CN117209134A - Quartz deposition tube, rare earth doped optical fiber preform and preparation method of optical fiber - Google Patents
Quartz deposition tube, rare earth doped optical fiber preform and preparation method of optical fiber Download PDFInfo
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- 230000008021 deposition Effects 0.000 title claims abstract description 84
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 78
- 239000013307 optical fiber Substances 0.000 title claims abstract description 60
- 239000010453 quartz Substances 0.000 title claims abstract description 52
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 52
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 52
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 58
- -1 rare earth salt Chemical class 0.000 claims abstract description 27
- 238000002791 soaking Methods 0.000 claims abstract description 14
- 238000001035 drying Methods 0.000 claims abstract description 7
- 238000001179 sorption measurement Methods 0.000 claims abstract description 5
- 238000000151 deposition Methods 0.000 claims description 83
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- 239000012792 core layer Substances 0.000 claims description 18
- 238000009826 distribution Methods 0.000 claims description 18
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- 229910052760 oxygen Inorganic materials 0.000 claims description 11
- 230000004927 fusion Effects 0.000 claims description 8
- 239000011259 mixed solution Substances 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 238000010926 purge Methods 0.000 claims description 6
- 239000002019 doping agent Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 230000018044 dehydration Effects 0.000 claims description 4
- 238000006297 dehydration reaction Methods 0.000 claims description 4
- 230000003647 oxidation Effects 0.000 claims description 4
- 238000007254 oxidation reaction Methods 0.000 claims description 4
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 claims description 3
- 239000002994 raw material Substances 0.000 claims description 3
- 239000005049 silicon tetrachloride Substances 0.000 claims description 3
- 229910052684 Cerium Inorganic materials 0.000 claims description 2
- 229910052765 Lutetium Inorganic materials 0.000 claims description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 2
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 2
- 229910052797 bismuth Inorganic materials 0.000 claims description 2
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 claims description 2
- ZMIGMASIKSOYAM-UHFFFAOYSA-N cerium Chemical compound [Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce] ZMIGMASIKSOYAM-UHFFFAOYSA-N 0.000 claims description 2
- 150000001875 compounds Chemical class 0.000 claims description 2
- 239000011261 inert gas Substances 0.000 claims description 2
- 230000001590 oxidative effect Effects 0.000 claims description 2
- 229910052698 phosphorus Inorganic materials 0.000 claims description 2
- 239000011574 phosphorus Substances 0.000 claims description 2
- 229910052706 scandium Inorganic materials 0.000 claims description 2
- 229910052727 yttrium Inorganic materials 0.000 claims description 2
- 239000000126 substance Substances 0.000 claims 1
- 238000010438 heat treatment Methods 0.000 abstract description 2
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 16
- 239000000835 fiber Substances 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 10
- KWMNWMQPPKKDII-UHFFFAOYSA-N erbium ytterbium Chemical compound [Er].[Yb] KWMNWMQPPKKDII-UHFFFAOYSA-N 0.000 description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 8
- CKLHRQNQYIJFFX-UHFFFAOYSA-K ytterbium(III) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Yb+3] CKLHRQNQYIJFFX-UHFFFAOYSA-K 0.000 description 8
- 229910052734 helium Inorganic materials 0.000 description 6
- 239000000460 chlorine Substances 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 229910052769 Ytterbium Inorganic materials 0.000 description 4
- HDGGAKOVUDZYES-UHFFFAOYSA-K erbium(iii) chloride Chemical compound Cl[Er](Cl)Cl HDGGAKOVUDZYES-UHFFFAOYSA-K 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 3
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- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 2
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- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
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- 239000010703 silicon Substances 0.000 description 1
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- Manufacture, Treatment Of Glass Fibers (AREA)
Abstract
The invention discloses a quartz deposition tube, a rare earth doped optical fiber preform and a preparation method of an optical fiber. Heating and breaking a tail pipe at one end of a quartz deposition tube, injecting rare earth salt and a codopant solution into the quartz deposition tube, fully soaking, drying and shrinking to obtain a rare earth doped core rod, balancing the uneven rare earth caused by volatilization in the shrinking process by designing the gradual adsorption capacity of a loose layer on rare earth, obtaining an optical fiber preform with uniform rare earth doping concentration, and preparing an optical fiber by drawing the optical fiber preform.
