CN112441736B - Optical fiber preform, preparation method thereof and plasma deposition equipment - Google Patents
Optical fiber preform, preparation method thereof and plasma deposition equipment Download PDFInfo
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- CN112441736B CN112441736B CN201910816852.0A CN201910816852A CN112441736B CN 112441736 B CN112441736 B CN 112441736B CN 201910816852 A CN201910816852 A CN 201910816852A CN 112441736 B CN112441736 B CN 112441736B
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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
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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]
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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
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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
- C03B37/01853—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
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Abstract
The application provides an optical fiber preform, a preparation method thereof and plasma deposition equipment, wherein fluorine doping distribution of an inner cladding gradual change type is formed by fluorine doping sintering, so that the preparation process difficulty of viscosity matching among a core layer, the inner cladding and an optical cladding can be solved, and particularly the viscosity matching on the boundary between the core layer and the optical cladding is realized; meanwhile, the constraint diffusion distribution of each layer of fluoride in the powder rod is realized, and the refractive index requirement of each layer is ensured; the stress problem of the fluorine-doped layer with large thickness can be effectively solved by synchronously carrying out fluorine-doped deposition and stress relief, and the phenomenon that the thicker the fluorine-doped layer is, the more easily the fluorine-doped layer is cracked is avoided.
Description
Technical Field
The application relates to the technical field of optical communication, in particular to an optical fiber preform, a preparation method thereof and plasma deposition equipment.
Background
In future 400G and above transmission systems, reducing fiber loss and obtaining a large effective area are one of the important issues in the field of fiber manufacturing. For quartz fiber, the attenuation at 600 nm-1600 nm mainly comes from Rayleigh scattering, and the attenuation a caused by Rayleigh scattering R Can be calculated by the following formula: a, a R ＝R/λ 4 +b. Wherein lambda is the wavelength and R is the Rayleigh scattering coefficient (dB/km/μm) 4 ) B is a corresponding constant.
In order to reduce the loss of the optical fiber, the most main process is to reduce the design of germanium doped in the core layer or pure silicon core, and the Rayleigh scattering of the optical fiber can be effectively reduced by reducing the doping concentration of the optical fiber. However, the rayleigh scattering R of the optical fiber is affected by the density fluctuation Rd in addition to the doping concentration Rc. Its expression r=rc+rd. The pure silicon core design adopted in the traditional process is easy to cause viscosity mismatch between the core layer and the cladding layer to cause density fluctuation, and the viscosity match between the core layer and the cladding layer is improved while germanium doping of the core layer is required to be reduced, so that the optical fiber loss can be reduced.
In order to obtain a large effective area, the main method is to reduce the refractive index of the core layer and increase the diameter of the core layer, but simply reduce the refractive index of the core layer and increase the diameter of the core layer, while the effective area of the optical fiber can be increased, the increase of the cut-off wavelength and the degradation of the attenuation and bending performance of the optical fiber are accompanied, so that the optical fiber exceeds relevant indexes. Moreover, if a pure silicon core design mode is adopted, the refractive index of the core layer cannot be reduced.
Disclosure of Invention
In view of the above, it is necessary to provide an ultralow-loss large-effective-area optical fiber preform.
The technical scheme provided by the application is as follows: a method for preparing an optical fiber preform, comprising the steps of:
sequentially forming a core layer, an inner cladding layer and an optical cladding layer which are mainly composed of silicon dioxide to obtain a powder rod, wherein the core layer further comprises germanium dioxide generated by reaction;
sequentially carrying out three stages of dehydroxylation, sintering and vitrification on the powder rod to form a glass rod with constrained diffusion of fluoride in a core layer, an inner cladding layer and an optical cladding layer, wherein fluoride gas is introduced from the sintering stage and the flow rate of the fluoride gas is linearly increased, and then the powder rod enters the vitrification stage, and the flow rate of the fluoride gas is gradually reduced until the vitrification stage is completed and becomes zero;
extending the glass rod to a target radius, and depositing a fluorine-doped layer on the surface layer of the glass rod by adopting a plasma deposition process and a stress relief process to obtain a fluorine-doped glass rod;
and forming an outer cladding layer on the outer layer of the fluorine-doped glass rod to obtain the transparent optical fiber preform.
Further, in the step of sequentially subjecting the powder rod to three stages of dehydroxylation, sintering, and vitrification to form a glass rod in which fluoride is diffusion-restricted in the core layer, the inner cladding layer, and the optical cladding layer, the content of fluoride in the glass rodThe amount of fluoride in the inner cladding layer increases gradually from the outer layer of the core layer to the inner layer of the optical cladding layer; the fluoride comprises SiF 4 、CF 4 、SF 6 、C 2 F 6 、SOF 2 、C 2 F 2 Cl 2 Or a combination of at least two thereof.
Further, the temperature in the dehydroxylation stage is controlled between 1200 and 1250 ℃; entering a sintering stage, taking the temperature of the dehydroxylation stage as an initial temperature, and raising the temperature to 1320-1450 ℃ at a heating rate of 0.5-5 ℃/min, wherein the fluoride gas is linearly increased at a flow rate of 5-25 cc/min until the sintering stage is finished; and (3) entering a vitrification stage, and keeping the temperature at the end of a sintering stage for 1-3 hours.
Further, in the step of sequentially forming a core layer, an inner cladding layer and an optical cladding layer which are mainly composed of silicon dioxide to obtain the powder rod, wherein the core layer further comprises germanium dioxide generated by reaction, the reaction gas for forming the core layer comprises oxygen, hydrogen, silicon tetrachloride, germanium tetrachloride and Ar gas, and the introducing flow rate of the germanium tetrachloride is controlled to be 50-200cc/min.
Further, in the step of sequentially forming a core layer, an inner cladding layer and an optical cladding layer which are mainly composed of silicon dioxide to obtain a powder rod, wherein the core layer further comprises germanium dioxide generated by reaction, the reaction gas for forming the inner cladding layer comprises oxygen, hydrogen, silicon tetrachloride and Ar gas, the introducing flow of the silicon tetrachloride is controlled to be 4 g/min-12 g/min, and the density of silicon dioxide powder generated by reaction is controlled to be 0.5-1.5 g/cm 3 The thickness of the inner cladding is 1/2-1/8 of the radius of the core.
