The Research Of Doppler Effect-based Optical Fiber Ultrasonic Detection

With the continuous development of modern science and technology, ultrasonic testinghas received extensive attension as a very important non-distructive testing technology and itsapplications are also expanding. Optical fiber sensing technology has also been widespreadconcerned and greatly developed because it has many unique advantages. Therefore, opticalfiber ultrasonic testing technology, which combines ultrasonic testing and optical fibersensing technology together, has a broad application prospects.When light propagates in fiber, affecting by external vibration it will produce afrequency shift, which we call Doppler effect in optical fiber. According to this effect we havedesigned a new type of optical fiber sensors, called fiber optic Doppler(FOD) sensor.This research performed ultrasonic test using FOD as a probe, and investigated theapplication of FPGA(Field Programmable Gate Array) in ultrasonic detection by utilizing itspowerful function in logical operations, real-time control and signal processing. Completedworks are as followed:(1) Grasped structures of several commonly used optic fiber sensors, analysisedDoppler effect in optical fiber, designed and producted optic fiber sensor probebased on Doppler effect, studied the signal technology and performed computersimulation.(2) Briefly introduced the structural features of ALTERA Company’s Cyclone Ⅱgeneration FPGA and designed ultrasonic testing simple systems which usedEP2C8T144C8as a core chip.(3) Discribed Qutuars software which was demanded in designing FPGA, and used thissoftware to write the system control module and perform computer simulation.(4) Bulit a ultrasonic detetion system using fiber optic Doppler sensor as probe.Performed the experiments.