Research Of High Speed Acoustic Vibration Sensing Demodulation System Based On Interference Phase Extraction

The high-speed fiber acoustic sensing demodulation system based on interference phase extraction has the advantages of high sensitivity and strong anti-interference ability.It has the advantages over traditional sensors in extreme environments.In this paper,the weak signal detection experiments in low-pressure carbon dioxide gas are carried out.The sensitive components are deeply studied and designed,and the demodulation system suitable for this environment is set up and tested.The major works done in our research are as follows:1.This paper gives an overview of the various implementations of optical fiber acoustic sensing,which is divided into two parts: the sensor and the sensing demodulation system.The current status of the research is discussed.The problems and challenges we faced are analyzed in detail.2.The performance and parameters of the sensor is analyzed.We use the polyphenylene sulfide film as sensing element,by setting a certain size of the diaphragm,while applying a certain pre-tension diaphragm so that the first-order natural frequency of the diaphragm is 54.3 kHz.So we can set the upper limit of the sensor response frequency to more than 40 kHz.3.We simulated the influence of the wavelength drift and cavity length drift ?L on the accuracy of the system demodulation results.When the ?? is 2nm,the attenuation ratio of the demodulation result is 10%.When the ?L is 5?m,the attenuation ratio of the demodulation result is only 5.4 ‰.4.We tested the sensor system with high frequency ultrasonic wave in a low-pressure carbon dioxide gas environment.The output of the sensor system was maintained at a high signal-to-noise ratio of 14.45 dB at a pressure of 270 Pa in carbon dioxide gas and the deformation of the membrane was ±5.2 nm.The detection sensitivity is 10.4nm/kPa.