Research On Optical Fiber And Fiber Gratings With Anisotropic Crystal Cladding

The power confinement factor of the fiber with cladding made of uniaxial crystal material whose optical axis is parallel to the axis of fiber were investigated by means of numeric solution, Influence of strain field on the wave-guide efficiency ofthe fiber with cladding. The ratio( k_cl) of the extraordinary to the ordinary ray indexwas introduced. The characteristic equation of the ideal normal mode was studied. The cut-off characteristic of fundamental mode and the influence parameter k_cl uponthe reflectivity of this kind of fiber Bragg grating were examined by using the coupled-mode theory., and the influence of k_cl on the reflectivity of this kind offiber Bragg gratings was physical interpreted with modal characteristics. The calculated results indicate that the strain has a strong impact on the power distribution of this kind of fiber, and with its gradually increasing, the optical energy was gradually concentrated into the core, for HE₁₁ mode, more power is transmitted by the core of the fiber with cladding made of isotropic material than that with claddingmade of uniaxial crystal material and the degree is dependence on the parameter k_cl,the reflectivity of the fiber Bragg grating with cladding made of uniaxial crystal material is much higher than that with cladding made of isotropic material, the reflectivity of this kind of fiber Bragg grating is greatly influenced by the energy distribution between the core and the cladding of this kind of the fiber. The research results provide an important theoretic basis for new application of designing new-style strain sensors and fiber Bragg grating in sensing and measurement technology.