在相干光通信系统中,激光器相位噪声导致信号在复平面内发生旋转,因此需要在接收端对信号进行载波相位估计和恢复。在利用M次方载波相位恢复算法进行相位估计时,简化了对相邻N个符号进行求和取平均以减小加性高斯噪声影响这一步,将由残余频偏、相位噪声及加性高斯噪声引起的总相位偏移量看作一个整体,直接估计出每个符号的总相位偏移,之后再恢复出调制相位。通过仿真比较了该算法与传统M次方载波相位恢复算法的性能,用该算法进行相位恢复后,信号的相位与原调制相位之间的误差只有10 ^-16 rad,而采用传统算法相位恢复后的误差可达0.3 rad,表明所提算法能够更加准确地恢复出调制相位,具有更高的估计精度。利用本文算法可在没有进行频偏补偿的条件下,直接完成相位恢复,而传统算法只能对频偏补偿后的信号进行相位恢复。此外,由于减少了求和取平均这一步,本文算法的复杂度也得到了降低。

In coherent optical communication systems, phase noise of the laser causes the signal to rotate in the complex plane; therefore, the estimation and recovery of carrier phase are required at the receiving end. Herein, when using the M-th power carrier phase recovery algorithm to estimate the phase, we simplify the summing and averaging of adjacent N symbols to reduce the influence of additive Gaussian noise. The proposed algorithm considers the phase shift caused by the residual frequency offset, phase noise, and additive Gaussian noise together. Then, the algorithm estimates the total phase shift caused by these three factors and resumes the modulation phase. The performance of the proposed algorithm is compared with that of the traditional M-th power carrier phase recovery algorithm in the simulation. After the phase recovery by the proposed algorithm, the error between the signal and original modulation phases is only 10 -16 rad. However, when using the traditional algorithm, the error can reach 0.3 rad, implying that the proposed algorithm can recover the modulation phase more accurately and has a higher estimation accuracy. In the simulation, even without compensating for the frequency offset, phase recovery can be realized using the proposed algorithm, while the traditional algorithm can only recover the phase of the signal after compensating the frequency offset. In addition, the complexity of the algorithm is reduced by reducing the summing and averaging step as well.