Research On Transmission Characteristics And Application Of The Single Phase-Shifted Fiber Bragg Grating

With the advancement of technology and the deepening of research and the needs of applications,fiber gratings with different structures and different functions have been produced.Phase-shifted fiber grating was inserted one or more phased-shifts in a uniform fiber grating,so that its transmission spectrum forms single or multiple phase-shift peaks with extreme narrow line widths,which has attracted extensive attention in the field of WDM systems,fiber sensing,narrow linewidth laser an so on.In this paper,we firstly introduce the development,classification and applications of fiber Bragg grating by reading lots of references.On this basis,we introduce phase-shifted fiber grating and its characteristics and applications was also introduced minutely in various fields.Then the couple-mode theory was used to analyze the transmission characteristics of the uniform fiber grating,and the reflectivity and transmission equation of phase-shifted fiber grating was analyzed minutely based on the coupled-mode theory with an the transfer matrix method.According to the transfer matrix method and control variable method,the transmission spectrum of single phase-shifted fiber grating was simulated by Matlab,the transmission spectrum of single phase-shifted fiber grating was analyzed including the magnitude of different phase-shifted?different location of phase-shifted?different lengths of fiber grating and different refractive index of the core and obtained the main factors of affecting transmittance of the phase-shifted peak?linewidth of the phase-shifted peak?position of the phase-shifted peak.These conclusions have important value for the making,of single phase-shifted fiber grating.Then analysis of temperature and strain sensing theory of single phase-shifted fiber grating.Based on this,designed experiments on temperature and s strain sensing of single phase-shifted fiber gratings.Through experimental analysis,it can be obtained the single phase-shifted fiber temperature sensitivity was 10.65 pm/~oC and sensitivity strain was 0.12 pm/u?and the transmission spectrum had good stability.So,single phase-shifted fiber gratings had prosperous application in the field of sensing.Finally,According to the good filtering and temperature sensing characteristics of single phase-shifted fiber grating proposed a tunable narrow linewidth erbium-doped fiber laser using a ring cavity structure.Experiment showed that the output of the unimodal laser was obtained,the range of temperature was from25~oC to 85~oC,wavelength of laser adjustable range of 0.7nm,threshold power was 43mW,linewidth was 0.01nm,and the maximum output power was 300uW.Meanwhile,the stability output of laser was tested,result show that the maximum fluctuation range of the output power was 0.26dB,showing it had fine stability.Meanwhile,the optimization analysis of the whole system was discussed in detail and various factors affecting the output of the laser were analyzed.The optimum length of EDF and the fit output couple-ration were gained,which laid the foundation for the actual fabrication of the fiber laser.