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针对少模多芯光纤中存在的纤芯内模式间的耦合及芯间模式耦合等问题, 提出一种阶跃型环形芯组成的7芯结构光纤, 每个纤芯可支持5个模式. 各纤芯具有一个中心低折射率区域和一个高折射率环, 保证纤芯内模式间均具有较大的折射率差, 从而减小模式间耦合问题. 运用有限元法模拟分析了中心纤芯和外纤芯的弯曲损耗、模式间的串扰特性及纤芯参数对串扰性能的影响. 数据模拟结果表明, 当波长为1.55 μm, 这种多芯光纤在弯曲半径为50 mm时, 弯曲损耗远低于光纤衰减损耗, 且纤芯中5个模式的相邻纤芯之间串扰均小于–20 dB/100 km, 因而这种多芯光纤在小弯曲半径下仍可实现纤芯间独立的长距离信息传输.Aiming at solving the problems of coupling between modes in a core and mode coupling between cores in few-mode multi-core fiber, a fiber with seven cores each with step index is proposed, and each core can support five modes. Each core has a central low refractive index region and a high refractive index ring to ensure that there is a large refractive index difference between modes in the core, so as to reduce the problem of mode coupling. The bending loss of central core and outer core, the crosstalk characteristics between modes and the influence of core parameters on crosstalk performance are simulated and analyzed by the finite element method. The simulation results show that at a wavelength of 1.55 μm and a bending radius of 50 mm, the bending loss of the proposed multi-core fiber is much lower than its attenuation loss, and the crosstalk between the adjacent cores of the five core modes are less than –20 dB/100 km. Therefore, this multi-core fiber can realize independent transmission of the core modes with long-distance under small bending radius.
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Keywords:
- few mode multi-core fiber /
- inter-core crosstalk /
- bending loss /
- mode field
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[22] Xie Y, Pei L, Zheng J 2020 Opt. Commun. 474 126155
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[23] Koshiba M, Saitoh K, Takenaga K 2012 IEEE Photonics J. 4 1987
Google Scholar
[24] Ce N X, Amezcua-Correa R, Bai N, Antonio-Lopez, E, Li G 2012 IEEE PTL 24 1914
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[28] Xie Y, Pei L, Zheng J, Zhao Q, Li J J 2020 Opt. Express 28 23806
Google Scholar
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图 1 环芯少模多芯光纤结构示意图 (a)单独纤芯示意图; (b)剖面图
Fig. 1. Structure diagram of ring core few-mode multi-core fiber: (a) Single fiber core; (b) whole configuration.
图 2 环形芯少模多芯光纤折射率分布图
Fig. 2. Refractive index distribution of ring core few-mode multi-core fiber.
图 3 各模式的有效折射率与纤芯内半径Rring_in的关系
Fig. 3. Relationship between the effective refractive index of each mode changes with the inner radius Rring_in.
图 4 弯曲半径为50 mm时, 外纤芯5种模式的电场能量分布 (a) LP01模式; (b) LP11模式; (c) LP21模式; (d) LP02模式; (e) LP31模式
Fig. 4. Electric field energy distribution of the outer fiber core in five modes at the bending radius of 50 mm: (a) LP01 mode; (b) LP11 mode; (c) LP21 mode; (d) LP02 mode; (e) LP31 mode.
图 5 λ = 1550 nm时, 弯曲半径Rb与弯曲损耗的关系曲线 (a) 中心纤芯; (b)外纤芯
Fig. 5. Bending loss curves as a function of bending radius Rb at the wavelength of 1550 nm: (a) Central core; (b) outer core.
图 6 模式有效折射率随弯曲半径Rb的变化曲线(其中λ = 1550 nm, Λ = 45 μm) (a)中心纤芯模式; (b)外纤芯模式
Fig. 6. Effective refractive indexes of the modes as a function of bending radius Rb for the fiber with λ = 1550 nm and Λ = 45 μm: (a) Central core; (b) outer core.
图 7 多芯光纤在50 mm弯曲半径下外纤芯的模场分布图 (a) LP01模; (b) LP11模; (c) LP21模; (d) LP02模; (e) LP31模
Fig. 7. Mode field distribution of the outer core of the multi-core fiber at the bending radius of 50 mm: (a) LP01 mode; (b) LP11 mode; (c) LP21 mode; (d) LP02 mode; (e) LP31 mode.
