WO2023240879A1 - 一种细径单模光纤 - Google Patents

一种细径单模光纤 Download PDF

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Publication number
WO2023240879A1
WO2023240879A1 PCT/CN2022/127613 CN2022127613W WO2023240879A1 WO 2023240879 A1 WO2023240879 A1 WO 2023240879A1 CN 2022127613 W CN2022127613 W CN 2022127613W WO 2023240879 A1 WO2023240879 A1 WO 2023240879A1
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refractive index
transition
cladding layer
cladding
optical fiber
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PCT/CN2022/127613
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English (en)
French (fr)
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罗文勇
耿皓
喻煌
吴海波
陈保平
胡古月
廖伟章
黄非
黄志凌
祁庆庆
邵帅
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烽火通信科技股份有限公司
烽火藤仓光纤科技有限公司
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Publication of WO2023240879A1 publication Critical patent/WO2023240879A1/zh

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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
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G02B6/03616—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference
    • G02B6/03688—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 5 or more 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
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02295—Microstructured optical fibre
    • 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
    • G02B6/0283—Graded index region external to the central core segment, e.g. sloping layer or triangular or trapezoidal layer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
    • Y02P40/57—Improving the yield, e-g- reduction of reject rates

Definitions

  • the present application relates to the technical field of optical fiber manufacturing, and in particular to a small-diameter single-mode optical fiber.
  • Optical fiber communications are widely used as the communication method with the fastest speed and the best transmission quality.
  • In terms of network construction with the shortage of pipeline resources, users have put forward higher requirements for pipeline space utilization, construction efficiency and maintenance convenience. Air-blown microcable technology is undoubtedly a good choice.
  • informatization construction has put forward demands for ODN technology.
  • ODN technology In order to adapt to the construction of optical fiber networks and 5G networks, ODN technology has increasingly higher space requirements, often requiring a large number of equipment to be arranged in extremely small distribution boxes. At this time, there will be even less space left for optical fiber for high-speed, high-bandwidth communication connections between devices. Therefore, both large-core microcable technology and the booming ODN technology have put forward significant demands for small-diameter single-mode optical fiber technology.
  • the traditional method of reducing the overall size of single-mode optical fiber is difficult to apply to microcables and smart ODN technologies that require higher optical fiber performance.
  • the application of small-diameter single-mode optical fiber needs to rely on existing cutting and splicing equipment, so the fiber size needs to meet the requirements of existing cutting, splicing and other equipment while improving performance.
  • Embodiments of the present application provide a thin-diameter single-mode optical fiber, which uses two waveguide structures of parabolic descent and polynomial linear descent to achieve a smooth transition between the germanium-doped core layer and the outer quartz cladding, thereby reducing the stress between the core and the cladding, and reducing the fiber stress. Internal microcracks caused by stress, thereby improving its long-term reliability.
  • Embodiments of the present application provide a thin-diameter single-mode optical fiber, which includes a germanium-doped core layer, a first transition cladding, a second transition cladding, and an outer quartz cladding arranged sequentially from the inside to the outside in the radial direction;
  • the refractive index of the first transition cladding layer is less than the refractive index of the germanium-doped core layer and greater than the refractive index of the second transition cladding layer;
  • the relative refractive index difference of the first transition cladding layer decreases in a first polynomial line shape
  • the relative refractive index difference of the second transition cladding layer decreases in a second polynomial line shape
  • the refractive index of the first transition cladding is n 2
  • the refractive index of the outer quartz cladding is n 8
  • the relative refractive index difference between n 2 and n 8 is ⁇ n 2 ;
  • ⁇ n 2 [a 1 ⁇ (1-x 1 -x 1 2 )+b 1 ]/100
  • x 1 is the distance from any point in the first transition cladding layer to the center of the germanium-doped core layer, a 1 and b 1 are both transition coefficients, and the value range of a 1 is 0.15% to 0.3%, The value range of b 1 is 0.35 ⁇ 0.45.
  • the refractive index of the second transition cladding is n 3
  • the refractive index of the outer quartz cladding is n 8
  • the relative refractive index difference between n 3 and n 8 is ⁇ n 3 ;
  • ⁇ n 3 [b 2 ⁇ (1-a 2 ⁇ x 2 2 )]/100
  • x 2 is the distance from any point in the second transition cladding layer to the center of the germanium-doped core layer, a 2 and b 2 are both transition coefficients, and the value range of a 2 is 1.8% to 2.2%, The value range of b 2 is 0.6 ⁇ 0.8.
  • the radius of the germanium-doped core layer is 3.0-5.0 microns
  • the total thickness of the first transition cladding layer and the second transition cladding layer is 2.0-4.0 microns
  • the radius of the outer quartz cladding layer is 30 ⁇ 45 microns.
  • the thin-diameter single-mode optical fiber further includes a fluorine-doped concave cladding and a third transition cladding arranged sequentially from the inside to the outside in the radial direction.
  • the fluorine-doped concave cladding and the third transition cladding are The layer is located between the second transition cladding and the outer quartz cladding;
  • the refractive index of the third transition cladding layer is less than the refractive index of the outer quartz cladding layer and greater than the refractive index of the fluorine-doped concave cladding layer.
  • the refractive index of the first transition cladding is n 2
  • the refractive index of the outer quartz cladding is n 8
  • the relative refractive index difference between n 2 and n 8 is ⁇ n 2 ;
  • ⁇ n 2 [a 3 ⁇ (1-x 1 -x 1 2 -x 1 3 )+b 3 ]/100
  • x 1 is the distance from any point in the first transition cladding layer to the center of the germanium-doped core layer
  • a 3 and b 3 are both transition coefficients
  • the value range of a 3 is 0.26% to 0.30%
  • the value range of b 3 is 0.54 ⁇ 0.58.
  • the refractive index of the second transition cladding is n 3
  • the refractive index of the outer quartz cladding is n 8
  • the relative refractive index difference between n 3 and n 8 is ⁇ n 3 ;
  • ⁇ n 3 [b 4 ⁇ (1-a 4 ⁇ x 2 2 )]/100
  • x 2 is the distance from any point in the second transition cladding layer to the center of the germanium-doped core layer
  • a 4 and b 4 are both transition coefficients
  • the value range of a 4 is 2.8% to 3.2%
  • the value range of b 4 is 0.45 ⁇ 0.55.
  • the refractive index of the fluorine-doped concave cladding is n 6
  • the refractive index of the outer quartz cladding is n 8
  • the relative refractive index difference between n 6 and n 8 is ⁇ n 6 ;
  • the value range of ⁇ n 6 is -0.12% ⁇ -0.21%.
  • the radius of the germanium-doped core layer is 3.0-4.0 microns
  • the total thickness of the first transition cladding layer and the second transition cladding layer is 2.0-4.0 microns
  • the fluorine-doped concave cladding layer is The thickness is 9.0-20.0 microns
  • the radius of the outer quartz cladding is 30-45 microns.
  • the thin-diameter single-mode optical fiber further includes an inner quartz cladding and a fourth transition cladding arranged sequentially from inside to outside in the radial direction, and the inner quartz cladding and the fourth transition cladding are located on the second Between the transition cladding and the fluorine-doped concave cladding;
  • the refractive index of the fourth transition cladding layer is smaller than the refractive index of the inner quartz cladding layer and larger than the refractive index of the fluorine-doped concave cladding layer.
  • the refractive index of the first transition cladding is n 2
  • the refractive index of the outer quartz cladding is n 8
  • the relative refractive index difference between n 2 and n 8 is ⁇ n 2 ;
  • ⁇ n 2 [a 5 ⁇ (1-x 1 -x 1 2 )+b 5 ]/100
  • x 1 is the distance from any point in the first transition cladding layer to the center of the germanium-doped core layer, a 5 and b 5 are both transition coefficients, and the value range of a 5 is 0.15% to 0.30%, The value range of b 5 is 0.35 ⁇ 0.45.
