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 ∼12 h. A fractional transfer instability of 7.2 × 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.

中文翻译：

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长期光纤频率传输的新型偏振控制方法

我们演示了一种基于梯度下降算法的新型偏振控制系统，该系统已应用于450公里的光频传输链路。通过控制传输信号的偏振状态来恢复跳动音符的功率，恢复时间为24 ms，从而确保了对光纤链路的长期评估。结果，在约12小时的连续测量时间内，数据利用率从70％提高到99％。积分时间为10000 s时，传输不稳定性为7.2×10 -20。这项工作为通过远程光纤链路比较远程光学时钟系统奠定了基础。