CN115072986A - Preparation method for improving refractive index center deviation of optical fiber preform - Google Patents

Preparation method for improving refractive index center deviation of optical fiber preform Download PDF

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Publication number
CN115072986A
CN115072986A CN202210677969.7A CN202210677969A CN115072986A CN 115072986 A CN115072986 A CN 115072986A CN 202210677969 A CN202210677969 A CN 202210677969A CN 115072986 A CN115072986 A CN 115072986A
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rare earth
core layer
optical fiber
refractive index
heating
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代江云
张立华
刘念
李芳�
高聪
沈昌乐
贺红磊
吕嘉坤
姜蕾
王建军
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Laser Fusion Research Center China Academy of Engineering Physics
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Laser Fusion Research Center China Academy of Engineering Physics
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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]
    • C03B37/018—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
    • C03B37/01861—Means for changing or stabilising the diameter or form of tubes or rods
    • 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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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

The invention provides a preparation method for improving the refractive index center offset of an optical fiber preform, which comprises the steps of depositing a plurality of rare earth-containing core layers, depositing a rare earth-free core layer, fusing the inner hole size of a quartz tube to 1.5-4 mm, introducing etching gas to remove the rare earth-free core layer on line, and finally fusing to form the solid preform. Compared with an etching method for improving the deviation of the refractive index center of the prefabricated rod and a preparation method for improving the deviation of the refractive index center of the prefabricated rod 2 O 5 The volatilization inhibition method has the advantages that the refractive index distribution of the optical fiber preform prepared by the method is flatter, pollution is not introduced or crystallization is not induced, the controllability of the method is stronger, and the difficulty of process optimization is reduced.

Description

Preparation method for improving refractive index center deviation of optical fiber preform
Technical Field
The invention relates to the technical field of optical fiber preforms, in particular to a preparation method for improving the center deviation of the refractive index of an optical fiber preform.
Background
Compared with the traditional solid laser, the fiber laser has many excellent properties, particularly has good beam quality and stability under the high-power operation condition, and plays an extremely important role in the fields of industrial processing, national defense safety, basic scientific research and the like. With the continuous deepening of the application field of the optical fiber laser, higher requirements are put forward on the output power of the ytterbium-doped optical fiber laser, and the improvement of the power of the optical fiber laser is directly related to the optimization of the performance of the optical fiber laser material. The performance of the ytterbium-doped optical fiber is directly determined to a great extent by the ytterbium-doped optical fiber prefabricated rod.
The method for producing the passive quartz optical fiber preform is not more than ten, but the current batch preparation technology is mainly four: (1) modified Chemical vapor Deposition (MCVD: Modified Chemical vapor Deposition); (2) vapor Axial Deposition (VAD: vapor phase Axial Deposition); (3) outside vapor Deposition (OVD: Outside Chemical vapor Deposition); (4) (microwave) Plasma activated Chemical vapor Deposition (PCVD). The above methods are all vapor deposition methods, and these four methods can also be classified into in-tube deposition process/in-tube method, and out-of-tube deposition process/out-of-tube method.
The MCVD process was developed in 1974 by Machesney et al, Bell laboratories, AT & T, Inc., USA, which was adopted by lucent, et al. The MCVD process is a vapor deposition process that takes place in a high purity quartz glass tube with an oxyhydrogen flame source. The chemical reaction mechanism of the MCVD process is high temperature oxidation. The MCVD process consists of two process steps, deposition and rod formation. The deposition is to obtain the optical fiber core refractive index distribution required by design, and the rod forming is to melt and shrink the deposited hollow high-purity quartz glass tube into a solid optical fiber preform core rod. MCVD has high deposition efficiency, simple equipment, low price and easy control of refractive index, and can manufacture profile optical fibers with more complex refractive index structures.
The preparation of the rare earth-doped silica optical fiber preform based on MCVD has a solution doping method and a gas phase doping method. The solution doping method is that firstly a loose layer is deposited on the inner wall of a high-purity quartz tube, then the loose layer is soaked in a solution containing rare earth ions, then chlorine is adopted for dehydration and drying treatment, and a solid preform is finally obtained after sintering and pipe shrinking. The gas phase doping method refers to that all materials enter a reaction area of a quartz tube in a carrier gas carrying mode. Preparation of phosphorus pentoxide (P) by gas phase doping or solution doping 2 O 5 ) The optical fiber preform with volatile component is subjected to high temperature collapsing process, and the volatile component volatilizes on the free surface to initiate other optical fiber material components (such as rare earth oxide Re) 2 O 3 Aluminum oxide Al 2 O 3 ) And thus the center of the refractive index of the preform shifts.
