Frequency stability and phase noise measurements of a 5,860 km-long intercontinental seafloor optical fibre cable

TL;DR

This paper reports the first measurements of frequency stability and phase noise over a 5,860 km intercontinental seafloor optical fibre, demonstrating the challenges of ultra-stable frequency transfer across oceans for global clock comparisons.

Contribution

It provides the first-ever measurements of an intercontinental optical fibre link's frequency stability and phase noise, advancing the understanding of long-distance optical frequency transfer.

Findings

First measurements of an intercontinental optical fibre link.

Identified challenges in frequency stability over transoceanic distances.

Paved the way for future global clock comparison techniques.

Abstract

Optical clock comparison via optical fibre links has been achieved over continental scales, but has not yet been demonstrated intercontinentally. The transfer of ultra-stable optical frequencies over transoceanic distances is a challenging task, as the seafloor cable architecture prevents the use of environmental noise suppression techniques currently employed on land-based metrological links. As a fundamental first step towards devising suitable frequency transfer techniques to enable future clock comparison on a global scale, here we show the free-running frequency stability and phase noise measurements of a transatlantic seafloor optical link between the UK and Canada. To the best of our knowledge, these are the first ever measurements of an intercontinental optical fibre link.