Fiber Fabry-Perot accelerometer with extended dynamic range and low noise floor

Optical interferometric accelerometers are widely used in seismic monitoring, petroleum resources exploration, and structural health monitoring due to their low noise floor and resistance to electromagnetic interference (EMI). However, their small working range limits further applications. To broaden the working range of the sensor while ensuring the inherent anti-electromagnetic interference capability of the optical sensor, this paper proposes an orthogonal optical path (OP) range broadening scheme (OORBS). The linear working range is widened by splicing the linear intervals in the two interferometric signals. Subsequently, a platform based on a nano-displacement unit was built to validate the feasibility of the OORBS under static and AC cavity length variations. The experimental results show that the OORBS can recover the cavity length completely. Finally, the OORBS was combined with an accelerometer to realize the range broadening. The OORBS extends the accelerometer’s working range from 0.42 mg to 68 mg while maintaining the high sensitivity, which is about a 162-time improvement. The accelerometer’s noise floor reaches 4.8 ng/Hz 1/2 at 15 Hz and accordingly, the dynamic range of the accelerometer increases from 98.8 dB to 143 dB. The proposed method is general to address the Fabry-Perot-based dynamic range limitation and can be adapted for various interferometric sensors, such as Fabry-Perot, grating, and Mach–Zehnder.