图 8 λ = 1550 nm,
$ \varLambda =45 $ μm时, 弯曲半径Rb与串扰的关系曲线 (a)中间纤芯中的LP01模式和外纤芯各模式的串扰; (b)中间纤芯中的LP11模式和外纤芯各模式的串扰; (c)中间纤芯中的LP21模式和外纤芯各模式的串扰; (d)中间纤芯中的LP02模式和外纤芯各模式的串扰; (e)中间纤芯中的LP31模和外纤芯的各模式的串扰Fig. 8. Crosstalk curves for the multi-core optical fiber with λ = 1550 nm and Λ = 45 μm: (a) LP01 mode in the central core and the modes in the outer core; (b) LP11 mode in the central core and the modes in the outer core; (c) LP21 mode in the central core and the modes in the outer core; (d) LP02 mode in the central core and the modes in the outer core; (e) LP31 mode in the central core and the modes in the outer core.
图 9 芯间距
$ \varLambda $ 与串扰的关系曲线 (a)中间纤芯LP01模式与外纤芯 LP11模式; (b) 中间纤芯LP11模式与外纤芯 LP11模式; (c) 中间纤芯LP21模式与外纤芯 LP11模式; (d) 中间纤芯LP02模式与外纤芯 LP02模式; (e) 中间纤芯LP31模式与外纤芯 LP31模式Fig. 9. Relation curves between core spacing Λ and crosstalk: (a) LP01 mode of the central core and LP11 mode of the outer core; (b) LP11 mode of the central core and LP11 mode of the outer core; (c) LP21 mode of the central core and LP11 mode of the outer core; (d) LP02 mode of the central core and LP02 mode of the outer core; (e) LP31 mode of the central core and LP31 mode of the outer core.
图 10 纤芯-包层折射率差与芯间串扰的关系 (a)中间纤芯中的LP01模和外纤芯各模式的串扰; (b)中间纤芯中的LP11模和外纤芯各模式的串扰; (c)中间纤芯中的LP21模和外纤芯各模式的串扰曲线; (d)中间纤芯中的LP02模和外纤芯各模式的串扰曲线; (e)中间纤芯中的LP31模和外纤芯的各模式之间的串扰
Fig. 10. Relationship between core-cladding refractive index difference and inter-core crosstalk: (a) LP01 mode in the central core and modes in the outer core; (b) LP11 mode in the central core and modes in the outer core; (c) LP21 mode in the central core and modes in the outer core; (d) LP02 mode in the central core and modes in the outer core; (e) LP31 mode in the central core and modes in the outer core.
表 1 中间纤芯与外纤芯各模式之间的串扰
Table 1. Crosstalk between different modes of middle core and outer core.
XT/[dB·(100 km)–1] Core 2 LP11b 
LP11b 
LP21b 
LP21b 
LP31b 
LP31b 
Core 1 LP11b 
–92.84 –129.70 –125.62 –95.26 –118.93 –116.99 LP11b 
–124.63 –92.86 –99.26 –135.26 –123.78 –120.89 LP21b 
–79.30 –82.52 –63.70 –72.51 –90.05 –93.15 LP21b 
–60.43 –69.32 –71.89 –63.78 –89.96 –89.17 LP31b 
–33.35 –44.74 –46.39 –35.01 –28.76 –46.20 LP31b 
–41.08 –33.92 –34.12 –50.58 –49.63 –28.19 
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表 2 光纤性能对比
Table 2. Fiber performance comparison.
