CN104402213A - Pure silicon dioxide loose body vitrification fluorine doping method - Google Patents
Pure silicon dioxide loose body vitrification fluorine doping method Download PDFInfo
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- CN104402213A CN104402213A CN201410597846.8A CN201410597846A CN104402213A CN 104402213 A CN104402213 A CN 104402213A CN 201410597846 A CN201410597846 A CN 201410597846A CN 104402213 A CN104402213 A CN 104402213A
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- pure silicon
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/01446—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
- C03B37/01453—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering for doping the preform with flourine
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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]
- C03B37/01413—Reactant delivery systems
- C03B37/0142—Reactant deposition burners
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Abstract
The invention discloses a pure silicon dioxide loose body vitrification fluorine doping method which includes following steps: depositing a pure silicon dioxide loose body through an axial vapour deposition method, wherein two blowtorches, which are different in material feeding temperature, are respectively used for depositing a compact layer and a loose layer to form the pure silicon dioxide loose body; heating and dehydrating the pure silicon dioxide loose body in a vitrification furnace under a dehydration atmosphere, wherein a dehydrating gas is fed into the vitrification furnace during heating; heating the pure silicon dioxide loose body under a fluoride atmosphere so that fluorine is doped into the loose layer of the pure silicon dioxide loose body selectively, wherein a step-type refractive index distribution is formed in the compact layer and the loose layer of the pure silicon dioxide loose body; vitrifying the pure silicon dioxide loose body to form a pure silicon dioxide cored optical fiber performed rod. The method can effectively reduce the content of OH- in a core layer, can reduce attenuation at 1550nm and 1383nm of the optical fiber and allows the fluorine to be distributed uniformly in a radial direction of a wrapping layer of the optical fiber performed rod.
Description
Technical field
The present invention relates to the manufacture method of preform, particularly relate to the vitrifying of a kind of pure silicon dioxide loose media and mix fluorine method.
Background technology
Preform is the starting material of drawing optical fiber, and its basic structure comprises sandwich layer and has the covering of more low-refraction.SiO
2be used to the main glass-former manufacturing preform, its specific refractory power can be changed by doping thus form waveguiding structure.Generally mix GeO in the core
2, make the specific refractory power of sandwich layer higher than the specific refractory power of the pure silica glass of covering.The relative difference of sandwich layer and cladding index adopts refractive index contrast Δ to represent, the specific refractory power of sandwich layer and covering is respectively
with
, the value of refractive index contrast Δ is determined by formula (1):
…………（1）
Sometimes in order to increase the bending resistance of optical fiber, the GeO by increasing in fiber core layer is needed
2content increases Δ value.But along with GeO
2the raising of content, can cause the increase of fiber Rayleigh scattering, thus causes the decay of optical fiber to increase.If the GeO mixed
2too high levels, just easily forms GeO gas, produces bubble thereupon.This transmission performance for final optical fiber and intensity are all disadvantageous.
For above-mentioned reasons, in order to reduce the decay of optical fiber further, pure-silica-core fiber is scheme best at present, in order to obtain the refractive index contrast Δ same with general single mode fiber, need the specific refractory power reducing fibre cladding, mix the specific refractory power that boron and fluorine can reduce silicon-dioxide, but, B
2o
3there is larger hangover at 1.2 μm to absorb, be unfavorable for the reduction of loss, therefore, preferably adopt the specific refractory power of mixing fluorine to reduce the silicon-dioxide forming optical fiber jacket.
The method of current manufacture preform comprises method (MCVD method and PCVD method in pipe, MCVD method is modified chemical vapor deposition method, it is the abbreviation of Modified Chemical Vapour Deposition, PCVD method is plasma body activation vapor deposition method, the abbreviation of Plasma activated Chemical Vapour Deposition) and the outer method of pipe (VAD method and OVD method, VAD method is axial vapor deposition method, it is the abbreviation of Vapour phase Axial Deposition, OVD method is excellent outer chemical vapor deposition method, the abbreviation of Outside Chemical Vapour Deposition).Manage outer method not by the restriction of liner dimensions, sedimentation velocity is fast, and production efficiency is high, is suitable for the large-scale production of large-scale optical fiber prefabricating stick.Know adopt flame hydrolysis gaseous state fluorochemicals can be added in silica glass when depositing, but the method to exist sedimentation effect and the low shortcoming of doping content.Its reason may be: first, fluorine-containing SiO
2particle is not generate in torch flame at once, but diffuses into SiO the process of moving from blowtorch to prefabricated rods loose media along with fluorine
2particle.Diffusion needs the regular hour, causes SiO because the fluorine entering flame reaction is easily diffused in surrounding environment simultaneously
2circumgranular fluorine dividing potential drop is very low.Secondly, SiO
2oH in circumgranular a part of fluorine and flame
-reaction generates HF, therefore only has the fluorine of small part to be incorporated into SiO
2in particle.In addition, HF has corrosive nature to glass particle, the SiO that easy and flame hydrolysis generates
2particle reaction:
SiO
2（s）+2HF（g）→SiOF
2（g）+H
2O（g）…………（2）
SiO
2（s）+4HF（g）→SiF
4（g）+2H
2O（g）…………（3）
(s) and (g) in formula represents solid-state and gaseous state respectively.