Further, in the step of sequentially forming a core layer, an inner cladding layer and an optical cladding layer which are mainly composed of silicon dioxide to obtain a powder rod, wherein the core layer further comprises germanium dioxide generated by reaction, the reaction gas for forming the optical cladding layer comprises oxygen, hydrogen, silicon tetrachloride and Ar gas, the inflow rate of the silicon tetrachloride is controlled to be 20 g/min-40 g/min, and the germanium dioxide generated by reactionThe density of the silicon powder is controlled to be 0.2-0.6 g/cm 3 The total thickness of the optical cladding and the inner cladding is 0.5 to 5.0 times the radius of the core.
Further, in the step of extending the glass rod to a target radius and depositing a fluorine-doped layer on the surface layer of the glass rod by adopting a plasma deposition process and a stress relief process to obtain the fluorine-doped glass rod, the plasma deposition process sprays fluorine-containing gas back and forth on the surface of the glass rod through a POD (point of sale) blast lamp, and the fluorine-containing gas is deposited layer by layer; the fluorine-containing gas comprises silicon tetrachloride, oxygen and fluoride; the fluoride comprises SiF 4 、CF 4 、SF 6 、C 2 F 6 、SOF 2 、C 2 F 2 Cl 2 One or a combination of at least two of the following; the stress relief process is to spray mixed gas of oxygen and nitrogen in the same direction at the side of the fluorine-containing gas when spraying the fluorine-containing gas so as to relieve the stress of the glass.
Further, the translation speed variable DeltaV of the POD blast lamp is-0.1 to-0.3 m/min; the deposition thickness variable DeltaC is 5-10 mm, the initial translation speed is 1m/min, the initial rod diameter is 30mm, and the lowest translation speed is not lower than 0.1m/min.
Further, the step of forming the outer cladding layer on the outer layer of the fluorine-doped glass rod to obtain the transparent optical fiber preform comprises the steps of depositing the outer cladding layer on the outer layer of the fluorine-doped glass rod by adopting a vapor deposition process, and then sintering to obtain the transparent optical fiber preform.
Further, the step of forming an outer cladding layer on the outer layer of the fluorine-doped glass rod to obtain a transparent optical fiber preform comprises the step of directly filling the fluorine-doped glass rod into a silicon dioxide sleeve to assemble the optical fiber preform.
The application also provides an optical fiber preform, which is formed by adopting the preparation method of the optical fiber preform, wherein the optical fiber preform sequentially comprises the following components in a coaxial arrangement from inside to outside:
the radius of the middle core layer is 4-6 mu m, and the refractive index of the middle core layer relative to silicon dioxide is 0.15-0.25%;
the inner structure cladding has a radius of 4.5-7.5 mu m, and the refractive index of the inner structure cladding relative to silicon dioxide is graded;
the optical structure layer has a radius of 10-25 mu m and a refractive index of-0.05 to-0.25% relative to silicon dioxide;
the radius of the fluorine-doped structural layer is 20-30 mu m, and the refractive index of the fluorine-doped structural layer relative to silicon dioxide is-0.4 to-0.6 percent;
the outer cladding has a radius of 60 μm or more and a refractive index of 0.
The application further relates to plasma deposition equipment for forming a fluorine-doped layer on the surface layer of a glass rod by deposition, wherein the equipment comprises a POD (point of sale) spray lamp group, the POD spray lamp group comprises a main spray lamp and a plurality of destressing spray lamps, which are arranged side by side, and the main spray lamp is used for spraying and depositing introduced silicon tetrachloride, oxygen and fluoride on the surface layer of the glass rod; the destressing blast lamp is used for introducing oxygen and nitrogen to remove glass stress.
Further, the POD torch set includes two the destressing torches, two the destressing torches are located the both sides of main torch, and the export of this three torches is consistent apart from the interval of glass stick along translation direction setting side by side.
Further, the distance from the outlet of the main burner or the destressing burner to the surface of the glass rod is not greater than the height of the jet flame.
Further, the distance from the outlet of the main burner or the destressing burner to the surface of the glass rod is half of the height of the jet flame.
Further, the axial distance between the main burner and the destressing burner is less than or equal to half of the sum of the widths of the two spray flames.
Furthermore, a plurality of pipelines are arranged in the main blast lamp side by side, and the pipelines are used for respectively introducing silicon tetrachloride, oxygen and fluoride to react to form deposited fluorine-doped silicon dioxide powder; a plurality of pipelines are arranged in the destressing blast lamp and are used for introducing oxygen and nitrogen.
Compared with the prior art, the application can solve the preparation process difficulty of viscosity matching among the core layer, the inner cladding and the optical cladding through the graded fluorine doping distribution of the inner cladding, in particular to viscosity matching on the boundary between the core layer and the optical cladding; meanwhile, the constraint diffusion distribution of each layer of fluoride in the powder rod is realized, and the refractive index requirement of each layer is ensured; the stress problem of the fluorine-doped layer with large thickness can be effectively solved by synchronously carrying out fluorine-doped deposition and stress relief, and the phenomenon that the thicker the fluorine-doped layer is, the more easily the fluorine-doped layer is cracked is avoided.
Drawings
The application will be described in further detail with reference to the drawings and the detailed description.
Fig. 1 is a flowchart illustrating a preparation process of an optical fiber preform according to an embodiment of the present application.
FIG. 2 is a schematic view of a powder rod deposition apparatus employed in the present application.
Fig. 3 is a schematic end view of the upper deposition chamber shown in fig. 2.
FIG. 4 is a cross-sectional view of fluorine doping amount and refractive index of each layer of the glass rod of the present application.
FIG. 5 is a schematic diagram of the furnace temperature control at the sintering stage of the present application.
FIG. 6 is a schematic view of fluorine doping control during the process of dehydroxylation, sintering and vitrification of the powder rod of the present application.
Fig. 7 is a schematic view of a structure of a plasma deposition apparatus according to the present application.
Fig. 8 is a schematic cross-sectional structure of an optical fiber preform according to the present application.
Fig. 9 is a schematic view of refractive index profile of an optical fiber preform according to the present application.
FIG. 10 is a schematic view showing fluctuation of the rod diameter of the powder rod in different air inlet modes.
Fig. 11 is a graph showing attenuation performance test of the optical fiber under different air intake modes.
