[1] Freckmann T, Essiambre R J, Winzer P J, et al. Fiber capacity limits with optimized ring constellations[J]. IEEE Photonics Technology Letters, 2009, 21(20): 1496-1498.

[2] Richardson D J, Fini J M, Nelson L E. Space-division multiplexing in optical fibres[J]. Nature Photonics, 2013, 7(5): 354-362.

[3] 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.

[4] Leoni 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.

[5] Xu C L, Yan K, Gu C, et al. All-fiber laser with flattop beam output using a few-mode fiber Bragg grating[J]. Optics Letters, 2018, 43(6): 1247-1250.

[6] Sun B, Wang A T, Xu L X, et al. Low-threshold single-wavelength all-fiber laser generating cylindrical vector beams using a few-mode fiber Bragg grating[J]. Optics Letters, 2012, 37(4): 464-466.

[7] Ngcobo S, Litvin I, Burger L, et al. A digital laser for on-demand laser modes[J]. Nature Communications, 2013, 4: 2289.

[8] WangN, Antonio-Lopez J E, Alvarado Zacarias J C, et al. Mode-selective fiber laser using a photonic lantern[C]∥ECOC 2016; 42nd European Conference on Optical Communication, September 18-22, 2016, Dusseldorf, Germany.New York: IEEE Press, 2016: 1- 3.

[9] Yan TT, Jiang YC, Li HS, et al.Switchable dual-mode all-fiber laser by using LPG and FBG[C]∥2018 Asia Communications and Photonics Conference (ACP), October 26-29, 2018, Hangzhou, China.New York: IEEE Press, 2018: 1- 2.

[10] Wan H D, Wang J, Zhang Z X, et al. Passively mode-locked ytterbium-doped fiber laser with cylindrical vector beam generation based on mode selective coupler[J]. Journal of Lightwave Technology, 2018, 36(16): 3403-3407.

[11] Ismaeel R, Lee T, Oduro B, et al. All-fiber fused directional coupler for highly efficient spatial mode conversion[J]. Optics Express, 2014, 22(10): 11610-11619.

[12] Ren F, Yu J, Wang J. Spatial-mode switchable ring fiber laser based on low mode-crosstalk all-fiber mode MUX/DEMUX[J]. Optics & Laser Technology, 2008, 101: 21-24.