DE2919619A1 - METHOD OF MANUFACTURING FIBER OPTIC LIGHT WAVE GUIDES - Google Patents

Description

J. Ir ve nI ¹ I.

Process for the production of glass fiber optical waveguides

The invention relates to a method for producing a glass fiber optical waveguide with a radial one Profile of the refractive index, in particular for the production of its preform, in the case of which from a chemical Vapor phase reaction the glass material first on the flame surface of a base plate, which is around a is rotated perpendicular to its flame surface axis, is deposited parallel to this axis of rotation is, and then on the free end face of the deposition on the base plate generated and rotated with this rod-shaped preform.

Such a method is proposed in the earlier patent applications DE-OS 28 35 326 and P 29 13 726. The gradient profile of the preform and thus also that of the optical waveguide is used in the DE-OS application 28 35 326 produced in that the precipitation of the glass material by an arrangement of concentric Burner nozzles happens, the composition of the gases reacting there from nozzle to nozzle in a radial direction Direction is so different that a predetermined radial distribution of the refractive index is created, The glass material is precipitated by flame hydrolysis.

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When registering P 29 13 726, the cancellation takes place through a series of parallel arranged burner nozzles, the composition of the there reacting gases also from nozzle to nozzle in. "- more radial Direction is so different that a predetermined radial distribution of the refractive index arises. The crackdown of the glass material takes place through a chemical vapor phase reaction.

In both methods, the surface on which the glass material is deposited is in the axial direction moved away from the nozzles, and the preform produced becomes fiberglass in a further, separate operation moved out.

task

It is the object of the invention to provide a further method of the type mentioned at the beginning.

solution

The object is achieved according to one of Claims 1 to 3. Further developments result from the subclaims.

description

The invention will now be explained in more detail with reference to the drawings, for example.
Show it:

Fig.l a method with a flame hydrolysis burner,

Fig.2 shows a method with a flame hydrolysis burner according to Fig.l and another burner for Melting the deposited glass material,

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Pig.3 a process with a plasma torch and

4 shows a method in which the preform is produced by one of the methods according to FIGS and at the same time is pulled out to the fiberglass.

In the following description, the expression "precipitation from a chemical vapor phase reaction" to be understood in such a way that he inter alia the suppression by the flame hydrolysis and the suppression by a reaction in a plasma excited by high frequency.

The first method of making a preform of a Glass fiber optic cable uses flame hydrolysis. In Fig.l is a burner 10 with hydrogen and fed oxygen. The oxygen is enriched with steam through a container not shown which bubbled part of the gas flow through a selection of different liquids leaves to absorb their vapors and transport them to the burner. Typically these contain Liquids silicon tetrachloride to react in the flame to produce silicon dioxide, and Germanium tetrachloride, phosphorus oxychloride (POCl,) and Boron chloride (BCl,), which react in the flame, and

² ^ produce oxides that dop the silicon dioxide and thus influence its refractive index. Using another apparatus for enriching the carrier gas with vapors, one or more of the halides can be replaced by hydrides. The one flowing out of the burner

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Flame 11 is against a base plate 13 or a Rod directed, on whose or whose surface see the precipitation of the flame hydrolysis accumulates. the Base plate or rod 13 is rotated about its axis, and at the same time the torch is moved from side to side across the end face of the rod or the surface of the base plate is guided along a line passing through the axis. To this We ensure that the precipitate accumulates on the entire end face. It should be noted that if the precipitation rate were constant, and the transverse movement in a straight line and would occur at a steady rate, with the precipitation moving towards the center of the surface with a greater speed would build »This is undesirable, so at least one of these 3 parameters must be changed in order to be even To get precipitation. A key feature of the The present invention is to influence the flame hydrolysis synchronously with the transverse movement in order to change the reaction product in such a way that a gradient profile of the refractive index arises. This is achieved by that the relative proportions of the gas flows are changed by the various liquids which the Provide steam reagents to form the precipitate. Thus, in the part of the transverse movement from the center towards the periphery, the relative proportions of the starting materials become of the refractive index increasing agents, such as germanium and phosphorus pentoxide, more and more reduced. It has therefore been found useful that the cyclical changes in the flow rates necessary to uniformly cover the end face of the rod 13 to those cyclical changes

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overlay that are necessary to achieve the required gradient profile of the refractive index. Corresponding In a preferred embodiment of the preform, the gradient profile of the refractive index does not extend to the outer edge, but it becomes a surface area of substantially constant refractive index plotted, from where the refractive index slowly in an approximately parabolic shape up to the maximum Value in the middle increases.

