CN109399910B - Large-core-diameter optical fiber preform and preparation method of optical fiber - Google Patents

Large-core-diameter optical fiber preform and preparation method of optical fiber Download PDF

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CN109399910B
CN109399910B CN201811407377.3A CN201811407377A CN109399910B CN 109399910 B CN109399910 B CN 109399910B CN 201811407377 A CN201811407377 A CN 201811407377A CN 109399910 B CN109399910 B CN 109399910B
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optical fiber
core
quartz tube
fiber preform
preform
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CN109399910A (en
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侯超奇
折胜飞
李玮楠
常畅
赵保银
郑锦坤
李哲
高菘
张岩
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XiAn Institute of Optics and Precision Mechanics of CAS
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XiAn Institute of Optics and Precision Mechanics of CAS
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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
    • C03B37/01807—Reactant delivery systems, e.g. reactant deposition burners
    • C03B37/01815—Reactant deposition burners or deposition heating means
    • 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
    • C03B37/01807—Reactant delivery systems, e.g. reactant deposition burners
    • 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

Abstract

The invention relates to a preparation method of an optical fiber preform and an optical fiber, in particular to a preparation method of a large-core-diameter optical fiber preform and a corresponding low-loss optical fiberThe preparation method solves the problem that the core diameter of the optical fiber preform prepared in the prior art is small. The preparation method of the large-core-diameter optical fiber preform comprises the following steps: adopting improved chemical vapor deposition (MCVD) combined with rare earth ion vapor phase doping method, depositing all materials under vapor phase condition, sintering and pipe reducing process to obtain large-core optical fiber preform rod, wherein the prepared optical fiber preform rod core is composed of SiO2、Al2O3、P2O5、Yb2O3And F, rod core diameter>3 mm. The preparation method of the optical fiber comprises the following steps: and (3) sleeving the prepared large-core-diameter optical fiber preform by selecting a proper sleeving process to enable the core-cladding ratio of the preform to meet the requirement of the optical fiber, processing the sleeved preform into an octagonal structure, drawing at the temperature of 2050 +/-20 ℃, and drawing into the optical fiber.

Description

Large-core-diameter optical fiber preform and preparation method of optical fiber
Technical Field
The invention relates to a preparation method of an optical fiber preform and an optical fiber, in particular to a preparation method of a large-core-diameter optical fiber preform and a corresponding low-loss optical fiber.
Background
The fiber laser is called as a third-generation laser, has many advantages compared with the traditional laser, such as high electro-optic conversion efficiency, good beam quality, long service life, strong environmental adaptability, small occupied area and the like, belongs to a novel energy-saving and environment-friendly photoelectronic device, is widely applied in the fields of industrial manufacturing, medical treatment, energy exploration, military, national defense and the like, and has the market sales growth rate reaching more than two digits continuously for years.
The laser fiber material is used as a core device of the high-power fiber laser and is a key factor for determining the power of the fiber laser, and each step of improvement of the power of the fiber laser is closely related to the improvement of the performance of the fiber material and the device. The Yb-doped quartz fiber is the strategic high point of a high-power fiber laser. And as a core device, the overall performance of the Yb-doped silica optical fiber is mainly determined by the performance of an optical fiber preform. Therefore, the primary condition for obtaining high-performance optical fiber is to prepare an optical fiber preform with excellent performance.
A commonly used preparation method for the Yb-doped silica optical fiber preform at present is a modified vapor deposition (MCVD) combined solution doping method, and the method comprises the steps of fixing a silica tube on a deposition bed, depositing a loose layer on the inner wall of the silica tube, taking the deposition tube with the loose layer down from a deposition lathe, soaking the deposition tube with the loose layer in a solution containing rare earth ions, adsorbing the rare earth ions in the loose layer, discharging the solution, connecting the deposition tube to the deposition lathe again, evaporating the solvent by adopting a dehydration process, sintering the loose layer adsorbed with the rare earth ions into glass, and shrinking the glass into a solid preform. The process is complicated and time consuming to produce, and the preforms produced have a small core diameter, typically 1.5-2mm, which significantly affects the fiber yield per preform. In addition, the particle distribution consistency of the loose layer is not easy to control, and the distribution of the fiber core refractive index in the optical fiber preform is directly influenced. Meanwhile, the solution contains a large amount of hydroxyl groups, which easily increases the background loss of the optical fiber, and is not favorable for high-power output of the optical fiber.