  • the refractive index of the second transition cladding is n 3
  • the refractive index of the outer quartz cladding is n 8
  • the relative refractive index difference between n 3 and n 8 is ⁇ n 3 ;
  • ⁇ n 3 [b 6 ⁇ (1-a 6 ⁇ x 2 2 )]/100
  • x 2 is the distance from any point in the second transition cladding layer to the center of the germanium-doped core layer
  • a 6 and b 6 are both transition coefficients
  • the value range of a 6 is 1.8% to 2.2%
  • the value range of b 6 is 0.6 ⁇ 0.8.
  • the refractive index of the fluorine-doped concave cladding is n 6
  • the refractive index of the outer quartz cladding is n 8
  • the relative refractive index difference between n 6 and n 8 is ⁇ n 6 ;
  • the value range of ⁇ n 6 is -0.22% ⁇ -0.46%.
  • the radius of the germanium-doped core layer is 2.5-4.0 microns
  • the total thickness of the first transition cladding, the second transition cladding and the inner quartz cladding is 3.0-8.0 microns
  • the fourth The total thickness of the transition cladding, the fluorine-doped concave cladding and the third transition cladding is 9.0-25.0 microns
  • the radius of the outer quartz cladding is 30-62.5 microns.
  • the outer quartz cladding is doped with alkali metal elements or halogens for reducing its viscosity.
  • the germanium-doped core layer is doped with alkali metal elements or halogens for reducing its viscosity.
  • the alkali metal element is at least one of potassium and lithium, and the halogen is chlorine element.
  • the thin-diameter single-mode optical fiber provided in the embodiment of the present application is designed with double transition cladding around the germanium-doped core layer. They are a first transition cladding in which the relative refractive index difference decreases in a first polynomial linear shape and a relative refractive index. The difference of the second transition cladding decreases in a second polynomial linear shape to form a waveguide structure with double smooth transition cladding, optimizing the macrobending loss and The problem of increased micro-bending loss enables small-diameter single-mode optical fiber to still have excellent attenuation performance under the same external interference conditions as existing conventional optical fibers.
  • the two structures of linear decline and second polynomial linear decline achieve a smooth transition between the germanium-doped core layer and the outer quartz cladding, reduce the stress between the core and the cladding, and reduce the micro-cracks caused by stress inside the optical fiber, thus improving its long-term performance. reliability.
  • This application uses two transitional claddings and two structures of the first polynomial linear decrease and the second polynomial linear decrease to reduce the number of fine-diameter single-mode optical fibers when they are fused with existing conventional single-mode optical fibers. Serious side light leakage problem. Since the fine-diameter single-mode fiber is 30% to 50% thinner than the existing conventional single-mode fiber, the temperature at the welding point has a greater impact on the fine-diameter single-mode fiber than the conventional single-mode fiber.
  • germanium-doped core layer is doped
  • the impurity component is more likely to diffuse, thereby reducing its ability to constrain the low-loss propagation of light, causing part of the light to leak due to the reduction in NA caused by the doping and diffusion of the germanium-doped core layer. Due to the double polynomial reduction used in the structure of this application, the diffusion effect caused by heat transfer from the outer quartz cladding into the germanium-doped core layer is well weakened, thereby achieving good compatibility with existing conventional single-mode optical fibers. It is well compatible with conventional G.652 optical fiber and has low splicing loss.
  • Figure 1 is a schematic structural diagram of a thin-diameter single-mode optical fiber waveguide provided by an embodiment of the present application
  • Figure 2 is a schematic structural diagram of a thin-diameter single-mode optical fiber waveguide provided by another embodiment of the present application.
  • Figure 3 is a schematic structural diagram of a thin-diameter single-mode optical fiber waveguide provided by yet another embodiment of the present application.
  • Germanium-doped core layer 2. First transition cladding layer; 3. Second transition cladding layer; 4. Inner quartz cladding layer; 5. Fourth transition cladding layer; 6. Fluorine-doped concave cladding layer; 7. The third transitional cladding; 8. The outer quartz cladding.
  • a preferred embodiment of the present application provides a thin-diameter single-mode optical fiber, which includes a germanium-doped core layer 1, a first transition cladding 2, a second transition cladding layer 2, and a second transition cladding layer 2.
  • the relative refractive index difference of the first transition cladding layer 2 decreases in a first polynomial line shape
  • the relative refractive index difference of the second transition cladding layer 3 decreases in a second polynomial line shape.
  • the first polynomial line shape and the second polynomial line shape decrease.
  • the connection points of the linear linear connections are smoothly transitioned, so that the first transition cladding layer 2 and the second transition cladding layer 3 as a whole make a smooth transition to the waveguide structure with a difference in refractive index.
  • the relative refractive index difference of the above-mentioned first transition cladding layer 2 decreases in a first polynomial line shape
  • the relative refractive index difference of the second transition cladding layer 3 decreases in a second polynomial line shape, which means that along the radial direction from From the inside to the outside, the relative refractive index difference gradually decreases, and the relative refractive index difference satisfies the polynomial function.
  • the first polynomial function corresponding to the first polynomial line shape is different from the second polynomial function corresponding to the second polynomial.
  • the fine-diameter single-mode optical fiber provided in the embodiment of the present application is designed with double transition cladding around the germanium-doped core layer 1, which are a first transition cladding 2 in which the relative refractive index difference decreases in a first polynomial linear shape and a relative
  • the second transition cladding 3 whose refractive index difference decreases in a second polynomial linear shape forms a waveguide structure with double smooth transition cladding, which strengthens the resistance of the small-diameter optical fiber against external forces from two aspects: reducing macro-bending loss and micro-bending loss.
  • This application uses the following formula to calculate the relative refractive index difference ⁇ n i :
  • n 8 is the refractive index of the outer quartz cladding 8.
  • n i in the formula is the first transition cladding.
  • the refractive index n 2 of layer 2; when calculating the relative refractive index difference ⁇ n 3 between the second transition cladding 3 and the outer quartz cladding 8, n i in the formula is the refractive index n 3 of the second transition cladding 3; other parameters layers and so on.
  • the refractive index of the first transition cladding layer 2 is n 2
  • the refractive index of the outer quartz cladding layer 8 is n 8
  • the relative refractive index difference between n 2 and n 8 is ⁇ n 2 ;
  • ⁇ n 2 [a 1 ⁇ (1-x 1 -x 1 2 )+b 1 ]/100
  • x 1 is the distance from any point in the first transition cladding layer 2 to the center of the germanium-doped core layer 1
  • a 1 and b 1 are both transition coefficients
  • the value range of a 1 is 0.15% to 0.3%
  • b 1 The value range is 0.35 ⁇ 0.45.
  • the refractive index of the second transition cladding layer 3 is n 3
  • the refractive index of the outer quartz cladding layer 8 is n 8
  • the relative refractive index difference between n 3 and n 8 is ⁇ n 3 ;
  • ⁇ n 3 [b 2 ⁇ (1-a 2 ⁇ x 2 2 )]/100
  • x 2 is the distance from any point in the second transition cladding layer 3 to the center of the germanium-doped core layer 1
  • a 2 and b 2 are both transition coefficients, and the value range of a 2 is 1.8% to 2.2%, and b 2 The value range is 0.6 ⁇ 0.8.
  • the radius of the germanium-doped core layer 1 is 3.0 to 5.0 microns
  • the total thickness of the first transition cladding layer 2 and the second transition cladding layer 3 is 2.0 to 4.0 microns
  • the outer quartz cladding layer The radius of 8 is 30 to 45 microns.
  • the diameter of the outer coating of the small-diameter single-mode optical fiber ranges from 100.0 to 125.0 microns.
