Research And Realization Of Fiber Grating Sensing Networks

Fiber gratings are attracting considerable interests in applications. They are new type of passive optical components, which are based on the periodical distribution of refraction index in fiber core. Fiber gratings have several distinguished advantages over normal fibers. Because of their intrinsic nature and inherent wavelength-encoded operation, fiber gratings are utilized as sensing elements in recent years. The relevant reports have been appealed much attention throughout the world.Encoding the information on the measurand in a wavelength form has been caused extensively focus. The most important advantage is that wavelength is an absolute parameter and thus does not depend on loss of the system or fluctuation of the source power. Most of today's demodulation techniques rely on optical filtering method, such as bulk optical edge filters, scanning fiber Fabry-Perot filters, WDM fiber couplers, acousto-optic tunable filters and Mach-Zehnder filters. In this dissertation, we mainly focus on the research and realization of fiber Bragg grating networks, including the principles and experiments of sensing and demodulation techniques. The contents are listed as follows:1.Generally introduce the sensing technique, especially the present situation and development of fiber and fiber Bragg grating sensor technique. The fundamental theory of fiber grating is also demonstrated. The basic principle of fiber Bragg grating sensor and demodulation and multiplex technique can be found in this dissertation.2. Using the fiber grating as the sensor unit, we have designed and fabricated a distributed sensor networks with multi-parameter and multi-function (AFSN-I fiber grating sensor multiplex network system). Moreover, the design principle, the system structure as well as the test results are demonstrated in detail. The actual wavelength resolution is 0.0011nm, meanwhile the strain measure resolution is approximatelyδε=1.0με, and the corresponding temperature measure resolution is aboutδT=0.03℃.3.We designed and realized a high-speed sensor multiplexing network system based on the chirp fiber grating and edge filter technique. The high-speed wavelength demodulation of fiber Bragg grating sensor has been turned into practice. The system principle is introduced and analyzed in this dissertation. The system is designed as an all-fiber system, using the chirp grating as the frequency-selective element. It realized the high-speed wavelength-division-multiplexing demodulation of fiber grating sensor.