基于简化扩展卡尔曼滤波的双偏振载波相位恢复算法

Dual-Polarization Carrier Phase Recovery Algorithm Based on Simplified Extended Kalman Filter

提出一种基于简化扩展卡尔曼滤波(EKF)的低复杂度、双偏振载波相位恢复算法,记为XY-EKF算法。XY-EKF算法通过估计并补偿两个偏振态之间的相位偏移,只利用X偏振态的实部和Y偏振态的虚部(或X偏振态的虚部和Y偏振态的实部)对两个偏振态进行相位恢复,减少了卡尔曼滤波所需的信号分量。XY-EKF算法能够在保持估计准确度的前提下降低算法的复杂度。将XY-EKF算法应用于传输速率为224 Gbit/s的双偏振16QAM相干光传输系统,仿真结果表明,当激光器线宽和信号码元周期乘积分别为10^-5和10^-4时,XY-EKF算法与经典EKF算法具有等同的性能表现,而其复杂度相比经典EKF算法降低了1/3。在光信噪比一定的条件下,当误码率为3.8×10^-3时,XY-EKF算法的线宽容忍度比经典EKF算法提升了1 MHz。

In this study, a low-complexity dual-polarization carrier phase recovery algorithm has been proposed based on a simplified extended Kalman filter(EKF),which is called XY-EKF algorithm. The signal component required by the Kalman filter is reduced by estimating and compensating for the phase offset between two polarizations. Further, the phase recovery of two polarizations is performed only using the real part(imaginary part) of the X polarization state and the imaginary part(real part) of the Y polarization state, thereby reducing the complexity of the algorithm while maintaining the estimation accuracy. The XY-EKF algorithm is applied to the dual-polarization 16 QAM coherent optical transmission system with transmission rate of 224 Gbit/s. The simulation results denote that XY-EKF algorithm exhibits a performance similar to that exhibited by classical EKF algorithm when the products of the laser linewidth and symbol duration are 10^-5 and 10^-4 with a 1/3 reduction in complexity. Furthermore, when the BER is 3.8×10^-3, the linewidth tolerance of the XY-EKF algorithm is 1 MHz higher than that of the EKF algorithm with an identical optical signal-to-noise ratio.