Disclosure of Invention
Aiming at the technical problems of small core diameter, uneven distribution of refractive index of a fiber core in the optical fiber perform and large background loss of the optical fiber perform prepared by the existing method, the invention provides a preparation method of the large-core-diameter optical fiber perform and a preparation method for preparing the optical fiber by using the large-core-diameter optical fiber perform prepared by the method, wherein the core diameter of the prepared perform is more than 3mm, the optical fiber yield of a single perform is improved to a great extent, the axial refractive index and the radial refractive index of the prepared optical fiber perform core are uniform, and the numerical aperture is 0.06 +/-0.005.
The technical solution of the invention is as follows:
a preparation method of a large-core-diameter optical fiber preform is characterized by comprising the following steps:
1) SiO (silicon dioxide) is used as the core component of the large-core-diameter optical fiber preform2、Al2O3、P2O5、Yb2O3Converting the content of F into the flow of the gaseous reaction material during deposition, and setting the flow of the gaseous reaction material and the number of deposited layers in a control system of the MCVD equipment; wherein the gaseous reaction mass comprises SiCl4、Al(acac)3、Yb(thd)3、POCl3、SiF4And O2；
2) Connecting the cleaned quartz tube to an MCVD deposition bed, and preheating the quartz tube by adopting oxyhydrogen flame; while preheating, the quartz tube is in a rotating state; after preheating is finished, SF is introduced6The gas erodes the inner wall of the quartz tube;
3) after the erosion is finished, introducing gaseous reaction materials into a rotating quartz tube for core rod deposition; the heating temperature of the quartz tube is 1850 ℃ to 1950 ℃;
4) when the set number of the deposited layers is reached, pipe shrinkage is started, and chlorine is introduced in the pipe shrinkage process; and (5) after the quartz tube is contracted into a solid rod from the hollow tube, finishing the manufacturing of the prefabricated rod.
Further, in order to make the refractive index distribution of the prepared large core optical fiber preform more uniform, in step 1), the preform core is composed of SiO2、Al2O3、P2O5、Yb2O3And F has a component content of Al2O3：1～2.5mol％，P2O5：1～2mol％，SiO2：95～97.5mol％，Yb2O3：0.1-0.25mol％，F：0～0.8mol％。
Further, in order to make the core diameter of the optical fiber preform larger, the number of deposition layers set in step 1) is 10.
Further, in order to make the refractive index distribution of the prepared large-core optical fiber preform more uniform, the flow rates of the gaseous reaction materials in each deposition layer set in step 1) are as follows:
Figure BDA0001877691210000021
Figure BDA0001877691210000031
during the reaction, O is introduced2In an amount sufficient to make the reaction material SiCl4、Al(acac)3、Yb(thd)3、POCl3、SiF4And O2The reaction takes place to form the corresponding oxide.
Further, in order to make the refractive index distribution of the prepared large-core optical fiber preform more uniform, the flow rates of the gaseous reaction materials in each deposition layer set in step 1) are as follows:
Figure BDA0001877691210000032
or
Figure BDA0001877691210000033
Figure BDA0001877691210000041
Or
Figure BDA0001877691210000042
Or
Figure BDA0001877691210000043
During the reaction, O is introduced2Is in sufficient amountSo that the reaction material SiCl4、Al(acac)3、Yb(thd)3、POCl3、SiF4And O2The reaction takes place to form the corresponding oxide.
