CN1026576C

CN1026576C - Method of manufacturing silica glass preform

Info

Publication number: CN1026576C
Application number: CN92104221A
Authority: CN
Inventors: 日原弘; 奥诚人; 八木健; 榎本宪嗣; 佐藤继男; 吉田和昭; 森川孝行
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 1991-04-30
Filing date: 1992-04-30
Publication date: 1994-11-16
Anticipated expiration: 2007-04-30
Also published as: CN1070897A

Abstract

The method of manufacturing a silica glass base preform comprises the steps of inserting a rod-like member mainly containing a ductile material, into a forming space of a mold , charging the remaining space of the forming spacewith a forming material containing silica glass powder or doped silica glass powder, compressing the mold charged with the forming material from outside such as to form a porous glass body of the forming material around the rod-like member, removing the rod-like memberfrom the porous glass body , inserting a glass rod into the hole formed after removal of the rod-like member, purifying said porous glass body in which the glass rod is inserted, and consolidating said porous glass body purified in the above purifying step.

Description

Method of manufacturing silica glass preform

The present invention relates to make the method for silica glass preform, optical fiber, optical waveguides, biography that this prefabricated component can be used for preparing in long distance communications or the optical field resemble fiber, post lens or its analogue.

Usually, people have known with rod in tube method and have prepared the optical fiber used in long distance communications or the optical field or the silica glass preform of optical waveguides.

According to rod in tube method, people will be inserted into as the glass stick of plug in the another kind of Glass tubing as coating layer, then they be made it to be melt into an integral body with the heating unit heating, form silica glass preform thus.Yet there is a problem in this method, and this problem is owing to the bubble that remains in the prefabricated component of making forms, and these bubbles are again that the incomplete fragmentation owing to the interface between glass stick and the pipe in the heat fused process produces.

Generally speaking, with the prefabricated component that contains bubble it is heated, it is lower to be controlled to its quality of optical fiber, and its reliability can be not high yet, and especially, its mechanical strength of the optical fiber of making thus is also lower.

Alternative method as rod in tube method, people have proposed another kind of method again, its adopts isostatic pressing technology to form the porous vitreum that coats on the periphery of glass plug, then the porous glass preform of making is dewatered and is consolidated into a kind of silica glass preform (referring to the disclosed Japanese patent application JP61-256937 that do not examine).

During actually operating, aforesaid method carries out in the following manner, at first, will insert as the glass stick of plug in a kind of deformable mould, and remaining space is used as the quartz glass powder of formed material and clogs.Thereby press the mould of filling in material on the periphery of glass stick, to form porous vitreum from the outside with hydrostatic pressure then.

After this, the porous vitreum that makes is thus taken out from mould and it is carried out sequence of operations comprising dehydration with fixedly make it to form glass preform for optical fiber.

In aforesaid method, need on the mould outside surface, to apply about 0.1 to 0.7 ton/centimetre to its central axis direction ²Pressure, be about 5 to 40 minutes clamping time.Sometimes being positioned at mould intermediary glass stick can rupture because of institute's applied pressure.The external diameter of glass stick is more little, and then glass stick is got over easy fracture.In addition, when this glass stick fracture, the porous vitreum that is molded into also can break because of the surging force that the glass stick fracture is produced.

As a result, when adopting isostatic pressing method to prepare porous vitreum (around glass stick), product production is always lower.

The present invention considers that just the problems referred to above propose, therefore but goal of the invention of the present invention is to improve the method that a kind of high yield prepares silica glass preform, and in fact the present invention realizes its purpose by preventing that when centering on glass stick formation porous vitreum with isostatic pressing method glass stick and porous vitreum are damaged.

According to the present invention, it provides a kind of method for preparing silica glass preform, it comprises the following steps: that the bar-like member that will mainly contain a kind of Drawability material is inserted in the molding space of mould, with the remaining space in the molding material fills mould that contains quartz glass powder or adulterated quartz glass powder; Pressing from the outside, the mould of filling molding material makes this formed material form a kind of porous vitreum around this bar-like member; Thereby from porous vitreum, take out this bar-like member and after removing this bar-like member, form a hole; Insert in this hole according to glass stick one; The said porous vitreum that has inserted glass stick of purifying, and with said in above-mentioned purification step the porous vitreum of purifying fixed.

Some other purpose of the present invention and advantage will provide in the description of back, and wherein some can obviously be found out from these are described, and perhaps recognize by implementing the present invention.By means of instruction of specifically noted in appending claims and combination, can be familiar with and obtain objects and advantages of the present invention.

The accompanying drawing of introducing and becoming the part of this specification sheets has been described certain preferred embodiments of the present invention, and they and the overview section of front and the detailed description of the preferred embodiments of back come together to describe fundamental principles more of the present invention.

Fig. 1 is the cross-sectional view of principal section figure that is used for implementing the shaped device of method of the present invention;

Fig. 2 represents a step in the inventive method, has wherein formed a kind of porous vitreum around bar-like member;

Fig. 3 A represents a step in present method, and wherein this bar-like member is taken out from this porous vitreum;

Fig. 3 B represents a step in present method, wherein a glass stick is inserted into and takes away in the hole that forms behind the bar-like member;

Fig. 3 C represents with this porous vitreum the silica glass preform after fixed;

Fig. 4 is the cross-sectional view of major portion that is used for implementing the another kind of shaped device of the inventive method;

Fig. 5 A and 5B represent the side-view of the porous vitreum of another embodiment;

Fig. 6 is the cross-sectional view that is used to form the shaped device of the porous vitreum of shape shown in Fig. 5 B;

Fig. 7 is the side-view of porous vitreum, is used to explain the method for the porous vitreum of another kind of preparation shape shown in Fig. 5 B.

