Application And Research Of Ultrasonic Sensing System Based On Fiber Bragg Grating

Ultrasonic is an important means of nondestructive testing and an important way of underwater communication.Piezoelectric ceramic transducer(PZT)is generally used in ultrasonic transmission and reception,but PZT can only realize single point detection due to its resonance characteristics,and the detection range is greatly limited.In recent years,with the rapid development of optical fiber sensors,fiber Bragg grating(FBG)has been used in various fields due to its advantages of anti-electromagnetic interference,high temperature resistance,anti-corrosion,small volume,light weight,easy reuse and so on.In the aspect of ultrasonic sensing,FBG has a wider frequency detection range.Based on this characteristic,the research of FBG ultrasonic sensor is of great significance.In this paper,based on the principle of FBG ultrasonic sensing,a set of fiber Bragg grating ultrasonic sensing system was built,and the sensing performance of the system in the megahertz high frequency ultrasonic field was studied.The research contents include amplitude characteristics and frequency response.The experimental results show that the amplitude characteristics of the system are consistent with that of the traditional PZT sensor,but the stability is not good enough under three different frequencies of ultrasonic field of 1.25 M,2.5M and 3M.FBG ultrasonic sensing system has a wide frequency detection range,which can cover the total frequency domain of the three frequency transducers.In this frequency domain,FBG ultrasonic sensing system has a more stable frequency response.For the characteristics of wide bandwidth detection range and stable frequency response,this paper explores the practical application of FBG ultrasonic sensing system in resonance thickness measurement.Through theoretical calculation,the resonance spectrum characteristics of the material are analyzed,and the "water-aluminum-water" dielectric layer model is established.The transmission coefficient and reflection coefficient of the model on the acoustic frequency are simulated by computer in the range of 0-5MHz,and the FBG ultrasonic sensing system is applied.The transmission and reflection signals of 3mm,5mm and 10.2mm aluminum plates were detected and analyzed.The experimental results show that the FBG ultrasonic sensor can measure the thickness by resonance method,and it has a certain application value in the broadband ultrasonic signal detection.