These reactions prevent SiO
2the growth of particle, reduces SiO simultaneously
2the deposition of particle.Therefore, along with the increase of fluorochemicals flow, sedimentation effect and sedimentation velocity progressively reduce, and do not produce deposition the most at last.On the other hand, due to the high diffusibility of fluorine, the fluorine-containing loose media that deposition obtains, in sintering process, by the fluorine of loss 40%-50%, makes refractive index profile structure be destroyed, and has a strong impact on the performance of optical fiber after drawing.
In order to solve the problem, publication number be US2003/0101771 A1 U.S. patent applications disclose a kind of preform loose media deposition time mix the method for fluorine: adopt vapour deposition process to deposit loose media in advance, then fluoride gas is ejected on loose media by torch flame burning formation fluoro-gas and forms fluorine-containing atmosphere, now do not pass into silicon-containing compound in blowtorch, avoid generating SiO
2particle.Fluoro-gas realizes doping by diffusing into loose media.There is following problem in this method: because blowtorch is certain position from a direction, fluoro-gas being sprayed to loose media, is difficult to ensure the axis of Fluorin doped and radial homogeneity.Although this patent proposes to adopt multiple blowtorch and utilize the method for opening cover and heating to improve the homogeneity of mixing fluorine, the fluctuation of Oil repellent in axis and radial direction still may be there is.In addition, during fluorine-containing loose media sintering also can there is diffusion and run off in fluorine.
For above problem, the patent No. be US4629485 U.S. patents disclose the method that fluorine is mixed in the vitrifying of a kind of preform loose media: good for the vapour deposition loose media containing hole is put into vitrifying stove and heats, pass into fluoride gas flow through loose media surface and make it fully diffuse into loose media, finally loose media glass is changed into and transparent mix fluorine glass.Concrete steps are: first adopt OVD method to deposit pure SiO
2loose media, then loose media is put into vitrifying stove and carry out dehydration vitrifying, then the plug after vitrifying is extended, adopt again on OVD method pure silicon dioxide plug after extension and deposit surrounding layer, after the loose media that deposition obtains dewaters in vitrifying stove, pass into fluoride gas, then after vitrifying, obtain the prefabricated rods of doped cladding layer fluorine.The method mixes that fluorine speed is fast and doping content is high, but the preform sandwich layer hydroxy radical content manufactured through the method is higher, and the transmission loss of the optical fiber 1383nm wavelength of drawing reaches more than 2dB/km.Its reason is: the pure silicon dioxide plug after (1) vitrifying is surperficial by OH in extension process
-pollute, OH
-at high temperature diffuse into plug.(2) plug after extending deposits covering through flame hydrolysis, the OH that hydrolysis reaction produces
-sandwich layer is diffused under follow-up hot environment (vitrifying and wire drawing).In order to reduce OH
-pollution, when producing plug, not only manufacture sandwich layer also fabrication portion covering (inner cladding).And cored ratio (ratio of plug cladding diameter and sandwich layer diameter) must be controlled more than 4.0 when adopting flame hydrolysis outsourcing to manufacture preformod of optical fiber with low water peak.Problem brought thus is: because the sandwich layer of plug that deposits and covering are all the loose medias containing a large amount of hole, when fluorine is mixed in vitrifying, fluorine not only diffuses into covering, and enters sandwich layer, causes fluorine to be difficult to optionally to mix covering and forms refractive index profile structure.
