Research On Zero Point Stabilized Acoustic Sensing Technology Using High Attenuation Fiber

The Acoustic sensor is indispensable in manufacturing measurement industry and multitudinous domains.However,traditional electronic sensor doesn't have sufficient detection accuracy and is not suitable for some special cases,The optical fiber interference acoustic sensor is relatively sensitive,small in size and highly applicable,which meets the standard in various engineering applications and daily life.However,since the current mainstream type of optical fiber acoustic wave sensor is limited by the structure of the Fabry-Perot interferometer(FPI),the interference spectrum of this structure is very sensitive to changes in ambient temperature without special processing or compensation.And detection sensitivity can be easily affected by sensors' zero point drift.Based on the "zero point temperature drift",this article first proposed a Fabry-Perot interferometric sensor based on a high-attenuation fiber.The sensor contains two wavelength-matched fiber Bragg gratings(FBG)as the two reflecting surfaces of the Fabry-Perot(FP)cavity,where the FBG is made of an excimer laser on a standard single-mode fiber(SMF).What's more,in the middle of the cavity,a part of the high attenuation fiber(HAF)is welded using wet chemical etching.Based on the strong evanescent field effect of the micro-nano fiber,the sensor can sense the small refractive index change of the surrounding medium due to sound waves,and realize underwater sound wave detection with a signal-to-noise ratio of more than 40 dB.Besides,the HAF's ability to absorb light energy and convert it into thermal energy can help achieve temperature compensation and further improve detection stability.In addition,graphene oxide(GO)and optical fiber sensing technology are combined for acoustic sensing research.The graphene oxide film is used as a vibrating membrane,which is combined with an optical fiber to form an FP interference structure for detecting weak sound waves.Two structures of SMF-HCF-GO and SMF-HAF-HCF-GO are designed for comparison in this subject.The experimental result shows that,the minimum detectable sound pressure of the two structures are 39 ?Pa/Hz1/2 and 49 ?Pa/Hz1/2,respectively.And the two structures have linear sound pressure responses to sound waves of 512.54 mV/Pa and 410.24 mV/Pa.And based on the photothermal effect of high-attenuation fiber,the latter can achieve zero-point stability by adjusting the power of the pump laser.