Year Number of fiber cores Structure of fiber core Cladding diameter/μm Bending radius/mm Bending loss Crosstalk/dB
(Transmission
distance)2012[24] 7 Hole-assisted 225 140 0.242 dB/km –60 (1 km) 2015[25] 36 Trench-assisted 200 140 0.001 dB/km –31 (5.5 km) 2017[26] 12 Trench-assisted 230 210 0.05 dB/100 turns –48 (500 km) 2019[27] 8 Differential inner-cladding 160 30 0.0049 dB/100 turns < –50 (100 km) 2020[28] 7 Hole-assisted 125 80 2.20 × 10–6 dB/m –32 (100 km) Our design 7 Ring-core structure 180 50 2.77 × 10–8 dB/m –116 (100 km)
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[1] Richardson D J, Fini J M, Nelson L E 2013 Nat. Photonics 7 354
Google Scholar
[2] Qian D, Huang M F, Huang Y K, Shao Y, Hu J, Wang T 2012 J. Lightwave Technol. 30 1540
Google Scholar
[3] Chen H G, Morency S, Jin C, Gregoire N, Essiambre 2016 Nat. Photonics 10 529
Google Scholar
[4] Mukasa K, Imamura K, Sugizaki R 2012 European Conference & Exhibition on Optical Communications Amsterdam, Netherlands, June 9, 2012 p1
[5] Igarashi K, Souma D, Wakayama Y, Takeshima K, Suzuki M 2015 Optical Fiber Communications Conference and Exhibition (OFC) Angeles, California, USA, March 22–26, 2015 pTH5C.4
[6] Shibahara K, Lee D, Kobayashi T, Mizuno T, Takara H, Sano A 2016 J. Lightwave Technol. 34 196
Google Scholar
[7] Igarashi K, Soma D, Wakayama Y, Takeshima K, Kawaguchi Y, Yoshikane N, Tsuritani T, Morita I, Suzuki M 2016 Opt. Express 24 10213
Google Scholar
[8] Kumar D, Ranjan R 2018 Opt. Fiber Technol. 41 95
Google Scholar
[9] Xie Y, Pei L, Zheng J, Zhao Q, Ning T, Sun J 2019 Appl. Opt. 58 4373
Google Scholar
[10] 刘诗男, 宁提纲, 马绍朔 2018 中国激光 45 1206001
Google Scholar
Liu S N, Ning T G, Ma S S 2018 Chin. J. Lasers 45 1206001
Google Scholar
[11] Chen S, Tong Y, Tian H 2020 Appl. Opt. 59 4634
Google Scholar
[12] Chen X, Li M J, Koh J, Artuso A, Nolan D A 2007 Opt. Express 15 10629
Google Scholar
[13] 郑斯文, 林桢, 任国斌, 简水生 2013 62 044224
Google Scholar
Zheng S W, Lin Z, Ren G B, Jian S S 2013 Acta Phys. Sin. 62 044224
Google Scholar
[14] Fini J M, Nicholson J W 2013 Opt. Express 21 19173
Google Scholar
[15] Tsuchida Y, Saitoh K, Koshiba M 2005 Opt. Express 13 4770
Google Scholar
[16] Zheng X, Ren G, Huang L, Li H, Zhu B, Zheng H, Cao M 2016 Appl. Opt. 55 2639
Google Scholar
[17] Dablu K, Rakesh R 2020 Optoelectron. Lett. 16 126
Google Scholar
[18] Farooque U, Singh D K, Ranjan R 2019 Opt. Quantum Electron. 51 371
Google Scholar
[19] Zheng S, Ren G, Lin Z, Jian S 2013 Appl. Opt. 52 4541
Google Scholar
[20] Ye F, Tu J, Saitoh K, Morioka T 2014 Opt. Express 22 23007
Google Scholar
[21] Jaramillo-Avila B, Torres J M, Leon-Montiel R J, Rodriguez-Lara B M 2019 Sci. Rep. 9 15737
Google Scholar
[22] Xie Y, Pei L, Zheng J 2020 Opt. Commun. 474 126155
Google Scholar
[23] Koshiba M, Saitoh K, Takenaga K 2012 IEEE Photonics J. 4 1987
Google Scholar
[24] Ce N X, Amezcua-Correa R, Bai N, Antonio-Lopez, E, Li G 2012 IEEE PTL 24 1914
Google Scholar
[25] Sakaguchi J, Klaus W, Mendinueta J M D, Puttnam B J, Kobayashi T 2016 J. Lightwave Technol. 34 93
Google Scholar
[26] Yusuke S A, Katsuhiro T, Shoichiro M, Kazuhiko A 2017 Opt. Fiber Technol. 35 19
Google Scholar
[27] Xie Y, Pei L, Sun J, Zheng J, Li J J 2019 Opt. Fiber Technol. 53 102001
Google Scholar
[28] Xie Y, Pei L, Zheng J, Zhao Q, Li J J 2020 Opt. Express 28 23806
Google Scholar
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