Research On Multi-channel Fiber Bragg Demodulation System

With the development of the fiber grating sensor technology, the field of the technology is growing up. It played a significant role in aerospace, shipping, national defense building, petrochemical and large engineering areas. We can see the application of all kinds of fiber optic grating sensor and the researching by the current trend of fiber Bragg grating; it requires a higher stability and function of fiber grating sensor demodulation system. In this context, it becomes a pressing need to design a demodulation system for the large and complex fiber grating sensor network. The research topic is the multi-channel fiber Bragg grating sensor demodulation system. We study the application status of fiber grating sensor and development trends; explain the purpose and significance of the topic; study the basic principle and several demodulate methods; design a multi-channel fiber Bragg grating sensor demodulation system and deeply discuss each part of the system; research the key technology of the system, such as the tunable laser and wavelength calibration, through the experiment and make conclusion.This article discusses the application status and development trend of the FBG sensing technology, and briefly introduces several ways of FBG wavelength demodulation:Optical Spectrum Analyzer, Edge Filter, marching grating, Non-equilibrium Maher-Tsang Tak interference, Michelson interferometer, Tunable F-P filter, Dispersion, Tunable narrow-band light source. Analysis the narrow-band light source method detail and design multi-channel demodulation base on it. Research the Semiconductor optical amplifier SOA and the characteristics and working principle of tunable FP filter, test the tunable laser source used in system, the results show that the output optical power and spectrum have a significantly increased than traditional light sources in demodulation system. It improves the system SNR and demodulation accuracy. According to the system requirements, divide the system light source into eight parts, each part of light source used in a 32-channel fiber Bragg grating demodulator. It makes the using of the system light source effectively, and improves the system's using flexibility; adjust freely to meet the real-time project needs. Meanwhile, discuss the wavelength calibration of the system and compare the use of reference grating and interleaver filter as a wavelength calibration reference system, the experimental data shows that using interleaver filter as the wavelength calibration of the system reference is better. Improve the production of the interleaver filter; use a zero temperature glass in production to reduce the wavelength drift of interleaver filter. Test the system and make a result:demodulation channel 256; system frequency 50Hz; range 1270nm-1350nm; resolution 1 pm.