Further, in step 3), the reaction mass Al (acac)3And Yb (thd)3Respectively as independent systems, and the heated gases enter the quartz tube in a gaseous state; al (acac)3The heating temperature of (b) is 240-3The heating temperature of the furnace is 200-240 ℃.
Further, the carrier gas O is passed through the step 3)2Delivering POCl in the form of bubbling3、SiCl4To the inside of the quartz tube; delivery of gas phase Al (acac) by carrier gas He3、Yb(thd)3Entering a quartz tube; gaseous SiF4And O2Directly into the quartz tube.
Further, the pipe shrinking in the step 4) is carried out at 2000-2100 ℃.
Meanwhile, the invention also provides a preparation method of the optical fiber, which comprises the following steps:
1) preparing a large-core-diameter optical fiber preform by adopting the method;
2) sleeving the large-core-diameter optical fiber preform prepared in the step 1); processing the sleeve into an octagon;
3) drawing at 2050 +/-20 ℃ to obtain the optical fiber.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention adopts an improved chemical vapor deposition (MCVD) combined rare earth ion vapor phase doping method and adopts a matrix material Al2O3、P2O5、SiO2Respectively from gaseous Al (acac)3、POCl3、SiCl4At high temperature and O2Reaction to form a rare earth dopant Yb2O3From gaseous Yb (thd)3And O2All the reaction products are deposited on the inner wall of the quartz tube in a glass state at 1850-1950 deg.C, and are sintered into a solid glass rod, i.e. a large-core-diameter optical fiber preform rod, after multiple depositions, the deposited material is the core of the preform rodA rod.
(2) Due to dopant ion migration, P2O5The volatilization may cause the uneven refractive index distribution of the prefabricated rod, and the invention adjusts Yb (thd) in the deposition layer3、Al(acac)3、POCl3Or SiF4The flow rate of the components is adjusted to ensure that the prepared large-core-diameter preform has uniform refractive index distribution.
(3) The preparation process of the invention is simple, and the whole deposition process can be completed in a closed system at one time, thereby improving the production efficiency of the prefabricated rod.
(4)Al2O3The reaction mass of (A) is Al (acac)3And the gas circuit is not easy to corrode.
(5) The adoption of the gas phase doping technology is beneficial to the uniform dispersion of doped ions in the glass, and the cluster effect is reduced, so that the loss of the optical fiber can be reduced.
Drawings
FIG. 1 is a refractive index profile of a large core optical fiber preform according to an embodiment of the present invention;
FIG. 2 is a refractive index profile of a second large core optical fiber preform according to an embodiment of the present invention;
FIG. 3 is a graph showing refractive index profiles of five large core optical fiber preforms according to embodiments of the present invention;
FIG. 4 is a refractive index profile of a fiber preform tube according to example five of the present invention;
FIG. 5 is an absorption spectrum of a five-fiber optical fiber according to an embodiment of the present invention;
FIG. 6 is a graph of loss spectra of five optical fibers according to examples of the present invention;
FIG. 7 is an end view of a five-fiber embodiment of the present invention;
fig. 8 is a graph of laser light-to-light conversion efficiency of five optical fibers according to an embodiment of the present invention.
The specific implementation scheme is as follows:
the invention provides Al2O3-P2O5-SiO2The preparation method of the ternary system laser large-core-diameter optical fiber preform comprises the following steps:
1) according to the large core diameter optical fiber preform core component SiO2、Al2O3、P2O5、Yb2O3And F, calculating the content of SiCl serving as a gaseous reaction material4、Al(acac)3、Yb(thd)3、POCl3、SiF4Setting flow values in a control system of the MCVD equipment according to the flow of the equal components;
2) taking a thin-wall quartz tube with the outer diameter of 28mm and the inner diameter of 24mm as a reaction base tube, cleaning the reaction base tube, connecting the reaction base tube to an MCVD deposition bed, and preheating the quartz tube by using oxyhydrogen flame; while preheating, the quartz tube is in a rotating state; after preheating is finished, SF is introduced6The gas erodes the inner wall of the quartz tube to eliminate impurities and pollutants on the inner wall of the quartz tube;
3) after the corrosion is finished, introducing the gaseous reaction materials into a quartz tube rotating at the rotating speed of 30 revolutions per minute according to a set flow value, and starting deposition at 1850-1950 ℃;
4) when the set number of deposited layers reaches 10, performing pipe shrinking at 2000-2100 ℃, and introducing chlorine gas in the pipe shrinking process; after the quartz tube is contracted into a solid rod from a hollow tube, the prefabricated rod is manufactured, the deposited material is a core rod of the prefabricated rod, and the deposited tube is a cladding layer of the prefabricated rod.
