快速移动链路上的自由空间光频率比对
Free Space Optical Frequency Comparison Over Rapidly Moving Links
AI总结：
针对自由空间光链路中相对运动导致的多普勒效应限制光频率比对稳定性的问题，研究团队研发了采用10 GHz带宽电光相位调制器的系统，经无人机链路验证实现了高稳定度频率比对，为地对低轨光频率比对提供了可扩展地面测试基础。
摘要：
自由空间光链路上的光参考频率信号比对受本地站点与远端站点间相对运动的限制。对于地面对低地球轨道的比对，预期的多普勒频移和多普勒变化率在100 MHz/s的速率下通常可达4 GHz，这阻碍了实现最高稳定性光频率比对所需的窄带检测。我们展示了一种能在存在此类显著多普勒频移的情况下开展光频率比对的系统，该系统采用驱动带宽为10 GHz的电光相位调制器，将可实现地对空频率比对。该系统在回射式无人机链路上进行了验证，链路最大视线速度为15 m/s，多普勒频移为19 MHz，多普勒变化率为1 MHz/s。在5秒的积分时间下，获得的最佳分数频率稳定度为7E-18。这些结果是迈向地面对低地球轨道光频率比对的重要一步，提供了一个可扩展的地面测试平台。
英文摘要：
The comparison of optical reference frequency signals over free-space optical links is limited by the relative motion between local and remote sites. For ground to low earth orbit comparison, the expected Doppler shift and Doppler rate typically reach 4 GHz at 100 MHz/s, which prevents the narrow-band detection required to compare optical frequencies at the highest levels of stability. We demonstrate a system capable of optical frequency comparison in the presence of these significant Doppler shifts, using an electro-optic phase modulator with an actuation bandwidth of 10 GHz, which will enable ground-to-space frequency comparison. This system was demonstrated over a retro-reflected drone link, with a maximum line-of-sight velocity of 15 m/s and Doppler shift of 19 MHz at a Doppler rate of 1 MHz/s. The best fractional frequency stability obtained was 7E-18 at an integration time of 5s. These results are an important step toward ground to low earth orbit optical frequency comparison, providing a scalable terrestrial test bed.
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