[1] Saitoh K, Matsuo S. Multicore fiber technology[J]. Journal of Lightwave Technology, 34, 55-66(2016).

[2] Chi R H, Zhou Y P, Li L Y. Research status and development analysis of multicore fiber amplifier[J]. Laser & Optoelectronics Progress, 56, 190005(2019).

[3] Pei L, Li Z Q, Wang J S et al. Review on gain equalization technology of fiber amplifier using space division multiplexing[J]. Acta Optica Sinica, 41, 0106001(2021).

[4] Mizuno T, Miyamoto Y. High-capacity dense space division multiplexing transmission[J]. Optical Fiber Technology, 35, 108-117(2017).

[5] Awaji Y. Review of space-division multiplexing technologies in optical communications[J]. IEICE Transactions on Communications, E102.B, 1-16(2019).

[6] Tu J J, Li Z H. Review of space division multiplexing fibers[J]. Acta Optica Sinica, 41, 0106003(2021).

[7] Mori T, Sakamoto T, Wada M et al. Few-mode fibers supporting more than two LP modes for mode-division-multiplexed transmission with MIMO DSP[J]. Journal of Lightwave Technology, 32, 2468-2479(2014).

[8] Jiang S L, Ma L, Zhang Z P et al. Design and characterization of ring-assisted few-mode fibers for weakly coupled mode-division multiplexing transmission[J]. Journal of Lightwave Technology, 36, 5547-5555(2018).

[9] Dai Y, Tian F, Wang Y J et al. Design of 4-LP few-mode fiber with low-differential mode delay[J]. Acta Optica Sinica, 41, 2106003(2021).

[10] Yuan H, Furdek M, Muhammad A et al. Space-division multiplexing in data center networks: on multi-core fiber solutions and crosstalk-suppressed resource allocation[J]. Journal of Optical Communications and Networking, 10, 272-288(2018).

[11] Hayashi T, Taru T, Shimakawa O et al. Design and fabrication of ultra-low crosstalk and low-loss multi-core fiber[J]. Optics Express, 19, 16576-16592(2011).

[12] Zhang H, Wang G R, Zhang J W et al. Theoretical study on low crosstalk high-density composite multi-core photonic crystal fiber[J]. Chinese Journal of Lasers, 48, 0706005(2021).

[13] Winzer P J. Energy-efficient optical transport capacity scaling through spatial multiplexing[J]. IEEE Photonics Technology Letters, 23, 851-853(2011).

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

[15] Sasaki Y, Takenaga K, Matsuo S et al. Few-mode multicore fibers for long-haul transmission line[J]. Optical Fiber Technology, 35, 19-27(2017).

[16] Zhao J J, Tang M, Oh K et al. Polarization-maintaining few mode fiber composed of a central circular-hole and an elliptical-ring core[J]. Photonics Research, 5, 261-266(2017).

[17] Gao J T, Nazemosadat E, Yang C et al. Design, fabrication, and characterization of a highly nonlinear few-mode fiber[J]. Photonics Research, 7, 1354-1362(2019).

[18] Ren F, Zhangsun T W, Huang X S et al. Design of 20-polarization-maintaining-mode “pseudo-rectangle” elliptical-core fiber for MIMO-less MDM networks[J]. Optical Fiber Technology, 50, 87-94(2019).

[19] Li Y L, Wang X, Zheng H J et al. A novel six-core few-mode fiber with low loss and low crosstalk[J]. Optical Fiber Technology, 57, 102211(2020).

[20] Corsi A, Chang J H, Wang R H et al. Highly elliptical core fiber with stress-induced birefringence for mode multiplexing[J]. Optics Letters, 45, 2822-2825(2020).

[21] Sillard P, Bigot-Astruc M, Boivin D et al. Few-mode fiber for uncoupled mode-division multiplexing transmissions[C], 12356407(2011).

[22] Kasahara M, Saitoh K, Sakamoto T et al. Design of three-spatial-mode ring-core fiber[J]. Journal of Lightwave Technology, 32, 1337-1343(2014).

[23] Riesen N, Love J D, Arkwright J W. Few-mode elliptical-core fiber data transmission[J]. IEEE Photonics Technology Letters, 24, 344-346(2012).

[24] Feng F, Gordon G S D, Jin X Q et al. Experimental characterization of a graded-index ring-core fiber supporting 7 LP mode groups[C], 15216458(2015).

[25] Xiao H, Li H S, Jian S S. Hole-assisted polarization-maintaining few-mode fiber[J]. Optics & Laser Technology, 107, 162-168(2018).

[26] Ramachandran S, Fini J M, Mermelstein M et al. Ultra-large effective-area, higher-order mode fibers: a new strategy for high-power lasers[J]. Laser & Photonics Reviews, 2, 429-448(2008).

[27] Yaman F, Bai N, Zhu B Y et al. Long distance transmission in few-mode fibers[J]. Optics Express, 18, 13250-13257(2010).

[28] Liang J P, Mo Q, Fu S N et al. Design and fabrication of elliptical-core few-mode fiber for MIMO-less data transmission[J]. Optics Letters, 41, 3058-3061(2016).

[29] Cao Y, Yu X S, Zhao Y L et al. Design of 14-mode polarization-maintaining ring-core fiber for spatial division multiplexing[C], 17373599(2017).

[30] Xiao H, Li H S, Wu B L et al. Elliptical hollow-core optical fibers for polarization-maintaining few-mode guidance[J]. Optical Fiber Technology, 48, 7-11(2019).

[31] Corsi A, Chang J H, Rusch L A et al. Design of highly elliptical core ten-mode fiber for space division multiplexing with 2 × 2 MIMO[J]. IEEE Photonics Journal, 11, 18501211(2019).

[32] Yang Y, Mo Q, Fu S N et al. Panda type elliptical core few-mode fiber[J]. APL Photonics, 4, 022901(2018).

[34] Sasaki Y, Tajima K, Seikai S. 26 km-long polarisation-maintaining optical fibre[J]. Electronics Letters, 23, 127-128(1987).

[35] Gao Y M, Feng G, Liu Y J et al. Single-polarization fiber of PANDA type[J]. Laser & Infrared, 41, 1244-1247(2011).

[36] Okamoto K. Single-polarization operation in highly birefringent optical fibers[J]. Applied Optics, 23, 2638-2642(1984).

[37] Rühl F F, Wong D. True single-polarization design for bow-tie optical fibers[J]. Optics Letters, 14, 648-650(1989).

[38] Rashleigh S, Marrone M. Polarization holding in elliptical-core birefringent fibers[J]. IEEE Journal of Quantum Electronics, 18, 1515-1523(1982).

[39] Shibata N, Tateda M, Seikai S et al. Birefringence and polarization mode dispersion caused by thermal stress in single-mode fibers with various core ellipticities[J]. IEEE Journal of Quantum Electronics, 19, 1223-1227(1983).