According to the core cladding ratio, a proper sleeving process is selected to perform sleeving on the optical fiber preform, the sleeved preform is cold-processed into an octagonal structure, drawing is performed at the temperature of 2050 +/-20 ℃, two layers of coatings are adopted, and a double-clad laser optical fiber is obtained, wherein the specification of the optical fiber is 20/400 microns.
The formula of the large-core-diameter optical fiber preform rod of the invention has the following requirements: al (Al)2O3：1～2.5mol％，P2O5：1～2mol％，SiO2：95～97.5mol％，Yb2O3: 0.1 to 0.25 mol%, F: 0-0.8 mol%; the preform preparation apparatus comprises three separate systems, one for depositing bulk content, e.g. SiCl, in the composition4And SiF4(ii) a Reaction Mass Al (acac)3As an independent system, sublimating from a pipeline with the temperature of 240-260 ℃, and then entering a quartz deposition tube in a gaseous state; yb (thd)3As an independent system, sublimating from a pipeline with the temperature of 200-240 ℃, and then entering quartz sediment in a gas stateAccumulating the tube; all gaseous reaction materials react with O at high temperature2Reacting, depositing the product on the inner wall of the quartz tube in a glass state (omitting the process of depositing a loose layer and then sintering), and preparing the optical fiber preform with large core diameter; addition of POCl3The photoinduced darkening effect under the condition of high-power laser output application can be inhibited, and the refractive index of the core rod can be effectively reduced; the preparation process is simple, the whole deposition process can be completed in a closed system at one time (different from a solution doping method, a loose body is deposited at a low temperature, then the deposited loose body is taken down, soaked in a solution and dehydrated at a high temperature), and the yield of the single Yb-doped optical fiber preform is effectively improved.
The invention is further illustrated by the following examples.
The first embodiment is as follows:
calculating gaseous reaction material Al (acac) according to the formula component requirements of the fiber core of the large-core-diameter optical fiber preform3、POCl3、SiCl4、Yb(thd)3And SiF4And the flow of the gaseous reaction material is set in the MCVD automatic control software, see Table 1; connecting the quartz tube to an MCVD deposition lathe, preheating the quartz tube by using oxyhydrogen flame, and introducing SF after preheating is finished6The gas erodes the inner wall of the quartz tube, and after the erosion is finished, the gas material is introduced into the quartz tube according to the set flow value to begin to deposit the core layer; in the deposition process, the heating temperature of the quartz tube is 1850 ℃, the rotation speed of the tube is 30 revolutions per minute, and the moving speed of oxyhydrogen flame is 100mm per minute; after the deposition is finished, introducing Cl2Sintered quartz tube, Cl2The flow rate of the hollow tube is 5mL/min, and after the hollow tube is subjected to multiple tube shrinkage and is sintered into a solid rod, the optical fiber preform is polished by flame at 1600 ℃. The prepared large-core optical fiber preform was fused at a high temperature, and the refractive index and the core diameter thereof were measured, with the results as shown in FIG. 1 and 1 in Table 7#As shown.
