| Fiber Bragg Grating is a kind of fiber optic device which is expected to be of great prospect of application in fiber communication. Nowadays the manufacturing and application research on FBG has gone into a popular field of the fiber optics technology. As a sensor, FBG can be immune from light source disturbance and system loss by transforming sensing information into its reflecting wavelength shift. Besides, FBG is very reliable and also immune from electromagnetic signals and corruption. Many FBGs can be put together on a single fiber to construct a FBG network to build a distributed sensing system. Such a system has shown the unexampled merit of FBG. The key technology of FBG sensing lies in how to measure the minute shift of Bragg reflecting wavelength precisely. And this is called demodulating of the coded wavelength signals. Though, the OSA can be used to do the measurement, it can not be applied to practical industry situation because of its huge-size and high-cost. Therefore, developing high-resolution and low-cost FBG demodulator is the key issue when it comes to FBG sensors industrializations. Although a large number of researchers in domestic research units have been doing a lot of research and investigations on the demodulation of FBG sensing, most of the researches are still in the step of lab experiments and have not yet met the requirements of mass practical industrial productions.This paper has done a research to improve the precision of demodulation system of FBG sensing. It contains the analysis of three precise demodulation systems which based on different demodulation schemes respectively;two kinds of typical computer information processing systems utilized in the demodulation of FBG sensing;and a unique dynamic curve algorithm which can improve the precision of the demodulation system of FBG sensing.Firstly, this paper has given a general comment on the benefits of FBG, also reviewed the developing history of FBG and FBG demodulation technology. And pointed out FBG demodulation technology is the key technology lies in the application of FBG sensing.And then, this paper focused on the research of improving the measurement precision of FBG demodulation system.The chapter 2 has analyzed the three precise demodulation systems. One is based on the technology of interference detecting, another is based on the technology of filter, and the third one is based on the technology of adjustable optic source. Each of the resolving power of wavelength of the three systems is within 10 pm. Moreover, one of the three has a resolving power of 1 pm.Further, the chapter 3 has illustrated two kinds of typical computer information processing systems utilized in the demodulation of FBG sensing: the processing system based on the technology of DSP and the processing system based on the embedding technology.The chapter 4 has concentrated on dealing with the sensing data. And a unique dynamic curve algorithm is proposed in chapter4 to improve the precision of demodulation system of Bragg grating sensor utilizing the homemade equipments, when only relative software needs to be changed. This method is based on Lagrange Expressions and groups of accurate sensing Lagrange curve are worked out by three pairs of data, and one of the three can be set and modify by the experimenter for the sake of precision. Errors of the value of wavelength are all within ±7pm, so that the precision of the system of demodulation system of Bragg grating sensor is improved. |
PDF Full Text Request