LAUSR

Abstract Based on the coupled mode theory of the fiber grating, a novel cascaded grating sensor with film-modified long period fiber grating (LPFG) and fiber Bragg grating (FBG) is designed. The sensing principles are investigated, and the temperature and humidity sensing experiments are carried out. The experimental results show that LPFG and FBG have different response sensitivities to the temperature and humidity, and the temperature sensitivities are 34.99 and 8.65 pm·℃−1, respectively. The humidity sensitivity of LPFG is 94.34 pm·%RH-1 while FBG is insensitive to the humidity. Therefore, the simultaneous monitoring of environmental temperature and humidity is realized by using the sensitivity matrix. The minimum resolutions of the sensor for temperature and humidity are ±2.312 °C and ±1.069%RH, respectively. Given the simple structure, high sensitivity, stable performance and anti-electromagnetic interference, the sensor promises an excellent application prospect.