Dual-parameter optical fiber sensor for temperature and humidity based on PMMA-microsphere and FBG composite structure

Abstract

In this work, we proposed and experimentally demonstrated an optical fiber temperature and humidity sensor composed of a polymethyl methacrylate (PMMA)-microsphere and a fiber Bragg grating (FBG), and realize monitoring the environment temperature and humidity simultaneously. The experimental results show that when the relative humidity (RH) change from 35% to 85%, the response sensitivity of the Fabry-Pérot (F-P), which is formed between PMMA-microsphere and the fiber end-face, is about 127 pm/%RH. However, the FBG in the structure is not sensitive to humidity. When temperature changes from 33 °C to 58 °C, the response sensitivity of the F-P and FBG are about 45.68 pm/°C and 10 pm/°C, respectively. When temperature and humidity change simultaneously, these two-parameters can be monitored simultaneously by using the dual-parameter measurement matrix method. The optical fiber dual-parameter sensor offers numerous advantages, such as low cost, high sensitivity, and easy fabrication.