Active Propagation Delay Stabilization for Fiber-Optic Frequency Distribution Using Controlled Electronic Delay Lines

In this paper, we present the novel method of stabilizing the propagation delay in the fiber-optic link using two matched electronic delay lines. For this purpose, we developed a dedicated integrated circuit using Austria Mikro Systeme 0.35-μm CMOS process. Two transmission links were tested at two independent laboratories, operating at different distances (20 and 60 km, respectively) and using slightly different setups. Both links show the Allan deviation of about 2 × 10^-17 after 1-d averaging and residual fluctuations of the propagation delay of around 12 ps peak to peak. The obtained results show that such systems are suitable for distributing the signals from hydrogen masers or cesium clocks at the distances spanning tens of kilometers.