CN116589174B - Quartz prefabricated part, optical fiber and optical fiber preparation method - Google Patents

Quartz prefabricated part, optical fiber and optical fiber preparation method Download PDF

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Publication number
CN116589174B
CN116589174B CN202310527894.9A CN202310527894A CN116589174B CN 116589174 B CN116589174 B CN 116589174B CN 202310527894 A CN202310527894 A CN 202310527894A CN 116589174 B CN116589174 B CN 116589174B
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optical fiber
layer
refractive index
index difference
relative refractive
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CN116589174A (en
Inventor
丁春来
朱钱生
曹珊珊
油光磊
徐海涛
郭雨凡
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Jiangdong Technology Co ltd
Zhongtian Technologies Fibre Optics Co Ltd
Jiangsu Zhongtian Technology Co Ltd
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Jiangdong Technology Co ltd
Zhongtian Technologies Fibre Optics Co Ltd
Jiangsu Zhongtian Technology Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/02—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor
    • C03B37/025—Manufacture of glass fibres or filaments by drawing or extruding, e.g. direct drawing of molten glass from nozzles; Cooling fins therefor from reheated softened tubes, rods, fibres or filaments, e.g. drawing fibres from preforms
    • C03B37/027—Fibres composed of different sorts of glass, e.g. glass optical fibres
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C25/00—Surface treatment of fibres or filaments made from glass, minerals or slags
    • C03C25/10—Coating
    • C03C25/104—Coating to obtain optical fibres
    • C03C25/1065—Multiple coatings
    • 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

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Glass Compositions (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

The application relates to the technical field of optical fibers, in particular to a quartz prefabricated member, an optical fiber and a preparation method of the optical fiber. The quartz prefabricated member is used for preparing optical fibers and comprises a core layer and a cladding layer surrounding the core layer, wherein the relative refractive index difference of the core layer is larger than that of the cladding layer, and the core layer comprises the following components from inside to outside: a parabolic graded layer and a linear graded layer, the cladding layer comprising a depressed layer and an outer cladding surrounding said depressed layer, the depressed layer having a relative refractive index difference no greater than zero and the depressed layer having a relative refractive index difference less than the outer cladding. The optical fiber is prepared by the quartz prefabricated member, so that the mechanical strength of the prepared optical fiber can be improved.

Description

Quartz prefabricated part, optical fiber and optical fiber preparation method
Technical Field
The application relates to the technical field of optical fibers, in particular to a quartz prefabricated member, an optical fiber and a preparation method of the optical fiber.
Background
Optical fibers are favored by those skilled in the art for their small size, light weight, and resistance to electromagnetic interference, and have developed very rapidly. Optical fibers are a critical component of a communication system, and their reliability directly affects the stability of the communication system.
The tensile strength of an optical fiber is one of the important indicators for evaluating the reliability of the optical fiber. With the trend of miniaturization of optical fiber size, how to ensure the mechanical strength of the optical fiber is also extremely important.
Disclosure of Invention
In view of the foregoing, embodiments of the present application provide a quartz preform, an optical fiber, and a method for manufacturing an optical fiber, which aim to improve the tensile mechanical strength of the optical fiber.
The embodiment of the application provides a quartz prefabricated member, which is used for preparing an optical fiber, and comprises a core layer and a cladding layer surrounding the core layer, wherein the relative refractive index difference of the core layer is larger than that of the cladding layer, and the core layer comprises the following components from inside to outside: a parabolic graded layer and a linear graded layer, the cladding layer comprising a depressed layer and an outer cladding layer surrounding the depressed layer, the depressed layer having a relative refractive index difference no greater than zero and the depressed layer having a relative refractive index difference less than the outer cladding layer.
The quartz prefabricated member of the embodiment of the application can be used for preparing optical fibers, and the refractive index profile of the core layer and the concave layer with parabolic gradual change and linear gradual change is adopted by the quartz prefabricated member, so that the uniformity of the internal viscosity of the core layer can be improved, the matching property of the core layer and the cladding layer is improved, the internal stress in the preparation process of the optical fibers is reduced, the prepared optical fibers have stronger strength, in addition, in the refractive index profile, the relative refractive index difference of the concave layer is not more than zero, so that the difference of the relative refractive index difference of the concave layer and the adjacent layer is increased, the scattering of light can be avoided, the internal defect caused by the scattering of the dopant of the concave layer can be reduced, and the strength of the optical fibers prepared by the prefabricated member is further improved.
In some embodiments, the outer cladding comprises, from inside to outside, a transition layer and an outermost layer, the transition layer having a relative refractive index difference that is greater than the relative refractive index difference of the depressed layer and less than the relative refractive index difference of the outermost layer.
