WO2015109861A1 - 一种具有兼容性的小弯曲半径单模光纤 - Google Patents

一种具有兼容性的小弯曲半径单模光纤 Download PDF

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WO2015109861A1
WO2015109861A1 PCT/CN2014/087158 CN2014087158W WO2015109861A1 WO 2015109861 A1 WO2015109861 A1 WO 2015109861A1 CN 2014087158 W CN2014087158 W CN 2014087158W WO 2015109861 A1 WO2015109861 A1 WO 2015109861A1
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layer
refractive index
transition
cladding
relative refractive
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PCT/CN2014/087158
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English (en)
French (fr)
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罗文勇
李诗愈
陈伟
莫琦
柯一礼
胡福明
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烽火通信科技股份有限公司
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Priority to EP14879549.5A priority Critical patent/EP3098631B1/en
Priority to ES14879549T priority patent/ES2718879T3/es
Priority to KR1020167019158A priority patent/KR101835249B1/ko
Priority to CA2928115A priority patent/CA2928115C/en
Publication of WO2015109861A1 publication Critical patent/WO2015109861A1/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
    • G02B6/03638—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 3 layers only
    • G02B6/0365—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 3 layers only arranged - - +
    • 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
    • G02B6/03605—Highest refractive index not on central axis
    • G02B6/03611—Highest index adjacent to central axis region, e.g. annular core, coaxial ring, centreline depression affecting waveguiding
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/02—Pure silica glass, e.g. pure fused quartz
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
    • C03B2201/12—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with fluorine
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
    • C03B2201/31—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with germanium
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/10—Internal structure or shape details
    • C03B2203/22—Radial profile of refractive index, composition or softening point
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/10—Internal structure or shape details
    • C03B2203/22—Radial profile of refractive index, composition or softening point
    • C03B2203/23—Double or multiple optical cladding profiles

Definitions

  • the invention relates to the field of single mode fiber, in particular to a small curved radius single mode fiber with compatibility.
  • the improvement of the bending resistance of the optical fiber not only ensures the high quality of the optical signal transmission, but also reduces the overall heat generation of the communication system in which it is located, and improves the overall performance of the system.
  • the advanced optical fiber companies in the world have carried out in-depth research on the demand for super-bending fiber-optic technology for the hot-spot technology ODN technology of communication networks.
  • China's fiber optic cable companies are currently focusing on the technical study of small bend radius single-mode fibers such as G.657B2/3 with a bend radius of 10 mm or less as required by ITUT-G.657.
  • the ODN technology adapts to the requirements of the space occupied by the construction of the optical fiber network and the 3G network, it is often necessary to arrange a large amount of equipment in a very small wiring box.
  • the space of the high-speed, high-bandwidth communication fiber between the devices will be narrower, and the bending performance of the fiber is more and more demanding.
  • More and more applications require a strong bending single with a bending radius of less than 3 mm or even 2 mm. Mode fiber.
  • this super-flexible single mode also needs good compatibility with ordinary single-mode fiber, and the single-point splice loss between the two needs to be controlled within an acceptable small range.
  • the fiber selected in the fiber-to-the-home segment is inferior in compatibility, even if it has good bending performance,
  • due to the large loss when it is welded with the conventional G.652 fiber it will cause a large loss of the optical signal when the two are docked, thereby additionally requiring a larger optical gain, or the G.652 fiber is still used at the household end. Therefore, although there are currently anti-bending fibers, their compatibility with conventional G.652 fibers is poor, and it cannot meet the large-scale adoption of the fiber-to-the-home market.
  • the object of the present invention is to provide a small curved radius single-mode optical fiber with compatibility, which can achieve superior bending resistance with a bending radius of less than 2 mm, and can realize the same as conventional single-mode optical fiber. Very compatible.
  • the technical solution adopted by the present invention is: a small curved radius single mode fiber with compatibility, including a concentrically disposed core layer, an erbium doped layer, and a first concentric arrangement from the inside to the outside.
  • the relative refractive index difference of the core layer grading layer is ⁇ n1, Realization, where x 1 is the distance from any point in the core layer to the axis thereof; a 1 is the gradient coefficient of the core layer, b 1 is the gradient stability coefficient of the core layer, and a 1 is in the range of 0.5 % ⁇ 2%, b 1 ranges from 0 to 0.2%; the relative refractive index difference of the first transition layer is ⁇ n3, Realized, wherein x 3 is the distance between the concentric circle centered on the center of the fiber and the outer edge of the erbium-doped core layer 2 at any point
  • the relative refractive index difference of the second transition layer is ⁇ n5.
  • x 5 is the distance between a concentric circle centered at the center of the fiber and a outer edge of the first cladding 4 at any point in the second transition layer 5, a 5 , b 5 are transition coefficients, a 5 The value ranges from -1.0% to -0.3%, and the value of b 5 ranges from 0 to 0.1%;
  • the relative refractive index difference of the third transition layer is ⁇ n7, Realization, wherein x 7 is the distance between a concentric circle centered on the center of the fiber and a outer edge of the second cladding 6 at any point in the third transition layer 7, a 7 and b 7 are transition coefficients, a 7 The value ranges from 0.1% to 0.4%, and b 7 ranges from -1.3% to -0.3%.
  • the ratio of the thickness of the erbium-doped core layer to the thickness of the first cladding layer ranges from 0.5 to 2.0.
  • the ratio of the thickness of the erbium-doped core layer to the thickness of the second cladding layer ranges between 0.2 and 1.0.
  • the relative refractive index difference of the erbium-doped core layer ranges from 0.2% to 0.8%.
  • the relative refractive index difference of the first cladding layer ranges from 0 to 0.1%.
  • the relative refractive index difference of the second cladding layer ranges from -1.3% to -0.3%.
  • the third cladding has a diameter of 80 ⁇ m or 125 ⁇ m, which is a quartz cladding.
  • the small bending radius single mode fiber attenuation is below 0.2 dB/km, and when the bending radius is 2 mm, the additional loss is below 0.35 dB.
  • the outer layer of the tragic core layer is provided with a plurality of cladding layers, a first cladding layer with a low erbium-doped content, a second cladding layer with a deep fluorine-doped content, and a third cladding layer composed of a quartz cladding layer, thereby forming
  • a mountain-shaped waveguide structure enhances the bending resistance of the optical fiber from two aspects of reducing macrobend loss and microbending loss.
  • a transition layer is established between the erbium-doped core layer and the first cladding layer, the first cladding layer and the second cladding layer, and the second cladding layer and the third cladding layer, and a core layer is used in the erbium-doped core layer.
  • the small bending radius single mode fiber can be controlled to a small extent when welded to a conventional G.652 single mode fiber, which is compatible with conventional single mode fiber. Characteristics, which lays the foundation for fiber-to-the-home and ODN technology.
