WO2024077718A1 - Coupled multi-core optical fiber and preparation method therefor - Google Patents

Coupled multi-core optical fiber and preparation method therefor Download PDF

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Publication number
WO2024077718A1
WO2024077718A1 PCT/CN2022/133377 CN2022133377W WO2024077718A1 WO 2024077718 A1 WO2024077718 A1 WO 2024077718A1 CN 2022133377 W CN2022133377 W CN 2022133377W WO 2024077718 A1 WO2024077718 A1 WO 2024077718A1
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core
optical fiber
cladding
transmission
fiber
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PCT/CN2022/133377
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French (fr)
Chinese (zh)
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胡景
田国才
和联科
姚艳
翟国华
陶泉
王友兵
劳雪刚
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江苏亨通光导新材料有限公司
江苏亨通光电股份有限公司
江苏亨通光纤科技有限公司
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Publication of WO2024077718A1 publication Critical patent/WO2024077718A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/028—Optical fibres with cladding with or without a coating with core or cladding having graded refractive index
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
    • G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/36—Mechanical coupling means
    • G02B6/38—Mechanical coupling means having fibre to fibre mating means

Definitions

  • the invention belongs to the technical field of communication optical fibers, and in particular relates to a coupled multi-core optical fiber and a preparation method thereof.
  • Multi-core optical fiber based on space division multiplexing (SDM) technology can achieve an exponential increase in communication capacity and break through the communication capacity limit of single-mode optical fiber.
  • multi-core optical fiber can be divided into weakly coupled multi-core optical fiber and strongly coupled multi-core optical fiber.
  • the core spacing of weakly coupled multi-core optical fiber is larger, which sacrifices the core density.
  • the cladding diameter of the optical fiber needs to be increased, which affects the strength and bending performance of the optical fiber.
  • the core spacing of strongly coupled multi-core optical fiber is close enough to cause crosstalk between the cores, but the generated crosstalk can be decoded through multiple-input multiple-output (MIMO) technology processing to achieve mode division multiplexing transmission.
  • MIMO multiple-input multiple-output
  • the effective area of the optical fiber is increased, which is beneficial to reducing nonlinear effects.
  • the core spacing of strongly coupled multi-core optical fibers is small, more cores can be accommodated under the same cladding diameter when designing optical fibers.
  • the key points of strongly coupled multi-core optical fibers based on SDM systems include the following aspects: (1) The effective refractive index difference between modes should be large enough to avoid mode coupling; (2) The mode loss of each mode should be the same or the difference should be small enough; (3) The presence of a depressed cladding is beneficial to improving macrobending performance; (4) The mode delay (DMD) and spatial mode dispersion (SMD) of the supermode should be as small as possible to reduce the complexity of the MIMO system.
  • DMD mode delay
  • SMD spatial mode dispersion
  • Patent application CN107179581A proposes a coupled multi-core preparation method, but mainly focuses on the transmission loss of the optical fiber but does not pay attention to the spatial mode dispersion and macrobending performance of the optical fiber.
  • the object of the present invention is to provide a coupled multi-core optical fiber and a preparation method thereof, wherein the coupled multi-core optical fiber has lower transmission loss and spatial mode dispersion and better bending performance.
  • a coupled multi-core optical fiber comprises a core unit and an optical fiber cladding surrounding the core unit;
  • the fiber core unit includes a plurality of transmission fiber cores, each of which includes a core layer and a core cladding layer surrounding the core layer; the plurality of transmission fiber cores are evenly distributed in the optical fiber cladding layer;
  • the optical fiber cladding surrounding the transmission core includes an inner cladding and an annular outer cladding
  • the refractive index profile of the multi-core optical fiber is a step-type profile structure
  • No transmission core is arranged at the center of the multi-core optical fiber.
  • the fiber core unit also includes a marking fiber core, and the marking fiber core is close to any one of the transmission fiber cores.
  • the distance between two adjacent transmission fiber cores is less than or equal to 35 ⁇ m, more preferably less than or equal to 25 ⁇ m and greater than or equal to 20 ⁇ m.
  • the radius of the core layer of the transmission fiber core is greater than or equal to 3.0 ⁇ m and less than or equal to 6.25 ⁇ m, more preferably greater than or equal to 4.0 ⁇ m and less than or equal to 6.0 ⁇ m; the ratio of the radius of the core cladding layer of the transmission fiber core to the radius of the core layer is 1.0 to 3.0.
  • the radius of the optical fiber cladding is 62.5 ⁇ m.
  • the refractive index difference ⁇ N1 of the core layer relative to pure silica is -0.0005 to 0.0058; the refractive index difference ⁇ N2 of the core cladding layer relative to pure silica is -0.0060 to -0.0005.
  • the refractive index difference ⁇ N3 of the inner cladding relative to pure silica is smaller than the refractive index difference ⁇ N4 of the outer cladding relative to pure silica; preferably, the refractive index difference ⁇ N3 of the inner cladding relative to pure silica is -0.0080 to -0.0010; the refractive index difference ⁇ N4 of the outer cladding relative to pure silica is -0.0055 to 0.
  • the core layer is a germanium-doped silica core layer or an alkali metal-doped silica core layer; and the core cladding is a fluorine-doped silica cladding.
  • the radius of the marking fiber core is greater than or equal to 2.5 ⁇ m and less than or equal to 4 ⁇ m; the marking fiber core is a germanium-doped silica fiber core; and the refractive index difference of the marking fiber core relative to pure silica is 0.0030-0.0040.
  • the method for preparing the coupled multi-core optical fiber comprises the following steps:
  • a sleeve rod consisting of an inner cladding and an outer cladding and each core rod in the core unit (transmission core and marking core) are prepared;
  • optical fiber structure of the present invention does not have a fiber core at the center, so that each transmission fiber core can be more effectively coupled;
  • the refractive index profile of the optical fiber of the present invention adopts a step-type profile structure, which can increase the effective refractive index difference between modes and avoid high-order mode coupling;
  • the optical fiber of the present invention has an inner cladding and an outer cladding, and the outer cladding is a ring structure, which can effectively improve the bending performance of the coupled multi-core optical fiber;
  • the optical fiber of the present invention can meet the demand for large-capacity transmission through the structural design of the core and the cladding and the design of the refractive index difference, and has lower transmission loss and spatial mode dispersion and better bending performance.
  • FIG. 1 is a diagram showing the refractive index profile structure distribution of the transmission core of the coupled multi-core optical fiber of the present invention.
  • FIG2 is a schematic diagram of the radial cross-sectional structure of the coupled multi-core optical fiber according to Example 1 of the present invention.
  • FIG. 3 is a diagram showing the refractive index profile structure distribution of the coupled multi-core optical fiber according to Example 1 of the present invention.
  • FIG. 4 is a schematic diagram of the radial cross-sectional structure of a coupled multi-core optical fiber according to Embodiment 2 of the present invention.
  • the present invention provides a coupled multi-core optical fiber, comprising a core unit and an optical fiber cladding surrounding the core unit;
  • the fiber core unit includes a plurality of transmission fiber cores 11, each transmission fiber core 11 includes a core layer 111 and a core cladding layer 112 surrounding the core layer 111; the plurality of transmission fiber cores 11 are evenly distributed in the optical fiber cladding layer 2;
  • the optical fiber cladding 2 surrounding the transmission core includes an inner cladding 21 and an annular outer cladding 22;
  • the refractive index profile of the multi-core optical fiber is a step-type profile structure
  • No transmission core is arranged at the center of the multi-core optical fiber.
