Simultaneous remote transfer of accurate timing and optical frequency over a public fiber network

TL;DR

This paper demonstrates the first simultaneous transfer of ultra-stable optical frequency and precise timing over 540 km of public fiber network, achieving high accuracy and stability surpassing traditional methods.

Contribution

It introduces a novel method for concurrent optical frequency and timing transfer over existing telecommunication infrastructure using spread spectrum modulation.

Findings

Achieved 250 ps absolute time accuracy

Maintained 20 ps long-term timing stability

Successfully transferred signals over 540 km of public fiber

Abstract

In this work we demonstrate for the first time that it is possible to transfer simultaneously an ultra-stable optical frequency and a precise and accurate timing over 540 km using a public telecommunication optical fiber networks with Internet data. The optical phase is used to carry both the frequency information and the timestamps by modulating a very narrow optical carrier at 1.55 $\mu$m with spread spectrum signals using two-way satellite time transfer modems. The results in term of absolute time accuracy (250 ps) and long-term timing stability (20 ps) well outperform the conventional Global Navigation Satellite System or geostationary transfer methods.