Miniature FBG Vibration Sensor With High Performance and Low Angle Dependence for Two-Dimensional Vibration Measurement

A miniature fiber Bragg grating (FBG) vibration sensor with high performance and low angle dependence has been proposed and applied in the 2-D vibration measurement of a vibration isolation platform in this article. Considering the bonding points with maxim replacement, the sensitivity and resonant frequency theoretical model of the elastomer and packaged small-diameter FBG were established. The genetic algorithm was utilized to achieve the globally optimized structure sizes under multiple constraints, while the modal simulation analysis was carried out to verify the result. A novel “figure of merit” defined as the product of the resonant frequency, the sensitivity, and the inverse of package volume was proposed for the performance evaluation of the sensor in the unit space of its package. The 1st-order and 2nd-order frequencies of its $X-/Y$ -direction are 1105.4/1266.1 Hz, while the sensitivity is 127.861 and 116.668 pm/g, respectively. The cross-interference in the $X-/Y$ -directions of the sensor is less than 2%. Moreover, the test results of the angle dependence of the sensitivity show that the sensor possesses consistent sensitivity in all directions of the 2-D plane, while the fit sin functions in the $X-/Y$ -direction have a high $R^{2}$ of 0.99851 and 0.99831, respectively. Finally, the 2-D vector vibration measurement capacity of this sensor was demonstrated on a rubber spring vibration isolation platform. The results show that this miniature 2-D vibration sensor is suitable for medium-to-high frequencies vibration vector measurement and has a bright application prospect for the monitoring of machines.