Reference numerals illustrate:
powder rod deposition apparatus 10
Core layer torch 101
Inner cladding torch 102
Optical cladding torch 103
Deposition chamber 104
Boom 105
Target 106
Powder rod 107
Upper deposition chamber 108
Upper deposition chamber inner layer 108a
Upper deposition chamber outer layer 108b
Upper deposition chamber end cap 108c
Plasma deposition apparatus 30
Glass rod 301
POD (point of sale) spray lamp group 303
Main burner 3031
First destressing torch 3032
Second destressing torch 3033
Optical fiber preform 50
Intermediate core layer 501
Inner structural cladding 503
Optical structure layer 505
Fluorine doped structural layer 507
Outer cladding 509
The following detailed description will further illustrate embodiments of the application in conjunction with the above-described drawings.
Detailed Description
In order that the above-recited objects, features and advantages of embodiments of the present application can be more clearly understood, a more particular description of the application will be rendered by reference to the appended drawings and appended detailed description. The features of the embodiments of the present application may be combined with each other without collision.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the application, and the described embodiments are merely some, rather than all, of the embodiments of the application. All other embodiments, based on the embodiments of the application, which are obtained by a person of ordinary skill in the art without making any inventive effort, are within the scope of the embodiments of the application.
By "stress" is meant herein the stress caused by micro-non-uniform regions formed by non-uniformity of composition, also known as structural stress or microscopic stress.
Herein, "POD" refers to plasma external phase deposition, english full: plasma outside deposition, POD for short.
Herein, "VAD" refers to axial vapor deposition, the english language being fully defined: vapor Axial Deposition, VAD for short.
Herein, "OVD" refers to an outside vapor deposition method, english is fully: outside Vapour Deposition, OVD for short.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the application belong. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
Referring to fig. 1, a flowchart of an optical fiber preform preparation process according to an embodiment of the application includes the following steps:
step S1: sequentially forming a core layer r01, an inner cladding layer r02 and an optical cladding layer r03 which are mainly composed of silicon dioxide, and obtaining a powder rod, wherein the core layer further comprises germanium dioxide generated by reaction.
In a specific embodiment, the reaction gas for forming the core layer comprises oxygen, hydrogen, silicon tetrachloride, germanium tetrachloride and Ar gas, wherein the introducing flow rate of the germanium tetrachloride is controlled to be 50-200cc/min. The reaction gas for forming the inner cladding comprises oxygen, hydrogen, silicon tetrachloride and Ar gas, wherein the introducing flow of the silicon tetrachloride is controlled to be 4 g/min-12 g/min, and the density of silicon dioxide powder generated by the reaction is controlled to be 0.5-1.5 g/cm 3 The thickness of the inner cladding is 1/2 to 1/8 of the radius of the core, i.e., (r 02-r 01)/r 01. The reaction gas for forming the optical cladding comprises oxygen, hydrogen, silicon tetrachloride and Ar gas, wherein the introducing flow of the silicon tetrachloride is controlled to be 20 g/min-40 g/min, and the density of silicon dioxide powder generated by the reaction is controlled to be 0.2-0.6 g/cm 3 The total thickness of the optical cladding and the inner cladding is 0.5 to 5.0 times the radius of the core, i.e. (r 03-r 01)/r 01, preferably 1.5 to 3.0 times. In the step, the reaction gas can be respectively introduced or mixed gas is introduced, the raw materials react in flame at high temperature to generate silicon dioxide particles or germanium dioxide and silicon dioxide particles,for example, the flow ratio of oxygen, hydrogen, silicon tetrachloride, germanium tetrachloride and Ar gas can be (1-3): (2-5): 3 (0.15-0.3): 1-1.5), and the flow ratio of oxygen, hydrogen, silicon tetrachloride and Ar gas can be (1-3): 3:3 (1-1.5); the method is characterized in that the thickness and the density of the deposited inner cladding and the optical cladding are optimally designed, powder layer combinations distributed in different density areas are realized, the components of each powder layer are similar, the core layer is doped as little as possible, the matching degree of each powder layer after viscosity regulation in the sintering process is high, the density fluctuation is not easy to be caused, and the near-pure silicon core design or the low germanium doped core layer design is achieved, so that Rayleigh scattering is reduced, and the loss of the final optical fiber is reduced.
Step S2: and sequentially carrying out three stages of dehydroxylation, sintering and vitrification on the powder rod to form a glass rod with constrained diffusion of fluoride in the core layer, the inner cladding layer and the optical cladding layer, wherein fluoride gas is introduced from the sintering stage and the flow rate of the fluoride gas is linearly increased, and then the powder rod enters the vitrification stage, and the flow rate of the fluoride gas is gradually reduced until the vitrification stage is completed and becomes zero. The fluoride gas is SiF 4 、CF 4 、SF 6 、C 2 F 6 、SOF 2 、C 2 F 2 Cl 2 Or a combination of at least two gases.
Referring to fig. 4, on the basis of the optimal design of thickness and density, the content of fluoride in the glass rod is the least in the core layer, the most and uniformly distributed in the optical cladding layer, and the content of fluoride in the inner cladding layer gradually increases from the content of fluoride in the outer layer of the core layer to the content of fluoride in the inner layer of the optical cladding layer, thereby realizing the constrained diffusion of fluoride in the core layer, the inner cladding layer and the optical cladding layer; meanwhile, the problem that the refractive index of the core layer is reduced due to the fact that the fluoride is not controlled to diffuse into the core layer in a large amount is avoided, and the refractive index requirements of the core layer and the optical cladding layer are affected. The fluoride comprises SiF 4 、CF 4 、SF 6 、C 2 F 6 、SOF 2 、C 2 F 2 Cl 2 Or a combination of at least two thereof.
Referring to fig. 5 and 6 together, the temperature is controlled between 1200 ℃ and 1250 ℃ in the dehydroxylation stage; entering a sintering stage, taking the temperature of the dehydroxylation stage as an initial temperature, and raising the temperature to 1320-1450 ℃ at a heating rate of 0.5-5 ℃/min, wherein the fluoride gas is linearly increased at a flow rate of 5-25 cc/min until the sintering stage is finished; and (3) entering a vitrification stage, and keeping the temperature at the end of a sintering stage for 1-3 hours.
The fluorine doping requirement in the optical cladding and the gradual change distribution of the fluoride of the inner cladding are realized through the process, a good transitional effect is achieved between the core layer and the optical cladding, and the viscosity between the core layer and the outer optical cladding at the center is effectively matched. The traditional ultralow-loss large-effective-area optical fiber adopts a sinking auxiliary design method, and the energy distribution in the optical fiber is Gaussian distribution.
