| Weak fiber Bragg grating sensors are widely used for temperature and stress measurement in tunnel fire warning,large building structure health monitoring,substation intrusion warning and other fields because of their special sensing characteristics.Weak fiber Bragg grating(FBG)is an important part of large-scale sensor networks,and its quality directly affects the performance of large-scale sensor networks.Due to the influence of shadow effect,external environment and other factors,the spectrometer detection method has great limitations,and can not detect large-scale fiber Bragg grating sensor arrays in real time.Because the quality detection system of large-scale fiber Bragg grating sensor arrays is not perfect and the evaluation criteria of spectral distortion are different,it is difficult to quickly analyze the quality of fiber Bragg grating sensor arrays.If the grating array has serious quality problems,it will not only affect the project progress,but also lead to significant economic losses and disasters.Therefore,it is necessary to analyze the quality of fiber Bragg grating sensor array quickly and systematically.In this paper,the quality analysis of fiber Bragg grating sensor array is mainly based on the grating spectrum,and the factors causing spectral distortion are analyzed and simulated.Fiber Bragg grating quality evaluation system is designed to realize rapid and accurate demodulation and spectrum recognition.Firstly,in view of the characteristics of inconsistent reflectance between the front end and the end of the large-capacity fiber Bragg grating sensor network,the factors causing the inconsistent reflectance are explored.An adaptive optical power compensation method is used to make the reflectance of the compensated fiber Bragg grating reflectance reach the same level.On this basis,the spectral quality analysis is carried out to explore.To avoid errors in spectral quality evaluation caused by inconsistent reflectance.Secondly,in order to solve the incomplete spectral quality evaluation system of fiber Bragg grating,this paper proposes to use threshold,spectral signal feature extraction and feature data calculation and comparison to gradually evaluate the quality from the aspects of reflection intensity,3DB bandwidth width,sidelobe rejection ratio,sag and main peak asymmetry,and then analyze the quality of the entire fiber Bragg grating sensor array.This evaluation system can cover all the characteristics of fiber Bragg grating spectrum and effectively complete the quality analysis of fiber Bragg grating spectrum.Finally,two kinds of fiber Bragg grating sensor arrays with different reflection intensity are used for experimental verification.The experimental results show that the optical power adaptive compensation can solve the problem of spectral reflectance inconsistency,and the evaluation system can identify the distorted fiber Bragg grating comprehensively and quickly,and record the distortion types,which is conducive to the processing and correction of different types of distortion,and the false detection rate is low. |
