CN110078366B - High-core-coated-concentricity optical fiber and preparation method thereof - Google Patents

High-core-coated-concentricity optical fiber and preparation method thereof Download PDF

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CN110078366B
CN110078366B CN201910181294.5A CN201910181294A CN110078366B CN 110078366 B CN110078366 B CN 110078366B CN 201910181294 A CN201910181294 A CN 201910181294A CN 110078366 B CN110078366 B CN 110078366B
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optical fiber
rod
core
layer
diameter
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CN110078366A (en
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莫思铭
李凡
纪明辉
邵珠峰
周莉
李想
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Jiangsu Yongding Fiber Technology Co ltd
Jiangsu Etern Co Ltd
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Jiangsu Yongding Fiber Technology Co ltd
Jiangsu Etern Co Ltd
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Priority to PCT/CN2019/114351 priority patent/WO2020181787A1/en
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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
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/01446—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
    • 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
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
    • 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
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
    • C03B37/01853—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
    • 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
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
    • C03B37/01861—Means for changing or stabilising the diameter or form of tubes or rods
    • 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
    • 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

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  • Manufacturing & Machinery (AREA)
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  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

The application relates to an optical fiber with high core-cladding concentricity and a preparation method thereof, wherein the preparation method of the optical fiber comprises the following steps: preparing a mother prefabricated core rod comprising an inner core layer, an outer core layer, an inner cladding layer and a sunken layer by using an MCVD (micro chemical vapor deposition) process, heating and stretching the mother prefabricated core rod to enable the bow of the stretched optical fiber core rod to be less than 0.8mm/m, preparing an outer cladding layer by using an OVD (over-voltage-reduction) process to obtain an optical fiber preform, and finally directly drawing the optical fiber preform or drawing the optical fiber preform to obtain the optical fiber. The diameter of the optical fiber preform rod prepared by the invention can reach 218mm, the fiber drawing length of a single preform rod can reach 3015km, the attenuation of the optical fiber at the wavelength of 1310nm is less than or equal to 0.311dB/km, the attenuation coefficient at the wavelength of 1383nm is less than or equal to 0.272dB/km, and the attenuation coefficient at the wavelength of 1550nm is less than or equal to 0.171 dB/km.

Description

High-core-coated-concentricity optical fiber and preparation method thereof
Technical Field
The application belongs to the technical field of optical fiber preparation, and particularly relates to an optical fiber with high core-coated concentricity and a preparation method thereof.
Background
The optical fiber is used as a medium for transmitting optical signals, and the optical fiber communication has the advantages of large communication capacity, long transmission distance, small signal crosstalk, good confidentiality, electromagnetic interference resistance, good transmission quality and the like, and plays a significant role in modern telecommunication networks. The optical fiber loss is one of the important indexes of the optical fiber performance, the optical fiber loss directly affects the distance of communication transmission or the distance interval of a relay station and the performance of communication equipment such as SDH (synchronous digital hierarchy), WDM (wavelength division multiplexing) and the like, and the system cost is mainly focused on controlling the loss, so that the optical fiber loss has great practical significance on whether the optical fiber can adapt to the development of future communication technology.