Step S3: and (3) extending the glass rod to a target radius, and depositing a fluorine-doped layer on the surface layer of the glass rod by adopting a plasma deposition process and a stress relief process to obtain the fluorine-doped glass rod.
Referring to fig. 7, in a specific embodiment, the plasma deposition process sprays fluorine-containing gas back and forth on the surface of the glass rod through a POD torch, and deposits layer by layer; the fluorine-containing gas comprises silicon tetrachloride, oxygen and fluoride; the fluoride comprises SiF 4 、CF 4 、SF 6 、C 2 F 6 、SOF 2 、C 2 F 2 Cl 2 One or a combination of at least two of the following; the destressing process is that when the fluorine-containing gas is sprayed, a pipeline is arranged on the side of the disk of the POD blast lamp, which sprays the fluorine-containing gas, and the outlet of the pipeline is sprayed with the mixed gas of oxygen and nitrogen in the same direction so as to eliminate the stress of glass. The translation speed variable DeltaV of the POD blast lamp is-0.1 to-0.3 m/min; the deposition thickness variable DeltaC is 5-10 mm, the initial translation speed is 1m/min, the initial rod diameter is 30mm, and the lowest translation speed is not lower than 0.1m/min. Through the POD non-constant speed deposition and the on-line stress relief process, the phenomenon that the POD preparation fluorine-doped layer with large thickness is easy to crack due to stress concentration can be eliminated. The method comprisesThe design of the deep fluorine-doped concave layer is beneficial to improving the bending resistance of the optical fiber.
Step S4: and forming an outer cladding layer on the outer layer of the fluorine-doped glass rod to obtain the transparent optical fiber preform.
In a specific embodiment, in the step S4, an outer cladding layer is deposited on the outer layer of the fluorine-doped glass rod by adopting a vapor deposition process, and then the transparent optical fiber preform is obtained through sintering. In the step S4, the fluorine-doped glass rod can be directly arranged in a silicon dioxide sleeve to be assembled into an optical fiber preform.
As shown in fig. 8 and 9, the optical fiber preform 50 molded by the above-mentioned manufacturing method comprises, in order from inside to outside, coaxially disposed:
the intermediate core layer 501 has a radius r1=4 to 6 μm and a refractive index Δn1 with respect to silica of 0.15 to 0.25%;
inner structural cladding 503, having a radius r2=4.5 to 7.5 μm, has a graded refractive index Δn2 with respect to silica;
the optical structure layer 505 has a radius r3=10 to 25 μm and a refractive index Δn3 with respect to silica of-0.05 to-0.25%;
the fluorine doped structural layer 507 has a radius r4=20-30 μm and a refractive index delta n4 of-0.4 to-0.6% relative to silicon dioxide;
the outer cladding 509 has a radius r5 of 60 μm or more and a refractive index Deltan 5 of 0.
The powder rod deposition apparatus 10 employed in step S1 of the present application will be described in detail with reference to fig. 2.
The apparatus includes a target rod 106, a deposition chamber 104, an optical cladding torch 103, an inner cladding torch 102, a core torch 101, a hanger rod 105, and an upper deposition chamber 108. Wherein, the upper part of the deposition chamber 104 is provided with an upper deposition cavity 108, a hanging rod 105 is arranged in the upper deposition cavity 108, the hanging rod 105 is provided with a hook, the hanging rod 105 is connected with a lifting mechanism, a target rod 106 is hung on the hook of the hanging rod 105 connected with the lifting mechanism, one side of the lower part of the deposition chamber 104 is provided with an optical cladding layer blast lamp 103, an inner cladding layer blast lamp 102 and a core layer blast lamp 101 in sequence, and the blast lamps (103, 102 and 101) spray air flow towards the target rod 106, so that powder is formed by layer-by-layer reaction and is adhered on the target rod 106. In the specific embodiment, the upper deposition chamber 108 has an inner chamber and an outer chamber, i.e., an upper deposition chamber inner layer 108a and an upper deposition chamber outer layer 108b, and an upper deposition chamber end cap 108c (shown in fig. 3) is provided at the end thereof. The upper deposition chamber outer layer 108b is mainly filled with external air, the upper deposition chamber inner layer 108a is mainly used for accommodating the powder rod lifting space, and the upper deposition chamber end cover 108c is used for sealing the powder rod accommodating space to prevent air flow from entering. So divide into inside and outside two rooms with upper portion deposit cavity 108, effectively with powder stick accommodation space and gas admission cavity separation, avoid along with the increase of powder stick diameter, the space that is used for the gas to pour in the upper portion deposit cavity reduces and the cavity pressure fluctuation that arouses, causes the stick diameter of powder stick to produce the fluctuation, and the stick diameter fluctuation of powder stick can effectively be improved to above-mentioned structural design.
Deposition process of powder rod: oxygen, hydrogen, silicon tetrachloride, germanium tetrachloride and Ar gas are introduced into the core layer blowtorch 101, and silicon dioxide and germanium dioxide are formed through high-temperature reaction and attached to the end face of the target rod, so that a loose core layer with certain density is formed. The silica layer with a certain thickness surrounding the surface of the core layer is an inner cladding, and oxygen, hydrogen, silicon tetrachloride and Ar gas are introduced into the inner cladding torch 102. The silicon dioxide layer with a certain thickness surrounding the surface of the inner cladding is an optical cladding, oxygen, hydrogen, silicon tetrachloride and Ar gas are introduced into the optical cladding blowtorch 103, and the deposition is stopped after the powder is deposited to a set length. In the process of introducing, the purposes of controlling the thickness and the density of the inner cladding and the optical cladding can be achieved by controlling the flow rate of silicon tetrachloride, the flow rate ratio of hydrogen and oxygen and the like of the inner cladding and the optical cladding blowlamps (102 and 103).
The plasma deposition apparatus 30 employed in step S3 of the present application will be described in detail with reference to fig. 7.