The rod is slowly moved away from the burner 10 with it a speed which is adapted to the rate of precipitation on its end face, so that the distance between the burner and the surface on which the flame 11 impinges, is kept constant.

! 5 It would be preferable to have precipitation conditions like this to choose that the precipitate becomes glassy as soon as it is deposited, instead of the precipitate in a non-vitreous form takes place in the form of glass particles, which a subsequent melting to vitreous State makes it necessary. However, it has been found that this is not possible with this precipitation method, if you incorporate volatile dopants such as germanium dioxide, phosphorus pentoxide or boron oxide into the precipitate want. The volatility of these dopants is so great that this deposition process does not it is possible that a significant proportion of these dopants will remain in the precipitate. To one with this To produce dopant-doped preform, the precipitate is initially at a temperature at which it

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forms a dense particulate precipitate, collected and placed on top at a higher temperature, which is just high enough to make the precipitate glassy, sintered.

The subsequent transfer of the particulate precipitate can be done by the rod-shaped preform 13 and the deposit on its end face from the burner through a furnace not shown pulls through. It is of course not necessary that the transformation in the glassy state together with the crackdown. If desired, the glassy state can be converted into a complete one separate independent subsequent process step can be carried out. Alternatively, you can also a cyclical working process can be applied. the supply of vapors to the burner for a while is interrupted when a predetermined thickness of the particulate precipitate has been reached, and the flame can be adjusted so that its temperature is increased enough to make the precipitate glassy before continuing with the knockdown.

Another alternative method of converting a precipitate that cannot be made glassy directly into the glassy one Convicting state uses a kind of a knockdown along with a glazing. It will the precipitation in particulate form in a localized across the end face of the rod (or the one on it precipitated material) moving zone formed,

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and the material deposited thereby in particulate form becomes in a second localized zone melted glassy, which is also across the end face (or the material deposited on it) is moved. One possible arrangement for carrying out this method is shown in FIG. This is different differs from the arrangement according to Fig.l only in the fact that a second burner 20 is present, which is common is moved with the first burner 10 across the end surface on which is deposited. This Burner is only supplied with hydrogen and oxygen without any additional vapors, and is adjusted so that it generates a flame 21 which is hot enough to be the when the burner 10 to melt the precipitate formed with its flame 11. For this purpose the arrangement is such designed so that the flame 21 follows that of the flame 11 in its path. At the end of each lateral movement in one Direction, the relative position of the two burners is reversed, allowing the assembly to return to transverse movement in the opposite direction is ready.

In a further modification, not shown, the second burner surrounds the first in a concentric arrangement.

In the description so far, only flame hydrolysis has been cited for suppression. A An alternative method that can be used is the precipitation from a high frequency excited plasma jet. A feature of flaming hydrolysis is that because of the presence of

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Hydrogen and oxygen in the reaction, the resulting product to contamination by OH groups tends, which are responsible for absorption bands that extend into the region of the spectrum, for which the fiber is intended. In a method of precipitation from a plasma jet, it is possible to choose a reaction from which hydrogen and hydrogen-containing compounds are excluded are, so that no OH groups can arise

^ P could otherwise be built into the precipitation. Die-Pig «.3 shows an arrangement with a plasma torch excited by high frequency. This is different differs from the arrangement according to FIG. 1 only in that the flame hydrolysis burner is replaced by a plasma burner 30 is replaced. This burner has a concentric arrangement in which a high frequency (in the range of up to 27 MHz) excited oxygen plasma jet. from the inner channel flows, while the vaporous materials, which are supposed to form the precipitate, from the inner Channel surrounding annular outer channel in the Plasma jet flow into it. These materials are produced by the oxygen in the plasma or by the oxygen gas, that carries the vapors, converted into oxides. These vapors can be the same. Halides and oxide halides which are used in the arrangement according to Fig.l described above. In this example the resulting Reaction, however, a direct oxidation instead of one Hydrolysis. The plasma jet can deliver enough energy to work in the area directly opposite the torch to promote the glazing of material which is in the

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The area closer to the edge of the beam has been cast down in a non-vitreous form. A special one separate subsequent process step for the vitrification of deposited material, the one 5 or more volatile dopants such as germanium dioxide is therefore not necessary.