The difference of the concentricity of the fiber core/cladding (concentricity of the core and the cladding) of the optical fiber is one of the main reasons for the loss of the optical fiber, and the difference of the bow of the optical fiber preform can directly cause that the optical fiber drawn by the preform has larger error of the concentricity of the core and the cladding, but the bow and the diameter uniformity of the preform are difficult to control in the production process of the optical fiber preform.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the optical fiber with high core-clad concentricity and the preparation method thereof are provided for solving the technical problem of poor core-clad concentricity of the optical fiber in the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a preparation method of an optical fiber with high core-cladding concentricity comprises the following steps:
depositing an inner cladding layer, an outer core layer and an inner core layer on the inner wall of a quartz tube serving as a lower limit layer by using an MCVD (micro chemical vapor deposition) process to obtain a deposition tube, and performing melt shrinkage on the deposition tube to obtain a prefabricated core rod mother rod;
respectively butting two ends of a mother prefabricated core rod with an upper stretching rod and a lower stretching rod, enabling the mother prefabricated core rod to vertically penetrate through a stretching furnace, enabling the upper stretching rod and the lower stretching rod to synchronously rotate at the same rotating speed, enabling the stretching furnace to heat the mother prefabricated core rod from bottom to top, enabling the upper stretching rod to move upwards, and heating and stretching the mother prefabricated core rod, wherein the upward movement speed of the upper stretching rod is obtained by calculation before stretching according to the diameter required by the stretched core rod, the upward movement speed of the stretching furnace and the diameter of the mother prefabricated core rod, and the bow of the stretched prefabricated core rod is less than 0.8 mm/m;
depositing an outer cladding loose body outside the stretched prefabricated core rod by using an OVD (optical vapor deposition) process, and then sintering to obtain an optical fiber prefabricated rod;
the optical fiber perform is directly drawn to form the single mode optical fiber or drawn to form the single mode optical fiber with ultra-low loss and large effective area.
Preferably, the following conditions are satisfied during the heating and stretching process of the prefabricated core rod mother rod: v1＝k×V2×V3(D1 2-D2 2)/D1 2，V1For real-time moving speed of up-drawing draw bar, V2The rotation speed of the optical fiber core rod mother rod is V3For a predetermined upward movement speed of the stretching furnace, D1Is the diameter of the mother rod of the drawn section of the optical fiber core rod, D2K is 0.1-0.12 and V is the diameter required by the drawn core rod2Is 7-9mm/min, V330-40mm/min, and the temperature of the stretching furnace for heating the optical fiber core rod master rod is controlled at 2000-2500 ℃.
Preferably, the sintering treatment method comprises the following steps: and (3) enabling the optical fiber preform to be sintered to rotate in a sintering furnace, heating gas in the sintering furnace through the up-and-down movement of a heating coil outside the sintering furnace, and completing sintering, wherein the moving speed of the heating coil is preferably 5-10mm/min, and the rotation speed is preferably 3-6 rpm.
Preferably, the sintering treatment method comprises the following steps: firstly, introducing inert gas and chlorine gas into a sintering furnace, enabling the temperature in the sintering furnace to reach 600-800 ℃ at a heating rate of 15-25 mm/min, preserving heat for 2-3h, enabling the temperature in the sintering furnace to reach 1000-1200 ℃ at a heating rate of 30-45 mm/min, and preserving heat for 2-3 h; and closing chlorine, and only introducing inert gas into the sintering furnace to ensure that the temperature in the sintering furnace reaches 1300-1500 ℃ at the heating rate of 10-20 mm/min and the temperature is kept for 4-6 h.
Preferably, the MCVD process is utilized to heat the fluorine-doped quartz tube to 600-800 ℃ before the inner cladding layer, the outer core layer and the inner core layer are deposited on the inner wall of the fluorine-doped quartz tube serving as the lower limit layer, and fluorine-containing gas is introduced into the fluorine-doped quartz tube to carry out chemical etching on the inner surface of the quartz tube.
Preferably, the relative refractive index of the inner core layer is Δ n1The relative refractive index of the outer core layer is Deltan2The relative refractive index of the inner cladding is Deltan3The relative refractive index of the depressed layer is Deltan4The outer cladding is pure silicon dioxide, and the relative refractive index is as follows: Δ n1>Δn2>0>Δn3>Δn4。
Preferably, the relative refractive index Δ n of the inner core layer10.35-0.5%, relative refractive index delta n of outer core layer20.1% -0.25%, relative refractive index delta n of inner cladding3Is-0.05% -0.01%, and the relative refractive index delta n of the depressed layer4Is-0.25 to-0.1 percent.
Preferably, the inner core layer and the outer core layer are doped with B2O3The inner cladding layer is doped with P2O5-a silica glass layer of the F mixture, said sagging layer being a fluorine-doped silica glass layer.