Description
Technical Field
The invention belongs to the field of optical fiber manufacturing, relates to a rare earth doping technology for optical fiber manufacturing, and in particular relates to a quartz deposition tube, a rare earth doped optical fiber preform and a preparation method of an optical fiber.
Background
The rare earth doped optical fiber preform is a key material for producing an optical fiber amplifier and an optical fiber laser. Compared with the traditional semiconductor laser amplifier, the optical fiber amplifier can directly amplify the signal in full light without the complex processes of photoelectric conversion, electro-optical conversion, signal regeneration and the like, has the characteristics of high gain, large bandwidth, low noise, polarization insensitivity gain and low lead-in loss in the working wavelength range, has good transparency, and is particularly suitable for relay amplification of long-distance optical communication. It can be said that the optical fiber amplifier lays an important technical foundation for realizing high-capacity all-optical communication. Rare earth doped fiber is used as an important component of high power fiber laser and is a main factor for determining the performance of high power fiber laser.
At present, the rare earth element doping method for producing the rare earth doped optical fiber preform mainly comprises a gas phase method, including rare earth chloride gas phase deposition and rare earth chelate gas phase deposition; the solution method comprises soaking rare earth solution in a tube and soaking rare earth solution outside the tube; a nano ion direct deposition method and a gel method. The solution method is the main preparation method of the doped optical fiber preform at present and comprises the following steps of: depositing a powder rod by a VAD method, soaking the powder rod in a solution containing rare earth elements, and vitrifying the soaked powder rod in a high-temperature furnace to prepare a rare earth element doped optical fiber preform core layer (CN 102108008B); in-tube method: and sequentially depositing an inner cladding layer and a loose ash core layer in a deposition tube, and injecting a solution containing rare earth chloride into the deposition tube, wherein the fused deposition tube, the inner cladding layer and the loose ash core layer are solid prefabricated rods (CN 102515501B, CN1500069, US 5711782A and US 5262365A).
The rare earth solution is doped by an in-tube method, doped rare earth ions and co-doping agents are easy to volatilize in a large amount in a high-temperature melting stage, so that the rare earth ions of the core rod are unevenly distributed and distributed in a V shape, the lower the content of the intermediate rare earth ions is, the refractive index profile of the finally drawn optical fiber is concave, the matching of an active optical fiber and a passive optical fiber is affected, the thermal stability of a laser is reduced, the quality of a light beam is poor, and the central dark spot is caused, so that the uniform distribution of the rare earth ions is very critical in the process of preparing the active optical fiber preform by a liquid phase method.
Disclosure of Invention
Aiming at the defects of the prior art, one of the purposes of the invention is to provide a quartz deposition tube and a preparation method thereof, wherein the density of a loose layer in the quartz deposition tube in the radial direction is controlled to obtain the rare earth doped quartz deposition tube with gradually changed doping concentration.
The invention also aims to prepare the uniformly doped rare earth doped prefabricated rod by the quartz deposition tube through fusion shrinkage, and solve the problem of uneven radial distribution of rare earth ions caused by volatilization of the rare earth ions in the fusion shrinkage process of the quartz deposition tube.
The invention also aims to prepare the rare earth doped optical fiber by using the rare earth doped preform rod so as to solve the problems that in the prior art, the doped rare earth has uneven refractive index due to uneven rare earth doping, and further the production and the use of the high-power optical fiber are limited; the optical fiber prepared by the method has the characteristics of smooth distribution of refractive index on the section, high gain, large bandwidth, low noise, polarization insensitive gain and low introduction loss.
The invention adopts the technical proposal for solving the problems that:
in one aspect, the invention provides a quartz deposition tube for preparing an optical fiber preform, comprising a liner tube and a loose layer deposited on the inner wall of the liner tube by adopting an MCVD process, wherein the density of the loose layer is gradually distributed in the radial direction, so that the gradual distribution of the adsorption capacity of dopants is generated.
As a preferred solution, the closer to the center, the greater the density of the porous layer.
The density distribution of the porous layer satisfies the following equation:
ρ＝ρ 0 +A*B 2
ρ is the density of the loose layer at any point ρ 0 The density of the loose layer closest to the inner wall of the liner tube is represented by B, the radial distance between the corresponding point and the inner wall of the liner tube is represented by A, and the gradient coefficient is represented by A.