Describe specific embodiments of the present invention below with reference to accompanying drawings in detail.

Fig. 1 is the cross-sectional view of principal section figure that is used to implement the shaped device of one embodiment of the invention.Used shaped device is furnished with 11, one support tubes 18 of a shaping mould are used to cover this mould round this shaping mould 11 and a pair of lid 12 and 13 both ends open.These parts are combined into assembly 10.

In assembly 10, shaping mould 11 and lid 12 and 13 have been formed an actual mould, and have promptly formed a molding space 20 by the part that these parts surround.Simultaneously, the part that surrounds between support tube 18 and shaping mould 11 has then formed pressurization space 21.

Each lid 12 or 13 has a stepped part, and each part matches with each shaping mould 11 and support tube 18.In addition, on lid 12 and 13, in the middle part of its end step portion difference fluted 14 and 15.Bar-like member 31(explained later) two ends are coupled to respectively in groove 14 and 15, and by anchor clamps 17 they are separately fixed on lid 12 and 13.Sometimes, several aspirating holes 16 are arranged on the lid 13, these aspirating holes pass this lid and the internal surface that arrives (as required) can also link to each other the vacuum pump (not shown) in case of necessity with each aspirating hole from outside surface.Further, be equipped with a strainer can also for sometimes each aspirating hole 16.

Many import/exports opening 19 is arranged on the support tube 18, and pressure medium infeeds or leaves pressurization space 21 by these openings.

Before moulding, this assembly 10 is put into the pressurizing device (not shown), when pressure medium 22 was imported in this pressurizing device by pressurization donor (not shown), the outside from support tube 18 entered pressurization space 21 to this pressure medium 22 by import/export opening 19.Some examples as pressure medium 22 are water and lubricating oil.

Shaping mould 11 is made by resilient material, for example natural rubber, silicon rubber, urethanes or paracril, lid 12 and 13 and support tube 18 make by metal such as aluminium, support fixture 17 is made by resilient material such as rubber.Preferably to the internal surface of lid 12 and 13 (with the formed material actual contact) coating in addition, (trade name is a teflon, teflon), thereby prevents formed body, and promptly porous vitreum is polluted for example to be coated with fluoro-resin.

Bar-like member 31 is mainly used the Drawability material, and for example metal is made, and it can be by making in metallic surface coated glass or synthetic resins.In fact, bar-like member 31 can adopt any material, as long as this material has high ductibility and makes it to be unlikely in waiting static pressure process to make it not yielding because of pressure ruptures and has high strength.As previously mentioned, preferably use glass, synthetic resins, particularly fluoro-resin to apply this bar-like member 31, to prevent that this porous vitreum from being polluted.

Utilization is arranged in the bar-like member 31 of molding space 20, and formed material 32 is packed in the space 20.Exert pressure to shaping mould 11 by the pressure medium 22 in this pressurization space 21 then.Enclose the porous vitreum 33 that this bar-like member 31 of model forms as shown in Figure 2 thus.

The formed material that forms porous vitreum 33 contains quartz glass powder, or adulterated quartz glass powder, and a kind of powder in back for example can be the particulate powders that contains doping agent and silica glass.In the present invention, the example of some doping agents is GeO ₂, P ₂O ₅, B ₂O ₃Or F.

Formed material 32 can only be made up of quartz glass powder, also can be made up of the fused silica powder that contains solvent or moulding additive.The example of solvent can be a pure water, and the example of some moulding additives can be an organic compound, for example polyvinyl alcohol, polyvinyl butyral, polyoxyethylene, methylcellulose gum, carboxymethyl cellulose, ethyl cellulose, hydroxypropylcellulose and glycerine.The addition of these moulding additives (relatively glass powder) is 1 to 20%(weight ratio) be preferably 15% or still less.

The particle diameter of fused silica powder is usually between 0.01 μ m to 100 μ m.Preferably, mean diameter should be between 0.4 μ m to 25 μ m.This is because will be difficult to remove wherein impurity during less than 0.4 μ m in the purification step in the back when particle diameter, because by diameter is that 0.4 μ m or its aperture of granuloplastic formed material that is lower than 0.4 μ m are less, this will make gas used in the purification step such as Cl ₂, or the material that in this step, will remove such as HCl, FeCl ₃, CuCl ₂, NaCl and analogue thereof be difficult to pass through from these holes.In addition, the particulate mean diameter is 25 μ m or bigger, and it is too little that the cohesive force between the particle will become, to such an extent as to formed body might be broken because of low concreteness.

Simultaneously, when can not filling up molding space 20 equably, fused silica powder (when powder is too thin, can take place), formed porous vitreum might fragmentation, fracture, size change, and makes the density distribution of this porous vitreum too wide because of the inhomogeneous meeting of packing density.In addition, even bubble still can be stayed in the glass after the porous vitreum consolidation.In order to prevent this phenomenon, should use solvent such as pure water or solvent and moulding additive with superfine particle granulation, make particle diameter reach 30 μ m or bigger.Utilize through the particle powder of granulation can be evenly filling molding space to high-density, thereby solved the problems referred to above.

When actual employing aforesaid method solves this problem; preferably making particle diameter is that 30 μ m or bigger and particle diameter are that the content of 300 μ m or littler granulated powder is lower than 50% of total amount, and particle diameter is the content of 10 μ m or littler powder be lower than total amount 10% but be not less than 1% of total amount.Employing has the fused silica powder or the adulterated fused silica powder of above-mentioned size distribution, can further reduce the ununiformity of the density of loading powder.In the time will having the powder pressurization of distribution like this, thin particle will be bonded to each other macrobead between big granulated powder particle in addition.Make the porous vitreum of formation that fragmentation takes place as few as possible thus.