  • FIG. 1 is a schematic view showing the end face structure of a small curved radius single mode fiber with compatibility according to the present invention
  • FIG. 2 is a schematic view showing a structure of a small curved radius single mode fiber waveguide with compatibility according to the present invention
  • FIG. 3 is a schematic diagram of mode field control of a single mode fiber with small bend radius with compatibility
  • FIG. 4 is an additional bending loss of the optical fiber when the cladding diameter of FIG. 1 is 125 ⁇ m;
  • Fig. 5 is a graph showing the additional bending loss of the optical fiber when the cladding diameter of Fig. 1 is 80 ⁇ m.
  • the present invention has a compatible small bend radius single mode fiber, including a core layer grading layer 1, an erbium doped core layer 2, a first transition layer 3, and a first cladding layer 4 disposed concentrically from the inside to the outside. a second transition layer 5, a second cladding layer 6, a third transition layer 7, and a third cladding layer 8.
  • the core gradient layer 1 is inside the erbium-doped core layer 2, the first transition layer 2 is located between the erbium-doped core layer 1 and the first cladding layer 4, and the second transition layer 5 is located in the first cladding layer 4 and Between the second cladding layers 6, the third transition layer 7 is located between the second cladding layer 6 and the third cladding layer 8.
  • the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the first cladding layer 4 ranges from 0.5 to 2.0.
  • the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L6 of the second cladding layer 6 ranges from 0.2 to 1.0.
  • the third cladding layer 8 is a quartz cladding layer having a diameter D8 of 80 ⁇ m or 125 ⁇ m.
  • the small bending radius single-mode optical fiber of the present invention has a diameter of 200 ⁇ m or 245 ⁇ m.
  • the refractive index of the core layer is 1 n
  • the refractive index of the erbium-doped core layer 2 is n2
  • the refractive index of the first transition layer 3 is n3
  • the refractive index of the first cladding layer 4 is N4
  • the third transition layer 5 has a refractive index of n5
  • the second cladding layer 6 has a refractive index of n6
  • the third transition layer 7 has a refractive index of n7
  • the third cladding layer 8 has a refractive index of n8
  • the refractive index n8 of layer 8 is the refractive index n of the equivalent quartz cladding.
  • a relative refractive index difference is used, and a relative refractive index difference between each waveguide layer and the quartz cladding layer is determined based on the refractive index n of the quartz cladding layer, which is measured and realized as a standard.
  • the relative refractive index difference is given by the formula:
  • n is the refractive index of the quartz cladding layer, that is, the present invention corresponds to the refractive index n8 of the third cladding layer 8, and n' is the refractive index of the corresponding layer compared thereto.
  • n' when calculating the difference between the refractive index of the core graded layer 1 and the relative refractive index of the quartz cladding layer, n' takes the core refractive index n1 in the formula; when calculating the refractive index of the erbium-doped core layer and the stone When the relative refractive index difference of the British cladding layer is different, the n' value of the core refractive index n2 in the formula; when calculating the relative refractive index difference between the core layer of the first transition layer 3 and the quartz cladding layer, the first transition of n' value in the formula Layer refractive index n3; when calculating the relative refractive index difference between the first cladding layer 4 and the quartz cladding layer, where n' takes the first cladding refractive index n4; when calculating the relative relationship between the second transition layer 5 and the quartz cladding layer In the case of the refractive index difference, n' takes the value of the second transition layer refractive index
  • the relative refractive index difference ⁇ n1 of the core layered layer 1 can be obtained by the formula (1), the relative refractive index difference of the erbium-doped core layer 2 is ⁇ n2, and the relative refractive index difference of the first transition layer 3 is ⁇ n3, the first package.
  • the relative refractive index difference of the layer 4 is ⁇ n4
  • the relative refractive index difference of the second transition layer 5 is ⁇ n5
  • the relative refractive index difference of the second cladding layer 6 is ⁇ n6
  • the relative refractive index difference of the third transition layer 7 is ⁇ n7.
  • the relative refractive index difference of the erbium-doped core layer 2 ranges from 0.2% to 0.8%; the relative refractive index difference of the first cladding layer 4 ranges from 0 to 0.1%, which is a micro-doped ruthenium cladding layer; The relative refractive index difference of the second cladding layer 6 ranges from -1.3% to -0.3%, which is a deep fluorine-doped cladding layer.
  • the relative refractive index difference of the core layer 1 is ⁇ n1, Realized, where x 1 is the distance from any point in the core layer 1 to the axis thereof; a 1 is the gradient coefficient of the core layer 1 , b 1 is the gradient stability coefficient of the core layer 1; the value of a 1 The range is from 0.5% to 2%, and the range of b 1 is from 0 to 0.2%.
  • the relative refractive index difference of the first transition layer 3 is ⁇ n3, Implemented, any of the 3 x 3 in which a first transition point is located in the center of the fiber is the distance between the center concentrically with the outer edge of the Ge-doped core 2, a 3, b 3 is the transition coefficient; A 3 is taken The value ranges from 0.3 to 0.8, and the value of b 3 ranges from 0.3% to 0.8%.
  • the relative refractive index difference of the second transition layer 5 is ⁇ n5, Implemented, where x 5 is any point at which the second optical layer 5 in the center of a circle of the concentric circles and the distance between the outer edge of the first cladding layer 4 of, a 5, b 5 is a transition coefficient; A is 5 The value ranges from -1.0% to -0.3%, and b 5 ranges from 0 to 0.1%.
  • the relative refractive index difference of the third transition layer 7 is ⁇ n7, Implemented, wherein A 7 is a center of the third optical fiber at any point within the buffer layer 7 which is the distance between the center of the circle concentric with the outer edge of the second cladding layer 6, a 7, b 7 is the transition coefficient; A is 7 The value ranges from 0.1% to 0.4%, and b 7 ranges from -1.3% to -0.3%.
  • the present invention triple-controls the mode field of a small bend radius fiber through the erbium-doped core 2, the first cladding layer 4, the second cladding layer 6, and the third cladding layer 8, and passes through the core gradation.
  • the layer 1, the first transition layer 3, the second transition layer 5 and the third transition layer 7 are adapted to the G.652 mode, and the epitaxial mode field approximates the G.652 fiber mode field, and the core mode field is The characteristic mode field of a small bend radius fiber.
  • the diameter D8 of the third cladding layer 8 of the small-bend radius single-mode fiber is 125 ⁇ m
  • the relative refractive index difference of the core layer-grading layer 1 is ⁇ n1.
  • the relative refractive index ⁇ n2 of the erbium-doped core layer 2 remained stable at a constant 0.2%.
  • the relative refractive index difference of the first transition layer 3 is ⁇ n3, Implemented, any of the 3 x 3 in which a first transition point is located in the center of the fiber is the distance between the center concentrically with the outer edge of the Ge-doped core 2, a 3, b 3 is the transition coefficient; A 3 is taken The value range is 0.8 and b 3 has a value range of 0.3%.
  • the relative refractive index difference ⁇ n4 of the first cladding layer 4 is kept constant, constant at 0%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the first cladding layer 4 is 2.0.