In the above equation, ρ and ρ 0 Are all in g/cm 3 ，ρ 0 The range of the value of (2) is 0.275<A<0.55；
The unit of the distance B is millimeter (mm), and the value range of the distance B is not more than 2.5;
a is a gradient coefficient, is a dimensionless parameter, and is generally 0.05-0.21 and optimally 0.1 according to the shrinkage temperature in the shrinkage process of the prepared preform and the volatility of rare earth at the shrinkage temperature.
According to the scheme, the density distribution of the loose layer is controlled, so that the density of the deposition layer from the inner wall of the liner tube to the central area is gradually increased, the adsorption capacity of the deposition layer on rare earth doped ions is enhanced, namely, after soaking is finished, the content of the rare earth ions in the deposition layer from the inner wall of the liner tube to the central area of the powder rod is gradually increased, the problem that the rare earth ions in the deposition layer close to the central area in the melting stage volatilize fast is counteracted, the problem that the rare earth ions of the core rod by the traditional liquid phase method are distributed in a V shape is solved, and the uniformly doped optical fiber preform is obtained after melting.
In another aspect, the present invention also provides a method for preparing a quartz deposition tube, comprising the steps of:
preparing a liner tube to be deposited, and introducing a raw material gas containing silicon tetrachloride and oxygen into the liner tube for deposition;
the deposition temperature is controlled to be gradually increased layer by layer to obtain loose layers with gradually increased density.
It should be noted that, during the loose layer deposition process of the liner tube, each layer is very thin, so the density distribution is similar to the gradual change distribution.
As a preferred technical scheme, the initial deposition temperature is 1200-1250 ℃, the increment of the deposition temperature of each subsequent layer is 5-15 ℃, and the highest deposition temperature does not exceed 1350 ℃. The density of the deposited layer can be changed by controlling the deposition temperature, so that the density distribution of the loose layer in the liner tube meets the requirement of the equation.
As a preferred technical scheme, the deposition temperature control mode is as follows:
the oxyhydrogen flame temperature is controlled by adjusting the flow of hydrogen and oxygen so that the deposition temperature reaches the set range.
On the other hand, the invention also provides a preparation method of the rare earth doped optical fiber preform based on the in-tube method, which adopts the quartz deposition tube to prepare, and comprises the following steps:
heating and breaking a tail pipe at one end of the quartz deposition tube;
preparing a mixed solution containing rare earth salt and a co-doping agent, injecting the mixed solution into a quartz deposition tube, and fully soaking;
and slowly pouring out the residual solution, drying, dehydrating, oxidizing and shrinking the quartz deposition tube to obtain the uniformly doped rare earth doped preform.
In the process of preparing the quartz deposition tube, the density of the loose layer in the tube is configured to be high at the center and low at the position close to the liner tube, so that the density of the loose layer in the section is gradually distributed, and in the process of soaking the mixed solution, the density of the loose layers is different, so that the rare earth adsorption capacity in the mixed solution is also different; the more the loose layer is close to the center, the more rare earth is adsorbed by the loose layer, so that the more the loose layer is close to the center, the higher the rare earth concentration is, in the subsequent fusion shrinking process, the more the volatilization capacity is stronger at the center, so that the density variation of the loose layer is reasonably designed to be matched with the volatilization degree in the fusion shrinking process, the rare earth concentration on the section of the preform rod is basically uniform after fusion shrinking, the purpose of completely and uniformly achieving in engineering is achieved, and the high-performance optical fiber can be prepared subsequently.
As a preferable technical scheme, the rare earth element of the rare earth salt is selected from one or more of Sc, Y, la, ce, pr, nd, pm, sm, eu, gd, tb, dy, ho, er, tm, yb and Lu.
As a preferable technical scheme, the co-admixture is any one or a combination of a plurality of compounds containing phosphorus, cerium, bismuth and aluminum.
As a preferable technical scheme, the relation between the soaking time C and the loose core layer thickness D of the quartz deposition tube filled with the mixed solution is 2D < C <4D, the unit of C is h, and the unit of D is millimeter.
As a preferable technical scheme, the quartz deposition tube drying and dehydration method comprises the following steps:
nitrogen or inert gas is introduced for purging, and then the first process gas is introduced for drying and dehydration at 600 ℃ to 1000 ℃.
The first process gas is selected according to the rare earth type and the process type, and can be a mixed gas consisting of helium, oxygen and chlorine.
As a preferable technical scheme, the oxidation and fusion shrinkage method comprises the following steps:
introducing a second process gas into the quartz deposition tube at 1600-2200 ℃ for oxidation and shrinkage, wherein the pressure in the tube is controlled at-1000 Pa to 500Pa during shrinkage, and obtaining the rare earth-containing preform.
