CN211263846U - Six-core strong-coupling four-mode optical fiber - Google Patents

Abstract

The application provides a six-core strong coupling four-mode optical fiber; the optical fiber consists of six fiber cores with graded index distribution, a refractive index groove and a fluorine-doped silica cladding; the supermode operation with high mode field density, low loss and low crosstalk is realized, and the bending loss is effectively reduced by adopting the concave refractive index cladding.

Description

Six-core strong-coupling four-mode optical fiber

Technical Field

The application relates to a novel optical fiber, in particular to a six-core strong-coupling four-mode optical fiber which can be applied to the fields of communication networks, optical information processing, new-generation information technologies and the like.

Background

In recent years, optical fiber communicationThe industry has made a breakthrough in the transmission capacity of communication networks around the physical dimension of space division multiplexing (including core multiplexing and mode division multiplexing and combinations thereof); the research of multi-core fiber and few-mode fiber in Space division multiplexing becomes a leading-edge research hotspot [ Guifang Li, New Bai, and Ningbo Zhuao and Cen Xia, Space-division multiplexing: the next front in optical communication&Photonics,2014,6(4):5041–5046；Guifang Li,Magnus Karlsson,Xiang Liu,and YvesQuiquempois,Focus issue introduction:space-division multiplexing,Opt.Express2014,22,32526-32527；He Wen,Hongjun Zheng,et al.Few-mode fibre-optic microwavephotonic links[J]Light, Science and Applications 2017,6, 8; zhenghongjun, Li Xin, Baicheng forest, transmission of chirp pulse in optical fiber, Beijing: scientific publishers, 2018.1, 1-184; study on Shaomo multiplex (demultiplexing) technique in Mao-Ma-Muyu system [ J]The university newspaper of chat (Nature science edition), 2020, 33(2): 50-67; wang Xiagui, Zheng hong Jun (Communicator), Li Xin, Liuyang, wish, Baicheng forest, Hu sanitary, development of optical fiber research in Modal division multiplexing system, Chun university journal (Nature science edition), 2019.4, 32(2):69-79](ii) a A multimode optical fiber with multiple solid cores and strong coupling also gets attention; the multi-solid core super-mode fiber is essentially a few-mode fiber with larger effective mode field area, large mode field density, low mode dependent loss, low mode coupling and low differential mode group delay [ Cen Xia, Neng Bai, Ibrahim Ozdur, et al, Supermodes for optical transmission, Optics Express,2011,19(17): 16653-16664; cen Xia, Neng Bai, rodrigo amezcua-corea, et al, Supermodes in string-coupled multi-core fibers, OFC2013, oth3k.5; yu Ruyuan, hong jun Zheng et al, anovel thread-ring-core now-mode with large effective area and low non-linear core]，Optoelectronics Letters.2018,14(1):30-35](ii) a The pure silica fiber core can effectively reduce the attenuation and the fusion loss of the optical fiber, and is mostly applied to single-mode optical fibers (T.Hasegawa et al.2016.Advances in ultra-low-loss silica fibers [ J.].Frontiers in Optics,paper FTu2B.2；S.Ten.2016.UltraLow-loss Optical Fiber Technology[J].Optical Fiber Communication Conference,paper Th4E.5；Yoshiaki Tamura.2018.Ultra-low loss silica core fiber for longhaul transmission[J]Optical Fiber Communication Conference, paper M4 B.1). The few-mode optical fiber with the graded-index profile can realize the low differential mode group delay DMGD and the far field and the near field with the same mode width, and the Effective Refractive Index Difference (ERID) of different modes is more than 0.5x10^-3Mode coupling can be avoided (Pierre Sillard et al, Few-Mode Fibers for Space-Division Multiplexed Transmissions [ J],European Conference&Exhibition on Optical Communication,2013.03(A1):1-3；Roland Ryf.Switching and Multiplexing Technologies for Mode-DivisionMultiplexed Networks[D],Optical Fiber Communication Conference&Exposure, 2017, Tu2 c). In conclusion, if the concepts of pure silica fiber core, graded index distribution and multi-solid-core strong-coupling supermode optical fiber are organically fused, the research challenge of the few-mode optical fiber at present is expected to be solved, and the method has important academic value and application value, and has great research significance and wide application prospect.