  • the relative refractive index difference of the second transition layer 5 is ⁇ n5, Implemented, where x 5 is any point at which the second optical layer 5 in the center of the distance between the center of the circle concentric with the outer edge of the first cladding layer 4, a 5, b 5 is a transition coefficient; A is 5 The value range is -0.65%, and the value of b 5 is 0.05%.
  • the relative refractive index difference ⁇ n6 of the second cladding layer 6 is kept constant, constant at -0.8%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the second cladding layer 6 is 1.0.
  • the relative refractive index difference of the third transition layer 7 is ⁇ n7, Implemented, wherein A 7 is a center of the third optical fiber at any point within the buffer layer 7 which is the distance between the center of the circle concentric with the outer edge of the second cladding layer 6, a 7, b 7 is the transition coefficient; A is 7 The value range is 0.25%, and the value of b 7 is -0.8%.
  • the 1550 nm attenuation of the small bending radius single mode fiber is 0.191 dB/km, and the welding loss with the conventional G.652 fiber reaches 0.08 dB, and the additional loss at the 2 mm bending radius is 0.345dB.
  • This embodiment is basically the same as the structure of the first embodiment.
  • the diameter D8 of the third cladding layer 8 is 125 ⁇ m, and the relative refractive index difference of the core layer gradient layer 1 is ⁇ n1.
  • x 1 is the distance from any point in the core layer 1 to the axis thereof;
  • a 1 is the gradient coefficient of the core layer 1 ,
  • b 1 is the gradient stability coefficient of the core layer 1;
  • the value of a 1 The range is 1%, and the value of b 1 is 0.2%.
  • the relative refractive index ⁇ n2 of the erbium-doped core layer 2 remained stable at a constant of 0.5%.
  • the relative refractive index difference of the first transition layer 3 is ⁇ n3, Implemented, any of the 3 x 3 in which a first transition point is located in the center of the fiber is the distance between the center concentrically with the outer edge of the Ge-doped core 2, a 3, b 3 is the transition coefficient; A 3 is taken The value ranges from 0.5 and b 3 ranges from 0.5%.
  • the relative refractive index difference ⁇ n4 of the first cladding layer 4 is stable and constant at 0.05%.
  • the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the first cladding layer 4 is 1.0.
  • the relative refractive index difference of the second transition layer 5 is ⁇ n5, Implemented, where x 5 is any point at which the second optical layer 5 in the center of the distance between the center of the circle concentric with the outer edge of the first cladding layer 4, a 5, b 5 is a transition coefficient; A is 5 The value ranges from -0.3%, and b 5 ranges from 0.1%.
  • the relative refractive index difference ⁇ n6 of the second cladding layer 6 is kept constant, constant at -0.3%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the second cladding layer 6 is 0.5.
  • the relative refractive index difference of the third transition layer 7 is ⁇ n7, Implemented, wherein A 7 is a center of the third optical fiber at any point within the buffer layer 7 which is the distance between the center of the circle concentric with the outer edge of the second cladding layer 6, a 7, b 7 is the transition coefficient; A is 7 The value ranges from 0.1% to b. The range of b 7 is -0.3%.
  • the 1550 nm attenuation of the small-bend radius single-mode fiber is 0.193 dB/km, and the fusion loss with the conventional G.652 fiber reaches 0.11 dB, and the additional loss at the 2 mm bending radius is 0.332dB.
  • This embodiment is basically the same as the structure of the first embodiment.
  • the diameter D8 of the third cladding layer 8 is 125 ⁇ m, and the relative refractive index difference of the core layer gradient layer 1 is ⁇ n1.
  • x 1 is the distance from any point in the core layer 1 to the axis thereof;
  • a 1 is the gradient coefficient of the core layer 1 ,
  • b 1 is the gradient stability coefficient of the core layer 1;
  • the value of a 1 The range is 2%, and the value of b 1 is 0.1%.
  • the relative refractive index ⁇ n2 of the erbium-doped core layer 2 remained stable at a constant 0.8%.
  • the relative refractive index difference of the first transition layer 3 is ⁇ n3, Implemented, any of the 3 x 3 in which a first transition point is located in the center of the fiber is the distance between the center concentrically with the outer edge of the Ge-doped core 2, a 3, b 3 is the transition coefficient; A 3 is taken The value range is 0.3 and b 3 has a value range of 0.8%.
  • the relative refractive index difference ⁇ n4 of the first cladding layer 4 is kept constant, constant at 0.1%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the first cladding layer 4 is 0.5.
  • the relative refractive index difference of the second transition layer 5 is ⁇ n5, Implemented, where x 5 is any point at which the second optical layer 5 in the center of the distance between the center of the circle concentric with the outer edge of the first cladding layer 4, a 5, b 5 is a transition coefficient; A is 5 The value ranges from -1.3%, and b 5 ranges from 0%.
  • the relative refractive index difference ⁇ n6 of the second cladding layer 6 is kept constant, constant at -1.3%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the second cladding layer 6 is 0.2.
  • the relative refractive index difference of the third transition layer 7 is ⁇ n7, Implemented, wherein A 7 is a center of the third optical fiber at any point within the buffer layer 7 which is the distance between the center of the circle concentric with the outer edge of the second cladding layer 6, a 7, b 7 is the transition coefficient; A is 7 The value range is 0.4%, and the value of b 7 is -1.3%.
  • the 1550 nm attenuation of the small-bend radius single-mode fiber is 0.194 dB/km, and the fusion loss with the conventional G.652 fiber reaches 0.15 dB, and the additional loss at the 2 mm bending radius is 0.311dB.
  • the diameter D8 of the third cladding layer 8 in the embodiment is 80 ⁇ m, and the relative refractive index difference of the core layer gradient layer 1 is ⁇ n1, Realized, where x 1 is the distance from any point in the core layer 1 to the axis thereof; a 1 is the gradient coefficient of the core layer 1 , b 1 is the gradient stability coefficient of the core layer 1; the value of a 1 The range is 0.5%, and b 1 has a value range of 0.
  • the relative refractive index ⁇ n2 of the erbium-doped core layer 2 remained stable at a constant 0.2%.
  • the relative refractive index difference of the first transition layer 3 is ⁇ n3, Implemented, any of the 3 x 3 in which a first transition point is located in the center of the fiber is the distance between the center concentrically with the outer edge of the Ge-doped core 2, a 3, b 3 is the transition coefficient; A 3 is taken The value range is 0.8 and b 3 has a value range of 0.3%.
  • the relative refractive index difference ⁇ n4 of the first cladding layer 4 is kept constant, constant at 0, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the first cladding layer 4 is 2.0.
  • the relative refractive index difference of the second transition layer 5 is ⁇ n5, Implemented, where x 5 is any point at which the second optical layer 5 in the center of the distance between the center of the circle concentric with the outer edge of the first cladding layer 4, a 5, b 5 is a transition coefficient; A is 5 The value ranges from -0.75% and b 5 ranges from 0.06%.