Table 1 example a flow rate (sccm) of each component in each deposition layer
Number of deposition layers SiCl4 Al(acac)3 Yb(thd)3 POCl3 SiF4
1 200 45 300 90 20
2 200 45 300 90 20
3 200 45 300 90 20
4 200 45 300 90 20
5 200 45 300 90 20
6 200 45 300 90 20
7 200 45 300 90 20
8 200 45 300 90 20
9 200 45 300 90 20
10 200 45 300 90 20
As can be seen from fig. 1, the refractive index of the prepared large-core optical fiber preform exhibits a W-shape in the radial direction, and the waveguide structure is not favorable for laser output, so that the preform is not subjected to fiber drawing.
Example two:
adjusting the composition Al (acac) according to the composition flux of the optical fiber preform and the refractive index profile of the preform in example one3、POCl3、Yb(thd)3Or SiF4The flow of the system is set in MCVD automatic control software, and the set value refers to a table 2; connecting the quartz tube to an MCVD deposition lathe after setting is finished, preheating the quartz tube by using oxyhydrogen flame, and introducing SF after preheating is finished6The gas erodes the inner wall of the quartz tube; after the corrosion is finished, introducing a gas material into the quartz tube according to a set flow value to start to deposit a core layer; in the deposition process, the heating temperature of the quartz tube is 1850 ℃, the rotation speed of the tube is 30 revolutions per minute, and the moving speed in the oxyhydrogen flame deposition process is 100mm per minute; after the deposition is finished, introducing Cl2Sintered quartz tube, Cl2The flow rate of the hollow tube is 5mL/min, and after the hollow tube is subjected to multiple tube shrinkage and is sintered into a solid rod, the optical fiber preform is polished by flame at 1600 ℃. Fusing the prepared large-core optical fiber preform at high temperature, testing refractive index, which is distributed as shown in FIG. 2, and calculating corresponding numerical aperture, the results are shown in 2 in Table 7#And (3) sampling.
And (3) selecting a proper sleeving process according to the geometric parameters of the prepared large-core-diameter optical fiber preform to sleeve the preform, so that the core cladding ratio of the preform meets the requirement of the optical fiber, cold-machining the sleeved preform into an octagon, drawing at the temperature of 2050 +/-20 ℃, and coating by two layers to obtain the double-clad laser optical fiber. Performance parameter of optical fiberThe data are shown in 2 in Table 7#And (3) sampling.
TABLE 2 example two gas flow rates (sccm) for each component of each deposition layer
Number of deposition layers SiCl4 Al(acac)3 Yb(thd)3 POCl3 SiF4
1 200 45 300 90 16
2 200 45 300 90 14
3 200 45 300 90 10
4 200 45 300 90 8
5 200 45 300 90 6
6 200 45 300 90 3
7 200 45 300 90 10
8 200 45 300 90 15
9 200 60 350 110 20
10 200 80 400 130 26
Example three:
according to the requirements of the components of the formula of the fiber core of the large-core-diameter optical fiber preform, in combination with the component flow and refractive index distribution results of the optical fiber preform in the first embodiment, the flow values of the components in each deposition layer set in the MCVD automatic control software in the first embodiment are shown in Table 3; connecting the quartz tube to an MCVD deposition lathe after setting is finished, preheating the quartz tube by using oxyhydrogen flame, and introducing SF after preheating is finished6The gas erodes the inner wall of the quartz tube; after the corrosion is finished, introducing a gas material into the quartz tube according to a set flow value to start to deposit a core layer; in the deposition process, the heating temperature of the quartz tube is 1900 ℃, the rotation speed of the tube is 30 revolutions per minute, and the moving speed of oxyhydrogen flame is 100mm per minute; after the deposition is finished, introducing Cl2The quartz tube is sintered, the flow of chlorine is 5mL/min, and after the hollow tube is sintered into a solid rod through multiple times of tube shrinkage, the optical fiber preform is polished by flame at 1600 ℃. Fusing the prepared large-core optical fiber preform at high temperature, testing the refractive index and calculating the corresponding numerical aperture, the results are shown in 3 in Table 7#The samples are shown.