Preferably, this fused silica powder is by vapor phase process, makes as the flame hydrolysis of silicon tetrachloride and the high temperature oxidation of silicon or silicon tetrachloride, also can be to obtain by handling to increase the particulate diameter with the powder that aforesaid method makes.Further in fact, those are preferred by the powder that above-mentioned quartz particles granulation is obtained.These fused silica powders have high purity, and mainly are made up of particle spherical in shape; Therefore, can be formed on the formed body that is easy to purifying in the purification step of back with these powder.The example of another fused silica powder is by water glass or its granulated powder and obtain.Use the fused silica powder filling molding space 20 that obtains by water glass can obtain higher filling, thereby make the porous vitreum 33 rare fragmentations of making.Simultaneously, the fused silica powder that is obtained by water glass contains many silanol roots (OH root) on particle surface, so they need not to use binding agent granulating easily.In addition, the frangible performance of granulation particulate also can be controlled, and just can make large-sized formed body at an easy rate thus.Can use the fused silica powder of making by water glass separately, also can be with them with (as chemical vapor deposition method, the silica powder that CVD) makes is used in combination with other method.

In the present invention, porous vitreum 33 should be made tubular form, and its two ends preferably are taper type (being coniform), or makes the three-dimensional bending surface that radius-of-curvature is equal to or greater than the porous vitreum outside diameter, adopts said structure can obtain following benefit:

1. because the end is cone shape or three-dimension curved surface, the damage to the sintered glass end of body that might take place when porous vitreum is taken out from mould after the porous vitreum press molding just can be avoided, and can also reduce the possibility of porous vitreum fragmentation effectively.

2. because fibre-optical preform is to be made by the porous vitreum that the end is taper shape or three-dimension curved surface, the fixed of this porous vitreum will be from inserting an end of high temperature sintering furnace.So just can prevent to produce bubble, thereby obtain even, Clear ﹠ Transparent glass at the middle portion of fibre-optical preform.

3. can directly a support stick or analogue be fused on this prefabricated component when after fixed, prefabricated component being drawn into optical fiber, draw this optical fiber, thereby save the operating time and increase product production.

Above-mentioned moulding process can be for certain effect be only carried out at one end.

Utilize the pressure exerting device shown in Fig. 6 porous vitreum can be made above-mentioned shape, in the figure, the shaping mould 41a with interior shape corresponding with desired shape wherein can be used in the device as shown in Figure 4, also can cut into required shape as shown in Figure 7 by an end 33a and obtain above-mentioned shape the porous insert after the moulding.

In order to be easy to be filled into formed material 32 in the molding space 20 and to make formed material 32 be easy to be shaped, preferably earlier that these materials are wetting before being filled into formed material 32 in the molding space 20.With the formed material 32 wetting aerated densityes that can increase formed porous vitreum 33, suppress the absorption of 33 pairs of air of porous vitreum simultaneously.Therefore can prevent from silica glass preform, to produce bubble.To in forming process, be easy to fragmentation as the wetting powder that can make of the granulated powder of formed material 32 simultaneously, thus the porous silica glass prefabricated component that acquisition has uniform density.In the case, the moisture in the formed material can be equal to or higher than the 1%(weight ratio), but be lower than the 5%(weight ratio).

The technology that another kind is filled into formed material 32 in the molding space 20 with being used for filling a vacancy property of height is the static of removing in the formed material 32, removing static can carry out before being filled into formed material 32 in the molding space 20, also can carry out in these material filling molding spaces 20.Simultaneously, also should carry out static for the shaping mould 11 of forming mould and lid 12 and 13 and remove processing.Be not limited only to formed material 32 and mould, the surrounding environment of material stuffing operation also need be carried out static and be removed processing.

Can adopt commercially available static remover to remove static.The static remover utilizes high pressure to make gas ionization, and with Ionized gas distribution around object, or with Ionized gas injection to object, thereby remove static on this object.

Remove to handle by static, can prevent between the shaped granule self and this material and mould between the unnecessary attraction or the repulsion that cause because of static, can make the tamped density of this formed material 32 even thus.

Utilize above-mentioned formed material 32, can form porous vitreum 33 around bar-like member 31.After this this bar-like member 31 is extracted out from porous vitreum 33, formed hole 33a therefrom, seen in Fig. 3 A.Can when remaining on porous vitreum 33 in the mould, also can after from mould, taking out vitreum 33, bar-like member be taken out.

In the hole 33a that in porous vitreum 33, forms, insert a glass stick 34 then, shown in Fig. 3 B.

Glass stick 34 can be with CVD rule such as MCVD, VAD, OVD and with quartzy sintered glass parts purifying and consolidation and make, and this glass component can make with extrinsion pressing, MSP method (mechanical forming method), shaping method to suppress, slip casting method, sol-gel method, slurry coating method, powder method or similar approach.This glass stick 34 can only be made by core glass, also can be made by the core glass of some coating glass of paripheral zone.

