Study On FBG Demodulation System Based On Novel Filters

Optical fiber grating sensors are widely used in intelligent structures monitoring of aviation, aerospace, marine, and so on, for the unique nature of anti-electromagnetic interference, corrosion resistance, easy to construct sensor networks, etc. Just as above illustrated, Fiber grating sensors could also be applied in the area of civil engineering, petrochemical, and others. In the light of rapid development of Hai River and urban express in Tianjin, the projects of bridge construction and maintain have increased in recent years. Facing with so many tough troublers in the process of fiber grating industrialization, a novel equipment for FBG spectra interrogation based on the technique of tunable Fabry-Perot filter has been developed.The project has been carried out on the basis of FBG mode coupling theory, sensing mechanism, structure of FBG wavelength readout system, signal processing principles, with a FBG demodulation system constituted by tunable Fabry-Perot filter and sensing signal processed by all phase filtering technique introduced. The main ideas discussed in the paper are as follows.1. Intensive study at the application area of FBG, research progress at home and abroad, as well as dilemmas faced in its industrialization process. Then draw out the main topic of the research.2. With fiber grating mode coupling theory described, and FBG characteristics classified one by one, the FBG sensors detection theories at the fields of stress and temperature are modeled. The scheme of wavelength readout system formed by tunable Fabry-Perot filter is disused in more details.3. The demodulation system overall framework is analysis, with each hardware module selected and connected. Corresponding with the hardware architecture, the software of data acquisition module is realized, and spectrum peak detection & positioning algorithm developed. In addition, human-computer interaction interface is constructed. The system performance is verified, further improvement is proposed.4. The de-noising technique for FBG array reflection spectra is introduced. Deep research on FRR and RRF is carried out. Furthermore, the method of digital filters with zero-phase based on all-phase is applied to the sensing spectra de-nosing. 5. The work carried out during the process of the project is summarized. Aiming at the application background and constantly growth of user needs, more function modules will be added in the near future.