Temperature-insensitive FBG acceleration sensor based on strain chirp effect

Abstract

The measurement of low-frequency vibration signals is a very important job in the fields of earthquake early warning, health monitoring of large-scale engineering structures, and geological exploration. Aiming at the problem of Fiber Bragg Grating (FBG) acceleration sensors’ cross-sensitivity to temperature and strain when measuring low-frequency vibration signals, this paper developed an M-shaped double cantilever beam structure that can produce chirp effect with its own structural characteristics, thereby making the sensor insensitive to temperature. Through theoretical analysis and simulation, the paper obtained the relationship between the reflection spectrum bandwidth of the chirped FBG and its acceleration. It adopted a spectrometer and a vibration test system to detect the reflection spectrum bandwidth of the FBG, and then obtained the acceleration. The experimental results showed that, compared with bare fiber grating, the temperature sensitivity of the proposed sensor was significantly lower, and its reflection spectrum bandwidth was not sensitive to temperature changes, moreover, there are good linear relationships between the reflection spectrum bandwidth, the power of the light, and the acceleration. The sensitivity was about 256 pm/g, the natural frequency was 66 Hz; therefore, the proposed sensor had realized high-performance detection of low-frequency vibration signals.