Research On Fiber-optic Sound Sensing Technology Based On Fabry-Perot Cavity

Compared with traditional electroacoustic sensors,fiber-optic acoustic sensors have the advantages of anti-electromagnetic interference,high sensitivity,large bandwidth,large dynamic range,flexible sensing system and good reusability.In recent years,it is widely used in national defense security,industrial monitoring,ultrasonic non-destructive testing and medical imaging and other fields.Most of the current fiber-optic acoustic sensing technologies use acoustic coupling materials or acoustic-sensitive diaphragms,which can improve the sound detection performance to a certain extent,but there are disadvantages that large-bandwidth and large dynamic range acoustic detection can not be achieved at the same time.In this paper,the key technologies of Fabry-Perot?F-P?cavity fiber optic acoustic sensor are studied.The main work is as follows:?1?The theory of the refractive index of air is analyzed,which shows refractive index depends linearly on sound pressure.The F-P cavity theory is analyzed in detail,which provides theoretical guidance for the design of acoustic sensor.?2?The overall scheme of F-P cavity fiber acoustic sensing system is proposed and the F-P cavity is designed and manufactured.The relevant optical parameters affecting the sensitivity of F-P cavity acoustic sensing are investigated,and the simulation verification is carried out.The F-P cavity features reflectivity of 99%and cavity length of 5 mm at last.?3?The principle and implementation process of the stable control demodulation method of the working point are analyzed.The real-time correction of the working point of the system is realized by STM32 and LABVIEW,and the fluctuation range of the light intensity at the working point is controlled to±1%.?4?The performance of acoustic sensing experimental system is tested and analyzed in detail.It shows voltage sensitivity of 3 mV/Pa at 0 dB gain and a minimum detectable sound pressure of 20 mPa/Hz^1/2 at 1 kHz.By the work of this paper,F-P cavity acoustic sensing technology features no mechanical resonance frequency,broad-band frequency response and large dynamic range.At the same time,the sensitivity is further improved by increasing F-P cavity finesse,so it possesses broad development prospects.