The apparatus 30 is used for depositing and forming a fluorine-doped layer on the surface layer of a glass rod 301, and comprises a POD (point of view) spray lamp group 303 and a POD (point of view) machine (not shown) for bearing the glass rod, wherein the POD machine regulates the glass rod to rotate around a glass rod shaft; the POD burner group 303 includes a main burner 3031 and a plurality of destressing burners that are arranged side by side, wherein the main burner 3031 is used for spraying and depositing introduced silicon tetrachloride, oxygen and fluoride on the surface layer of the glass rod, and can spray in a reciprocating manner; the destressing blast lamp is used for introducing oxygen and nitrogen to remove glass stress. The different airflows can be arranged in the blowtorch and provided with a single pipeline or a single pipeline, or a plurality of airflows are led in by adopting the same pipeline or pipeline. As shown in fig. 7, the glass rod is horizontally clamped in the plasma deposition apparatus 30, the underside of the apparatus 30 is provided with 3 POD torches side by side, namely a first destressing torch 3032, a main torch 3031 and a second destressing torch 3033, the three torches (3032, 3031 and 3033) can horizontally translate synchronously, the distance between the outlets of the three torches and the surface of the glass rod is consistent, the distance between the outlet of the POD torch group and the surface of the glass rod is not more than the height of the sprayed flame, preferably is half of the height of the sprayed flame, and the axial distance between the destressing torch and the main torch is not more than half of the sum of the widths of the sprayed flames of the two, namely the sprayed flames of the adjacent torches overlap. In other embodiments, the number of POD torches is not limited to 3, and the number of destressing torches may be 1 or 2 or more; the distances between the outlets of the plurality of blowlamps and the glass rod are set according to the technological parameters, and are not limited to be the same; the deposition equipment can be vertically arranged or obliquely clamped, and only the powder can be deposited on the surface layer by the blowtorch, so that the deposition equipment is not limited and needs to be set according to actual process requirements and product performance requirements.
And (3) a fluorine-doped layer deposition process: as shown in fig. 7, a glass rod 301 is placed on a POD machine, and a POD burner set 303 is sprayed back and forth on the rod surface for layer-by-layer deposition. SiCl is introduced into a main burner 3031 in the burner group 303 4 、O 2 Fluoride, forming a fluorine-containing glass layer, forming deep fluorine-doped concave layers with different depths according to fluorine-doped design flow, wherein the design of the deep fluorine-doped concave layers is beneficial to improving the bending resistance of the optical fiber. O is respectively introduced into the first destressing blast lamp 3032 and the second destressing blast lamp 3033 at two sides 2 、N 2 For removing glass stresses. The translation speed variable DeltaV of the POD blast lamp is-0.1 to-0.3 m/min; the deposition thickness variable DeltaC is 5-10 mm, the initial translation speed is 1m/min, the initial rod diameter is 30mm, and the lowest translation speed is not lower than 0.1m/min. Non-constant deposition and on-line destressing by PODThe process can eliminate the phenomenon that the POD is easy to crack due to stress concentration of the fluorine-doped layer with large thickness.
The process of forming the optical fiber preform 50 by the method of the present application and the performance thereof are compared with each other by combining specific examples and comparative examples.
Example 1:
firstly, preparing a core layer, an inner cladding layer and an optical cladding layer by adopting a VAD vapor deposition process, and introducing GeCl into the core layer in the deposition process 4 The flow rate of the gas is controlled to be 50cc/min; siCl in inner cladding 4 The flow rate is controlled to be 4g/min, and the powder density is controlled to be 1.3g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the SiCl in optical cladding 4 The flow rate is controlled to be 20g/min, and the powder density is controlled to be 0.6g/cm 3 。
And (3) carrying out dehydroxylation, sintering and vitrification treatment on the deposited powder rod in a sintering furnace. Firstly, controlling the dehydroxylation temperature T1 at 1200 ℃; after the dehydroxylation is finished, the temperature is increased to 1320 ℃ at a heating rate of 1 ℃/min (T2) and CF is introduced at the same time 4 The gas is linearly increased at a flow rate of 5cc/min until the sintering phase is finished; after the temperature is increased to the temperature T2, the glass is subjected to vitrification constant temperature stage for 1h, the powder rod is further sintered into a transparent glass body, and the fluorine doping flow is gradually reduced to zero along with the time.
And extending the prepared glass rod to a target rod diameter, and then depositing a deep fluorine-doped concave layer by a plasma deposition Process (POD). And placing the glass rod on a POD machine, spraying the POD blast lamp back and forth on the surface of the glass rod, and depositing layer by layer. SiCl is introduced into a main blast lamp in the blast lamp group 4 、O 2 、CF 4 Forming a fluorine-containing glass fluorine-doped layer, introducing O into the destressing blowlamp at two sides 2 、N 2 For removing glass stress. The initial speed is 1m/min, the initial glass rod diameter is 30mm, when the rod diameter is 35mm, the translation speed of the blast lamp set is controlled to be 0.9m/min, the translation speed is reduced by 0.1m/min according to each 5mm thickness increase, the lowest translation speed is not lower than 0.1m/min, and the like until the diameter reaches the target rod diameter of 58mm.
And (3) depositing a pure silicon outer cladding layer by adopting an OVD (over-the-counter (open-flow) gas phase synthesis process on the fluorine-doped glass rod, after reaching the target weight or rod diameter, ending the deposition, sintering, and preparing the powder rod into a transparent glass rod, thereby completing the low-loss large-effective-area optical fiber preform 50.
Refractive index profile characteristics: intermediate core layer 501: Δn1=0.16%, r1=4.2 μm; inner structural cladding 503 is a fluorine doped transition region, r2=5.6 μm; optical structural layer 505: Δn3= -0.20%, r3=12 μm; a fluorine doped structural layer (hereinafter also referred to as a deep fluorine doped recessed layer) 507: Δn4= -0.42%, r4=28 μm; the outer cladding 509 is a pure silicon dioxide layer. Since the overclad 509 may also be formed by a sleeve process, both the deposited overclad and the overclad of the sleeved quartz tube before and after uniform sintering are the overclad 509.
The diameter (diameter) of the optical fiber preform rod can reach 122mm (2 r 5). After fiber drawing, test results: effective area of optical fiber=128 μm 2 The 1550nm attenuation is 0.173dB/km, when the bending radius R=10mm×1 circle, the 1550nm bending loss and the 1625nm bending loss are respectively 0.08dB, 0.18dB, and the cable wavelength 1470nm.