  • the diameter of the outer coating of the small-diameter single-mode optical fiber ranges from 135.0 to 200.0 microns.
  • the outer quartz cladding 8 in FIG. 1 can be doped with alkali metal elements or halogens for reducing its viscosity.
  • the alkali metal element is at least one of potassium and lithium
  • the halogen is chlorine element.
  • the outer quartz cladding 8 of Example 1 contains potassium, and the attenuation at 1550nm is 0.171dB/km. Its fusion loss with conventional G.652 optical fiber reaches 0.18dB, and its additional loss at a bending radius of 5mm is 0.21dB.
  • the outer quartz cladding 8 of Example 2 contains lithium and has an attenuation of 0.175dB/km at 1550nm. Its fusion loss with conventional G.652 optical fiber reaches 0.16dB, and its additional loss at a bending radius of 5mm is 0.19dB.
  • the outer quartz cladding 8 of Example 3 contains chlorine, and the attenuation at 1550nm is 0.157dB/km. Its fusion loss with conventional G.652 optical fiber reaches 0.10dB, and its additional loss at a bending radius of 5mm is 0.35dB;
  • the outer quartz cladding 8 of Example 4 contains potassium, and the attenuation at 1550nm is 0.158dB/km. Its fusion loss with conventional G.652 optical fiber reaches 0.09dB, and its additional loss at a bending radius of 5mm is 0.29dB.
  • the outer quartz cladding 8 of Example 5 is not doped with other elements, and has an attenuation of 0.179 dB/km at 1550 nm. Its fusion loss with conventional G.652 optical fiber reaches 0.08 dB, and its additional loss at a bending radius of 5 mm is 0.46 dB.
  • the above five embodiments realize the waveguide structure design of a small-diameter single-mode optical fiber that has good compatibility with existing conventional single-mode optical fibers, can be well compatible with conventional G.652 optical fibers, and has low splicing loss.
  • a fluorine-doped concave cladding layer 6 can be added around the germanium-doped core layer 1. Specifically, see Figure 2.
  • a small-diameter single-mode The optical fiber also includes a fluorine-doped concave cladding 6 and a third transition cladding 7 arranged sequentially from the inside to the outside in the radial direction.
  • the fluorine-doped concave cladding 6 and the third transition cladding 7 are located between the second transition cladding 3 and the third transition cladding 7 .
  • the refractive index of the third transition cladding 7 is smaller than the refractive index of the outer quartz cladding 8, and greater than the refractive index of the fluorine-doped concave cladding 6.
  • a third transition cladding layer 7 is provided between the fluorine-doped concave cladding layer 6 and the outer quartz cladding layer 8 to reduce stress between cores and claddings.
  • the refractive index of the first transition cladding layer 2 is n 2
  • the refractive index of the outer quartz cladding layer 8 is n 8
  • the relative refractive index difference between n 2 and n 8 is ⁇ n 2 ;
  • ⁇ n 2 [a 3 ⁇ (1-x 1 -x 1 2 -x 1 3 )+b 3 ]/100
  • x 1 is the distance from any point in the first transition cladding layer 2 to the center of the germanium-doped core layer 1
  • a 3 and b 3 are both transition coefficients
  • the value range of a 3 is 0.26% ⁇ 0.30%
  • b 3 The value range is 0.54 ⁇ 0.58.
  • the refractive index of the second transition cladding layer 3 is n 3
  • the refractive index of the outer quartz cladding layer 8 is n 8
  • the relative refractive index difference between n 3 and n 8 is ⁇ n 3 ;
  • ⁇ n 3 [b 4 ⁇ (1-a 4 ⁇ x 2 2 )]/100
  • x 2 is the distance from any point in the second transition cladding layer 3 to the center of the germanium-doped core layer 1
  • a 4 and b 4 are both transition coefficients
  • the value range of a 4 is 2.8% to 3.2%
  • b 4 The value range is 0.45 ⁇ 0.55.
  • the refractive index of the fluorine-doped concave cladding layer 6 is n 6
  • the refractive index of the outer quartz cladding layer 8 is n 8
  • the relative refractive index difference between n 6 and n 8 is ⁇ n 6 ;
  • the value range of ⁇ n 6 is -0.12% ⁇ -0.21%.
  • the radius of the germanium-doped core layer 1 is 3.0 to 4.0 microns
  • the total thickness of the first transition cladding layer 2 and the second transition cladding layer 3 is 2.0 to 4.0 microns
  • the fluorine-doped concave The thickness of the cladding 6 is 9.0-20.0 microns
  • the radius of the outer quartz cladding 8 is 30-45 microns.
  • the diameter of the outer coating of the small-diameter single-mode optical fiber ranges from 100.0 to 125.0 microns.
  • the diameter of the outer coating of the small-diameter single-mode optical fiber ranges from 135.0 to 200.0 microns.
  • the thickness of the third transition cladding 7 can be determined according to the outer diameter of the small-diameter single-mode optical fiber, the radius of the germanium-doped core layer 1 , the first transition cladding 2 and The total thickness of the second transition cladding 3, the thickness of the fluorine-doped concave cladding 6 and the thickness of the outer quartz cladding 8 are determined. That is to say, the thickness of the third transition cladding 7 can be equal to 0.
  • the third transition cladding 7 is a vertical line segment.
  • the germanium-doped core layer 1 in Figure 2 can be doped with alkali metal elements or halogens to reduce its viscosity.
  • the alkali metal element is at least one of potassium and lithium
  • the halogen is chlorine element.
  • the viscosity matching between the germanium-doped core layer 1 and the fluorine-doped concave cladding layer 6 is achieved, and the internal stress is reduced, thereby reducing the attenuation of the optical fiber, thereby achieving a low-loss, small-diameter bend-insensitive single mode optical fiber.
  • the germanium-doped core layer 1 of Example 6 contains potassium and has an attenuation of 0.177dB/km at 1550nm. Its fusion loss with conventional G.652 optical fiber reaches 0.18dB, and its additional loss at a bending radius of 2.5mm is 0.18B.
  • the germanium-doped core layer 1 of Example 7 contains lithium and has an attenuation of 0.175dB/km at 1550nm. Its fusion loss with conventional G.652 optical fiber reaches 0.16dB, and its additional loss at a bending radius of 2.5mm is 0.19dB.
  • the germanium-doped core layer 1 of Example 8 contains chlorine and has an attenuation of 0.175dB/km at 1550nm. Its fusion loss with conventional G.652 optical fiber reaches 0.16dB, and its additional loss at a bending radius of 5mm is 0.18dB.
  • the germanium-doped core layer 1 of Example 9 contains potassium and has an attenuation of 0.156dB/km at 1550nm. Its fusion loss with conventional G.652 optical fiber reaches 0.09dB, and its additional loss at a bending radius of 5mm is 0.29dB.
  • the germanium-doped core layer 1 of Example 10 is not doped with other elements, and has an attenuation of 0.179 dB/km at 1550 nm. Its fusion loss with conventional G.652 optical fiber reaches 0.08 dB, and its additional loss at a bending radius of 5 mm is 0.42 dB.
  • the above five embodiments realize the waveguide structure design of a small-diameter single-mode optical fiber that has good compatibility with existing conventional single-mode optical fibers, can be well compatible with conventional G.652 optical fibers, and has low splicing loss.
  • the inner quartz cladding 4 and the fourth transition cladding 5 can be added. Specifically, see Figure 3.
  • the inner quartz cladding 4 and the fourth transition cladding 5 are The fourth transition cladding 5 is arranged in sequence from the inside to the outside in the radial direction.
  • the inner quartz cladding 4 and the fourth transition cladding 5 are located between the second transition cladding 3 and the fluorine-doped concave cladding 6; the fourth transition cladding
  • the refractive index of layer 5 is smaller than the refractive index of inner quartz cladding layer 4 and larger than the refractive index of fluorine-doped concave cladding layer 6 .