Preferably, the ratio b/a of the diameter b of the outer core layer to the diameter a of the inner core layer is 1.5-2.5, the ratio c/a of the diameter c of the inner core layer to the diameter a of the inner core layer is 3-4, the ratio d/a of the diameter d of the sunken layer to the diameter a of the inner core layer is 7-9, and the ratio d/c of the diameter d of the optical fiber preform to the diameter c of the stretched preform rod is 2.5-3.5.
The invention also provides an optical fiber prepared by the method.
The invention has the beneficial effects that:
the invention uses MCVD technique to prepare a mother rod of a prefabricated core rod comprising an inner core layer, an outer core layer, an inner cladding layer and a sunken layer, then the mother rod of the prefabricated core rod is heated and stretched to ensure that the bow of the stretched optical fiber core rod is less than 0.8mm/m, then an outer cladding layer is prepared by OVD technique to obtain an optical fiber prefabricated rod, and finally the optical fiber prefabricated rod is directly drawn or drawn to obtain an optical fiber, wherein: (1) the stretching of the mother prefabricated core rod after the MCVD process step adopts a vertical upward stretching mode, and the upward moving speed of the upper stretching guide rod is calculated in advance according to the diameter required by the stretched core rod, the upward moving speed of the stretching furnace and the diameter of the mother optical fiber core rod at the stretched section before stretching, so that the bow degree and the diameter uniformity of the stretched prefabricated core rod are ensured; (2) the reasonable sintering process in the OVD process step not only effectively removes hydroxyl groups, but also ensures the uniformity of the diameter of the optical fiber preform, and finally reduces the core-clad concentricity error of the drawn optical fiber; (3) the refractive indexes, diameters and the like of the inner core layer, the outer core layer, the inner cladding layer and the depressed layer are further limited, so that the fiber drawing length of the optical fiber preform can be ensured, and the optical fiber loss is reduced. Finally, the diameter of the optical fiber preform rod prepared by the invention can reach 218mm, the fiber drawing length of a single preform rod can reach 3015km, the attenuation of the optical fiber at the wavelength of 1310nm is less than or equal to 0.311dB/km, the attenuation coefficient at the wavelength of 1383nm is less than or equal to 0.272dB/km, and the attenuation coefficient at the wavelength of 1550nm is less than or equal to 0.171 dB/km.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
Example 1
The embodiment provides a method for preparing an optical fiber with high core-cladding concentricity, which comprises the following steps:
heating the fluorine-doped quartz tube to 600 ℃, and introducing SiF into the fluorine-doped quartz tube4Chemically etching the inner surface of the quartz tube by using gas, depositing an inner cladding, an outer core layer and an inner core layer on the inner wall of the fluorine-doped quartz tube serving as a lower limit layer by using an MCVD (plasma chemical vapor deposition) process to obtain a deposition tube, and performing melt shrinkage on the deposition tube at 2300 ℃ to obtain a prefabricated core rod mother rod; the inner core layer and the outer core layer are doped with B2O3The silica glass layer of (2), the relative refractive index of the inner core layer being Δ n10.35% of the refractive index of the outer core layer20.1% of the total weight of the inner cladding, the inner cladding is doped with P2O5-a silica glass layer of the F mixture, the relative refractive index of the inner cladding Deltan3Is-0.05%, and the relative refractive index of the depressed layer is Deltan4Is-0.25%; the ratio b/a of the diameter b of the outer core layer to the diameter a of the inner core layer is 1.5, the ratio c/a of the diameter c of the inner cladding layer to the diameter a of the inner core layer is 3, and the ratio d/a of the diameter d of the sunken layer to the diameter a of the inner core layer is 7;