  • the spacing ⁇ between two adjacent transmission cores in the drawn optical fiber is less than or equal to 35 ⁇ m, more preferably less than or equal to 25 ⁇ m and greater than or equal to 20 ⁇ m.
  • the radius R1 of the core layer of the transmission fiber core is greater than or equal to 3.0 ⁇ m and less than or equal to 6.25 ⁇ m, more preferably greater than or equal to 4.0 ⁇ m and less than or equal to 6.0 ⁇ m; the ratio of the radius R2 of the core cladding of the transmission fiber core to the radius R1 of the core layer is 1.0 to 3.0.
  • the radius R3 of the optical fiber cladding (radius of the inner cladding) is preferably greater than or equal to 23.0 ⁇ m and less than 62.5 ⁇ m.
  • the radius R4 of the optical fiber cladding (outer radius of the outer cladding) is preferably 62.5 ⁇ m.
  • the core layer of the transmission fiber core is a germanium-doped silica core layer or an alkali metal-doped silica core layer; when the core layer is alkali metal-doped silica, the average concentration of the alkali metal is greater than or equal to 5 ppm and less than or equal to 100 ppm; the alkali metal is preferably at least one of lithium, sodium, potassium, and rubidium.
  • the core cladding of the transmission fiber core is a fluorine-doped silica cladding; the inner cladding of the optical fiber cladding is a fluorine-doped silica cladding, and the outer cladding of the optical fiber cladding is a fluorine-doped silica cladding or a pure silica cladding.
  • the refractive index difference ⁇ N1 of the core layer relative to pure silica is -0.0005 to 0.0058; the refractive index difference ⁇ N2 of the core cladding relative to pure silica is -0.0060 to -0.0005.
  • the refractive index difference ⁇ N3 of the inner cladding relative to pure silica is smaller than the refractive index difference ⁇ N4 of the outer cladding relative to pure silica; preferably, the refractive index difference ⁇ N3 of the inner cladding relative to pure silica is -0.0080 to -0.0010; the refractive index difference ⁇ N4 of the outer cladding relative to pure silica is -0.0055 to 0.
  • the multiple transmission fiber cores are symmetrically distributed in a regular quadrilateral or a regular hexagon, or in other uniformly symmetrical distribution forms.
  • the transmission loss of the transmission optical fiber of the present invention at 1550 nm is less than or equal to 0.22 dB/Km, more preferably less than or equal to 0.16 dB/Km.
  • the fiber core unit also includes a marking fiber core 12, which is close to any one of the transmission fiber cores 11.
  • the marking fiber core is used to confirm the position of each transmission fiber core of the multi-core optical fiber for fusion splicing. After drawing, the radius of the marking fiber core is greater than or equal to 2.5 ⁇ m and less than or equal to 4 ⁇ m; the marking fiber core is a germanium-doped silica fiber core; the refractive index difference of the marking fiber core relative to pure silica is 0.0030 to 0.0040.
  • the method for preparing the coupled multi-core optical fiber comprises the following steps:
  • the coupled multi-core optical fiber of the second embodiment includes a core unit and an optical fiber cladding surrounding the core unit;
  • the fiber core unit includes four transmission fiber cores 11 and one marking fiber core 12; each transmission fiber core 11 includes a core layer 111 and a core cladding 112 surrounding the core layer 111; the four transmission fiber cores 11 are distributed in a square shape around the center of the optical fiber in the optical fiber cladding 2; the marking fiber core 12 is close to any one of the transmission fiber cores 11; the optical fiber cladding 2 surrounding the fiber core unit includes an inner cladding 21 and an annular outer cladding 22; the refractive index profile of the multi-core optical fiber is a step-type profile structure; no transmission fiber core is arranged at the center of the multi-core optical fiber.
  • the radius R1 of the core layer of the transmission fiber core after drawing is 4.3 ⁇ m
  • the radius R2 of the core cladding of the transmission fiber core is 8.6 ⁇ m
  • the outer radius R4 of the outer cladding is 62.5 ⁇ m
  • the spacing ⁇ between two adjacent transmission fiber cores is 20 ⁇ m.
  • the core layer of the transmission fiber core is a germanium-doped silica core layer; the refractive index difference ⁇ N1 of the core layer relative to pure silica is 0.0050.
  • the core cladding of the transmission fiber core is a fluorine-doped silica cladding; the refractive index difference ⁇ N2 of the core cladding relative to pure silica is -0.0010.
  • the inner cladding of the optical fiber cladding is a fluorine-doped silica cladding
  • the outer cladding of the optical fiber cladding is a pure silica cladding.
  • the refractive index difference between the inner cladding and pure silica is equal to the refractive index difference between the core cladding and pure silica.
  • the preparation method of the coupled multi-core optical fiber of Example 1 is as follows:
  • a fluorine-doped core rod is prepared by VAD process, the core rod is processed into a target rod with a target diameter by extension and external grinding process, and then an outer cladding layer of pure silica is prepared by OVD process, and finally extended to a 80-100 mm sleeve rod;
  • the transmission fiber core rod and the marking fiber core rod are prepared by VAD process, with a diameter of 90 to 120 mm;
  • the strongly coupled four-core optical fiber prepared in this embodiment 1 supports eight modes, the transmission loss of each transmission core at 1550nm is 0.198dB/Km, and the spatial mode dispersion of the optical fiber is 20.5ps/km ⁇ 0.5, which is suitable for preparing strongly coupled four-core optical fiber devices.
  • the coupled multi-core optical fiber of the second embodiment includes a core unit and an optical fiber cladding surrounding the core unit;
  • the fiber core unit includes six transmission fiber cores 11 and one marking fiber core 12; each transmission fiber core 11 includes a core layer 111 and a core cladding 112 surrounding the core layer 111; the six transmission fiber cores 11 are distributed in a regular hexagon around the center of the optical fiber in the optical fiber cladding 2; the marking fiber core 12 is close to any one of the transmission fiber cores 11; the optical fiber cladding 2 surrounding the fiber core unit includes an inner cladding 21 and an annular outer cladding 22; the refractive index profile of the multi-core optical fiber is a step-type profile structure; no transmission fiber core is arranged at the center of the multi-core optical fiber.
  • the radius R1 of the core layer of the transmission fiber core after drawing is 4.5 ⁇ m
  • the radius R2 of the core cladding of the transmission fiber core is 9.1 ⁇ m
  • the outer radius R4 of the outer cladding is 62.5 ⁇ m
  • the spacing ⁇ between two adjacent transmission fiber cores is 25 ⁇ m.
  • the core layer of the transmission fiber core is a germanium-doped silica core layer; the refractive index difference ⁇ N1 of the core layer relative to pure silica is 0.0051.
  • the core cladding of the transmission fiber core is a fluorine-doped silica cladding; the refractive index difference ⁇ N2 of the core cladding relative to pure silica is -0.0020.
  • the inner cladding of the optical fiber cladding is a fluorine-doped silica cladding
  • the outer cladding of the optical fiber cladding is a pure silica cladding.
  • the refractive index difference between the inner cladding and pure silica is equal to the refractive index difference between the core cladding and pure silica.