Selecting proper sleeving process according to the geometric parameters of the prepared large-core-diameter optical fiber preform to sleeve the preform, enabling the core cladding ratio to meet the requirement of the optical fiber, cold-machining the sleeved preform into an octagon, drawing at 2050 +/-20 ℃, and adopting two layersAnd coating to obtain the double-clad laser fiber. The optical fiber performance parameters are shown in Table 7, item 3#And (3) sampling.
TABLE 3 example three gas flow rates (sccm) for each component of each deposition layer
Number of deposition layers SiCl4 Al(acac)3 Yb(thd)3 POCl3 SiF4
1 200 45 300 90 16
2 200 45 300 90 14
3 200 45 300 90 10
4 200 45 300 90 8
5 200 45 300 90 6
6 200 45 300 90 3
7 200 45 300 90 10
8 200 45 300 90 15
9 200 45 350 110 20
10 200 45 400 130 26
Example four:
according to the requirements of the components of the formula of the fiber core of the large-core-diameter optical fiber preform, the flow values of the components in the deposition layers set in MCVD automatic control software in the embodiment are shown in the table 4 by combining the component flow and refractive index distribution results of the optical fiber preform in the embodiment I; connecting the quartz tube to an MCVD deposition lathe after setting is finished, preheating the quartz tube through oxyhydrogen flame, and introducing SF after preheating is finished6The gas erodes the inner wall of the quartz tube to eliminate impurities and pollutants on the inner wall of the quartz tube; after the corrosion is finished, introducing a gas material into the quartz tube according to a set flow value to start to deposit a core layer; in the deposition process, the heating temperature of the quartz tube is 1900 ℃, the rotation speed of the tube is 30 revolutions per minute, and the moving speed of oxyhydrogen flame is 100mm per minute; after the deposition is finished, introducing Cl2The quartz tube is sintered, the flow of chlorine is 5mL/min, and after the hollow tube is sintered into a solid rod through multiple times of tube shrinkage, the optical fiber preform is polished by flame at 1600 ℃. Fusing the prepared large-core optical fiber preform at high temperature, testing the refractive index and calculating the corresponding numerical aperture, the results are shown in 4 in Table 7#The samples are shown.
Selecting proper sleeving process according to the geometric parameters of the prepared large-core-diameter optical fiber preform to sleeve the preform, so that the core cladding ratio of the preform meets the requirement of the optical fiber, and sleevingAnd cold-working the prefabricated rod into octagon, drawing at 2050 +/-20 ℃, coating by two layers to obtain the double-clad laser fiber, wherein the drawn fiber has the specification of 20/400 mu m. The optical fiber performance parameters are shown in Table 7, item 4#And (3) sampling.
Table 4 example four gas flow rates (sccm) for each component of each deposition layer
Number of deposition layers SiCl4 Al(acac)3 Yb(thd)3 POCl3 SiF4
1 200 60 300 90 8
2 200 60 300 90 4
3 200 60 300 90 3
4 200 60 300 90 1
5 200 60 300 90 5
6 200 60 300 90 6
7 200 60 300 90 8
8 200 60 300 90 12
9 200 80 350 110 15
10 200 100 400 130 18
Example five:
according to the requirements of the components of the formula of the fiber core of the large-core-diameter optical fiber preform, in combination with the results of the component flow and refractive index distribution of the large-core-diameter optical fiber preform in the embodiment, the flow values of the components in the deposition layers set in the MCVD automatic control software in the embodiment are referred to in table 5; connecting the quartz tube to an MCVD deposition lathe after setting is finished, preheating the quartz tube through oxyhydrogen flame, and introducing SF after preheating is finished6The gas erodes the inner wall of the quartz tube to eliminate impurities and pollutants on the inner wall of the quartz tube; after the corrosion is finished, introducing a gas material into the quartz tube according to a set flow value to start to deposit a core layer; in the deposition process, the heating temperature of the quartz tube is 1940 ℃, the rotation speed of the tube is 30 r/min, and the moving speed in the oxyhydrogen flame deposition process is 100 mm/min; after the deposition is finished, introducing Cl2Sintered quartz tube, Cl2The flow rate of the hollow tube is 5mL/min, and after the hollow tube is subjected to multiple tube shrinkage and is sintered into a solid rod, the optical fiber preform is polished by flame at 1600 ℃. Fusing the prepared large-core optical fiber preform at high temperature, testing the refractive index, referring to FIG. 3, calculating the corresponding numerical aperture, and finding the result 5 in Table 7#The samples are shown. From FIG. 3As can be seen, the refractive index of the large core optical fiber preform prepared in this example tends to be flat.
