A novel ultra-broadband polarization splitter based on dual-core photonic crystal fiber (DC-PCF) is designed. The full-vector finite element method (FEM) and coupled-mode theory are employed to investigate the characteristics of the polarization splitter. According to the numerical results, graphene-filled layer can not only broaden the working bandwidth but also reduce the size of polarization splitter. Furthermore, the fluorine-doped region and the germanium-doped region could broaden the bandwidth. Apart from that, the 4.78-mm-long polarization splitter can achieve an extinction ratio of -98.6 dB at the wavelength of 1550 nm. When extinction ratio is less than -20 dB, the range of the wavelength is 1027-1723 nm with a bandwidth of 696 nm. Overall, the polarization splitter can be applied to all-optical network communication system in the infrared and near-infrared wavelength range.

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