  • the preparation method of the coupled multi-core optical fiber of Example 2 is as follows:
  • a fluorine-doped core rod is prepared by VAD process, the core rod is processed into a target rod with a target diameter by extension and external grinding process, and then an outer cladding layer of pure silica is prepared by OVD process, and finally extended to a 80-100 mm sleeve rod;
  • the transmission fiber core rod and the marking fiber core rod are prepared by VAD process, with a diameter of 90 to 120 mm;
  • the strongly coupled six-core optical fiber prepared in Example 2 supports twelve modes, the transmission loss of each transmission core at 1550nm is 0.208dB/Km, and the spatial mode dispersion of the optical fiber is 25ps/km ⁇ 0.5, which is suitable for preparing strongly coupled six-core optical fiber devices.
  • the coupled multi-core optical fiber of the third embodiment comprises a core unit and an optical fiber cladding surrounding the core unit;
  • the fiber core unit includes four transmission fiber cores 11 and one marking fiber core 12; each transmission fiber core 11 includes a core layer 111 and a core cladding 112 surrounding the core layer 111; the four transmission fiber cores 11 are distributed in a square shape around the center of the optical fiber in the optical fiber cladding 2; the marking fiber core 12 is close to any one of the transmission fiber cores 11; the optical fiber cladding 2 surrounding the fiber core unit includes an inner cladding 21 and an annular outer cladding 22; the refractive index profile of the multi-core optical fiber is a step-type profile structure; no transmission fiber core is arranged at the center of the multi-core optical fiber.
  • the radius R1 of the core layer of the transmission fiber core after drawing is 6.0 ⁇ m
  • the radius R2 of the core cladding of the transmission fiber core is 6.0 ⁇ m
  • the outer radius R4 of the outer cladding is 62.5 ⁇ m
  • the spacing ⁇ between two adjacent transmission fiber cores is 20 ⁇ m.
  • the core layer of the transmission fiber core is an alkali metal-doped silica core layer; the refractive index difference ⁇ N1 of the core layer relative to pure silica is 0.0005.
  • the core cladding of the transmission fiber core is a fluorine-doped silica cladding; the refractive index difference ⁇ N2 of the core cladding relative to pure silica is -0.0060.
  • the inner cladding of the optical fiber cladding is a fluorine-doped silica cladding
  • the outer cladding of the optical fiber cladding is also a fluorine-doped silica cladding;
  • the refractive index difference of the inner cladding relative to pure silica is -0.0060;
  • the refractive index difference of the outer cladding relative to pure silica is -0.0040.
  • the preparation method of the coupled multi-core optical fiber of Example 3 is as follows:
  • the strongly coupled four-core optical fiber prepared in this embodiment 3 supports eight modes, the transmission loss of each transmission core at 1550nm is 0.158dB/Km, and the spatial mode dispersion of the optical fiber is 8.5ps/km ⁇ 0.5, which is suitable for large-capacity transmission systems.

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Abstract

A coupled multi-core optical fiber and a preparation method therefor. The coupled multi-core optical fiber comprises a fiber core unit and an optical fiber cladding (2) surrounding the fiber core unit, wherein the fiber core unit comprises a plurality of transmission fiber cores (11), and each transmission fiber core (11) comprises a core (111) and a fiber core cladding (112) surrounding the core (111); the plurality of transmission fiber cores (11) are uniformly distributed in the optical fiber cladding (2); the optical fiber cladding (2) surrounding the transmission fiber cores (11) comprises an inner cladding (21) and an annular outer cladding (22); and the refractive index profile of the multi-core optical fiber is of a step-index profile structure, and the transmission fiber cores (11) are not arranged at the center of the multi-core optical fiber. The coupled multi-core optical fiber has relatively low transmission loss and spatial mode dispersion, and has a better bending performance.

Description

一种耦合型多芯光纤及其制备方法A coupled multi-core optical fiber and a method for preparing the same 技术领域Technical Field
本发明属于通信光纤技术领域，特别涉及一种耦合型多芯光纤及其制备方法。The invention belongs to the technical field of communication optical fibers, and in particular relates to a coupled multi-core optical fiber and a preparation method thereof.
背景技术Background technique
基于空分复用技术(SDM)的多芯光纤可以实现通信容量成倍的增长，可以突破单模光纤的通信容量极限。按芯间耦合类型可以将多芯光纤划分为弱耦合多芯光纤和强耦合多芯光纤。弱耦合多芯光纤为实现较弱的芯间耦合，芯间距较大，这牺牲了纤芯密度。同时为容纳更多的纤芯，需增加光纤的包层直径，这影响光纤的强度及弯曲性能。强耦合多芯光纤芯间距足够近，使各纤芯产生串扰，但产生的串扰可以通过多输入多输出(MIMO)技术处理进行解码，实现模分复用传输。Multi-core optical fiber based on space division multiplexing (SDM) technology can achieve an exponential increase in communication capacity and break through the communication capacity limit of single-mode optical fiber. According to the type of inter-core coupling, multi-core optical fiber can be divided into weakly coupled multi-core optical fiber and strongly coupled multi-core optical fiber. In order to achieve weaker inter-core coupling, the core spacing of weakly coupled multi-core optical fiber is larger, which sacrifices the core density. At the same time, in order to accommodate more cores, the cladding diameter of the optical fiber needs to be increased, which affects the strength and bending performance of the optical fiber. The core spacing of strongly coupled multi-core optical fiber is close enough to cause crosstalk between the cores, but the generated crosstalk can be decoded through multiple-input multiple-output (MIMO) technology processing to achieve mode division multiplexing transmission.
强耦合型多芯光纤由于各芯模场相互叠加形成超模，使光纤的有效面积增大，有利于降低非线性效应。同时由于强耦合多芯光纤的芯间距较小，在光纤设计时相同包层直径下可以容纳更多的纤芯。基于SDM系统强耦合多芯光纤设计要点包括以下方面：(1)模式间的有效折射率差应足够大以避免模式耦合；(2)各模式的模式损耗应相同或相差足够小；(3)下陷包层的存在有利于改善宏弯性能；(4)超模的模式时延(DMD)及空间模式色散(SMD)应尽可能小以降低MIMO系统的复杂性。Since the core mode fields of strongly coupled multi-core optical fibers are superimposed on each other to form supermodes, the effective area of the optical fiber is increased, which is beneficial to reducing nonlinear effects. At the same time, since the core spacing of strongly coupled multi-core optical fibers is small, more cores can be accommodated under the same cladding diameter when designing optical fibers. The key points of strongly coupled multi-core optical fibers based on SDM systems include the following aspects: (1) The effective refractive index difference between modes should be large enough to avoid mode coupling; (2) The mode loss of each mode should be the same or the difference should be small enough; (3) The presence of a depressed cladding is beneficial to improving macrobending performance; (4) The mode delay (DMD) and spatial mode dispersion (SMD) of the supermode should be as small as possible to reduce the complexity of the MIMO system.
综上所述，降低强耦合多芯光纤的传输损耗及空间模式色散，同时改善宏弯性能是实现强耦合多芯光纤应用亟需改善的问题。In summary, reducing the transmission loss and spatial mode dispersion of strongly coupled multi-core optical fibers and improving the macrobending performance are issues that need to be urgently improved in order to realize the application of strongly coupled multi-core optical fibers.
专利申请CN107179581A提出了一种耦合性多芯制备方法，但主要关注光纤的传输损耗而未关注光纤的空间模式色散及宏弯性能。Patent application CN107179581A proposes a coupled multi-core preparation method, but mainly focuses on the transmission loss of the optical fiber but does not pay attention to the spatial mode dispersion and macrobending performance of the optical fiber.
