In view of such disadvantages as high material loss

complexity of preparation processes

and poor transmission performances and output beam qualities in ordinary infrared fibers

a new type of large core infrared Photonic Band Gap Photonic Crystal Fiber（PBG-PCF） is presented

which is appropriate for CO2 laser transmission.The large core of such a fiber is produced by removing 19 capillary air holes from the center of photonic crystals with triangular lattice.A fiber bandgap figure of CO2 laser at a transmission wavelength of 10.6 μm is first obtained by PWM analysis and then

its loss characteristics are analyzed by using the simulation software COMSOL Multiphysics based on the full vector finite element method.The results show that the new photonic crystal fiber has smaller loss

about 0.08dB/km

in 10.6 μm CO2 laser transmission than the existing infrared fibers

satisfying the needs of high power CO2 laser transmissions for medical applications.