  • An inner quartz cladding layer 4 is provided between the germanium-doped core layer 1 and the fluorine-doped concave cladding layer 6 to form a stress transition, so that the fluorine-doped concave cladding layer 6 can achieve a lower relative refractive index difference and improve the bending resistance. sensitivity ability,
  • a double transition cladding layer is provided between the germanium-doped core layer 1 and the inner quartz cladding layer 4. They are a first transition cladding layer 2 whose relative refractive index difference decreases in a first polynomial linear shape and a second transition cladding layer whose relative refractive index difference decreases in a second polynomial shape.
  • the second transition cladding 3 with a linear descending term is used to smooth the internal stress and improve the micro-bending ability.
  • a fourth transition cladding 5 is provided between the inner quartz cladding 4 and the fluorine-doped concave cladding 6.
  • a third transition cladding 7 is provided between the fluorine-doped concave cladding 6 and the outer quartz cladding 8.
  • the refractive index of the first transition cladding layer 2 is n 2
  • the refractive index of the outer quartz cladding layer 8 is n 8
  • the relative refractive index difference between n 2 and n 8 is ⁇ n 2 ;
  • ⁇ n 2 [a 5 ⁇ (1-x 1 -x 1 2 )+b 5 ]/100
  • x 1 is the distance from any point in the first transition cladding layer 2 to the center of the germanium-doped core layer 1
  • a 5 and b 5 are both transition coefficients
  • the value range of a 5 is 0.15% to 0.30%
  • b 5 The value range is 0.35 ⁇ 0.45.
  • the refractive index of the second transition cladding 3 is n 3
  • the refractive index of the outer quartz cladding 8 is n 8
  • the relative refractive index difference between n 3 and n 8 is ⁇ n 3 ;
  • ⁇ n 3 [b 6 ⁇ (1-a 6 ⁇ x 2 2 )]/100
  • x 2 is the distance from any point in the second transition cladding layer 3 to the center of the germanium-doped core layer 1
  • a 6 and b 6 are both transition coefficients, and the value range of a 6 is 1.8% to 2.2%, and b 6 The value range is 0.6 ⁇ 0.8.
  • the refractive index of the fluorine-doped concave cladding layer 6 is n 6
  • the refractive index of the outer quartz cladding layer 8 is n 8
  • the relative refractive index difference between n 6 and n 8 is ⁇ n 6 ;
  • the value range of ⁇ n 6 is -0.22% ⁇ -0.46%.
  • the radius of the germanium-doped core layer 1 is 2.5 to 4.0 microns
  • the total thickness of the first transition cladding layer 2 , the second transition cladding layer 3 and the inner quartz cladding layer 4 is 3.0 to 8.0 microns. microns
  • the total thickness of the fourth transition cladding 5, the fluorine-doped concave cladding 6 and the third transition cladding 7 is 9.0 to 25.0 microns
  • the radius of the outer quartz cladding 8 is 30 to 62.5 microns.
  • the diameter of the outer coating of the small-diameter single-mode optical fiber ranges from 100.0 to 125.0 microns.
  • the diameter of the outer coating of the small-diameter single-mode optical fiber ranges from 135.0 to 200.0 microns.
  • the germanium-doped core layer 1 in Figure 3 can be doped with alkali metal elements or halogens to reduce its viscosity.
  • the alkali metal element is at least one of potassium and lithium
  • the halogen is chlorine element.
  • the viscosity of the germanium-doped core layer 1 and the inner quartz cladding 4 is matched, and the internal stress is reduced, thereby reducing the attenuation of the optical fiber, thereby realizing a low-loss, small-diameter, bend-insensitive single-mode optical fiber.
  • the total thickness of the fourth transition cladding layer 5 , the fluorine-doped concave cladding layer 6 and the third transition cladding layer 7 is usually calculated.
  • the third transition cladding layer 7 and the fourth transition cladding layer 5 have separate thicknesses. The thicknesses of the two can be equal to 0 independently.
  • the third transition cladding layer 7 and the fourth transition cladding layer 5 are each a vertical line segment.
  • the outer coating of the optical fiber includes an inner layer and an outer layer.
  • the Young's modulus of the inner layer is controlled between 0.1Mpa and 50Mpa, and the Young's modulus of the outer layer is controlled between 0.3Gpa and 1.0Gpa.
  • the germanium-doped core layer 1 of Example 11 is not doped with other elements, the attenuation at 1550nm is 0.179dB/km, and its additional loss at a bending radius of 2.5mm is 0.12B.
  • the germanium-doped core layer 1 of Example 12 contains lithium, has an attenuation of 0.179dB/km at 1550nm, and its additional loss at a bending radius of 2.5mm is 0.13dB.
  • the germanium-doped core layer 1 of Example 13 contains chlorine, the attenuation at 1550nm is 0.175dB/km, and its additional loss at a bending radius of 2.5mm is 0.11dB.
  • the germanium-doped core layer 1 of Example 14 contains lithium, the attenuation at 1550nm is 0.176dB/km, and its additional loss at a bending radius of 5mm is 0.12dB.
  • the germanium-doped core layer 1 of Example 15 contains potassium and has an attenuation of 0.159dB/km at 1550nm. Its fusion loss with conventional G.652 optical fiber reaches 0.08dB, and its additional loss at a bending radius of 5mm is 0.22dB.
  • the above five embodiments realize the waveguide structure design of a small-diameter single-mode optical fiber that has good compatibility with existing conventional single-mode optical fibers, can be well compatible with conventional G.652 optical fibers, and has low splicing loss.
  • it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, It can also be an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be an internal connection between two components.
  • a fixed connection a detachable connection, or an integral connection
  • it can be a mechanical connection
  • It can also be an electrical connection
  • it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be an internal connection between two components.