SUMMERY OF THE UTILITY MODEL

Under the support of special expenses of construction engineering of national science foundation (numbers 61671227 and 61431009), Shandong province science foundation (ZR2011FM015) and Taishan scholars, the application provides a six-core strong-coupling four-mode optical fiber, which integrates the advantages of a pure silica fiber core, graded index distribution and a multi-solid-core supermode optical fiber and provides important support for deep research in the fields of optical fiber optics, optical fiber communication, optical fiber wireless access, optical information processing, new-generation information technology and the like.

The technical scheme that this patent application solved its technical problem and adopts is:

the application provides a six-core strong coupling four-mode optical fiber; the optical fiber consists of six fiber cores with graded index distribution, a refractive index groove and a fluorine-doped silica cladding; the radius of each of the six cores is R1-3 μm, the inner radius of the groove is R2-15 μm, the outer radius of the groove is R3-25 μm, and the radius of the cladding is R4-62.5 μm; the central coordinates of the six fiber cores are (6 μm, 0) in sequence,

(-6μm，0)，

the refractive indexes of the six core centers, the grooves and the fluorine-doped silica cladding are respectively n 1-1.4440, n 2-1.4165 and n 3-1.4220; each core is according to n as 1.4440[1-2 delta (r/a)²]^0.5A graded index profile, r is the distance from any point in the core to the axis, a is the outer diameter of the core, the refractive index difference between the core center and the cladding

The optical fiber is excited by incident light, and the optical fiber modes in the six fiber cores are strongly coupled, so that the multimode operation of low loss, low crosstalk, large effective mode field area, low nonlinear coefficient, high mode field density and low differential mode group delay is realized, and the transmission performance of the optical fiber is further improved; the mode field characteristics of the supermode in the fiber can be varied by varying the size, location and refractive index profile of the core, cladding and depressed index cladding.

The beneficial effect of this patent application is as follows:

1. the optical fiber modes in the six fiber cores are strongly coupled, so that the supermode operation with high mode field density, low loss and low crosstalk is realized, and the optical fiber transmission performance is further improved;

2. the optical fiber concave refractive index cladding can effectively reduce bending loss;

3. the optical fiber integrates the advantages of a pure silica fiber core, graded index distribution and a multi-solid-core supermode optical fiber, and provides important support for the deep research in the fields of optical fiber optics, optical fiber communication, optical fiber wireless access and optical information processing, new-generation information technology and the like.

4. The mode field characteristics of the supermode in the fiber can be changed by changing the size, position and refractive index distribution of the core, the cladding and the depressed index cladding.

Drawings

FIG. 1 is a schematic cross-sectional view of a six-core strongly-coupled four-mode optical fiber according to the present application; the fiber consists of six graded-index-profile cores (cross-hatched), a refractive-index trench (right-obliquely hatched), and a fluorine-doped silica cladding (white).

FIG. 2 shows the electric field distributions for the four supermode x-polarizations LP01, LP11a, LP21a and LP31a at a wavelength of 1.55 μm.

Fig. 3 shows the effective refractive index of the four supermodes as a function of input wavelength. The solid lines with squares, stars, solid dots and diamonds are the LP01, LP11, LP21 and LP31 supermode cases, respectively.

Detailed Description

The following describes the technical solution of the present patent application in detail with reference to the embodiments and the drawings, but the scope of protection is not limited thereto.

Example 1 fig. 1 is a schematic diagram of a six-core strong coupling four-mode optical fiber according to the present application. The optical fiber consists of six fiber cores with graded index distribution, a refractive index groove and a fluorine-doped silica cladding; the radius of each of the six cores is R1-3 μm, the inner radius of the groove is R2-15 μm, the outer radius of the groove is R3-25 μm, and the radius of the cladding is R4-62.5 μm; the central coordinates of the six fiber cores are (6 μm, 0) in sequence,

(-6μm，0)，

the refractive indexes of the six core centers, the grooves and the fluorine-doped silica cladding are respectively n 1-1.4440, n 2-1.4165 and n 3-1.4220; each core is according to n as 1.4440[1-2 delta (r/a)²]^0.5Graded index profile, r being from any point in the core to the axisDistance, a is the outer diameter of the core, the refractive index difference between the core center and the cladding

The optical fiber is excited by incident light, and the optical fiber modes in the six fiber cores are strongly coupled, so that the multimode operation of low loss, low crosstalk, large effective mode field area, low nonlinear coefficient, high mode field density and low differential mode group delay is realized, and the transmission performance of the optical fiber is further improved; the mode field characteristics of the supermode in the fiber can be varied by varying the size, location and refractive index profile of the core, cladding and depressed index cladding.

