A kind of high-birefringence polarization-maintaining(PM) photonic crystal fiber(PCF) is analyzed by introducing two big air holes near the core.The optimization scheme of PM-PCFs is presented by means of adjusting the sizes of the larger holes and the smaller holes.The polarization properties and mode field distributions of this fiber are analyzed by utilizing the finite element method(FEM).The results indicate that the mode birefringence is highly improved by the selective filling method,and i...