respectively butting the two ends of a mother prefabricated core rod with an upper stretching and drawing rod and a lower stretching and drawing rod, enabling the mother prefabricated core rod to vertically penetrate through a stretching furnace, enabling the upper stretching and drawing rod and the lower stretching and drawing rod to synchronously rotate at the same rotating speed, enabling the stretching furnace to heat the mother prefabricated core rod from bottom to top, enabling the upper stretching and drawing rod to move upwards, and heating the mother prefabricated core rodStretching, and satisfying the requirements in the process of heating and stretching the mother rod of the prefabricated core rod: v1＝k×V2×V3(D1 2-D2 2)/D1 2，V1For real-time moving speed of up-drawing draw bar, V2The rotation speed of the optical fiber core rod mother rod is V3For a predetermined upward movement speed of the stretching furnace, D1Is the diameter of the mother rod of the drawn section of the optical fiber core rod, D2The required diameter of the drawn mandrel, k is 0.1, V2Is 9mm/min, V3The heating temperature of the stretching furnace for heating the optical fiber core rod master rod is controlled to be 2000 ℃, and the bow of the prefabricated core rod after stretching is less than 0.8 mm/m;
depositing an outer cladding loose body outside the stretched prefabricated core rod by using an OVD (over-vacuum deposition) process, and then sintering to obtain an optical fiber prefabricated rod, wherein the outer cladding is pure silicon dioxide, and the ratio d/c of the diameter d of the optical fiber prefabricated rod to the diameter c of the stretched prefabricated core rod is 2.5; the sintering treatment method comprises the following steps: firstly, introducing helium and chlorine into a sintering furnace, enabling an optical fiber preform to be sintered to rotate in the sintering furnace at the speed of 3rpm, heating gas in the sintering furnace through the up-and-down movement of a heating coil outside the sintering furnace, enabling the moving speed of the heating coil to be 5mm/min, enabling the temperature in the sintering furnace to reach 600 ℃ at the temperature rising rate of 15mm/min, preserving heat for 3 hours, and enabling the temperature in the sintering furnace to reach 1000 ℃ at the temperature rising rate of 30mm/min, and preserving heat for 3 hours; and closing chlorine, introducing only helium into the sintering furnace, maintaining the autorotation of the optical fiber preform rod in the sintering furnace and the up-and-down movement of the heating coil, enabling the temperature in the sintering furnace to reach 1300 ℃ at the heating rate of 10mm/min, and preserving the heat for 6 hours.
Tests show that the diameter of the optical fiber preform reaches 198mm, the fiber drawing length of a single rod can reach 2815km, the attenuation of the drawn optical fiber at 1310nm is 0.302dB/km, the attenuation of the drawn optical fiber at 1383nm is 0.268dB/km, and the attenuation of the drawn optical fiber at 1550nm is 0.169 dB/km.
Example 2
The embodiment provides a method for preparing an optical fiber with high core-cladding concentricity, which comprises the following steps:
heating the fluorine-doped quartz tube to 800 ℃, and introducing CF into the fluorine-doped quartz tube4Chemically etching the inner surface of the quartz tube by using gas, depositing an inner cladding, an outer core layer and an inner core layer on the inner wall of the fluorine-doped quartz tube serving as a lower limit layer by using an MCVD (plasma chemical vapor deposition) process to obtain a deposition tube, and performing melt shrinkage on the deposition tube at 2300 ℃ to obtain a prefabricated core rod mother rod; the inner core layer and the outer core layer are doped with B2O3The silica glass layer of (2), the relative refractive index of the inner core layer being Δ n10.5%, relative refractive index of outer core layer Deltan20.25%, the inner cladding is doped with P2O5-a silica glass layer of the F mixture, the relative refractive index of the inner cladding Deltan3Is-0.01%, and the relative refractive index of the depressed layer is Deltan4Is-0.1%; the ratio b/a of the diameter b of the outer core layer to the diameter a of the inner core layer is 2.5, the ratio c/a of the diameter c of the inner cladding layer to the diameter a of the inner core layer is 4, and the ratio d/a of the diameter d of the sunken layer to the diameter a of the inner core layer is 9;
will prefabricate the mother stick both ends of plug and dock respectively and draw the stick with drawing down to make the mother stick of prefabricate plug vertically pass tensile stove, make and go up tensile draw the stick and draw down to draw the stick with the same rotational speed synchronous revolution, make tensile stove heat the mother stick from the bottom up of prefabricate plug, and make and go up tensile draw the stick rebound, heat tensile to the mother stick of prefabricate plug, heat tensile in-process satisfying the mother stick of prefabricate plug: v1＝k×V2×V3(D1 2-D2 2)/D1 2，V1For real-time moving speed of up-drawing draw bar, V2The rotation speed of the optical fiber core rod mother rod is V3For a predetermined upward movement speed of the stretching furnace, D1Is the diameter of the mother rod of the drawn section of the optical fiber core rod, D2The required diameter of the drawn mandrel, k is 0.12, V2Is 7mm/min, V3The heating temperature of the stretching furnace for heating the optical fiber core rod master rod is controlled to be 2500 ℃, and the bow of the prefabricated core rod after stretching is less than 0.8 mm/m;