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Abstract

一种细径单模光纤，包括沿径向由内到外依次设置的掺锗芯层（1）、第一过渡包层（2）、第二过渡包层（3）和外石英包层（8）；第一过渡包层（2）的折射率小于掺锗芯层（1）的折射率，且大于第二过渡包层（3）的折射率；沿径向由内到外，第一过渡包层（2）的相对折射率差呈第一多项式线形下降，第二过渡包层（3）的相对折射率差呈第二多项式线形下降。在掺锗芯层（1）的周围设计了相对折射率差呈第一多项式线形下降的第一过渡包层（2）和相对折射率差呈第二多项式线形下降的第二过渡包层（3），从而形成双平滑过渡包层的波导结构，加强细径光纤抵抗外界的干扰能力，并实现掺锗芯层（1）与外石英包层（8）之间的平滑过渡，减少芯包间应力，降低光纤内部因应力造成的微裂纹，从而提升其长期可靠性。

Description

一种细径单模光纤 技术领域
本申请涉及光纤制造技术领域，特别涉及一种细径单模光纤。
背景技术
随着全球宽带网络、新一代移动通信、三网融合建设的加快，通信业务对网络带宽的要求越来越高，光纤通信作为速度最快、传输质量最好的通信方式而被广泛使用。在网络建设上，随着管道资源的紧张，用户对管道的空间利用率、施工效率和维护的便利性等提出了更高的要求，气吹微缆技术无疑是一种很好的选择。另外，信息化建设对ODN技术提出了需求，ODN技术为适应光纤网络和5G网络的建设，对占地空间的要求越来越高，往往需要在极小的配线盒内布置大量的设备，此时留给用于设备间高速、高带宽通信连接的光纤的空间将更为狭小。因此，无论是大芯数微缆技术还是蓬勃发展的ODN技术，均对细径单模光纤技术提出了重大需求。
光纤的直径越小、涂层越薄，进而导致光纤抗外界干扰能力下降，所以传统的仅依靠减小单模光纤外形尺寸的方法难以应用于对光纤性能要求较高的微缆和智能ODN技术。另外，细径单模光纤在应用环节，需要依托于现有切割、熔接设备，故光纤尺寸需要在满足性能提升的同时，满足现有切割、熔接等设备的要求。因此，如何发展出与常规通信光纤具有良好熔接性能，还具有更小体积，同时还具有优良的几何与光学性能的细径单模光纤成为光纤厂家谋求单模光纤细径化应用技术急需解决的难题。
发明内容
本申请实施例提供一种细径单模光纤，通过抛物线形下降和多项 式线形下降的两种波导结构来实现掺锗芯层与外石英包层之间的平滑过渡，减少芯包间应力，降低光纤内部因应力造成的微裂纹，从而提升其长期可靠性。
本申请实施例提供了一种细径单模光纤，其包括沿径向由内到外依次设置的掺锗芯层、第一过渡包层、第二过渡包层和外石英包层；
所述第一过渡包层的折射率小于掺锗芯层的折射率，且大于第二过渡包层的折射率；
沿径向由内到外，所述第一过渡包层的相对折射率差呈第一多项式线形下降，所述第二过渡包层的相对折射率差呈第二多项式线形下降。
一些实施例中，所述第一过渡包层折射率为n 2，所述外石英包层的折射率为n 8，n 2与n 8的相对折射率差为Δn 2；
Δn 2＝[a 1×(1-x 1-x 1 2)+b 1]/100
其中，x 1为所述第一过渡包层内任意一点到所述掺锗芯层的中心的距离，a 1和b 1均为过渡系数，且a 1取值范围为0.15％～0.3％，b 1取值范围为0.35～0.45。
一些实施例中，所述第二过渡包层折射率为n 3，所述外石英包层的折射率为n 8，n 3与n 8的相对折射率差为Δn 3；
Δn 3＝[b 2×(1-a 2×x 2 2)]/100
其中，x 2为所述第二过渡包层内任意一点到所述掺锗芯层的中心的距离，a 2和b 2均为过渡系数，且a 2取值范围为1.8％～2.2％，b 2取值范围为0.6～0.8。
一些实施例中，所述掺锗芯层的半径为3.0～5.0微米，所述第一过渡包层和第二过渡包层的合计厚度为2.0～4.0微米，所述外石英包层的半径为30～45微米。
一些实施例中，所述细径单模光纤还包括沿径向由内到外依次设置的掺氟下凹包层和第三过渡包层，所述掺氟下凹包层和第三过渡包 层位于第二过渡包层和外石英包层之间；
所述第三过渡包层的折射率小于外石英包层的折射率，且大于掺氟下凹包层的折射率。
一些实施例中，所述第一过渡包层折射率为n 2，所述外石英包层的折射率为n 8，n 2与n 8的相对折射率差为Δn 2；
Δn 2＝[a 3×(1-x 1-x 1 2-x 1 3)+b 3]/100
其中，x 1为所述第一过渡包层内任意一点到所述掺锗芯层的中心的距离，a 3和b 3均为过渡系数，且a 3取值范围为0.26％～0.30％，b 3取值范围为0.54～0.58。
一些实施例中，所述第二过渡包层折射率为n 3，所述外石英包层的折射率为n 8，n 3与n 8的相对折射率差为Δn 3；
Δn 3＝[b 4×(1-a 4×x 2 2)]/100
其中，x 2为所述第二过渡包层内任意一点到所述掺锗芯层的中心的距离，a 4和b 4均为过渡系数，且a 4取值范围为2.8％～3.2％，b 4取值范围为0.45～0.55。
一些实施例中，所述掺氟下凹包层折射率为n 6，所述外石英包层的折射率为n 8，n 6与n 8的相对折射率差为Δn 6；
Δn 6的取值范围为-0.12％～-0.21％。
一些实施例中，所述掺锗芯层的半径为3.0～4.0微米，所述第一过渡包层和第二过渡包层的合计厚度为2.0～4.0微米，所述掺氟下凹包层的厚度为9.0～20.0微米，所述外石英包层的半径为30～45微米。
一些实施例中，所述细径单模光纤还包括沿径向由内到外依次设置的内石英包层和第四过渡包层，所述内石英包层和第四过渡包层位于第二过渡包层和掺氟下凹包层之间；
所述第四过渡包层的折射率小于内石英包层的折射率，且大于掺氟下凹包层的折射率。
一些实施例中，所述第一过渡包层折射率为n 2，所述外石英包层 的折射率为n 8，n 2与n 8的相对折射率差为Δn 2；
Δn 2＝[a 5×(1-x 1-x 1 2)+b 5]/100
其中，x 1为所述第一过渡包层内任意一点到所述掺锗芯层的中心的距离，a 5和b 5均为过渡系数，且a 5取值范围为0.15％～0.30％，b 5取值范围为0.35～0.45。
一些实施例中，所述第二过渡包层折射率为n 3，所述外石英包层的折射率为n 8，n 3与n 8的相对折射率差为Δn 3；
Δn 3＝[b 6×(1-a 6×x 2 2)]/100
其中，x 2为所述第二过渡包层内任意一点到所述掺锗芯层的中心的距离，a 6和b 6均为过渡系数，且a 6取值范围为1.8％～2.2％，b 6取值范围为0.6～0.8。
一些实施例中，所述掺氟下凹包层折射率为n 6，所述外石英包层的折射率为n 8，n 6与n 8的相对折射率差为Δn 6；
Δn 6的取值范围为-0.22％～-0.46％。
一些实施例中，所述掺锗芯层的半径为2.5～4.0微米，所述第一过渡包层、第二过渡包层和内石英包层的合计厚度为3.0～8.0微米，所述第四过渡包层、掺氟下凹包层和第三过渡包层的合计厚度为9.0～25.0微米，所述外石英包层的半径为30～62.5微米。
一些实施例中，所述外石英包层中掺杂有用于降低其粘度的碱金属元素或者卤素。
一些实施例中，所述掺锗芯层中掺杂有用于降低其粘度的碱金属元素或者卤素。
一些实施例中，所述碱金属元素为钾、锂中的至少一种，所述卤素为氯元素。
本申请提供的技术方案带来的有益效果包括：
本申请实施例提供的细径单模光纤，在掺锗芯层的周围设计了双过渡包层，分别为相对折射率差呈第一多项式线形下降的第一过渡包 层和相对折射率差呈第二多项式线形下降的第二过渡包层，以形成双平滑过渡包层的波导结构，优化光纤变细后，涂层和外石英包层厚度减薄带来的宏弯损耗和微弯损耗增加问题，使细径单模光纤在面临现有常规光纤同等外界干扰条件下，仍具备优良的衰减性能；同时针对光纤变细后长期使用的可靠性问题，通过第一多项式线形下降和第二多项式线形下降的两种结构来实现掺锗芯层与外石英包层之间的平滑过渡，减少芯包间应力，降低光纤内部因应力造成的微裂纹，从而提升其长期可靠性。
