Fiber Grating Detection Ultrasonic System Design

This dissertation is based on the principle of fiber optic ultrasonic sensors, with an emphasis on the designs of detection of focused ultrasonic fields with fiber Bragg Grating.Through comparing five fiber optic detectors, we proposed the ultrasound sensing system based on fiber Bragg Grating detection as a final scheme. We also analyzed the correlation demodulation theory of the fiber grating sensing system and the realization of four demodulation systems. Synthetically considering the characters of detected signals, we used transmission model of fiber Bragg Grating. The system was divided into three parts and the related design ways were presented. The first part is to select an immersed and focused ultrasound piezoelectric transducer to generate focused ultrasonic field through characterizing the waveform, field parameters, transducer, and detecting principle of ultrasonic waves. We presented the ultrasound generating system, which was experimentally proved the existence of ultrasound and the place of the focused point as a reference for further fiber Bragg Grating detecting. The second part is to design the appropriate photo detector whose testing performance was shown. The third part is to select a satisfying Bragg Grating on the basis of analyzing the frequency response of detecting ultrasound with fiber Bragg Grating. In addition, some related experimental results were also presented and discussed.The principles and the ideas of the above-mentioned system, and the key points of the realization process of the blue print are discussed in detail. We also demonstrated the new technology referred to the system design, and made some innovations based on them. By testing and adjusting the system again, we finally realized all the functions of detecting focused ultrasonic field parameters. Processing the experimental data with related software, the results proved the feasibility of the scheme of fiber Bragg Grating sensing ultrasound system.Finally, the problems existed in the detecting ultrasonic system using fiber Bragg Grating and some opinions of the future improvement of the system were brought forward.