Extended Data Fig. 7: Traces for synchronization over 300 km for 4.0 mW of comb power at site B (left, blue traces) and for reduced, 40 μW comb power at site B (right, green curves).
From: Quantum-limited optical time transfer for future geosynchronous links
(a) Time trace of received power, Prec, measured at the output of the timing discriminator for site A with the applied threshold shown as a dashed black line. (b) The control effort, ΔTcntrl, applied on site B to maintain synchronization between the two site’s clock combs. As such, it is also a measurement of the time offset between the two cavity-stabilized reference lasers. (c) Changes in the time-of-flight. These changes are due to temperature drifts in the 300 km of air and in the fiber paths up to the terminals, atmospheric turbulence, and mechanical movement in the terminals. (d) The out-of-loop timing verification or ‘Truth’ data indicates constant temporal overlap between the clock combs at both sites despite 100’s of ps changes in the time-of-flight and 100’s of ns changes in ΔTcntrl. This truth data is used to generate the instability deviations of Fig. 3.
