PVAc based SCMS optical fiber humidity sensor and its application in transformer oil

This paper presents a novel design of an optical fiber sensor (OFS) utilizing a single-mode-coreless-multimodesingle-mode (SCMS) fiber coated with Poly-Vinyl Acetate (PVAc) for humidity and moisture detection. PVAc, a highly sensitive synthetic polymer, exhibits changes in refractive index (RI) based on relative humidity (RH) variations in the surrounding medium, thereby affecting the output power of SCMS. Numerical analysis using COMSOL Multiphysics determined the optimal coating thickness. The fabricated PVAc-coated SCMS sensor enables RH measurement in air and moisture measurement in oil. The sensor demonstrated a sensitivity of 0.19 dBm/%RH and 0.16 dBm/%RH for increasing and decreasing humidity rates, respectively, within an RH range of 60-85% in air media. Additionally, the sensor achieved a sensitivity of 0.15 dBm/ppm for moisture measurement in oil media.