Nano-g accelerometer with differential Fabry–Pérot interferometer for low-frequency noise suppression

This paper introduces a nano-g level optical accelerometer based on a differential Fabry–Pérot interferometer(DFPI) for low-frequency (less than 1 Hz) noise suppression. The accelerometer has its proof-mass supported by two metal spring beams and has a natural frequency of 40 Hz. The DFPI structure is composed of two fiber end-faces and two reflectors made by gold-coated silicon chips attached on each side of the proof-mass. It is both theoretically analyzed and calculated that the differential structure can suppress noises caused by laser source, optical components and temperature, therefore improves the signal to noise ratio of the accelerometer. Experimental results show that the DFPI accelerometer has a noise floor of 4 ng/Hz at 3 Hz to 10 Hz, with a displacement noise floor of 0.62 pm/Hz, a measurement range of 0.88 mg and a sensitivity of 1699.7 V/g. The DFPI mechanism improves the noise performance at 0.1 Hz from 100 ng/Hz by a single FPI to 24 ng/Hz by DFPI, and improves the bias instability from 49 ng to 17 ng. The proposed DFPI accelerometer has the potential applications on seismic acceleration measurement for mineral exploration and active vibration isolation.