Ultra-high-resolution phase demodulation based miniature fiber-optic accelerometer at low and medium frequencies

A miniature fiber-optic Fabry–Perot (F-P) accelerometer based on phase demodulation is demonstrated for improving sensitivity. The accelerometer is composed of a 11.5 mm diameter cylindrical outer frame, a spring-like diaphragm with a loaded mass block and optical fiber. This structure is not only simple and easy to manufacture, but also greatly improves the performances of the accelerometer. The F-P cavity length is demodulated by phase demodulation with abundant advantages of wide dynamic range, high resolution, independent of fiber loss and light intensity fluctuations. The inertial mass displacement indicating a variation in the F-P cavity length is demodulated and converted to acceleration. Through experimental verification, the resonant frequency of the accelerometer is 232 Hz, and axial sensitivity is flat in 30–180 Hz. The average sensitivity of the flat area is 17.55 µm/g and the transverse crosstalk is around 3 %. The resolution of the sensing system is 2.8 µg within a ±3 mm maximum measurement range by experimental tests. This work gives a fitting option to monitor low and medium frequency vibration in a large range of areas.