DE3304552A1 - METHOD FOR PRODUCING LIGHTWAVE GUIDES - Google Patents

Description

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A. Baumgärtner-R.Dorn 7-6

Process for the production of optical fibers

The invention relates to a method according to the preamble of claim 1.

Such methods in which the glass material to generating preform is deposited in particle form on a rotating carrier, are, for. B. from DE-AS 23 13 and from DE-AS 27 15 333 known.

All known methods of this type have the feature in common that the particulate glass material to be deposited is produced in one or more burners by a chemical oxidation reaction and is deposited directly from the reaction on the rotating carrier, with SiCl and GeCl, for example, being SiCl in the flame 0 _? or GeOp are oxidized. Chlorides or oxychlorides are generally used as starting materials for these processes. Due to their reactive character, these compounds must be stored in an absolutely water-free environment; quartz glass containers are usually used as storage and transport vessels. The vessels must be handled with great care.

ZT / P1-Kg / R

02/08/1982 -4-

A. Tree gardener 7-6

From DE-OS 30 00 762 is a method for application of a ManteL on a stick made of KerngLasmateria L known, the production of which is not described. In this process, the starting materials are not the chlorides, but the oxides have already been used, d. H. the deposition of the particulate material is not involved linked to an oxidation reaction. This is where glass powder is used fed by gravity across the flame of a plasma torch to this flame, carried away by the flame and deposited on the surface of the rotating rod made of core glass material heated by the flame, in such a way that a homogeneous glazed layer is created. Because the particles of glass powder in the flame melted into droplets and deposited on the support under direct glazing is a purification of the deposited glass, in particular an avoidance or subsequent removal of hydroxyl group inclusions hardly possible with this procedure.

For growing single crystals, DE-PS 24 15 the so-called Verneuil process known, in which powdery oxidic material is converted into a tubular Oxyhydrogen burner introduced coaxially, melted there and is deposited on a coaxially arranged carrier which rotates during the deposition and with the Growth rate of the deposited material in is removed from the oxyhydrogen burner in the axial direction.

A regulation of the dosage of the powder supply does not take place ^ and silicon dioxide as powdery oxidic Starting material is related to this process not known.

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A. Building contractors 7-6

It is the object of the invention to provide a method of the above designated genus for the production of fiber optic cables state that avoids the difficult to handle chlorides and oxychlorides and at the same time allows preforms to be manufactured with great purity.

The object is achieved as specified in claim 1. Further developments can be found in the subclaims.

The invention is illustrated by way of example with reference to the single drawing explained in more detail. The drawing shows an apparatus for carrying out the new method.

Starting material for the process described below is a powder of silicon dioxide or a powder mixture made of silicon dioxide and an oxide dopant, for example germanium dioxide. Such powdery Starting material can also be used in large quantities handle without expensive safety devices and store.

• The powder is in a storage container 1 and is from there via a metering device in the form of a Conveyor screw 2 with controllable worm gear 3 in initiated a heat generating device that the Powder liquefied or evaporated and then as particulate Glass material is deposited on a carrier. The heat generating device is in the present case a hydrogen-oxygen burner consisting of several coaxial tubes, which, as shown, consists of three coaxial

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Tubes 4, 5 and 6 consists. The PuLvermateria L is made by the screw conveyor 2 is introduced into the inner tube 4 of the burner, which is also the supply pipe for the Is oxygen. The oxygen supply makes it homogeneous Gas-powder mixture generated. The screw conveyor 2 determines the amount of per unit of time in the burner incoming powder. To regulate the per time unit A mass flow regulator 7 is provided for the amount of powder flowing in. The mass flow measurement can be carried out according to various principles, depending on the required measurement accuracy take place / for example optical transmission measurements, optical scatter measurements or a capacitive one Measurement of the mass flow possible, the latter because of the dielectric constant of the powder differs significantly from 1.

The hydrogen is introduced into the middle burner tube, and through the outer tube 6 can enter the burner flame a gas can be introduced in order to purify the powder evaporated in the flame and hydroxyl groups in the deposited Avoid material. For this purpose, gases are generally suitable which contain impurities in the form of transition metals and form compounds with hydroxyl groups which are volatile at the deposition temperature, for example chlorine gas is suitable. If necessary, a protective gas, e.g. B. argon can be added. To regulate the flow rates of hydrogen, Oxygen and chlorine are mass flow regulators 8, 9 and 10 provided.

The burner described opens into a combustion chamber 11, which has a gas-tight bushing on its upper side.

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has and a suction tube 12, so that exhaust gases and water vapor can be extracted. In the combustion chamber 11, more precisely in the flame burning in it, this is Powder material introduced into the burner evaporates or liquefied so that in the vapor phase or liquid phase cleaning and elimination of hydroxyl groups can take place. The vapor phase or liquid phase becomes after possibly a recondensation has taken place has, particulate I-shaped glass material deposited on a carrier i eden.

