To meet the application requirements of high birefringence in optical fiber communication and sensing system

a new Photonic Crystal Fiber（PCF） is proposed in this paper.The designed structure is hexagonal

which is arranged by circular air holes. The inner cladding is designed as four elliptical air holes and two small round air holes. By applying full-vector finite-element method and changing the ellipticity and the size of small round air holes

we investigate the effective refractive index

high birefringence

nonlinear coefficient and dispersion characteristic of the fiber. The simulation results show that when the ellipticity is 0.5 and the diameter of small round hole is 0.8 μm

a high birefringence of 4.22×10

-2

a high nonlinear coefficient of 109.65 km

-1

·W

-1

and a dispersion value as low as-14 ps/（nm·km） can be obtained at 1 550 nm. The PCF proposed in this paper has high birefringence and high nonlinearity

which can be applied in the optical switch field and provide the theoretical basis for the research of optical communication and optical fiber sensing.