WO2017101051A1 - 用于非圆对称模式的光纤耦合器 - Google Patents

用于非圆对称模式的光纤耦合器 Download PDF

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WO2017101051A1
WO2017101051A1 PCT/CN2015/097647 CN2015097647W WO2017101051A1 WO 2017101051 A1 WO2017101051 A1 WO 2017101051A1 CN 2015097647 W CN2015097647 W CN 2015097647W WO 2017101051 A1 WO2017101051 A1 WO 2017101051A1
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fiber
core
coupling region
optical fibre
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何祖源
杜江兵
马麟
李佳熊
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上海交通大学
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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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means

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  • the invention relates to a technology in the field of optical fiber communication and sensing, in particular to a fiber coupler for a non-circular symmetric mode.
  • the mode in the fiber can be expressed as LP mn , where m ⁇ 0, n ⁇ 1, and m and n are integers.
  • the LP 0n mode is a circular symmetry mode, such as LP 01 mode, LP 02 mode, and LP 03 mode.
  • the LP mn mode is a non-circular symmetry mode, such as an LP 11 mode, an LP 21 mode, and an LP 22 mode.
  • Modular multiplexing technology based on small mode fiber has emerged in this context.
  • the modular multiplexing technology makes full use of the limited stable mode in the small-mode fiber.
  • Each mode can transmit information as an independent channel, and the system capacity and spectrum efficiency are doubled.
  • the technology is considered to be the key technology for constructing future optical networks. one.
  • High-order modes play an important role in the modular multiplexing technology, and there is an urgent need for fiber couplers suitable for high-order modes.
  • the present invention is directed to the above-mentioned deficiencies of the prior art, and proposes a fiber coupler for a non-circular symmetric mode.
  • the invention relates to a fiber coupler for a non-circular symmetric mode, suitable for LP mn mode, wherein m ⁇ 1, n ⁇ 1, m and n are integers, the fiber coupler is composed of two identical fibers,
  • the length L of the coupling zone and the distance of the central axis of the core, that is, the core spacing d of the coupling zone are obtained by:
  • R is the split ratio
  • the splitting ratio refers to a ratio of light energy carried in another optical fiber to light energy carried in the optical fiber after being incident on an optical fiber in a non-circular symmetric mode.
  • Said LP mn mold can be decomposed into two orthogonal degenerate modes: LP mna LP mnb mold and die.
  • the fiber coupler can form a coupling region by, but not limited to, an etching method, a polishing method, or a fusion taper method.
  • the fiber coupler of the present invention is suitable for the non-circular symmetric mode, overcomes the influence of the mode spot rotation on the splitting ratio, and can be applied to the modular multiplexing optical fiber communication and sensing system. Further, the present invention is simple and easy to select, according to the working mode and working wavelength of the fiber coupler, the appropriate fiber is selected, and the length of the coupling region and the core spacing of the coupling region are determined according to the splitting ratio of the fiber coupler, and the coupling region can pass the corrosion. Formed by conventional methods such as the method, the polishing method, or the melt taper method.
  • FIG. 1 is a schematic structural view of a fiber coupler of the present invention
  • Figure 2 is a schematic diagram showing the simulation results of a fiber coupler (the split ratio of 30:70) suitable for the LP 11 mode;
  • Figure 3 is a schematic diagram showing the simulation results of a fiber coupler (the split ratio of 50:50) suitable for the LP 11 mode;
  • Figure 4 is a schematic diagram showing the simulation results of a fiber coupler (the split ratio of 70:30) suitable for the LP 21 mode;
  • Figure 5 is a schematic diagram showing the simulation results of a fiber coupler (the split ratio of 90:10) suitable for the LP 21 mode;
  • This embodiment relates to a fiber coupler suitable for the LP 11 mode.
  • the LP 11 mode is incident on the first fiber, and there are innumerable possibilities for the pattern of the incident LP 11 mode, as shown in Figure 2, which is four possibilities. After passing through the coupling region, the light energy carried by the first fiber and the second fiber is as shown in FIG. 2, and the rotation of the incident mode spot does not affect the splitting ratio of the coupler.
  • the cladding index n cl of the first fiber and the second fiber 1.4446.
  • the LP 11 mode is incident on the first fiber, and there are innumerable possibilities for the pattern of the incident LP 11 mode. As shown in Figure 3, there are four possibilities. After passing through the coupling region, the light energy carried by the first fiber and the second fiber is as shown in FIG. 3, and the rotation of the incident mode is not affected by the splitting ratio of the coupler.
  • This embodiment relates to a fiber coupler suitable for the LP 21 mode.
  • the cladding index n cl of the first fiber and the second fiber 1.4446.
  • the LP 21 mode is incident on the first fiber, and there are innumerable possibilities for the pattern of the incident LP 21 mode, as shown in Figure 4, which is four possibilities. After passing through the coupling region, the light energy carried by the first fiber and the second fiber is as shown in FIG. 4, and the rotation of the incident mode spot does not affect the splitting ratio of the coupler.
  • This embodiment relates to a fiber coupler suitable for the LP 21 mode.
  • the LP 21 mode is incident on the first fiber, and there are innumerable possibilities for the pattern of the incident LP 21 mode. As shown in Figure 5, there are four possibilities. After passing through the coupling region, the light energy carried by the first optical fiber and the second optical fiber is as shown in FIG. 5, and the rotation of the incident optical mode spot does not affect the splitting ratio of the coupler.