The second process gas is also selected according to the rare earth type and the process type, and can be helium and oxygen.
As a preferable technical scheme, the core rare earth ion type of the obtained preform is one or more, and the mass content of each doping ion is 300-100000ppm.
On the other hand, the invention also provides a rare earth doped optical fiber preform rod, which is prepared by adopting the preparation method.
On the other hand, the invention provides a rare earth doped optical fiber, which is obtained by sleeving rod drawing or direct drawing on the rare earth doped prefabricated rod prepared by adopting the preparation method.
The rare earth doped preform rod is internally doped with the highly uniform rare earth elements to prepare the optical fiber, so that the rare earth on the optical fiber obtained after drawing is highly uniform, the refractive index of the optical fiber is distributed smoothly on the section, and the optical fiber has the characteristics of high gain, large bandwidth, low noise, polarization insensitivity gain and low introduction loss.
Compared with the prior art, the invention has the beneficial effects that:
the invention solves the problem of uneven rare earth ion distribution of the rare earth doped optical fiber preform by optimizing the powder rod deposition and fusion shrinking process. The invention can utilize the existing solution method equipment in the pipe, and has strong universality and adaptability. The rare earth doped optical fiber perform produced by the method has the advantages that rare earth ions are uniformly distributed in the optical fiber perform, the obtained optical fiber refractive index profile is smooth, and the laser slope efficiency is high.
Drawings
FIG. 1 is a schematic diagram of a structure of a quartz deposition tube according to an embodiment.
Fig. 2 is a graph showing the laser slope efficiency of erbium-ytterbium co-doped fiber obtained by drawing the preform obtained in example 1 and comparative example 1.
FIG. 3 is a graph showing the laser slope efficiency of ytterbium-doped fibers drawn from the preform obtained in example 2 and comparative example 2.
100-quartz deposition tube, 110-liner, 120-loose layer, 130-center.
Detailed Description
For a better understanding of the present invention, the following examples are set forth to illustrate the invention further, but are not to be construed as limiting the invention.
As shown in fig. 1, the present invention provides a quartz deposition tube for preparing an optical fiber preform, comprising a liner tube and a loose layer deposited on the inner wall of the liner tube by an MCVD process, wherein the density of the loose layer is gradually distributed in the radial direction, thereby generating a gradual distribution of doping power to dopants.
Example 1:
preparing a quartz deposition tube with a loose core layer deposited on the inner surface by an MCVD process, preparing a pure silicon liner tube with the outer diameter of 28mm and the inner diameter of 22mm, introducing raw material gases such as silicon tetrachloride, oxygen and the like, controlling oxyhydrogen flame deposition temperature by adjusting the flow of the hydrogen and the oxygen so as to adjust the deposition temperature to reach a set value, wherein the initial deposition temperature is 1225 ℃, the subsequent deposition temperature is gradually increased, the deposition temperature of each layer is increased by 7.5 ℃,11 layers are deposited, the highest deposition temperature is 1300 ℃, and the deposition is sparse along with the change of the deposition temperatureThe density of the loose layer is gradually increased, and finally the parameters of the quartz deposition tube are as follows: the density of the loose layer closest to the inner wall of the liner tube is 0.3g/cm 3 The deposition thickness of the loose layer is 2.2mm, and the density of the loose layer at any position with the distance B from the inner wall of the liner tube is rho=0.3+0.11 x B 2 (g/cm 3 )。
Injecting 0.3L of ethanol solution containing ytterbium chloride, erbium chloride and aluminum chloride into a deposition tube, wherein the content of ytterbium chloride is 0.023mol/L, the content of erbium chloride is 0.015mol/L, the content of aluminum chloride is 0.16mol/L, soaking for 6 hours, pouring out the solution, introducing nitrogen into a quartz liner tube for purging for 3 hours, and then introducing He and O between 650 ℃ and 950 DEG C 2 ，Cl 2 And dehydrating the loose core layer, and finally, shrinking the quartz tube at 1800-2100 ℃ to obtain the erbium-ytterbium co-doped preform, and drawing to obtain the erbium-ytterbium co-doped optical fiber with the specification of 25/300.
