Sensitivity Enhanced Strain Sensor Based on Two-Arm Vernier Effect

A novel sensitivity enhanced strain sensor based on two-arm Vernier Effect is proposed and demonstrated. This sensor is prepared by pasting two in-line Fabry Perot interferometers(FPIs) in cross configuration to a diamond metal frame. Because of the contribution of the FPI in vertical axis, it has a greater magnification factor M' compared to traditional sensors based on Vernier Effect. The structure of the diamond metal frame is optimized using the finite element method by COMSOL. The numerical results indicate that the M' increases with the decrease of the angle of the diamond metal frame, and when the angle is less than a critical value, M' decreases sharply to a fixed value due to the vertical axis contraction and the release of preloading force. The experimental results show that when the diamond angle is 60, the M' is 26.6 which is 4 times that of the sensor in parallel configuration using same FPIs while the free spectra range(FSR) unchanged. This feature is important to improve the sensitivity while controlling device costs.