In this paper

the properties of a new type of Total Internal Reflection Photonic Crystal Fiber（TIR-PCF） with two small elliptic air holes in the core are studies by using the Full Vectorial Effective Index Method（FVEIM）.The numerical results show that the difference between the refractive index in the core and the equivalent refractive index in the cladding increases with the wavelength

that the relative aperture of the air holes in the fixed cladding and the degeneracy of two orthonormal polarized modes of the PCF fundamental mode is removed

presenting a modal high birefringence

and that the modal birefringence increase and the total PCF dispersion curve becomes flattened with the increase of the ellipticity of the air holes.