86-km optical link with a resolution of 2.10-18 for RF frequency transfer

TL;DR

This paper demonstrates ultra-precise RF frequency transfer over 86 km of urban fiber with a resolution of 2.10^-18, utilizing optical compensation and polarization scrambling, and explores extended link performance over 186 km.

Contribution

It introduces a novel optical compensation method with polarization scrambling for high-resolution RF transfer over long-distance fiber links.

Findings

Achieved 2.10^-18 resolution over 86 km fiber

Extended link over 186 km with resolution below 10^-17

Analyzed limitations due to fiber dispersion and laser fluctuations

Abstract

RF frequency transfer over an urban 86 km fibre has been demonstrated with a resolution of 2.10-18 at one day measuring time using an optical compensator. This result is obtained with a reference carrier frequency of 1 GHz, and a rapid scrambling of the polarisation state of the input light in order to reduce the sensitivity to the polarisation mode dispersion in the fibre. The limitation due to the fibre chromatic dispersion associated with the laser frequency fluctuations is highlighted and analyzed. A preliminary test of an extended compensated link over 186 km using optical amplifiers gives a resolution below 10-17 at 1 day.