Precise Radio Frequency Dissemination via Simulated 3000-km Fiber Re-Circulating Loop

In the long-haul fiber link, the phase noise introduced by erbium-doped fibers amplifiers (EDFAs) cannot be compensated. Its influence is very important and should be considered in long-haul fiber link frequency dissemination. In this letter, we disseminate a high-precision radio frequency signal to a simulated remote site over a long fiber link in the laboratory. The phase noise introduced by EDFA is analyzed. A fiber re-circulating loop with optical switch is constructed to test the performance of frequency dissemination system in the case of cascade using EDFAs. The system can obtain the phase error between the returned signal and the reference signal based on a 3000-km fiber re-circulating loop. The residual frequency instability after phase noise compensation reaches
$3.5 \times 10^{\mathrm {-13}}$
at 1 s and
$2.0 \times 10^{\mathrm {-15}}$
at 4000 s. Our method provides the basis for long-haul precision frequency dissemination and frequency synchronization between remote sites.