Design And Research Of Fiber Grating Sensing Networks

As novel passive optical components, fiber gratings have a comprehensive prospect in optical communication and sensing systems, due to their unique optical properties. In their sensing applications, fiber gratings attracts numerous attentions for their high sensitivity, large dynamic range, small size, good reliability and endurance, convenience for sensing networks, immunity to electromagnetic perturbation, etc. In the past decade, researches on fiber gratings have improved so much. Fiber grating sensors to detect the parameters such as strain, stress, pressure, temperature, displacement and acceleration have been applied in long-term health monitoring of large structures such as bridges, dams, concrete and steel structures. Furthermore, temperature-monitoring techniques based on fiber grating sensors become more and more mature in petrochemical and electrical industries. With development of fiber grating techniques, fiber grating sensors and sensing systems definitely possess a brighter future.The dissertation, which is supported by National High Technology Plan (The 863 Plan), Key Science and Technology Programme, Tianjin, and Shanghai Science and Technology Programme, focuses on the solutions of key problems in FBG sensors'engineering applications. In this dissertation, we obtained innovative research progress in fabrication of fiber gratings and FBG sensors and development of signal demodulation techniques, on the basis of research on theories and applicable techniques combining with practical demands. The dissertation consisting of six chapters, includes the following contents:Chapter One: The principle, classification, applications, development status and trend are overviewed. FBG's sensing principle and the latest development of FBG's sensing theory are expatiated and analyzed.Chapter Two: The three analysis methods of fiber gratings—Coupled mode theory, Transmissive matrix method and Fourier transformation method are introduced in detail, the content and applicable range of which are compared. On the basis of transimissve matrix method, the distribution and spectra of typical fiber gratings are simulated and analyzed, including uniform fiber Bragg grating, long period grating, chirped fiber grating, Tapered fiber grating, Moriéfiber grating, Blazed fiber grating, phase-shifted fiber grating and superstructure fiber grating.Chapter Three: Key techniques are developed in fabrication of fiber gratings as a product, including chemical pretreatment technique of optical fiber, Bragg wavelength control and stabilization techniques, apodization techniques, etc. In our experiments, the Bragg wavelength shift of sensing FBG reaches 10nm; the tuning range of Bragg wavelength comes to as much as 40nm by using a novel tuning structure of our design, which has achieved the international leading level. By utilizing our own apodization techniques, the group delay fluctuation of chirped fiber grating we fabricate attain 10pcs, on the basis of which chromatic dispersion compensator is produced with a excellent performance.Chapter Four: Design, material selecting and fabrication method of various FBG sensors are studied, aiming at the sensors'good reliability and adaptability. The...