Simultaneous Measurement of Temperature and Relative Humidity Based on FBG and FP Interferometer

In this letter, a simultaneous measurement system of temperature and relative humidity is proposed, which consists of a fiber Bragg grating (FBG) and Fabry-Perot (FP) interferometer. The FP interferometer was fabricated by splicing the hollow capillary with a single-mode fiber and the end of the hollow capillary was filled with a layer of polyimide, achieving a humidity sensitivity of 22.07 pm/%RH in the range of 20-90 %RH. FBG is insensitive to humidity, which can be used to measure temperature and eliminate the obstruction of temperature on FP humidity probe by formula conversion. The temperature sensitivity of FBG is 9.98 pm/°C. Due to low cost and good stability, this system has broad application prospects in the fields of food processing, medical care, and food storage.