FIG. 2 shows the electric field distributions for the four supermode x-polarizations LP01, LP11a, LP21a and LP31a at a wavelength of 1.55 μm. The equipotential lines in the figure represent the intensity of the electric field of the incident light, and the higher the density, the stronger the electric field. If polarization degeneracy and spatial degeneracy are considered, the proposed fiber can support 12 supermodes as follows: LP 01X, LP 01Y, LP11a X, LP11a Y, LP11b X, LP11bY, LP21a X, LP21a Y, LP21b X, LP21b Y, LP31a X and LP31a Y. We have obtained a supermode formed by strong coupling of the six inter-core modes, where the core-to-core distance is much shorter than for conventional multicore fibers. The field distribution of the supermode can be regarded as superposition and strong reconstruction of independent modes of each fiber core. Thus, a six-core few-mode fiber can support a larger effective area and higher mode density than conventional fibers, which can effectively reduce the nonlinear effects of the fiber and optical communication. Since the Effective Refractive Index (ERI), dispersion, effective area, and nonlinear coefficients of degenerate modes are similar, four supermodes are discussed herein.

Fig. 3 shows the effective refractive index of the four supermodes as a function of input wavelength. The solid lines with squares, stars, solid dots and diamonds are the LP01, LP11, LP21 and LP31 supermode cases, respectively. As can be seen in fig. 3, the effective refractive index decreases for all four supermode modes as the input wavelength increases. The effective index drop rates for the LP01, LP11 modes are significantly lower than for the LP21 and LP31 modes. For feedingAt a given input wavelength, the effective index of the LP01 mode is at a maximum, the effective index of the LP31 mode is at a minimum, and the effective index of the LP11 mode is greater than that of the LP21 mode, when the input wavelength is 1.55 μm, the effective indices of the LP01, LP11, LP21, and LP31 supermodes are 1.4316, 1.4309, 1.4296, and 1.4287, respectively, and the difference between the effective indices of the LP01 and LP11 modes is 0.7 × 10^-3The effective refractive index difference between the LP11 mode and the LP21 mode is 1.3 × 10^-3The effective refractive index difference between the LP21 mode and the LP31 mode is 0.9 × 10^-3The effective index difference of each of the four supermode modes is greater than 0.5 × 10^-3According to the literature [ Pierre Sillard, Denis molin. Few-mode fibers for space-division multiplexedtransition [ C ]].European Conference&Inhibition on Optical Communication,2013,03(A1): 1-3; zhenghongjun, Li Xin, Baicheng forest, transmission of chirp pulse in optical fiber, Beijing: scientific Press, 2018, 1-184]Low modal crosstalk can be achieved.

In summary, the proposed fiber achieves four supermode operation with low loss, low dispersion, low crosstalk and low DMGD. It should be noted that the specific embodiments are merely representative examples of the present application, and it is obvious that the technical solutions of the present application are not limited to the above-described examples, and many variations are possible. Those skilled in the art, having the benefit of this disclosure, and the benefit of this description, will recognize what is coming within the scope of the claims as though fully disclosed herein or fully apparent from the written description.

Claims (1)

1. A six-core strong coupling four-mode optical fiber; the method is characterized in that: the optical fiber consists of six fiber cores with graded index distribution, a refractive index groove and a fluorine-doped silica cladding; the radius of each of the six cores is R1-3 μm, the inner radius of the groove is R2-15 μm, the outer radius of the groove is R3-25 μm, and the radius of the cladding is R4-62.5 μm; the central coordinates of the six fiber cores are (6 μm, 0) in sequence,

(-6μm，0)，

the refractive indexes of the six core centers, the grooves and the fluorine-doped silica cladding are respectively n 1-1.4440, n 2-1.4165 and n 3-1.4220; each core is according to n as 1.4440[1-2 delta (r/a)²]^0.5A graded index profile, r is the distance from any point in the core to the axis, a is the outer diameter of the core, the refractive index difference between the core center and the cladding

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