It may be procedurally more favorable that the Cleaning of the material and the elimination of hydroxyl groups by means of the chlorine gas is not already in the flame instead of adding chlorine and the deposited particulate material in one to be subjected to chlorine treatment in a later step. In this case the burner would only serve to Particle I-shaped glass material to be deposited on a carrier,

The carrier on which the light emerging from the flame and recondensed material is deposited, is located in the combustion chamber 11 in an orientation such that _s can be controlled, the distance between the burner head and the place of deposition on the carrier in a certain way. In the example shown, the deposition on the carrier is a process in which the preform grows in the axial direction in relation to the carrier axis. A glass rod 13 rotating about its longitudinal axis is used as the carrier, and the deposition takes place on the end face of the preform grown on it.

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The temperature prevailing in the combustion chamber and in particular the temperature of the deposition surface becomes determined by means of a pyrometer 14 and with an additional heater 15, for example a preform growing up surrounding resistance heater 15, or via the fuel gas supply regulated. The flame temperature is determined by means of a second pyrometer 16.

The deposition conditions prevailing in the combustion chamber, where the pressure can be regulated via the suction, can now be adjusted so that the preform 17 in porous State or in a glassy state. A porous preform that was later melted into a glassy preform must be, is preferable in the event that the above-mentioned cleaning in the vapor phase is not brings a sufficient result and a separate post-treatment for the purpose of cleaning or disposal of hydroxyl groups is necessary.

To a second material with a different composition to be deposited on the material by the axial growth of the burner described deposited material is a second Burner 18 provided. This second burner 18, of which only the burner head opening into the combustion chamber is shown is designed in accordance with the first burner shown and is supplied and controlled accordingly. The second burner 18 has a deposition direction which is perpendicular to the axis of rotation of the beam, and therefore enables the material deposited from the first burner to be coated on its outer surface.

With the material deposited in this way, two

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for example a material with a lower refractive index act as the jacket material from the preform fiber to be produced is required. The direction the arrangement of the beam with respect to the axis of the first / The burner shown is chosen so that both burners in terms of temperature and deposition conditions the appropriate orientation to the deposition surfaces to have.

Should the core composition have a radial gradient of the refractive index, so is in place of the one shown first burner as known per se to use a multi-tube burner, due to the arrangement of its Burner nozzles or different based on the local temperature profile and by feeding them with powders Composition produces the desired refractive index curve.

An alternative to this is a burner that consists of a homogeneous Powder mixture solely by suitable arrangement of its Nozzles generate the desired refractive index course.

Another possibility is to use several independent, suitably arranged burners.

It should be noted that the above-described

Invention can also be used that one after the other

several layers are applied to the outer surface of a rotating support.

As a heat generating device for melting the powdery Starting material can be used instead of a gas

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A. Tree gardener 7-6

torch of the type described also a plasma torch with inductive or capacitive plasma coupling or a Arc torch can be used. It also appears possible to obtain the necessary energy in the form of laser pulses provide.

The powdery starting material, namely silicon dioxide powder and, for example, germanium dioxide powder is available from several manufacturers in different quality levels. The powder appears as grain a grain size of a few hundredths of a jjm is suitable.

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Claims (10)

STANDARD ELECTRICS LORENZ
STOCK COMPANY
STUTTGART A. Baumgärtner-R.Dorn 7-6 Claims η.] Method for the production of Lichtwel lenleitern, at in which a preform is first made and the optical waveguide is drawn from it, in the case of the preform production particulate glass material on a rotating Carrier is deposited, thereby marked e i c h η e t that powdered silicon dioxide or this together with one or more powdered ones Dopants by means of a gas flow over a regulated Dosing device coaxially in a ring or tubular heat generating device initiated in this liquefies "or evaporates and after condensation is deposited on the rotating support. 2. The method according to claim 1, characterized in that that the core and shell of the preform are applied to the carrier simultaneously or one after the other. 3. The method according to claim 1 or 2, characterized in that the particulate glass material such is deposited on the rotating carrier that a porous body is formed and that the porous body is then melted into a glassy preform. ZT / P1-Kg / R -Z- 02/08/1983 A. Tree gardener 7-6 4. The method according to claim 1 or 2, characterized in that the particulate glass material below Immediate glazing is deposited on the rotating support. 5. The method according to any one of the preceding claims, characterized in that at least one gas is introduced into the heat generating device, which with Transition metals and compounds with hydroxyl groups which are volatile at the deposition temperature. 6. The method according to any one of the preceding claims, characterized in that an inert gas in addition the heat generating device is initiated. 7. The method according to any one of the preceding claims, characterized in that as a heat generating device a gas burner is used. 8. The method according to any one of claims 1 to 6, characterized characterized in that a heat generating device Plasma torch is used. 9. The method according to any one of claims 1 to 6, characterized in that a heat-generating device an arc generating device is used. 10. The method according to any one of claims 1 to 6, characterized in that a heat-generating device Device is used that generates laser pulses.