Abstract

Reliable distributed temperature sensing in high-temperature environments remains a significant challenge due to the thermal and mechanical limitations of conventional optical fibers. In particular, polymer-coated fibers degrade above ∼300 °C due to coating failure, mechanical fragility and hydrogen ingress. Metal-coated optical fibers offer a robust alternative for harsh environments such as Electric Arc Furnaces (EAFs), aerospace engines, nuclear systems, and oil and gas wells, owing to their superior mechanical strength and hermetic sealing. In this work, a first comprehensive experimental investigation of the thermo-mechanical behavior of metal-coated optical fibers for distributed high temperature sensing is presented over a wide temperature range from 25 °C to 700 °C, accompanied by validation through an industrial case study employing Rayleigh-based Optical Frequency Domain Reflectometry (OFDR). Copper (Cu)- and gold (Au)-coated fibers are systematically evaluated in terms of temperature sensitivity, hysteresis, long-term stability, and mechanical robustness, complemented by axial strain characterization and post-exposure surface morphological analysis. Distributed measurements during thermal cycling reveal pronounced coating-dependent behavior. Au-coated fibers exhibit stable, repeatable responses with minimal hysteresis, whereas Cu-coated fibers show significant hysteresis and sensitivity mismatch between heating and cooling. Long-term tests over 72 h further demonstrate temperature fluctuations up to ±3.5 °C in Cu-coated fibers, while Au-coated fibers maintain superior signal stability, attributed to enhanced hermeticity and resistance to oxidation. The practical relevance is validated through an industrial case study on early leak-onset detection in the refractory lining of an Electric Arc Furnaces (EAF) burner assembly, where real-time distributed thermal mapping enables clear localization of water ingress under operating temperatures approaching 600 °C. Overall, this study establishes a direct correlation between coating-dependent thermo-mechanical effects and distributed sensing accuracy, highlighting the performance differences between Au- and Cu-coated fibers. These findings provide critical design guidelines for deploying distributed fiber-optic sensors in high-temperature industrial environments.

Department(s)

Electrical and Computer Engineering

Second Department

Materials Science and Engineering

Publication Status

Full Text Access

Comments

Office of Energy Efficiency and Renewable Energy, Grant DEEE0009392

Keywords and Phrases

Distributed temperature sensing; Fiber optic sensors; High temperature sensing; Metal-coated fibers; Optical frequency domain reflectometer (OFDR); Rayleigh backscattering; Thermal mapping

International Standard Serial Number (ISSN)

0263-2241

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2026 Elsevier, All rights reserved.

Publication Date

01 Oct 2026

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