depositing an outer cladding loose body outside the stretched prefabricated core rod by using an OVD (over-vacuum deposition) process, and then sintering to obtain an optical fiber prefabricated rod, wherein the outer cladding is pure silicon dioxide, and the ratio d/c of the diameter d of the optical fiber prefabricated rod to the diameter c of the stretched prefabricated core rod is 3.5; the sintering treatment method comprises the following steps: firstly, introducing helium and chlorine into a sintering furnace, enabling an optical fiber preform to be sintered to rotate in the sintering furnace at the speed of 6rpm, heating gas in the sintering furnace through the up-and-down movement of a heating coil outside the sintering furnace, enabling the moving speed of the heating coil to be 10mm/min, enabling the temperature in the sintering furnace to reach 800 ℃ at the temperature rising rate of 25mm/min, preserving heat for 2 hours, enabling the temperature in the sintering furnace to reach 1200 ℃ at the temperature rising rate of 45mm/min, and preserving heat for 3 hours; and closing chlorine, introducing only helium into the sintering furnace, maintaining the autorotation of the optical fiber preform rod in the sintering furnace and the up-and-down movement of the heating coil, enabling the temperature in the sintering furnace to reach 1500 ℃ at the heating rate of 20mm/min, and preserving the heat for 4 hours.
Tests show that the diameter of an optical fiber preform reaches 218mm, the fiber drawing length of a single rod can reach 3015km, the attenuation of the drawn optical fiber at 1310nm is 0.311dB/km, the attenuation of the drawn optical fiber at 1383nm is 0.272dB/km, and the attenuation of the drawn optical fiber at 1550nm is 0.171 dB/km.
Example 3
The embodiment provides a method for preparing an optical fiber with high core-cladding concentricity, which comprises the following steps:
heating the fluorine-doped quartz tube to 700 ℃, and introducing SiF into the fluorine-doped quartz tube4Chemically etching the inner surface of the quartz tube by using gas, depositing an inner cladding, an outer core layer and an inner core layer on the inner wall of the fluorine-doped quartz tube serving as a lower limit layer by using an MCVD (plasma chemical vapor deposition) process to obtain a deposition tube, and performing melt shrinkage on the deposition tube at 2300 ℃ to obtain a prefabricated core rod mother rod; the inner core layer and the outer core layer are doped with B2O3The silica glass layer of (2), the relative refractive index of the inner core layer being Δ n10.4%, relative refractive index of outer core layer Deltan20.2% of the total weight of the inner cladding, the inner cladding being doped with P2O5-a silica glass layer of the F mixture, the relative refractive index of the inner cladding Deltan3Is-0.07%, and the relative refractive index of the depressed layer is Deltan4Is-0.2%; the ratio b/a of the diameter b of the outer core layer to the diameter a of the inner core layer is 2, the ratio c/a of the diameter c of the inner cladding layer to the diameter a of the inner core layer is 3, and the ratio d/a of the diameter d of the sunken layer to the diameter a of the inner core layer is 8;
respectively aligning two ends of a mother rod of a prefabricated core rodConnect to draw the stick and draw the stick with drawing down to make the female stick of prefabricated plug vertical pass tensile stove, make on tensile draw the stick and draw down to draw the stick with the same rotational speed synchronous revolution, make tensile stove heat the female stick from the bottom up of prefabricated plug, and make and go up tensile and draw the stick rebound, heat tensile to the female stick of prefabricated plug, satisfy in the female stick heating tensile process of prefabricated plug: v1＝k×V2×V3(D1 2-D2 2)/D1 2，V1For real-time moving speed of up-drawing draw bar, V2The rotation speed of the optical fiber core rod mother rod is V3For a predetermined upward movement speed of the stretching furnace, D1Is the diameter of the mother rod of the drawn section of the optical fiber core rod, D2The required diameter of the drawn mandrel, k is 0.11, V2Is 8mm/min, V3The heating temperature of the stretching furnace for heating the optical fiber core rod master rod is controlled to be 2300 ℃, and the bending degree of the prefabricated core rod after stretching is less than 0.8 mm/m;