The embodiment of the application is provided with the transition layer, so that the dissipation of dopants can be further avoided, and the preparation strength of the optical fiber is improved.
In some embodiments, the relative refractive index difference at the maximum refractive index of the parabolic graded layer is between 0.017 and 0.022; the relative refractive index difference at the minimum refractive index of the parabolic graded layer is between 0.01 and 0.016; the relative refractive index difference at the minimum refractive index of the linear graded layer is between 0.002 and 0.006; the relative refractive index difference of the concave layer is between-0.01 and-0.003; the relative refractive index difference of the outermost layer is between 0.002 and 0.006.
The embodiment of the application can ensure the light gathering capability of the optical fiber by ensuring the relative refractive index difference within the range.
The embodiment of the application also provides a preparation method of the optical fiber, and provides the quartz prefabricated member; drawing the quartz prefabricated member to obtain a bare optical fiber; and coating the outer surface of the bare optical fiber to obtain the optical fiber with the coating layer.
The optical fiber is prepared by the quartz prefabricated member, the refractive index profile of the core layer and the concave layer with parabolic gradual change and linear gradual change is adopted by the quartz prefabricated member, so that the uniformity of the internal viscosity of the core layer can be improved, the matching property of the core layer and the cladding layer is improved, the internal stress in the optical fiber preparation process is reduced, the prepared optical fiber has stronger strength, in addition, in the refractive index profile, the relative refractive index difference of the concave layer is not more than zero, so that the difference of the relative refractive index difference of the concave layer and the adjacent layer is increased, the dissipation of light can be avoided, the internal defect caused by the dissipation of the dopant of the concave layer can be reduced, and the strength of the optical fiber prepared by the prefabricated member is improved.
In some embodiments, after the coating treatment is performed on the outer surface of the bare optical fiber, the optical fiber with a coating layer is further comprised of:
Placing the optical fiber with the coating layer in a vacuum environment with a preset vacuum degree and a preset temperature, and performing vacuum heat treatment; and after the vacuum heat treatment is carried out for a preset period of time, the optical fiber with the coating layer is taken out from the vacuum environment.
According to the embodiment of the application, through vacuum heat treatment, on one hand, the further curing of the optical fiber coating can be promoted, and through higher temperature treatment, the release of local stress generated by rapid curing of the coating is facilitated, so that the optical fiber strength is enhanced; on the other hand, the gas which influences the performance of the optical fiber, such as water vapor and the like, attached to the optical fiber can be rapidly and effectively removed by a hot temperature vacuumizing mode.
In some embodiments, after the drawing process is performed on the quartz preform, the method further includes: annealing the bare optical fiber; and sending the annealed bare optical fiber into a delayed heat preservation area for delayed heat preservation treatment.
According to the embodiment of the application, the influence of the surrounding environment on the bare optical fiber can be reduced by delaying the heat preservation area, meanwhile, the cooling speed of the optical fiber is reduced, and the internal structure of the bare optical fiber is stabilized, so that the strength of the manufactured optical fiber is further improved.
In some embodiments, the bare optical fiber is coated to provide a coated optical fiber comprising: coating the outer surface of the bare optical fiber, and curing to form a first coating layer; and coating the first coating layer, and curing to form a second coating layer to obtain the optical fiber with the coating layer.
The embodiment of the application is provided with the two coating layers and respectively carries out curing treatment, thereby being beneficial to improving the curing effect of the coating layers.
In some embodiments, the modulus of the first coating layer is 0.3-1MPa, the modulus of the second coating layer is 600-900MPa, and the thickness ratio of the first coating layer to the second coating layer is 0.8-1.3.
In some embodiments, the optical fiber preparation method is applied to an optical fiber preparation device in which a quartz glass tube is sleeved on a path of a bare optical fiber.
The embodiment of the application reduces the influence of the external environment on the preparation process of the optical fiber by using the quartz glass tube.
The embodiment of the application also provides an optical fiber, which is prepared by the optical fiber preparation method.
It will be appreciated that the optical fiber provided above is prepared by the method for preparing an optical fiber described above, and thus, the advantages achieved by the method can be referred to the advantages of the corresponding method provided above, and will not be described herein.
Drawings
Fig. 1 is a schematic cross-sectional view of a quartz preform according to an embodiment of the present application.
Fig. 2 is a schematic cross-sectional view of a quartz preform according to another embodiment of the present application.
FIG. 3 is a schematic view of a refractive index profile of a quartz preform according to an embodiment of the present application.