For this reason, the patent No. be the United States Patent (USP) of US4620861, publication number to be the U.S. Patent application of US2002/0073740 A1 and application number be 00805475.4 Chinese patent application propose the method that when fluorine is mixed in vitrifying, plug refractive index profile controls respectively.The patent No. doping agent that to be the method for the United States Patent (USP) of US4620861 be mixes different concns by plug deposition process center core layer and covering makes its softening temperature lower than the softening temperature of pure silica glass, after heating, doping sandwich layer and the covering that do not adulterate (or sandwich layer is different with the concentration of clad doped dose) form different density and porosity thus realize plug optionally vitrifying, pass into fluoride gas afterwards, fluorine optionally mixes covering.But the method is not suitable for the manufacture of pure-silica-core fiber prefabricated rods.Although the sandwich layer doping post softening temperature of plug declines, after heating, density increases, and porosity reduces, thus when making vitrifying mix fluorine, fluorine effectively cannot diffuse into sandwich layer.But when sandwich layer and clad doped agent concentration are more or less the same, sandwich layer and covering cannot form effective interface, thus fluorine is made to be difficult to invariably can diffuse into sandwich layer.And publication number be US2002/0073740 A1 U.S. patent applications disclose a kind of method that relation according to fluorochemical speed of response and velocity of diffusion controls plug refractive index profile: when fluorine is mixed in loose media vitrifying, the speed that fluoride gas and loose media react and the speed that fluoride gas spreads in loose media are all the functions of temperature, along with the rising of temperature, fluoride gas and loose media speed of response are faster than the speed of fluoride gas at loose media internal diffusion.Therefore, by controlling the temperature and time mixing fluorine, parameter Ф>=1(Ф is defined as
, wherein
for the radius of loose media,
for the spread coefficient of fluoride gas in loose media,
reaction rate constant for fluoride gas and loose media), thus control the radial doping depth of fluorine in loose media.But the method is clearly difficult to the refractive index profile structure forming step change type.Application number for the method disclosed in the Chinese patent application of 00805475.4 is: loose media vapour deposition obtained passes into CF after dehydrating in vitrifying stove
4flow through the outside surface of loose media, the time of doping and temperature are enough to make and CF
4the Fluorin doped concentration on the loose media surface of contact is minimum, and increases progressively to center gradually.Obviously, the method and publication number are the same refractive index profile structure being difficult to be formed step change type of method of the U.S. Patent application of US2002/0073740 A1.Application number method disclosed in the Chinese patent application of 201310126465.7 is: adopt OVD to deposit the mandrel loose body obtained, then by the outside surface sintering densification of loose media, then sedimentary inner envoloping layer loose media outside tight zone is continued, form mandrel loose body, send into after mandrel loose body being detached target rod in vitrifying stove and carry out mixing fluorine, make fluorine optionally mix inner cladding, the shortcoming of this kind of method is dehydration and doping process loose media is all hollow, the OH that hydrolysis reaction produces
-and the fluorine element mixing fluorine process more easily enters the central hollow of loose media, and then diffuse into sandwich layer, cause fluorine element to adulterate unsuccessfully, after vitrifying terminates, also will be carried out the sealing of centre hole in addition by vertical rolling equipment, this also can cause the OH of sandwich layer
-content overproof, affects further optical fiber property after wire drawing.
Summary of the invention
The technical assignment of the technical problem to be solved in the present invention and proposition is the defect overcoming prior art existence, provides the vitrifying of a kind of pure silicon dioxide loose media to mix fluorine method.
For this reason, the present invention is by the following technical solutions:
Fluorine method is mixed in the vitrifying of a kind of pure silicon dioxide loose media, it is characterized in that comprising the following steps:
Axial vapor deposition method is utilized to deposit pure silicon dioxide loose media, establish two blowtorch that feed temperature is different during deposition simultaneously, blowtorch is near depocenter and the higher and tight zone of this blowtorch formation of deposits pure silicon dioxide loose media of temperature, and another blowtorch departs from depocenter and the lower and tectorium of this blowtorch formation of deposits pure silicon dioxide loose media of temperature;
Described pure silicon dioxide loose media is put into vitrifying stove and at dehydration atomosphere thermal dehydration, while heating, in vitrifying stove, passes into dehydrated air;
In fluorochemical atmosphere, heat described pure silicon dioxide loose media, make fluoride gas optionally mix in the tectorium of pure silicon dioxide loose media;
Pure silicon dioxide loose media described in vitrifying, make the tight zone of pure silicon dioxide loose media form pure silicon dioxide sandwich layer, the tectorium of pure silicon dioxide loose media forms fluorine-containing covering, described sandwich layer and covering form pure-silica-core fiber prefabricated rods.
As optimization technique means, the Ratio control of the diameter of described pure silicon dioxide loose media and the diameter of pure silicon dioxide loose media tight zone>=10.0, to ensure the ratio of fibre core diameter and Bao Jing; The density of described tight zone is 1.4-2.5g/cm
3, during to avoid mixing fluorine, fluorine gas atmosphere enters tight zone, also avoids tight zone oversintering simultaneously.。
As optimization technique means, the blowtorch material flow of described deposition pure silicon dioxide loose media tectorium is 2.0-10.0 with the ratio of the blowtorch material flow of deposition pure silicon dioxide loose media tight zone, is controlled the diameter of tight zone and tectorium by flow difference part.
As optimization technique means, the temperature of the blowtorch of described deposition pure silicon dioxide loose media tectorium is 800 DEG C-1000 DEG C; The temperature of the blowtorch of described deposition pure silicon dioxide loose media tight zone is 850 DEG C-1080 DEG C; Both control at 50 DEG C-80 DEG C at temperature head, can ensure density variation and the sedimentation effect difference of loose media tectorium and tight zone like this.
