CN85101900A - The manufacture method of optical glass fibre - Google Patents

Abstract

Draw the production method of fibre-optic glass preform, be included in the oxyhydrogen flame flame hydrolysis frit to form glass granules, glass granules is deposited on the seed spare to produce a kind of solid or hollow cylindrical deposition precast billet, whole deposition precast billet is placed in the atmosphere that contains a kind of dewatering agent, in that being shunk in 20% time and the temperature at least, deposition precast billet diameter makes its dehydration, the deposition precast billet that to take off water sends into from the one end that heating and sintering make the glass preform of production have the longitudinal refractive index uniform distribution the pure inert atmosphere, and the fibre-optic light transmission (wavelength is 1.30 microns) that is drawn by above-mentioned glass preform decays and is equal to or less than 1 decibel/km.

Description

The manufacture method of optical glass fibre

The invention relates to the manufacture method of optical fiber glass precast billet.Especially relate to the method that a kind of glass that utilizes flame hydrolysis to make to draw optical fiber to use gives base, give optical fiber that base is drawn into this glass and vertically form evenly, optical transmission attenuation is low.

Be applicable to that scale operation draws the manufacture method that fibre-optic glass gives base " VAD "-axial vapor deposition method and " OVPD "-outer vapour deposition process are arranged.All may further comprise the steps in two kinds of methods: in oxyhydrogen flame, use the flame hydrolysis frit, as contain or do not contain additive (GeO for example ₂) SiCl ₄, form pure silica glass particulate (SiO ₂) or contain the additive silica glass particulate of 0.1 micron of granular size average out to; Make the silica glass particle deposition on seed spare, generate the porous deposition and give base; At high temperature sintering generates transparent glass and gives base.

In " VAD " method, the silica glass particle deposition constantly forms the cylindrical deposition of real core and gives base (referring to United States Patent (USP) 4,135,901) on the rotation seed spare parallel with seed spare turning axle on seed spare.And in " OVPD " method, the silica glass particle deposition with the rotation seed rod made from aluminium or silica glass of rotation seed spare vertical direction on, form many thin layers glass granules (referring to United States Patent (USP) 3,711,262; 3,737,292; 3,737,293).

Then, in inert atmosphere (as helium), the porous deposition is given base heat-agglomerating, become transparent glass and give base with high temperature.

Fibre-optic application request has low optical transmission attenuation.Especially be that fibre-optic light transmits overall attenuation should be less than 1 decibel/km in 1.30 microns the remote optical communications using wavelength.Like this, will reduce moisture residual in the optical fiber (being hydroxyl), otherwise it is 1.38 microns a light with absorbing wavelength, and influence is 1.30 microns light transmission with wavelength.Fig. 1 is the amount of residual moisture content in the expression optical fiber and the relation between light transmission (wavelength the is 1.30 microns) decay.This shows that if residual moisture content is less than 0.3ppm in the optical fiber, then optical transmission attenuation is just less than 0.3 decibel/km.

Because theoretical light transmission (wavelength the is 1.30 microns) attenuation range that limits glass material is 0.3-0.4 decibel/km.So the total attenuation range of light transmission is 0.6-0.7 decibel/km.

In order to make light transmit overall attenuation less than 1 decibel/km, be necessary to reduce the other factors that causes optical transmission attenuation, especially to reduce the absorption of impurity (as transition metal copper and iron) as much as possible.

The amount of impurity element during 20 decibels/km of table 1 expression light transmission (wavelength is 0.8 micron) decay.

Table 1

By table 1 as seen, in order to reduce fibre-optic optical transmission attenuation, importantly will reduce in the optical fiber foreign matter content below 1ppb, are 1/5th of copper optical transmission attenuations of causing 0.8 micron wave length owing to copper causes the optical transmission attenuation of 1.30 micron wave lengths.

In addition, the bubble in the optical fiber also will cause the decay that light transmits.The generation of these bubbles mainly is to be used to deposit the chlorine that gives the base dewatering agent or for regulating specific refractory power as additive CeO ₂Caused.

At present, can produce huge optical fiber glass and give base, give base as can draw the long fibre-optic big glass of 200 kms with " VAD " manufactured, this huge glass gives base and requires to have smaller glass and give the more all even in the vertical more stable composition of base.