  • the relative refractive index difference ⁇ n6 of the second cladding layer 6 is kept constant, constant at -0.9%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the second cladding layer 6 is 1.0.
  • the relative refractive index difference of the third transition layer 7 is ⁇ n7, Achieved, wherein a 7 is the distance between a concentric circle centered at the center of the fiber center at a point in the third transition layer 7 and a concentric circle centered on the outer edge of the second cladding layer 6 at the center of the fiber, a 7 , b 7 It is a transition coefficient; a 7 has a value range of 0.3%, and b 7 has a value range of -0.9%.
  • the 1550 nm attenuation of the small-bend radius single-mode fiber is 0.195 dB/km, and the fusion loss with the conventional G.652 fiber reaches 0.13 dB, and the additional loss at the 2 mm bending radius is 0.332dB.
  • the structure of the embodiment is substantially the same as that of the embodiment 5.
  • the diameter D8 of the third cladding layer 8 is 80 ⁇ m, and the relative refractive index difference of the core layer gradient layer 1 is ⁇ n1.
  • x 1 is the distance from any point in the core layer 1 to the axis thereof;
  • a 1 is the gradient coefficient of the core layer 1 ,
  • b 1 is the gradient stability coefficient of the core layer 1;
  • the value of a 1 The range is 1.3%, and the value of b 1 is 0.2%.
  • the relative refractive index ⁇ n2 of the erbium-doped core layer 2 remained stable and was constant at 0.6%.
  • the relative refractive index difference of the first transition layer 3 is ⁇ n3, Implemented, any of the 3 x 3 wherein a first transition point is located in the center of the fiber 2 is the distance between the outer edge of the Ge-doped core concentrically with the center of the circle, a 3, b 3 is the transition coefficient; A 3 is taken The value range is 0.6 and the value of b 3 is 0.45%.
  • the relative refractive index difference ⁇ n4 of the first cladding layer 4 is kept constant, constant at 0.05%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the first cladding layer 4 is 0.9.
  • the relative refractive index difference of the second transition layer 5 is ⁇ n5, Implemented, where x 5 is any point at which the second optical layer 5 in the center of the distance between the center of the circle concentric with the outer edge of the first cladding layer 4, a 5, b 5 is a transition coefficient; A is 5 The value ranges from -0.3%, and b 5 ranges from 0.1%.
  • the relative refractive index difference ⁇ n6 of the second cladding layer 6 is kept constant, constant at -0.3%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the second cladding layer 6 is 0.4.
  • the relative refractive index difference of the third transition layer 7 is ⁇ n7, Implemented, wherein A 7 is a center of the third optical fiber at any point within the buffer layer 7 which is the distance between the center of the circle concentric with the outer edge of the second cladding layer 6, a 7, b 7 is the transition coefficient; A is 7 The value ranges from 0.1% to b. The range of b 7 is -0.3%.
  • the 1550 nm attenuation of the small-bend radius single-mode fiber is 0.197 dB/km, and the fusion loss with the conventional G.652 fiber reaches 0.16 dB, and the additional loss at the 2 mm bending radius is 0.312dB.
  • the structure of the embodiment is substantially the same as that of the embodiment 5.
  • the diameter D8 of the third cladding layer 8 is 80 ⁇ m, and the relative refractive index difference of the core layer gradient layer 1 is ⁇ n1.
  • x 1 is the distance from any point in the core layer 1 to the axis thereof;
  • a 1 is the gradient coefficient of the core layer 1 ,
  • b 1 is the gradient stability coefficient of the core layer 1;
  • the value of a 1 The range is 2%, and the value of b 1 is 0.1%.
  • the relative refractive index ⁇ n2 of the erbium-doped core layer 2 remained stable at a constant 0.8%.
  • the relative refractive index difference of the first transition layer 3 is ⁇ n3, Implemented, any of the 3 x 3 in which a first transition point is located in the center of the fiber is the distance between the center concentrically with the outer edge of the Ge-doped core 2, a 3, b 3 is the transition coefficient; A 3 is taken The value range is 0.3 and b 3 has a value range of 0.8%.
  • the relative refractive index difference ⁇ n4 of the first cladding layer 4 is kept constant, constant at 0.1%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the first cladding layer 4 is 0.5.
  • the relative refractive index difference of the second transition layer 5 is ⁇ n5, Implemented, where x 5 is any point at which the second optical layer 5 in the center of the distance between the center of the circle concentric with the outer edge of the first cladding layer 4, a 5, b 5 is a transition coefficient; A is 5 The value ranges from -1.3%, and b 5 ranges from 0.
  • the relative refractive index difference ⁇ n6 of the second cladding layer 6 is kept constant, constant at -1.3%, and the ratio of the thickness L2 of the erbium-doped core layer 2 to the thickness L4 of the second cladding layer 6 is 0.2.
  • the relative refractive index difference of the third transition layer 7 is ⁇ n7, Implemented, wherein A 7 is a center of the third optical fiber at any point within the buffer layer 7 which is the distance between the center of the circle concentric with the outer edge of the second cladding layer 6, a 7, b 7 is the transition coefficient; A is 7 The value range is 0.4%, and the value of b 7 is -1.3%.
  • the 1550 nm attenuation of the small bending radius single mode fiber is 0.199 dB/km, and the welding loss with the conventional G.652 fiber reaches 0.19 dB, and the additional loss at the bending radius of 2 mm is 0.297dB.