As optimization technique means, in described dehydration atomosphere and dehydrated air, contain Cl
2gas and He gas; Heating temperature during dehydration in vitrifying stove is 1100 DEG C-1400 DEG C, and moisture can be removed by this temperature range completely, simultaneously again can not by loose media vitrifying.
As optimization technique means, described dehydrated air flows through described pure silicon dioxide loose media from top to bottom, and the temperature of mixing loose media during fluorine is 1100 DEG C-1400 DEG C.
As optimization technique means, described fluorochemical atmosphere is SiF
4, CF
4, SF
6, C
2f
6, C
2f
2cl
2, F
2, C
3f
8, NF
3, SOF
2, SO
2one or more combination in ClF.
As optimization technique means, described fluorochemical atmosphere contains He and N
2, He can improve the heat conduction efficiency of gas, N
2then as inert protective atmosphere.
As optimization technique means, by latch, the kind rod of taking the lead containing pore is fixed on fixture, then at kind of an excellent bottom deposition pure silicon dioxide loose media, and plants one end that rod is positioned at the rear pure silicon dioxide loose media of deposition.After pure silicon dioxide loose media has deposited, on described kind rod is installed to above vitrifying stove fixture by latch and slow being dropped in the middle of vitrifying stove by pure silicon dioxide loose media carries out vitrifying.Heating temperature during vitrifying in vitrifying stove is 1480 DEG C-1600 DEG C, and the vitrifying time is 2 hours-10 hours.
The invention has the beneficial effects as follows: first, establish two blowtorch that feed temperature is different when utilizing VAD to deposit simultaneously, feed temperature difference due to two blowtorch forms tight zone and the tectorium of pure silicon dioxide loose media, the tectorium of pure silicon dioxide loose media and tight zone are still porosity and looseness state, pass into dehydrated air in dehydration, effectively reduce the OH in pure silicon dioxide loose media
-content, thus the decay greatly reducing optical fiber 1383nm, in addition owing to being Pure Silica Core Fiber prefabricated rods, do not have the doping of germanium, reduce Rayleigh scattering, greatly can reduce the decay of 1550nm.Secondly, the existence of the density difference of pure silicon dioxide loose media tectorium and tight zone, when fluorine is mixed in vitrifying, fluoride gas optionally diffuses into the tectorium of pure silicon dioxide loose media and cannot enter the tight zone of pure silicon dioxide loose media, thus forms Stepped-index distribution.Relative to prior art, owing to being doping and vitrifying in fluorochemical atmosphere, fluorine is evenly distributed in covering radial direction, and refractive index profile can not be caused due to the loss of fluorine to be destroyed.Finally, method of the present invention mixes that fluorine speed is fast, and doping content is high, doping evenly, be suitable for the large-scale production of large-scale optical fiber prefabricating stick.
Accompanying drawing explanation
Fig. 1 is the schematic cross-section of preform;
Fig. 2 is the schematic diagram according to the inventive method deposition loose media;
Fig. 3 is according to schematic cross-section during the inventive method deposition loose media;
Fig. 4 is according to schematic diagram during the inventive method enforcement vitrifying;
Fig. 5 is the optical fiber precast rod refractivity sectional view according to the embodiment of the present invention 1;
Fig. 6 is the optical fiber precast rod refractivity sectional view according to the embodiment of the present invention 2;
Number in the figure illustrates:
1 '-covering, 2 '-sandwich layer, 1-latch, 2-kind rod, the tight zone of 3-pure silicon dioxide loose media, the tectorium of 4-pure silicon dioxide loose media, 5-pure silicon dioxide loose media, 6-tight zone blowtorch, 7-tectorium blowtorch, 8-heating member, 9-furnace core tube, 10-air feed port, 11-gas direction arrow, 12-venting port;
The refractive index contrast of Δ-preform sandwich layer and covering.
Embodiment
Below in conjunction with Figure of description, the present invention will be further described.
Fluorine method is mixed in pure silicon dioxide loose media of the present invention vitrifying, comprises the following steps:
Axial vapor deposition method (VAD method) is utilized to deposit pure silicon dioxide loose media, establish two blowtorch that feed temperature is different during deposition simultaneously, blowtorch is near depocenter and the higher and tight zone of this blowtorch formation of deposits pure silicon dioxide loose media of temperature, and another blowtorch departs from depocenter and the lower and tectorium of this blowtorch formation of deposits pure silicon dioxide loose media of temperature;
Pure silicon dioxide loose media is put into vitrifying stove and at dehydration atomosphere thermal dehydration, while heating, in described vitrifying stove, passes into dehydrated air;
In fluorochemical atmosphere, heat described pure silicon dioxide loose media, make fluoride gas optionally mix in the tectorium of pure silicon dioxide loose media;
Pure silicon dioxide loose media described in vitrifying, make the tight zone of pure silicon dioxide loose media form pure silicon dioxide sandwich layer, the tectorium of pure silicon dioxide loose media forms fluorine-containing covering, sandwich layer and covering form pure-silica-core fiber prefabricated rods.
