An optical fiber humidity sensor based on optical absorption

A simple optical fiber relative humidity (RH) sensor was proposed and demonstrated. The humidity sensor was fabricated by coating moisture-sensitive film on the end face of a multi-mode optical fiber. The film was synthesized by doping CoCl
₂
into a PVA/SiO
₂
composite solution. Based on an optical absorption technique, the sensor head was characterized. From the optical absorption, a relative humidity range of 25%~65% was detected. Furthermore, the sensor has good repetitive response, and the response time was less than 2 min.