Example 2:
firstly, preparing a core layer, an inner cladding layer and an optical cladding layer by adopting a VAD vapor deposition process, and introducing GeCl into the core layer in the deposition process 4 The flow rate of the gas is controlled to be 100cc/min; siCl in inner cladding 4 The flow rate is controlled to be 8g/min, and the powder density is controlled to be 0.9g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the SiCl in optical cladding 4 The flow rate is controlled to be 30g/min, and the powder density is controlled to be 0.4g/cm 3 。
And (3) carrying out dehydroxylation, sintering and vitrification treatment on the deposited powder rod in a sintering furnace. Firstly, controlling the dehydroxylation temperature T1 at 1200 ℃; after the dehydroxylation is completed, the temperature is raised to 1400 ℃ at a heating rate of 3 ℃/min (T2) and SiF is simultaneously used 4 The gas is linearly increased at a flow rate of 12cc/min until the sintering phase is finished; after the temperature is raised to 1400 ℃, the glass is vitrified for 2 hours at constant temperature, the powder rod is further sintered into transparent glass body, and the fluorine doping flow is gradually reduced to zero along with the time.
And extending the prepared glass rod to the target rod diameter, and then depositing a fluorine-doped layer (namely a deep fluorine-doped concave layer) by a plasma deposition Process (POD). Placing the glass rod on a POD machine, spraying a POD blast lamp back and forth on the surface of the glass rod, and depositing layer by layer. SiCl is introduced into a main blast lamp in the blast lamp group 4 、O 2 、SiF 4 Forming a fluorine-containing glass fluorine-doped layer, introducing O into the destressing blowlamp at two sides 2 、N 2 For removing glass stress. The initial speed is 0.9m/min, the initial glass rod diameter is 35mm, when the rod diameter is 43mm, the translation speed of the blast lamp set is controlled to be 0.7m/min, the translation speed is reduced by 0.2m/min according to 8mm of increased thickness, the lowest translation speed is not less than 0.1m/min, and the diameter reaches 55mm of the target rod diameter by analogy.
The fluorine-doped glass rod is extended to a target rod diameter and assembled with a pure silica quartz glass sleeve, so that the low-loss large-effective-area optical fiber preform 50 is formed.
Refractive index profile characteristics: intermediate core layer 501: Δn1=0.21%, r1=5.0 μm; inner structural cladding 503 is a fluorine doped transition region, r2=6.2 μm; optical structure cladding 505: Δn3= -0.15%, r3=16 μm; fluorine doped structural layer 507: Δn4= -0.47%, r4=25 μm; outer cladding 509: is a pure silicon dioxide layer.
The diameter of the optical fiber preform rod can reach 125mm. After fiber drawing, test results: effective area of optical fiber=123 μm 2 The 1550nm attenuation is 0.169dB/km, when the bending radius R=10mm×1 circle, the 1550nm bending loss and the 1625nm bending loss are respectively 0.06dB and 0.15dB, and the cable wavelength is 1510nm.
Example 3:
firstly, preparing a core layer, an inner cladding layer and an optical cladding layer by adopting a VAD vapor deposition process, and introducing GeCl into the core layer in the deposition process 4 The flow rate of the gas is controlled to be 150cc/min; siCl in inner cladding 4 The flow rate is controlled to be 12g/min, and the powder density is controlled to be 0.6g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the SiCl in optical cladding 4 The flow rate is controlled to be 40g/min, and the powder density is controlled to be 0.25g/cm 3 。
And (3) carrying out dehydroxylation and vitrification sintering on the deposited powder rod in a sintering furnace. Firstly, controlling the dehydroxylation temperature T1 at 1250 ℃; after the dehydroxylation is completed, the temperature is raised to 1450 ℃ at a heating rate of 5 ℃ per minute (T2) while SF is being applied 6 The gas is linearly increased at a flow rate of 20cc/min until the sintering phase is finished; after the temperature is raised to 1450 ℃, sintering is finished, the glass is put into a vitrification constant temperature stage for 3 hours,the powder rod is further sintered into transparent glass body, and the fluorine doping flow rate is gradually reduced to zero along with the time.
And extending the prepared glass rod to a target rod diameter, and then depositing a deep fluorine-doped concave layer by a plasma deposition Process (POD). And placing the glass rod on a POD machine, spraying the POD blast lamp back and forth on the surface of the glass rod, and depositing layer by layer. SiCl is introduced into a main blast lamp in the blast lamp group 4 、O 2 、SF 6 Forming a fluorine-containing glass layer, introducing O into the destressing blowlamp at two sides 2 、N 2 For removing glass stress. The initial speed is 0.8m/min, the initial glass rod diameter is 40mm, when the rod diameter reaches 50mm, the translation speed of the blast lamp set is controlled to be 0.5m/min, the translation speed is reduced by 0.3m/min according to 10mm of thickness increase, the lowest translation speed is not less than 0.1m/min, and the diameter reaches 60mm of the target rod diameter by analogy.
And (3) depositing a pure silicon outer cladding layer by adopting an OVD (over-the-counter (open-glass) gas phase synthesis process on the fluorine-doped glass rod, after reaching the target weight or rod diameter, ending the deposition, and sintering to prepare a transparent glass rod, namely, completing the low-loss large-effective-area optical fiber preform 50.
Refractive index profile characteristics: intermediate core layer 501: Δn1=0.24%, r1=6.0 μm; inner structural cladding 503 is a fluorine doped transition region, r2=7.3 μm; optical structural layer 505: Δn3= -0.08%, r3=20 μm; deep fluorine doped recesses 507: Δn4= -0.54%, r4=30 μm; the outer cladding 509 is a pure silicon dioxide layer.
The diameter of the optical fiber preform rod can reach 135mm. After fiber drawing, test results: effective area of optical fiber=114 μm 2 The 1550nm attenuation is 0.171dB/km, when the bending radius R=10mm×1 circle, the 1550nm bending loss and the 1625nm bending loss are respectively 0.04dB, 0.09dB and the cable wavelength is 1525nm.
