Performance Analysis And Study Of Fiber Bragg Gratings Sensor Based On Uniform Rectangular Cantilever Beam

Optical fiber Bragg gratings(FBG)sensing technology can realize long-distance,multi-parameter,large-scale networking and real-time monitoring.Therefore,it is widely used in military,industrial,agricultural and other fields.It is necessary to constantly design new sensor structures,develop new sensing methods,enhance sensor performance,and expand application fields to meet the rapid development of high-tech in modern society.In most practical applications,the strain in the FBG length range is non-uniformly distributed,which seriously affects the performance of the sensor and even causes the sensor to fail.Therefore,it is meaningful to study the FBG sensing characteristics under non-uniform strain distributions and study the FBG sensors structure and sensing method based on the non-uniform strain distributions.After deeply studying the research status and sensing principle of FBG sensing technology,this paper has carried out the analysis and research on the sensing performance of FBG sensors based on uniform rectangular cantilever beam.Firstly,the expressions of the strain transfer rate and the average strain transfer rate of the surface FBG sensors were deduced.And the effects of the corresponding parameters on the transmissibility were analyzed in detail through simulation.Further simulation analysis indicates that the length and width of the intermediate layer should be increased as much as possible in the package to reduce the influence of the thickness on the average strain transfer rate,so as to improve the repeatability and consistency of the FBG sensors package results.These provides a solid theoretical basis for the improvement of the package technology and strain transfer error correction of the FBG sensors.Then,the non-uniform strain distributions is constructed by using laser cutting technology combined with uniform rectangular cantilever beam,and the sensing characteristics and deficiencies of uniform FBG and apodized FBG in non-uniform strain distribution were tested and analyzed.A displacement sensor based on two uniform FBG combined spectral bandwidth sensors was proposed to solve the problem of poor sensing linearity and low sensitivity of a single uniform FBG reflection spectrum bandwidth at any non-uniform strain distributions.Three kinds of displacement sensors with different laying positions are designed and implemented.The experimental measurements demonstrate the effectiveness of the combined spectral bandwidth sensing method in a variety of non-uniform strain distributions,and improve the linearity and sensitivity of the FBG sensors.Then,FBG displacement sensors based on apodized FBG center wavelength encoding with different non-uniform strain distributions are proposed.And a thorough analysis of the performance of different strain magnification structures is demonstrated.There is a positive and linear correlation between the displacement of the free end of the cantilever beam and the average strain of the FBG length.The correlation is used to calculate the displacement sensitivity and analyze the efficacy of the different strain magnification structures.The sensitivity enhancement factor is a reasonable agreement between simulation and experiment.The proposed method can be used to enhance the sensitivity of the FBG sensor and further improve the sensor structure design.Finally,the simulated annealing algorithm is improved,and the non-uniform strain distributions reconstruction technique based on the improved simulated annealing algorithm is proposed.The feasibility and effectiveness of the non-uniform strain distributions reconstruction technique of the FBG length based on the improved simulated annealing algorithm are proved through simulation experiments.And the linear non-uniform strain distribution reconstruction is realized.