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  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

一种用于非圆对称模式的光纤耦合器，适用于LP mn模，其中m≥1，n≥1，m、n均为整数，该光纤耦合器由两根相同光纤组成，其耦合区的长度L以及纤芯间距d满足：式（I）其中，R为分光比， Ca 12为LPmna模的耦合系数，Cb 12 为LPmnb模的耦合系数，式（II）式（III）其中：ε0为真空的介电常数；ω为入射光的角频率；ρ为耦合区中第一光纤和第二光纤的纤芯半径；nco为光纤的纤芯折射率；ncl为光纤的包层折射率；Am为LPmn模的归一化常数；I为第一类修正贝塞尔函数；K为第二类修正贝塞尔函数；w为LPmn模纤芯中横向归一化传播常数；u为LPmn模包层中横向归一化传播常数。该光纤耦合器适用于非圆对称模式，克服了模斑旋转对分光比的影响，在模分复用光纤通信和传感领域具有广阔的应用前景。

Description

用于非圆对称模式的光纤耦合器 技术领域
本发明涉及的是一种光纤通信和传感领域的技术，具体是一种用于非圆对称模式的光纤耦合器。
背景技术
光纤耦合器作为最基本的无源器件，可以实现光的传输、分束、耦合以及干涉等功能，广泛应用于光纤通信和光纤传感领域。光纤中的模式可以表示为LPmn，其中m≥0，n≥1，m和n均为整数。当m＝0时，LP0n模为圆对称模式，例如LP01模、LP02模和LP03模等。当m≥1时，LPmn模为非圆对称模式，例如LP11模、LP21模和LP22模等。由于单模光纤的大量使用，目前大部分光纤耦合器只适用于圆对称的LP01模(基模)[M.J.F.Digonnet and H.J.Shaw,“Analysis of a tunable single mode optical fiber coupler,”IEEE J.Quantum Electron.18,746-754(1982)]。[0003]随着个人移动与固定带宽等通信业务的不断普及，当今社会对网络带宽的需求不断增加。为了提高光纤信道的容量，人们提出了基于单模光纤的密集波分复用、相干接收等技术。然而，由于固有的非线性效应和ASE噪声，单模光纤的信道容量已经逼近了香农极限。基于少模光纤的模分复用技术在此背景下应运而生。模分复用技术充分利用了少模光纤中有限的稳定模式，每一个模式都可以作为独立信道传递信息，系统容量和频谱效率因而成倍提高，改技术被认为是构建未来光网络的关键技术之一。高阶模式在模分复用技术中扮演了重要角色，人们迫切需要适用于高阶模式的光纤耦合器。
在实际的光纤中，沿光纤长度方向存在纤芯形状的意外改变和各向异性应力，因此少模光纤中的各个模式在传播过程中，其模斑会绕着纤芯中心轴随机旋转。对于圆对称模式而言，模斑旋转不会影响耦合器的分光比，因此适用于高阶圆对称模式的光纤耦合器容易实现，设计方法与适用于基膜的光纤耦合器类似。然而，对于非圆对称模式而言，耦合器的分光比受到模斑旋转的影响，因此适用于非圆对称模式的光纤耦合器难于实现。
发明内容
本发明针对现有技术存在的上述不足，提出一种用于非圆对称模式的光纤耦合器。
本发明是通过以下技术方案实现的：
本发明涉及一种用于非圆对称模式的光纤耦合器，适用于LPmn模，其中m≥1，n≥1，m和n均为整数，该光纤耦合器由两根相同光纤组成，其耦合区的长度L以及纤芯中心轴的距离，即耦合区纤芯间距d通过以下方式得到：
Figure PCTCN2015097647-appb-000001
其中：R为分光比，
Figure PCTCN2015097647-appb-000002
为LPmna模的耦合系数，
Figure PCTCN2015097647-appb-000003
为LPmnb模的耦合系数，
Figure PCTCN2015097647-appb-000004
Figure PCTCN2015097647-appb-000005
其中：ε0为真空的介电常数；ω为入射光的角频率；ρ为耦合区中第一光纤和第二光纤的纤芯半径；nco为光纤的纤芯折射率；ncl为光纤的包层折射率；Am为LPmn模的归一化常数；I为第一类修正贝塞尔函数；K为第二类修正贝塞尔函数；w为LPmn模纤芯中横向归一化传播常数；u为LPmn模包层中横向归一化传播常数。
