Highly Sensitive Optical Fiber Humidity Sensor Employing SiO₂ Coated ZnO Nanoparticle Doped PVA

This letter describes the development and characterization of an optical fiber humidity sensor employing intensity modulation via evanescent wave (EW) absorption technique. For the development of the sensor, humidity-sensitive SiO2-coated ZnO nanoparticle doped PVA film was synthesized over the centrally decladded plastic cladding silica (PCS) fiber. In order to achieve optimal response, rigorous experimental investigations were conducted by varying the film thickness and composition. The optimized sensing probe demonstrated a linear response over 45.5-94.4% RH, with a linear sensitivity of 0.0137RH−1 (47.6mV/%RH). The response and recovery times were observed to be 1s and 1.25s during humidification and dehumidification, respectively. Additionally, the proposed sensor demonstrates a very high degree of repeatability, reversibility, and stability.