[2] [2] LEE Y W, HAN K J, LEE B, et al. Polarization independent all fiber multiwavelength-switchable filter based on a polarization-diversity loop configuration[J]. Opt Express, 2003, 11(25): 3359-3364.

[3] [3] XU Z, LI X, LING W, et al. Design of short polarization splitter based on dual-core photonic crystal fiber with ultra-high extinction ratio[J]. Optics Communications, 2015, 354: 314-320.

[4] [4] FANG L, WANG J. All-fiber polarization beam splitting and rotating based on vector-mode-assisted coupling[J]. Optics express, 2018, 26(12): 15124-15137.

[5] [5] SNYDER A W, STEVENSON A J. Polished-type couplers acting as polarizing beam splitters[J]. Optics Letters, 1986, 11(4): 254-256.

[6] [6] KNIGHT J C, BIRKS T A, RUSSELL P S J, et al. All-silica single-

[8] [8] CHEN D, WU G. Highly birefringent photonic crystal fiber based on a double-hole unit[J]. Applied optics, 2010, 49(9): 1682-1686.

[13] [13] SHENG Z, WANG J, FENG R. Design of a compact polarization splitter based on the dual-elliptical-core photonic crystal fiber[J]. Infrared Physics & Technology, 2014, 67: 560-565.

[17] [17] RAJESWARI D, RAJA A S, SELVENDRAN S. Design and analysis of polarization splitter based on dual-core photonic crystal fiber[J]. Optik, 2017, 144: 15-21.

[18] [18] HE F, SHI W, HUI Z, et al. A dual-core PCF polarization splitter with five elliptical air holes based on tellurite glass[J]. Optical and Quantum Electronics, 2017, 49(11): 363.1-363.10.

[19] [19] JEGADEESAN S, DHAMODARAN M, AZEES M, et al. Design of a Polarization Splitter Based on a Dual-core Hexagonal-shaped Photonic Crystal Fiber[J]. Current Optics and Photonics, 2019, 3(4): 304-310.

[21] [21] ZHANG S, ZHANG W, GENG P, et al. Design of single-polarization wavelength splitter based on photonic crystal fiber[J]. Applied optics, 2011, 50(36): 6576-6582.

[22] [22] CUCINOTTA A, SELLERI S, VINCETTI L, et al. Perturbation analysis of dispersion properties in photonic crystal fibers through the finite element method [J]. J lightwave Technol. 2002, 20: 1433-1442.

[23] [23] ROSA L, POLI F, FORONI M, et al. Polarization splitter based on a square-lattice photonic crystal fiber[J]. Opt. Lett., 2006, 31(4): 441-443.

[24] [24] LU W, LOU S, WANG X. Ultrabroadband polarization splitter based on a modified three-core photonic crystal fiber[J]. Applied optics, 2013, 52(35): 8494-8500.