Broadband Flat Response High Sensitivity FBG Accelerometer Based on Multi-resonance Structure

A broadband flat response high sensitivity Fiber Bragg grating (FBG) acceleration sensor is reported that solves the problem that the sensitivity of a vibration sensor is normally constrained by its measurement frequency range. Two sets of cantilever beams with different resonance frequencies and one set of cross beams are used to construct a unique multi-resonant structure with a range of different resonance frequencies. A damping liquid is added to make the resonance peaks broaden and merge to realize a broadband flat response. The effects of the dimensional parameters of the resonant structure and the viscosity of the damping liquid on the frequency response curve of the FBG acceleration sensor are analyzed using a finite element simulation, and the optimization of each parameter is achieved. The resonant structure was fabricated and the overall package of the FBG acceleration sensor was completed using methyl silicone oil as the damping fluid. A vibration test system was built to test and analyze the frequency response characteristics of the sensor, and the results show that the sensor has a sensitivity of 203.4 pm/g and the frequency range of the flat region with an unevenness of less than 3 dB is 250~800 Hz, which is about 3 times better than existing reported state of the art devices.