[1] Mukasa K, Imamura K, Tsuchida Y et al. Multi-core fibers for large capacity SDM[C]. //2011 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, March 6-10, 2011, Los Angeles, CA, USA., 12050335(2011).

[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, 6, 413-487(2014).

[3] Sakaguchi J, Puttnam B J, Klaus W et al. Large-scale space division multiplexed transmission through multi-core fiber[C]. //Asia Communications and Photonics Conference 2012, November 7-10, 2012, Guangzhou, China, AS2C.5(2012).

[4] Berdagué S, Facq P. Mode division multiplexing in optical fibers[J]. Applied Optics, 21, 1950-1955(1982).

[5] Xie X Q, Tu J J, Zhou X et al. Design and optimization of 32-core rod/trench assisted square-lattice structured single-mode multi-core fiber[J]. Optics Express, 25, 5119-5132(2017).

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

[7] Sillard P, Molin D. A review of few-mode fibers for space-division multiplexed transmissions[C]. //39th European Conference and Exhibition on Optical Communication (ECOC 2013), September 22-26, 2013, London, UK. [S. l.: s. n.], 13841833(2013).

[8] Chanclou P, Kaczmarek C, Mouzer G et al. Design and demonstration of a multicore single-mode fiber coupled lens device[J]. Optics Communications, 233, 333-339(2004).

[9] Jin W X, Ren G B, Pei L et al. Dual-mode large-mode-area multi-core fiber with circularly arranged airhole cores[J]. Acta Physica Sinica, 66, 2024210(2017).

[10] Hayashi T. Multi-core fiber for high-capacity long-haul spatially-multiplexed transmission[J]. Sei Technical Review, 77, 14-22(2013).

[11] Sakamoto T, Matsui T, Saitoh K et al. Low-loss and low-DMD 6-mode 19-core fiber with cladding diameter of less than 250 μm[J]. Journal of Lightwave Technology, 35, 443-449(2017).

[12] Sakamoto T, Saitoh K, Saitoh S et al. Six-mode seven-core fiber for repeated dense space-division multiplexing transmission[J]. Journal of Lightwave Technology, 36, 1226-1232(2018).

[13] Kumar D, Ranjan R. Analysis of crosstalk performance and its reduction amount in single-mode homogeneous trench-assisted multicore fiber[C]. //2018 Conference on Information and Communication Technology (CICT), October 26-28, 2018, Jabalpur, India., 1-5(2018).

[14] Liu C, Pei L, Xie Y H et al. Design of low crosstalk few mode multi-core fiber based on heterogeneous structure[J]. Chinese Journal of Lasers, 47, 1106004(2020).

[15] Li Z H, Li S G, Li J S et al. Double-trench assisted thirteen-core five-mode fibers with low crosstalk and low non-linearity[J]. Acta Physica Sinica, 70, 20201825(2021).

[16] Xie Y H, Pei L, Zheng J J et al. Low-DMD and low-crosstalk few-mode multi-core fiber with air-trench/holes assisted graded-index profile[J]. Optics Communications, 474, 126155(2020).

[17] Cheng T L, Zhang J W, Wang G R et al. minimal mode fiber with low crosstalk grooves embedded with air holes: CN112083525A[P](2020).

[18] Li S G, Wang L Y, Li Z H et al. Low crosstalk multi-core and few mode optical fiber with grooves and pores: CN112764154A[P](2021).

[19] Tu J J, Long K P, Saitoh K. An efficient core selection method for heterogeneous trench-assisted multi-core fiber[J]. IEEE Photonics Technology Letters, 28, 810-813(2016).

[20] Kong F, Saitoh K, Mcclane D et al. Mode area scaling with all-solid photonic bandgap fibers[J]. Optics Express, 20, 26363-26372(2012).

[21] Cao Y, Shi W H, Xu G J et al. Design of bend-resistant large-mode-area dual-mode photonic crystal fiber[J]. Laser & Optoelectronics Progress, 52, 100602(2015).

[22] Jung Y, Kang Q Y, Zhou H Y et al. Low-loss 25.3 km few-mode ring-core fiber for mode-division multiplexed transmission[J]. Journal of Lightwave Technology, 35, 1363-1368(2017).

[23] Zheng S W, Ren G B, Lin Z et al. A novel four-air-hole multicore dual-mode large-mode-area fiber: Proposal and design[J]. Optical Fiber Technology, 19, 419-427(2013).

[24] Salsi M, Koebele C, Sperti D et al. Mode-division multiplexing of 2×100 Gb/s channels using an LCOS-based spatial modulator[J]. Journal of Lightwave Technology, 30, 618-623(2012).

[25] Takenaga K, Arakawa Y, Sasaki Y et al. A large effective area multi-core fiber with an optimized cladding thickness[J]. Optics Express, 19, B543-B550(2011).

[26] Takenaga K, Arakawa Y, Tanigawa S et al. An investigation on crosstalk in multi-core fibers by introducing random fluctuation along longitudinal direction[J]. IEICE Transactions on Communications, E94-B, 409-416(2011).

[27] 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).

[28] Ji S Y, Gong J J, Zhu F. Calculation of mode field diameter and effective area of single-mode fiber[J]. Modern Transmission, 34-37(2020).

[29] Lin Z, Zheng S W, Ren G B et al. Characterization and comparison of 7-core and 19-core large-mode-area few-mode fibers[J]. Acta Physica Sinica, 62, 064214(2013).

[30] Xu M N, Zhou G Y, Chen C et al. of a novel four-mode micro-structured fiber with low-level crosstalk and high mode differential group delay[J]. Acta Physica Sinica, 64, 234206(2015).

[31] Zhang W, Chen H M. Design and analysis of high MDGD micro-structured few-mode fiber[J]. Study on Optical Communications, 26-29(2017).

[32] Liu D M, Sun J Q, Lu P. Optical fiber optics[M]. 2nd ed, 73-93(2008).