Dual Fiber Bragg Grating Sensor for Vibration Measurement in High Temperature

Fiber optic vibration sensors are widely used in industrial production, security inspection, and other fields due to the advantages of anti-electromagnetic interference, high sensitivity, and high temperature resistance. Traditional fiber optic vibration sensors can only measure a single physical quantity, so it has some shortcomings such as large measurement error and unable to self-calibration at high temperature. Here, we propose a high-temperature two-parameter fiber Bragg grating (FBG) sensor for monitoring temperature and vibration signals simultaneously. Two sets of cascaded gratings are written onto a quartz fiber by using a femtosecond laser. One set of gratings is attached to a cantilever beam with a mass block to sense vibration signals. The structure of the cantilever beam is designed and optimized by theoretical calculation and finite element analysis. Another set of gratings is used to sense temperature and compensate for the effect of temperature on vibration. This sensor has a characteristic frequency of 2100 Hz and an excellent optical response from $25~^{\circ }$ C to $1100~^{\circ }$ C. After temperature compensation, it has a sensitivity of 0.286 pm/g in the range of 1–50 g. This work provides a new way for simultaneous detection of vibration and temperature in extreme environments, such as high temperature and strong vibration.