Effect of soil temperature on one-way optical frequency transfer through dense-wavelength-division-multiplexing fibre links

TL;DR

This study models how soil temperature variations affect optical frequency transfer in dense-wavelength-division-multiplexing fibre links, demonstrating the stability of one-way optical frequency dissemination over such networks.

Contribution

It introduces a model linking soil temperature changes to frequency variations in optical fibres and validates it with real data, showing stable frequency transfer over long distances.

Findings

Soil temperature impacts on optical frequency are qualitatively consistent with measurements.

Optical frequency transfer remains stable enough for standard frequency standards over DWDM networks.

The model can predict link stability over extended periods.

Abstract

Results of optical frequency transfer over a carrier-grade dense-wavelength-division-multiplexing (DWDM) optical fibre network are presented. The relation between soil temperature changes on a buried optical fibre and frequency changes of an optical carrier through the fibre is modelled. Soil temperatures, measured at various depths by the Royal Netherlands Meteorology Institute (KNMI) are compared with observed frequency variations through this model. A comparison of a nine-day record of optical frequency measurements through the 2 x 298 km fibre link with soil temperature data shows qualitative agreement. A soil temperature model is used to predict the link stability over longer periods (days-months-years). We show that one-way optical frequency dissemination is sufficiently stable to distribute and compare e.g. rubidium frequency standards over standard DWDM optical fibre networks.