According to reaction formula I and (II), give that base dewaters and during sintering in deposition, GeO ₂Volatilize,

When temperature is higher than 800 ℃:

When temperature is higher than 900 ℃:

Wherein (g) represents gaseous state.Therefore, GeO ₂Volatile quantity change along with the slight variation of the dehydration and/or the flow velocity of sintering condition (as temperature) and chlorine.The index distribution that its result makes glass give base changes.

For example, according to United States Patent (USP) 3,993,454 disclosed methods are containing GeO ₂SiO ₂Glass is that deposition that core is formed is given base and progressively sent into sintering in the sintering oven from stove one end, and atmosphere is that the refringence that transparent glass that the helium (i.e. " gradient sintering method ") that contains chlorine makes gives between the base two ends is 0.3% in the stove, accordingly GeO ₂Weight difference is 5%.

Another method that present known sintered deposit gives base is whole deposition to be given base send in the atmosphere that contains chlorine, makes temperature progressively be raised to sintering temperature, deposition is given base sinter transparent glass into and give base (referring to United States Patent (USP) 4,338,111).Though this method is applicable to the base that gives of making the longitudinal refractive index distributional stability, and a shortcoming is arranged, it was produced gives base and glass with the production of gradient sintering method and gives base and compare and contain numerous air-bubble.

First purpose of the present invention provides the method that glass that a kind of production longitudinal refractive index is evenly distributed gives base.Second purpose provides a kind of method that glass gives base of producing, and is equal to or less than 1 decibel/km with this fibre-optic light transmission (wavelength is 1.30 microns) decay of giving the base drawing.

Therefore, the invention provides a kind of method that optical fiber glass gives base of producing.Flame hydrolysis frit in oxyhydrogen flame, form glass granules, and be deposited on the seed spare, thereby the deposition that obtains solid or hollow cylinder is given base, whole deposition is given base place the atmosphere that contains dewatering agent, shrink at least 20% time and the temperature at the diameter that can make whole deposition give base and to dewater, the deposition of dehydration is given base send in the pure inert gas atmosphere, heating and sintering since an end.

Fig. 1 represents the relation between residual moisture content in the optical fiber and light transmission (wavelength the is 1.30 microns) attenuation change thereof.

Fig. 2 represents GeO ₂Relation between volatile quantity and temperature.

Fig. 3 represents GeO ₂Chlorine turn into and temperature between relation.

Fig. 4 represents to be used for the stove of gradient sintering method.

Fig. 5 represents to be used for the another kind of stove of embodiments of the invention.

According to the present invention, find to utilize United States Patent (USP) 3,993, the prepared deposition of 459 disclosed production methods is given base, and one of unsettled reason of its refractive index is deposition to be given base one end progressively send in dehydration and the sintering atmosphere and dewater and sintering i.e. gradient sintering method, therefore, GeO₂Volatile quantity change along with the slight variation of dehydrating agent flow velocity and/or temperature, in case the GeO and/or the GeCl that have volatilized₄With GeO₂Be deposited on deposition and give on the base, thereby cause deposition to give the change of base refractive index; Another reason is to dewater making under the high temperature that gives the base transparence.

Contain GeO by handle₂SiO₂Deposition is given base and is heated in helium, has tested out GeO₂Volatile quantity and the relation between heating-up temperature, as shown in Figure 2, can find out from figure GeO₂Volatile quantity increase along with the rising of temperature. For example, GeO 1500 ℃ the time₂Volatile quantity GeO during than 1100 ℃₂Large five times of volatile quantity, (8th Conference of Optical Communication, C-25,629-632(1982)).

That Fig. 3 represents is GeO ₂Relation between chlorineization and temperature.As seen from the figure, GeO ₂Volatile quantity raise along with temperature and increase, according to test of the present invention, GeO ₂Volatile quantity (V) and the relation between temperature (T) can be expressed from the next:

V＝A×exp（+40×10 ³/RT）……（Ⅲ）

Wherein, A is a constant.R=1.987 card/mole, T are absolute temperature (° K), thus formula as can be known, the volatilization kinetic energy be 40 kcal/mol.

Through above-mentioned discussion as can be known, because GeO ₂Volatilization utilizes the gradient sintering method consumingly, makes under the such high temperature that gives the base transparence, and go that production is had glass that longitudinal refractive index is evenly distributed and give base and dewater, be not too suitable.