Fig. 4 is a flowchart illustrating steps of a method for manufacturing an optical fiber according to an embodiment of the present application.
Fig. 5 is a schematic structural diagram of an optical fiber preparation apparatus according to an embodiment of the present application.
Fig. 6 is a schematic structural diagram of a curing unit according to an embodiment of the application.
Description of the main reference signs
Parabolic graded layer 110
Linear graded layer 120
Recess layer 210
Outer cladding 220
Transition layer 221
Outermost layer 222
Steps 401, 402, 403, 404, 405, 406, 407
Stick feeding unit 1
Quartz preform 2
Graphite heating furnace 3
Annealing unit 4
Bare fiber diameter measuring unit 5
First applicator 61
First curing unit 71
Second applicator 62
Second curing unit 72
Coated optical fiber calliper unit 8-element
Positioning wheel 9
Optical fiber 10
Winding unit 11
Quartz glass tube 601
Curing oven 602
Curing light source 603
Reflection cover 604
Detailed Description
In order that the above-recited objects, features and advantages of the present application will be more clearly understood, a more particular description of the application will be rendered by reference to the appended drawings and appended detailed description. The embodiments of the present application and the features in the embodiments may be combined with each other without collision.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, and the described embodiments are merely some, rather than all, of the embodiments of the present application.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
Spatially relative terms, such as "upper" and "lower" may be used herein for simplicity of description to describe one element or feature's relationship to other element(s) or feature(s) illustrated in the figures. And spatially relative terms such as "upper," "upper" and "lower" may be used herein to describe a relationship of some of the features of an element relative to other features of the element in the figures. The device may be oriented differently (rotated 90 degrees or in other directions) and the spatially relative descriptors used herein interpreted accordingly.
In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the term "vertical" or the like is based on the orientation or positional relationship shown in the drawings, for convenience of description and simplification of the description, and is not indicative or implying that the apparatus or element in question has a specific orientation, is configured and operated in a specific orientation, and therefore, is not to be construed as limiting the present invention.
The following examples will provide those skilled in the art with a more complete understanding of the present invention and are not intended to limit the invention to the embodiments described.
Optical fibers are favored by those skilled in the art for their small size, light weight, and resistance to electromagnetic interference, and have developed very rapidly. Optical fibers are a critical component of a communication system, and their reliability directly affects the stability of the communication system.
The tensile strength of an optical fiber is one of the important indicators for evaluating the reliability of the optical fiber. With the trend of miniaturization of optical fiber size, how to ensure the mechanical strength of the optical fiber is also extremely important.
In some embodiments, the mechanical strength of the optical fiber may be improved by adjusting and controlling the process parameters during the fiber drawing process.
However, there is still room for improvement in the strength of the optical fiber produced by adjusting the process parameters during the drawing of the optical fiber.
In view of the foregoing, embodiments of the present application provide an optical fiber preform, an optical fiber manufacturing method, and an optical fiber, respectively, which can be used for manufacturing an optical fiber, aiming at improving the strength of the optical fiber.
Fig. 1 is a schematic cross-sectional view of a quartz preform according to an embodiment of the present application. The quartz preform is used for preparing an optical fiber.
The quartz preform includes a core layer and a cladding layer surrounding the core layer. The core layer has a relative refractive index difference that is greater than the cladding layer.
The relative refractive index difference may be calculated as follows:
Where Δ i is the relative refractive index difference at position i of the quartz preform profile, n i is the refractive index at position i, and n 0 is the refractive index of the silica material.
The core layer comprises from inside to outside: the parabolic graded layer 110 and the linear graded layer 120, i.e., the linear graded layer 120, surround the parabolic graded layer 110. The relative refractive index difference of the parabolic graded layer is parabolic in shape and the relative refractive index difference of the linear graded layer is linear in shape.
In some embodiments, the relative refractive index difference of the core is a continuous curve along the outward radius of the core, and the relative refractive index difference of the core may decrease gradually along the outward radius of the core. I.e. in the core, the closer to the core center the relative refractive index difference is.
The cladding includes: a depressed layer 210 and an outer cladding layer 220 surrounding the depressed layer 210. The relative refractive index difference of the depressed layer 210 is no greater than zero, and the relative refractive index difference of the depressed layer 210 is less than the relative refractive index difference of the outer cladding 220.
The dopant of the recess layer 210 may be fluorine or other dopants, which is not limited in the embodiment of the present application.
