Fig. 1: Frequency comb-to-comb stabilization over a 1.3 km free-space optical link.
From: Frequency comb-to-comb stabilization over a 1.3-km free-space atmospheric optical link
a Overall system configuration. The master comb is located at Site A in stabilization to a high-finesse optical cavity. A slave comb to be stabilized is placed at Site B. Two optical frequencies ν1 (1531 nm) and ν2 (1564 nm) are extracted from the master comb at Site A, transferred to Site B through a free-space optical link. b Time-dependent power fluctuation of the optical carrier signals received by the transceivers; T1 at Site A and T2 at Site B. Grey line at bottom denotes the calculated power difference between T1 and T2. c, d Linewidths of the transferred optical frequencies ν1 and ν2, respectively, at Site B with phase noise suppression control. e Single sideband (SSB) phase noise spectra of forward path (one-way) and feedback (two-way) optical carrier signals. WDM Wavelength division multiplexer, AOM Acousto-optic modulator, C Circulator, EDFA Erbium-doped fiber amplifier, OC Optical coupler, PD Photodetector, T Transceiver, M Flat mirror, and PLL Phase-locked loop
