Design And Research Of Double-Clad Fiber Microbend Sensor And Fiber Grating Sensing Network

Fiber sensing technology is one of the most rapidly developing sensing technologies. Fiber sensor has many outstanding feature, such as smart structure, light weight, resist the electromagnetism disturbance, corrosion protection, high sensitivity, form network easily, which make it have wide applications in fields of Aerospace, Voyage, petrochemical complex, electric industry, nuclear industry, medical apparatus and instruments, et al. In addition to replace the traditional type of electrical and mechanical sensor, new applications of fiber sensor have been found and realized. New types of fiber sensing principle and sensor structure emerge in endlessly, and fiber sensing system of more points and parameters detection has continually been improved. Research on new types of fiber sensor principles, structures and methods of detection, realization of key technology of fiber sensing network, and pursuit sensing system of high speed, high precision and large scale have always been the persistent pursuit of scientific workers.In this thesis, we mainly focus on the designation and realization of new kind of fiber sensor and the research of fiber grating networks technology. With the research project of my supervisor, which is China Postdoctoral Science Foundation "Research on fiber grating sensing technology and application for the pressure detection in mine" (20080441150), Using special structure characteristics of double-clad fiber, we design and develop a new kind of double-clad fiber micro-bend sensor, and do the theories and empirical research on its detection technology. This thesis can be divided into five chapters, and the contents are listed as follows:Chapter 1, generally introduces the status quo and development trend of fiber sensing technology, including fiber grating sensing technique, fiber micro-bend sensing technique and fiber sensing network technique.Chapter 2, the fundamental theory of fiber Bragg grating are demonstrated The basic principle of fiber grating sensing technique and several usual demodulation methods can be found in this chapter.Chapter 3, the sensing principle and detection technology of fiber micro-bend sensor is introduced.Chapter 4, the theoretical model of double-clad fiber bending loss through theoretical and simulation method is established. The best structural parameters are got through the simulation of the relationship between sensing sensitivity and several kinds of double-clad fiber structure parameters. After these, the best period, tooth spacing and teeth number of deformation device are analyzed. Finally, for the special structure of double-clad fiber and its coupler, double-clad fiber microbend sensor and its dark-field detection technology are experimental studied.Chapter 5, a high-speed sensor multiplexing network system based on the F-P tunable filter is designed. Judging peak of FBG, which is the key problem of demodulates precision has been further studied. By the measuring of fiber grating sensor, the system performance of multipoint real-time monitoring has been confirmed.