[1] R.-J. Essiambre, R. W. Tkach. Capacity trends and limits of optical communication networks. Proc. IEEE, 100, 1035-1055(2012).

[2] R. S. Romaniuk. Multicore optical fibers. Rev. Roum. Phys., 32, 99-112(1987).

[3] K. Saitoh, S. Matsuo. Multicore fiber technology. J. Lightwave Technol., 34, 55-66(2016).

[4] S. Berdague, P. Facq. Mode division multiplexing in optical fibers. Appl. Opt., 21, 1950-1955(1982).

[5] N. Bozinovic, Y. Yue, Y. Ren, M. Tur, P. Kristensen, H. Huang, A. E. Willner, S. Ramachandran. Terabit-scale orbital angular momentum mode division multiplexing in fibers. Science, 340, 1545-1548(2013).

[6] G. Li, N. Bai, N. Zhao, C. Xia. Space-division multiplexing: the next frontier in optical communication. Adv. Opt. Photonics, 6, 413-487(2014).

[7] D. J. Richardson, J. M. Fini, L. E. Nelson. Space-division multiplexing in optical fibres. Nat. Photonics, 7, 354-362(2013).

[8] B. J. Puttnam, G. Rademacher, R. S. Luís. Space-division multiplexing for optical fiber communications. Optica, 8, 1186-1203(2021).

[9] P. Sillard, M. Bigot-Astruc, D. Molin. Few-mode fibers for mode-division-multiplexed systems. J. Lightwave Technol., 32, 2824-2829(2014).

[10] A. Li, X. Chen, A. Al Amin, J. Ye, W. Shieh. Space-division multiplexed high-speed superchannel transmission over few-mode fiber. J. Lightwave Technol., 30, 3953-3964(2012).

[11] L. Allen, M. W. Beijersbergen, R. J. C. Spreeuw, J. P. Woerdman. Orbital angular-momentum of light and the transformation of Laguerre-Gaussian laser modes. Phys. Rev. A, 45, 8185-8189(1992).

[12] J. Wang, J.-Y. Yang, I. M. Fazal, N. Ahmed, Y. Yan, H. Huang, Y. Ren, Y. Yue, S. Dolinar, M. Tur, A. E. Willner. Terabit free-space data transmission employing orbital angular momentum multiplexing. Nat. Photonics, 6, 488-496(2012).

[13] J. Chen, C. Wan, Q. Zhan. Engineering photonic angular momentum with structured light: a review. Adv. Photonics, 3, 064001(2021).

[14] B. Ndagano, H. Sroor, M. McLaren, C. Rosales-Guzman, A. Forbes. Beam quality measure for vector beams. Opt. Lett., 41, 3407-3410(2016).

[15] J. Fang, Z. Xie, T. Lei, C. Min, L. Du, Z. Li, X. Yuan. Spin-dependent optical geometric transformation for cylindrical vector beam multiplexing communication. ACS Photonics, 5, 3478-3484(2018).

[16] G. C. G. Berkhout, M. P. J. Lavery, J. Courtial, M. W. Beijersbergen, M. J. Padgett. Efficient sorting of orbital angular momentum states of light. Phys. Rev. Lett., 105, 153601(2010).

[17] Y. H. Wen, I. Chremmos, Y. J. Chen, Y. F. Zhang, S. Y. Yu. Arbitrary multiplication and division of the orbital angular momentum of light. Phys. Rev. Lett., 124, 213901(2020).

[18] G. Ruffato, M. Massari, G. Parisi, F. Romanato. Test of mode-division multiplexing and demultiplexing in free-space with diffractive transformation optics. Opt. Express, 25, 7859-7868(2017).

[19] G. Labroille, B. Denolle, P. Jian, P. Genevaux, N. Treps, J.-F. Morizur. Efficient and mode selective spatial mode multiplexer based on multi-plane light conversion. Opt. Express, 22, 15599-15607(2014).

[20] N. K. Fontaine, R. Ryf, H. Chen, D. T. Neilson, K. Kim, J. Carpenter. Laguerre-Gaussian mode sorter. Nat. Commun., 10, 26(2019).

[21] J. Fang, J. Bu, J. Li, C. Lin, A. Kong, X. Yin, H. Luo, X. Song, Z. Xie, T. Lei, X. Yuan. Performance optimization of multi-plane light conversion (MPLC) mode multiplexer by error tolerance analysis. Opt. Express, 29, 37852-37861(2021).

[22] G. Ruffato, V. Grillo, F. Romanato. Multipole-phase division multiplexing. Opt. Express, 29, 38095-38108(2021).

[23] S. Matsuo, K. Takenaga, Y. Sasaki, Y. Amma, S. Saito, K. Saitoh, T. Matsui, K. Nakajima, T. Mizuno, H. Takara, Y. Miyamoto, T. Morioka. High-spatial-multiplicity multicore fibers for future dense space-division-multiplexing systems. J. Lightwave Technol., 34, 1464-1475(2016).

[24] S. Beppu, K. Igarashi, M. Kikuta, D. Soma, T. Nagai, Y. Saito, H. Takahashi, T. Tsuritani, I. Morita, M. Suzuki. Weakly coupled 10-mode-division multiplexed transmission over 48-km few-mode fibers with real-time coherent MIMO receivers. Opt. Express, 28, 19655-19668(2020).

[25] D. Soma, S. Beppu, Y. Wakayama, K. Igarashi, T. Tsuritani, I. Morita, M. Suzuki. 257-Tbit/s weakly coupled 10-mode C + L-band WDM transmission. J. Lightwave Technol., 36, 1375-1381(2018).

