Basic Researches Of Grating Writting And Applications Based On Chalcogenide And Tellurite Fibers

Fiber Bragg gratings(FBGs) have extensive applications in optical fiber communication and fiber sensing etc.Compared with conventional sensors,the sensors based on FBGs have a lot of advantages,including small size and high precision.Besides,compared with conventional resonant cavities,the cavities based on FBGs have realized all-fiber structure.The stable and accurate frequency-selecting characteristics of FBGs improve the stability of lasers,and increase the output power and efficiency.This dissertation analyses the diffraction field used to manufacture FBGs based on the phase mask method,which could provide theoretical directions for experimental inscription.The sensitivity of mid-infrared waveband FBGs inscribed in soft glass fibers(chalcogenide and tellurite fiber)to variations of temperature,strain and pressure is deeply analyzed.Using FBGs as the resonant cavities of mid-infrared waveband Raman fiber lasers(RFLs),optimal design of Raman laser parameters is realized by numerical simulation.The main contents of this dissertation are as follows:Firstly,the physical model of FBG writing based on the phase mask method is established and analyzed using the finite element method(FEM).The diffracted light field by the phase mask is analyzed and compared by changing the light source types(plane wave or spherical wave),incident direction and the groove depth of the phase mask.Diffraction patterns are gained under different conditions.And optimized conditions for the inscription of FBGs are proposed.Secondly,according to Bragg formulas,the sensitivity characteristics of mid-infrared FBGs based on chalcogenide fibers,tellurite fibers and other fibers are analyzed.The characteristic curves of Bragg wavelength changing with temperature,strain and pressure are numerically simulated.Then considering the above analysis,the basic characteristics and advantages of FBGs in infrared sensing applications are analyzed.Thirdly,based on coupling transmission equations of stimulated Raman scattering(SBS),the characteristics of pump light and Stokes lights,in chalcogenide RFL and tellurite RFL,are analyzed by FEM and shooting method.By numerical simulation,the affect on output performance of RFL caused by the variation of pump power,fiber length and reflectivity at output is investigated.Finally optimization parameters of first-order and second-order mid-infrared RFLs are presented.