According to the quartz prefabricated member provided by the embodiment of the application, the refractive index profile of the core layer and the concave layer with parabolic gradual-linear gradual change is adopted, so that the uniformity of the viscosity inside the quartz can be improved, the matching property of the core layer and the cladding layer is improved, the internal stress in the preparation process of the optical fiber is reduced, the prepared optical fiber has stronger strength, in addition, in the refractive index profile, the relative refractive index difference of the concave layer is not more than zero, so that the difference of the relative refractive index difference of the concave layer and the adjacent layer is increased, the dissipation of light can be avoided, the internal defect caused by the dissipation of the dopant of the concave layer can be reduced, and the strength of the optical fiber prepared from the prefabricated member is improved.
In some embodiments, as shown with reference to FIG. 2, the outer cladding 220 may further include a transition layer 221 and an outermost layer 222 from the inside out. That is, the outer cladding 220 includes: a transition layer 221 surrounding the recess layer 210, and an outermost layer 222 surrounding the transition layer 221.
That is, in the present embodiment, the quartz preform may include a core layer and a cladding layer, the core layer including, in order from inside to outside: the parabolic graded layer 110 and the linear graded layer 120, the cladding layer comprises, in order from inside to outside: a recessed layer 210, a transition layer 221, and an outermost layer 222.
Wherein the relative refractive index difference of the transition layer 221 is greater than the relative refractive index difference of the depressed layer 210, and the relative refractive index difference of the transition layer 221 is less than the relative refractive index difference of the outermost layer 222.
The transition layer is arranged in the embodiment, so that dopant dissipation can be further avoided, and the preparation strength of the optical fiber is improved.
Referring to fig. 3, fig. 3 is a schematic diagram of a refractive index profile of a quartz preform according to an embodiment of the present application, where the schematic diagram reflects a trend of a relative refractive index difference in the quartz preform shown in fig. 2 with a radius.
In some embodiments, the relative refractive index difference Δ 1 at the maximum refractive index of the parabolic graded layer 110 may be between 0.017 and 0.022, for example, the relative refractive index difference Δ 1 at the maximum refractive index of the parabolic graded layer 110 may be 0.017, 0.019, 0.020, or 0.022, etc.
The relative refractive index difference Δ 2 at the minimum refractive index of the parabolic graded layer 110 may be between 0.01 and 0.016, for example, the relative refractive index difference Δ 2 at the minimum refractive index of the parabolic graded layer 110 may be 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, or 0.016, etc.
The relative refractive index difference Δ 3 at the minimum refractive index of the linear graded layer 120 may be between 0.002 and 0.006, for example, the relative refractive index difference Δ 1 at the minimum refractive index of the parabolic graded layer 110 may be 0.002, 0.004, 0.005, 0.006, or the like.
The relative refractive index difference Δ 4 of the depressed layer 210 may be between-0.01 to-0.003, for example, the relative refractive index difference Δ 4 of the depressed layer 210 may be-0.01, -0.008, -0.006, or-0.003, etc.
The relative refractive index difference Δ 5 of the transition layer 221 may be less than or equal to 0.
For example, in the case where the relative refractive index difference Δ 5 of the transition layer 221 is 0, the material of the transition layer 221 may be pure silicon dioxide.
The relative refractive index difference Δ 6 of the outermost layer 222 may be between 0.002 and 0.006, for example, the relative refractive index difference Δ 6 of the outermost layer 222 may be 0.002, 0.003, 0.004, 0.006, or the like.
The outermost layer may be doped with phosphorus pentoxide, but not limited thereto, and the specific dopant may be determined according to the performance requirements of the optical fiber and the relative refractive index difference of the outermost layer.
The relative refractive index difference of each layer is set in the above range, so that the light condensing performance of the prepared optical fiber can be ensured.
Further, the relative refractive index difference of the linear graded layer 120 may satisfy the following formula:
Δr＝b-aXr；
Wherein X r is the distance from the position r in the linear gradual change layer to the central zero point of the core layer, and b is a preset constant; b may have a value in the range of 0.011 to 0.02, e.g., b may have a value of 0.011, 0.013, 0.014, 0.016, 0.018, or 0.02; a is another predetermined constant, and the value range of a may be 5×10 -4～2*10-3, for example, a may be 5×10 -4、8*10-4、1*10-3, or 2×10 -3.