The common preparation method for the ytterbium-doped silica optical fiber preform at present is an improved vapor deposition (MCVD) combined solution doping method or a vapor doping method. When the two methods are subjected to a collapsing process, the core layer deposited on the inner wall of the quartz tube needs to bear higher collapsing temperature (2000-2200 ℃) for the quartz tube containing P 2 O 5 For the rare earth doped optical fiber preform (such as phosphor-silicon, aluminum-phosphor-silicon optical fiber components), the volatile component will volatilize on the free surface, causing the shift of the center of the refractive index of the rare earth doped optical fiber preform. The uncontrolled shift of the index center adversely affects the control of the fiber waveguide structure and the reduction of the fiber transmission loss.
The invention patent publication No. CN 1295039A, entitled method for preparing an optical fiber preform, discloses a method for preparing an optical fiber preform, which can eliminate or significantly reduce undesirable refractive index variations in the central portion of an optical fiber, comprising: a first sintering step, an etching step and a second sintering step. This is achieved byThe method can only etch the fiber material component without rare earth in the core region, but for the active fiber with the core region containing rare earth oxide, the etching gas (C) is used 2 F 6 、C 2 F 3 Cl 3 、SF 6 ) The rare earth oxide can not react with the rare earth oxide (see organic Materials,2018,54(3),276-282), so when the method is used for removing the center shift of the refractive index of the rare earth-doped optical fiber, serious crystallization can be caused due to the residue of the rare earth oxide, and the application of the method is limited.
The invention patent publication CN 109399910A "preparation method of large core diameter optical fiber preform and optical fiber", which reports migration of doped ions, P 2 O 5 The volatilization may cause the uneven refractive index distribution of the preform, and the invention adjusts Yb (thd) in the deposition layer 3 、Al(acac) 3 、POCl 3 Or SiF 4 The flow rate of the components is adjusted to ensure that the prepared large-core-diameter preform has uniform refractive index distribution. The method carries out targeted compensation on the component flow of the last layer, but the final refractive index center distribution still has large depressions.
Accordingly, those skilled in the art have been made to develop a preparation method for improving the center shift of the refractive index of an optical fiber preform to solve the above-mentioned disadvantages of the prior art.
Disclosure of Invention
In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is the refractive index center shift problem occurring when the improved vapor deposition method disclosed in the prior art is used for manufacturing an optical fiber preform.
In order to achieve the purpose, the invention provides a preparation method for improving the center deviation of the refractive index of an optical fiber preform, which comprises the steps of firstly depositing a plurality of core layers containing rare earth, then depositing the core layers containing no rare earth, then firstly melting and shrinking the inner hole of a quartz tube to 1.5-4 mm, introducing etching gas to remove the core layers containing no rare earth on line, and finally melting and shrinking the core layers into the solid preform for the second time;
further, the preparation method for improving the refractive index center shift of the optical fiber preform comprises the following steps:
step 1, welding a cleaned quartz gas inlet pipe 1, a cleaned quartz deposition pipe 2 and a cleaned quartz tail gas pipe 3 to an MCVD lathe; after the three sections of quartz tubes are welded, carrying out heat treatment on the quartz tubes to release the internal stress of the welding points;
step 2, heating MCVD chemical reaction material SiCl 4 With POCl 3 Bubbler, Yb chelate with AlCl 3 A bubbler and corresponding transport lines;
step 3, installing the soot wiper and sealing, then heating the flame, moving the pulley, and introducing etching gas to remove grease and dust on the inner wall of the quartz tube;
step 4, changing the flame temperature and the pulley speed, rotating the pipeline, and sequentially depositing a rare earth-containing core layer in a plurality of layers;
step 5, depositing a core layer with an inner core not containing rare earth on the basis of the step 4;
step 6, performing primary melting and shrinking on the quartz tube obtained in the step 5, changing the flame temperature and the pulley speed, and melting and shrinking until the diameter of a central hole is 1.5-4 mm;
step 7, introducing etching gas into the quartz tube with the center hole of 1.5-4 mm obtained in the step 6, heating and etching the inner wall of the quartz tube to perform on-line removal of the core layer without rare earth;