Concrete, the Ratio control of the diameter of pure silicon dioxide loose media and the diameter of pure silicon dioxide loose media tight zone is>=10.0; The density of tight zone is 1.4-2.5g/cm
3.The blowtorch material flow (unit Liter Per Minute, slm) of deposition pure silicon dioxide loose media tectorium is 2.0-10.0 with the ratio of the blowtorch material flow (unit milliliter per minute, sccm) of deposition pure silicon dioxide loose media tight zone.The temperature of the blowtorch of deposition pure silicon dioxide loose media tectorium is 800 DEG C-1000 DEG C; The temperature of the blowtorch of deposition pure silicon dioxide loose media tight zone is 850 DEG C-1080 DEG C; Both control at 50 DEG C-80 DEG C temperature head.Cl is contained in dehydration atomosphere and dehydrated air
2gas and He gas; Heating temperature during dehydration in vitrifying stove is 1100 DEG C-1400 DEG C.Described dehydrated air flows through described pure silicon dioxide loose media from top to bottom, and the temperature of mixing loose media during fluorine is 1100 DEG C-1400 DEG C.Described fluorochemical atmosphere is SiF
4, CF
4, SF
6, C
2f
6, C
2f
2cl
2, F
2, C
3f
8, NF
3, SOF
2, SO
2one or more combination in ClF.Described fluorochemical atmosphere contains He and N
2.By latch, the kind rod of taking the lead containing pore is fixed on fixture, then at kind of an excellent bottom deposition pure silicon dioxide loose media, and plants one end that rod is positioned at the rear pure silicon dioxide loose media of deposition.After pure silicon dioxide loose media has deposited, on described kind rod is installed to above vitrifying stove fixture by latch and slow being dropped in the middle of vitrifying stove by pure silicon dioxide loose media carries out vitrifying.Heating temperature during vitrifying in vitrifying stove is 1480 DEG C-1600 DEG C.The vitrifying time is 2 hours-10 hours.
Describe the preferred embodiments of the invention in detail below with reference to accompanying drawings.
Fig. 1 is preform schematic cross-section.Preform is formed by post-depositional loose media vitrifying.Preform be made up of sandwich layer (plug) 2 ' and covering 3 ', and wherein the specific refractory power of plug 2 ' is higher than the specific refractory power of covering 1 ', thus formation waveguiding structure.
Fig. 2 is VAD depositing operation (equipment) schematic diagram for the manufacture of pure silicon dioxide loose media.Plant excellent 2(also referred to as drawing rod) be installed on reactor fixture by latch 1, then origin position is dropped to, plant rod to rotate with certain spindle speed, then off-response still starts normal sedimentation process, once loose media covers laser, motor can upwards draw kind of a rod with certain speed, makes loose media continued propagation.Gaseous state SiCl
4raw material and oxyhydrogen flame react, and produce a large amount of SiO
2particle, its particle diameter from a few nanometer to hundreds of nanometer not etc., grow up gradually along with cohesion, and then particle deposits along with air-flow and thermophoresis effect are brought to kind of rod 2 lower end, and continues down to grow, until reach certain loose media length by particle.Complete because loose media deposits two blowtorch simultaneously, blowtorch 6 temperature is higher, position partially in, material flow is less than normal, the tight zone 3 of deposition pure silicon dioxide loose media, blowtorch 7 temperature is lower, position is on the upper side, and material flow is bigger than normal, the tectorium 4 of deposition pure silicon dioxide loose media, in order to prevent pure silicon dioxide loose media from ftractureing in deposition process, temperature head, the relative position of two blowtorch 6 and blowtorch 7 are most important for deposition process.The density of pure silicon dioxide loose media tight zone 3, higher than the density of pure silicon dioxide loose media tectorium 4, is preferably greater than 1.4g/cm
3, be more preferably greater than 1.8g/cm
3.
Fig. 3 is the schematic cross-section of pure silicon dioxide loose media 5, and tight zone 3 is positioned at the bosom of pure silicon dioxide loose media, and tectorium 4 forms the covering of pure silicon dioxide loose media uniformly around tight zone.In order to drawing optical fiber after fibre core footpath and Bao Jing match, the diameter control of pure silicon dioxide loose media diameter and pure silicon dioxide loose media tight zone 3, more than 10.0, preferably controls between 10.5-15.
Pure silicon dioxide loose media after having deposited is loose porous state, and its tectorium density is 0.1-1.2g/cm
3, preferably, its density is 0.2-0.8g/cm
3, more preferably, its density is 0.4-0.6g/cm
3.
Next pure silicon dioxide loose media 5 is unloaded from fixture, then utilize latch to be installed on the fixture of vitrifying stove by the circular hole of kind of rod 2 head, be put in the middle of vitrifying stove and carry out vitrifying.
