| The Fiber Bragg Grating (FBG) is applied widely in sensing field for its unique characteristics. The achievements on FBG study are focused on the distributed and low frequency FBG sensing in industry nowadays. But there is no satisfied way for high frequency detection, such as vibration. In order to meet the needs of this kind of signals detection, the FBG dynamic demodulation methods are being developed. The study of FBG dynamic demodulation methods is becoming a main task to be solved urgently.On the base of related extensive material reading, the achievements reviewing on FBG sensing demodulation within ten years plus and the analysis of problems existed in this field, three dynamic demodulation methods were proposed in the way of density modulation, that is of double FBG density modulation, Amplified Spontaneous Emission Broadband Light (ASE) spectrum characteristic and CWDM side band characteristic respectively. Based on theoretical analysis, FBG sensing demodulation systems were established separately. According to the characteristics of density demodulation, the relationship between Bragg wavelength shift and system output was get by converting FBG wavelength into light density variation with Matlab calculating the real value. Causes of the differences between the simulation results and the math model were analyzed. The performances of the systems are going to be improved.In order to realize dynamic demodulation, the demodulation method by making use of ASE light source spectrum characteristic, which is one of the proposed methods, was selected to demonstrate the feasibility of the method. A FBG current sensing probe was constructed with a GMM rod. An alternating current measuring system was established with an ASE light source and the probe and a measurement was carried out on 50Hz alternating current signal. Through the experiment of temperature sensing, the demodulation system was calibrated.According to the characteristic of the GMM, an experiment study on ac... |
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