Further, the parabolic graded layer radius R1 may be between 0 and 1.7 μm, for example R1 may be equal to 0.5 μm, 0.8 μm, 1.5 μm, or 1.7 μm, etc.;
The core radius (i.e., core radius) R2 may be between 4.5 and 5 μm, for example, R2 may be equal to 4.51 μm, 4.55 μm, or 5 μm, etc.;
The radius R3 of the recessed layer is between 13 and 30 μm, for example R3 may be equal to 13 μm, 16 μm, 25 μm, or 30 μm etc.;
The radius R4 of the transition layer is between 16 and 55 μm, for example R4 may be equal to 16 μm, 20 μm, 30 μm, 45 μm, or 55 μm etc.;
And R3/R4 may be between 1.2 and 2.2, e.g., R3/R4 may be equal to 1.2, 1.4, 1.6, 2.0, or 2.2, etc.;
The outermost radius R5 may be 62.5 μm, but is not limited thereto.
The radii of the layers can be designed in the practical application process by combining the preparation requirement of the optical fiber, the application scene of the optical fiber, the performance requirement of the optical fiber and the like, and the embodiment of the application is not limited to the design.
The embodiment of the present application further provides a method for manufacturing an optical fiber, in which the quartz preform in the above embodiment is used for manufacturing the optical fiber, so that the relevant technical details of the above quartz preform embodiment are still valid in the present embodiment, and are not repeated herein, and accordingly, the implementation details of the present embodiment can also be applied to the previous embodiment.
The preparation method of the optical fiber comprises the following steps: providing the quartz prefabricated member in the embodiment, and carrying out wire drawing treatment on the quartz prefabricated member to obtain a bare optical fiber; and coating the outer surface of the bare optical fiber to obtain the optical fiber with the coating layer.
The quartz prefabricated member used in the preparation of the optical fiber adopts the refractive index profile of the core layer and the concave layer with parabolic gradual change and linear gradual change, so that the uniformity of the internal viscosity of the core layer can be improved, the matching property of the core layer and the cladding layer is improved, the internal stress in the preparation process of the optical fiber is reduced, and the prepared optical fiber has stronger strength.
In addition, in the refractive index profile, the relative refractive index difference of the concave layer is not more than zero, so that the difference of the relative refractive index difference of the concave layer and the adjacent layer is increased, not only can the escape of light be avoided, but also the internal defect caused by the escape of the dopant of the concave layer can be reduced, and the mechanical strength of the optical fiber manufactured by the prefabricated member is further improved.
For example, referring to fig. 4 and 5, fig. 4 is a flowchart illustrating steps of a method for preparing an optical fiber according to an embodiment of the application.
The optical fiber preparation device can realize each process step in the optical fiber preparation method. The optical fiber preparing apparatus may include: a rod feeding unit 1, a quartz preform 2, a graphite heating furnace 3, an annealing unit 4, a bare optical fiber diameter measuring unit 5, a first applicator 61, a first curing unit 71, a second applicator 62, a second curing unit 72, a coated optical fiber diameter measuring unit 8, a positioning wheel 9, an optical fiber 10, and a winding unit 11.
In some embodiments, the fiber preparation device is provided with a quartz glass tube that is sleeved over the path of the bare fiber. The present embodiment reduces the influence of the external environment on the optical fiber manufacturing process by using a quartz glass tube.
It will be appreciated that it is difficult to sleeve a silica glass tube at certain parts of the optical fibre preparation device, and that no silica glass tube may be provided, for example, at the bare fibre calliper unit 5, and that a silica glass tube is provided in the path that the fibre will take after passing through the bare fibre calliper unit 5.
The flow of the optical fiber preparation method provided in this embodiment is described below with reference to fig. 4 and 5, and the optical fiber preparation method includes:
In step 401, a quartz preform is provided.
For example, a quartz preform as provided in the above-described quartz preform embodiments may be prepared by modified chemical vapor deposition (MCVD, modified Chemical Vapor Deposition).
Embodiments of the present application may also be used to prepare quartz preforms by other methods, such as, but not limited to, plasma Chemical Vapor Deposition (PCVD).
At step 402, a quartz preform is surface treated.
Impurities, greasy dirt and microcracks on the surface of the quartz preform can be eliminated by surface treatment, so that the mechanical strength of the manufactured optical fiber can be further improved by surface treatment of the quartz preform.
The surface treatment method may include flame polishing, or an acid washing method, etc.
For example, the quartz preform may be acid etched using a mixture of hydrofluoric acid (HF) and nitric acid (HNO 3), wherein the mass ratio of hydrofluoric acid to nitric acid may be set between desired settings, for example, may be set at 1:1 to 1:5, the embodiment of the present application is not limited thereto.
The quartz prefabricated member can be cleaned by clear water after acid etching, the total duration of surface treatment can be 5-8 hours, and in the practical application process, the duration of surface treatment can be adjusted according to the surface impurities and other conditions of the quartz prefabricated member, and the embodiment of the application does not limit the duration of surface treatment.