Vitrifying stove is by heating member 8(resistance furnace or other heating unit) heat pure quartzy furnace core tube 9, heating zone length is 400mm when temperature fluctuation ± 25 DEG C, the speed of rotation of pure silicon dioxide loose media 5 is 3-10rpm, and decline enters heating zone gradually, the tight zone 3 of pure silicon dioxide loose media forms the mandrel loose body of prefabricated rods, and pure silicon dioxide loose media tectorium 4 forms the surrounding layer of prefabricated rods loose media.
A large amount of OH can be introduced in process due to hydrolysis reaction deposition loose media
-, and prefabricated rods particularly mandrel loose body 3 couples of OH
-requirement high especially, in order to obtain low OH
-the mandrel loose body 3 of content, must through the process of dehydration.Cl in dehydration
2enter vitrifying stove with He from air feed port 10, and from bottom to top (arrow 11) flows through pure silicon dioxide loose media 5 surface, then flows out from vitrifying fire grate gas port 12.Cl
2effect be dewatering agent, its reaction equation is:
2Cl
2+ 2H
2O = O
2+ 4HCl………………………（4）
2Si-OH + 2Cl
2= 2Si-Cl + O
2+ 2HCl…………（5）
The cardinal principle of dehydration is exactly in fact use Cl
-replace isolated OH
-halogenating reaction process, reaction result causes the generation of Si-Cl key, and the fundamental vibration absorption peak due to this key is positioned near 25 μm, away from current optical communication operating wavelength area, so to the attenuation by absorption in Optical Fiber Transmission process and moment-less influence; The Main Function of He is auxiliary dehydration, because He has, atomic volume is little, diffusivity is high, the feature of stable performance, so it penetrates into mandrel loose body 3 inside easily via the hole in pure silicon dioxide loose media 5 and can not have an impact to the performance of prefabricated rods, He mono-brings Cl in aspect
2, make it fully to contact with pure silicon dioxide loose media 5, on the other hand, the waste gas of dehydration reaction and moisture brought out; Dehydrate step to carry out under lower than pure silicon dioxide loose media 5 second-order transition temperature, dehydration temperaturre is 1100 DEG C-1400 DEG C.Temperature is too high, easily causes pure silicon dioxide loose media 5 closing of pores, Cl
2effectively cannot enter mandrel loose body 3 inside to dewater.Temperature is too low, then the required time is oversize, is not suitable for suitability for industrialized production.Time of drying is 0.5-5 hour.After dehydrating, pure silicon dioxide loose media again progressively declines and enters heating zone, simultaneously passes into fluoride gas from air feed port 10 and flows through pure silicon dioxide loose media 5 surface (arrow 11) and carry out loose media 4 and mix fluorine.Preferably, diluent gas is preferably contained in vitrifying stove as helium.Because the sandwich layer loose media 3 of pure silicon dioxide loose media 5 and surrounding layer loose media 4 density exist certain gap, the fluoride gas diffusing into surrounding layer loose media 4 cannot enter sandwich layer loose media 3.Fluoride gas is at least SiF
4, CF
4, SF
6, C
2f
6, C
2f
2cl
2, F
2, C
3f
8, NF
3, SOF
2, SO
2the combination of a kind of in ClF or at least two kinds.Mixing fluorine temperature can be identical with dehydration temperaturre, carries out at temperature that also can be different with dehydration temperaturre.Fluoride gas accounts for the 1-30% of total gas flow rate.The time of mixing fluorine is enough to fluorine is diffused into fully and is evenly distributed in surrounding layer loose media 4.Time controling is at 0.5-5 hour.Then He, O is passed into
2carry out vitrifying, vitrified temperature range is 1480-1600 DEG C.Owing to being mixed with fluorine in surrounding layer loose media 4, second-order transition temperature can be made to decrease.According to the difference of mandrel loose body diameter, length and second-order transition temperature and speed, vitrified time is 0.5-8 hour.After vitrifying completes, prefabricated rods is drawn into step type single mode optical fiber by drawing process conveniently.
embodiment 1:
Utilize VAD method to carry out the making of pure silicon dioxide loose media 5, in blowtorch 6, the flow of hydrogen, oxygen and silicon tetrachloride is respectively 18slm, 30 slm and 20sccm.In blowtorch 7, the flow of hydrogen, oxygen and silicon tetrachloride is respectively 118slm, 138slm and 100slm.Kind of rod 2 is inserted on the fixture of VAD reactor by latch 1, drops to origin position.Gaseous halide raw material SiCl
4be hydrolyzed reaction in oxyhydrogen flame, produces a large amount of SiO
2particle deposition is on the lowermost end of kind of rod 2.Along with kind of rod 2 rotation and slowly promote, SiO
2particle is deposited on the lower end of the kind rod 2 of rotation gradually, in axial direction grows.After having deposited, the external diameter of pure silicon dioxide loose media 5 is 160mm, and length is 1500mm.
