少模光纤通信系统中模间非线性相位调制的补偿分析

Analysis of Compensation for Inter-Mode Nonlinear Phase Modulation in Few-Mode Optical Fiber Communication Systems

考虑少模光纤中自相位调制和交叉相位调制效应对导波光传播特性的影响,给出了相应非线性耦合模方程的解析解,并用于计算少模光纤的非线性系数和分析少模光纤通信系统的非线性补偿。以支持两个线偏振(LP)模的四相相移键控(QPSK)信号系统为例,仿真分析了模式损耗和非线性效应对模分复用系统性能的影响,重点分析了模间相位调制的补偿作用和补偿算法的适应性。研究表明,补偿后能够正确解调QPSK信号所容许的模式损耗偏离会随着其参考值的增加而增大,少模光纤通信系统中非线性补偿效果主要受限于模间非线性系数,其所容许的最大偏离为0.146 W-1·km-1。

Considering the influences of self-phase modulation and cross-phase modulation on the propagation characteristics of guided light in few-mode fibers, we present the analytic solution of the corresponding nonlinear coupled mode equation, which is used to calculate the nonlinear coefficients of few-mode fibers and analyze the nonlinear compensation in few-mode optical fiber communication systems. Taking four-phase phase shift keying(QPSK) signal systems which supports two linearly polarized(LP) modes as an example, the influences of mode loss and nonlinear effects on the mode division multiplexing system is analyzed by simulation, and the compensation effectiveness for inter-mode phase modulation and the adaptability of the compensation algorithm are also discussed in detail. Research results show that, for correct demodulation of QPSK signals after compensation, the maximum allowable misalignment of mode loss increases with the increasing reference value, and the nonlinear compensation effect in the few-mode optical fiber communication system is limited by the inter-mode nonlinear coefficient. The maximum allowable deviation of the inter-mode nonlinear coefficient is 0.146 W-1·km-1.