Residual timing jitter in the free-space optical two-way time and frequency transfer caused by atmospheric turbulence

Abstract

Free-space optical two-way time and frequency transfer (FSO-TWTFT) will play an important role in the establishment of optical clock network, enabling the improvement of communication and navigation. In this paper, the model of residual timing jitter caused by the atmospheric turbulence is built for the FSO-TWTFT, where the spatial and temporal turbulence variation are both considered. The power spectrum density (PSD) of the residual timing jitter is derived and verified by comparing with the reported experimental results. The impacts of atmospheric turbulence on the comb-based FSO-TWTFT technique and the FSO-based optical frequency transfer technique are further analyzed for the satellite-to-ground links. The PSD at different satellite heights and elevation angles are presented. The results show the influence of temporal turbulence variation will be higher than that of spatial turbulence variation when the satellite is over 2000 km due to the large link delay. The residual timing jitters of the two FSO-TWTFT techniques are less than 6.4 fs in most orbit zones under medium turbulence intensity. In particular, for the comb-based FSO-TWTFT technique, there is a special orbit zone where the Doppler frequency shift approaches the repetition frequency difference of linear optical sampling and then the residual timing jitter increases dramatically.