所述的分光比是指：非圆对称模式入射到一根光纤，经过耦合区后，在另外一根光纤中携带的光能量与前述光纤中携带的光能量的比值。
所述的LPmn模可以分解为两个正交的简并模式：LPmna模和LPmnb模。
所述的光纤，其工作波长优选为λ＝1550nm，分光比R优选为(30～90):(70～10)，在耦合区的纤芯半径优选为ρ＝6.48μm，纤芯折射率优选为nco＝1.4546，包层折射率优选为ncl＝1.4446。
所述的光纤耦合器，可以通过但不限于腐蚀法、抛磨法或者熔融拉锥法形成耦合区。
技术效果
与现有技术相比，本发明的光纤耦合器适用于非圆对称模式，克服了其模斑旋转对分光比的影响，可以应用于模分复用光纤通信和传感系统。进一步地，本发明简单易行，根据光纤耦合器的工作模式和工作波长选择合适的光纤，根据光纤耦合器的分光比确定耦合区的长度和耦合区的纤芯间距，且耦合区可以通过腐蚀法、抛磨法或者熔融拉锥法等现有方法形成。
附图说明
图1为本发明光纤耦合器的结构示意图；
图2为适用于LP11模的光纤耦合器(分光比为30:70)仿真结果示意图；
图3为适用于LP11模的光纤耦合器(分光比为50:50)仿真结果示意图；
图4为适用于LP21模的光纤耦合器(分光比为70:30)仿真结果示意图；
图5为适用于LP21模的光纤耦合器(分光比为90:10)仿真结果示意图；
具体实施方式
实施例1
本实施例涉及一种适用于LP11模的光纤耦合器，耦合器的工作波长λ＝1550nm，分光比R为30:70。第一光纤和第二光纤在耦合区的纤芯半径ρ＝6.48μm，第一光纤和第二光纤的纤芯折射率nco＝1.4546，第一光纤和第二光纤的包层折射率ncl＝1.4446。经过计算，如图1所示的耦合区的长度L＝32.5mm，耦合区纤芯间距d＝15.6μm。
LP11模入射到第一光纤，入射的LP11模的模斑存在无数种可能，如图2所示即为其中四种可能。经过耦合区后，第一光纤和第二光纤携带的光能量如图2所示，入射光模斑的旋转不影响该耦合器的分光比。
实施例2
本实施例涉及一种适用于LP11模的光纤耦合器，耦合器的工作波长λ＝1550nm，分光比R为50:50。第一光纤和第二光纤在耦合区的纤芯半径ρ＝6.48μm，第一光纤和第二光纤的纤芯折射率nco＝1.4546，第一光纤和第二光纤的包层折射率ncl＝1.4446。经过计算，如图1所示的耦合区的长度L＝21.5mm，耦合区纤芯间距d＝16.9μm。
LP11模入射到第一光纤，入射的LP11模的模斑存在无数种可能，如图3所示即为其中四种可能。经过耦合区后，第一光纤和第二光纤携带的光能量如图3所示，入射光模斑的旋转不影响该耦合器的分光比。
实施例3
本实施例涉及一种适用于LP21模的光纤耦合器，耦合器的工作波长λ＝1550nm，分光比R为70:30。第一光纤和第二光纤在耦合区的纤芯半径ρ＝6.48μm，第一光纤和第二光纤的纤芯折射率nco＝1.4546，第一光纤和第二光纤的包层折射率ncl＝1.4446。经过计算，如图1所示的耦合区的长度L＝31.7mm，耦合区纤芯间距d＝19.2μm。
LP21模入射到第一光纤，入射的LP21模的模斑存在无数种可能，如图4所示即为其中四种可能。经过耦合区后，第一光纤和第二光纤携带的光能量如图4所示，入射光模斑的旋转不影响该耦合器的分光比。
实施例4
本实施例涉及一种适用于LP21模的光纤耦合器，耦合器的工作波长λ＝1550nm，分光比R为90:10。第一光纤和第二光纤在耦合区的纤芯半径ρ＝6.48μm，第一光纤和第二光纤的纤芯折射率nco＝1.4546，第一光纤和第二光纤的包层折射率ncl＝1.4446。经过计算，如图1所示的耦合区的长度L＝25.3mm，耦合区纤芯间距d＝18.5μm。
LP21模入射到第一光纤，入射的LP21模的模斑存在无数种可能，如图5所示即为其中四 种可能。经过耦合区后，第一光纤和第二光纤携带的光能量如图5所示，入射光模斑的旋转不影响该耦合器的分光比。
上述具体实施可由本领域技术人员在不背离本发明原理和宗旨的前提下以不同的方式对其进行局部调整，本发明的保护范围以权利要求书为准且不由上述具体实施所限，在其范围内的各个实现方案均受本发明之约束。