发明内容Summary of the invention
为解决上述技术问题，本发明的目的在于提供一种耦合型多芯光纤及其制备方法，该耦合型多芯光纤具有较低的传输损耗和空间模式色散以及较优的弯曲性能。In order to solve the above technical problems, the object of the present invention is to provide a coupled multi-core optical fiber and a preparation method thereof, wherein the coupled multi-core optical fiber has lower transmission loss and spatial mode dispersion and better bending performance.
为实现上述技术目的，达到上述技术效果，本发明通过以下技术方案实现：In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:
一种耦合型多芯光纤，包括纤芯单元和包围该纤芯单元的光纤包层；A coupled multi-core optical fiber comprises a core unit and an optical fiber cladding surrounding the core unit;
纤芯单元包括多个传输纤芯，每个传输纤芯包括芯层和包围该芯层的纤芯包层；该多个传输纤芯在光纤包层中呈均匀分布；The fiber core unit includes a plurality of transmission fiber cores, each of which includes a core layer and a core cladding layer surrounding the core layer; the plurality of transmission fiber cores are evenly distributed in the optical fiber cladding layer;
包围传输纤芯的光纤包层包括内包层和环形的外包层；The optical fiber cladding surrounding the transmission core includes an inner cladding and an annular outer cladding;
该多芯光纤的折射率剖面为阶跃型剖面结构；The refractive index profile of the multi-core optical fiber is a step-type profile structure;
该多芯光纤的中心处不设置传输纤芯。No transmission core is arranged at the center of the multi-core optical fiber.
进一步的，所述纤芯单元还包括标记纤芯，标记纤芯靠近其中任意一个传输纤芯。Furthermore, the fiber core unit also includes a marking fiber core, and the marking fiber core is close to any one of the transmission fiber cores.
进一步的，相邻两个传输纤芯的间距为小于或等于35μm，更优选为小于等于25μm且大于等于20μm。Furthermore, the distance between two adjacent transmission fiber cores is less than or equal to 35 μm, more preferably less than or equal to 25 μm and greater than or equal to 20 μm.
进一步的，传输纤芯的芯层的半径大于或等于3.0μm且小于或等于6.25μm，更优选为大于等于4.0μm且小于等于6.0μm；传输纤芯的纤芯包层的半径与芯层的半径之比为1.0～3.0。Furthermore, the radius of the core layer of the transmission fiber core is greater than or equal to 3.0 μm and less than or equal to 6.25 μm, more preferably greater than or equal to 4.0 μm and less than or equal to 6.0 μm; the ratio of the radius of the core cladding layer of the transmission fiber core to the radius of the core layer is 1.0 to 3.0.
进一步的，所述光纤包层的半径为62.5μm。Furthermore, the radius of the optical fiber cladding is 62.5 μm.
进一步的，芯层相对于纯二氧化硅的折射率差△N1为-0.0005～0.0058；纤芯包层相对于纯二氧化硅的折射率差△N2为-0.0060～-0.0005。Furthermore, the refractive index difference ΔN1 of the core layer relative to pure silica is -0.0005 to 0.0058; the refractive index difference ΔN2 of the core cladding layer relative to pure silica is -0.0060 to -0.0005.
进一步的，内包层相对于纯二氧化硅的折射率差△N3小于外包层相对于纯二氧化硅的折射率差△N4；优选的，所述内包层相对于纯二氧化硅的折射率差△N3为-0.0080～-0.0010；所述外包层相对于纯二氧化硅的折射率差△N4为-0.0055～0。Furthermore, the refractive index difference ΔN3 of the inner cladding relative to pure silica is smaller than the refractive index difference ΔN4 of the outer cladding relative to pure silica; preferably, the refractive index difference ΔN3 of the inner cladding relative to pure silica is -0.0080 to -0.0010; the refractive index difference ΔN4 of the outer cladding relative to pure silica is -0.0055 to 0.
进一步的，所述芯层为掺锗二氧化硅芯层或掺碱金属二氧化硅芯层；所述纤芯包层为掺氟二氧化硅包层。Furthermore, the core layer is a germanium-doped silica core layer or an alkali metal-doped silica core layer; and the core cladding is a fluorine-doped silica cladding.
进一步的，所述标记纤芯的半径大于或等于2.5μm且小于或等于4μm；该标记纤芯为锗掺杂二氧化硅纤芯；标记纤芯相对于纯二氧化硅的折射率差为0.0030～0.0040。Furthermore, the radius of the marking fiber core is greater than or equal to 2.5 μm and less than or equal to 4 μm; the marking fiber core is a germanium-doped silica fiber core; and the refractive index difference of the marking fiber core relative to pure silica is 0.0030-0.0040.
该耦合型多芯光纤的制备方法，包括如下步骤：The method for preparing the coupled multi-core optical fiber comprises the following steps:
(1)首先制备由内包层和外包层构成的套柱胚棒以及纤芯单元中的各个芯棒(传输纤芯和标记纤芯)；(1) First, a sleeve rod consisting of an inner cladding and an outer cladding and each core rod in the core unit (transmission core and marking core) are prepared;
(2)将纤芯单元的各个芯棒的直径延伸至目标匹配直径；(2) extending the diameter of each core rod of the core unit to a target matching diameter;
(3)利用高精度钻孔设备按设计的孔分布图依次在套柱胚棒上进行钻孔，制得套柱；(3) using high-precision drilling equipment to drill holes on the sleeve column embryo rod in sequence according to the designed hole distribution map to produce the sleeve column;
(4)将纤芯单元的各个芯棒与套柱的对应孔组装，获得强耦合多芯光纤光棒，将光棒通过后续的拉丝工艺，制得该耦合型多芯光纤。(4) Assembling the core rods of the core unit with the corresponding holes of the sleeve to obtain a strongly coupled multi-core optical fiber rod, and subjecting the rod to a subsequent drawing process to obtain the coupled multi-core optical fiber.
本发明的有益效果：Beneficial effects of the present invention:
本发明的光纤结构的中心处不设置纤芯，可以使各传输纤芯之间能够更有效的耦合；The optical fiber structure of the present invention does not have a fiber core at the center, so that each transmission fiber core can be more effectively coupled;
本发明的光纤的折射率剖面采用阶跃型剖面结构，可以提升模式间的有效折射率差，避免高阶模式耦合；The refractive index profile of the optical fiber of the present invention adopts a step-type profile structure, which can increase the effective refractive index difference between modes and avoid high-order mode coupling;
本发明的光纤具有内包层和外包层，外包层为环形结构，可以有效改善该耦合多芯光纤的弯曲性能；The optical fiber of the present invention has an inner cladding and an outer cladding, and the outer cladding is a ring structure, which can effectively improve the bending performance of the coupled multi-core optical fiber;
本发明的光纤通过纤芯和包层的结构设计以及折射率差设计，可以满足大容量传输需求，并且具有较低的传输损耗和空间模式色散以及较优的弯曲性能。The optical fiber of the present invention can meet the demand for large-capacity transmission through the structural design of the core and the cladding and the design of the refractive index difference, and has lower transmission loss and spatial mode dispersion and better bending performance.
附图说明BRIEF DESCRIPTION OF THE DRAWINGS
图1为本发明的耦合型多芯光纤的传输纤芯的折射率剖面结构分布图。FIG. 1 is a diagram showing the refractive index profile structure distribution of the transmission core of the coupled multi-core optical fiber of the present invention.
图2为本发明实施例1的耦合型多芯光纤的径向截面结构示意图。FIG2 is a schematic diagram of the radial cross-sectional structure of the coupled multi-core optical fiber according to Example 1 of the present invention.
