基于光电振荡器的低相位噪声微波信号远距离稳相传输技术研究

The technology of microwave signal transmission over long-distance fiber with high stability has been widely used in many fields, such as deep space detection and remote clock synchronization field. Generally, in engineering applications, fiber-optic lines generally range from a few kilometers to hundreds of kilometers. Long-distance transmissions exacerbate the randomness of changes in the external environment of the fiber, and the deterioration of signal phase information with the transmission distance. The method of isolating the optical fiber from the external environment is obviously difficult and costly. Therefore, how to solve the problem is to maintain the signal without changing the influence of the external environment of fiber and causing no interference to the signal in the existing optical link. The phase stability problem has become an important task in the field of research in recent years..Based on the full investigation of the existing phase steady report for microwave signals over long-distance fiber , this project proposes a steady-state transmission scheme for long-range microwave signals based on OEO. The scheme transmits the microwave signal with the opposite phase information through the OEO fiber link, and mixes the signal transmitted in the forward direction at the far end of the link to compensate the phase jitter introduced in the forward signal transmission.

微波信号通过光纤进行远距离稳频稳相传输的技术在诸多领域有着广泛的应用，如深空探测、远程时钟同步等系统。通常，在工程应用中，光纤线路一般从几千米到几百千米不等，长距离传输更加剧了光纤外部环境变化的随机性，以及信号相位信息恶化随传输距离的积累。通过隔离光纤与外界环境的办法显然难度大、成本高，因此，在不改变外部环境对光纤的影响下，并对已有光通信链路中信号不造成任何干扰的情况下，保持系统远端信号的相位稳定是该领域研究的重要任务，也是近年来学者们研究的热点。.本项目在充分调研国内外现有微波信号远距离稳相方法的基础上，拟提出一种基于光电振荡器（OEO）的远距离微波信号稳相传输方案。该方案通过OEO光纤链路反向传输带有相反误差相位信息的微波信号，在链路远端与正向传输的信号进行混频，从而补偿正向信号传输中引入的相位抖动。

光纤信号传输系统容易受到环境温度和机械振动的影响，传输的微波信号被引入时延和相位波动，进而降低远端站点接收信号的频率稳定性。本项目针对该问题展开研究。研究了微波信号光纤传输的基本理论、影响因素和系统频率稳定性评估指标。然后提出了使用具有高Q值、低相位噪声的光电振荡器（OEO）来改善传输系统的相位噪声，结合被动相位补偿技术实现微波信号稳相传输。最后提出使用全光信号处理技术结合注入锁定OEO，实现了毫米波本振信号的稳相传输，并验证了高阶调制信号在该系统上分发的可行性。本项目的主要工作为：.1. 根据光电振荡器OEO的开/闭环模型分析其相位噪声特性，改善OEO相位噪声水平。结合注入锁定原理，实验实现了6 km光纤环路OEO在X全波段上的稳定单模振荡，边模抑制比达到70dB，且相噪达到-75dBc/Hz@10Hz和-140dBc/Hz@10kHz。.2. 提出了一种基于注入锁定光电振荡器的信号远距离传输稳相系统。引入OEO作为高质量、低相噪的本振微波信号源，同时复用OEO的长光纤环作为微波信号分发的环网。结合无源相位补偿原理和注入锁定OEO，该方案能够适用于更高频段、更大带宽、更低相位噪声的微波信号传输。实验实现了10.8 GHz微波信号在6.8 km光纤环网上的任意节点分发。相位噪声达到-110dBc/Hz@10kHz，远端站接收信号频率稳定度为3.8×10−14/1s和2.3×10−17/10000s。.3.提出了一种基于光电振荡器的全光微波信号远距离传输稳相系统。采用全光信号处理方案代替射频混频器，将微波相位共轭操作从电域搬移到光域上，突破了电器件的带宽限制和非线性问题。实验实现了36 GHz毫米波本振信号在6 km光纤环网上的稳相传输。相位噪声达到-130dBc/Hz@10kHz，远端站接收信号频率稳定度为1.069×10-14/1s和3.3×10-16/1000s。