Pull up latch 1, pure silicon dioxide loose media is unloaded from fixture, be then installed on vitrifying stove fixture, and slow being dropped in the middle of vitrifying stove by pure silicon dioxide loose media 5 carries out vitrifying.Vitrifying stove heats pure quartzy furnace core tube 9 by heating member 8, and heating zone length is 400mm when temperature fluctuation ± 25 DEG C.The speed of rotation of pure silicon dioxide loose media 5 is 3rpm, and decline enters heating zone gradually.First pass into inert nitrogen gas to purge, then pass into Cl
2dehydrate with He, to remove the OH in mandrel loose body 3
-.Dehydrated air enters vitrifying stove from air feed port 10, and from bottom to top (arrow 11) flows through the surface of pure silicon dioxide loose media 5, flows out from vitrifying fire grate gas port 12.Dehydration temperaturre is 1100 DEG C, and dewatering time is 3 hours.After dehydrating, pure silicon dioxide loose media 5 again progressively declines and enters heating zone, passes into SF from air feed port 10 simultaneously
6gas, He gas and N
2gas, the surface (arrow 11) flowing through pure silicon dioxide loose media 5 is carried out loose media 4 and is mixed fluorine.Because the sandwich layer loose media 3 of pure silicon dioxide loose media 5 and surrounding layer loose media 4 density exist certain gap, the fluoride gas diffusing into surrounding layer loose media 4 cannot enter sandwich layer loose media 3.The temperature of mixing fluorine is 1200 DEG C, SF
6gas accounts for 15% of total gas flow rate.The time of mixing fluorine is 2 hours, thus fluorine is fully diffused in loose media 4.Then He, O is passed into
2carry out vitrifying, vitrified temperature is 1480 DEG C, and vitrified time is 5 hours.After vitrifying completes, through the test of PK2600 prefabricated rods comprehensive tester, as shown in Figure 5, Δ value reaches 0.332% to the refractive index profile of Pure Silica Core Fiber prefabricated rods.Draw by ordinary method and obtain G.652D optical fiber, its 1550nm decays to 0.190dB/km, and 1383nm decays to 0.292dB/km.
embodiment 2
Utilize VAD method to carry out the making of pure silicon dioxide loose media 5, in blowtorch 6, the flow of hydrogen, oxygen and silicon tetrachloride is respectively 10slm, 16 slm and 10sccm.In blowtorch 7, the flow of hydrogen, oxygen and silicon tetrachloride is respectively 60slm, 70slm and 50slm.Kind of rod 2 is inserted on the fixture of VAD reactor by latch 1, drops to origin position.Gaseous halide raw material SiCl
4be hydrolyzed reaction in oxyhydrogen flame, produces a large amount of SiO
2particle deposition is on the lowermost end of kind of rod 2.Along with kind of rod 2 rotation and slowly promote, SiO
2particle is deposited on the lower end of the kind rod 2 of rotation gradually, in axial direction grows.After having deposited, the external diameter of pure silicon dioxide loose media 5 is 80mm, and length is 1500mm.
Pull up latch 1, pure silicon dioxide loose media is unloaded from fixture, be then installed on vitrifying stove fixture, and slow being dropped in the middle of vitrifying stove by pure silicon dioxide loose media 5 carries out vitrifying.Vitrifying stove heats pure quartzy furnace core tube 9 by heating member 8, and heating zone length is 400mm when temperature fluctuation ± 25 DEG C.The speed of rotation of pure silicon dioxide loose media 5 is 3rpm, and decline enters heating zone gradually.First pass into inert nitrogen gas to purge, then pass into Cl2 and He and dehydrate, to remove the OH in mandrel loose body 3
-.Dehydrated air enters vitrifying stove from air feed port 10, and from bottom to top (arrow 11) flows through the surface of pure silicon dioxide loose media 5, flows out from vitrifying fire grate gas port 12.Dehydration temperaturre is 1150 DEG C, and dewatering time is 3 hours.After dehydrating, pure silicon dioxide loose media 5 again progressively declines and enters heating zone, passes into CF from air feed port 10 simultaneously
4gas, He gas and N
2gas, the surface (arrow 11) flowing through pure silicon dioxide loose media 5 is carried out loose media 4 and is mixed fluorine.Because the sandwich layer loose media 3 of pure silicon dioxide loose media 5 and surrounding layer loose media 4 density exist certain gap, the fluoride gas diffusing into surrounding layer loose media 4 cannot enter sandwich layer loose media 3.The temperature of mixing fluorine is 1250 DEG C, CF
4gas accounts for 20% of total gas flow rate.The time of mixing fluorine is 3 hours, thus fluorine is fully diffused in loose media 4.Then He, O is passed into
2carry out vitrifying, vitrified temperature is 1480 DEG C, and vitrified time is 3 hours.After vitrifying completes, through the test of PK2600 prefabricated rods comprehensive tester, as shown in Figure 6, Δ value reaches 0.360% to the refractive index profile of Pure Silica Core Fiber prefabricated rods.Draw by ordinary method and obtain ultra-low-loss fiber, its 1550nm decays to 0.170dB/km, and 1383nm decays to 0.248dB/km.
