面向高速光纤传输的网格正交频分复用理论及相关技术研究

Through identifying the evolutionary status of optical fiber transmission system driven by massive amounts of information, we proposed the original thoughts about the joint management of time-frequency plane for multi-carrier optical communication systems. The focus of this research will be on the modulation/demodulation principles of optical lattice orthogonal frequency-division multiplexing (LOFDM) and its applications for high-speed optical fiber transmission, including the generation, transmission and modeling of optical LOFDM signal, the design and optimization of time-frequency plane matched with optical fiber channel, the novel nonlinear mitigation scheme based on the joint management of time-frequency plane and the digital signal processing for optical LOFDM system. Based on the existing theory of multi-carrier optical fiber transmission, specific objectives of this project will focus on resolving two important research questions, which are the optimal structures of time-frequency plane matched with optical fiber channel and the optical lattice orthogonal frequency-division multiplexing with high nonlinear tolerance. From the viewpoint of disciplinary crossing and integration, this research introduced the lattice orthogonal frequency-division multiplexing into optical fiber transmission system and deeply explored its potential, the intricate interactions between the physical impairments are also considered. The research work of this project will provide theoretical and technical supporting for the development of the future multi-carrier optical communication systems.

从分析海量信息驱动下未来光纤传输系统的演进趋势入手，提出将光纤信道适应性列为多载波系统的核心特征，基于时频网格联合管控思想，重点研究光网格正交频分复用信号的调制/解调原理及其在光纤信道中高速传输的关键技术，包括：光网格正交频分复用信号的产生、传输及建模；与光纤信道相匹配的时频网格设计及优化；基于时频网格联合管控的非线性损伤补偿方法；光网格正交频分复用系统的数字信号处理算法等内容。立足现有多载波光纤传输理论，解决能够与光纤信道相匹配的载波时频网格结构的设计与优化、满足低非线性损伤要求的光网格正交频分复用传输系统建模与仿真两类关键科学问题。突出学科交叉，将网格正交频分复用概念扩展至光传输领域并进一步深化，综合考虑信号在光纤信道中传输时由于多种物理损伤相互耦合而引入的复杂机理，为研发下一代多载波光纤通信系统提供科学支撑。

由于网络数据流量的海量增长、千亿移动设备的连接和业务需求的多样化，光纤通信技术面临严峻挑战。工业界和学术界一致认为下一代光纤通信系统中一个非常具有竞争力的技术方案是光网格正交频分复用。本项目重点研究了光网格正交频分复用系统的以下三项关键技术：光信号的调制/解调原理、高速光纤传输激发的物理损伤机理和损伤抑制补偿方法。项目组通过分析矩形和六角时频网格正交频分复用系统的信号生成过程，设计了适合光纤信道传输的调制/解调方法；建立了网格正交频分复用信号的光纤传输模型，该模型包含了各种信道噪声和非线性串扰、不同时频网格下的固有虚部干扰、频率偏移等复杂效应对光信号传输过程的影响；搭建了相干光网格正交频分复用系统的数值仿真平台，可以对上述损伤机理及其补偿方法进行详细分析，实现矩形和六角时频网格系统传输性能的仿真研究，具有广泛的应用性。在此基础上，我们提出了相干光网格正交频分复用系统的信道和频偏联合估计方法，该方法借助于不同帧之间的频域平均操作，获取频偏和信道响应的估计值，在线性和非线性光纤传输场景下分别验证了该方法的有效性；提出了OFDM-ROF系统的毫米波信号光学生成方法，该方法利用三并联马赫-曾德尔干涉仪生成高质量的40 GHz和80 GHz毫米波信号；针对传统光正交频分复用系统具有过高峰均比的缺陷，提出了基于脉冲成型的子载波幺正扩展方法，能够减小不同子载波之间的波形叠加，有效降低时域信号的PAPR，该方法也适用于六角时频网格系统。此外，项目组还研究了单轴晶体包层光纤的非线性效应，提出了调控非线性效应的有效途径；研究了单模光纤的受激布里渊散射过程，详细分析了该非线性效应影响下光脉冲的传输过程和损伤机理。相关研究已发表SCI论文8篇，EI期刊论文11篇，已授权实用新型专利2项，新申请发明专利和实用新型专利各1项，已培养硕士研究生4名，取得的成果能够为光网格正交频分复用技术的发展提供有益科学参考。