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

[2] P. J. Winzer, D. T. Neilson. From scaling disparities to integrated parallelism: a decathlon for a decade. J. Lightwave Technol., 2017, 35: 1099-1115.

[3] Y. Weng, X. He, Z. Pan. Space division multiplexing optical communication using few-mode fibers. Opt. Fiber Technol., 2017, 36: 155-180.

[4] B. Wohlfeil, G. Rademacher, C. Stamatiadis, K. Voigt, L. Zimmermann, K. Petermann. A two-dimensional fiber grating coupler on SOI for mode division multiplexing. IEEE Photon. Technol. Lett., 2016, 28: 1241-1244.

[5] Y. Yu, M. Ye, S. Fu. On-chip polarization controlled mode converter with capability of WDM operation. IEEE Photon. Technol. Lett., 2015, 27: 1957-1960.

[6] L.-W. Luo, N. Ophir, C. P. Chen, L. H. Gabrielli, C. B. Poitras, K. Bergmen, M. Lipson. WDM-compatible mode-division multiplexing on a silicon chip. Nat. Commun., 2014, 5: 3069.

[7] SternB.LipsonM., “High-bandwidth link with single laser input using silicon modulators and mode multiplexing,” in CLEO: Science and Innovations (Optical Society of America, 2016), paper STu4G-5.

[8] WuX.XuK.HuangC.ShuC.TsangH. K., “Mode division multiplexed 3 × 28  gbit/s on-chip photonic interconnects,” in CLEO: Science and Innovations (Optical Society of America, 2016), paper STu4G-6.

[9] KoonenA. M. J.ChenH. S.Van Den BoomH. P. A.RazO., “Silicon photonic integrated mode multiplexer,” in IEEE Photonics Society Summer Topical Meeting Series PSST (2012), pp. 240–241.

[10] FontaineN. K.DoerrC. R.MestreM. A.RyfR.WinzerP.BuhlL.SunY.JiangX.LingleR., “Space-division multiplexing and all-optical MIMO demultiplexing using a photonic integrated circuit,” in National Fiber Optic Engineers Conference, OSA Technical Digest (2012), paper PDP5B.1.

[11] Y. Ding, H. Ou, J. Xu, C. Peucheret. Silicon photonic integrated circuit mode multiplexer. IEEE Photon. Technol. Lett., 2013, 25: 648-651.

[12] DoerrC. R.FontaineN.HiranoM.SasakiT.BuhlL.WinzerP., “Silicon photonic integrated circuit for coupling to a ring-core multimode fiber for space-division multiplexing,” in European Conference and Exhibition on Optical Communication (2011), paper Th.13.A.3.

[13] DemirtzioglouI.LacavaC.ShakoorA.KhokharA.JungY.ThomsonD. J.PetropoulosP., “Silicon grating coupler for mode order conversion,” in Conference on Lasers and Electro-Optics (Optical Society of America, 2019), paper JTh2A.74.

[14] M. Zhang, H. Liu, B. Wang, G. Li, L. Zhang. Efficient grating couplers for space division multiplexing applications. IEEE J. Sel. Top. Quantum Electron., 2018, 24: 8200605.

[15] C. T. Nadovich, W. D. Jemison, D. J. Kosciolek, D. T. Crouse. Focused apodized forked grating coupler. Opt. Express, 2017, 25: 26861-26874.

[16] R. Marchetti, C. Lacava, A. Khokhar, X. Chen, I. Cristiani, D. J. Richardson, G. T. Reed, P. Petropoulos, P. Minzioni. High-efficiency grating-couplers: demonstration of a new design strategy. Sci. Rep., 2017, 7: 16670.