  In this paper, a differential MOEMS accelerometer based on the Fabry-Perot
(FP) micro-cavities is presented. The optical system of the device consists of
two FP cavities and the mechanical system is composed of a proof mass that is
suspended by four springs. The applied acceleration tends to move the PM from
its resting position. This mechanical displacement can be measured by the FP
interferometer formed between the proof mass cross-section and the optical
fiber end face. The proposed sensor is fabricated on a silicon on insulator
(SOI) wafer using the bulk micromachining method. The results of the sensor
characterization show that the accelerometer has a linear response in the range
of 1g. Also, the optical sensitivity and resolution of the sensor in the static
characterization are 6.52 nm/g and 153ug. The sensor sensitivity in the power
measurement is 49.6 mV/g and its resonant is at 1372 Hz. Using the differential
measurement method increases the sensitivity of the accelerometer. Based on
experimental data, the sensor sensitivity is two times as high as that of a
similar MOEMS accelerometer with one FP cavity.