step 8, performing secondary fusion on the hollow tube obtained in the step 7 after the rare earth-free core layer is removed to obtain a solid rod, and finishing the preparation of the optical fiber preform;
further, in the step 1, the heating mode is oxyhydrogen flame heating;
further, in the step 1, the heat treatment temperature is 1800-2000 ℃;
further, in the step 2, the SiCl is adopted 4 With POCl 3 Heating to 25-40 ℃ by a bubbler;
further, in the step 2, the Yb chelate complex and AlCl are mixed 3 Heating the mixture to 120-160 ℃ by a bubbler;
further, in the step 2, the corresponding conveying pipelines are heated to 220-260 ℃;
further, in the step 3, the heating temperature is 1900-2100 ℃;
further, in the step 3, the moving speed of the pulley is 100-150 mm/min;
further, in step 3, the etching gas is SF 6 、C 2 F 6 ；
Further, in the step 4, the heating temperature is 1400-2000 ℃;
further, in the step 4, the moving speed of the pulley is 100-150 mm/min;
further, in the step 4, the rotation speed of the pipeline is 20-40 revolutions per minute;
further, in the step 4, the rare earth-containing core layer is 2-15 layers;
further, in the step 4, each layer of the core layer containing rare earth comprises SiCl 4 、AlCl 3 、POCl 3 、Ce(thd) 3 、Yb(thd) 3 ；
Further, in the step 5, the core layer containing no rare earth comprises SiCl 4 、AlCl 3 、POCl 3 ；
Further, in the step 6, the heating temperature is 2050-2150 ℃;
further, in the step 6, the moving speed of the pulley is 20-60 mm/min;
further, in the step 7, the etching gas is C 2 F 6 、O 2 、SF 6 、C 2 F 3 Cl 3 ；
Further, in the step 7, the heating temperature is 1900-2200 degrees;
further, in the step 7, the number of times of etching the inner wall of the quartz tube is 1-6 times;
further, in the step 8, the heating temperature is 2150-2200 ℃;
further, in the step 8, the moving speed of the pulley is 5-40 mm/min;
in a specific embodiment of the present invention, in the step 1, the heat treatment temperature is 1800 ℃;
in another embodiment of the present invention, in the step 1, the heat treatment temperature is 1900 ℃;
in another embodiment of the present invention, in the step 1, the heat treatment temperature is 2000 ℃;
in a specific embodiment of the present invention, in the step 2, the SiCl is 4 With POCl 3 Heating to 25 ℃ by a bubbler;
in another embodiment of the present invention, in the step 2, the SiCl is 4 With POCl 3 Heating to 30 ℃ by a bubbler;
in another embodiment of the present invention, in the step 2, the SiCl is 4 With POCl 3 Heating to 40 ℃ by a bubbler;
in a specific embodiment of the present invention, in step 2, the Yb chelate is reacted with AlCl 3 Heating the bubbler to 120 ℃;
in another embodiment of the present invention, in step 2, the Yb chelate is reacted with AlCl 3 Heating to 130 ℃ by a bubbler;
in another embodiment of the present invention, in step 2, the Yb chelate is reacted with AlCl 3 Heating to 160 ℃ by a bubbler;
in a specific embodiment of the present invention, in step 2, the respective transport lines are heated to 220 ℃;
in another embodiment of the present invention, in step 2, the respective transport lines are heated to 240 ℃;
in another embodiment of the present invention, in step 2, the respective transport lines are heated to 260 ℃;
in an embodiment of the present invention, in the step 3, the etching gas is SF 6 ；
In a specific embodiment of the present invention, in the step 3, the heating temperature is 1900 ℃;
in another embodiment of the present invention, in the step 3, the heating temperature is 2000 ℃;
in another embodiment of the present invention, in the step 3, the heating temperature is 2100 ℃;
in a specific embodiment of the present invention, in the step 3, the moving speed of the pulley is 100 mm/min;
in another embodiment of the present invention, in the step 3, the moving speed of the pulley is 130 mm/min;
in another embodiment of the present invention, in the step 3, the moving speed of the trolley is 150 mm/min;
in a specific embodiment of the present invention, in the step 4, the heating temperature is 1400 ℃;
in another embodiment of the present invention, in the step 4, the heating temperature is 1700 ℃;
in another embodiment of the present invention, in the step 4, the heating temperature is 2000 ℃;
in a specific embodiment of the present invention, in the step 4, the moving speed of the pulley is 100 mm/min;
in another embodiment of the present invention, in the step 4, the moving speed of the pulley is 130 mm/min;
in another embodiment of the present invention, in the step 4, the moving speed of the trolley is 150 mm/min;
in a specific embodiment of the present invention, in the step 4, the rotation speed of the pipeline is 20 rpm;
in another embodiment of the present invention, in the step 4, the rotation speed of the pipeline is 30 r/min;
in another embodiment of the present invention, in the step 4, the rotation speed of the pipeline is 40 rpm;
