[1] C BRUNET, L A RUSCH. Optical fibers for the transmission of orbital angular momentum modes. Optical Fiber Technology, 31, 172-177(2016).

[2] R S SOFANA, D TOMISLAV, P SIANO. Future generation 5G wireless networks for smart grid:a comprehensive review. Energies, 12, 1-17(2019).

[3] M PRASHANT. Trends inoptical fibre communication. Academic Journal of Physical Sciences, 1, 7-12(2019).

[5] A E WILLNER, Hao HUANG, Y YAN. Optical communications using orbital angular momentum beams. Advances in Optics and Photonics, 7, 66-106(2015).

[6] An-dong WANG, Cheng DU, Guo-xuan ZHU. 18 km low-crosstalk OAM+WDM transmission with 224 individual channels enabled by a ring-core fiber with large high-order mode group separation. Optics Letters, 43, 1890-1893(2018).

[7] Yi-fan DENG, Hu ZHANG, Hui LI. Erbium-doped amplification in circular photonic crystal fiber supporting orbital angular momentum modes. Applied Optics, 56, 1748-1752(2017).

[8] Jian WANG, M J PADGETT, S RAMACHANDRAN. Multimode communications using orbital angular momentum. Optical Fiber Telecommunications, 12, 569-615(2013).

[9] N BOZINOVIC, Yang YUE, Yong-xiong REN. Terabit-scale orbital angular momentum mode division multiplexing in fibers. Science, 340, 1545-1548(2013).

[10] C BRUNET, P VAITY, , . Design, fabrication and validation of an OAM fiber supporting 36 states. Optics Express, 22, 26117-26127(2014).

[11] C BRUNET, B UNG, Li-xian WANG. Design of a family of ring-core fibers for OAM transmission studies. Optics Express, 23, 10553-10563(2015).

[12] [12] SUN Xibo, GENG Yuanchao, ZHU Qihua, et al. Edgedip air ce fiber f improvement of the transmission of higherder OAM modes[C]. SPIE, 2018, 10710: 107103E.

[13] Hai-su LI, Guo-bin REN, Yu-dong LIAN. Broadband orbital angular momentum transmission using a hollow-core photonic bandgap fiber. Optics Letters, 41, 3591-3594(2016).

[14] Shu-hui LI, Jian WANG. A compact trench-assisted multi-orbital-angular-momentum multi-ring fiber for ultrahigh-density space-division multiplexing(19rings×22modes). Scientific Reports, 4, 3853(2014).

[15] Guang-hao SHAO, Shao-cheng YAN, Wei LUO. Orbital angular momentum (OAM) conversion and multicasting using N-core supermode fiber. Scientific Reports, 7, 1062(2017).

[16] Wei WANG, Hai-dong XU, Qi-hao YANG. Large mode area microstructured fiber supporting 56 super-OAM modes. Optics Express, 27, 27991-28008(2019).

[17] S ALESSIO, C F SIMON, T K BORIS. Terahertz orbital angular momentum modes with flexible twisted hollow core antiresonant fiber. Applied Photonics, 3, 051708(2018).

[18] Hu ZHANG, Xiao-guang ZHANG, Hui LI. A design strategy of the circular photonic crystal fiber supporting good quality orbital angular momentum mode transmission. Optics Communications, 397, 59-66(2017).

[19] Hu ZHANG, Xiao-guang ZHANG, Hui LI. The orbital angular momentum modes supporting fibers based on the photonic crystal fiber structure. Crystals, 7, 286(2017).

[20] T ARSōNE, Y JEAN, D MICHEL. Ring-core photonic crystal fiber for propagation of OAM modes. Optics Letters, 44, 1611-1614(2019).

[21] Jia-jing TU, Zheng-yong LIU, She-cheng GAO. Ring-core fiber with negative curvature structure supporting orbital angular momentum modes. Optics Express, 27, 20358-20372(2019).

[22] Yuan YUAN, De-peng KONG, Li-li WANG. A hollow ring-core polymer optical fiber for supra-high bandwidth data communication. Optics Communications, 441, 176-184(2019).

[23] Yue YANG, Yan YAN, N AHMED. Mode properties and propagation effects of optical orbital angular momentum (OAM) modes in a ring fiber. IEEE Photonics Journal, 4, 535-543(2012).

[24] Si CHEN, Jian WANG. Theoretical analyses on orbital angular momentum modes in conventional graded-index multimode fibre. Scientific Reports, 7, 3990(2017).

[25] , OL ER. Optical fibers with high-index-contrast dielectricthin films. Optical Engineering, 45, 105006(2006).

[26] Li-li ZHANG, Xia ZHANG, Cheng-lin BAI. Study on the effect of ellipticity and misalignment on OAM modes in a ring fiber. Optoelectronics Letters, 14, 50-54(2018).

[27] Zhi-shen ZHANG, Jiu-lin GAN, Xiao-bo HENG. Optical fiber design with orbital angular momentum light purity higher than 99%. Optics Express, 23, 29331-29341(2015).

[28] [28] WANG Lixian, CSI A, RUSH L, et al. Investigation of bital angular momentum mode purity in airce optical fibers[C]. IEEE, 2016: 203204.https:www.researchgate.publication308082089_Investigation_of_bital_angular_momentum_mode_purity_in_airce_optical_fibers