图3为本发明实施例1的耦合型多芯光纤的折射率剖面结构分布图。FIG. 3 is a diagram showing the refractive index profile structure distribution of the coupled multi-core optical fiber according to Example 1 of the present invention.
图4为本发明实施例2的耦合型多芯光纤的径向截面结构示意图。FIG. 4 is a schematic diagram of the radial cross-sectional structure of a coupled multi-core optical fiber according to Embodiment 2 of the present invention.
具体实施方式Detailed ways
下面将结合具体实施例对本发明中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。The technical solutions in the present invention will be described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
如图2和图4所示，本发明提供了一种耦合型多芯光纤，包括纤芯单元和包围该纤芯单元的光纤包层；As shown in FIG. 2 and FIG. 4 , the present invention provides a coupled multi-core optical fiber, comprising a core unit and an optical fiber cladding surrounding the core unit;
纤芯单元包括多个传输纤芯11，每个传输纤芯11包括芯层111和包围该芯层111的纤芯包层112；该多个传输纤芯11在光纤包层2中呈均匀分布；The fiber core unit includes a plurality of transmission fiber cores 11, each transmission fiber core 11 includes a core layer 111 and a core cladding layer 112 surrounding the core layer 111; the plurality of transmission fiber cores 11 are evenly distributed in the optical fiber cladding layer 2;
包围传输纤芯的光纤包层2包括内包层21和环形的外包层22；The optical fiber cladding 2 surrounding the transmission core includes an inner cladding 21 and an annular outer cladding 22;
该多芯光纤的折射率剖面为阶跃型剖面结构；The refractive index profile of the multi-core optical fiber is a step-type profile structure;
该多芯光纤的中心处不设置传输纤芯。No transmission core is arranged at the center of the multi-core optical fiber.
其中，拉丝后的光纤中的相邻两个传输纤芯的间距Λ为小于或等于35μm，更优选为小于等于25μm且大于等于20μm。The spacing Λ between two adjacent transmission cores in the drawn optical fiber is less than or equal to 35 μm, more preferably less than or equal to 25 μm and greater than or equal to 20 μm.
其中，拉丝后，传输纤芯的芯层的半径R1大于或等于3.0μm且小于或等于6.25μm，更优选为大于等于4.0μm且小于等于6.0μm；传输纤芯的纤芯包层的半径R2与芯层的半径R1之比为1.0～3.0。Among them, after drawing, the radius R1 of the core layer of the transmission fiber core is greater than or equal to 3.0μm and less than or equal to 6.25μm, more preferably greater than or equal to 4.0μm and less than or equal to 6.0μm; the ratio of the radius R2 of the core cladding of the transmission fiber core to the radius R1 of the core layer is 1.0 to 3.0.
其中，拉丝后，所述光纤包层的半径R3(内包层的半径)优选为大于或等于23.0μm且小于62.5μm。Wherein, after drawing, the radius R3 of the optical fiber cladding (radius of the inner cladding) is preferably greater than or equal to 23.0 μm and less than 62.5 μm.
其中，拉丝后，所述光纤包层的半径R4(外包层的外半径)优选为62.5μm。Wherein, after drawing, the radius R4 of the optical fiber cladding (outer radius of the outer cladding) is preferably 62.5 μm.
其中，传输纤芯的芯层为掺锗二氧化硅芯层或掺碱金属二氧化硅芯层；当芯层为掺碱金属二氧化硅时，碱金属的平均浓度大于或等于5ppm且小于或等于100ppm；碱金属优选为锂、钠、钾、铷中的至少一种。Among them, the core layer of the transmission fiber core is a germanium-doped silica core layer or an alkali metal-doped silica core layer; when the core layer is alkali metal-doped silica, the average concentration of the alkali metal is greater than or equal to 5 ppm and less than or equal to 100 ppm; the alkali metal is preferably at least one of lithium, sodium, potassium, and rubidium.
传输纤芯的纤芯包层为掺氟二氧化硅包层；光纤包层的内包层为掺氟二氧化硅包层，光纤包层的外包层为掺氟二氧化硅包层或纯二氧化硅包层。The core cladding of the transmission fiber core is a fluorine-doped silica cladding; the inner cladding of the optical fiber cladding is a fluorine-doped silica cladding, and the outer cladding of the optical fiber cladding is a fluorine-doped silica cladding or a pure silica cladding.
其中，如图1所示，芯层相对于纯二氧化硅的折射率差△N1为-0.0005～0.0058；纤芯包层相对于纯二氧化硅的折射率差△N2为-0.0060～-0.0005。As shown in FIG1 , the refractive index difference ΔN1 of the core layer relative to pure silica is -0.0005 to 0.0058; the refractive index difference ΔN2 of the core cladding relative to pure silica is -0.0060 to -0.0005.
其中，内包层相对于纯二氧化硅的折射率差△N3小于外包层相对于纯二 氧化硅的折射率差△N4；优选的，内包层相对于纯二氧化硅的折射率差△N3为-0.0080～-0.0010；所述外包层相对于纯二氧化硅的折射率差△N4为-0.0055～0。Among them, the refractive index difference ΔN3 of the inner cladding relative to pure silica is smaller than the refractive index difference ΔN4 of the outer cladding relative to pure silica; preferably, the refractive index difference ΔN3 of the inner cladding relative to pure silica is -0.0080 to -0.0010; the refractive index difference ΔN4 of the outer cladding relative to pure silica is -0.0055 to 0.
其中的多个传输纤芯为对称分布，其分布方式为正四边形或正六边形，也可以为其他均匀对称分布方式。The multiple transmission fiber cores are symmetrically distributed in a regular quadrilateral or a regular hexagon, or in other uniformly symmetrical distribution forms.
本发明的传输光纤的1550nm处传输损耗小于或等于0.22dB/Km，更优选的是小于或等于0.16dB/Km。The transmission loss of the transmission optical fiber of the present invention at 1550 nm is less than or equal to 0.22 dB/Km, more preferably less than or equal to 0.16 dB/Km.
所述纤芯单元还包括标记纤芯12，标记纤芯12靠近其中任意一个传输纤芯11。标记纤芯用于多芯光纤的各传输纤芯的位置确认，以便于进行熔接。拉丝后，标记纤芯的半径大于或等于2.5μm且小于或等于4μm；该标记纤芯为锗掺杂二氧化硅纤芯；标记纤芯相对于纯二氧化硅的折射率差为0.0030～0.0040。The fiber core unit also includes a marking fiber core 12, which is close to any one of the transmission fiber cores 11. The marking fiber core is used to confirm the position of each transmission fiber core of the multi-core optical fiber for fusion splicing. After drawing, the radius of the marking fiber core is greater than or equal to 2.5 μm and less than or equal to 4 μm; the marking fiber core is a germanium-doped silica fiber core; the refractive index difference of the marking fiber core relative to pure silica is 0.0030 to 0.0040.
