Validation of Kepler Time and Frequency Transfer on a Terrestrial Range of 10.45km

Kurzfassung

A bi-directional optical link is established over 10.45 km to perform Two-Way Frequency and Time Transfer (TWFT, TWTT) to validate the system design for Lower Earth Orbit (LEO) to ground links through the atmospheric channel. Binary phase shift keying with a homodyne reception scheme is used to recover the carrier frequency. The time transfer is enabled by optical correlation and dynamic tracking of a 25.6 Gcps transmission spread-sequence with a locally generated reference sequence. An additional data transmission of 50 Mbps is performed on the same channel. Optical references and frequency combs on both sides enable the frequency measurements. Ultra-stable oscillators generate Radio Frequency (RF) references for the time transfer. The performance of the system is evaluated under different atmospheric conditions. Frequency transfer with a stability of 5 · 10^?15 at 1 s gate time. Simultaneous two-way time transfer with a stability of 1 · 10^?13 at 1 s gate time prove the feasibility of the system even through the atmospheric channel.