in a specific embodiment of the present invention, in the step 4, the rare earth-containing core layer is 5 layers;
in a specific embodiment of the present invention, in the step 4, the gas flow rate in each layer of the core layer containing rare earth is SiCl 4 Is 150sccm and AlCl 3 Is 90sccm, POCl 3 Is 60sccm, Yb (thd) 3 Is 150 sccm;
in an embodiment of the present invention, in the step 5, the gas flow rate in the core layer without rare earth is SiCl 4 Is 50sccm and AlCl 3 Is 30sccm, POCl 3 Is 65 sccm;
in a specific embodiment of the present invention, in the step 6, the heating temperature is 2050 ℃;
in another embodiment of the present invention, in the step 6, the heating temperature is 2100 ℃;
in another embodiment of the present invention, in the step 6, the heating temperature is 2150 ℃;
in a specific embodiment of the present invention, in the step 6, the moving speed of the pulley is 20 mm/min;
in another embodiment of the present invention, in the step 6, the moving speed of the trolley is 40 mm/min;
in another embodiment of the present invention, in the step 6, the moving speed of the trolley is 60 mm/min;
in a specific embodiment of the present invention, in the step 6, the first time of melting and shrinking is performed until the diameter of the central hole is 1.5 mm;
in another embodiment of the present invention, in the step 6, the first time of the melting and shrinking is performed until the diameter of the central hole is 3 mm;
in another embodiment of the present invention, in the step 6, the first time of the melting and shrinking is performed until the diameter of the central hole is 4 mm;
in an embodiment of the present invention, in the step 7, the etching gas is C 2 F 6 、O 2 ；
In a specific embodiment of the present invention, in the step 7, the C 2 F 6 The input amount is 100 ml/min;
in a specific embodiment of the present invention, in the step 7, the O is 2 The input amount is 300 ml/min;
in a specific embodiment of the present invention, in the step 7, the heating temperature is 1900 ℃;
in another embodiment of the present invention, in the step 7, the heating temperature is 2150 ℃;
in another embodiment of the present invention, in the step 7, the heating temperature is 2180 ℃;
in a specific embodiment of the present invention, in step 7, the number of times of etching the inner wall of the quartz tube is 1;
in another specific embodiment of the present invention, in the step 7, the number of times of etching the inner wall of the quartz tube is 3;
in another specific embodiment of the present invention, in the step 7, the number of times of etching the inner wall of the quartz tube is 6 times;
in a specific embodiment of the present invention, in the step 8, the heating temperature is 2150 ℃;
in another embodiment of the present invention, in the step 8, the heating temperature is 2180 ℃;
in another embodiment of the present invention, in the step 8, the heating temperature is 2200 ℃;
in a specific embodiment of the present invention, in the step 8, the moving speed of the pulley is 5 mm/min;
in another embodiment of the present invention, in the step 8, the moving speed of the pulley is 10 mm/min;
in another embodiment of the present invention, in the step 8, the moving speed of the pulley is 20 mm/min;
by adopting the scheme, the preparation method for improving the center deviation of the refractive index of the optical fiber preform has the following advantages:
(1) compared with the method adopting an etching method and P 2 O 5 The method for improving the center deviation of the refractive index of the prefabricated rod by a volatilization inhibition method has the advantages that all components of the prefabricated rod prepared by the method are more uniformly distributed in the radial direction, and the center depression of the refractive index is smaller; and no pollution is introduced or crystallization is caused;
(2) depositing a core layer without rare earth oxide on the innermost layer, so that the on-line etching method can be applied to the elimination of the center deviation of the refractive index of the rare earth-doped optical fiber preform;
in summary, the manufacturing method for improving the refractive index center shift of the optical fiber preform disclosed by the invention is compared with the etching method for improving the refractive index center shift of the preform and the P 2 O 5 The volatilization inhibition method has the advantages that the refractive index distribution of the optical fiber preform prepared by the method is flatter, pollution is not introduced or crystallization is not induced, the controllability of the method is stronger, and the difficulty of process optimization is reduced.
The conception, the specific technical solutions and the technical effects produced by the present invention will be further described with reference to the following detailed description so as to fully understand the objects, the features and the effects of the present invention.