本申请通过两个过渡包层和第一多项式线形下降和第二多项式线形下降的两种结构，减少了细径单模光纤与现有常规单模光纤熔融时细径单模光纤侧漏光严重的问题。由于细径单模光纤相比现有常规单模光纤要细30％～50％以上，熔接点处温度对细径单模光纤的影响相比常规单模光纤更大，其掺锗芯层掺杂成分更易扩散，从而使其约束光低损耗传播的能力降低，使部分光因掺锗芯层掺杂扩散带来的NA降低而发生泄漏。本申请的结构，由于采用了双多项式下降，热量从外石英包层传递进掺锗芯层带来的扩散影响被很好的削弱，从而实现了与现有常规单模光纤具有良好兼容特性，可以与常规G.652光纤良好兼容，对接的熔接损耗低。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本申请一个实施例提供的细径单模光纤波导结构示意图；
图2为本申请另一个实施例提供的细径单模光纤波导结构示意图；
图3为本申请再一个实施例提供的细径单模光纤波导结构示意 图。
图中：1、掺锗芯层；2、第一过渡包层；3、第二过渡包层；4、内石英包层；5、第四过渡包层；6、掺氟下凹包层；7、第三过渡包层；8、外石英包层。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请的一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动的前提下所获得的所有其他实施例，都属于本申请保护的范围。
参见图1所示，本申请一个优选的实施方式提供了一种细径单模光纤，其包括沿径向由内到外依次设置的掺锗芯层1、第一过渡包层2、第二过渡包层3和外石英包层8；第一过渡包层2的折射率小于掺锗芯层1的折射率，且大于第二过渡包层3的折射率；沿径向由内到外，第一过渡包层2的相对折射率差呈第一多项式线形下降，第二过渡包层3的相对折射率差呈第二多项式线形下降，第一多项式线形和第二多项式线形相连接处平滑过渡，以使得第一过渡包层2、第二过渡包层3作为整体，相对折射率差的波导结构平滑过渡。
上述第一过渡包层2的相对折射率差呈第一多项式线形下降，以及第二过渡包层3的相对折射率差呈第二多项式线形下降，指的是，沿径向由内到外，相对折射率差逐渐减小，且相对折射率差满足多项式函数。显然，第一多项式线形对应的第一多项式函数与第二多项式对应的第二多项式函数不相同。
本申请实施例提供的细径单模光纤，在掺锗芯层1的周围设计了双过渡包层，分别为相对折射率差呈第一多项式线形下降的第一过渡包层2和相对折射率差呈第二多项式线形下降的第二过渡包层3，从 而形成双平滑过渡包层的波导结构，从减少宏弯损耗和微弯损耗两个方面来加强细径光纤抵抗外界的干扰能力，并通过第一多项式线形下降和第二多项式线形下降的两种结构来实现掺锗芯层1与外石英包层8之间的平滑过渡，减少芯包间应力，降低光纤内部因应力造成的微裂纹，从而提升其长期可靠性。
本申请采用如下公式计算相对折射率差Δn i：
Δn i＝(n i-n 8)/(n i+n 8)*100％
其中n 8为外石英包层8的折射率，对本申请而言，当计算第一过渡包层2与外石英包层8的相对折射率差Δn 2时，公式中n i为第一过渡包层2的折射率n 2；当计算第二过渡包层3与外石英包层8的相对折射率差Δn 3时，公式中n i为第二过渡包层3的折射率n 3；其他各层以此类推。
结合图1所示，上述实施方式中，第一过渡包层2折射率为n 2，外石英包层8的折射率为n 8，n 2与n 8的相对折射率差为Δn 2；
Δn 2＝[a 1×(1-x 1-x 1 2)+b 1]/100
其中，x 1为第一过渡包层2内任意一点到掺锗芯层1的中心的距离，a 1和b 1均为过渡系数，且a 1取值范围为0.15％～0.3％，b 1取值范围为0.35～0.45。
结合图1所示，上述实施方式中，第二过渡包层3折射率为n 3，外石英包层8的折射率为n 8，n 3与n 8的相对折射率差为Δn 3；
Δn 3＝[b 2×(1-a 2×x 2 2)]/100
其中，x 2为第二过渡包层3内任意一点到掺锗芯层1的中心的距离，a 2和b 2均为过渡系数，且a 2取值范围为1.8％～2.2％，b 2取值范围为0.6～0.8。
结合图1所示，上述实施方式中，掺锗芯层1的半径为3.0～5.0微米，第一过渡包层2和第二过渡包层3的合计厚度为2.0～4.0微米，外石英包层8的半径为30～45微米。
结合图1所示，当外石英包层8的半径为30微米时，细径单模光纤的外涂层直径范围为100.0～125.0微米。
当外石英包层8的半径为40微米时，细径单模光纤的外涂层直径范围为135.0～200.0微米。
上述实施方式中，为了进一步优化光纤的衰减性能，可以在图1中的外石英包层8中掺杂有用于降低其粘度的碱金属元素或者卤素。比如，碱金属元素为钾、锂中的至少一种，卤素为氯元素。通过降低外石英包层8的粘度，实现掺锗芯层1与外石英包层8的粘度匹配，降低内应力，从而降低光纤的衰减，从而实现超低损耗的细径单模光纤。
结合图1，以下通过5个具体实施例详细阐述。
表1按图1所示波导结构时的实施例
Figure PCTCN2022127613-appb-000001
实施例1的外石英包层8含有钾，1550nm衰减为0.171dB/km， 其与常规G.652光纤的熔接损耗达到0.18dB，其在5mm弯曲半径下的附加损耗为0.21dB。
实施例2的外石英包层8含有锂，1550nm衰减为0.175dB/km，其与常规G.652光纤的熔接损耗达到0.16dB，其在5mm弯曲半径下的附加损耗为0.19dB。
实施例3的外石英包层8含有氯，1550nm衰减为0.157dB/km，其与常规G.652光纤的熔接损耗达到0.10dB，其在5mm弯曲半径下的附加损耗为0.35dB；
实施例4的外石英包层8含有钾，1550nm衰减为0.158dB/km，其与常规G.652光纤的熔接损耗达到0.09dB，其在5mm弯曲半径下的附加损耗为0.29dB。
实施例5的外石英包层8未掺入其他元素，1550nm衰减为0.179dB/km，其与常规G.652光纤的熔接损耗达到0.08dB，其在5mm弯曲半径下的附加损耗为0.46dB。
可见，上述5个实施例实现了与现有常规单模光纤具有良好兼容特性的细径单模光纤的波导结构设计，可以与常规G.652光纤良好兼容，对接的熔接损耗低。
当需要有一定的弯曲不敏感能力时，可以在掺锗芯层1周围增加掺氟下凹包层6，具体地，参见图2所示，在另一个优选的实施方式中，细径单模光纤还包括沿径向由内到外依次设置的掺氟下凹包层6和第三过渡包层7，掺氟下凹包层6和第三过渡包层7位于第二过渡包层3和外石英包层8之间；第三过渡包层7的折射率小于外石英包层8的折射率，且大于掺氟下凹包层6的折射率。在掺氟下凹包层6与外石英包层8之间设置有第三过渡包层7，减少芯包间应力。
结合图2所示，上述实施方式中，第一过渡包层2折射率为n 2，外石英包层8的折射率为n 8，n 2与n 8的相对折射率差为Δn 2；
Δn 2＝[a 3×(1-x 1-x 1 2-x 1 3)+b 3]/100
其中，x 1为第一过渡包层2内任意一点到掺锗芯层1的中心的距离，a 3和b 3均为过渡系数，且a 3取值范围为0.26％～0.30％，b 3取值范围为0.54～0.58。
结合图2所示，上述实施方式中，第二过渡包层3折射率为n 3，外石英包层8的折射率为n 8，n 3与n 8的相对折射率差为Δn 3；
Δn 3＝[b 4×(1-a 4×x 2 2)]/100