Abstract

一种具有兼容性的小弯曲半径单模光纤，包括由内至外同心设置的芯层渐变层（1）、掺锗芯层（2）、第一过渡层（3）、第一包层（4）、第二过渡层（5）、第二包层（6）、第三过渡层（7）和第三包层（8）；芯层渐变层（1）的相对折射率差为Δn1，以Δn1=a1(x1+x2 1+x3 1)+b1实现，第一过渡层（3）的相对折射率差为Δn3，以Δn3=b3(1-a3x2 3)0.5实现，第二过渡层（5）的相对折射率差为Δn5，以Δn5=a5x2 5+b5实现，所述第三过渡层（7）的相对折射率差为Δn7，以Δn7=a7x2 7+b7实现。所述具有兼容性的小弯曲半径单模光纤，实现弯曲半径达2mm以下的超强抗弯曲能力，同时可实现与常规单模光纤的良好兼容。

Description

一种具有兼容性的小弯曲半径单模光纤 技术领域
本发明涉及单模光纤领域，具体来讲是一种具有兼容性的小弯曲半径单模光纤。
背景技术
目前通信网络的建设带动了光纤入户和ODN技术的飞速发展，这二者都对光纤的抗弯曲性能提出了很高的要求。光纤在弯曲条件下，会发生光信号的衰减，这是由于光纤弯曲后有部分功率的光泄漏了出去，这些泄漏出的光将会被涂层材料等吸收从而发热。有研究发现常规G.652D单模光纤做成的跳线，当在弯曲半径15mm条件下长时间工作时，由于持续的发热，会造成其两个连接端点间的损坏，造成接续损耗的持续降低，并带来不可恢复的损害。对于ODN中小配线盒内将大量光纤弯曲布线而言，由于光纤弯曲带来的光功率泄漏造成的发热将会给ODN的通信稳定带来严重影响。
光纤的抗弯曲性能的提升不仅有利于保证光信号传输的高质量，而且可以减小其所在通信系统的整体发热量，提升该系统的整体性能。世界各先进光纤企业针对通信网络的热点技术ODN技术对超强抗弯光纤技术的需求，展开了深入的研究。我国的光纤光缆企业目前主要集中在ITUT-G.657所要求的弯曲半径10mm或更小的小弯曲半径单模光纤如G.657B2/3的技术研究。
但是随着ODN技术为适应光纤网络和3G网络的建设对占地空间的要求，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，其对光纤的弯曲性能要求越来越高，越来越多的应用需要弯曲半径小于3mm乃至2mm以下的超强抗弯单模光纤。同时，这种超强抗弯单模还需要与普通单模光纤具有良好的兼容性，二者之间的单点熔接损耗需要控制在一个可以接受的较小范围内。
对于光纤入户而言，其所选用的光纤事实上需要具有两个关键特性，其一是抗弯曲能力，即小弯曲半径低损耗的光信号传输，这是其根本特性；其二是需要与常规G.652光纤具有一定的兼容特性。因为在当前骨干网和城域网乃至接入网的前端，大量铺设的光纤基本都是G.652光纤，如果在光纤入户段选用的光纤与其兼容特性差，即使其具有良好的弯曲性能，但是由于其在与常规G.652光纤熔接时损耗大，也会造成光信号在二者对接时大量损耗，从而额外需要更大的光增益，或者入户端干脆仍选用G.652光纤。因此，虽然当前已有抗弯曲光纤，但是由于其与常规G.652光纤兼容性能差，并不能满足光纤入户市场的大量采用。
发明内容
针对现有技术中存在的缺陷，本发明的目的在于提供一种具有兼容性的小弯曲半径单模光纤，实现弯曲半径达2mm以下的超强抗弯曲能力，同时可实现与常规单模光纤的良好兼容。
为达到以上目的，本发明采取的技术方案是：一种具有兼容性的小弯曲半径单模光纤，包括同心设置的芯层渐变层、掺锗芯层，以及由内至外同心设置的第一包层、第二包层和第三包层，所述掺锗芯层与第一包层之间设有第一过渡层，第一包层和第二包层之间设有第二过渡层，第二包层和第三包层之间设有第三过渡层；所述芯层渐变层的相对折射率差为Δn1，是以
Figure PCTCN2014087158-appb-000001
实现，其中 x1为芯层渐变层内任一点到其中轴线的距离；a1为芯层渐变层的渐变系数，b1为芯层渐变层的渐变稳定系数，a1的取值范围为0.5％～2％，b1的取值范围为0～0.2％；所述第一过渡层的相对折射率差为Δn3，是以
Figure PCTCN2014087158-appb-000002
实现，其中x3为第一过渡层3内任一点所处的以光纤中心为圆心的同心圆与掺锗芯层2外边缘之间的距离，a3、b3为过渡系数，a3的取值范围为0.3～0.8，b3的取值范围为0.3％～0.8％；所述第二过渡层的相对折射率差为Δn5，是以
Figure PCTCN2014087158-appb-000003
实现，其中x5为第二过渡层5内任一点所处的以光纤中心为圆心的同心圆与第一包层4外边缘之间的距离，a5、b5为过渡系数，a5的取值范围为-1.0％～-0.3％，b5的取值范围为0～0.1％；所述第三过渡层的相对折射率差为Δn7，是以
Figure PCTCN2014087158-appb-000004
实现，其中x7为第三过渡层7内任一点所处的以光纤中心为圆心的同心圆与第二包层6外边缘之间的距离，a7、b7为过渡系数，a7的取值范围为0.1％～0.4％，b7的取值范围为-1.3％～-0.3％。
在上述技术方案的基础上，所述掺锗芯层的厚度与第一包层的厚度比值范围在0.5～2.0之间。
在上述技术方案的基础上，所述掺锗芯层的厚度与第二包层的厚度比值范围在0.2～1.0之间。
在上述技术方案的基础上，所述掺锗芯层的相对折射率差的范围是0.2％～0.8％。
在上述技术方案的基础上，所述第一包层的相对折射率差的范围是0～0.1％。
在上述技术方案的基础上，所述第二包层的相对折射率差的范围是-1.3％～-0.3％。
在上述技术方案的基础上，所述第三包层的直径为80μm或 125μm，为石英包层。
在上述技术方案的基础上，当工作波长在1550nm时，所述小弯曲半径单模光纤衰减在0.2dB/km以下，弯曲半径在2mm时，附加损耗在0.35dB以下。
本发明的有益效果在于：
1、所述惨锗芯层外面设有多个包层，低掺锗含量的第一包层、深掺氟含量的第二包层和由石英包层组成的第三包层，从而形成了一种山形波导结构，从减少宏弯损耗和微弯损耗两个方面来加强光纤的抗弯曲能力。
2、掺锗芯层与第一包层、第一包层与第二包层、第二包层与第三包层之间均设立过渡层，并在掺锗芯层内采用芯层渐变层，从而优化光纤的模式特性和应力特性，从而小弯曲半径单模光纤与常规G.652单模光纤熔接时，其熔接点的损耗可以控制到很小的程度，与常规单模光纤的良好兼容特性，从而为光纤入户、ODN技术用光纤奠定基础。
附图说明
图1为本发明具有兼容性的小弯曲半径单模光纤端面结构示意图；
图2为本发明具有兼容性的小弯曲半径单模光纤波导结构示意图；
图3为具有兼容性的小弯曲半径单模光纤模场控制示意图；
图4为图1中包层直径125μm时的光纤弯曲附加损耗；
图5为图1中包层直径80μm时的光纤弯曲附加损耗。
具体实施方式
以下结合附图对本发明作进一步详细说明。