该耦合型多芯光纤的制备方法，包括如下步骤：The method for preparing the coupled multi-core optical fiber comprises the following steps:
(1)首先制备纤芯单元中的各个芯棒，即传输纤芯和标记纤芯，并制备套柱胚棒(光纤包层)(1) First, prepare the core rods in the core unit, namely the transmission core and the marking core, and prepare the sleeve rod (optical fiber cladding)
(2)将纤芯单元的各个芯棒的直径延伸至目标匹配直径；(2) extending the diameter of each core rod of the core unit to a target matching diameter;
(3)利用高精度钻孔设备按设计的孔分布图依次在套柱胚棒上进行钻孔，制得套柱，孔的数量与纤芯单元的芯棒的数量相等；(3) using a high-precision drilling device to drill holes on the sleeve rod in sequence according to the designed hole distribution diagram to produce the sleeve, and the number of holes is equal to the number of core rods of the core unit;
(4)将纤芯单元的各个芯棒与套柱的对应孔组装，获得强耦合多芯光纤光棒，将光棒通过后续的拉丝工艺，制得该耦合型多芯光纤。(4) Assembling the core rods of the core unit with the corresponding holes of the sleeve to obtain a strongly coupled multi-core optical fiber rod, and subjecting the rod to a subsequent drawing process to obtain the coupled multi-core optical fiber.
实施例1Example 1
如图2所示，该实施例2的耦合型多芯光纤，包括纤芯单元和包围该纤芯单元的光纤包层；As shown in FIG2 , the coupled multi-core optical fiber of the second embodiment includes a core unit and an optical fiber cladding surrounding the core unit;
该纤芯单元包括四个传输纤芯11和一个标记纤芯12；每个传输纤芯11包括芯层111和包围该芯层111的纤芯包层112；该四个传输纤芯11在光纤包层2中围绕光纤中心呈正方形分布；标记纤芯12靠近任意一个传输纤芯11；包围纤芯单元的光纤包层2包括内包层21和环形的外包层22；该多芯光纤的折射率剖面为阶跃型剖面结构；该多芯光纤的中心处不设置传输纤芯。The fiber core unit includes four transmission fiber cores 11 and one marking fiber core 12; each transmission fiber core 11 includes a core layer 111 and a core cladding 112 surrounding the core layer 111; the four transmission fiber cores 11 are distributed in a square shape around the center of the optical fiber in the optical fiber cladding 2; the marking fiber core 12 is close to any one of the transmission fiber cores 11; the optical fiber cladding 2 surrounding the fiber core unit includes an inner cladding 21 and an annular outer cladding 22; the refractive index profile of the multi-core optical fiber is a step-type profile structure; no transmission fiber core is arranged at the center of the multi-core optical fiber.
其中，拉丝后的传输纤芯的芯层的半径R1为4.3μm；传输纤芯的纤芯包层的半径R2为8.6μm。外包层的外半径R4为62.5μm。相邻两个传输纤芯的间距Λ为20μm。The radius R1 of the core layer of the transmission fiber core after drawing is 4.3 μm, the radius R2 of the core cladding of the transmission fiber core is 8.6 μm, the outer radius R4 of the outer cladding is 62.5 μm, and the spacing Λ between two adjacent transmission fiber cores is 20 μm.
其中，传输纤芯的芯层为掺锗二氧化硅芯层；芯层相对于纯二氧化硅的折射率差△N1为0.0050。The core layer of the transmission fiber core is a germanium-doped silica core layer; the refractive index difference △N1 of the core layer relative to pure silica is 0.0050.
传输纤芯的纤芯包层为掺氟二氧化硅包层；纤芯包层相对于纯二氧化硅的折射率差△N2为-0.0010。The core cladding of the transmission fiber core is a fluorine-doped silica cladding; the refractive index difference △N2 of the core cladding relative to pure silica is -0.0010.
光纤包层的内包层为掺氟二氧化硅包层，光纤包层的外包层为纯二氧化硅包层。内包层相对于纯二氧化硅的折射率差等于纤芯包层相对于纯二氧化硅的折射率差。The inner cladding of the optical fiber cladding is a fluorine-doped silica cladding, and the outer cladding of the optical fiber cladding is a pure silica cladding. The refractive index difference between the inner cladding and pure silica is equal to the refractive index difference between the core cladding and pure silica.
该实施例1的耦合型多芯光纤的制备方法为：The preparation method of the coupled multi-core optical fiber of Example 1 is as follows:
(1)通过VAD工艺制备掺氟芯棒，将芯棒通过延伸及外圆磨工艺加工成目标直径靶棒，再利用OVD工艺制备纯二氧化硅的外包层，最后延伸至80～100mm套柱胚棒；(1) A fluorine-doped core rod is prepared by VAD process, the core rod is processed into a target rod with a target diameter by extension and external grinding process, and then an outer cladding layer of pure silica is prepared by OVD process, and finally extended to a 80-100 mm sleeve rod;
采用VAD工艺制备传输纤芯芯棒及标记纤芯芯棒，直径为90～120mm；The transmission fiber core rod and the marking fiber core rod are prepared by VAD process, with a diameter of 90 to 120 mm;
(2)将各纤芯芯棒延伸至目标匹配直径；(2) extending each fiber core rod to a target matching diameter;
(3)采用高精度钻孔设备按设计的孔分布图依次在套柱胚棒上进行钻孔，形成含有标记纤芯孔以及传输纤芯孔的套柱；(3) using high-precision drilling equipment to drill holes on the sleeve embryo rod in sequence according to the designed hole distribution map to form a sleeve containing a marking fiber core hole and a transmission fiber core hole;
(4)将传输纤芯芯棒以及标记纤芯芯棒与套柱进行组装，获得强耦合多芯光纤光棒；将光棒通过后续的拉丝工艺，制得该耦合型多芯光纤。(4) Assembling the transmission fiber core rod and the marking fiber core rod with the sleeve column to obtain a strongly coupled multi-core optical fiber light rod; and subjecting the light rod to a subsequent drawing process to obtain the coupled multi-core optical fiber.
本实施例1制备的强耦合四芯光纤支持八个模式，各传输纤芯的1550nm处传输损耗为0.198dB/Km，光纤的空间模式色散为20.5ps/km^0.5，适用于制备强耦合四芯光纤器件。The strongly coupled four-core optical fiber prepared in this embodiment 1 supports eight modes, the transmission loss of each transmission core at 1550nm is 0.198dB/Km, and the spatial mode dispersion of the optical fiber is 20.5ps/km^0.5, which is suitable for preparing strongly coupled four-core optical fiber devices.
实施例2Example 2
如图4所示，该实施例2的耦合型多芯光纤，包括纤芯单元和包围该纤芯单元的光纤包层；As shown in FIG4 , the coupled multi-core optical fiber of the second embodiment includes a core unit and an optical fiber cladding surrounding the core unit;
该纤芯单元包括六个传输纤芯11和一个标记纤芯12；每个传输纤芯11包括芯层111和包围该芯层111的纤芯包层112；该六个传输纤芯11在光纤包层2中围绕光纤中心呈正六边形分布；标记纤芯12靠近任意一个传输纤芯11；包围纤芯单元的光纤包层2包括内包层21和环形的外包层22；该多芯光纤的折射率剖面为阶跃型剖面结构；该多芯光纤的中心处不设置传输纤芯。The fiber core unit includes six transmission fiber cores 11 and one marking fiber core 12; each transmission fiber core 11 includes a core layer 111 and a core cladding 112 surrounding the core layer 111; the six transmission fiber cores 11 are distributed in a regular hexagon around the center of the optical fiber in the optical fiber cladding 2; the marking fiber core 12 is close to any one of the transmission fiber cores 11; the optical fiber cladding 2 surrounding the fiber core unit includes an inner cladding 21 and an annular outer cladding 22; the refractive index profile of the multi-core optical fiber is a step-type profile structure; no transmission fiber core is arranged at the center of the multi-core optical fiber.
