Fiber Bragg Grating Demodulation Based On DSP

At present, Fiber Bragg Grating(FBG) is one of the most potential and typical optical passive components. FBG can be immune from light source disturbance and system loss by transforming sensing information into its reflecting wavelength shift, which has the characteristic of wavelength coding. Besides, FBG is of good reliance, immune from electromagnetic signals and corruption, and can be constructed as FBGs network by being put together on a single fiber so as to realize distributed sensing, which is an unexampled merit for FBG. Therefore, the research and the application in fiber grating attracts more and more attention in recent years.However, demodulation technology of FBG is one of the difficulties in the fields of FBG sensing technique research. Recently although a large number of researchers in domestic research units have been doing a lot of research and investigations on the demodulation methods of FBG, most of the researches are still in the phase of lab experiments and have not yet met the requirements of the practical industrial mass productions.Based on these problems, a distributed FBG wavelength demodulation system which is based on DSP is presented and adapts to engineering application. This system applies a tunable fiber F-P(Fabry-perot) filter to demodulate the wavelength variations of FBG. The voltage control signal providing for F-P filter is produced by the counter of TMS320VC5402 DSP through a D/A converter. When the light wavelength permeating the F-P filter equals to the Bragg reflection wavelength, there is an interrupt request signal, DSP deals with the useful information after DSP answers interruption, and then obtain the corresponding changes of the measured parameters.In this complicated research dealing with optics, mechanic and electrics, the main contributions of this paper are:(1) Expatiate the basic sensing and demodulation principles of FBG, andanalyze systematically the main factors affecting FBG wavelength.(2) Put forward some FBG demodulation methods which have high research values, and then analyze and compare these methods, at last summarize the merits and disadvantages of these methods.(3) As for the elementary knowledge of this dissertation, expatiate and analyze systematically basilica parts of an apparatus:TMS320VC5402 DSP.(4) Choose a distributed FBG sensing demodulation system, namely tunable F-P filter method. Based on this system, this paper gives a demodulation solution detailed in system functions, and respectively design hardware and software of all subsections.(5) To do distributed sensing demodulation experiment to detect the distributed temperature variables, the results show that the whole system reaches anticipative aim and is about to be ready for trial and engineering application.(6) Based on the results of experiments, summarize the dissertation and anticipate the future research works.