After the surface treatment of the quartz preform, the moisture of the surface-treated quartz preform may be dried, and the process proceeds to step 403.
It will be appreciated that in the case where no surface defects such as impurities, oil stains, microcracks, etc. are present on the surface of the quartz preform, the surface treatment may not be performed on the quartz preform, i.e. whether the process in step 403 is performed or not may be selected according to actual requirements, which is not limited by the embodiment of the present application.
And 403, drawing the quartz prefabricated member to obtain the bare optical fiber.
For example, the quartz preform is transferred to a graphite heating furnace 3 and subjected to a melt drawing process. The diameter of the bare fiber may be set according to the use, performance, etc. of the prepared optical fiber, for example, the diameter of the bare fiber may be set between 124 μm and 126 μm.
And 404, annealing the bare optical fiber, and sending the annealed optical fiber into a delay heat preservation area for delay heat preservation.
The temperature of the delay heat preservation area can be set to be a fixed temperature or a gradient temperature within a certain range, so that the temperature of the optical fiber can be reduced in a gradient manner.
For example, the delayed thermal insulation region may be set to a gradient of 1200-600 ℃, but is not limited thereto.
In some embodiments, the optical fiber preparation device may further include a deferred thermal insulation area, where the deferred thermal insulation area is connected to the annealing unit, and after the bare optical fiber is obtained, the bare optical fiber after being pulled by gravity may pass through the annealing unit 4 to enter the deferred thermal insulation area.
The length of the delayed thermal insulation region may be set to be 4-6 m, for example, but not limited to, according to the actual application process.
According to the embodiment, the annealed optical fiber is sent into the delayed heat preservation area, so that the influence of the environment on the bare optical fiber can be reduced, the cooling speed of the optical fiber can be reduced, the internal structure of the bare optical fiber is stabilized, and the mechanical strength of the prepared optical fiber is improved.
In the practical application process, whether the annealed optical fiber is sent into the delayed heat preservation area can be set according to the mechanical strength requirement of the optical fiber.
And 405, coating the outer surface of the bare optical fiber to obtain the optical fiber with the coating layer.
In some embodiments, step 405 may include: firstly, coating treatment can be carried out on the outer surface of the bare optical fiber, and curing is carried out to form a first coating layer; then, a coating process is performed on the first coating layer, and curing is performed to form a second coating layer, thereby obtaining the optical fiber with the coating layer.
The coating layer material is a polymer having a refractive index larger than that of quartz glass and a low elastic modulus, and may be a thermosetting silicone resin liquid, an ultraviolet curable acrylate liquid, polyurethane, or the like, but is not limited thereto.
For example, the bare optical fiber is cooled, then is conveyed to an applicator for coating with resin coating, and is subjected to primary and secondary acrylic resin coating respectively by wet-dry coating, and is cured by ultraviolet light.
Compared with the optical fiber prepared by only performing the coating treatment once, the optical fiber prepared by the embodiment of the application is provided with two layers of coating layers, and is respectively coated, treated and cured, so that the curing effect is improved.
In some embodiments, the modulus of the first coating layer may be 0.3-1MPa, for example, the modulus may be 0.3MPa, 0.5MPa, 0.7MPa, or 1MPa, etc.; the modulus of the second coating layer may be 600 to 900MPa, for example, the modulus may be 600MPa, 700MPa, 900MPa, or the like; the ratio of the thickness of the first coating layer to the second coating layer may be 0.8 to 1.3, for example, the ratio of the thickness thereof may be 0.8, 1.0, 1.1, 1.2, 1.3, or the like.
If the first coating layer is too thick, the second coating layer is thinner, which may reduce the mechanical strength of the optical fiber, and if the first coating layer is thinner, the second coating layer is thicker, which may affect the bending performance of the optical fiber.
In some embodiments, the coating layer may be cured by a curing unit including a plurality of curing ovens 602, as shown with reference to fig. 6, the plurality of curing ovens 602 being arranged in a staggered manner.
Each curing oven may include a curing light 603, a reflective cap 604, and a fiber through-hole.
Further, in order to prevent the bare optical fiber from being influenced by the external environment, a quartz glass tube 601 may be provided on the path of the optical fiber to each curing oven, the quartz glass tube 601 may pass through the optical fiber through-hole, and the optical fiber may pass through the quartz glass tube 601 to be cured.
The curing light source 603 may be an ultraviolet light source, and because the curing light source is a 360 ° divergent light source, the reflection efficiency of the reflection cover is not 100%, which may cause uneven curing of the coating, thereby generating stress, and the staggered arrangement may make the intensity distribution of the light source more uniform, so as to cure the coating uniformly.