其中，x 2为第二过渡包层3内任意一点到掺锗芯层1的中心的距离，a 4和b 4均为过渡系数，且a 4取值范围为2.8％～3.2％，b 4取值范围为0.45～0.55。
结合图2所示，上述实施方式中，掺氟下凹包层6折射率为n 6，外石英包层8的折射率为n 8，n 6与n 8的相对折射率差为Δn 6；Δn 6的取值范围为-0.12％～-0.21％。
结合图2所示，上述实施方式中，掺锗芯层1的半径为3.0～4.0微米，第一过渡包层2和第二过渡包层3的合计厚度为2.0～4.0微米，掺氟下凹包层6的厚度为9.0～20.0微米，外石英包层8的半径为30～45微米。
结合图2所示，当外石英包层8的半径为30微米时，细径单模光纤的外涂层直径范围为100.0～125.0微米。
当外石英包层8的半径为50微米时，细径单模光纤的外涂层直径范围为135.0～200.0微米。
需要说明的是，结合图2所示，上述实施方式中，第三过渡包层7的厚度可以根据细径单模光纤外径，以及掺锗芯层1的半径、第一过渡包层2和第二过渡包层3的合计厚度、掺氟下凹包层6的厚度以及外石英包层8的厚度确定，也就是说，第三过渡包层7的厚度可以等于0，此时，在波导结构图中，第三过渡包层7为一段竖直的线段。
上述实施方式中，为了进一步优化光纤的衰减性能，可以在图2 掺锗芯层1中掺杂用于降低其粘度的碱金属元素或者卤素。比如，碱金属元素为钾、锂中的至少一种，卤素为氯元素。
通过降低掺锗芯层1的粘度，实现掺锗芯层1和掺氟下凹包层6的粘度匹配，降低内应力，从而降低光纤的衰减，从而实现低损耗的细径弯曲不敏感单模光纤。
结合图2，以下通过5个具体实施例详细阐述。
表2按图2所示波导结构时的实施例
Figure PCTCN2022127613-appb-000002
实施例6的掺锗芯层1含有钾，1550nm衰减为0.177dB/km，其与常规G.652光纤的熔接损耗达到0.18dB，其在2.5mm弯曲半径下的附加损耗为0.18B。
实施例7的掺锗芯层1含有锂，1550nm衰减为0.175dB/km，其与常规G.652光纤的熔接损耗达到0.16dB，其在2.5mm弯曲半径下的附加损耗为0.19dB。
实施例8的掺锗芯层1含有氯，1550nm衰减为0.175dB/km，其与常规G.652光纤的熔接损耗达到0.16dB，其在5mm弯曲半径下的附加损耗为0.18dB。
实施例9的掺锗芯层1含有钾，1550nm衰减为0.156dB/km，其与常规G.652光纤的熔接损耗达到0.09dB，其在5mm弯曲半径下的附加损耗为0.29dB。
实施例10的掺锗芯层1未掺入其他元素，1550nm衰减为0.179dB/km，其与常规G.652光纤的熔接损耗达到0.08dB，其在5mm弯曲半径下的附加损耗为0.42dB。
可见，上述5个实施例实现了与现有常规单模光纤具有良好兼容特性的细径单模光纤的波导结构设计，可以与常规G.652光纤良好兼容，对接的熔接损耗低。
当需要更好的弯曲不敏感能力时，可以增加内石英包层4和第四过渡包层5，具体地，参见图3所示，在另一个优选的实施方式中，内石英包层4和第四过渡包层5沿径向由内到外依次设置，内石英包层4和第四过渡包层5位于第二过渡包层3和掺氟下凹包层6之间；第四过渡包层5的折射率小于内石英包层4的折射率，且大于掺氟下凹包层6的折射率。
在掺锗芯层1和掺氟下凹包层6之间设置内石英包层4，形成应力过渡，从而可让掺氟下凹包层6可以实现更低的相对折射率差，提升弯曲不敏感能力，
在掺锗芯层1和内石英包层4之间设置双过渡包层，分别为相对折射率差呈第一多项式线形下降的第一过渡包层2和相对折射率差 呈第二多项式线形下降的第二过渡包层3，来实现内应力的平滑以及微弯能力的提升，在内石英包层4与掺氟下凹包层6之间设置有第四过渡包层5，在掺氟下凹包层6与外石英包层8之间设置有第三过渡包层7，通过系列下凹包层和过渡包层，既实现高的弯曲不敏感能力，又能优化内部缺陷和应力，实现低衰减和高可靠。
结合图3所示，上述实施方式中，第一过渡包层2折射率为n 2，外石英包层8的折射率为n 8，n 2与n 8的相对折射率差为Δn 2；
Δn 2＝[a 5×(1-x 1-x 1 2)+b 5]/100
其中，x 1为第一过渡包层2内任意一点到掺锗芯层1的中心的距离，a 5和b 5均为过渡系数，且a 5取值范围为0.15％～0.30％，b 5取值范围为0.35～0.45。
结合图3所示，上述实施方式中，第二过渡包层3折射率为n 3，外石英包层8的折射率为n 8，n 3与n 8的相对折射率差为Δn 3；
Δn 3＝[b 6×(1-a 6×x 2 2)]/100
其中，x 2为第二过渡包层3内任意一点到掺锗芯层1的中心的距离，a 6和b 6均为过渡系数，且a 6取值范围为1.8％～2.2％，b 6取值范围为0.6～0.8。
结合图3所示，上述实施方式中，掺氟下凹包层6折射率为n 6，外石英包层8的折射率为n 8，n 6与n 8的相对折射率差为Δn 6；Δn 6的取值范围为-0.22％～-0.46％。
结合图3所示，上述实施方式中，掺锗芯层1的半径为2.5～4.0微米，第一过渡包层2、第二过渡包层3和内石英包层4的合计厚度为3.0～8.0微米，第四过渡包层5、掺氟下凹包层6和第三过渡包层7的合计厚度为9.0～25.0微米，外石英包层8的半径为30～62.5微米。
结合图3所示，当外石英包层8的半径为30微米时，细径单模光纤的外涂层直径范围为100.0～125.0微米。
当外石英包层8的半径为62.5微米时，细径单模光纤的外涂层直径范围为135.0～200.0微米。
上述实施方式中，为了进一步优化光纤的衰减性能，可以在图3掺锗芯层1中掺杂用于降低其粘度的碱金属元素或者卤素。比如，碱金属元素为钾、锂中的至少一种，卤素为氯元素。
通过降低掺锗芯层1的粘度，实现掺锗芯层1和内石英包层4的粘度匹配，降低内应力，从而降低光纤的衰减，从而实现低损耗的细径弯曲不敏感单模光纤。
需要说明的是，结合图3所示，上述实施方式中，通常计算第四过渡包层5、掺氟下凹包层6和第三过渡包层7的合计厚度，对于第三过渡包层7和第四过渡包层5单独的厚度，二者厚度可以单独等于0，此时，在波导结构图中，第三过渡包层7和第四过渡包层5各自均为一段竖直的线段。
上述实施方式中，光纤的外涂层包括内层和外层，内层的杨氏模量控制在0.1Mpa～50Mpa，外层的杨氏模量控制在0.3Gpa～1.0Gpa。
结合图3，以下通过5个具体实施例详细阐述。
表3按图3所示波导结构时的实施例
Figure PCTCN2022127613-appb-000003
Figure PCTCN2022127613-appb-000004
实施例11的掺锗芯层1未掺入其他元素，1550nm衰减为0.179dB/km，其在2.5mm弯曲半径下的附加损耗为0.12B。
实施例12的掺锗芯层1含有锂，1550nm衰减为0.179dB/km，其在2.5mm弯曲半径下的附加损耗为0.13dB。
实施例13的掺锗芯层1含有氯，1550nm衰减为0.175dB/km，其在2.5mm弯曲半径下的附加损耗为0.11dB。
实施例14的掺锗芯层1含有锂，1550nm衰减为0.176dB/km，其在5mm弯曲半径下的附加损耗为0.12dB。
实施例15的掺锗芯层1含有钾，1550nm衰减为0.159dB/km，其与常规G.652光纤的熔接损耗达到0.08dB，其在5mm弯曲半径下的附加损耗为0.22dB。
可见，上述5个实施例实现了与现有常规单模光纤具有良好兼容特性的细径单模光纤的波导结构设计，可以与常规G.652光纤良好兼容，对接的熔接损耗低。
在本申请的描述中，需要说明的是，术语“上”、“下”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述 本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
