase noise. Compared with other algorithms, the proposed algorithm achieves a very high spectrum utilization rate and a good compensation effect for 50Gbit · s-1 CO-OFDM system with a transmission distance of 100km. After the second iteration of the transmission signal whose laser linewidth is 700kHz and the modulation method is 32QAM, the error rate performance of the proposed phase noise compensation algorithm can reach the upper limit of forward error correction. The proposed algorithm promotes the application of large linewidth CO-OFDM system in long-distance access network and metropolitan area network.