It should be noted that any of the arrangements described above can be operated in such a way that continuously an optical fiber can be manufactured. This is shown in Fig.4. However, there are also other processes for the production of the preform are suitable, in which a precipitation of the glass material in axial direction, based on the preform, takes place, for example, also those in the two initially mentioned earlier patent applications proposed method.

In the arrangement according to FIG. 4, a flame hydrolysis burner is used or a plasma torch 40 is moved across the end of a preform 43 so that on the free end face the preform running through the flame 41 new material is applied. The baseplate for knockdown, which is initially necessary for the production of the preform, is here already removed so that the preform is rotated on its own around its axis and removed from the plasma torch or flame hydrolysis torch 40 is withdrawn by means not shown which are set so that the withdrawal of the Preform takes place at a speed which is adapted to that at which the material is applied, so that between the burner 40 and the end face of the

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Vorforin 43 a constant distance is maintained. These means moving the preform away from the burner in the axial direction simultaneously guide the preform into a fiber drawing furnace 45 in which the other end is heated to a temperature at which it can be pulled out to Paser 46. The resulting fiber is wound onto a drum 47. Normally the fiber is passed through a coating bath (not shown) before being wound onto the drum is used to cover the freshly drawn fiber with a protective layer that protects its surface from a Protects against decomposition in the attacking atmosphere. It was found that even if the preform continuously rotates around its axis while it is being drawn to the fiber, it is not necessary to do the drawn To let the fiber rotate synchronously with the preform, because a continuous shear was accepted at the point of tension can be.

It is believed that the precipitation reactions described above are at least preferably homogeneous vapor phase reactions in which a soot is formed from mixed oxides. This · is on it precipitated in particle form and subsequently sintered, or it is precipitated, and the soot is simultaneously melted into the glassy state. Another alternative precipitation method can be can be used in which a heterogeneous surface reaction takes place, in which glass directly on the substrate surface grows up. It's typical of a heterogeneous

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Reaction that it can take place at a lower substrate temperature than the Temperature that is necessary for an equivalent homogeneous reaction to produce a glassy Precipitation forms. The suppression of a reaction in a plasma jet that is related with the Fig.3 was described, is considered to be a mainly homogeneous reaction if it is below normal operating conditions and flow rates, however, one can change the Apparatus such that the plasma torch, the substrate and the arrangement for transverse movement in one environment work under reduced pressure instead of promoting a heterogeneous reaction under atmospheric pressure, in which the precipitation takes place directly in glassy form. Such a reaction happens, for example, at operating at a pressure in the range of 1 to 50 Torr with an inductive or H-plasma of frequency of 27 MIIz and the power of several kilowatts.

The inductive plasma may also be replaced by a higher Frequentes microwave plasma, for example with 2, ¹ GHz JS, wherein the requests to the pressure and power remain substantially unchanged.

A heterogeneous surface reaction can be promoted by a thermally activated reaction at atmospheric pressure although relatively low precipitation rates are believed to operate at reduced pressure is not a necessary condition for a plasma-activated, heterogeneous surface reaction, provided that the flow rate, the concentration of the reagents and the ion and electron temperatures of the plasma discharge are chosen so that a low concentration of activated specific reagents prevails in the plasma.

