Humidity Sensor With a PVA-Coated Photonic Crystal Fiber Interferometer

A photonic crystal fiber (PCF)-model interferometer (MI)-based relative humidity (RH) sensor is proposed and experimentally demonstrated. The PCF-MI is formed by fusion splicing a short length of PCF between two single-mode fibers with the air holes of the PCF in the splicing regions being fully collapsed. It was then coated with a layer of polyvinyl alcohol by using a dip-coating process. Experimental results show that a high humidity sensitivity of 40.9 pm/%RH is achieved within a measurement range of 20-95%RH. The sensor also shows good repeatability and low temperature independence.