Optical fibre sensors utilizing evanescent wave interactions with a functional coating layer for the detection of liquid-phase vapours based on their evaporation temperatures

This article presents a novel approach to detecting liquid vapors by utilizing evanescent wave interactions with an active sensing environment based on a graphene oxide (GO) thin film. The study focuses on materials representing chemical warfare agents and irritant gases, including TMP, THX, and NH₄OH, whose vapors are adsorbed onto the GO layer, influencing light propagation in low-cost optical fibre sensors. The paper describes the fabrication of microfibres, surface activation, coating processes, and identification methods for specific vapors. Spectral analyses were performed in the 600 1800 nm range under varying evaporation temperatures. For each compound, characteristic wavelengths were identified, with NH₄OH demonstrating the highest sensitivity in peak shift (0.07 nm/°C) and TMP the lowest (0.03 nm/°C). After 30 minutes of exposure, the peak shift rate stabilized across all tested substances. Additionally, an increase in optical power over time confirms the accumulation of material on the microfiber surface and corresponding changes in light propagation conditions.