Linking distributed and integrated fiber-optic sensing

TL;DR

This paper compares distributed acoustic sensing and integrated fiber-optic sensing systems, analyzing their sensitivities and demonstrating a first quantitative comparison using real telecommunications fibers in Athens.

Contribution

It provides a theoretical framework for comparing DAS and integrated systems and presents the first direct experimental comparison using existing telecom fibers.

Findings

Sensitivity depends strongly on fiber curvature points

First quantitative comparison between DAS and MFFI systems

Demonstrated feasibility of using existing telecom fibers for sensing

Abstract

Distributed Acoustic Sensing (DAS) has become a popular method of observing seismic wavefields: backscattered pulses of light reveal strains or strain-rates at any location along a fiber-optic cable. In contrast, a few newer systems transmit light through a cable and collect integrated phase delays over the entire cable, such as the Microwave Frequency Fiber Interferometer (MFFI). These integrated systems can be deployed over significantly longer distances, may be used in conjunction with live telecommunications, and can be significantly cheaper. However, they provide only a single time series representing strain over the entire length of fiber. This work discusses theoretically how a distributed and integrated system can be quantitatively compared, and we note that the sensitivity depends strongly on points of curvature. Importantly, this work presents the first results of a quantitative, head-to-head comparison of a DAS and the integrated MFFI system using pre-existing telecommunications fibers in Athens, Greece.