Microwave transfer through optical frequency comb toward 10−19 instability using fiber-loop optical-microwave phase detectors

We demonstrate a remote microwave/RF transfer technique based on frequency comb. We use high resolution and low drift fiber-loop optical-microwave phase detectors (FLOM-PD) for fiber link stabilization and synchronization between a mode-locked laser and microwave sources. The demonstrated fractional frequency instability between 2.856-GHz oscillators separated by a 2.3-km fiber link is 7.6 × 10^-18 and 6.5 × 10^-19 at 1000 s and 82,500 s averaging time, respectively.