如图1所示，本发明具有兼容性的小弯曲半径单模光纤，包括由内至外同心设置的芯层渐变层1、掺锗芯层2、第一过渡层3、第一包层4、第二过渡层5、第二包层6、第三过渡层7和第三包层8。其中，芯层渐变层1在掺锗芯层2的内部，第一过渡层2位于掺锗的芯层1与第一包层间4之间，第二过渡层5位于第1包层4与第二包层6之间，第三过渡层7位于第二包层6与第三包层8之间。所述掺锗芯层2的厚度L2与第一包层4的厚度L4比值范围在0.5～2.0之间。所述掺锗芯层2的厚度L2与第二包层6的厚度L6比值范围在0.2～1.0之间。所述第三包层8为石英包层，其直径D8为80μm或125μm，涂覆后本发明小弯曲半径单模光纤直径为200μm或245μm。
如图2所示，所述芯层渐变层1的折射率为n1，掺锗芯层2的折射率为n2，第一过渡层3的折射率为n3，第1包层4的折射率为n4，第三过渡层5的折射率为n5，第二包层6的折射率为n6，第三过渡层7的折射率为n7，第三包层8的折射率为n8；选取第三包层8的折射率n8为等效石英包层的折射率n。在实现上述折射率时，采用相对折射率差的办法，以石英包层的折射率n为基准，各波导层与石英包层之间有一个相对折射率差，以此为标准来测算并实现本发明的山形波导结构所包括的各层折射率。相对折射率差采用公式为：
Δn＝(n′-n)/(n′+n)×100％   公式(1)
其中，n为石英包层的折射率，即本发明对应为第三包层8的折射率n8，n′为与之相比较的对应层的折射率。
对本发明而言，当计算芯层渐变层1的折射率与石英包层相对折射率差时，公式中n′取值纤芯折射率n1；当计算掺锗芯层折射率与石 英包层相对折射率差时，公式中n′取值纤芯折射率n2；当计算第一过渡层3芯层与石英包层的相对折射率差时，式中n′取值第一过渡层折射率n3；当计算第一包层4与石英包层的相对折射率差时，式中n′取值第一包层折射率n4；当计算第二过渡层5与石英包层的相对折射率差时，式中n′取值第二过渡层折射率n5；当计算第二包层6与石英包层的折射率差时，式中n′取值掺氟包层的折射率n6；当计算第三过渡层7与石英包层的折射率差时，式中n′取值第三过渡层的折射率n7。
则由公式(1)可以分别得到芯层渐变层1的相对折射率差Δn1，掺锗芯层2的相对折射率差为Δn2，第一过渡层3的相对折射率差为Δn3，第一包层4的相对折射率差为Δn4，第二过渡层5的相对折射率差为Δn5，第二包层6的相对折射率差为Δn6，第三过渡层7的相对折射率差为Δn7。所述掺锗芯层2的相对折射率差的范围是0.2％～0.8％；所述第一包层4的相对折射率差的范围是0～0.1％，为微掺锗包层；所述第二包层6的相对折射率差的范围是-1.3％～-0.3％，为深掺氟包层。
所述芯层渐变层1的相对折射率差为Δn1，是以
Figure PCTCN2014087158-appb-000005
Figure PCTCN2014087158-appb-000006
实现，其中x1为芯层渐变层1内任一点到其中轴线的距离；a1为芯层渐变层1的渐变系数，b1为芯层渐变层1的渐变稳定系数；a1的取值范围为0.5％～2％，b1的取值范围为0～0.2％。
所述第一过渡层3的相对折射率差为Δn3，是以
Figure PCTCN2014087158-appb-000007
Figure PCTCN2014087158-appb-000008
实现，其中x3第一过渡层3内任一点所处的以光纤中心为圆心的同心圆与掺锗芯层2外边缘之间的距离，a3、b3为过渡系数；a3的取值范围为0.3～0.8，b3的取值范围为0.3％～0.8％。
所述第二过渡层5的相对折射率差为Δn5，是以
Figure PCTCN2014087158-appb-000009
实现，其中x5为第二过渡层5内任一点所处的以光纤中心为圆心的同 心圆与第一包层4外边缘之间的距离，a5、b5为过渡系数；a5的取值范围为-1.0％～-0.3％，b5的取值范围为0～0.1％。
所述第三过渡层7的相对折射率差为Δn7，是以
Figure PCTCN2014087158-appb-000010
实现，其中a7为第三过渡层7内任一点所处的以光纤中心为圆心的同心圆与第二包层6外边缘之间的距离，a7、b7为过渡系数；a7的取值范围为0.1％～0.4％，b7的取值范围为-1.3％～-0.3％。
如图3所示，本发明通过掺锗纤芯2、第一包层4、第二包层6和第三包层8对小弯曲半径光纤的模场进行了三重控制，并通过纤芯渐变层1、第一过渡层3、第二过渡层5和第三过渡层7对模场特性进行了适应G.652的优化，其外延模场近似G.652光纤模场，其核心模场则为小弯曲半径光纤的特性模场。
下面通过具体实施例对本发明做进一步说明。
实施例1：
本实施例中小弯曲半径单模光纤的第三包层8的直径D8为125μm，芯层渐变层1的相对折射率差为Δn1，以
Figure PCTCN2014087158-appb-000011
Figure PCTCN2014087158-appb-000012
实现，其中x1为芯层渐变层1内任一点到其中轴线的距离；a1为芯层渐变层1的渐变系数，b1为芯层渐变层1的渐变稳定系数；a1的取值范围为0.5％，b1的取值范围为0。
掺锗芯层2的相对折射率Δn2保持稳定，恒定为0.2％。
所述第一过渡层3的相对折射率差为Δn3，以
Figure PCTCN2014087158-appb-000013
Figure PCTCN2014087158-appb-000014
实现，其中x3第一过渡层3内任一点所处的以光纤中心为圆心的同心圆与掺锗芯层2外边缘之间的距离，a3、b3为过渡系数；a3的取值范围为0.8，b3的取值范围为0.3％。
所述第一包层4的相对折射率差Δn4保持稳定，恒定为0％，掺锗芯层2的厚度L2与第一包层4的厚度L4的比值为2.0。
所述第二过渡层5的相对折射率差为Δn5，以
Figure PCTCN2014087158-appb-000015
实现，其中x5为第二过渡层5内任一点所处的以光纤中心为圆心的同心圆与第一包层4外边缘之间的距离，a5、b5为过渡系数；a5的取值范围为-0.65％，b5的取值范围为0.05％。
所述第二包层6的相对折射率差Δn6保持稳定，恒定为-0.8％，掺锗芯层2的厚度L2与第二包层6的厚度L4的比值在1.0。
所述第三过渡层7的相对折射率差为Δn7，以
Figure PCTCN2014087158-appb-000016
实现，其中a7为第三过渡层7内任一点所处的以光纤中心为圆心的同心圆与第二包层6外边缘之间的距离，a7、b7为过渡系数；a7的取值范围为0.25％，b7的取值范围为-0.8％。
由图4中可知，本实施例中，小弯曲半径单模光纤的1550nm衰减为0.191dB/km，其与常规G.652光纤的熔接损耗达到0.08dB，其在2mm弯曲半径下的附加损耗为0.345dB。
实施例2：
本实施例与实施例1结构基本相同，所述第三包层8的直径D8为125μm，芯层渐变层1的相对折射率差为Δn1，以
Figure PCTCN2014087158-appb-000017
Figure PCTCN2014087158-appb-000018
