Two-Way Time and Frequency Transfer via Ground-to-Satellite Optical Communications Links

Future global clock networks will require time and frequency transfer links capable of spanning intercontinental distances and supporting the stability of state-of-the-art frequency standards. Improved Two-Way Satellite Time and Frequency Transfer (TWSTFT) will be essential to support precision atomic references in orbit, as well as direct comparison of clocks at standards labs around the world. In this work we propose leveraging high data rate satellite optical communications links for precision time and frequency transfer by locking the communications symbol clock and optical carrier phase to an atomic reference using a femtosecond comb. We describe how the time, frequency, and phase measurements made by modern optical communications systems can be used to achieve link timing uncertainties TDEV at 10(-14) tau(-1/2) using the GHz symbol clock, and frequency uncertainty MDEV at 10(-17) tau(-3/2) supported by tracking the optical carrier phase over an orbit.