Comparative example 1 of example 1:
preparing a quartz deposition tube with a loose core layer deposited on the inner surface by adopting an MCVD process, wherein the deposition thickness of the loose core layer is 2.2mm, and the density of the loose core layer is 0.31g/cm 3 。
Injecting 0.3L of ethanol solution containing ytterbium chloride, erbium chloride and aluminum chloride into a quartz deposition tube, wherein the content of ytterbium chloride is 0.023mol/L, the content of erbium chloride is 0.015mol/L, the content of aluminum chloride is 0.16mol/L, soaking for 6 hours, pouring out the solution, introducing nitrogen into a quartz liner tube for purging for 3 hours, and then introducing He and O between 650 ℃ and 950 DEG C 2 ，Cl 2 And dehydrating the loose core layer, and finally, shrinking the quartz tube at 1800-2100 ℃ to obtain the erbium-ytterbium co-doped preform, and drawing to obtain the erbium-ytterbium co-doped optical fiber with the specification of 25/300.
The erbium-ytterbium ion concentration distribution of the core layer of the two erbium-ytterbium co-doped fibers is shown in table 1, and it can be seen that the erbium-ytterbium co-doped fiber prepared in example 1 has uniform distribution of the erbium-ytterbium ion concentration distribution in comparative example 1.
Table 1 shows comparison of ytterbium ion concentration and erbium ion concentration distribution in example 1 and comparative example 1
Example 1 the laser slope efficiency of erbium ytterbium co-doped fiber obtained by drawing reaches 72.8% (shown in figure 1). The slope efficiency of the fiber laser obtained in comparative example 1 is only 53.1%, and it can be seen that the performance of the fiber can be significantly improved by adopting the erbium-ytterbium co-doped fiber prepared in this example.
Example 2
The same MCVD process as in example 1 was used to prepare a quartz deposition tube with a loose core layer deposited on the inner surface, the parameters of the quartz deposition tube being: the initial deposition temperature is 1215 ℃, the subsequent deposition temperature is gradually increased, the deposition temperature of each layer is increased by 8 ℃,13 layers are deposited, the highest deposition temperature is 1311 ℃, and the density of loose layers closest to the inner wall of the liner tube is 0.28g/cm 3 The deposition thickness of the loose layer is 2.3mm, and the density of the loose layer at any position with the distance B from the inner wall of the liner tube is rho=0.28+0.13 x B 2 (g/cm 3 )。
Injecting 0.3L of ethanol solution containing ytterbium chloride and aluminum chloride into a quartz deposition tube, wherein the ytterbium chloride content is 0.025mol/L, the aluminum chloride content is 0.18mol/L, soaking for 6 hours, pouring out the solution, introducing nitrogen into a quartz liner tube to purge for 3.5 hours, and then introducing He and O between 650 ℃ and 950 DEG C 2 ，Cl 2 And (3) dehydrating the loose core layer, and finally, shrinking the quartz tube at 1800-2100 ℃ to obtain an ytterbium-doped preform, and drawing to obtain the ytterbium-doped optical fiber with the specification of 14/250.
Comparative example 2 of example 2
Preparing a quartz deposition tube with a loose core layer deposited on the inner surface by adopting an MCVD process, wherein the deposition thickness of the loose core layer is 2.3mm, and the density of the loose core layer is 0.30g/cm 3 。
Injecting 0.3L of ethanol solution containing ytterbium chloride and aluminum chloride into a quartz deposition tube, wherein the ytterbium chloride content is 0.025mol/L, the aluminum chloride content is 0.18mol/L, soaking for 6 hours, pouring out the solution, introducing nitrogen into a quartz liner tube to purge for 3.5 hours, and then introducing He and O between 650 ℃ and 950 DEG C 2 ，Cl 2 And (3) dehydrating the loose core layer, and finally, shrinking the quartz tube at 1800-2100 ℃ to obtain an ytterbium-doped preform, and drawing to obtain the ytterbium-doped optical fiber with the specification of 14/250.
The ytterbium ion concentration distribution of the two ytterbium-doped fibers is shown in table 2, and it can be seen that the ytterbium ion concentration distribution of the ytterbium-doped fiber prepared in example 2 is even compared with that of comparative example 2.
Table 2 shows comparison of ytterbium ion concentration and erbium ion concentration distribution of example 2 and comparative example 2
Example 2 drawing resulted in a fiber laser slope efficiency of 75.2% (as shown in fig. 2). The slope efficiency of the fiber laser obtained in comparative example 2 is only 56.6%, and it can be seen that the ytterbium-doped optical fiber preform prepared by the embodiment can obviously improve the optical fiber performance.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and changes can be made by those skilled in the art without departing from the inventive concept and remain within the scope of the invention.