需要说明的是，在本申请中，诸如“第一”和“第二”等之类的关系术语仅仅用来将一个实体或者操作与另一个实体或操作区分开来，而不一定要求或者暗示这些实体或操作之间存在任何这种实际的关系或者顺序。而且，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法、物品或者设备不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法、物品或者设备所固有的要素。在没有更多限制的情况下，由语句“包括一个……”限定的要素，并不排除在包括所述要素的过程、方法、物品或者设备中还存在另外的相同要素。
以上所述仅是本申请的具体实施方式，使本领域技术人员能够理解或实现本申请。对这些实施例的多种修改对本领域的技术人员来说将是显而易见的，本文中所定义的一般原理可以在不脱离本申请的精神或范围的情况下，在其它实施例中实现。因此，本申请将不会被限制于本文所示的这些实施例，而是要符合与本文所申请的原理和新颖特点相一致的最宽的范围。

Claims (17)

  1. 一种细径单模光纤，其特征在于，其包括沿径向由内到外依次设置的掺锗芯层(1)、第一过渡包层(2)、第二过渡包层(3)和外石英包层(8)；
    所述第一过渡包层(2)的折射率小于掺锗芯层(1)的折射率，且大于第二过渡包层(3)的折射率；
    沿径向由内到外，所述第一过渡包层(2)的相对折射率差呈第一多项式线形下降，所述第二过渡包层(3)的相对折射率差呈第二多项式线形下降。
  2. 如权利要求1所述的细径单模光纤，其特征在于：
    所述第一过渡包层(2)折射率为n 2，所述外石英包层(8)的折射率为n 8，n 2与n 8的相对折射率差为Δn 2；
    Δn 2＝[a 1×(1-x 1-x 1 2)+b 1]/100
    其中，x 1为所述第一过渡包层(2)内任意一点到所述掺锗芯层(1)的中心的距离，a 1和b 1均为过渡系数，且a 1取值范围为0.15％～0.3％，b 1取值范围为0.35～0.45。
  3. 如权利要求1所述的细径单模光纤，其特征在于：
    所述第二过渡包层(3)折射率为n 3，所述外石英包层(8)的折射率为n 8，n 3与n 8的相对折射率差为Δn 3；
    Δn 3＝[b 2×(1-a 2×x 2 2)]/100
    其中，x 2为所述第二过渡包层(3)内任意一点到所述掺锗芯层(1)的中心的距离，a 2和b 2均为过渡系数，且a 2取值范围为1.8％～2.2％，b 2取值范围为0.6～0.8。
  4. 如权利要求1所述的细径单模光纤，其特征在于：
    所述掺锗芯层(1)的半径为3.0～5.0微米，所述第一过渡包层(2)和第二过渡包层(3)的合计厚度为2.0～4.0微米，所述外石英包层(8)的半径为30～45微米。
  5. 如权利要求1所述的细径单模光纤，其特征在于：
    所述细径单模光纤还包括沿径向由内到外依次设置的掺氟下凹包层(6)和第三过渡包层(7)，所述掺氟下凹包层(6)和第三过渡包层(7)位于第二过渡包层(3)和外石英包层(8)之间；
    所述第三过渡包层(7)的折射率小于外石英包层(8)的折射率，且大于掺氟下凹包层(6)的折射率。
  6. 如权利要求5所述的细径单模光纤，其特征在于：
    所述第一过渡包层(2)折射率为n 2，所述外石英包层(8)的折射率为n 8，n 2与n 8的相对折射率差为Δn 2；
    Δn 2＝[a 3×(1-x 1-x 1 2-x 1 3)+b 3]/100
    其中，x 1为所述第一过渡包层(2)内任意一点到所述掺锗芯层(1)的中心的距离，a 3和b 3均为过渡系数，且a 3取值范围为0.26％～0.30％，b 3取值范围为0.54～0.58。
  7. 如权利要求5所述的细径单模光纤，其特征在于：
    所述第二过渡包层(3)折射率为n 3，所述外石英包层(8)的折射率为n 8，n 3与n 8的相对折射率差为Δn 3；
    Δn 3＝[b 4×(1-a 4×x 2 2)]/100
    其中，x 2为所述第二过渡包层(3)内任意一点到所述掺锗芯层(1)的中心的距离，a 4和b 4均为过渡系数，且a 4取值范围为2.8％～3.2％，b 4取值范围为0.45～0.55。
  8. 如权利要求5所述的细径单模光纤，其特征在于：
    所述掺氟下凹包层(6)折射率为n 6，所述外石英包层(8)的折射率为n 8，n 6与n 8的相对折射率差为Δn 6；
    Δn 6的取值范围为-0.12％～-0.21％。
  9. 如权利要求5所述的细径单模光纤，其特征在于：
    所述掺锗芯层(1)的半径为3.0～4.0微米，所述第一过渡包层(2)和第二过渡包层(3)的合计厚度为2.0～4.0微米，所述掺氟下 凹包层(6)的厚度为9.0～20.0微米，所述外石英包层(8)的半径为30～45微米。
  10. 如权利要求5所述的细径单模光纤，其特征在于：
    所述细径单模光纤还包括沿径向由内到外依次设置的内石英包层(4)和第四过渡包层(5)，所述内石英包层(4)和第四过渡包层(5)位于第二过渡包层(3)和掺氟下凹包层(6)之间；
    所述第四过渡包层(5)的折射率小于内石英包层(4)的折射率，且大于掺氟下凹包层(6)的折射率。
  11. 如权利要求10所述的细径单模光纤，其特征在于：
    所述第一过渡包层(2)折射率为n 2，所述外石英包层(8)的折射率为n 8，n 2与n 8的相对折射率差为Δn 2；
    Δn 2＝[a 5×(1-x 1-x 1 2)+b 5]/100
    其中，x 1为所述第一过渡包层(2)内任意一点到所述掺锗芯层(1)的中心的距离，a 5和b 5均为过渡系数，且a 5取值范围为0.15％～0.30％，b 5取值范围为0.35～0.45。
  12. 如权利要求10所述的细径单模光纤，其特征在于：
    所述第二过渡包层(3)折射率为n 3，所述外石英包层(8)的折射率为n 8，n 3与n 8的相对折射率差为Δn 3；
    Δn 3＝[b 6×(1-a 6×x 2 2)]/100
    其中，x 2为所述第二过渡包层(3)内任意一点到所述掺锗芯层(1)的中心的距离，a 6和b 6均为过渡系数，且a 6取值范围为1.8％～2.2％，b 6取值范围为0.6～0.8。
  13. 如权利要求10所述的细径单模光纤，其特征在于：
    所述掺氟下凹包层(6)折射率为n 6，所述外石英包层(8)的折射率为n 8，n 6与n 8的相对折射率差为Δn 6；
    Δn 6的取值范围为-0.22％～-0.46％。
  14. 如权利要求10所述的细径单模光纤，其特征在于：
    所述掺锗芯层(1)的半径为2.5～4.0微米，所述第一过渡包层(2)、第二过渡包层(3)和内石英包层(4)的合计厚度为3.0～8.0微米，所述第四过渡包层(5)、掺氟下凹包层(6)和第三过渡包层(7)的合计厚度为9.0～25.0微米，所述外石英包层(8)的半径为30～62.5微米。
  15. 如权利要求1所述的细径单模光纤，其特征在于：
    所述外石英包层(8)中掺杂有用于降低其粘度的碱金属元素或者卤素。
  16. 如权利要求5或10所述的细径单模光纤，其特征在于：
    所述掺锗芯层(1)中掺杂有用于降低其粘度的碱金属元素或者卤素。
  17. 如权利要求1或16所述的细径单模光纤，其特征在于：
    所述碱金属元素为钾、锂中的至少一种，所述卤素为氯元素。
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