Drawings
FIG. 1 is a schematic structural diagram of a manufacturing apparatus for improving the refractive index center shift of an optical fiber preform according to the present invention;
FIG. 2 is a radial refractive index profile of a preform according to the development process for the center shift phenomenon of the refractive index of the preform in example 1;
FIG. 3 is a radial refractive index profile of the preform of example 2;
FIG. 4 is a schematic cross-sectional view of a preform;
in the figure, 1, a quartz gas inlet pipe; 2. a quartz deposition tube; 3. a quartz tail gas pipe; 4. an oxyhydrogen flame; 5. a flow regulating valve 1; 6. SiCl 4 With POCl 3 A bubbler; 7. a breather pipe 1; 8. yb chelate and AlCl 3 A bubbler; 9. a breather pipe 2; 10. etching gas; 11. a flow regulating valve 2; 12. a flow rate regulating valve 3; 13. a transport line; 14. a soot scraper; 15. depositing a base layer; 16. 5 layers of core layer containing rare earth; 17. does not contain a rare earth core layer.
Detailed Description
The following describes several preferred embodiments of the present invention to make the technical contents thereof clearer and easier to understand. The invention may be embodied in many different forms of embodiments, which are intended to be illustrative only, and the scope of the invention is not intended to be limited to the embodiments shown herein.
If there is an experimental method not specified specific conditions, it is usually carried out according to conventional conditions, such as the relevant instructions or manuals.
Example 1 preparation method for improving center shift of refractive index of optical fiber preform
The preparation device is adopted to manufacture the optical fiber preform as shown in figure 1; the specific operation is as follows:
step 1, respectively welding and connecting a cleaned quartz gas inlet pipe 1, a quartz deposition pipe 2 and a quartz tail gas pipe 3 end to an MCVD lathe; after the three sections of quartz tubes are connected, carrying out heat treatment on the quartz tubes, wherein the heat treatment temperature is 1800 ℃, and releasing the internal stress of welding points;
step 2, adding SiCl serving as MCVD chemical reaction material 4 With POCl 3 The bubbler 6 is heated to 25 ℃, and the Yb chelate and the AlCl are mixed 3 The bubbler 8 is heated to 120 ℃ and the corresponding transport line 13 is heated to 220 ℃;
step 3, installing the soot wiper 14 and sealing, heating the flame at 1900 ℃, moving the pulley at 100mm/min, and introducing SF 6 Removing grease and dust on the inner wall of the quartz tube by using gas 10;
step 4, sequentially depositing a rare earth-containing core layer in multiple layers, dividing a rare earth-containing gas material into 5 layers, sequentially introducing the layers into a quartz tube to start deposition of the core layer, wherein the gas flow of each layer is SiCl 4 Is 150sccm and AlCl 3 Is 90sccm, POCl 3 Is 60sccm, Yb (thd) 3 Is 150 sccm; in the deposition process, the heating temperature of the quartz tube is 1400 ℃, the rotation speed of the tube is 20 revolutions per minute, and the moving speed of the oxyhydrogen flame 4 is 100mm per minute;
step 5, depositing a core layer without rare earth of the 6 th layer of the inner core on the basis of the step 4, wherein the gas flow of the layer is SiCl 4 Is 50sccm and AlCl 3 Is 30sccm, POCl 3 Is 65 sccm;
the cross section of each layer deposited in step 4 and step 5 is schematically shown in fig. 4, and 15 is a deposited base layer; 16 is 5 core layers containing rare earth; 17 is a core layer containing no rare earth;
step 6, performing primary melting and shrinking on the quartz tube obtained in the step 5, wherein the flame temperature is 2050 ℃, the pulley speed is 20mm/min, and the melting and shrinking are performed until the diameter of a central hole is 1.5 mm;
step 7, introducing 100ml/min of C into the quartz tube with the central hole of 2mm in the step 6 under the conditions of the temperature of 1900 ℃ and the pulley speed of 100mm/min 2 F 6 And 300ml/min of O 2 Reciprocating for 1 time to remove the rare earth-free inner core layer by on-line etching to obtain a hollow tube with the center removed with the inner core layer;
step 8, performing secondary fusion on the hollow tube obtained in the step 7 at 2150 ℃ and at a pulley speed of 5mm/min to obtain a solid rod, and then polishing the solid rod under oxyhydrogen flame 4 at 1700 ℃ to obtain the optical fiber preform of the embodiment;
in this example, the composition of each deposition layer of steps 4, 5 is shown in table 1 below;
TABLE 1
Number of deposition layers SiCl 4 AlCl 3 POCl 3 Yb(thd) 3
1 150sccm 90sccm 60sccm 150sccm
2 150sccm 90sccm 60sccm 150sccm
3 150sccm 90sccm 60sccm 150sccm
4 150sccm 90sccm 60sccm 150sccm
5 150sccm 90sccm 60sccm 150sccm
6 50sccm 30sccm 65sccm 0sccm