After glass stick 34 is inserted in the hole, with currently known methods with these porous vitreum 33 purifying, and then consolidation.Purge process is normally containing Cl ₂Atmosphere in carry out; But treat as when having added some organic compound such as moulding additive in the section bar material, also can adopt other purge process, i.e. oil removing, this moment, this organic compound decomposed because of being heated, and also can make its decomposition by oxidation in case of necessity.Containing Cl ₂Atmosphere in when carrying out purifying, this purge process can for example under 1250 ℃, at Cl ₂With carry out under the He atmosphere, in this step, metallic impurity such as Na, Ca, Fe, Cu and analogue thereof can be removed and realized dehydration (removing the OH root).The consolidation process for example can be carried out under 1600 ℃ in He atmosphere, and in this step, porous vitreum 33 is converted to transparent vitreum 35, obtains the silica glass preform of being made up of glass stick 34 and transparent vitreous body 35 36 thus.Should be pointed out that sometimes purge process and consolidation process to be placed in the step and carry out.In addition, in this scheme, purge process and consolidation process are to carry out afterwards glass stick being inserted because of bar-like member 31 being extracted from porous vitreum 33 in the hole that the back forms, but that the order of this technology is not limited to is top a kind of.For instance, can after purifying porous vitreum 33, replace bar-like member 31 with glass stick 34 again, if after bar-like member 31 is taken out, carry out purifying and then glass stick is inserted in the hole effect too from vitreum 33.

According to aforesaid method, forming in the process of porous vitreum around glass stick with isostatic pressing method, glass stick and porous vitreum all can not be damaged, and so just can prepare silica glass preform by high yield.In addition, because porous vitreum is to be become transparent glass by consolidation when bonding to glass stick, so on transparent vitreous body that forms thus and the interface between the glass stick, can produce bubble hardly.

Example to another kind of shaped device is described now.Fig. 4 is the cross-sectional view that can be used for the major portion of the another kind of shaped device in the inventive method.This shaped device comprises shaping mould 41, surrounds into the support tube 48 of pattern 41, and at a pair of

moulding drift

42 and 43 at these parts two ends.These parts are combined into ligand 40.

Be furnished with

groove

44 and 45 on the

moulding drift

42 and 43 respectively, these two grooves are positioned at the middle part of the internal surface of each drift.Matching with

groove

44 and 45 in the two ends of bar-like member 61, and is fixed on moulding

drift

42 and 43 by anchor clamps 47.As required, can have aspirating hole 46 on the moulding drift 43 sometimes and pass its internal surface up to outside surface.Under the situation of perforate, can also in aspirating hole 46, be equipped with a strainer (not shown).

Shaping mould 41 and moulding

drift

42 and 43 have been formed mould, and promptly are molding spaces 50 by the part that these parts surround, and in addition, the parts of being determined by support tube 48 and shaping mould 41 promptly become pressurization space 51.

Lid

54 and 55 is secondary stepped appearance tubular shape, and they are respectively around moulding

drift

42 and 43 and put, corresponding to being furnished with a pressure transmission mould 53 by the outer surface of shaping mould 41 with the part of

lid

54 and 55 pressurization spaces of determining 51.

Be furnished with a plurality of import/exports opening 49 on the support tube 48, be used for pressure medium 52 is sent into pressurization space 51 and therefrom discharged pressure medium.

During actually operating, ligand 40 is placed in the pressurizing device (not shown), and when pressure medium 52 was admitted to pressurizing device, the outside from support tube 48 entered pressurization space 51 to this pressure medium 52 by import/export opening 49.

Shaping mould 41 can adopt with the similar resilient material of foregoing mould 11 and make, and support fixture 47 is made by resilient material such as rubber, and is described to support fixture 17 as the front.Other parts are made by metal such as aluminium.In addition, and preferably apply for example fluoro-resin on the

moulding drift

42 and 43 of formed material actual contact,, thereby prevent that promptly the sintered glass that forms produces and pollutes as the internal surface of lid 12 and 13 organizer.

Simultaneously, according to preparing bar-like member 61 with the similar mode of bar-like member 31.Utilization is arranged in the bar-like member 61 of molding space 50, and formed material 62 is inserted in the space 50.Then, exert pressure to shaping mould 41 by the pressure medium 52 that is contained in the pressurization space 51.Form porous vitreum around bar-like member 61 thus, as shown in Figure 4.

Following step is all carried out in the mode similar to foregoing mode.

In Fig. 1 to 7, all protrude to the outside of porous vitreum (as 33 among Fig. 2) at the two ends of bar-like member (for example 31 among Fig. 1), but this structure is not to be required in this invention, though an end wherein preferably should outwards protrude, but they needn't always outwards protrude, when wherein having an end outwards to protrude, just can open a hole at an easy rate at the center of porous member.

Various details embodiment.

Example 1

In this example, formed material 32 only adopts commercially available silica powder, and its average particulate diameter is 20 μ m, adopts shaped device shown in Figure 1 to prepare porous vitreum.

Shaping mould 11 usefulness silicon rubber are made, and its external diameter is 60mm, and internal diameter is 50mm, and long is 270mm.By shaping mould 11 and lid 12 and 13 molding space 20 its useful lengths (highly) of determining is 250mm, is coated with teflon (trade(brand)name) on lid 12 and 13 the internal surface.

Bar-like member 31 is formed from steel, and it is 10.6mm that outside surface is coated with its external diameter of teflon, and long is 270mm.

When infeeding formed material 32, take off lid 12 from this ligand, bar-like member 31 is inserted in the molding spaces 20, packed in the groove 15 in its lower end.Then 420 grams are infeeded in the molding space 20 through vacuum treated formed material 32, it is airtight with this space to add upper cover 12.

As required, the vacuum pump (not shown) can be connected on the aspirating hole 16, be used for molding space 20 is vacuumized, simultaneously, will be injected into the pressurization space 21 as the lubricating oil of pressure medium 22 from the pressure medium plenum system (not shown) that links to each other with import/export opening 19.Thus with shaping mould 11 at 1000kgf/cm ²Pressure pressurizeed about 1 minute down.

