The six-fold symmetry of photonics crystal fibers (PCFs) is destroyed by defecting triple adjacent air holes in the core region to form elliptical core in theory, the two orthogonal polarized states of the fundamental mode become non-degeneration, the mode field is strongly linear polarization and appear an ellipse. According to the theoretical model, the elliptical core five ring hexangular structure polymer photonics crystal fiber(PCF) with diameter of 150 μm, average hole-diameter of 3.94 μm, and average holes spacing of 8.75 μm is fabricated successfully based on poly methyl methacry-late (PMMA). The full-vectorial plane-wave method is applied to simulate the mode fields of fabricated fiber. From symmetry analysis of waveguide modes, the guided modes are classified in the elliptical core polymer photonics crystal fiber by adopting the minimum waveguide sector and its corresponding boundary conditions and are compared with analysis of theory. The research offer a basis for the mode fields experiment of elliptical core polymer PCF and provide a possibility to manufacture high birefringence polarization maintaining fiber based on polymer.

guided wave optics; photonics crystal fiber（PCF）; elliptical core; polymer