[26] J. Sakaguchi, W. Klaus, Y. Awaji, N. Wada, T. Hayashi, T. Nagashima, T. Nakanishi, T. Taru, T. Takahata, T. Kobayashi. 228-spatial-channel bi-directional data communication system enabled by 39-core 3-mode fiber. J. Lightwave Technol., 37, 1756-1763(2019).

[27] J. Zhang, G. Zhu, J. Liu, X. Wu, J. Zhu, C. Du, W. Luo, Y. Chen, S. Yu. Orbital-angular-momentum mode-group multiplexed transmission over a graded-index ring-core fiber based on receive diversity and maximal ratio combining. Opt. Express, 26, 4243-4257(2018).

[28] F. Z. Tan, W. M. Lyu, S. Y. Chen, Z. Y. Liu, C. Y. Yu. Contactless vital signs monitoring based on few-mode and multi-core fibers. Opto-Electron. Adv., 3, 190034(2020).

[29] G. Rademacher, B. J. Puttnam, R. S. Luis, J. Sakaguchi, W. Klaus, T. A. Eriksson, Y. Awaji, T. Hayashi, T. Nagashima, T. Nakanishi, T. Taru, T. Takahata, T. Kobayashi, H. Furukawa, N. Wada. Highly spectral efficient C plus L-band transmission over a 38-core-3-mode fiber. J. Lightwave Technol., 39, 1048-1055(2021).

[30] D. Soma, Y. Wakayama, S. Beppu, S. Sumita, T. Tsuritani, T. Hayashi, T. Nagashima, M. Suzuki, M. Yoshida, K. Kasai, M. Nakazawa, H. Takahashi, K. Igarashi, I. Morita, M. Suzuki. 10.16-peta-b/s dense SDM/WDM transmission over 6-mode 19-core fiber across the C plus L band. J. Lightwave Technol., 36, 1368-1375(2018).

[31] W. Klaus, J. Sakaguchi, B. J. Puttnam, Y. Awaji, N. Wada, T. Kobayashi, M. Watanabe. Free-space coupling optics for multicore fibers. IEEE Photonics Technol. Lett., 24, 1902-1905(2012).

[32] N. Lindenmann, S. Dottermusch, M. L. Goedecke, T. Hoose, M. R. Billah, T. P. Onanuga, A. Hofmann, W. Freude, C. Koos. Connecting silicon photonic circuits to multicore fibers by photonic wire bonding. J. Lightwave Technol., 33, 755-760(2015).

[33] V. I. Kopp, J. Park, J. Singer, D. Neugroschl, A. Gillooly. Low return loss multicore fiber-fanout assembly for SDM and sensing applications. Optical Fiber Communication Conference (OFC), M2C.3(2020).

[34] N. Riesen, S. Gross, J. D. Love, Y. Sasaki, M. J. Withford. Monolithic mode-selective few-mode multicore fiber multiplexers. Sci. Rep., 7, 6971(2017).

[35] Q. Huang, Y. Wu, W. Jin, K. S. Chiang. Mode multiplexer with cascaded vertical asymmetric waveguide directional couplers. J. Lightwave Technol., 36, 2903-2911(2018).

[36] H. Chen, N. K. Fontaine, R. Ryf, B. Guan, S. J. Ben Yoo, T. Koonen. Design constraints of photonic-lantern spatial multiplexer based on laser-inscribed 3-D waveguide technology. J. Lightwave Technol., 33, 1147-1154(2015).

[37] Z. Xie, S. Gao, T. Lei, S. Feng, Y. Zhang, F. Li, J. Zhang, Z. Li, X. Yuan. Integrated (de)multiplexer for orbital angular momentum fiber communication. Photonics Res., 6, 743-749(2018).

[38] L. W. Chen, Y. M. Yin, Y. Li, M. H. Hong. Multifunctional inverse sensing by spatial distribution characterization of scattering photons. Opto-Electron. Adv., 2, 19001901(2019).

[39] X. Lu, Y. Shao, C. Zhao, S. Konijnenberg, X. Zhu, Y. Tang, Y. Cai, H. P. Urbach. Noniterative spatially partially coherent diffractive imaging using pinhole array mask. Adv. Photon., 1, 016005(2019).

[40] C. Jin, M. Afsharnia, R. Berlich, S. Fasold, C. Zou, D. Arslan, I. Staude, T. Pertsch, F. Setzpfandt. Dielectric metasurfaces for distance measurements and three-dimensional imaging. Adv. Photonics, 1, 036001(2019).

[41] X. Chen, Z. Fu, Q. Gong, J. Wang. Quantum entanglement on photonic chips: a review. Adv. Photonics, 3, 064002(2021).

[42] D. Tan, Z. Wang, B. Xu, J. Qiu. Photonic circuits written by femtosecond laser in glass: improved fabrication and recent progress in photonic devices. Adv. Photonics, 3, 024002(2021).

[43] D. Z. Tan, B. Zhang, J. R. Qiu. Ultrafast laser direct writing in glass: thermal accumulation engineering and applications. Laser Photonics Rev., 15, 2000455(2021).

[44] Y. C. Jia, S. X. Wang, F. Chen. Femtosecond laser direct writing of flexibly configured waveguide geometries in optical crystals: fabrication and application. Opto-Electron. Adv., 3, 190042(2020).

[45] F. J. Mustieles, E. Ballesteros, P. Baquero. Theoretical S-bend profile for optimization of optical wave-guide radiation losses. IEEE Photonics Technol. Lett., 5, 551-553(1993).

[46] V. Kumar, V. Priye. 3-D multilayer S-bend silicon waveguide optical interconnect. IEEE Photonics Technol. Lett., 30, 1040-1043(2018).