Microwave-based satellite–ground links are used to transfer time and frequency in various applications such as metrology, navigation, positioning, and very long baseline interferometers. The existing approaches, however, cannot fully satisfy the requirements of these applications. In this study, we investigated the possibility of an optical-based satellite–ground link, where the transferred carriers are pulsed lasers, resulting in a link with a high time resolution and a large ambiguous range. First, we analyzed the parameters of satellites in different orbits and concluded that high-orbit links enable more stable time–frequency comparison or dissemination by taking advantage of the long duration, a large common view range, and the lower relativistic effects. Subsequently, we performed a 16 km free-space transfer experiment to simulate links in the loss, noise, and delay effects. The link exhibits an instability of $4 \times {10^{- 18}}$ at 3,000 s and an approximately 10 fs time deviation with an average loss of 72 dB, corresponding to the loss of a satellite–ground link at geostationary earth orbit (GEO). Based on these results, we expect that the instability of the time–frequency transfer via a GEO link might reach ${10^{- 18}}$ at 10,000 s.

中文翻译：

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通过光学卫星-地面链路在10 ^-18不稳定下进行时间和频率传输的实验模拟

基于微波的卫星地面链路用于在各种应用中传输时间和频率，例如计量，导航，定位和超长基线干涉仪。但是，现有方法不能完全满足这些应用程序的要求。在这项研究中，我们研究了基于光学的卫星-地面链路的可能性，其中传输的载波是脉冲激光，从而导致了具有高时间分辨率和较大模糊范围的链路。首先，我们分析了不同轨道上的卫星参数，并得出结论，高轨道链路可以利用较长的持续时间，较大的公共视角范围和较低的相对论效应，实现更稳定的时频比较或传播。随后，我们进行了16 km的自由空间传递实验，以模拟损耗，噪声和延迟效应中的链接。链接显示不稳定$ 4乘以{10 ^ {-18}} $在3,000 s处出现约10 fs的时间偏差，平均损耗为72 dB，这对应于地球静止地球轨道（GEO）的卫星-地面链路的损耗。根据这些结果，我们预计，通过GEO链接进行时频传输的不稳定性可能会在10,000 s时达到$ {10 ^ {-18}} $。