depositing an outer cladding loose body outside the stretched prefabricated core rod by using an OVD (over-vacuum deposition) process, and then sintering to obtain an optical fiber prefabricated rod, wherein the outer cladding is pure silicon dioxide, and the ratio d/c of the diameter d of the optical fiber prefabricated rod to the diameter c of the stretched prefabricated core rod is 3; the sintering treatment method comprises the following steps: firstly, introducing helium and chlorine into a sintering furnace, enabling an optical fiber preform to be sintered to rotate in the sintering furnace at the speed of 5rpm, heating gas in the sintering furnace through the up-and-down movement of a heating coil outside the sintering furnace, enabling the moving speed of the heating coil to be 5-10mm/min, enabling the temperature in the sintering furnace to reach 700 ℃ at the temperature rising rate of 20mm/min, preserving heat for 2.5 hours, enabling the temperature in the sintering furnace to reach 1100 ℃ at the temperature rising rate of 40mm/min, and preserving heat for 2.5 hours; and closing chlorine, introducing only helium into the sintering furnace, maintaining the autorotation of the optical fiber preform rod in the sintering furnace and the up-and-down movement of the heating coil, enabling the temperature in the sintering furnace to reach 1400 ℃ at the temperature rise rate of 15mm/min, and preserving the heat for 5 hours.
Tests show that the diameter of an optical fiber preform reaches 212mm, the fiber drawing length of a single rod can reach 2951km, the attenuation of the drawn optical fiber at 1310nm is 0.295dB/km, the attenuation of the drawn optical fiber at 1383nm is 0.251dB/km, and the attenuation of the drawn optical fiber at 1550nm is 0.165 dB/km.
In light of the foregoing description of the preferred embodiments according to the present application, it is to be understood that various changes and modifications may be made without departing from the spirit and scope of the invention. The technical scope of the present application is not limited to the contents of the specification, and must be determined according to the scope of the claims.

Claims (9)

1. A preparation method of an optical fiber with high core-cladding concentricity is characterized by comprising the following steps:
depositing an inner cladding layer, an outer core layer and an inner core layer on the inner wall of a quartz tube serving as a sinking layer by using an MCVD (micro chemical vapor deposition) process to obtain a deposition tube, and performing melt shrinkage on the deposition tube to obtain a prefabricated core rod master rod; the relative refractive indexes of the inner core layer, the outer core layer, the inner cladding layer and the depressed layer are delta n in sequence1、Δn2、Δn3、Δn4The relative refractive index is: Δ n1>Δn2>0>Δn3>Δn4；
Respectively butting two ends of a mother prefabricated core rod with an upper stretching rod and a lower stretching rod, enabling the mother prefabricated core rod to vertically penetrate through a stretching furnace, enabling the upper stretching rod and the lower stretching rod to synchronously rotate at the same rotating speed, enabling the stretching furnace to heat the mother prefabricated core rod from bottom to top, enabling the upper stretching rod to move upwards, and heating and stretching the mother prefabricated core rod, wherein the upward movement speed of the upper stretching rod is obtained by calculation before stretching according to the diameter required by the stretched core rod, the upward movement speed of the stretching furnace and the diameter of the mother prefabricated core rod, and the bow of the stretched prefabricated core rod is less than 0.8 mm/m; satisfies the following requirements in the heating and stretching process of the mother rod of the prefabricated core rod: v1＝k×V2×V3(D1 2-D2 2)/D1 2，V1For real-time moving speed of up-drawing draw bar, V2The rotation speed of the optical fiber core rod mother rod is V3For a predetermined upward movement speed of the stretching furnace, D1Is the diameter of the mother rod of the drawn section of the optical fiber core rod, D2K is 0.1-0.12 and V is the diameter required by the drawn core rod2Is 7-9mm/min, V3Is 30-40 mm/min;
depositing a pure silica outer cladding loose body outside the stretched prefabricated core rod by using an OVD (optical vapor deposition) process, and then sintering to obtain an optical fiber prefabricated rod;
the optical fiber perform is directly drawn to form the single mode optical fiber or drawn to form the single mode optical fiber with ultra-low loss and large effective area.
