High resolution frequency standard dissemination via optical fiber metropolitan network

TLDR

The article introduces a new 100 MHz ultrastable reference signal dissemination system over a standard fiber network, with potential upgrades for future optical clocks. The system transfers the 100 MHz signal via amplitude modulation of an optical carrier and implements two noise‑compensation approaches, whose limits are analyzed and solutions proposed to enhance stability and extend distribution distance. The system enables high‑precision cold‑atom fountain comparisons up to 100 km, achieving a relative frequency resolution of 10⁻¹⁴ at 1 s and 10⁻¹⁷ after 1 day.

Abstract

We present in this article results on a new dissemination system of an ultrastable reference signal at 100MHz on a standard fiber network. The 100MHz signal is simply transferred by amplitude modulation of an optical carrier. Two different approaches for compensating the noise introduced by the link have been implemented. The limits of the two systems are analyzed and several solutions are suggested in order to improve the frequency stability and to further extend the distribution distance. Nevertheless, our system is a good tool for the best cold atom fountains comparison between laboratories, up to 100km, with a relative frequency resolution of 10−14 at 1s integration time and 10−17 for 1day of measurement. The distribution system may be upgraded to fulfill the stringent distribution requirements for the future optical clocks.