其中，拉丝后的传输纤芯的芯层的半径R1为4.5μm；传输纤芯的纤芯包层的半径R2为9.1μm。外包层的外半径R4为62.5μm。相邻两个传输纤芯的间距Λ为25μm。The radius R1 of the core layer of the transmission fiber core after drawing is 4.5 μm, the radius R2 of the core cladding of the transmission fiber core is 9.1 μm, the outer radius R4 of the outer cladding is 62.5 μm, and the spacing Λ between two adjacent transmission fiber cores is 25 μm.
其中，传输纤芯的芯层为掺锗二氧化硅芯层；芯层相对于纯二氧化硅的 折射率差△N1为0.0051。Among them, the core layer of the transmission fiber core is a germanium-doped silica core layer; the refractive index difference △N1 of the core layer relative to pure silica is 0.0051.
传输纤芯的纤芯包层为掺氟二氧化硅包层；纤芯包层相对于纯二氧化硅的折射率差△N2为-0.0020。The core cladding of the transmission fiber core is a fluorine-doped silica cladding; the refractive index difference △N2 of the core cladding relative to pure silica is -0.0020.
光纤包层的内包层为掺氟二氧化硅包层，光纤包层的外包层为纯二氧化硅包层。内包层相对于纯二氧化硅的折射率差等于纤芯包层相对于纯二氧化硅的折射率差。The inner cladding of the optical fiber cladding is a fluorine-doped silica cladding, and the outer cladding of the optical fiber cladding is a pure silica cladding. The refractive index difference between the inner cladding and pure silica is equal to the refractive index difference between the core cladding and pure silica.
该实施例2的耦合型多芯光纤的制备方法为：The preparation method of the coupled multi-core optical fiber of Example 2 is as follows:
(1)通过VAD工艺制备掺氟芯棒，将芯棒通过延伸及外圆磨工艺加工成目标直径靶棒，再利用OVD工艺制备纯二氧化硅的外包层，最后延伸至80～100mm套柱胚棒；(1) A fluorine-doped core rod is prepared by VAD process, the core rod is processed into a target rod with a target diameter by extension and external grinding process, and then an outer cladding layer of pure silica is prepared by OVD process, and finally extended to a 80-100 mm sleeve rod;
采用VAD工艺制备传输纤芯芯棒及标记纤芯芯棒，直径为90～120mm；The transmission fiber core rod and the marking fiber core rod are prepared by VAD process, with a diameter of 90 to 120 mm;
(2)将各纤芯芯棒延伸至目标匹配直径；(2) extending each fiber core rod to a target matching diameter;
(3)采用高精度钻孔设备按设计的孔分布图依次在套柱胚棒上进行钻孔，形成含有标记纤芯孔以及传输纤芯孔的套柱；(3) using high-precision drilling equipment to drill holes on the sleeve embryo rod in sequence according to the designed hole distribution map to form a sleeve containing a marking fiber core hole and a transmission fiber core hole;
(4)将传输纤芯芯棒以及标记纤芯芯棒与套柱进行组装，获得强耦合多芯光纤光棒；将光棒通过后续的拉丝工艺，制得该耦合型多芯光纤。(4) Assembling the transmission fiber core rod and the marking fiber core rod with the sleeve column to obtain a strongly coupled multi-core optical fiber light rod; and subjecting the light rod to a subsequent drawing process to obtain the coupled multi-core optical fiber.
本实施例2制备的强耦合六芯光纤支持十二个模式，各传输纤芯的1550nm处传输损耗为0.208dB/Km，光纤的空间模式色散为25ps/km^0.5，适用于制备强耦合六芯光纤器件。The strongly coupled six-core optical fiber prepared in Example 2 supports twelve modes, the transmission loss of each transmission core at 1550nm is 0.208dB/Km, and the spatial mode dispersion of the optical fiber is 25ps/km^0.5, which is suitable for preparing strongly coupled six-core optical fiber devices.
实施例3Example 3
该实施例3的耦合型多芯光纤，包括纤芯单元和包围该纤芯单元的光纤 包层；The coupled multi-core optical fiber of the third embodiment comprises a core unit and an optical fiber cladding surrounding the core unit;
该纤芯单元包括四个传输纤芯11和一个标记纤芯12；每个传输纤芯11包括芯层111和包围该芯层111的纤芯包层112；该四个传输纤芯11在光纤包层2中围绕光纤中心呈正方形分布；标记纤芯12靠近任意一个传输纤芯11；包围纤芯单元的光纤包层2包括内包层21和环形的外包层22；该多芯光纤的折射率剖面为阶跃型剖面结构；该多芯光纤的中心处不设置传输纤芯。The fiber core unit includes four transmission fiber cores 11 and one marking fiber core 12; each transmission fiber core 11 includes a core layer 111 and a core cladding 112 surrounding the core layer 111; the four transmission fiber cores 11 are distributed in a square shape around the center of the optical fiber in the optical fiber cladding 2; the marking fiber core 12 is close to any one of the transmission fiber cores 11; the optical fiber cladding 2 surrounding the fiber core unit includes an inner cladding 21 and an annular outer cladding 22; the refractive index profile of the multi-core optical fiber is a step-type profile structure; no transmission fiber core is arranged at the center of the multi-core optical fiber.
其中，拉丝后的传输纤芯的芯层的半径R1为6.0μm；传输纤芯的纤芯包层的半径R2为6.0μm。外包层的外半径R4为62.5μm。相邻两个传输纤芯的间距Λ为20μm。The radius R1 of the core layer of the transmission fiber core after drawing is 6.0 μm, the radius R2 of the core cladding of the transmission fiber core is 6.0 μm, the outer radius R4 of the outer cladding is 62.5 μm, and the spacing Λ between two adjacent transmission fiber cores is 20 μm.
其中，传输纤芯的芯层为掺碱金属二氧化硅芯层；芯层相对于纯二氧化硅的折射率差△N1为0.0005。The core layer of the transmission fiber core is an alkali metal-doped silica core layer; the refractive index difference △N1 of the core layer relative to pure silica is 0.0005.
传输纤芯的纤芯包层为掺氟二氧化硅包层；纤芯包层相对于纯二氧化硅的折射率差△N2为-0.0060。The core cladding of the transmission fiber core is a fluorine-doped silica cladding; the refractive index difference △N2 of the core cladding relative to pure silica is -0.0060.
光纤包层的内包层为掺氟二氧化硅包层，光纤包层的外包层也为掺氟二氧化硅包层；内包层相对于纯二氧化硅的折射率差为-0.0060；外包层相对于纯二氧化硅的折射率差为-0.0040。The inner cladding of the optical fiber cladding is a fluorine-doped silica cladding, and the outer cladding of the optical fiber cladding is also a fluorine-doped silica cladding; the refractive index difference of the inner cladding relative to pure silica is -0.0060; the refractive index difference of the outer cladding relative to pure silica is -0.0040.
