DE2630365A1 - Multichannel waveguide made using double crucible - where several glass optical fibres are drawn and embedded in glass sheath - Google Patents

Abstract

A multichannel optical waveguide is made, where several fibres are embedded in a single sheath. An outer crucible (1) surrounds an inner crucible (2) which contains outlet nozzles in its base matching the number of optical fibres required; the fibres flow downwards from crucible (2) through at least one nozzle in the base of crucible (1), so the material flowing from crucible (1) forms a sheath round the fibres; and the assembly is drawn out of the double crucible (1,2). Two types (1,2) of glass are pref. melted simultaneously in the crucibles while the nozzles are closed by a single plug; the melts are then cooled to the drawing temp., and the plug is removed for drawing the multichannel waveguide. The pref. appts. includes a double crucible made of Pt; Ir; or Pt-Rh, surrounded by a heater coil. Arrangement avoids the prodn. difficulties involved with conventional methods; and waveguides of high quality suitable for optical communication over long distances are obtd.

Description

Device and method for the production of multi-channel

Optical fibers.

The invention relates to a method and a device for production of multi-channel optical fibers.

Multi-channel optical fibers are known, e.g. from the document N.S. Kapany, Fieber Optics ", Academic Press, (1967), New York / London.

With multi-channel optical fibers, several optical fiber cores are in embedded in a common mantle. The fiber optic cores consist of a material whose refractive index is higher than the refractive index of the material of the coat. So that the optical fiber cores do not influence each other optically, they must have a sufficiently large distance from one another. The distance should a multiple of the wavelength of the light guided in the fiber optic cores be. Optically, such a multichannel optical fiber corresponds to one Bundles of individual fibers, each with an optical fiber core having its own owns separate coat.

A manufacturing method is also from the publication mentioned at the beginning known for multi-channel optical fibers.

The production takes place according to the rod-and-ear method. This is a Bundles of rod-and-tube units inserted into a glass tube of sufficiently large diameter, Heated to the softening temperature of the glass and turned into a multi-channel optical fiber moved out. The glass rods, which have a higher refractive index than the glass tubes, form the fiber optic cores in the fully drawn multichannel fiber optic.

According to the rod-and-tube method, only optical fibers can be used in proportion produce low quality. In general, the quality is for image transmission Sufficient over short distances for optical message transmission over larger ones However, the quality is not sufficient for stretching. The main reason for the relative poor quality of the optical fibers produced by the rod-and-tube method in that it is very difficult to create a fault-free interface between the ¢ let rods, the the later fiber optic cores, and the glass tubes, which later form the fiber optic cladding Elden, to generate. This interface is almost always made up of dust particles or small ones Contaminated gas bubbles. In addition to these fundamental difficulties, the rod-tube method brings with it, the following problems arise: The bundled rod-tube units cannot be heated evenly in practice, i.e. when pulling the multichannel optical fiber inhomogeneous heating of the bundled rod-tube units occurs. aside from that it is difficult to melt the individual units together without bubbles guarantee.

The object of the invention is to provide a new manufacturing process and a device for carrying out the manufacturing process for multichannel optical fibers indicate that the difficulties mentioned above do not occur.

This object is achieved by a method which, according to the invention has the features of the characterizing part of the patent holder; -spruches 1.

The method according to the invention can advantageously be carried out in such a way that that multichannel optical fibers of any length can be made.

It is also advantageous that multi-channel optical fibers are produced where the cross section of the fiber optic cores and the cross section of the optical fiber cladding can have almost any shape, as further is described below on the basis of exemplary embodiments.

It is also advantageous that, due to the invention, the pulling of Multi-channel optical fibers at the same speed as known single fibers can be done.

According to the invention is therefore for the production of multichannel optical fibers a double crucible is provided, in which an inner crucible is arranged in an outer crucible is. The inner crucible is used to hold a glass or plastic compound that is used for the later fiber optic cores is provided. The outer pan is used for receiving another glass or plastic compound that will later be used for the optical fiber cladding is provided. The outer pan has at least one nozzle in its bottom, which has a relatively large cross-section.

The inner crucible has several nozzles with relatively few Cross-section, which are arranged above the nozzle in the outer crucible so that they differ from the cross-section the nozzle are enclosed in the outer pan.

This means that when the multi-channel optical fibers are pulled out of the inner pan Kunsitoff- or glass strands that form the later optical fiber cores, the automatically enveloped by the plastic or glass mass located in the outer pan so that the later optical fiber cladding is preformed.

