Experimental simulation of time and frequency transfer via an optical satellite–ground link at 10-18 instability

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 × 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.