[1] Padgett M J. Orbital angular momentum 25 years on[J]. Optics Express, 2017, 25(10): 11265-11274.
[3] Ramachandran S, Kristensen P, Yan M F. Generation and propagation of radially polarized beams in optical fibers[J]. Opt. Lett., 2009, 34(16): 2525-2527.
[4] Bozinovic N, Kristensen P, Ramachandran S. Long-range fiber-transmission of photons with orbital angular momentum[C]// IEEE Lasers & Electro-optics, 2011: 1188-1189.
[5] Bozinovic N, Yue Y, Ren Y, et al. Terabit-scale orbital angular momentum mode division multiplexing in fibers[J]. Science, 2013, 340(6140): 1545-1548.
[8] Zhang L, Zhang K, Peng J, et al. Circular photonic crystal fiber supporting 110 OAM modes[J]. Optics Communications, 2018, 429: 189-193.
[11] Wang W, Sun C, Wang N, et al. A design of nested photonic crystal fiber with low nonlinear and flat dispersion supporting 30+50 OAM modes[J]. Optics Communications, 2020, 471: 125823.
[12] Lei Y, Xu X, Wang N, et al. Numerical analysis of a photonic crystal fiber for supporting 76 orbital angular momentum modes[J]. J. of Optics, 2018, 20(10): 105701.
[13] Wang A, Du C, Zhu G, et al. 18km low-crosstalk OAM+WDM transmission with 224 individual channels enabled by a ring-core fiber with large high-order mode group separation[J]. Opt. Lett., 2018, 43(8): 1890-1893.
[14] Wang H, Liang Y, Zhang X, et al. Low-loss orbital angular momentum ring-core fiber: design, fabrication and characterization[J]. J. of Lightwave Technol., 2020, 38(22): 6327-6333.
[16] Bozinovic N, Golowich S, Kristensen P, et al. Control of orbital angular momentum of light with optical fibers[J]. Opt. Lett., 2012, 37(13): 2451-2453.
[17] Brunt C, Ung B, Belanger P A, et al. Vector mode analysis of ring-core fibers: design tools for spatial division multiplexing[J]. J. of Lightwave Technol., 2014, 32(23): 4648-4659.
[18] Gregg P, Kristensen P, Golowich S, et al. Stable transmission of 12 OAM states in air-core fiber[C]// Cleo. IEEE, 2013: 1-2.
[19] Gregg P, Kristensen P, Ramachandran S. Conservation of orbital angular momentum in air-core optical fibers[J]. Optica, 2015, 4(9): 1115-1116.
[20] Ramachandran S, Gregg P, Kristensen P, et al. On the scalability of ring fiber designs for OAM multiplexing[J]. Opt. Express, 2015, 23(3): 3721-3730.
[21] Ung B, Vaity P, Wang L, et al. Few-mode fiber with inverse-parabolic graded-index profile for transmission of OAM-carrying modes[J]. Opt. Express, 2014, 22(15): 18044-18055.
[22] Brunet C, Vaity P, Messaddeq, et al. Design, fabrication and validation of an OAM fiber supporting 36 states[J]. Opt. Express, 2014, 22(21): 26117-26127.
[23] Brunet C, Ung B, Messaddeq Y, et al. Design of an optical fiber supporting 16 OAM modes[C]// IEEE Optical Fiber Communication Conf., 2014.
[25] Zhu M, Zhang W, Xi L, et al. A new designed dual-guided ring-core fiber for OAM mode transmission[J]. Optical Fiber Technol., 2015, 25: 58-63.
[26] Li S, Wang J. Multi-orbital-angular-momentum multi-ring fiber for high-density space-division multiplexing[J]. IEEE Photonics J., 2013, 5(5): 7101007.
[27] Li S, Wang J. A compact trench-assisted multi-orbital-angular-momentum multi-ring fiber for ultrahigh-density space-division multiplexing (19 rings×22 modes)[J]. Scientific Reports, 2014, 4(1): 3853.
[28] Ye Jingfu, Yan, et al. Excitation and separation of vortex modes in twisted air-core fiber[J]. Opt. Express, 2016, 24(8): 8310-8316.
[29] Zhang Z, Liu X, Wei W, et al. The simulation of vortex modes in twisted few-mode fiber with inverse-parabolic index profile[J]. IEEE Photonics J., 2020, 12(3): 1-8.
[30] Li S, Wang J. Supermode fiber for orbital angular momentum (OAM) transmission[J]. Opt. Express, 2015, 23(14): 18736-18745.
[31] Wang W, Xu H D, Yang Q H, et al. Large mode area microstructured fiber supporting 56 super-OAM modes[J]. Opt. Express, 2019, 27(20): 27991-28008.
[34] Wong, KI G. Excitation of orbital angular momentum resonances in helically twisted photonic crystal fiber[J]. Science, 2012, 337(6093): 446-449.
[35] Haisu L, Guobin R, Bofeng Z, et al. Guiding terahertz orbital angular momentum beams in multimode kagome hollow-core fibers[J]. Opt. Lett., 2017, 42(2): 179-182.
[37] Liu E, Tan W, Yan B, et al. Robust transmission of orbital angular momentum mode based on a dual-cladding photonic quasi-crystal fiber[J]. J. of Phys. D: Appl. Phys., 2019, 52(32): 325110.
[39] Zhang H, Zhang W, Xi L, et al. A new type circular photonic crystal fiber for orbital angular momentum mode transmission[J]. IEEE Photon. Technol. Lett., 2016, 28(13): 1426-1429.
[40] Zhang H, Zhang X G, Li H, et al. A design strategy of the circular photonic crystal fiber supporting good quality orbital angular momentum mode transmission[J]. Optics Communications, 2017, 397: 59-66.
[41] Tian W, Zhang H, Zhang X G, et al. A circular photonic crystal fiber supporting 26 OAM modes[J]. Optical Fiber Technol., 2016, 30: 184-189.
[42] Zhou G, Zhou G, Cheng C, et al. Design and analysis of a microstructure ring fiber for orbital angular momentum transmission[J]. IEEE Photonics J., 2017, 8(2): 1-12.
[43] Hu Z A, Huang Y Q, Luo A P, et al. Photonic crystal fiber for supporting 26 orbital angular momentum modes[J]. Opt. Express, 2016, 24(15): 17285-17291.
[44] Chen C, Zhou G, Zhou G, et al. A multi-orbital-angular-momentum multi-ring micro-structured fiber with ultra-high-density and low-level crosstalk[J]. Opt. Communications, 2016, 368: 27-33.
[45] Xu M, Zhou G, Chen C, et al. A novel micro-structured fiber for OAM mode and LP mode simultaneous transmission[J]. J. of Optics, 2018, 47(4): 428-436.
[46] Wang N, Xie J L, Jia Hongzhi, et al. A low confinement loss double-photonic crystal fibre over 850nm bandwidth with 26 orbital angular momentum modes transmission[J]. J. of Modern Optics, 2018, 65(18): 2060-2066.
[47] Wang W, Wang N, Li K, et al. A novel dual guided modes regions photonic crystal fiber with low crosstalk supporting 56 OAM modes and 4 LP modes[J]. Optical Fiber Technol., 2020, 57: 102213.
[52] Hassan M M, Kabir M A, Hossain M N, et al. Photonic crystal fiber for robust orbital angular momentum transmission: design and investigation[J]. Optical and Quantum Electron., 2020, 52(1): 1-14.