Optical fiber humidity sensor based on the direct response of the polyimide film

An optical fiber humidity sensor based on an optical Fabry-Perot interferometer is proposed and experimentally demonstrated. The sensor is constructed by a short section of hollow-core fiber coated with a polyimide (PI) film. Taking advantage of the direct response of the PI film, a sensitivity of up to 1.309 nm/% RH can be achieved in the humidity change range from 40% RH to 80% RH. The temperature sensitivity is measured to be 43.57 pm/degrees C when the temperature changes from 25 degrees C to 55 degrees C. Because of its simple structure, fast response time, convenient production, and good reproducibility, the proposed sensor will be competitive in the field of cultural relic humidity monitoring and pharmaceutical storage. (C) 2018 Optical Society of America