The long-term impact of different fluids on polymer-coated fibers in Rayleigh-based OFDR

The interaction between surrounding liquids and optical fibers with protective coatings immersed in them is investigated in this paper. The research aims to determine whether, and to what extent, the liquid impacts the properties of the fiber coatings. Using long-term spectral shift monitoring by Rayleigh backscattering optical frequency domain reflectometry (OFDR), the study examines how different coatings behave when exposed to different liquids, including water, acetone, ethanol, and methanol. These findings provide valuable insight into selecting appropriate optical fiber coatings, which could be used as sensors in various fluids. The results led to the determination of the stabilization period, after which the influence of the liquid on the coating - indirectly on the fiber - stabilizes, providing accurate and reliable measurements by Rayleigh-based OFDR. Spectral shifts in used fibers immersed in different liquids were observed at room temperature. Consequently, the strain effects (either compression or elongation), which originated from the interactions between the coating and the liquid, were thoroughly analyzed. The findings of this study are important for proper undisturbed measurement by Rayleigh-based OFDR when designing fiber sensor setups that work in different fluids.