Claims (5)

  1. 一种用于非圆对称模式的光纤耦合器，其特征在于，适用于LPmn模，其中m≥1，n≥1，m和n均为整数，该光纤耦合器由两根相同光纤组成，其耦合区的长度L以及纤芯中心轴的距离，即耦合区纤芯间距d通过以下方式得到：
    Figure PCTCN2015097647-appb-100001
    其中：R为分光比，
    Figure PCTCN2015097647-appb-100002
    为LPmna模的耦合系数，
    Figure PCTCN2015097647-appb-100003
    为LPmnb模的耦合系数，
    Figure PCTCN2015097647-appb-100004
    Figure PCTCN2015097647-appb-100005
    其中：ε0为真空的介电常数；ω为入射光的角频率；ρ为耦合区中第一光纤和第二光纤的纤芯半径；nco为光纤的纤芯折射率；ncl为光纤的包层折射率；Am为LPmn模的归一化常数；I为第一类修正贝塞尔函数；K为第二类修正贝塞尔函数；w为LPmn模纤芯中横向归一化传播常数；u为LPmn模包层中横向归一化传播常数。
  2. 根据权利要求1所述的光纤耦合器，其特征是，所述的分光比是指：非圆对称模式入射到一根光纤，经过耦合区后，在另外一根光纤中携带的光能量与前述光纤中携带的光能量的比值。
  3. 根据权利要求1所述的光纤耦合器，其特征是，所述的LPmn模可以分解为两个正交的简并模式：LPmna模和LPmnb模。
  4. 根据权利要求1所述的光纤耦合器，其特征是，所述的光纤，其工作波长为λ＝1550nm，分光比R为(30～90):(70～10)，在耦合区的纤芯半径为ρ＝6.48μm，纤芯折射率为nco＝1.4546，包层折射率为ncl＝1.4446。
  5. 根据上述任一权利要求所述的光纤耦合器，其特征是，所述的光纤耦合器，通过腐蚀法、抛磨法或者熔融拉锥法形成其耦合区。
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CN112363320A (zh) * 2020-09-27 2021-02-12 四川长虹电器股份有限公司 一种光纤涡旋光束发生器及其制备方法
CN112363320B (zh) * 2020-09-27 2022-02-01 四川长虹电器股份有限公司 一种光纤涡旋光束发生器及其制备方法
CN112946821A (zh) * 2021-02-07 2021-06-11 中国人民解放军国防科技大学 基于套管法的模组选择光子灯笼制备方法

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