As a result, in molding space 20, formed the uniform porous vitreum 33 of aerated density, can't see broken situation in the product around bar-like member 31.Porous vitreum 33 its external diameters of being made by formed material 32 are about 42mm, and long is 250mm.

Undoubtedly, also not damage on bar-like member 31.

Then, discharge pressure medium 22 gradually from pressurization space 21, the time is approximately 30 minutes, so that shaping mould 11 is recovered.After shaping mould 11 restores, take off lid 12, porous vitreum 33 and bar-like member 31 are taken out from molding space 20 together.

Then, as shown in Figure 3A, bar-like member 31 is taken out from porous vitreum, and shown in Fig. 3 B, a quartz glass bar 34 is inserted among the hole 33a that forms thus.The diameter of this glass stick 34 is 10.6mm, and long is 270mm.In addition, for this glass stick, the external diameter of core glass is 1: 4 with the external diameter ratio that coats glass, and the refractive index contrast △ of core glass and skin glass is 0.35%.

Then, with the porous vitreum 33 that inserts and glass stick 34 under 1250 ℃, Cl ₂With purifying in the He atmosphere (removing impurity and dehydration), and then under 1600 ℃, consolidation in the He atmosphere.As a result, porous vitreum 33 is transparent vitreum 35 by clinkering, forms the glass preform for optical fiber of being made up of glass stick 34 and transparent vitreous body 35 36 shown in Fig. 3 c thus.

Fibre-optical preform 36 its external diameters that obtain thus are 35mm, can't see bubble on the interface of glass stick 34 and transparent vitreous body 35.

This fibre-optical preform 36 is carried out fibre-optical drawing, thereby make a kind of single-mode fiber, its core diameter is about 10 μ m, and external diameter is 125 μ m, after the drawing, apply the optical fiber that is produced with the ultraviolet-curing resin coating immediately, thereby its coating external diameter is 400 μ m.

Verified, the coating optical fibre that obtains thus has and the identical performance of mainly making by the CVD method of single-mode fiber.

For purpose relatively, use the technology identical to make another porous vitreum with above-mentioned technology, wherein adopting external diameter is 8mm, the external diameter ratio of core glass and skin glass is that 1: 3 and its cutoff wavelength design load are that the quartz glass bar of 1.30 μ m replaces bar-like member.

For above-mentioned example and Comparative Examples, measure the breaking property of each bar-like member, the broken incidence of each porous vitreum, the result is as follows:

Example:

Breaking property=the % of bar-like member

Broken incidence=10% of porous vitreum

Comparative Examples:

The breaking property of bar-like member=80%

Broken incidence=60% of porous vitreum

Can clearly be seen that from The above results in example, bar-like member never ruptures, the rare fragmentation of its porous vitreum, and in Comparative Examples, bar-like member often ruptures, so fragmentation also often takes place in its porous vitreum.

Example 2

In this example, formed material 32 is that the silica powder granulation of 0.7 μ m makes by the particle diameter that can buy from the market, and granulating adopts following technology to carry out.At first in fused silica powder, add pure water, form slip.Then with this slip spray-dryer granulation.Do not add binding agent in the granulating, also do not add dispersion agent in slip before the granulation, made its median size of granulation formed material powder is 50 μ m, and median size is that 30 μ m or higher powder account for more than 50% of whole powder.In addition, particle diameter accounts for 5% of whole powder at 1 μ m or littler fine powder.

Utilize this formed material 32 and the bar-like member identical with example 1, form porous vitreum 33 with the technology similar to example 1 around bar-like member, thus obtained porous vitreum 33 is 42mm with the same its external diameter in the example 1, and length is 250mm.

Obviously, do not produce damage in the bar-like member 31.

After this, will insert porous vitreums 33 with identical glass stick in the example 1 34, then with this porous vitreum 33 under 1250 ℃, at Cl ₂With carry out purifying (remove impurity and dehydration) in the He atmosphere, with purified porous vitreum 33 under 1600 ℃, further consolidation in He atmosphere, make it consolidation and become transparent vitreum 35, obtain the fibre-optical preform of forming by glass stick 34 and transparent vitreous body 35 36 shown in Fig. 3 c therefrom.Surface in contact place between glass stick 34 and transparent vitreous body 34 finds no bubble.

Adopt the technology identical with example 1 that this fibre-optical preform 36 is made coating optical fibre, its shape is identical with example 1.

The cutoff wavelength of thus obtained coating optical fibre is the same with design load to be 1.30 μ m.

In order to carry out to this, the fine-grained quartz glass powder that only adopts median size to be about 8 μ m is made product (Comparative Examples 1) as formed material 32, in addition, only adopting median size again is that the fused silica powder of 50 μ m is made another kind of product (Comparative Examples 2) as formed material 32, and these two kinds of products are detected.

For above-mentioned example and Comparative Examples 1 and Comparative Examples 2, measure the tamped density of its fused silica powder in molding space and the difference of tamped density, its result is as follows:

Example 2:

Tamped density 0.88g/cm ³

Tamped density is poor ± and 0.02

Comparative Examples 1:

Tamped density 1.12g/cm ³

Tamped density is poor ± and 0.08

Comparative Examples 2:

Tamped density 0.81g/cm ³

Tamped density is poor: ± 0.05

Can clearly be seen that by The above results though the tamped density of example 2 is lower than Comparative Examples 1, its tamped density difference is low more a lot of than Comparative Examples 1 and Comparative Examples 2.The tamped density that should be pointed out that example 2 is enough good, and its product can be used for physical condition.

