Design and Analysis of a High Sensitivity FBG Accelerometer Based on Local Strain Amplification

Abstract

A fiber Bragg grating (FBG) accelerometer based on a push–pull elastic cylinder structure is demonstrated. First, the model based on the uniform cylinder structure is analyzed and the optimized accelerometer parameters are given. Then, by designing a radius-varying cylinder structure, the FBG strain becomes larger than the cylinder strain, which leads to enhanced sensitivity amplification for a small accelerometer size and relatively high resonant frequency. Meanwhile, the influence of the transverse force on the accelerometer is theoretically analyzed. These results indicate that the transverse-induced FBG deformation is very big so that a strict transverse constrain is needed. The formula of the strain magnification is derived and the design rules of the strain magnification are given. After structure optimization according to the rules, the FBG strain increases to 1.5 times, the sensitivity increases to 1.82 times, whereas the resonant frequency reduces to 0.9 times compared with the parameters of accelerometer based on uniform cylinder structure. Finally, the accelerometer size reduces to $\Phi {20~{\rm mm}\times 34~{\rm mm}}$ , the sensitivity increases to 623 pm/g, and the resonant frequency reduces to 449 Hz.