After obtaining the optical fiber having the coating layer, the cured optical fiber 10 may be drawn and collected by positioning the wheel 9 and the winding unit 11, and the optical fiber satisfying not less than a preset strain limit may be screened, for example, the preset strain limit may be set to 2%.
The optical fiber screened out has a strain limit greater than or equal to 2% may then be subjected to a vacuum heat treatment, i.e., step 406 is performed.
The method and the device can primarily remove unqualified optical fibers through strain limit screening, further improve the qualification rate of finished optical fibers, prevent unqualified optical fibers from entering a subsequent process, and save preparation cost.
In step 406, the coated optical fiber is placed in a vacuum environment having a predetermined vacuum and a predetermined temperature, and subjected to a vacuum heat treatment.
For example, the screened optical fiber is treated with a protective gas (e.g., deuterium gas), placed in a vacuum drying oven, a vacuum environment is established in the vacuum drying oven, and vacuum is applied until the vacuum drying oven reaches a preset vacuum level, e.g., 0.08MPa, and then a heater is turned on to bring the temperature of the vacuum drying oven to a preset temperature, e.g., 60 ℃.
In step 407, after performing the vacuum heat treatment for a preset period of time, the optical fiber having the coating layer is taken out from the vacuum environment.
The preset time period can be set according to requirements. For example, the screened optical fiber is placed in a vacuum drying oven for 12 hours, after the treatment is completed, the temperature in the vacuum drying oven is kept to be reduced to room temperature, the vacuum drying oven is restored to the vacuum degree of 0MPa, and the optical fiber is taken out.
Under the vacuum environment with preset vacuum degree and preset temperature, the optical fiber with the coating layer is subjected to vacuum heat treatment, so that on one hand, the further solidification of the optical fiber coating layer can be promoted, the service life of the optical fiber is further prolonged, the release of local stress generated by the rapid solidification of the coating layer is facilitated through heat treatment, and therefore the strength of the optical fiber is enhanced, and on the other hand, the gas influencing the performance of the optical fiber, such as water vapor attached to the optical fiber, can be rapidly and effectively removed through a thermal temperature vacuumizing mode, and the performance of the optical fiber is further improved.
Based on the steps, the optical fiber with the external diameter of 180-200 mu m and the tensile strength of more than or equal to 65N and high tensile strength can be prepared, and the strength of the optical fiber is not lower than the strength of the optical fiber corresponding to the optical fiber with the external diameter of 235-255 mu m, namely the optical fiber with the small external diameter and high mechanical strength can be prepared by the method.
It will be appreciated that in the process of manufacturing the optical fiber, whether to execute the step 402, the step of deferred thermal insulation treatment of the optical fiber, the steps 406 to 407, and the like may be selected according to the performance requirement of the optical fiber, the surface condition of the optical fiber preform, and the like, which is not limited in the embodiment of the present application.
The above-described optical fiber preparation process is described below by specific process parameters used in the optical fiber preparation process.
1. A quartz preform conforming to the refractive index profile structure of fig. 2 and 3 was prepared.
2. HF is adopted: the quartz prefabricated member is subjected to surface treatment for 6 hours according to the mass ratio of HNO 3 =1:4.
3. After the moisture on the surface of the quartz prefabricated member is dried, drawing treatment is carried out through optical fiber drawing equipment shown in fig. 5, and a bare optical fiber is obtained.
4. The bare optical fiber is annealed and then sent into a delay heat preservation area, the gradient temperature of the delay heat preservation area is set to 1200/1180/1140/1100/1050/1000/900/800/700/600 ℃, and the length of the delay heat preservation area is 4m.
5. And then the bare optical fiber passes through the quartz glass tube and the cooling tube and is coated by adopting a resin material, wherein the modulus of the first coating layer is 0.3MPa, and the modulus of the second coating layer is 600MPa.
6. The optical fiber having the coating layer is subjected to vacuum heat treatment.
Referring to table 1, the optical fibers of each example in table 1 were subjected to the above-described preparation processes in steps 1 to 5, and the vacuum heat treatment conditions of each example were different as follows:
Vacuum heat treatment conditions of example 1: no vacuum heat treatment was performed.
Vacuum heat treatment conditions of example 2: baking at 45 ℃ for 8 hours under the vacuum degree of 0.06 MPa.
Vacuum heat treatment conditions of example 3: baking at 60 deg.C under 0.06MPa for 8 hr.
Vacuum heat treatment conditions of example 4: and then heating to 60 ℃ and continuously heating for 6 hours.