Example 3

In this example, formed material 62 adopts the silica powder that can from the market buy similar to example, and its median size is 0.7 μ m, and used shaped device as shown in Figure 4.At first in fused silica powder, add pure water and make it to become slip shape material; then with spray-dryer with its granulation; thereby obtain formed material 62; do not add binding agent in the granulating, in slip, do not add dispersion agent before the granulation, in the formed material of making thus 62 yet; particle diameter is that 1 μ m or littler particulate powders account for below 9.5%; other then is the powder that median size is about 50 μ m, and in fact, its median size of the powder more than 50% is 30 μ m or more than the 30 μ m.

Shaping mould 41 is made by silicon rubber, and external diameter is 60mm, and internal diameter is 50mm, longly is 600mm.By shaping mould 41 and

moulding drift

42 and 43 molding space 50 its useful lengths (height) of determining is 480mm.Be coated with teflon (trade(brand)name) on used

moulding drift

42 and 43 the internal surface.

When infeeding formed material 62, take off drift 42 from ligand, bar-like member 61 is inserted in the molding spaces 50, packed in the groove 45 in its lower end.Then about 810 grams are infeeded in the molding space 50 through vacuum treated formed material 62, with the moulding drift that the space is airtight.

After this, as required, can molding space 50 be vacuumized by the vacuum pump (not shown) that links to each other with aspirating hole 46, simultaneously, will inject pressurization space 51 as the lubricating oil of pressure medium 52 from the pressure medium plenum system (not shown) that links to each other with import/export opening 49.Thereby at 500kgf/cm ²Under the pressure shaping mould was pressurizeed about 1 hour.

As a result, in molding space 50, formed the uniform porous vitreum of aerated density, do not seen fragmentation in the product around bar-like member 61.Porous vitreum 33 its external diameters of being made by formed material 62 are 40mm, and long is 480mm.

Then, discharge pressure medium 52 gradually from pressurization space 51, the time is approximately 1 hour, so that shaping mould 41 is recovered, after shaping mould 41 restores, takes off moulding drift 42, and porous vitreum is taken out from molding space 50 with bar-like member 61.

Then, extract bar-like member 61 out from porous vitreum, and glass stick is inserted on the porous vitreum in the formed hole, the diameter of this glass stick is 10.6mm, longly is 500mm.For this glass stick, the external diameter of its core glass is 1: 4 with the external diameter ratio of skin glass in addition, and the refractive index contrast △ of core glass and skin glass is 0.35%.

With porous vitreum with inserting wherein glass stick under 1270 ℃, at Cl ₂With purifying in the He atmosphere (remove impurity and dehydration), subsequently under 1630 ℃, consolidationization in He atmosphere.Thus, the porous vitreum consolidation is become transparent vitreous body, thereby make the fibre-optical preform of forming by glass stick and transparent vitreous body.In the transparent vitreous body of this prefabricated component, do not find bubble.

Adopt the method identical that fibre-optical preform is made the similar coating optical fibre of structure and example 1 then with example 1.The cutoff wavelength of this coating optical fibre is the same with design load to be 1.28 μ m, and on vertical cutoff wavelength difference performance, it has identical characteristics with the optical fiber of mainly making by the CVD method.

Should be noted that the same good of its tamped density and tamped density difference and example 2.

Example 4

In this example; employing shaped device formed material as shown in Figure 4 is by making from the fused silica powder granulation of water glass; the median size of original fused silica powder (before the granulation) is approximately 0.5 μ m, and the median size of the powder after the granulation is 100 μ m.

Moulding process is identical with example 3 basically, and difference is that this example adopts above-mentioned powder as formed material, and shaping mould 41 is made by paracril (NBR), and also having forming pressure is 1000kgf/cm ²

Do not have fragmentation in the porous vitreum of making thus, when the restorer in the shaping mould 41 produces too soon, might cause fragmentation.

Subsequent, resemble and porous vitreum purifying and consolidation are become transparent vitreum the example 3.

The transparent vitreous body that will make with fused silica powder from water glass with wet quartz (the wet quartz of granulation of other fused silica powder; or natural quartz) other transparent vitreous body that makes compares; powder tamped density in mould more each other; the output of porous vitreum and the output of transparent vitreous body, it the results are shown in the following table 1.

Table 1

Material tamped density output %

(g/cm ³) the porous vitreum transparent vitreous body

Water glass 0.90 90 90

Wet quartzy 0.40 40 70

Granulation natural quartz 1.00 10 50

From table 1, can know and find out, higher by its tamped density of fused silica powder that water glass is made, each stage, the product output that promptly forms porous vitreum and transparent vitreous body is also higher, can prove thus when fused silica powder that employing is obtained by water glass prepares silica glass preform to obtain good especially performance.

Example 5

In this example; adopt shaped device as shown in Figure 4 and the fused silica powder that makes by water glass; these fused silica powders are the granulometric composition of 0.7 μ m by median size; and by to wherein adding and they are made slip as the pure water of solvent; the proportion of slip is 60%; utilize spray-dryer with the fused silica powder granulation, formed particulate mean diameter is 50 μ m.

Then, resemble the example 4 these fused silica powders around bar-like member 61 and form porous vitreum.From porous vitreum, extract bar-like member out, and a glass stick made from the CVD method is inserted in the hole that forms thus.For this glass stick, its core glass is 1: 4 with the external diameter ratio of skin glass.

After this, resemble and porous vitreum purifying and consolidation are become transparent vitreum the example 3, obtain the fibre-optical preform formed by glass stick and transparent vitreous body thus, with conventional drawing technology this fibre-optical preform is drawn into optical fiber, the optical fiber of Xing Chenging has identical performance with the optical fiber that makes with CVD method or its similar approach thus.

