Optical frequency transmission over 251 km of fiber at 6x10-19 residual frequency instability in 100 s

B. de Beauvoir, F. Nez, Laurent Hilico +7 more

Nathan R. Newbury, Paul A. Williams, William C. Swann

We transfer an optical frequency over 251 km of optical fiber with a residual instability of 6x10(-19) at 100 s. This instability and the associated timing jitter are limited fundamentally by the noise on the optical fiber and the link length. We give a simple expression for calculating the achievable instability and jitter over a fiber link. Transfer of optical stability over this long distance requires a highly coherent optical source, provided here by a cw fiber laser locked to a high finesse optical cavity. A sufficient optical carrier signal is delivered to the remote fiber end by incorporating two-way, in-line erbium-doped fiber amplifiers to balance the 62 dB link loss.

Davide Calonico, Elio K. Bertacco, Claudio Eligio Calosso +10 more

Zhaolong Li, Sibo Gui, Haitao Wu +2 more

Optical clocks can be used as the absolute frequency reference due to their high accuracy and stability. In a precise optical clock transmission system, the instability loss of the link is usually evaluated by beating the remote optical signal with the reference clock, which is not suitable for real frequency distribution applications. Therefore, it is necessary to assess the performance directly at the remote site for the optical frequency transfer, because the two sites of the link are usually not co-located. In this paper, we proposed a comb-based remote residual instability evaluation scheme. Two coherent optical combs with different wavelengths were extracted from a frequency stable comb and transmitted after multiplexing. The residual instability was evaluated directly at the remote site by measuring the phase fluctuation difference between the two combs. We achieved 8.61 × 10−19 at 40,000 s over a 10 km fiber link, reaching the instability of optical clocks. These results revealed that our scheme can evaluate optical clock frequency transmission directly at the remote site, which made the method truly practical.

Predehl, Alnis, Hänsch +6 more

Paul A. Williams, William C. Swann, Nathan R. Newbury

We transmit a narrow-linewidth cw laser at 1535 nm across 38 km of installed fiber. Through standard Doppler-cancellation techniques, we achieve a residual fractional frequency instability of 4 times 10-17at 1 second averaging time.