Study Of The Dynamic Stress And Refractive Index Sensing Of Fiber Bragg Grating

The research works of the dissertation are focus on FBG (Fiber Bragg Grating) sensors for the strain and refractive index, and their extensive application. The researches of FBG sensor have been attractive in recent years, from basic measurement for strain and temperature, and extending to higher resolution measurement and wider practical applications. In the thesis, the basic concept is firstly introduced. For high resolution and practical application, the advanced researchers of FBG measurement are presented as following:The reconstruction for arbitrary stain distribution of FBG is presented in Chapter 3. Based on the concept of layer peeling, two algorithms, which are signal cut-off method and discrete matrix method, are developed and applied in arbitrary stain distribution reconstruction.Based on DWDM (Dense Wavelength Division Multiplexing) and temperature controlled FBG demodulation, two highe dynamic resolution resolution sensing systems are presented in Chapter 4. Comparing to the classic vibration sensor, capility and resolution of FBG sensor are experimentally verified in vibration measurement of cantilever.The application for process monitor in laser thrombolysis is demonstrated in Chapter 5. The sensing parameter in laser thrombolysis is shockwave induced by laser irradiating in blood. With the laboratorial experiment and vitro experiment, the FBG sensing system is verified to be available in process monitoring.The phase shift FBG for refractive index measurement is demonstrated in Chapter 6. The phase shift FBG is partially etched by HF solution while the rest is protected. With wavelength difference or reflected power demodulation, the phase shift FBG presents characterization of temperature insensitivity in refractive index measurement.A refractive index sensor based on DFB (Distributed FeedBack) fiber laser for ultrahigh resolution measurement is designed in Chapter 7. Compensating to the temperature variation of active FBG, the wavelength difference demodulation scheme is proposed. And the relationship between the wavelength difference and refractive index is analyzed. The ultrahigh resolution is theoretically verified.