Study On Two-Parameter Sensing Based On Dual-Grating

The Fiber Bragg Grating(FBG) is one of the fiber passive devices with the fastest developing speed in recent years.The fiber Bragg grating sensor has been used widely in many fields, such as industry and agriculture, environment monitoring, space exploration, civil engineering and rail transport, etc. It becomes the research all over the world. So it is of great scientific significance and economic value to research FBG sensors with features of high performance and low cost.It is the hotspot and difficult to measure multi-parameter with fiber grating sensor in the practical use. The study mainly focuses on the measurement of two-parameter temperature and strain in this thesis. Introduce the existing method of temperature and strain simultaneous measurement in detail, as well as summary and analyze their benefits and shortcomings. On the basis of the study above,A double-grating combination structure based on equi-intensity cantilever is adopted to achieve simultaneous measurement of temperature and stress. Selecting two fibers Bragg gratings of the same batch of production with consistent parameters, paste them to the upper and lower beam surface, respectively. The upper and lower beam grating suffer from equivalent stress but in opposite direction, resulting in two reflection peaks to achieve the simultaneous measurement of temperature and stress. The experiment result shows that the method is practicable and has a simple craftsmanship, moreover, it has the advantages of saving bandwidth and reducing cost.The numerical simulation of the FBG sensing performance of temperature and strain is analyzed. Theoretical rules for practical application of fiber Bragg grating sensors is provided in the paper. The affecting of structural parameters of fiber Bragg grating to the temperature and strain sensing performance of uniform grating, chirped grating and apodized grating is discussed by simulation analysis. The study specifically focuses on the impact and relationship of the grating length, the chirp coefficient, refractive index modulation to grating reflectivity, side-mode suppression ratio and 3dB-Bandwidth, as well as provides a reference rules for choosing a best fiber grating sensor in different applications.