高速短距离光传输中非线性估计与信号均衡

The proliferation of bandwidth demands and multiple Internet services has driven the short reach optical transmissions to higher data rate and lower cost. The signal with high baud rate and high modulation order in high speed short reach optical transmission is seriously affected by the nonlinearity. The project aims to explore the distortion mechanism of short reach optical transmissions, establish a linear and nonlinear response model based on Volterra series theory in the time domain and frequency domain respectively. Based on the linear equalization in the time domain, the project proposes a nonlinear equalization with low complexity in the time-domain besides the novel adaptive algorithms, using the advanced digital signal processing. A novel nonlinear equalization mechanism in the frequency domain is also presented, offering a low cost way to improve the tolerance to system’s nonlinearity for the frequency modulation. The project also proposes a pre-equalization scheme using a pseudo noise sequence to estimate the linear channel response. A hybrid equalization is given to further improve the short reach optical system by combining the proposed pre-equalization and the nonlinear post-equalization. The project reveals the method of model establishment and equalization for nonlinear distortion in the low cost and high speed short reach optical transmissions, and provides an effective way to estimate and compensate the nonlinear distortion, which has significance both in theory and practice.

日益增长的带宽需求和多元化互联网服务推动着短距离光传输快速发展，目标是实现高速和低成本的信号传输。高速短距离光传输系统中高波特率和高阶调制信号受到系统非线性的影响严重，本项目探索短距离光传输系统中非线性损伤机理，基于Volterra级数理论建立系统非线性响应时域和频域模型，利用先进的数字信号处理技术，在线性时域均衡的基础上，提出低复杂度的非线性时域均衡方案及自适应算法，并建立新型的频域非线性均衡机制，为频域调制技术的低成本非线性均衡奠定基础。项目同时研究利用伪噪声序列估计信道线性响应的预均衡方案，并结合后端非线性补偿形成联合均衡机制，进一步提升系统的传输性能。本项目揭示低成本高速短距离光传输系统非线性损伤建模方法和均衡机理，为实现系统非线性估计和补偿提供有效手段，具有重要的理论和实际意义。

短距离光接入、互连和无线融合传输应用是未来重要的发展和研究领域。400Gb/s乃至1Tb/s的高速传输成为研究的主要目标。最可能采用的是先进的调制格式来提高频谱效率，直接探测技术来简化系统结构，以及低成本的光源等。本项目探索短距离光传输系统中非线性损伤机理，基于Volterra级数理论建立系统非线性响应时域和频域模型，提出了三种低复杂度的非线性时域均衡算法、新型的频域非线性均衡算法和基于神经网络的非线性补偿方案。项目同时研究了利用伪噪声序列估计信道线性响应的预均衡方案，验证了基于PN序列实现线性信道估计可进一步提升系统的传输性能。最后本项目搭建了脉冲幅度调制（PAM）、无载波幅相调制（CAP）、离散多音调制（DMT）等通用短距离仿真和实验系统，对提出的新型理论、算法进行了可行性验证，提出并实验实现了400Gb/s的低成本短距离传输方案。本项目提出的低成本高速短距离光传输系统非线性损伤建模方法和均衡机理，为实现系统非线性估计和补偿提供了有效手段，具有重要的理论和实际意义。