Example 6

In this example, shaped device forms 62 silica powders that adopt granulation of section bar material as shown in Figure 4, and it is to form by the silica powder granulation that median size is about 0.7 μ m.The median size of granulated powder is 50 μ m, and the moisture in the granulated powder is about 0.5%.

Granulated powder is wetting in a temperature and humidity constant container, and wet processes is to be fixed on 40 ℃ in temperature, and humidity is to carry out under 70% the condition.Under these conditions, the humidity of granulation silica powder is enhanced 3%, and humidity is measured with infrared hygronom, should be understood that if humidity is brought up to 5% or higher, will some granulated powder be transformed into primary particle again, thereby can lower the filling properties of powder.

Used shaping mould 41 its internal diameters are 50mm, make by paracril, and approximately be 250mm by the useful length (highly) of shaping mould 41 and

moulding drift

42 and 43 molding spaces of determining.

Utilize above-mentioned facility; according to identical with example 3 basically mode around bar-like member 61 and form porous vitreum; its difference is that this example is that the formed material 62 that 420 grams are made by wetting granulated powder is inserted in the molding space 50, and forming pressure is adjusted into 1000kgf/cm ²

After this, applied pressure was reduced in the clock time at 20 minutes gradually to prevent fragmentation, if the restorer in the shaping mould 41 produces too soon then might cause fragmentation when pressure descends.

The step of back can be carried out according to foregoing mode, does not find broken in the porous vitreum that makes thus.

Then, bar-like member is extracted out from porous vitreum, and inserted glass stick in formed hole, its core glass of used glass stick is 1: 4 with the external diameter ratio of skin glass, and its diameter is 10.6mm, and long is 270mm.

As example 3,, make it to be transformed into transparent vitreum with this porous vitreum purifying and consolidation.Made the fibre-optical preform of being made up of glass stick and transparent vitreous body thus, do not have bubble in this prefabricated component, this fibre-optical preform is drawn into optical fiber, thus obtained optical fiber has identical performance with the optical fiber that makes with CVD method or similar approach.

In order to compare, adopt granulation silica powder to contrast organizer by make one with sampling technology without moist curing.The density of the organizer of comparative example and Comparative Examples and porosity the results are shown in the following table 2.

Table 2

The density that forms material forms the porosity of material

（g/cm ³）（%）

Wetting 1.30 43.8

Without wetting 1.23 46.3

As can be seen from Table 2, to form that material is wetting can be improved its density and reduce its porosity, be reduced (as shown in table 2) owing to form the porosity of material, air capacity contained in this material also will descend thereupon, and not have bubble to produce in transparent vitreum.

According to the mode identical with example 1 with shaping mould 11 pressurizations, pressure was reduced gradually so that shaping mould 11 is unlikely to return to too apace its normal position in the clock time at 30 minutes, after shaping mould 11 recovers, take lid 12 away and bar-like member 31 is taken out from molding space 20 with porous vitreum.

Obtain not have the porous vitreum of bubble thus.

After this, bar-like member is extracted out from porous vitreum, and a glass stick inserted in the formed hole, used glass stick is with the axial vapor deposition method of VAD(, a kind of in the CVD method) method is made, its core glass is 1: 3 with the external diameter ratio of skin glass, and its external diameter is 7.8mm, and long is 260mm.

According to the mode identical with example 1, porous vitreum purifying and the consolidation that forms thus become transparent vitreum, make the fibre-optical preform of forming by glass stick and transparent vitreous body thus, the external diameter of this prefabricated component is about 35mm, and long is 235mm.

With currently known methods this fibre-optical preform is drawn into optical fiber, after measured, the cutoff wavelength of this optical fiber is the same with design load to be 1.30 μ m, at vertical cutoff wavelength difference aspect of performance, here the optical fiber that is obtained with use the CVD method, the optical fiber that makes as the VAD method has same performance.

Simultaneously, the removal through static formed material of handling and the formed material of handling without the static removal are compared, compare the tamped density of its material, the number of bubbles in tamped density difference and the transparent vitreous body, its result is as shown in table 3 below.

Table 3

Remove electrostatic and do not remove electrostatic

Tamped density (g/cm ³) 0.95 0.90

The variation range of tamped density ± 0.05 ± 0.08

Number of bubbles 10 30 in the transparent vitreous body

Can clearly be seen that by table 3, remove the variation range that static can improve the tamped density of formed material and dwindle tamped density, thereby reduce the number of bubbles that remains in transparent vitreous body and the product thereof.

Example 7

In this example, adopt the shaped device of structure as shown in Figure 4, its difference is that this device comprises shaping mould 41a, and it is the three-dimensional bending surface in two ends up and down, as shown in Figure 6.At first 1700 gram particle fossil English glass powder are inserted in the molding space 50.Used fused silica powder is that to be dispersed in the water and with spray drying technology they to be granulated into median size by the quartz particles that is 8 μ m (trade(brand)name: Exelica SE-8, Tokuyama Soda Co.) be that the particle of 150 μ m is made with median size.Before particle is inserted molding space 50, earlier a stainless steel bar 61 is placed on the position, intermediate portion, the external diameter of rod iron 61 is 14mm, the teflon that the surface is coated with applies 1500kgf/cm by the water as pressure medium 52 to shaping mould ²Pressure, thereby around bar-like member 61 and insert silica powder 62, be 1 to 5 minute clamping time.

