Fig. 4
From: Free-space transfer of comb-rooted optical frequencies over an 18 km open-air link
Microwave signal transfer. a Microwave synthesis by heterodyning two optical carriers λt2 and λt3. Abbreviations are; OC: optical coupler, PD; photodetector, SMSR: side-mode-suppression ratio, SNR: signal-to-noise ratio. b Phase noise spectra of a 10 GHz microwave measured at Site A (black) in back-to-back configuration and at Site B (blue) after transmission over an 18 km free-space optical link. The reference optical signal (grey) is plotted by downscaling the uncompensated optical phase noise shown in Fig. 3b