The shape of the nozzle cuts corresponds to the shape desired Cross sections of the optical fiber cores or the optical fiber cladding.

In general the nozzles of the inner crucible will be circular, corresponding circular optical fiber cores. For special applications are However, other shapes are possible, as explained below on the basis of exemplary embodiments will.

In the following the invention will be explained with reference to the figures, the exemplary embodiments show explained.

1 shows a longitudinal section through a double crucible, Fig. 2 shows a view from below of this double crucible. Figures 3 to 6 show examples of different cross-sections of multi-channel optical fibers.

According to FIG. 1, the double crucible consists of an outer crucible 1, in which an inner crucible 3 is arranged by means of holders 2. In the bottom of the inner crucible are the nozzles 30, in the bottom of the outer pan the nozzle 10. These nozzles can at the same time by a cap 4, for example from a quartz glass rod 5 is worn, must be closed.

Fig. 2 now shows a plan view from below of the double crucible. Corresponding positions have the same reference numerals as in Fig. 1. The outer pan 1 is broken open image-wise in this figure, so that the inner pan 3 and one of the brackets 2 can be seen. The remaining part of the inner crucible and another holder 2 are shown in dashed lines. This representation is to it can be seen that the nozzles 30 in the inner crucible are within the cross section of the nozzle 10 are arranged in the outer pan.

For heating the double crucible, see again FIG. 1, is in this Example, an induction heater 6 is provided. If such a heater is used, at least the outer pan must be made of a metal. The inner crucible will then heated by convection.

The outer crucible is used to manufacture the multi-channel optical fibers filled with a material for the cladding of the multichannel optical fibers, in addition if the outer crucible is loaded, for example, with corresponding glass rods 11, these Glass rods are then melted in the outer crucible. In a corresponding way can the inner crucible is loaded with gas rods 12 for the material of the optical fiber cores will.

It can be seen that the glass material is also in a form other than rod Can be introduced into the crucible, for example, there are also corresponding glass spheres suitable. It is also possible to pour a glass melt into the crucible.

During the melting process, the cans in the crucibles are done a closure 4 closed. This prevents the glass material from becoming for the fiber optic cores and the glass material for the fiber optic cladding at Mix the melting process.

As soon as the glass load on the crucible has melted, and as soon as the glass melt in the crucibles by reloading with glass material a desired Has reached the level, the double crucible is cooled to the drawing temperature. As soon as this temperature is reached, the closure 4 is removed downwards, a strand of glass is attached to this closure, which is now attached to a pulling drum (not shown) can be pinned, so that the drawing process in known Way can be initiated.

The strand of glass drawn from the double crucible tapers in the process depending on the pulling speed to the finished multichannel optical fiber . As is well known, only the absolute value of the cross section is used when drawing a glass strand of the glass strand changed, the ratio of the cross-sections of individual parts of the Glass strand, i.e. here the ratio of those emerging from the cans of the inner crucible Glass strands to the cross section of the nozzle in the outer crucible remains unchanged.

With continuous feeding of glass material into the outer crucible or inner crucible, the level of the melt in the crucibles can be kept constant so that an endless multichannel optical fiber can be drawn out.

Before being wound onto the drawing drum, the multichannel optical fiber still be provided in a known manner with an additional plastic jacket, which protects the fiber from mechanical damage. For this purpose, the fiber can for example by a bath can be drawn with an epoxy resin.

The double crucible can also be made with transparent plastics instead of glass be loaded. This means that multi-channel optical fibers can be made from plastic 'The manufacture of these plastic optical fibers takes place in the same Way like making the fiberglass. So far, however, can be done with glasses achieve higher optical qualities.

FIG. 3 now shows an example of the cross section of a multichannel optical fiber shown how it can be produced by the method according to the invention. In this example, both the fiber optic cores 100 and the fiber optic cladding 101 has a circular cross section.

The diameter of the entire fiber is, for example, 145 µm Diameter of the fiber optic cores 3G / um.

To produce this multi-channel optical fiber shown, Thus, according to the invention, a double crucible is used, in which the outer crucible is a Has nozzle, the cross section of which has the shape of the cross section of the optical fiber jacket is equivalent to. The same applies to the nozzles of the inner crucible and the optical fiber cores.

4 is an example of a ribbon-shaped multichannel optical fiber darges + ellt. Here are the optical fiber cores 100, which in turn are circular Have cross-section arranged in a layered jacket, which has a flat has a rectangular cross-section.

