Study On The Distributed FBG System For Simultaneous Measuring Strain And Temperature

Due to the development of fiber grating's UV writing technology, FBG possesses the reality that it can be repeatedly and continuously writing several FBG in one fiber, and makes more space for grating sensor. At the same time it creates a new model for the distributed measurement of temperature and stain, namely distributed FBG measurement model. The purpose of this paper is to discuss the system design and experiment research of strain and temperature sensing network of the distributed FBG. The development trend of FBG sensing and several questions to be solved in the practical application are summarized. We study from the following four aspects: the design of sensing head of FBG; the sensing principle; the addressing and demodulation of strain and temperature sensing network of the distributed FBG; the choice of light source and signal demodulation. First, the paper gives more details on the sensing principle of FBG temperature, strain, cross-sensitivity and simultaneous measurement. Further- more, it analyses several kind of multiplexing addressing and signal demodulation technology and proposes a method, which integrates frequency demodulation continuous wave with wavelength division multiplexing, to solve the multiplexing addressing problem of FBG sensing network. The technology of brim filter waves of double refraction fiber Sagnac brim filter is adopted to demodulate sensing signal. The proposed system scheme is testified to be feasible by theoretical analysis and experimental research. Second, temperature and strain measurement system of distributed FBG is designed. The constituent modules and material parts of the whole system are analyzed on principle and designed. Due to temperature and strain performance of FBG, the design scheme of pre-strain sensing head is adopted for simultaneous measurement temperature and strain. The center wavelength is scanned and identified by F-P filter. Finally, temperature and strain performance of FBG is tested and the error of sensing head for simultaneous measurement temperature and strain is given detailed analysis and experimental simulation. Furthermore, addressing progress and signal demodulation of grating array are studied by simulation experiments, and various factors that influence measurement accuracy and their solutions are expatiated.