Vacuum heat treatment conditions of example 5: no vacuum heat treatment was performed.
TABLE 1
From the table, the tensile strength of the optical fiber can be effectively improved by 7.82-11.23% by a vacuum heat treatment method, and the dynamic fatigue parameter of the optical fiber can be improved.
In addition, the attenuation coefficient of the optical fiber does not change obviously along with the change of the process parameters.
The optical fiber prepared by the embodiment of the application greatly reduces the outer diameter (compared with 245 μm) of the optical fiber, improves the strength of the optical fiber, increases the reliability of the optical fiber, reduces the risk of fiber interruption in the optical fiber laying process, and meets the application of fields with higher requirements on the strength of the optical fiber, such as sensing and the like.
Moreover, the refractive index profile of the core layer and the concave cladding layer which are linearly graded by adopting parabolas can effectively eliminate the problem of mismatching of viscosity between quartz and reduce the internal stress in the optical fiber production process; and meanwhile, the reasonable waveguide structure and doping can reduce quartz density fluctuation so as to alleviate structural defects in the optical fiber.
The embodiment of the application also provides an optical fiber, which is prepared by the embodiment provided by the optical fiber preparation method.
Finally, it should be noted that the above-mentioned embodiments are merely for illustrating the technical solution of the present application and not for limiting the same, and that it should be understood by those skilled in the art that the technical solution of the present application may be modified or substituted without departing from the spirit and scope of the technical solution of the present application.

Claims (10)

1. A silica preform for use in the manufacture of an optical fiber, said silica preform comprising a core layer and a cladding layer surrounding said core layer, said core layer having a relative refractive index difference greater than the relative refractive index difference of said cladding layer;
the core layer comprises from inside to outside: a parabolic graded layer and a linear graded layer;
The cladding comprises a depressed layer and an outer cladding surrounding the depressed layer, the depressed layer having a relative refractive index difference no greater than zero and the depressed layer having a relative refractive index difference less than the outer cladding;
Wherein the relative refractive index difference at the maximum refractive index of the parabolic graded layer is between 0.017 and 0.022;
the relative refractive index difference at the minimum refractive index of the parabolic graded layer is between 0.01 and 0.016;
the relative refractive index difference at the minimum refractive index of the linear graded layer is between 0.002 and 0.006;
The relative refractive index difference of the concave layer is between-0.01 and-0.003.
2. The quartz preform of claim 1, wherein the outer cladding comprises, from inside to outside, a transition layer and an outermost layer, the transition layer having a relative refractive index difference that is greater than a relative refractive index difference of the recess layer and less than a relative refractive index difference of the outermost layer.
3. The quartz preform of claim 2, wherein the outermost layer has a relative refractive index difference between 0.002 and 0.006.
4. A method of making an optical fiber comprising:
providing a quartz preform according to any of claims 1 to 3;
Drawing the quartz prefabricated member to obtain a bare optical fiber;
And coating the outer surface of the bare optical fiber to obtain the optical fiber with the coating layer.
5. The method for manufacturing an optical fiber according to claim 4, further comprising, after said coating the outer surface of said bare optical fiber to obtain an optical fiber having a coating layer:
Placing the optical fiber with the coating layer in a vacuum environment with a preset vacuum degree and a preset temperature, and performing vacuum heat treatment;
And taking out the optical fiber with the coating layer from the vacuum environment after carrying out vacuum heat treatment for a preset period of time.
6. The method of manufacturing an optical fiber according to claim 4, further comprising, after the drawing of the silica preform, the steps of:
annealing the bare optical fiber;
And sending the annealed bare optical fiber into a delayed heat preservation area for delayed heat preservation treatment.
7. The method for manufacturing an optical fiber according to claim 4, wherein the coating treatment of the bare optical fiber to obtain an optical fiber having a coating layer comprises:
Coating the outer surface of the bare optical fiber, and curing to form a first coating layer;
and coating the first coating layer, and curing to form a second coating layer to obtain the optical fiber with the coating layer.
8. The method of making an optical fiber according to claim 7, wherein the modulus of the first coating layer is 0.3 to 1MPa, the modulus of the second coating layer is 600 to 900MPa, and the thickness ratio of the first coating layer to the second coating layer is 0.8 to 1.3.
9. The optical fiber preparation method according to claim 4, wherein the optical fiber preparation method is applied to an optical fiber preparation device, and the optical fiber preparation device is provided with a quartz glass tube in a sleeved manner on a passing path of the bare optical fiber.
10. An optical fiber, characterized in that the optical fiber is produced according to the production method according to any one of claims 4 to 9.
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