Spectral Characteristics Of Tilted Fiber Bragg Grating In Anisotropic Media

As a special kind of fiber gratings,Tilted Fiber Bragg Grating(TFBG) has shown great potential and advantages in both optical fiber sensing and optical communication field.In this paper, the spectrum of TFBG is studied.And software such as Matlab,Opti Grating and Rsoft have been used to simulate the spectrum of TFBGs with different structures as well as TFBGs in different environmental medias.The main contents of this paper are:1.The development, classification and application of optical fiber gratings are introduced.And then followed by the introduction, research status and application of tilted fiber grating.2.By using the Coupled Mode Theory and the Volume Current Method, the Bragg mode transmission spectrum as well as the cladding modes and the radiation modes spectrum of the tilted fiber gratings are analyzed.Reflectivity of the core fundamental modes and the expressions of the Bragg reflection wavelength are calculated.Also,the reflectivity expressions of cladding modes and radiation modes are derived.3.The analysis and simulation of TFBGs with different structures in isotropic medium are presented.In this section,TFBGs are divided into two categories:2-structure-TFBG and 3-structure-TFBG.The influence of the structure parameters such as the tilt angle, the thickness of the cladding and the refractive index of the core on both TFBGs’ spectrum are analyzed.After that,this paper presented the the analysis and simulation of the influence of the refractive index change of tilted fiber grating spectrum.The results showed that when 3-structure-TFBG is used as a refractive index sensor,it’s sensitivity can reach 10-5.4.The analysis and simulation of the FBG’s spectrum characteristics in anisotropic medium are presented.Results showed that the Principal Refractive Indices(kcl) of the anisotropic media has an influence on the spectrum.Also,A new feature was found that the spectrum of FBG will change dramatically when the kcl reaches about 1.By using this new feature,designed an electro-optic switch with extinction ratio of up to 42.32 d B.The analysis and simulation of the spectral characteristics of TFBG in anisotropic medium are presented.It is found that when the kcl is changed in the vicinity of 1, the core fundamental modes and the radiation modes of the TFBG have completely opposite switching characteristics.At the end of this paper,analysis and simulation of the resonance wavelength changes of TFBG are presented by changing the kcl as well as the tilt angle.