Swelling-Based Distributed Chemical Sensing with Standard Acrylate Coated Optical Fibers

Sina Sedighi,Dorel Dorobantu,Dominik Ziegler,Marius Enachescu,Alin Jderu,Marcelo A Soto

doi:10.3390/s21030718

Abstract

Distributed chemical sensing is demonstrated using standard acrylate coated optical fibers. Swelling of the polymer coating induces strain in the fiber’s silica core provoking a local refractive index change which is detectable all along an optical fiber by advanced distributed sensing techniques. Thermal effects can be discriminated from strain using uncoated fiber segments, leading to more accurate strain readings. The concept has been validated by measuring strain responses of various aqueous and organic solvents and different chain length alkanes and blends thereof. Although demonstrated on a short range of two meters using optical frequency-domain reflectometry, the technique can be applied to many kilometer-long fiber installations. Low-cost and insensitive to corrosion and electromagnetic radiation, along with the possibility to interrogate thousands of independent measurement points along a single optical fiber, this novel technique is likely to find applications in environmental monitoring, food analysis, agriculture, water quality monitoring, or medical diagnostics.

Highlights

Accepted: 18 January 2021With nearly two billion kilometers deployed around the world, optical fibers are the backbone of today’s telecommunications networks
Among the many different sensing approaches that have evolved over the last decades, distributed optical fiber sensors have gained attention due to their unique ability to provide longitudinally distributed measurements of physical variables, such as temperature or strain [2]
optical time-domain reflectometry (OTDR) is commonly used over long distances; it offers limited spatial resolution

Summary

Introduction

With nearly two billion kilometers deployed around the world, optical fibers are the backbone of today’s telecommunications networks. The interrogating systems typically use optical frequency-domain reflectometry (OFDR) or optical time-domain reflectometry (OTDR) to obtain spatially resolved information about the measurand Among these techniques, OTDR is commonly used over long distances (e.g., tens of kilometers); it offers limited spatial resolution. OFDR achieves very high spatial resolution (millimeter length scale), yet the sensing distance is limited to a few tens of meters. These technologies primarily measure temperature and strain changes [2]; there has been a recent interest in expanding the number of physical variables that a Published: 21 January 2021

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Conclusion