[1] [1] RICHARDSON D J, FINI J M, NELSON L E. Space-division multiplexing in optical fibres[J]. Nature photonics, 2013, 7(5): 354-362.

[2] [2] LI G F, BAI N, ZHAO N B, et al. Space-division multiplexing: the next frontier in optical communication[J]. Advances in Optics and Photonics, 2014, 6(4): 413-487.

[3] [3] SU Y, HE Y, CHEN H, et al. Perspective on mode-division multiplexing[J]. Applied Physics Letters, 2021, 118(20): 200502-1-200502-9.

[4] [4] KOEBELE C, SALSI M, MILORD L, et al. 40km transmission of five mode division multiplexed data streams at 100Gb/s with low MIMO-DSP complexity[C]//IEEE. Proceedings of European Conference and Exposition on Optical Communications. Geneva: IEEE, 2011: 1-3.

[5] [5] BAI N, IP E, HUANG Y K, et al. Mode-division multiplexed transmission with inline few-mode fiber amplifier[J]. Optics express, 2012, 20(3): 2668-2680.

[6] [6] SIEIFFER V, LENONI P, JUNG Y, et al. 20×960-Gb/s Space-division-multiplexed 32QAM transmission over 60 km few-mode fiber[J]. Optics express, 2014, 22(1): 749-755.

[7] [7] RANDEL S, RYF R, SIERRA A, et al. 6×56Gb/s mode-division multiplexed transmission over 33-km few-mode fiber enabled by 6×6 MIMO equalization[J]. Optics Express, 2011, 19(17): 16697-16707.

[8] [8] RYF R, FONTAINE N K, CHEN H S, et al. 72-Tb/s transmission over 179-km all-fiber 6-mode span with two cladding pumped in-line amplifiers[C]//IEEE. 2015 European Conference on Optical Communication (ECOC). Valencia. Spain: IEEE, 2015: 1-3.

[9] [9] CHEN H S, RYF R, FONTAINE N K, et al. High spectral efficiency mode-multiplexed transmission over 87-km 10-mode fiber[C]//IEEE. Proceedings of 2016 Optical Fiber Communications Conference and Exhibition (OFC). Anaheim: IEEE, 2016: 1-3.

[11] [11] SILLARD P, MOLIN D, BIGOT-ASTRUC M, et al. 50 μm multimode fibers for mode division multiplexing[J]. Journal of lightwave technology, 2016, 34(8): 1672-1677.

[12] [12] SIMONNEAU C, D'AMATO A, JIAN PU, et al. 4×50 Gb/s transmission over 4.4 km of multimode OM2 fiber with direct detection using mode group multiplexing[C]//IEEE. Proccedings of Optical Fiber Communication Conference. Anaheim: IEEE, 2016:1-3.

[14] [14] LI J, WU Z, GE D, et al. Weakly-coupled mode division multiplexing over conventional multi-mode fiber with intensity modulation and direct detection[J]. Frontiers of Optoelectronics, 2019, 12(1): 31-40.

[15] [15] LI J, HU J, ZOU D, et al. Terabit mode division multiplexing discrete multitone signal transmission over OM2 multimode fiber[J]. IEEE Journal of Selected Topics in Quantum Electronics, 2020, 26(4): 1-8.

[16] [16] REN F, LI J H, WU Z Y, et al. Three-mode mode-division-multiplexing passive optical network over 12-km low mode-crosstalk FMF using all-fiber mode MUX/DEMUX[J]. Optics Communications, 2017, 383: 525-530.

[17] [17] GASULLA I, KAHN J M. Performance of direct-detection mode-group-division multiplexing using fused fiber couplers[J]. Journal of Lightwave Technology, 2015, 33(9): 1748-1760.

[18] [18] GRUNER-NIELSEN L, MATHEW N M, Nymann M H, et al. Mode division multiplexing on standard 50/125 μm multi mode fiber using photonic lanterns[C]//IEEE. Proceedings of 2021 Optical Fiber Communications Conference and Exhibition (OFC). San Francisco: IEEE, 2021: 1-3.