实现，其中x1为芯层渐变层1内任一点到其中轴线的距离；a1为芯层渐变层1的渐变系数，b1为芯层渐变层1的渐变稳定系数；a1的取值范围为1％，b1的取值范围为0.2％。
掺锗芯层2的相对折射率Δn2保持稳定，恒定为0.5％。
所述第一过渡层3的相对折射率差为Δn3，以
Figure PCTCN2014087158-appb-000019
Figure PCTCN2014087158-appb-000020
实现，其中x3第一过渡层3内任一点所处的以光纤中心为圆心的同心圆与掺锗芯层2外边缘之间的距离，a3、b3为过渡系数；a3的取值范围为0.5，b3的取值范围为0.5％。
所述第一包层4的相对折射率差Δn4保持稳定，恒定为0.05％， 掺锗芯层2的厚度L2与第一包层4的厚度L4的比值为1.0。
所述第二过渡层5的相对折射率差为Δn5，以
Figure PCTCN2014087158-appb-000021
实现，其中x5为第二过渡层5内任一点所处的以光纤中心为圆心的同心圆与第一包层4外边缘之间的距离，a5、b5为过渡系数；a5的取值范围为-0.3％，b5的取值范围为0.1％。
所述第二包层6的相对折射率差Δn6保持稳定，恒定为-0.3％，掺锗芯层2的厚度L2与第二包层6的厚度L4的比值在0.5。
所述第三过渡层7的相对折射率差为Δn7，以
Figure PCTCN2014087158-appb-000022
实现，其中a7为第三过渡层7内任一点所处的以光纤中心为圆心的同心圆与第二包层6外边缘之间的距离，a7、b7为过渡系数；a7的取值范围为0.1％，b7的取值范围为-0.3％。
由图4中可知，本实施例中，小弯曲半径单模光纤的1550nm衰减为0.193dB/km，其与常规G.652光纤的熔接损耗达到0.11dB，其在2mm弯曲半径下的附加损耗为0.332dB。
实施例3：
本实施例与实施例1结构基本相同，所述第三包层8的直径D8为125μm，芯层渐变层1的相对折射率差为Δn1，以
Figure PCTCN2014087158-appb-000023
Figure PCTCN2014087158-appb-000024
实现，其中x1为芯层渐变层1内任一点到其中轴线的距离；a1为芯层渐变层1的渐变系数，b1为芯层渐变层1的渐变稳定系数；a1的取值范围为2％，b1的取值范围为0.1％。
掺锗芯层2的相对折射率Δn2保持稳定，恒定为0.8％。
所述第一过渡层3的相对折射率差为Δn3，以
Figure PCTCN2014087158-appb-000025
Figure PCTCN2014087158-appb-000026
实现，其中x3第一过渡层3内任一点所处的以光纤中心为圆心的同心圆与掺锗芯层2外边缘之间的距离，a3、b3为过渡系数；a3的取值范围为0.3，b3的取值范围为0.8％。
所述第一包层4的相对折射率差Δn4保持稳定，恒定为0.1％，掺锗芯层2的厚度L2与第一包层4的厚度L4的比值为0.5。
所述第二过渡层5的相对折射率差为Δn5，以
Figure PCTCN2014087158-appb-000027
实现，其中x5为第二过渡层5内任一点所处的以光纤中心为圆心的同心圆与第一包层4外边缘之间的距离，a5、b5为过渡系数；a5的取值范围为-1.3％，b5的取值范围为0％。
所述第二包层6的相对折射率差Δn6保持稳定，恒定为-1.3％，掺锗芯层2的厚度L2与第二包层6的厚度L4的比值在0.2。
所述第三过渡层7的相对折射率差为Δn7，以
Figure PCTCN2014087158-appb-000028
实现，其中a7为第三过渡层7内任一点所处的以光纤中心为圆心的同心圆与第二包层6外边缘之间的距离，a7、b7为过渡系数；a7的取值范围为0.4％，b7的取值范围为-1.3％。
由图4中可知，本实施例中，小弯曲半径单模光纤的1550nm衰减为0.194dB/km，其与常规G.652光纤的熔接损耗达到0.15dB，其在2mm弯曲半径下的附加损耗为0.311dB。
实施例4：
本实施例所述第三包层8的直径D8为80μm，芯层渐变层1的相对折射率差为Δn1，以
Figure PCTCN2014087158-appb-000029
实现，其中x1为芯层渐变层1内任一点到其中轴线的距离；a1为芯层渐变层1的渐变系数，b1为芯层渐变层1的渐变稳定系数；a1的取值范围为0.5％，b1的取值范围为0。
掺锗芯层2的相对折射率Δn2保持稳定，恒定为0.2％。
所述第一过渡层3的相对折射率差为Δn3，以
Figure PCTCN2014087158-appb-000030
Figure PCTCN2014087158-appb-000031
实现，其中x3第一过渡层3内任一点所处的以光纤中心为圆心的同心圆与掺锗芯层2外边缘之间的距离，a3、b3为过渡系数；a3的 取值范围为0.8，b3的取值范围为0.3％。
所述第一包层4的相对折射率差Δn4保持稳定，恒定为0，掺锗芯层2的厚度L2与第一包层4的厚度L4的比值为2.0。
所述第二过渡层5的相对折射率差为Δn5，以
Figure PCTCN2014087158-appb-000032
实现，其中x5为第二过渡层5内任一点所处的以光纤中心为圆心的同心圆与第一包层4外边缘之间的距离，a5、b5为过渡系数；a5的取值范围为-0.75％，b5的取值范围为0.06％。
所述第二包层6的相对折射率差Δn6保持稳定，恒定为-0.9％，掺锗芯层2的厚度L2与第二包层6的厚度L4的比值在1.0。
所述第三过渡层7的相对折射率差为Δn7，以
Figure PCTCN2014087158-appb-000033
实现，其中a7为第三过渡层7内任一点所处的以光纤中心为圆心的同心圆与第二包层6外边缘以光纤中心为圆心的同心圆间的距离，a7、b7为过渡系数；a7的取值范围为0.3％，b7的取值范围为-0.9％。
由图5中可知，本实施例中，小弯曲半径单模光纤的1550nm衰减为0.195dB/km，其与常规G.652光纤的熔接损耗达到0.13dB，其在2mm弯曲半径下的附加损耗为0.332dB。
实施例5：
本实施例与实施例5结构基本相同，所述第三包层8的直径D8为80μm，芯层渐变层1的相对折射率差为Δn1，以
Figure PCTCN2014087158-appb-000034
Figure PCTCN2014087158-appb-000035
实现，其中x1为芯层渐变层1内任一点到其中轴线的距离；a1为芯层渐变层1的渐变系数，b1为芯层渐变层1的渐变稳定系数；a1的取值范围为1.3％，b1的取值范围为0.2％。
掺锗芯层2的相对折射率Δn2保持稳定，恒定为0.6％。
所述第一过渡层3的相对折射率差为Δn3，以
Figure PCTCN2014087158-appb-000036
Figure PCTCN2014087158-appb-000037
实现，其中x3第一过渡层3内任一点所处的以光纤中心为圆 心的同心圆与掺锗芯层2外边缘之间的距离，a3、b3为过渡系数；a3的取值范围为0.6，b3的取值范围为0.45％。
