Analysis of Influence of Polarization Mode Dispersion on Tb/s Single-Carrier Coherent Optical Fiber Communication Systems

In ultrahigh-speed coherent optical fiber communication systems, increasing single-carrier data rate is usually considered the foundation for the data rate increase of wavelength division multiplexing (WDM) communication systems. In single-carrier optical fiber communication systems, polarization mode dispersion (PMD) is one of the most critical factors affecting the data rate increase. This article quantitatively analyzed the impact of first-order, second and higher-order, full-order PMD on coherent fiber communication systems at the single-carrier bit rate of Tb/s levels from the perspective of error vector magnitude and symbol error rate (EVM/SER). The constant modulus algorithm (CMA) was analyzed for PMD compensation performance. Finally, the optimal tap numbers of the CMA were calculated in three cases of PMD. The results show that the optical signal-to-noise ratio (OSNR) tolerance limit can be improved by 6.7 dB and 6 dB, respectively, in first-order PMD and second and higher-order PMD. SER and EVM in second and higher-order PMD are almost 100% and 99.36% better than in first-order PMD, given the compensation performance of CMA. The optimal tap numbers of CMA differ in three cases of PMD.

在超高速相干光纤通信系统中，提升单载波数据速率通常被视为波分复用（WDM）通信系统总数据速率提升的基础。在单载波光纤通信系统中，偏振模色散（PMD）是制约数据速率提升的最关键因素之一。本文从误差矢量幅度与符号差错率（EVM/SER）的视角，定量分析了一阶、二阶及更高级阶乃至全阶偏振模色散对Tb/s级单载波速率相干光纤通信系统的影响。本文分析了恒模算法（CMA）的偏振模色散补偿性能，并针对三种偏振模色散场景计算了恒模算法的最优抽头数。结果表明，在一阶偏振模色散与二阶及更高级阶偏振模色散场景中，光信噪比（OSNR）的容限极限分别可提升6.7 dB与6 dB。在恒模算法的补偿前提下，二阶及更高级阶偏振模色散场景下的符号差错率与误差矢量幅度分别比一阶偏振模色散场景提升了近100%与99.36%。三种偏振模色散场景下，恒模算法的最优抽头数存在差异。