Selecting a proper sleeving process according to the geometric parameters of the preform to sleeve the preform so that the core cladding ratio of the preform meets the requirement of the optical fiber, wherein the refractive index distribution of the preform after sleeving is shown in figure 4; and processing the sleeved preform into an octagonal structure, drawing at the temperature of 2050 +/-20 ℃, and coating by two layers to obtain the double-clad laser fiber. The optical fiber performance parameters are shown in Table 7, 5#A sample; the absorption spectrum is shown in FIG. 5, the loss spectrum of the fiber is shown in FIG. 6, the end view of the fiber is shown in FIG. 7, and the core package size of the fiber is 19.9 μm/399.8 μm.
Table 5 example five gas flow rates (sccm) for each component of each deposition layer
Number of deposition layers SiCl4 Al(acac)3 Yb(thd)3 POCl3 SiF4
1 200 60 300 90 8
2 200 60 300 90 4
3 200 60 300 90 3
4 200 60 300 90 1
5 200 60 300 90 5
6 200 60 300 90 6
7 200 60 300 90 8
8 200 60 300 90 12
9 200 80 350 110 15
10 200 100 400 130 18
Example six:
according to the requirements of the components of the formula of the fiber core of the large-core-diameter optical fiber preform, in combination with the component flow and refractive index distribution results of the optical fiber preform in the first embodiment, the flow values of the components in each deposition layer set in the MCVD automatic control software in the first embodiment are shown in Table 6; after the setting is finished, connecting the quartz tube to an MCVD deposition lathe, preheating the quartz tube through oxyhydrogen flame, and after the preheating is finished, introducing a gas material into the quartz tube according to a set flow value to start depositing a core layer; after the corrosion is finished, according to the gas flow values of all components in all deposition layers listed in the table 3, introducing gas materials into the quartz tube to start to deposit a core layer; during deposition, the quartz tube was heated to 1940 deg.C, the tube was rotated at 30 rpm, and the oxyhydrogen flame was appliedThe moving speed in the deposition process is 100 mm/min; after the deposition is finished, introducing Cl2Initial collapse of the tube, Cl2The flow rate of the hollow tube is set to be 5mL/min, and after the hollow tube is subjected to multiple tube shrinkage and is sintered into a solid rod, the optical fiber preform is polished by flame at 1600 ℃. Fusing the prepared large-core optical fiber preform at high temperature, testing the refractive index, and calculating the corresponding numerical aperture, the results of which are shown in 6 in Table 7#The samples are shown.
And (3) selecting a proper sleeving process according to the geometric parameters of the preform to sleeve the preform, so that the core cladding ratio of the preform meets the requirement of the optical fiber, processing the sleeved preform into an octagonal structure, drawing at the temperature of 2050 +/-20 ℃, and coating by two layers to obtain the double-clad laser optical fiber. The absorption coefficient and core loss of the prepared optical fiber were measured, and the results are shown in 6 of Table 7#And (3) sampling.
Table 6 example six gas flow rates (sccm) for each component of each deposition layer
Number of deposition layers SiCl4 Al(acac)3 Yb(thd)3 POCl3 SiF4
1 200 75 300 90 15
2 200 75 300 90 12
3 200 75 300 90 11
4 200 75 300 90 8
5 200 75 300 90 7
6 200 75 300 90 6
7 200 75 300 90 4
8 200 75 300 90 8
9 200 90 350 110 12
10 200 110 400 130 15
TABLE 7 corresponding fiber test parameters in the specific examples
Figure BDA0001877691210000121
Figure BDA0001877691210000131
Refractive index profiles of the optical fiber preforms prepared in examples three, four and six were similar, all as shown in FIG. 3; the drawn optical fibers were 20/400 μm in both dimensions and the refractive index profiles were similar, as shown in FIG. 4.