The obtained optical fiber preform was subjected to refractive index testing,
the test results are shown in FIG. 3;
embodiment 2, a method for improving the center shift of the refractive index of an optical fiber preform
Step 1, respectively welding and connecting a cleaned quartz gas inlet pipe 1, a quartz deposition pipe 2 and a quartz tail gas pipe 3 end to an MCVD lathe; after the three sections of quartz tubes are connected, carrying out heat treatment on the quartz tubes, wherein the heat treatment temperature is 1900 ℃, and releasing the internal stress of a welding point;
step 2, adding SiCl serving as MCVD chemical reaction material 4 With POCl 3 The bubbler 6 is heated to 30 ℃, and the Yb chelate and the AlCl are mixed 3 The bubbler 8 is heated to 130 ℃ and the corresponding transport line 13 is heated to 240 ℃;
step 3, installing the soot wiper 14 and sealing, heating the flame at 2000 ℃, moving the pulley at 130mm/min, and introducing SF 6 Removing grease and dust on the inner wall of the quartz tube by using gas 10;
step 4, depositing the core layer containing the rare earth in a plurality of layers in sequence, dividing the gas material containing the rare earth into 5 layers, sequentially introducing the materials into a quartz tube to begin to deposit the core layer, wherein the gas flow of each layer is SiCl 4 Is 150sccm and AlCl 3 Is 90sccm, POCl 3 Is 60sccm, Yb (thd) 3 Is 150 sccm; in the deposition process, the heating temperature of the quartz tube is 1700 ℃, the rotation speed of the tube is 30 revolutions per minute, and the moving speed of the oxyhydrogen flame 4 is 130mm per minute;
step 5, depositing a core layer with an inner core not containing rare earth on the basis of the step 4, wherein the gas flow of the core layer is SiCl 4 Is 50sccm and AlCl 3 Is 30sccm, POCl 3 Is 65 sccm;
step 6, performing first melting and shrinking on the quartz tube obtained in the step 5, wherein the flame temperature is 2100 ℃, the pulley speed is 40mm/min, and the melting and shrinking are performed until the diameter of a central hole is 3 mm;
step 7, introducing 100ml/min of C into the quartz tube with the central hole of 3mm in the step 6 under the conditions of the temperature of 2150 ℃ and the pulley speed of 100mm/min 2 F 6 And 300ml/min of O 2 Repeating for 3 times to remove the rare earth-free inner core layer by on-line etching to obtain a hollow tube with the center removed with the inner core layer;
step 8, performing secondary fusion on the hollow tube obtained in the step 7 at the temperature of 2180 ℃ and the pulley speed of 10mm/min to obtain a solid rod, and polishing under oxyhydrogen flame 4 at 1700 ℃ to obtain the optical fiber preform of the embodiment;
example 3 preparation method for improving center shift of refractive index of optical fiber preform
Step 1, respectively welding and connecting a cleaned quartz inlet pipe 1, a cleaned quartz deposition pipe 2 and a cleaned quartz tail gas pipe 3 to an MCVD lathe end to end; after the three sections of quartz tubes are connected, carrying out heat treatment on the quartz tubes, wherein the heat treatment temperature is 2000 ℃, and releasing the internal stress of welding points;
step 2, adding SiCl serving as MCVD chemical reaction material 4 With POCl 3 The bubbler 6 is heated to 40 ℃, and the Yb chelate and the AlCl are mixed 3 The bubbler 8 is heated to 160 ℃ and the corresponding transport line 13 is heated to 260 ℃;
step 3, installing the soot scraper 14 and sealing, heating the flame at 2100 ℃, moving the pulley at a speed of 150mm/min, and introducing SF 6 Removing grease and dust on the inner wall of the quartz tube by using gas 10;
step 4, depositing the core layer containing the rare earth in a plurality of layers in sequence, dividing the gas material containing the rare earth into 5 layers, sequentially introducing the materials into a quartz tube to begin to deposit the core layer, wherein the gas flow of each layer is SiCl 4 Is 150sccm and AlCl 3 Is 90sccm, POCl 3 Is 60sccm, Yb (thd) 3 Is 150 sccm; in the deposition process, the heating temperature of the quartz tube is 2000 ℃, the rotation speed of the tube is 40 revolutions per minute, and the moving speed of the oxyhydrogen flame 4 is 150mm per minute;
step 5, depositing a core layer with an inner core not containing rare earth on the basis of the step 4, wherein the gas flow of the core layer is SiCl 4 Is 50sccm and AlCl 3 Is 30sccm, POCl 3 Is 65 sccm;
step 6, performing primary melting and shrinking on the quartz tube obtained in the step 5, wherein the flame temperature is 2150 ℃, the pulley speed is 60mm/min, and the melting and shrinking are performed until the diameter of a central hole is 4 mm;