该实施例3的耦合型多芯光纤的制备方法为：The preparation method of the coupled multi-core optical fiber of Example 3 is as follows:
(1)通过VAD工艺制备掺氟芯棒，将芯棒通过延伸及外圆磨工艺加工成目标直径靶棒，再利用OVD工艺制备外包层，最后延伸至80～100mm套柱胚棒；(1) Prepare a fluorine-doped core rod by VAD process, process the core rod into a target rod with a target diameter by extension and external grinding process, then prepare the outer cladding by OVD process, and finally extend it to 80-100 mm sleeve rod;
制备传输纤芯芯棒及标记纤芯芯棒，直径为90～120mm；Prepare transmission fiber core rod and marking fiber core rod with a diameter of 90 to 120 mm;
(2)将各纤芯芯棒延伸至目标匹配直径；(2) extending each fiber core rod to a target matching diameter;
(3)采用高精度钻孔设备按设计的孔分布图依次在套柱胚棒上进行钻孔，形成含有标记纤芯孔以及传输纤芯孔的套柱；(3) using high-precision drilling equipment to drill holes on the sleeve embryo rod in sequence according to the designed hole distribution map to form a sleeve containing a marking fiber core hole and a transmission fiber core hole;
(4)将传输纤芯芯棒以及标记纤芯芯棒与套柱进行组装，获得强耦合多芯光纤光棒；将光棒通过后续的拉丝工艺，制得该耦合型多芯光纤。(4) Assembling the transmission fiber core rod and the marking fiber core rod with the sleeve column to obtain a strongly coupled multi-core optical fiber light rod; and subjecting the light rod to a subsequent drawing process to obtain the coupled multi-core optical fiber.
本实施例3制备的强耦合四芯光纤支持八个模式，各传输纤芯的1550nm处传输损耗为0.158dB/Km，光纤的空间模式色散为8.5ps/km^0.5，适用于大容量传输系统。The strongly coupled four-core optical fiber prepared in this embodiment 3 supports eight modes, the transmission loss of each transmission core at 1550nm is 0.158dB/Km, and the spatial mode dispersion of the optical fiber is 8.5ps/km^0.5, which is suitable for large-capacity transmission systems.
以上所述仅为本发明的实施例，并非因此限制本发明的专利范围，凡是利用本发明说明书及附图内容所作的等效结构或等效流程变换，或直接或间接运用在其他相关的技术领域，均同理包括在本发明的专利保护范围内。The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims (10)

  1. 一种耦合型多芯光纤，其特征在于：包括纤芯单元和包围该纤芯单元的光纤包层；A coupled multi-core optical fiber, characterized in that it comprises a core unit and an optical fiber cladding surrounding the core unit;
    纤芯单元包括多个传输纤芯，每个传输纤芯包括芯层和包围该芯层的纤芯包层；该多个传输纤芯在光纤包层中呈均匀分布；The fiber core unit includes a plurality of transmission fiber cores, each of which includes a core layer and a core cladding layer surrounding the core layer; the plurality of transmission fiber cores are evenly distributed in the optical fiber cladding layer;
    包围传输纤芯的光纤包层包括内包层和环形的外包层；The optical fiber cladding surrounding the transmission core includes an inner cladding and an annular outer cladding;
    该多芯光纤的折射率剖面为阶跃型剖面结构；The refractive index profile of the multi-core optical fiber is a step-type profile structure;
    该多芯光纤的中心处不设置传输纤芯。No transmission core is arranged at the center of the multi-core optical fiber.
  2. 根据权利要求1所述的一种耦合型多芯光纤，其特征在于：所述纤芯单元还包括标记纤芯，标记纤芯靠近其中任意一个传输纤芯。The coupled multi-core optical fiber according to claim 1 is characterized in that: the core unit also includes a marking core, and the marking core is close to any one of the transmission cores.
  3. 根据权利要求1所述的一种耦合型多芯光纤，其特征在于：相邻两个传输纤芯的间距为小于或等于35μm。The coupled multi-core optical fiber according to claim 1 is characterized in that the spacing between two adjacent transmission cores is less than or equal to 35 μm.
  4. 根据权利要求1所述的一种耦合型多芯光纤，其特征在于：传输纤芯的芯层的半径大于或等于3.0μm且小于或等于6.25μm；传输纤芯的纤芯包层的半径与芯层的半径之比为1.0～3.0。The coupled multi-core optical fiber according to claim 1 is characterized in that: the radius of the core layer of the transmission fiber core is greater than or equal to 3.0 μm and less than or equal to 6.25 μm; the ratio of the radius of the core cladding of the transmission fiber core to the radius of the core layer is 1.0 to 3.0.
  5. 根据权利要求1所述的一种耦合型多芯光纤，其特征在于：所述光纤包层的半径为62.5μm。The coupled multi-core optical fiber according to claim 1, characterized in that the radius of the optical fiber cladding is 62.5 μm.
  6. 根据权利要求1所述的一种耦合型多芯光纤，其特征在于：芯层相对于纯二氧化硅的折射率差△N1为-0.0005～0.0058；纤芯包层相对于纯二氧化硅的折射率差△N2为-0.0060～-0.0005。A coupled multi-core optical fiber according to claim 1, characterized in that: the refractive index difference ΔN1 of the core layer relative to pure silica is -0.0005 to 0.0058; the refractive index difference ΔN2 of the core cladding relative to pure silica is -0.0060 to -0.0005.
  7. 根据权利要求1所述的一种耦合型多芯光纤，其特征在于：所述内包层相对于纯二氧化硅的折射率差△N3为-0.0080～-0.0010；所述外包层相对于纯 二氧化硅的折射率差△N4为-0.0055～0。A coupled multi-core optical fiber according to claim 1, characterized in that: the refractive index difference ΔN3 of the inner cladding relative to pure silica is -0.0080 to -0.0010; the refractive index difference ΔN4 of the outer cladding relative to pure silica is -0.0055 to 0.
  8. 根据权利要求1所述的一种耦合型多芯光纤，其特征在于：所述芯层为掺锗二氧化硅芯层或掺碱金属二氧化硅芯层；所述纤芯包层为掺氟二氧化硅包层。The coupled multi-core optical fiber according to claim 1 is characterized in that: the core layer is a germanium-doped silica core layer or an alkali metal-doped silica core layer; and the core cladding is a fluorine-doped silica cladding.
  9. 根据权利要求2所述的一种耦合型多芯光纤，其特征在于：所述标记纤芯的半径大于或等于2.5μm且小于或等于4μm。The coupled multi-core optical fiber according to claim 2, characterized in that the radius of the marker core is greater than or equal to 2.5 μm and less than or equal to 4 μm.
  10. 一种权利要求1至9任一项所述的耦合型多芯光纤的制备方法，其特征在于，包括如下步骤：A method for preparing a coupled multi-core optical fiber according to any one of claims 1 to 9, characterized in that it comprises the following steps:
    (1)首先制备套柱胚棒和纤芯单元；(1) First, prepare the sleeve column embryo rod and the core unit;
    (2)将纤芯单元的各个芯棒的直径延伸至目标匹配直径；(2) extending the diameter of each core rod of the core unit to a target matching diameter;
    (3)利用高精度钻孔设备按设计的孔分布图依次在套柱胚棒上进行钻孔，制得套柱；(3) using high-precision drilling equipment to drill holes on the sleeve column embryo rod in sequence according to the designed hole distribution map to produce the sleeve column;
    (4)将纤芯单元的各个芯棒与套柱的对应孔组装，获得强耦合多芯光纤光棒，将光棒通过后续的拉丝工艺，制得该耦合型多芯光纤。(4) Assembling the core rods of the core unit with the corresponding holes of the sleeve to obtain a strongly coupled multi-core optical fiber rod, and subjecting the rod to a subsequent drawing process to obtain the coupled multi-core optical fiber.
PCT/CN2022/133377 2022-10-11 2022-11-22 Coupled multi-core optical fiber and preparation method therefor WO2024077718A1 (en)

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