By contrast, 5 with the least background loss was selected#The fiber was subjected to high power laser test experiments with 5#The optical fiber is used as a laser amplification stage, the power of the seed light entering the optical fiber is 20W, the test shows that the laser conversion efficiency of the optical fiber is 82.7 percent, the use requirement of a commercial optical fiber laser is met, and the laser slope curve is shown in figure 8.

Claims (5)

1. A preparation method of a large-core-diameter optical fiber preform is characterized by comprising the following steps: the method comprises the following steps:
1) SiO (silicon dioxide) is used as the core component of the large-core-diameter optical fiber preform2、Al2O3、P2O5、Yb2O3And F in the amount converted to the flow rate of the gaseous reaction material during deposition, wherein the preform core component is SiO2、Al2O3、P2O5、Yb2O3And F is SiO2：95～97.5mol％，Al2O3：1～2.5mol％，P2O5：1～2mol％，Yb2O3: 0.1 to 0.25 mol%, F: 0-0.8 mol%; setting the flow rate of gaseous reaction materials and the number of deposited layers in a control system of MCVD equipment, wherein the number of the deposited layers is 10; wherein the gaseous reaction mass comprises SiCl4、Al(acac)3、Yb(thd)3、POCl3、SiF4And O2The flow rate of the gaseous reaction materials is as follows:
Figure FDA0002530690600000011
or the flow rate of the gaseous reaction materials is as follows:
Figure FDA0002530690600000012
Figure FDA0002530690600000021
or the flow rate of the gaseous reaction materials is as follows:
Figure FDA0002530690600000022
or the flow rate of the gaseous reaction materials is as follows:
Figure FDA0002530690600000023
or the flow rate of the gaseous reaction materials is as follows:
Figure FDA0002530690600000031
2) connecting the cleaned quartz tube to an MCVD deposition bed, and preheating the quartz tube by adopting oxyhydrogen flame; while preheating, the quartz tube is in a rotating state; after preheating is finished, SF is introduced6The gas erodes the inner wall of the quartz tube;
3) after the erosion is finished, introducing gaseous reaction materials into a rotating quartz tube for core rod deposition; the heating temperature of the quartz tube is 1850 ℃ to 1950 ℃;
4) when the set number of the deposited layers is reached, pipe shrinkage is started, and chlorine is introduced in the pipe shrinkage process; and (5) after the quartz tube is contracted into a solid rod from the hollow tube, finishing the manufacturing of the prefabricated rod.
2. The method of claim 1, wherein the step of preparing a large core optical fiber preform comprises: in step 3), reaction mass Al (acac)3And Yb (thd)3Respectively as independent systems, and the heated gases enter the quartz tube in a gaseous state; al (acac)3The heating temperature of (b) is 240-3The heating temperature of the furnace is 200-240 ℃.
3. The method of claim 2, wherein the step of preparing a large core optical fiber preform comprises: passing a carrier gas in the step 3)O2Delivery of POCl3、SiCl4To the inside of the quartz tube; delivery of gas phase Al (acac) by carrier gas He3、Yb(thd)3Entering a quartz tube; gaseous SiF4And O2Directly into the quartz tube.
4. A method for preparing a large core optical fiber preform according to claim 3, wherein: and (4) performing pipe shrinking at 2000-2100 ℃.
5. A method of making an optical fiber, comprising: comprises the following steps
1) Preparing a large-core optical fiber preform by the preparation method according to any one of claims 1 to 4;
2) sleeving the prepared large-core-diameter optical fiber preform rod into a sleeve, and processing the sleeve into an octagon;
3) drawing at 2050 +/-20 ℃ to obtain the optical fiber.
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