It can be seen that the nozzle in the outer crucible to produce a such multichannel optical fiber has a cross section of the optical fiber cladding must have a corresponding rectangular cross-section. The nozzles of the inner pan for the fiber optic core must be within the cross section of the nozzle in the outer pan be arranged.

In Fig. 5 is the cross section of a multichannel optical fiber with 40 optical fiber cores shown, which are in the manner of an 8x5 matrix within the optical fiber cladding are arranged.

Fig. 6 shows an example of a multichannel optical fiber which Optical fiber cores 101 with non-circular cross-sections have +. These fiber optic cores have a cross-section similar to the shape of segments for digital displays. With such a multichannel optical fiber, the individual optical fiber cores controlled with light sources, so is already with a single multi-channel optical fiber digital image transmission possible.

The multichannel optical fibers shown can be easily converted Connect using multichannel optical fibers of the same type. For an adjustment when splicing or coupling it is sufficient to use one of the outer optical fiber cores Multi-channel optical fiber with an optical fiber core of the other multi-channel optical fiber to coincide. If at the same time the end faces of the optical fiber jackets are brought to congruence, the two multi-channel optical fibers are already optimally adjusted to each other. The adjustment of the fiber optic jackets to each other can for example be done by capillary that have a slightly larger diameter respectively.

Have cross-section than the multi-channel optical fibers to be connected.

In the double crucible shown in FIG. 1, the outer crucible has only one nozzle. However, it is also possible to equip the outer pan with several nozzles, the inner pan then also has a corresponding multiple of nozzles. Through this it is possible to simultaneously use several multichannel optical fibers in the above-described Way to draw. In this case, a drawing temperature with a stranding device can also be used are provided so that stranded multi-channel optical fibers are produced can be.

From the above description it can be seen that advantageously for the actual drawing process with multi-channel Optical fibers according to the invention no greater effort must be made than it is with simple Fibers is common.

The double crucible can for example be made of platinum, iridium or a Are made of platinum-rhodium alloy. These metals are because of their chemical Resilience and its heat resistance are particularly well suited. It can but also other materials are used that are heat-resistant and through the melts cannot be attacked chemically or physically.

For example, the following glasses from the company are used as glass material Schott suitable: F-7 for the fiber optic jackets, LF-5 for the fiber optic cores.

However, other types of glass can also be used, but must the glass for the fiber optic cores and the glass for the fiber optic cladding can be drawn at the same temperature. It is also important that the glass is sorts do not enter into any undesired chemical reactions with one another.

The cleaner the starting substance for the glasses, the less is the attenuation of the light guided in the later optical fibers.

4 claims 6 figures Blank page

Claims (4)

Claims 1. A method for producing a multichannel optical fiber with an optical fiber jacket in which several optical fiber cores are embedded, in that a double crucible is used which an outer pan (1) and an inner pan (3) arranged therein, wherein at least one nozzle (10) in the bottom of the outer crucible and at least one nozzle (10) in the bottom of the inner crucible a number of nozzles (30) corresponding to the number of optical fiber cores with the nozzles of the inner crucible above the nozzle of the outer crucible and inside of the cross section of the nozzle are arranged in the outer crucible that in the outer crucible a material for the optical fiber clad is filled into the inner crucible Material for the optical fiber cores, and then the multi-channel optical fiber from the double crucible is pulled. 2. The method according to claim 1, characterized in that g e k e n n z e i c h -n e t that a type of glass intended for the optical fiber jacket is melted in the outer crucible is that at the same time one provided for the optical fiber cores in the inner crucible Type of glass is melted that the nozzles in the crucible during this melting be kept closed by a closure (4) that after melting the double crucible to a temperature intended for drawing optical fibers is cooled, that now the closure (4) is removed, from the double crucible a strand of glass emerges, and that this strand of glass becomes a multichannel optical fiber is pulled out. 3. Apparatus for carrying out a method according to any one of the claims 1 and 2, given by a heater (6) that can be heated Double crucible with an outer crucible (1) and an inner crucible arranged therein (3), through a nozzle (10) arranged in the bottom of the outer pan and through one of the Number of optical fiber cores corresponding number of DUses (30) in the bottom of the inner crucible, wherein the nozzles of the inner pot are above the nozzle of the outer pot and within of Cross section of the nozzle are arranged in the outer pan. 4. Apparatus according to claim 3, characterized in that g e k e n n -z e i c h n e t that the double crucible made of platinum, iridium or a platinum-rhodium alloy consists.