自由空间远程高精度相干光频率传递关键技术研究

In recent years, the uncertainty and stability of the optical clock have achieved the order of magnitude of E-18 and usually have been distributed in different places. In order to verify their performance indicators or use the existing optical clock to produce the UTC, it is necessary to study the remote frequency transfer method which is superior to the order of magnitude of E-19. At present, the frequency stability is lower than 1E-16/ day with traditional two-way satellite time and frequency transfer technology. The time and frequency transfer technology based on optical fiber can meet the requirements of optical clock time and frequency comparison in only about the order of magnitude hundreds of kilometers. Neither of methods can solve the remote intercontinental comparison between optical clocks..The aim of the project is to achieve the intercontinental time and frequency comparison between optical clocks. A method of coherent optical frequency transfer over free space is proposed. The theory and experimental research of coherent optical frequency transfer over free space is carried out. The effect of theory of relativity, Doppler Shift on the frequency transfer is explored. The mechanism and characteristics of link errors are researched. The mechanism of phase noise compensation at sender is explored to achieve real-time phase noise compensation. It provides theoretical and technical support for the research, development and construction of the global optical clock remote comparison and space-based space-time reference in China.

近年来，光钟的不确定度和稳定度均达到E-18量级，且通常异地分布。为验证它们的性能指标，以及利用现有光钟产生协调世界时，必须研究优于E-19量级的远程频率传递方法。目前，传统的卫星双向时间频率传递技术的频率稳定度低于1E-16/天，光纤时频传递技术仅在百公里量级满足光钟时频比对的要求，这两种方法都无法解决远距离跨洲际光钟之间的比对。.本项目以实现跨洲际光钟时频比对为目标，提出自由空间相干光频率传递方法，开展自由空间相干光频率传递的理论和实验研究；探索相对论、多普勒频移等对频率传递的影响，研究链路误差产生机理及其特性，探索发送端相位噪声补偿机理，实现实时相位噪声补偿。为全球光钟远程比对和我国天基时空基准的研究、发展与建设提供理论与技术支撑。

针对高精度光学频率远程比对需求，研究了地球空间相对论框架下的超高精度时频传递理论模型与方法，得出了相对论对时频传递的影响量级，以及相应的相对论误差修正方法。开展空间激光传输信道误差产生机理、多普勒频移误差补偿机理研究，建立了大气湍流误差计算模型，提出了基于主动相位噪声补偿的星间频率传递系统及方法，攻克了相干光频率传递相位噪声补偿和大范围快速可调谐相干接收等关键技术。在理论研究的基础上，搭建了地面相干光频率传递演示验证系统，在100米自由空间链路上，频率传递稳定度达到9.67E-16@1s，4.7E-16@10s。该方法能够为国家综合PNT体系、跨洲际光钟比对提供支撑。