The formation problem of bubble is also studied.According to United States Patent (USP) 4,338,111 methods of describing, when whole deposition being given base when being controlled in the sintering atmosphere, form bubble, the reason that forms bubble is set as follows: when whole deposition being given base when being controlled in the sintering atmosphere, because its surface at first is transformed into transparent glass, like this by GeO ₂The GeO that generates ₂And/or GeCl ₄Still remain in the deposition that does not also become transparent glass and give the poriferous circular position of base.Heat-up rate is big more, and the diameter that deposition is given base is big more, and the bubble of formation is also many more.For example, diameter is that 80 millimeters deposition is given base considerable bubble is just arranged, and length is 50 centimetres, and diameter is that 120 millimeters or bigger deposition are given and just contained 3-8 the bubble that naked eyes can be seen in the base.Give the base diameter when big when deposition, radially the tap density change is very big for it.The temperature difference in surface and centre is bigger, has 100 ℃ approximately when maximum.So the surface that deposition is given base becomes the speed of transparent glass fast than its inner transformation, causes bubble to stay transparent glass inside.

Further research is learnt, when adopting the gradient sintering method, when the sintering diameter gave base greater than 80 millimeters deposition, radial shrinkage caused so soon that to give base cracked, before radial shrinkage about 20%, almost all forms, and so far no longer continues cracked.Reach a conclusion thus: before giving base radial shrinkage about 20%, the whole base that gives is controlled in the sintering atmosphere at least, makes its contraction, and do not adopt gradient sintering method sintering it.

The deposition that adopts in the inventive method is given base can be with traditional method as productions such as " VAD " method and " OVPD " methods.

The method according to this invention, it is to contain dewatering agent (for example, chlorine-containing compound such as Cl that deposition is given base ₂, SOCl ₂And CCl ₄With fluorochemicals such as F ₂SF ₆And CF ₄) atmosphere (as helium, argon gas, nitrogen or oxygen) in the dehydration.

It is better that deposition is given base dehydrating effect when not being higher than 1400 ℃, is preferably in 1100-1400 ℃.If dehydration temperaturre surpasses 1400 ℃, then deposition is given base and is shunk rapidly, causes it cracked.

After the dehydration, give base and be admitted to gradually in the sintering atmosphere of a kind of rare gas element (as helium, argon, nitrogen etc.), preferably at 1500 ℃ to 1900 ℃ sintering.If give base at the sintering temperature more than 1900 ℃, that petty stretching is just very difficult.

Method of the present invention is specially adapted to major diameter and gives base as the deposition more than 80 millimeters.

Utilizing hereinafter, embodiment will be explained the present invention in further detail.Otherwise indicated, used % is weight %.

Example 1

Produce 6 kinds of porous depositions with the VAD method and give base, wherein each all comprises one by 94%SiO ₂And 6%GeO ₂Glass core and a cover of making by pure silicon dioxide of forming.It is 90 millimeters and length is 600 millimeters that deposition is given the base external diameter.Core diameter and cladding diameter are than adjusting to core/jacket that the optical fiber that makes manufacturing has directly than being 10/125(micron/micron).

Each deposition give base after dewatering under the listed condition of table 2 sintering and obtain a kind of transparent glass and give base.

The glass that processing is produced like this gives base, and the employing ordinary method draws optical fiber and checks the characteristic of fiber.

No. 1 to No. 3 is comparative sample in giving base, and dehydration and sintering are that the speed of sending into of employing 2 mm/min is given base and sent into gradually.In the stove of Fig. 4, label 1,2,3,4,5,6 and 7 represents to deposit the entrance and exit that gives base, support stick, muffle tube, well heater, body of heater, sends into gas respectively.

The transparent glass of producing gives base radial shrinkage 50% and contains bubble.Particularly, give base splits with passing through volution for No. 2.Record the refringence (△ n) of giving the two ends of base for No. 1 to No. 3 and all be about 50%.

With the optical fiber optical transmission attenuation that gives No. 1 to No. 3 drawing of base is 0.7-1.5 decibel/km, and the residual quantity of water is 0.4-0.5ppm.Because bubble increases the transmission decay of light significantly.Can not draw any optical fiber No. 2 with giving base.