step 7, introducing 100ml/min of C into the quartz tube with the central hole of 4mm obtained in the step 6 under the conditions of the temperature of 2180 ℃ and the pulley speed of 100mm/min 2 F 6 And 300ml/min of O 2 The on-line etching of the inner core layer without the rare earth is removed by 6 times of reciprocating to obtain a hollow tube with the center removed with the inner core layer;
step 8, performing second melting on the hollow tube obtained in the step 7 at the temperature of 2200 ℃ and the pulley speed of 20mm/min to obtain a solid rod, and then polishing the solid rod under oxyhydrogen flame 4 at the temperature of 1700 ℃ to obtain the optical fiber preform of the embodiment;
comparative example 4, the preform fabrication was performed using the existing method, with the following specific operations:
step 1, respectively welding and connecting a cleaned quartz gas inlet pipe 1, a quartz deposition pipe 2 and a quartz tail gas pipe 3 end to an MCVD lathe; after the three sections of quartz tubes are connected, carrying out heat treatment on the quartz tubes, wherein the heat treatment temperature is 2100 ℃, and releasing the internal stress of a welding point;
step 2, adding SiCl serving as MCVD chemical reaction material 4 With POCl 3 The bubbler 6 is heated to 25 ℃, and the Yb chelate and the AlCl are mixed 3 The bubbler 8 is heated to 120 ℃ and the corresponding transport line 13 is heated to 180 ℃;
step 3, installing the soot wiper 14 and sealing, heating the flame at 1900 ℃, moving the pulley at 100mm/min, and introducing SF 6 Removing grease and dust on the inner wall of the quartz tube by using gas 10;
step 4, dividing the gas materials into 5 layers, sequentially introducing the layers into a quartz tube to start to deposit a core layer, wherein the gas flow of each layer is SiCl 4 Is 150sccm and AlCl 3 Is 90sccm, POCl 3 Is 60sccm, Yb (thd) 3 Is 150 sccm; in the deposition process, the heating temperature of the quartz tube is 1920 ℃, the rotation speed of the tube is 30 revolutions per minute, and the moving speed of the oxyhydrogen flame 4 is 100mm per minute;
step 5, after the deposition is finished, the hollow quartz tube is fused and contracted into a solid rod, and the preparation of the optical fiber preform is finished; then polished under oxyhydrogen flame 4 at 1700 ℃ to obtain the optical fiber preform of the embodiment;
in this example, the composition of the deposit of step 4 is shown in table 2 below;
TABLE 2
Number of deposition layers SiCl 4 AlCl 3 POCl 3 Yb(thd) 3
1 150sccm 90sccm 60sccm 150sccm
2 150sccm 90sccm 60sccm 150sccm
3 150sccm 90sccm 60sccm 150sccm
4 150sccm 90sccm 60sccm 150sccm
5 150sccm 90sccm 60sccm 150sccm
The refractive index of the optical fiber preform obtained in comparative example 4 was measured, and the measurement result is shown in FIG. 2;
the optical fiber preform obtained in example 1 of the technical scheme of the present invention and the optical fiber preform obtained in comparative example 4 of the prior art are subjected to refractive index detection and comparison, as shown in fig. 3 and 2;
as shown in fig. 2, the refractive index of the optical fiber preform prepared in comparative example 4 of the prior art is measured to have a large refractive index fluctuation in the radial direction from less than 0 to more than 0, which indicates that the refractive index center of the optical fiber preform prepared in comparative example 4 of the prior art is greatly shifted;
as shown in fig. 3, the refractive index fluctuation of the optical fiber preform prepared in embodiment 1 of the present invention in the radial direction smaller than 0 and larger than 0 is greatly reduced, which indicates that the refractive index center shift of the optical fiber preform prepared in embodiment 1 of the present invention is greatly improved compared to the refractive index center shift of the optical fiber preform prepared in comparative example 4 of the prior art;
in addition, the core layer without rare earth oxide is deposited on the innermost layer, so that the on-line etching method can be applied to the elimination of the center deviation of the refractive index of the rare earth-doped optical fiber preform;
the optical fiber preform obtained by other embodiments of the invention has similar beneficial effects as described above;
the optical fiber preform obtained by other embodiments of the invention has similar beneficial effects as described above;
the foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims (9)

1. A preparation method for improving the refractive index center deviation of an optical fiber preform is characterized in that,
the method comprises the steps of firstly depositing a plurality of rare earth-containing core layers, then depositing a rare earth-free core layer, then firstly fusing and shrinking the inner hole of a quartz tube to 1.5-4 mm, introducing etching gas to remove the rare earth-free core layer on line, and finally fusing and shrinking the quartz tube to form the solid preform for the second time.
