Fig. 1. Silicon-based MEMS wheel-shaped diaphragm. (a) Structural schematic; (b) diaphragm section view

Fig. 2. Finite element simulation of silicon-based MEMS wheel-shaped diaphragm. (a) First order vibration mode; (b) simulation model; (c) frequency response curve; (d) directivity at different frequencies

Fig. 3. Schematic of silicon-based MEMS wheel-shaped diaphragm fiber-optic acoustic sensor structure. (a) Cross-sectional view of sensor structure; (b) schematic of FP interferometric principle

Fig. 4. Fabrication process of silicon-based MEMS wheel-shaped diaphragms. (a) Photolithography (device layer); (b) DRIE (device layer); (c) photolithography (handle wafer); (d) DRIE (handle wafer); (e) RIE (silicon oxide); (f) sputtering (device layer)

Fig. 5. Fiber-optic acoustic sensor with a silicon-based MEMS wheel-shaped diaphragm. (a) Silicon-based diaphragm; (b) physical sensor; (c) schematic of structure

Fig. 6. Fiber-optic acoustic sensor FP cavity length measurement of wheel-shaped diaphragm. (a) Test platform; (b) interferometric spectrum measured by the sensor

Fig. 7. Test system for fiber-optic acoustic sensor with a silicon-based MEMS wheel-shaped diaphragm. (a) Schematic of test system; (b) photo of part of test device

Fig. 8. Frequency response curves of fiber-optic acoustic sensor with a silicon-based MEMS wheel-shaped diaphragm

Fig. 9. Acoustic response curves of fiber-optic acoustic sensor with a silicon-based MEMS wheel-shaped diaphragm under different acoustic excitations. (a) 4 kHz; (b) 7 kHz; (c) 10 kHz; (d) acoustic pressure sensitivity curve under 7 kHz excitation

Fig. 10. Directional response testing of fiber-optic acoustic sensor with a silicon-based MEMS wheel-shaped diaphragm. (a) Photo of test setup; (b) experimental and simulated direction response curves at 7 kHz

Fig. 11. Test experiment of mini-UAV noise. (a) Test environment; (b) background noise of experimental site

Fig. 12. Mini-UAV radiation noise spectra. (a) Noise spectrum acquired by electret condenser microphone; (b) noise spectrum acquired by wheel-shaped diaphragm fiber-optic acoustic sensor

Fig. 13. Mini-UAV test results at different distances. (a) Test results by electret condenser microphone; (b) test results by wheel-shaped diaphragm fiber-optic acoustic sensor