To give base and be inserted into one by one for No. 4 to No. 6 in uppermost first stove of Fig. 5, the length of this stove is enough to hold the whole length of giving base.Then, with the mobile helium that has given constant current speed, chlorine and oxygen dehydration, and furnace temperature is brought up to 1350 ℃ with 3.3 ℃/minute speed from 800 ℃, and insulation 1 hour under this temperature.Stop supplies chlorine and oxygen drop to the base that gives that took off water gradually and are positioned at second stove that first stove bottom has helium atmosphere then.Label 1 to 6 is the same with Fig. 4 in Fig. 5, and label 7 and 8 represents that respectively sintering gives second stove of base and the well heater of second stove.

The base that gives of Sheng Chaning is for No. 4 to No. 6 that the transparent glass that does not contain bubble gives base like this.Its radial shrinkage be 35% and its longitudinally refringence be stable, as shown in table 2.

Give base from all of No. 4 to No. 6 and can both be drawn into optical fiber, each light transmission (wavelength is 1.30 microns) of giving base decays to 0.35-0.5 decibel/km, and quantity of residual is less than 0.1ppm.

Same deposition give base with give No. 4 identical conditions of base under dewater, but 1000 ℃ of down heating.Giving the base radial shrinkage is about 5%.When taking off giving base (No. 7) and will splitting to volution of water at 1675 ℃ of following sintering.

Example 2

Adopt the OVPD method, by 85%SiO ₂And 15%GeO ₂It is 6 millimeters that the glass granules of forming is deposited on diameter, and length is around 50 centimetres the axle of aluminum oxide, to be 50 millimeters up to diameter, till the pure silica glass particle deposition of the usefulness that continues is 100 millimeters to diameter.Afterwards, the axle of taking-up aluminum oxide has just produced a hollow cylinder deposition and has given base (No. 8).

Give base and be inserted into for No. 8 in uppermost first stove of Fig. 5, and dewater with mobile helium and chlorine, its flow velocity is respectively 10 liters/minute and 50 ml/min.And furnace temperature is raised to 1150 ℃ with 3.3 ℃/minute speed from 800 ℃.Insulation is 2 hours under this temperature.By dehydration, this deposition is given base radial shrinkage 30%.The deposition of having dewatered is given in base sends into Fig. 4 with the speed of about 5 mm/min the stove of insulation in 1650 ℃ of pure helium-atmospheres, and obtains a kind ofly do not have the transparent glass of bubble to give base.Giving optical fiber that base draws with this glass is 0.4 decibel/km to the optical transmission attenuation of 1.30 micron wave lengths, and quantity of residual is 0.1ppm.The specific refractory power reference is 1%.It is uniform that this situation means along the distribution of whole staple length specific refractory power.

In order to contrast, will with give No. 7, base identical give base (No. 9) with give No. 7 identical conditions of base under, dewater with the stove of Fig. 5.Afterwards, in same stove, in pure helium-atmosphere, be heated to 1650 ℃, obtain transparent glass and give base, contain numerous air-bubble in the centre of this base.After the dehydration, give base radial shrinkage 30%.

With a kind of deposition give base (No. 10) with give No. 7 identical conditions of base under dewater, but heat up and the temperature of insulation is 1000 ℃ rather than 1150 ℃.It shrinks 5%.Such dehydration give base with give No. 7 identical conditions of base under heat, the surface cracks as a result.

Claims (5)

1, a kind ofly draws the production method that optical fiber gives base, be included in the oxyhydrogen flame flame hydrolysis frit to form glass granules, glass granules is deposited on the seed spare gives base to form a kind of deposition solid or hollow cylinder, whole deposition is given base be placed in the atmosphere that contains a kind of dewatering agent, shrink at least in 20% time and the temperature and make its dehydration making deposition give the base diameter.And the deposition that heating and sintering took off water to give base be employing sends into mode the pure inert atmosphere from this part one end.

2, according to the method for claim 1, dehydration temperaturre is not higher than 1400 ℃

3, according to the method for claim 2, dehydration temperaturre is from 1100 ℃ to 1400 ℃.

4, according to the method for claim 1, sintering temperature is from 1500 ℃ to 1900 ℃.

5, according to the method for claim 1, deposition is given the diameter of base greater than 80 millimeters.

Images