Claims (14)
1. A quartz deposition tube for preparing an optical fiber preform rod is characterized by comprising a liner tube and a loose layer deposited on the inner wall of the liner tube by adopting an MCVD process, wherein the density of the loose layer is gradually distributed in the radial direction, so that the gradual distribution of the adsorption capacity to doped substances is generated.
2. The quartz deposition tube of claim 1, wherein: the closer to the center, the greater the density of the porous layer, the density distribution of the porous layer satisfying the following equation:
ρ＝ρ 0 +A*B 2
ρ is the density of the loose layer at any point ρ 0 The density of the loose layer closest to the inner wall of the liner tube is represented by B, the radial distance between the corresponding point and the inner wall of the liner tube is represented by A, and the gradient coefficient is represented by A.
3. The quartz deposition tube of claim 2, wherein: said ρ and ρ 0 Are all in g/cm 3 ，ρ 0 Is of the value of (2)In the range of 0.275<A<0.55; the unit of the distance B is millimeter, and the value range of the distance B is not more than 2.5; a is a dimensionless parameter, and the value range is 0.05-0.21.
4. A method of preparing a quartz deposition tube according to any of claims 1-3, comprising the steps of:
preparing a liner tube to be deposited, and introducing a raw material gas containing silicon tetrachloride and oxygen into the liner tube for deposition; the deposition temperature is controlled to be gradually increased layer by layer to obtain loose layers with gradually increased density.
5. A process for preparing a tube for quartz deposition as claimed in claim 4, wherein the initial deposition temperature is between 1200 and 1250℃and the subsequent incremental steps of the deposition temperature for each layer are between 5 and 15℃and the maximum deposition temperature is not more than 1350 ℃.
6. A method for preparing a rare earth doped optical fiber preform based on an in-tube method, which is prepared by adopting the quartz deposition tube according to any one of claims 1 to 5, and is characterized in that the preparation method comprises the following steps:
preparing a mixed solution containing rare earth salt and a co-doping agent, injecting the mixed solution into a quartz deposition tube, and fully soaking;
and slowly pouring out the residual solution, drying, dehydrating, oxidizing and shrinking the quartz deposition tube to obtain the uniformly doped rare earth doped preform.
7. The method for preparing a rare earth doped optical fiber preform based on the in-tube method according to claim 6, wherein: the rare earth element of the rare earth salt is selected from one or more of Sc, Y, la, ce, pr, nd, pm, sm, eu, gd, tb, dy, ho, er, tm, yb and Lu.
8. The method for preparing a rare earth doped optical fiber preform based on the in-tube method according to claim 6, wherein: the co-admixture is any one or a combination of a plurality of compounds containing phosphorus, cerium, bismuth and aluminum.
9. The method for preparing a rare earth doped optical fiber preform based on the in-tube method according to claim 6, wherein: the relation between the soaking time C and the loose core layer thickness D of the quartz deposition tube injected with the mixed solution is 2D < C <4D, the unit of C is h, and the unit of D is millimeter.
10. The method for preparing a rare earth doped optical fiber preform based on the in-tube method according to claim 6, wherein: the quartz deposition tube drying and dehydration method comprises the following steps:
nitrogen or inert gas is introduced for purging, and then the first process gas is introduced for drying and dehydration at 600 ℃ to 1000 ℃.
11. The method for preparing a rare earth doped optical fiber preform based on the in-tube method according to claim 6, wherein: the oxidation and fusion shrinkage method comprises the following steps:
introducing a second process gas into the quartz deposition tube at 1600-2200 ℃ for oxidation and shrinkage, wherein the pressure in the tube is controlled at-1000 Pa to 500Pa during shrinkage, and obtaining the rare earth-containing preform.
12. The method for preparing a rare earth doped optical fiber preform based on the in-tube method according to claim 6, wherein: the core rare earth ion type of the obtained preform is one or more, and the mass content of each doped ion is 300-100000ppm.
13. The utility model provides a tombarthite doped optical fiber perform which characterized in that: a preparation method according to any one of claims 6 to 12.
14. A rare earth doped optical fiber, characterized in that the rare earth doped preform prepared by the preparation method according to any one of claims 6 to 12 is drawn by a jacket rod or directly drawn to obtain the rare earth doped optical fiber.
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