Novel Polarization Control Approach to Long-Term Fiber-Optic Frequency Transfer
Dong-Jie Wang1,2,3, Xiang Zhang1,2,3, Jie Liu1,3, Dong-Dong Jiao1,2,3, Xue Deng1,2,3, Jing Gao1,2,3, Qi Zang1,2,3, Dan Wang1,3, Tao Liu1,2,3*, Rui-Fang Dong1,2,3, and Shou-Gang Zhang1,2,3
1National Time Service Center, Chinese Academy of Sciences, Xi'an 710600, China 2University of Chinese Academy of Sciences, Beijing 100049, China 3Key Laboratory of Time and Frequency Standards, Chinese Academy of Sciences, Xi'an 710600, China
Abstract：We demonstrate a novel polarization control system based on a gradient descent algorithm, applied to a 450-km optical frequency transfer link. The power of the out-loop beat note is retrieved by controlling the polarization state of the transferred signal, with a recovery time of 24 ms, thereby ensuring the long-term evaluation of the fiber link. As a result, data utilization is enhanced from 70% to 99% over a continuous measurement period of $\sim$12 h. A fractional transfer instability of $7.2 \times 10^{-20}$ is achieved at an integration time of 10000 s. This work lays the foundation for the comparison of a remote optical clock system via a long-haul optical fiber link.
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2020, Vol. 37 