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L e r s e i t e

Claims (14)

Patent attorney Dipl.-Phys. Leo Thul Short Street 8 7 Stuttgart 30 J.Irven-14 INTERNATIONAL STANDARD ELECTRIC CORPORATION, NEW YORK Claims r \ ■ "■■■;■" - -, ■■: i: ■■■ Process for the production of a preform of a glass fiber optical waveguide with a radial profile of the refractive index, in which the glass material is first deposited on the flat surface of a base plate, which is rotated about an axis perpendicular to its flat surface, parallel to this axis of rotation, from a chemical vapor phase reaction is, and then on the free end surface of the rod-shaped preform produced by the precipitation on the base plate and rotated with this, characterized in that the precipitation of the glass material takes place through a single burner nozzle (10, 30) and that during precipitation the burner nozzle and the base plate with the preform produced are moved relative to one another transversely to the axis thereof and the reaction is influenced in such a way that the preform produced receives a gradient profile of the refractive index (FIGS. 1, 2, 3). Kg / Sch .. """
05/11/1979 909847/0846 iT.Irven-14 2. A method for producing a glass fiber optical waveguide with a radial profile of the refractive index, in which the rod-shaped preform is produced by first placing the glass material on the flat surface of a base plate around an axis perpendicular to its flat surface from a chemical vapor phase reaction is rotated, is deposited parallel to this axis of rotation and then on the free end surface of the rod-shaped preform produced by the deposition on the base plate and rotated with this, characterized in that the deposition of the glass material takes place through a single burner nozzle (40) and that during deposition the burner nozzle is moved across the flat surface of the base plate or across the free end face of the rod-shaped preform (43) produced, and the reaction is influenced in such a way that the preform (43) produced receives a gradient profile of the refractive index and that at the other end d he produced rod-shaped preform (43), the base plate is removed and this end is heated and the glass fiber (46) is drawn from it, while further glass material is deposited on the free end surface of the rotated rod-shaped preform (FIG. 4). 3. Process for the production of a glass fiber optical waveguide with a radial profile of the refraction index, in which the rod-shaped preform is produced by the fact that from a chemical vapor phase reaction Glass material first on the flat surface of a base plate, which is perpendicular to its flat surface Surface standing axis is rotated, is deposited parallel to this axis of rotation and then on the free End face of the knockdown on the baseplate 909847/0846 iT.Irven-1 4 produced and rotated with this rod-shaped preform, characterized in that at the other end of the rod-shaped preform produced, the base plate is removed and this end is heated and the glass fiber is drawn therefrom, while further glass material is deposited on the free end surface of the rotated rod-shaped preform. 4. The method according to claim 1 or 3, characterized in that the burner nozzle (10, 30, 40) is moved across the flat surface of the rotating base plate during precipitation. 5. The method according to any one of claims 1 to 4, characterized in that during deposition, the rotating base plate (13) or the rotating rod-shaped preform (43) produced is moved in the direction of the axis of rotation away from the nozzle at a speed which corresponds to the deposition rate of the glass material is adapted. 6. The method according to any one of the preceding claims, characterized in that the precipitation takes place by a flame hydrolysis (Fig.1, 2). 7. The method according to any one of claims 1 to 5, characterized in that the chemical vapor phase reaction is a reaction in which hydrogen or hydrogen-containing compounds are excluded. . «09847 / 0.84: 6 8. A method according to any one of claims 1, 2, 4, 5 and 7, characterized ge k ennzeichnet that the precipitate is formed by a reaction in a plasma beam (Fig, 3) 9. The method according to any one of claims 1, 3, 4, 5, 6 and 7, characterized in that the glass material is first deposited in a non-glassy form and is then melted to glass. 10. The method according to claim 9, characterized in that the melting to the glass is carried out together with the deposition. 11. The method according to any one of claims 1, 2, 4, 5, 6, 9 and 10, characterized in that through the burner nozzle (10, 40) which is moved across the surface of the base plate or over the free end surface of the preform , the glass material is deposited in a non-vitreous form and there is a second burner nozzle (20) which is moved parallel to the first burner nozzle (10) and which melts the precipitate caused by the first burner nozzle (20) into glass (Fig. 3). 12. The method according to claim 8, characterized in that the reaction in the plasma jet is carried out under conditions which cause the precipitate to be formed by a heterogeneous reaction taking place on the surface. 13. The method according to claim 12, characterized in that the reaction in the plasma jet is carried out at a pressure in the range from 1 to 50 Torr. 809847/0846 J.Irven-14 14. The method according to any one of the preceding claims _r, characterized in that the deposited glass material consists of silicon dioxide doped with one or more oxides of germanium, phosphorus and boron. : 909847/084