相干光M-PSK系统的弹性DAML相位估计算法

Flexible DAML phase estimation algorithm in coherent optical M-PSK systems

相干光通信系统中判决辅助式最大似然(DAML)相位估计算法因其较高的计算效率引起了广泛的关注.然而,传统DAML相位估计算法假设激光器相位噪声在整个块长度区间内是恒定不变的,这引起了块长度效应.本文考虑了激光器相位噪声缓慢时变的特点,并提出了基于相干光M-PSK系统的弹性DAML相位估计算法来克服传统DAML相位估计算法中存在块长度效应的缺点.该算法在传统DAML算法的基础上引入了加权系数来更准确地进行载波相位恢复.同时,本文推导了该算法的相位估计误差,并用仿真验证了其有效性.仿真结果也表明:弹性DAML算法能消除传统DAML算法的块长度效应,并能放宽相干光M-PSK系统对激光器线宽的要求.

Decision-aided maximum likelihood（DAML） phase estimation has been applied in coherent optical communication systems due to its high computational efficiency. However, conventional DAML algorithm only considers constant laser phase noise over the entire block length, thus causing block length effect. Given time-varying laser phase noise, a flexible DAML phase estimation algorithm is proposed in coherent optical M-PSK systems, which can eliminate the block length effect of conventional DAML. Weighted coefficients are introduced to estimate carrier phase more accurately than the conventional algorithm. Meanwhile, the phase estimation error is derived and simulations justify its validity. Simulation results also show that the flexible DAML algorithm can eliminate the block length effect of conventional DAML and relax the requirement of laser linewidth in coherent optical M-PSK systems.