2. The method according to claim 1, wherein,
the preparation method for improving the refractive index center deviation of the optical fiber preform comprises the following steps:
step 1, welding a cleaned quartz gas inlet pipe (1)1, a cleaned quartz deposition pipe 2 and a cleaned quartz tail gas pipe 3 to an MCVD lathe; after the three sections of quartz tubes are welded, carrying out heat treatment on the quartz tubes to release the internal stress of the welding points;
step 2, heating MCVD chemical reaction material SiCl 4 With POCl 3 A bubbler (6), Yb chelate and AlCl 3 A bubbler (8) and a corresponding transport line (13);
step 3, installing a soot wiper (14) and sealing, then heating flame, moving a pulley and introducing etching gas (10) to remove grease and dust on the inner wall of the quartz tube;
step 4, changing the flame temperature and the pulley speed, rotating the pipeline, and sequentially depositing a rare earth-containing core layer in a multilayer manner;
step 5, depositing a core layer with an inner core not containing rare earth on the basis of the step 4;
step 6, performing primary melting and shrinking on the quartz tube obtained in the step 5, changing the flame temperature and the pulley speed, and melting and shrinking until the diameter of a central hole is 1.5-4 mm;
7, introducing etching gas (10) into the quartz tube with the center hole of 1.5-4 mm obtained in the step 6, heating and etching the inner wall of the quartz tube to remove the rare earth-free core layer on line;
and 8, performing secondary fusion on the hollow tube obtained in the step 7 after the rare earth-free core layer is removed to obtain a solid rod, and finishing the preparation of the optical fiber preform.
3. The method according to claim 2, wherein the reaction mixture,
in the step 1, the heating mode is heating by oxyhydrogen flame (4);
in the step 1, the heat treatment temperature is 1800-2000 ℃.
4. The method according to claim 2, wherein the reaction mixture,
in the step 2, the SiCl 4 With POCl 3 Heating the bubbler (6) to 25-40 ℃;
in the step 2, the Yb chelate and AlCl are 3 Heating the bubbler (8) to 120-160 ℃;
in the step 2, the corresponding conveying pipelines (13) are heated to 220-260 ℃.
5. The method according to claim 2, wherein the reaction mixture,
in the step 3, the heating temperature is 1900-2100 ℃;
in the step 3, the moving speed of the pulley is 100-150 mm/min;
in the step 3, the etching gas (10) is SF 6 、C 2 F 6 。
6. The method according to claim 2, wherein the reaction mixture,
in the step 4, the heating temperature is 1400-2000 ℃;
in the step 4, the moving speed of the pulley is 100-150 mm/min;
in the step 4, the rotation speed of the pipeline is 20-40 revolutions per minute;
in the step 4, the rare earth-containing core layer is 2-15 layers;
in the step 4, the diluent isEach layer of the core layer of soil comprises SiCl 4 、AlCl 3 、POCl 3 、Ce(thd) 3 、Yb(thd) 3 ；
In the step 5, the core layer not containing rare earth comprises SiCl 4 、AlCl 3 、POCl 3 。
7. The method according to claim 2, wherein the reaction mixture,
in the step 6, the heating temperature is 2050-2200 ℃;
in the step 6, the moving speed of the pulley is 20-60 mm/min.
8. The method according to claim 2, wherein the reaction mixture,
in the step 7, the etching gas (10) is C 2 F 6 、O 2 、SF 6 、C 2 F 3 Cl 3 ；
In the step 7, the heating temperature is 1900-2200 degrees;
in the step 7, the number of times of etching the inner wall of the quartz tube is 1-6 times.
9. The method according to claim 2, wherein the reaction mixture,
in the step 8, the heating temperature is 2150-2200 ℃;
in the step 8, the moving speed of the pulley is 5-40 mm/min.
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US5961682A (en) * 1995-07-12 1999-10-05 Samsung Electronics Co., Ltd. Method of fabricating optical fiber doped with rare earth element using volatile complex
JP2003146685A (en) * 2001-11-13 2003-05-21 Shin Etsu Chem Co Ltd Method for manufacturing quartz preform for optical fiber
CN104086079A (en) * 2014-07-25 2014-10-08 长飞光纤光缆股份有限公司 Fusion shrinkage preparation method of core rod of optical fiber preform rod
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