Remote transfer of a high-stability and ultralow-jitter timing signal

Transfer of a high-stability and ultralow-jitter timing signal through a fiber network via a mode-locked fiber laser is demonstrated. With active cancellation of the fiber-transmission noise, the fractional instability for transfer of a radio-frequency signal through a 6.9- s4.5-d km round-trip installed (laboratory-based) fiber network is below 9(7) ×10⁻¹⁵ τ^−1/2 for an averaging time ≥1 s, limited by the noise floor of the frequencycounting system. The noise cancellation reduces the rms timing jitter, integrated over a bandwidth from 1 Hz to 100 kHz, to 37 (20) fs for the installed (laboratory-based) fiber network, representing what is to our knowledge the lowest reported jitter for transfer of a timing signal over kilometer-scale distances using an installed (laboratory-based) optical-fiber network.