偏振模色散补偿中2种偏振度取样方式的特性

Performance of Two Sampling Modes for Degree of Polarization Used as Feedback Signal in Polarization Mode Dispersion Compensation

建立了一个数值计算模型,详细分析了40Gbit/s光纤通信系统中,以偏振度作为反馈控制信号的偏振模色散自动补偿技术的2种取样方式的性能.通过数值模拟计算了补偿后的误码率和偏振度,结果表明,以单偏振态的偏振度作为反馈信号的取样方式只能用于自由度较少的2段偏振模色散补偿器进行偏振模色散补偿,对于自由度较多的3段偏振模色散补偿器则达不到理论上的预示效果,反而有可能陷入局部极大值而引入高阶偏振模色散,使得补偿后误码率变大.使用4个以上的自由度进行补偿则宜采用偏振度椭球的短轴作为反馈信号.

A numerical model is founded to analyze the performance of two sampling modes for polarization degree as controlling signal with various polarization mode dispersion compensators in 40 Gbit/s optical fiber communication, numerical simulation results including the compensated bit error rate （BER） and polarization degree of 1000 sampling points show that when single state of polarization sampling mode is used in two stages and three stages polarization mode dispersion （PMD） compensator with more than four degrees of freedom, the numbers of degree of freedom for the compensators should not be more than four, otherwise, the compensation algorithm will be plunged in local maximum to cause severe PMD that increase bit error. So, another sampling method is proposed to be suit for three section PMD compensator, in which shortest axis lengths of degree of polarization （DOP）ellipsoid is used as the feedback signals. The performance of DOP ellipsoid is evaluated by means of numerical simulations with three-section compensator, which is better than that of single state of polarization sampling mode.