The result, formed porous vitreum around bar-like member 61, then, from this vitreum, extract bar-like member out, and in the hole that forms thus, insert an optical fiber glass plug, its core glass is 1: 3 with the external diameter ratio of skin glass, and external diameter is 14mm, obtains shape the porous vitreum as fibre-optical preform identical with Fig. 5 B thus.After this, by carrying out purifying and consolidation like that described in the example 1, obtaining external diameter thus is the transparent fibre-optical preform of 70mm with the porous vitreum that produced.Then, this fibre-optical preform is drawn into the optical fiber with core and foreskin, its performance is identical with the optical fiber that makes with VAD method (in the CVD method a kind of).

Example 8

In this example, adopt formed material hereinafter described to replace material therefor in the example 7, make matrix material of optic fibre with this.Its result is described below.

(1) with median size is the quartzy fine particle (trade(brand)name: Exelica SE-1 of 0.3 μ m; Tokuyama Soda Co.) is dispersed in the water; thereby forming median size is the granulation silica powder of 150 μ m; made powder is made transparent silica glass; contain 5ppm Fe in verified this transparency silica glass, it is not suitable for being used for making optical fiber.

(2) being that the quartzy particulate (trade(brand)name: Admafine SO-25R, Admatex Co.) of 0.6 μ m is dispersed in the water with median size, is the granulation silica powder of 150 μ m thereby form median size.The powder that obtains is made highly purified silica glass, contain 50ppb Fe in verified this silica glass, it is fit to be used for making optical fiber.

(3) be that the quartzy particulate (trade(brand)name: Elsil, Mitsubishi Metal Co.) of 29 μ m is dispersed in the water with 3%PVA with median size, making median size thus is the granulation silica powder of 150 μ m.Its physical strength of moulding porous vitreum that is produced a little less than, it is not suitable for being used for making fibre-optical preform.

In the above-described embodiments, we are the forming process that example has mainly been discussed fibre-optical preform with the silica glass preform.But need not explicit word, also can adopt the technology similar to prepare to pass to resemble fiber, optical waveguides or the used prefabricated component of post lens to above-mentioned example.

The present invention can also have some other advantage and improvement for those skilled in the art, and therefore, the present invention is not limited to its described in this article detail and described embodiment in a broad sense.Therefore, under the situation of the spirit or scope that do not break away from the of the present invention total invention thought that limits by appended claims and equivalent thereof, also can make various improvement.

Claims

1, a kind of preparation method of silica glass preform is characterized in that it comprises the following steps:

The bar-like portion (31,61) that mainly contains metallic substance is inserted in the molding space (20,50) of mould (11,12,13,41,42,43);

In the molding space (20,50) of remainder, insert the formed material (32,62) that contains fused silica powder or adulterated fused silica powder;

To the mould that fills up formed material (32,62) (11,12,13,41,42,43) pressurization, form porous vitreum (33) from the outside thereby make this formed material (32,62) center on bar-like member (31,61);

From porous vitreum (33), take bar-like member (31,61) away, thereby after taking bar-like member away, form a hole (33a);

In a glass stick (34) patchhole (33a);

To insert porous vitreum (33) purifying of glass stick (34); And

Will purified porous vitreum consolidation in above-mentioned purification step.

2, the described method of claim 1 is characterized in that described preparation process is by in sequence following:

The bar-like member (31,61) that mainly contains metallic substance is inserted in the molding space (20,50) of mould (11,12,13,41,42,43);

From the outside to the mould that fills up formed material (32,62) (11,12,13,41,42,43) thus make should be at section bar material (32,62) around bar-like member (31,61) formation porous vitreum (33) in pressurization;

With porous vitreum (33) purifying that forms;

In a glass stick (34) patchhole (33a);

3, the described method of claim 1 is characterized in that described preparation process is by in sequence following:

To take porous vitreum (33) purifying of bar-like member (31,61) away;

In a glass stick (34) patchhole (33a); And

4, the described method of claim 1 is characterized in that described bar-like member (31,61) made by the metal of surface-coated glass or synthetic resins.

5, the described method of claim 1 is characterized in that described formed material (32,62) is a silica powder, and its mean diameter is between 0.4-25 μ m.

6, the described method of claim 5 is characterized in that containing in the described formed material (32,62) 50% or the higher granulated powder of particle diameter between 30 μ m-300 μ m, and described granulated powder is made by described silica powder.

7, the described method of claim 6; it is characterized in that described formed material (32; 62) contain in 50% or higher particle diameter at 30 μ m or bigger to 300 μ m or littler granulated powder, and 1% or higher and particle diameter below 10% at 10 μ m or littler powder particle.

8, the described method of claim 1 is characterized in that containing in the described fused silica powder powder from water glass.

9, the described method of claim 1 is characterized in that it also further comprises from described formed material (32,62) to remove the electrostatic step.

10, the described method of claim 9 is characterized in that it also further comprises to remove the electrostatic step from described mould.

11, the described method of claim 1 is characterized in that described formed material (32,62) is wetted before being received in molding space.

12, the described method of claim 11 is characterized in that the humidity of described formed material (32,62) is equal to or higher than 1wt% and is lower than 5wt%.

13, the described method of claim 1 is characterized in that porous vitreum (33) has at least an end to be cut coning shape, perhaps forms the three-dimension curved surface that radius-of-curvature is equal to or greater than porous vitreum (33) external diameter.

14, the described method of claim 1, it is characterized in that wherein used fused silica powder is by chemical vapor deposition method, as flame hydrolysis, oxidizing reaction, pyrolytic reaction technology makes, and also can handle making by the silica powder that will make thus.

15, the described method of claim 1 is characterized in that wherein used fused silica powder by the metal silicate oxidation is made, and also can handle making by the silica powder that will make thus.

16, the described method of claim 1 is characterized in that described bar-like member (31,61), and it has at least an end to protrude to the outside of described porous vitreum (33).