所述第一包层4的相对折射率差Δn4保持稳定，恒定为0.05％，掺锗芯层2的厚度L2与第一包层4的厚度L4的比值为0.9。
所述第二过渡层5的相对折射率差为Δn5，以
Figure PCTCN2014087158-appb-000038
实现，其中x5为第二过渡层5内任一点所处的以光纤中心为圆心的同心圆与第一包层4外边缘之间的距离，a5、b5为过渡系数；a5的取值范围为-0.3％，b5的取值范围为0.1％。
所述第二包层6的相对折射率差Δn6保持稳定，恒定为-0.3％，掺锗芯层2的厚度L2与第二包层6的厚度L4的比值在0.4。
所述第三过渡层7的相对折射率差为Δn7，以
Figure PCTCN2014087158-appb-000039
实现，其中a7为第三过渡层7内任一点所处的以光纤中心为圆心的同心圆与第二包层6外边缘之间的距离，a7、b7为过渡系数；a7的取值范围为0.1％，b7的取值范围为-0.3％。
由图5中可知，本实施例中，小弯曲半径单模光纤的1550nm衰减为0.197dB/km，其与常规G.652光纤的熔接损耗达到0.16dB，其在2mm弯曲半径下的附加损耗为0.312dB。
实施例6：
本实施例与实施例5结构基本相同，所述第三包层8的直径D8为80μm，芯层渐变层1的相对折射率差为Δn1，以
Figure PCTCN2014087158-appb-000040
Figure PCTCN2014087158-appb-000041
实现，其中x1为芯层渐变层1内任一点到其中轴线的距离；a1为芯层渐变层1的渐变系数，b1为芯层渐变层1的渐变稳定系数；a1的取值范围为2％，b1的取值范围为0.1％。
掺锗芯层2的相对折射率Δn2保持稳定，恒定为0.8％。
所述第一过渡层3的相对折射率差为Δn3，以
Figure PCTCN2014087158-appb-000042
Figure PCTCN2014087158-appb-000043
实现，其中x3第一过渡层3内任一点所处的以光纤中心为圆心的同心圆与掺锗芯层2外边缘之间的距离，a3、b3为过渡系数；a3的取值范围为0.3，b3的取值范围为0.8％。
所述第一包层4的相对折射率差Δn4保持稳定，恒定为0.1％，掺锗芯层2的厚度L2与第一包层4的厚度L4的比值为0.5。
所述第二过渡层5的相对折射率差为Δn5，以
Figure PCTCN2014087158-appb-000044
实现，其中x5为第二过渡层5内任一点所处的以光纤中心为圆心的同心圆与第一包层4外边缘之间的距离，a5、b5为过渡系数；a5的取值范围为-1.3％，b5的取值范围为0。
所述第二包层6的相对折射率差Δn6保持稳定，恒定为-1.3％，掺锗芯层2的厚度L2与第二包层6的厚度L4的比值在0.2。
所述第三过渡层7的相对折射率差为Δn7，以
Figure PCTCN2014087158-appb-000045
实现，其中a7为第三过渡层7内任一点所处的以光纤中心为圆心的同心圆与第二包层6外边缘之间的距离，a7、b7为过渡系数；a7的取值范围为0.4％，b7的取值范围为-1.3％。
由图5中可知，本实施例中，小弯曲半径单模光纤的1550nm衰减为0.199dB/km，其与常规G.652光纤的熔接损耗达到0.19dB，其在2mm弯曲半径下的附加损耗为0.297dB。
本发明不局限于上述实施方式，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本发明的保护范围之内。本说明书中未作详细描述的内容属于本领域专业技术人员公知的现有技术。

Claims (8)

  1. 一种具有兼容性的小弯曲半径单模光纤，包括同心设置的芯层渐变层、掺锗芯层，以及由内至外同心设置的第一包层、第二包层和第三包层，其特征在于：所述掺锗芯层与第一包层之间设有第一过渡层，第一包层和第二包层之间设有第二过渡层，第二包层和第三包层之间设有第三过渡层；
    所述芯层渐变层的相对折射率差为Δn1，是以
    Figure PCTCN2014087158-appb-100001
    Figure PCTCN2014087158-appb-100002
    实现，其中x1为芯层渐变层内任一点到其中轴线的距离；a1为芯层渐变层的渐变系数，b1为芯层渐变层的渐变稳定系数，a1的取值范围为0.5％～2％，b1的取值范围为0～0.2％；
    所述第一过渡层的相对折射率差为Δn3，是以
    Figure PCTCN2014087158-appb-100003
    Figure PCTCN2014087158-appb-100004
    实现，其中x3为第一过渡层3内任一点所处的以光纤中心为圆心的同心圆与掺锗芯层2外边缘之间的距离，a3、b3为过渡系数，a3的取值范围为0.3～0.8，b3的取值范围为0.3％～0.8％；
    所述第二过渡层的相对折射率差为Δn5，是以
    Figure PCTCN2014087158-appb-100005
    实现，其中x5为第二过渡层5内任一点所处的以光纤中心为圆心的同心圆与第一包层4外边缘之间的距离，a5、b5为过渡系数，a5的取值范围为-1.0％～-0.3％，b5的取值范围为0～0.1％；
    所述第三过渡层的相对折射率差为Δn7，是以
    Figure PCTCN2014087158-appb-100006
    实现，其中x7为第三过渡层7内任一点所处的以光纤中心为圆心的同心圆与第二包层6外边缘之间的距离，a7、b7为过渡系数，a7的取值范围为0.1％～0.4％，b7的取值范围为-1.3％～-0.3％。
  2. 如权利要求1所述具有兼容性的小弯曲半径单模光纤，其特征在于：所述掺锗芯层的厚度与第一包层的厚度比值范围在0.5～2.0之间。
  3. 如权利要求1所述具有兼容性的小弯曲半径单模光纤，其特征在于：所述掺锗芯层的厚度与第二包层的厚度比值范围在0.2～1.0之间。
  4. 如权利要求1所述具有兼容性的小弯曲半径单模光纤，其特征在于：所述掺锗芯层的相对折射率差的范围是0.2％～0.8％。
  5. 如权利要求1所述具有兼容性的小弯曲半径单模光纤，其特征在于：所述第一包层的相对折射率差的范围是0～0.1％。
  6. 如权利要求1所述具有兼容性的小弯曲半径单模光纤，其特征在于：所述第二包层的相对折射率差的范围是-1.3％～-0.3％。
  7. 如权利要求1所述具有兼容性的小弯曲半径单模光纤，其特征在于：所述第三包层的直径为80μm或125μm，为石英包层。
  8. 如权利要求1所述具有兼容性的小弯曲半径单模光纤，其特征在于：当工作波长在1550nm时，所述小弯曲半径单模光纤衰减在0.2dB/km以下，弯曲半径在2mm时，附加损耗在0.35dB以下。
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