Phase fluctuation compensation for long-term transfer of stable radio frequency over fiber link

We developed a new radio frequency dissemination system based on an optical fiber link. A 1.55 μm mode-locked fiber laser was used as optical transmitter in the system. To actively reduce the phase fluctuation induced by the fiber length variations with high resolution, we proposed a novel compensation technique. In our technique, we directly control the phase of optical pulses generated by the laser to compensate the fluctuation. The phase-controlling method is based on both pump power modulation and cavity length adjusting. We performed the transfer in a 22-km outdoor fiber link, with a transfer stability of 3.7 × 10(-14) at 1 s and 6.6 × 10(-18) at 16000 s. The integrated timing jitter in 24 hours was reduced from 14 ps to 35 fs.