| In recent years, the applications of fiber Bragg grating (FBG) has been attracted great attention in the field of optical sensing and communication. FBG sensor has the advantages of resistance to electromagnetic interference, big signal bandwidth, high sensitivity, easy multiplexing, light weight, compact conformation, easy for fiber connection, realizing wavelength absolute coding, linking many sensors into sensing network using various multiplexing technology, realizing multi-point monitoring to achieve its properties through embedding in the internal structure of materials, or adhibiting on the surface mount, etc. These sensors have extensive prospect in the security monitoring area of the special occasions, such as the large buildings and oil wells. In this paper, theoretical and experimental studies on spectra response of FBG were carried on in the sensing of the multi-mechanics parameters, which specifically includes:The establishment of FBG's reflected spectrum model was introduced based on coupled mold theory. The effect of correlation parameter on the reflected spectrum was analyzed. Embark on the phase matching condition of FBG, the detailed discussion was carried on based on axial homogenous strain, axial inhomogeneous strain, cross-sensitivity characteristic of temperature and strain. And the corresponding mathematical model was established.During the research process, the paper analyzes the spectra response of FBG under transverse force in detail. The reason that the reflected spectra of FBG split under transverse force, the stress relation of reflected spectra on the two polarization directions were discussed. At the same time, the characteristic of FBG under local transverse force were studied based on transfer matrix method. The spectrum split with the increase of local transverse force and the split point shift linearly and periodically. The relationship between the reflectivity and the position of stress is hyperbolic tangent. Moreover, the phase had certain relations. Based on this, the characteristic of FBG under inhomogeneous transverse force were studied. The characteristic of FBG under linear force, sinusoidal force and conic force were discussed, respectively. The relation between parameters of transverse force and bandwidth, symmetrical wavelength of spectra were deduced, and the corresponding mathematical model was established. The application prospect and the vital significance were discussed in the field of optical sensing and fiber component, through analysis on the characteristic of FBG under transverse load.Study on the characteristic of twisted HiBi fiber grating is one of the most important parts of the subject study. The paper analyzes the spectra response of twisted HiBi fiber grating. Based on the characteristic of twisted HiBi fiber and coupled mold theory of FBG, the coupled equation of twisted HiBi fiber grating is proposed and proved by transfer matrix method. The study indicates that the center wavelength of FBG's reflected spectrum on the two polarization directions shift, and the reflectivity decreased with the increase of the twist angle. The longer wavelength produces"red shift". The shorter wavelength produces"blue shift". And the wavelength shift is basically same. At the same time, a new resonance peak is produced in the reflected spectrum. Its peak wavelength is 1/2 of the sum of two FBG's center wavelengths. The relation between peak reflectivity and twist angle is tangent. Through characteristic analysis on the twisted fiber grating, the application value is discussed in the field of fiber-optic torsion sensing.Considering the characteristics of FBG's reflected spectrum under the different condition, the conception of analysis on characteristic of FBG's reflected spectrum using the ant colony algorithm is proposed. Through establishment of the ant colony algorithm model and design of the programs, the corresponding objective functions were established respectively to the response of FBG under axial strain and the transverse force, and the theoretical simulation experiment had been carried on. The effects on optimizing of the reflected spectrum were studied in detail based on various parameters of algorithm. And stability, astringency and accuracy of the algorithm were discussed.Based on the above research, the multi-mechanics parameters sensing experiment system of FBG has been designed, and the software of the data acquisition, processing and the simple spectrum analysis has been established. Using this system the experiments were carried on respectively to FBG under the axial strain, the transverse strain and the twisted action. The corresponding experimental data and the spectrum were gained. The comparison between the experimental data and theoretical analysis was given. And the theory had been confirmed accuracy. At the same time, we carried on the optimization to experimental result of FBG under transverse load using ant colony algorithm, obtained a more precise result, and proved the feasibility of the algorithm.
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