Low-Frequency High-Resolution Fiber Fabry–Perot Interferometric Accelerometer Based on Double-Spring-Supported Oscillator

A compact optical fiber Fabry Perot accelerometer was designed for micro vibration measurements in the low-frequency band below 1 Hz. A double-spring-supported spring-mass oscillator was designed to increase the cross-axis suppression and reduce the structural stress, facilitating the low mechanical thermal noise of the accelerometer. The mechanical thermal noise of the accelerometer was reduced to 0.069 ng/Hz 1/2 with the quality factor of 121.8 and the fundamental frequency of 13.4 Hz. Moreover, by carefully adjusting the extrinsic Fabry-Perot interferometer formed between the cleaved fiber end face and the proof mass through the designed screw-in integration adaptor, the acceleration can be read out with high sensitivity which is achieved as 2.104 (±0.046) V/mg experimentally. The self-noise of the accelerometer was demonstrated as low as 1 ng/Hz 1/2 at 1 Hz and 11 ng/Hz 1/2 at 0.1 Hz respectively, which is the superior level for this frequency band in the existing fiber-optic accelerometers as far as we know. The proposed optical fiber Fabry-Perot accelerometer can satisfy the requirement of microturbulence detection in the fields of geophysics and aerospace.