It should be noted that, the mode of above-described embodiment is only limitted to describe embodiment, but the present invention is not confined to aforesaid way, and those skilled in the art can modify accordingly without departing from the scope of the present invention easily, therefore scope of the present invention should comprise disclosed principle and the maximum range of new feature.
Claims (11)
1. a fluorine method is mixed in the vitrifying of pure silicon dioxide loose media, it is characterized in that comprising the following steps:
Axial vapor deposition method is utilized to deposit pure silicon dioxide loose media, establish two blowtorch that feed temperature is different during deposition simultaneously, blowtorch is near depocenter and the higher and tight zone of this blowtorch formation of deposits pure silicon dioxide loose media of temperature, and another blowtorch departs from depocenter and the lower and tectorium of this blowtorch formation of deposits pure silicon dioxide loose media of temperature;
Described pure silicon dioxide loose media is put into vitrifying stove and at dehydration atomosphere thermal dehydration, while heating, in vitrifying stove, passes into dehydrated air;
In fluorochemical atmosphere, heat described pure silicon dioxide loose media, make fluoride gas optionally mix in the tectorium of pure silicon dioxide loose media;
Pure silicon dioxide loose media described in vitrifying, make the tight zone of pure silicon dioxide loose media form pure silicon dioxide sandwich layer, the tectorium of pure silicon dioxide loose media forms fluorine-containing covering, described sandwich layer and covering form pure-silica-core fiber prefabricated rods.
2. fluorine method is mixed in pure silicon dioxide loose media according to claim 1 vitrifying, it is characterized in that: the Ratio control of the diameter of described pure silicon dioxide loose media and the diameter of pure silicon dioxide loose media tight zone is>=10.0; The density of described tight zone is 1.4-2.5g/cm
3.
3. fluorine method is mixed in pure silicon dioxide loose media according to claim 1 vitrifying, it is characterized in that: the blowtorch material flow of described deposition pure silicon dioxide loose media tectorium is 2.0-10.0 with the ratio of the blowtorch material flow of deposition pure silicon dioxide loose media tight zone.
4. fluorine method is mixed in pure silicon dioxide loose media according to claim 1 vitrifying, it is characterized in that: the temperature of the blowtorch of described deposition pure silicon dioxide loose media tectorium is 800 DEG C-1000 DEG C; The temperature of the blowtorch of described deposition pure silicon dioxide loose media tight zone is 850 DEG C-1080 DEG C; Both control at 50 DEG C-80 DEG C temperature head.
5. fluorine method is mixed in pure silicon dioxide loose media according to claim 1 vitrifying, it is characterized in that: contain Cl in described dehydration atomosphere and dehydrated air
2gas and He gas; Heating temperature during dehydration in vitrifying stove is 1100 DEG C-1400 DEG C.
6. fluorine method is mixed in pure silicon dioxide loose media according to claim 1 vitrifying, it is characterized in that: described dehydrated air flows through described pure silicon dioxide loose media from top to bottom, and loose media temperature when carrying out Fluorin doped is 1100 DEG C-1400 DEG C.
7. fluorine method is mixed in pure silicon dioxide loose media according to claim 1 vitrifying, it is characterized in that: described fluorochemical atmosphere is SiF
4, CF
4, SF
6, C
2f
6, C
2f
2cl
2, F
2, C
3f
8, NF
3, SOF
2, SO
2one or more combination in ClF.
8. fluorine method is mixed in pure silicon dioxide loose media according to claim 1 vitrifying, it is characterized in that: described fluorochemical atmosphere contains He and N
2.
9. fluorine method is mixed in pure silicon dioxide loose media according to claim 1 vitrifying, it is characterized in that: by latch, the kind rod of taking the lead containing pore is fixed on fixture, then at kind of an excellent bottom deposition pure silicon dioxide loose media, and one end that rod is positioned at the rear pure silicon dioxide loose media of deposition is planted.
10. fluorine method is mixed in pure silicon dioxide loose media according to claim 9 vitrifying, it is characterized in that: after pure silicon dioxide loose media has deposited, on described kind rod is installed to above vitrifying stove fixture by latch and slow being dropped in the middle of vitrifying stove by pure silicon dioxide loose media carries out vitrifying.
Fluorine method is mixed in 11. pure silicon dioxide loose media according to claim 10 vitrifyings, it is characterized in that: Heating temperature during vitrifying in vitrifying stove is 1480 DEG C-1600 DEG C, and the vitrifying time is 2-10 hour.
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