Comparative example 1:
the preparation process and parameter settings of this example were essentially the same as in example 3, except that: in step S1, a conventional VAD vapor deposition chamber is used for deposition, i.e. a gas flow enters the lower chamber from the upper powder chamber, and is co-located with the powder. Introducing GeCl into the core layer in the deposition process 4 The flow rate of the gas is controlled to be 150cc/min; siCl in inner cladding 4 Flow controlAt 12g/min, the powder density was controlled at 0.58g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the SiCl in optical cladding 4 The flow rate is controlled to be 40g/min, and the powder density is controlled to be 0.26g/cm 3 。
For powder bars formed in different air intake modes, we performed preparation of multiple groups of samples under the process conditions of example 3 and comparative example 1, and tested the thickness of the optical cladding and the inner cladding in each sample with the multiplying power of the bar diameter of the respective core layer, wherein the bar diameters of all the core layers were identical, as shown in fig. 10. The graph shows that the rod diameter of the powder rod adopting the air inlet mode is basically consistent, the result of 22 groups of samples is maintained between 2.3 and 2.4 times, and the fluctuation is small; by adopting the conventional air inlet mode of comparative example 1, the diameter of the powder rod has large fluctuation and the range is 2.5 + Multiple to 2.1 + The samples were not equal between the times, 15 samples were less than 2.3 times, and 7 samples were more than 2.3 times, which was very unstable. Therefore, the result shows that the air inlet mode of the application is helpful to reduce the fluctuation of the rod diameter of the powder rod, and the design and control of the thickness and the density are easier to realize.
Refractive index profile characteristics: intermediate core Δn1 '=0.24%, r1' =6.1 μm; the inner structure cladding is a fluorine doped transition region, r2' =7.3 μm; optical structure cladding Δn3 '= -0.08%, r3' =20μm; deep fluorine doped recessed layer Δn4 '= -0.54%, r4' = 22 μm; the outer cladding is a pure silicon dioxide layer.
The diameter of the optical fiber preform rod can reach 135mm. After fiber drawing, test results: effective area of optical fiber=114 μm 2 The 1550nm attenuation is 0.172dB/km, when the bending radius R=10mm×1 circle, the 1550nm bending loss and the 1625nm bending loss are respectively 0.05dB and 0.105dB, and the cable wavelength is 1520nm.
For fibers shaped in different modes of air intake, we also compare the attenuation at 1550nm, as shown in FIG. 11. The results in the graph show that the attenuation of the 22 sets of samples of example 3 is substantially between 0.165 and 0.175dB/km, more precisely between 0.168 and 0.172 dB/km. The 22 groups of comparative example 1 had an attenuation of up to 0.185dB/km or more, a minimum of about 0.168dB/km, a mean value greater than that of example 3, poor reproducibility of the samples, and poor yield. It can be seen that the air inlet mode has an influence on the attenuation of the optical fiber, and the constant ratio among the core layer, the inner cladding layer and the optical cladding layer in the core rod can be realized through the deposition airflow control of the powder rod, so that the attenuation longitudinal instability caused by the longitudinal fluctuation of the core rod is avoided.
Comparative example 2:
based on the preparation process of examples 2, 3, the effect of the destressing torch on the glass rod body cracking at a constant speed by turning off the main torch in the plasma deposition Process (POD) was compared. The results are shown in the following table:
from the table, when the POD is deeply doped with fluorine for deposition, the stress relief blowlamp is turned off, and when the non-constant-speed deposition is synchronously adopted, the thicker the rod diameter is, the more the rod diameter is cracked; if the destressing blast lamp is closed, and constant-speed deposition is adopted, almost all cracking occurs. The application adopts a non-constant speed process and is additionally provided with an on-line destressing blast lamp, so that normal deposition can be ensured, and cracking can be avoided.
In conclusion, the preparation method of the optical fiber preform is simple, can effectively control and realize the quantitative production of the optical fiber with ultralow loss and large effective area, and has excellent performance and the effective area of 114 mu m 2 The above can preferably reach 128 μm 2 The loss and the attenuation are low, and the material is the preferable material of the G.264E optical fiber. The method has the advantages that: (1) After the thickness and density of the inner cladding and the optical cladding in VAD deposition are optimally designed, powder layer combination with different density area distribution is realized, and the constraint diffusion of fluoride in the core layer, the inner cladding and the optical cladding is realized by combining a linear sintering fluorine doping process; meanwhile, the reduction of the refractive index of the core layer caused by the fact that the fluoride is not controlled to diffuse to the core layer in a large amount is avoided, and the refractive index requirements of the core layer and the optical cladding layer are influenced; (2) The fluorine doping requirement in the optical cladding and the gradual distribution of the fluoride in the inner cladding are realized by the process, so that the transition effect between the core layer and the optical cladding is very good, and the fluorine in the center is realizedThe viscosity between the optical cladding layers of the core layer and the outer layer is effectively matched; (3) Through the POD non-constant speed deposition and the on-line stress relief process, the phenomenon that the fluorine doped layer with large thickness prepared by the POD is easy to crack due to stress concentration can be eliminated, and the design of the deep fluorine doped concave layer is beneficial to improving the bending resistance of the optical fiber. (4) The outermost layer adopts a pure silicon dioxide design structure, reduces the specific gravity of doped glass in the optical fiber, and is favorable for preparing a large-size optical fiber preform. (5) The upper deposition cavity is divided into an inner chamber and an outer chamber, the powder rod accommodating space is effectively separated from the gas inlet cavity, cavity pressure fluctuation caused by reduction of the space for gas filling in the upper deposition cavity along with the increase of the powder rod is avoided, and the structure effectively improves rod diameter fluctuation of the powder rod.
The foregoing embodiments are merely for illustrating the technical solution of the embodiment of the present application, but not for limiting the same, although the embodiment of the present application has been described in detail with reference to the foregoing preferred embodiments, it will be understood by those skilled in the art that modifications and equivalent substitutions may be made to the technical solution of the embodiment of the present application without departing from the spirit and scope of the technical solution of the embodiment of the present application.
