相干通信系统信道间非线性补偿算法研究

With the development of DSP technology, the coherent optical communication has recently become a hot topic again. When the signal light propagating in the fiber simultaneously affected by chromatic dispersion and nonlinear effects, resulting in signal impairments. These impairments limiting further enhance transmission capacity. Thus, mitigate or compensate for these impairments are a fiber optic communication research important part. By coherently receiving the optical signal amplitude information, digital backward propagation (DBP) method can be utilized to achieve the purpose of compensating for signal impairments. However DBP method, especially in WDM systems, need a huge amount of calculation. So, how to reduce the computational burden is a key issue of nonlinear compensation. DBP method base on solving nonlinear Schrödinger equation. The most effective method is the split-step Fourier method. It is inversely proportional to the step size computing needs. For WDM system, through abandoned FWM negligible part, step size limit can be relaxed to walk-off length. Through explicitly computing the walk-off effect, the step size restrictions can be relaxed to the dispersion length. The project is planned on researching the inter-channel nonlinear interaction using the perturbation theory and using this formula to design inter-channel nonlinear compensation algorithm. The step size of this algorithm can break through the restrictions of dispersion length. The computational burden can be relaxed by one order of magnitude.

随着数字信号处理（DSP）技术的发展，相干光通信近来再次成为了研究热点。信号光在光纤中传播时同时受到色散和非线性作用的影响，造成信号损伤,限制了传输容量。减轻或补偿这些损伤是光纤通信研究中的一个重要的组成部分。可以利用后向数字传播（DBP）方法通过计算对信号进行反演，对信号损伤进行补偿。但是DBP方法，尤其是在WDM系统中，计算量巨大，目前难以承受。所以，如何通过算法改进减少计算负担成为了目前相干光通信非线性补偿研究中的关键和核心问题。DBP方法基于解非线性薛定谔方程，目前最有效的方法是分步傅立叶方法。它的计算复杂度反比于计算步长。对于WDM系统，目前最先进的走离算法可以将步长的限制放宽到色散长度。本项目拟在此基础上，利用微扰理论研究信道间非线性相互作用，推导非线性相移计算公式，并据此设计新型的信道间非线性补偿算法。算法的步长可以突破色散长度的限制，有望将计算复杂度降低一个数量级。