2. The method for preparing an optical fiber with high concentricity of core and cladding as claimed in claim 1, wherein the temperature of the core rod of the optical fiber heated by the drawing furnace is controlled to 2000-2500 ℃.
3. The method for preparing an optical fiber with high core-clad concentricity according to claim 1 or 2, wherein the sintering treatment method comprises the following steps: and (3) enabling the optical fiber preform to be sintered to rotate in a sintering furnace, heating gas in the sintering furnace through the up-and-down movement of a heating coil outside the sintering furnace, and completing sintering, wherein the moving speed of the heating coil is preferably 5-10mm/min, and the rotation speed is preferably 3-6 rpm.
4. The method for preparing an optical fiber with high core-clad concentricity according to claim 3, wherein the sintering treatment method comprises the following steps: firstly, introducing inert gas and chlorine gas into a sintering furnace, enabling the temperature in the sintering furnace to reach 600-800 ℃ at a heating rate of 15-25 mm/min, preserving heat for 2-3h, enabling the temperature in the sintering furnace to reach 1000-1200 ℃ at a heating rate of 30-45 mm/min, and preserving heat for 2-3 h; and closing chlorine, and only introducing inert gas into the sintering furnace to ensure that the temperature in the sintering furnace reaches 1300-1500 ℃ at the heating rate of 10-20 mm/min and the temperature is kept for 4-6 h.
5. The method for preparing an optical fiber with high core-cladding concentricity as claimed in claim 1 or 2, wherein the fluorine-doped quartz tube is heated to 800 ℃ and fluorine-containing gas is introduced into the fluorine-doped quartz tube to chemically etch the inner surface of the quartz tube before the inner cladding layer, the outer core layer and the inner core layer are deposited on the inner wall of the fluorine-doped quartz tube as the depressed layer by MCVD process.
6. The method for manufacturing an optical fiber with high core-clad concentricity according to claim 1 or 2, wherein the relative refractive index Δ n of the inner core layer10.35-0.5%, relative refractive index delta n of outer core layer20.1% -0.25%, relative refractive index delta n of inner cladding3Is-0.05% -0.01%, and the relative refractive index delta n of the depressed layer4Is-0.25 to-0.1 percent.
7. The method of making a high-core-envelope concentricity optical fiber as claimed in claim 1 or 2, wherein the inner and outer core layers are doped with B2O3The inner cladding layer is doped with P2O5-a silica glass layer of the F mixture, said sagging layer being a fluorine-doped silica glass layer.
8. The method for preparing an optical fiber with high concentricity of a core package according to claim 1 or 2, wherein the ratio b/a of the diameter b of the outer core layer to the diameter a of the inner core layer is 1.5 to 2.5, the ratio c/a of the diameter c of the inner core layer to the diameter a of the inner core layer is 3 to 4, the ratio d/a of the diameter d of the depressed layer to the diameter a of the inner core layer is 7 to 9, and the ratio d/c of the diameter d of the optical fiber preform to the diameter c of the preform core rod after drawing is 2.5 to 3.5.
9. An optical fiber prepared by the method of any one of claims 1-8.
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