Claims (9)
1. A method for preparing an optical fiber preform, comprising the steps of:
sequentially forming a core layer, an inner cladding layer and an optical cladding layer which are mainly composed of silicon dioxide to obtain a powder rod, wherein the core layer further comprises germanium dioxide generated by reaction;
sequentially performing three stages of dehydroxylation, sintering and vitrification on the powder rod to form a glass rod with constrained diffusion of fluoride in a core layer, an inner cladding layer and an optical cladding layer, wherein the content of fluoride in the glass rod is the least in the core layer, the most and uniformly distributed in the optical cladding layer, and the content of fluoride in the inner cladding layer is gradually increased from the content of fluoride in the outer layer of the core layer to the content of fluoride in the inner layer of the optical cladding layer; the fluoride comprises SiF 4 、CF 4 、SF 6 、C 2 F 6 、SOF 2 、C 2 F 2 Cl 2 One or at least two of (a)The combination, wherein from entering the sintering stage, the flow rate of the fluoride gas is increased linearly at a flow rate of 5-25 cc/min until the sintering stage is finished, and then entering the vitrification stage, the flow rate of the fluoride gas is reduced gradually until the vitrification stage is finished and becomes zero;
the glass rod is extended to a target radius, a fluorine-doped layer is deposited on the surface layer of the glass rod by adopting a plasma deposition process and a stress relief process, and the fluorine-doped glass rod is obtained, wherein the plasma deposition process is used for spraying fluorine-containing gas back and forth on the surface of the glass rod through a POD (point of sale) blast lamp, and the fluorine-containing gas is deposited layer by layer; the fluorine-containing gas comprises silicon tetrachloride, oxygen and fluoride; the fluoride comprises SiF 4 、CF 4 、SF 6 、C 2 F 6 、SOF 2 、C 2 F 2 Cl 2 One or a combination of at least two of the following; the destressing process is that when fluorine-containing gas is sprayed, the mixed gas of oxygen and nitrogen is sprayed at the side of the fluorine-containing gas in the same direction so as to eliminate the stress of the glass;
and forming an outer cladding layer on the outer layer of the fluorine-doped glass rod to obtain the transparent optical fiber preform.
2. The method for manufacturing an optical fiber preform according to claim 1, wherein: the temperature in the dehydroxylation stage is controlled between 1200 and 1250 ℃; entering a sintering stage, taking the temperature of the dehydroxylation stage as an initial temperature, and increasing the temperature to 1320-1450 ℃ at a heating rate of 0.5-5 ℃/min until the sintering stage is finished; and (3) entering a vitrification stage, and keeping the temperature at the end of a sintering stage for 1-3 hours.
3. The method for manufacturing an optical fiber preform according to claim 1, wherein: and in the step of sequentially forming a core layer, an inner cladding layer and an optical cladding layer which are mainly composed of silicon dioxide to obtain a powder rod, wherein the core layer further comprises germanium dioxide generated by reaction, and the reaction gas for forming the core layer comprises oxygen, hydrogen, silicon tetrachloride, germanium tetrachloride and Ar gas, wherein the introducing flow rate of the germanium tetrachloride is controlled to be 50-200cc/min.
4. The method for manufacturing an optical fiber preform according to claim 1, wherein: in the step of sequentially forming a core layer, an inner cladding layer and an optical cladding layer which are mainly composed of silicon dioxide to obtain a powder rod, wherein the core layer further comprises germanium dioxide generated by reaction, the reaction gas for forming the inner cladding layer comprises oxygen, hydrogen, silicon tetrachloride and Ar gas, the introducing flow of the silicon tetrachloride is controlled to be 4 g/min-12 g/min, and the density of silicon dioxide powder generated by reaction is controlled to be 0.5-1.5 g/cm 3 The thickness of the inner cladding is 1/2-1/8 of the radius of the core.
5. The method for manufacturing an optical fiber preform according to claim 1, wherein: in the step of sequentially forming a core layer, an inner cladding layer and an optical cladding layer which are mainly composed of silicon dioxide to obtain a powder rod, wherein the core layer further comprises germanium dioxide generated by reaction, the reaction gas for forming the optical cladding layer comprises oxygen, hydrogen, silicon tetrachloride and Ar gas, the introducing flow of the silicon tetrachloride is controlled to be 20 g/min-40 g/min, and the density of silicon dioxide powder generated by reaction is controlled to be 0.2-0.6 g/cm 3 The total thickness of the optical cladding and the inner cladding is 0.5 to 5.0 times the radius of the core.
6. The method for manufacturing an optical fiber preform according to claim 1, wherein: the translation speed variable DeltaV of the POD blast lamp is-0.1 to-0.3 m/min; the deposition thickness variable DeltaC is 5-10 mm, the initial translation speed is 1m/min, the initial rod diameter is 30mm, and the lowest translation speed is not lower than 0.1m/min.
7. The method for manufacturing an optical fiber preform according to claim 1, wherein: the step of forming the outer cladding layer on the outer layer of the fluorine-doped glass rod to obtain the transparent optical fiber preform comprises the steps of adopting a vapor deposition process to deposit the outer cladding layer on the outer layer of the fluorine-doped glass rod, and then sintering to obtain the transparent optical fiber preform.
8. The method for manufacturing an optical fiber preform according to claim 1, wherein: and forming an outer cladding layer on the outer layer of the fluorine-doped glass rod to obtain a transparent optical fiber preform, wherein the fluorine-doped glass rod is directly arranged in a silicon dioxide sleeve to be assembled into the optical fiber preform.
9. An optical fiber preform molded by the method for producing an optical fiber preform according to any one of claims 1 to 8, comprising, in order from inside to outside, coaxially disposed:
the radius of the middle core layer is 4-6 mu m, and the refractive index of the middle core layer relative to silicon dioxide is 0.15-0.25%;
the inner structure cladding has a radius of 4.5-7.5 mu m, and the refractive index of the inner structure cladding relative to silicon dioxide is graded;
the optical structure layer has a radius of 10-25 mu m and a refractive index of-0.05 to-0.25% relative to silicon dioxide;
the radius of the fluorine-doped structural layer is 20-30 mu m, and the refractive index of the fluorine-doped structural layer relative to silicon dioxide is-0.4 to-0.6 percent;
the outer cladding has a radius of 60 μm or more and a refractive index of 0.
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| US5217516A (en) * | 1985-12-27 | 1993-06-08 | Sumitomo Electric Industries, Ltd. | Method of making optical glass article |
| JPH09221335A (en) * | 1995-12-04 | 1997-08-26 | Sumitomo Electric Ind Ltd | Production of precursor of optical fiber glass preform |
| CN101389573A (en) * | 2005-12-29 | 2009-03-18 | 硅石技术责任有限公司 | Plasma torch for making synthetic silica |
| CN101634728A (en) * | 2009-08-18 | 2010-01-27 | 长飞光纤光缆有限公司 | Anti-bending multimode fiber and manufacturing method thereof |
| CN109081576A (en) * | 2017-06-14 | 2018-12-25 | 中天科技精密材料有限公司 | Preform and its manufacturing method |
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| CN112441736A (en) | 2021-03-05 |
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