DE3306603A1 - Method for producing waveguide conductors with fibres of a defined excess length - Google Patents

Abstract

The invention relates to a method for producing a waveguide conductor which consists of a contractable jacket and at least one optical fibre arranged, at least to a certain extent movably, therein, in which, during winding on, the optical fibre is situated in a preselected initial position relative to the jacket, and in which the waveguide conductor is cooled to room temperature. After reaching room temperature (T1), the waveguide conductor (7) is once again heated to a heating temperature (T2) far in excess of room temperature and tempered, as a result of which it is possible to avoid subsequent irreversible changes in length due to further temperature increases. <IMAGE>

Description

Process for the production of waveguide cores

with fibers of defined excess length The invention relates to a method for producing one from a contractible casing and at least one in this at least to a certain extent movably arranged waveguide fiber existing Waveguide core in which the waveguide fiber is relatively to the sheath in a preselected starting position, and in which the waveguide vein is cooled to room temperature.

Such a method is already known from DE-OS 31 11 963. It is used to manufacture waveguide cores, in which the waveguide fiber has an excess length relative to the sheath, so that the fiber in the sheath e.g. Has undulating course. In the process, the waveguide vein is first used wound at a certain temperature above room temperature, the Waveguide fiber as a result of additional braking to the smallest radius of curvature lays inside the clad, so that the waveguide fiber relative to the clad in a selected starting position. It thus initially becomes a waveguide vein produced in which the fiber has a certain undersize relative to the cladding, i. the fiber would run into the sheath when the wire ends were loosened.

By cooling down to a constant ambient temperature of the so Coiled wire is achieved that it is before further cooling to room temperature is in a defined physical state, so that the occurring thereafter thermal length contraction of the shell during cooling remains calculable. It is thus possible the relative length of the cladding to the waveguide fiber to be determined exactly. For example, the previously set lower length can be used as a result compensated or even overcompensated, so that waveguide cores arise, the fibers of which are excessively long.

It is known that, for example, the optical transmission properties Such waveguide cores depend very much on the excess length of the waveguide fiber or from the reversible stretch or contraction area determined by the ascender length depend on the fiber sheath. For example, if the excess length is too great, the fiber will be pressed against the inner wall of the shell even with a slight contraction of the shell, whereby the attenuation can possibly increase considerably. The same can also if the excess length is too small and the envelope is stretched at the same time.

The expansion or contraction area of the envelope, in which the almost constant optical conditions are present, is thus also determined by the set excess length. It is therefore necessary that an excess length has been set after production the wire is preserved as far as possible.

It has been shown that in waveguide veins where to Setting the excess length the reversible thermal contraction when the cooling down Shell is used at room temperature, this requirement practically does not meet leaves, especially not if on the waveguide cores after their manufacture relatively high temperatures, e.g. during further processing steps or as a result of exposure to intense sunlight when stored outdoors. Such veins show, depending on the corresponding temperature effect, one compared to the one previously set Excessive length changed and did not degrade again even when the temperature was lowered Excess length their waveguide fibers so that their optical Change transmission properties in an uncontrolled manner.

The object of the invention is to provide a method for producing a Specify waveguide core with a waveguide fiber arranged in a sheath, the excess length is adjusted so that it is relatively higher even after exposure Temperatures on the waveguide vein is maintained after its completion.

This object is achieved according to the invention in that the waveguide core after reaching room temperature again to a level significantly above room temperature lying heating temperature is heated and tempered.

Investigations on contractible waveguide sheaths have shown that the reversible process of thermal expansion and contraction is an irreversible one Contraction process is superimposed, hereinafter referred to as the shrinkage process shall be. This shrinking process is seen as one that occurs over time Understand irreversible change in volume or length, its timing by heat treatment at a relatively high temperature in the sense of aging can be accelerated.

The shrinking process can therefore occur when adjusting the ascenders of waveguide fibers in waveguide cores, e.g. after the Adjustment of a certain initial position of waveguide fiber and cladding, e.g. after setting a short length of the fiber relative to the sheath, the sheath as long is shrunk until the desired excess length has been achieved. The size of the The excess length produced depends, as will be explained in more detail below, on several parameters, such as the tempering time, the cooling rate the casing just applied to the fiber, the initial position between the fiber and cover, etc.

The inventive method has the advantage that after completion the shrinking process practically no large irreversible changes in length Shell as a result of renewed exposure to high temperatures and thus permanent or

uncontrolled changes of the set excess length occur more, as tests with a wide variety of cover materials have shown.

According to an advantageous development of the invention, there is the contractible Sheath made of plastic, while a heating temperature is chosen that is just below the softening temperature of the plastic. Plastics have the advantage that they have a relatively strong shrinkage behavior, so that relatively large lengths are adjustable. The choice of a heating temperature just below the softening temperature the plastic also has the effect that the shrinking process is as complete as possible expires, so that the excess length once set is no longer irreversible changes subject.

According to another advantageous embodiment of the invention is used for Adjustment of the initial position reduces the friction between the waveguide fiber and the cladding chosen so large that the waveguide fiber is wound without undersength. That means that the fiber runs practically in the center of the sheath, which makes its relative Position to the envelope is set. Such a defined starting position between Fibers and sheaths are required in order to be aware of the well-known shrinkage behavior of the sheath, that was measured beforehand, for example, to be able to set the desired excess length.

According to a further embodiment of the invention is used for adjustment the initial position selected the friction between waveguide fiber and cladding to be small, wherein the waveguide fiber as a result of its braking when winding the waveguide core on the smallest radius of curvature in the envelope. To set the starting position the waveguide fiber can also be stretched during winding. Both methods have the advantage that the range of variation to adjust the ascender length through previous generation of a descender can be extended considerably.

In another advantageous development of the invention, the Waveguide vein cooled to room temperature with only a low cooling rate.

It has been shown that the shrinking process is part of it already used during the extrusion of the shell. This extrusion shrinkage is The lower the cooling rate of the waveguide vein, the greater the is extruding. By slowly cooling the waveguide vein, achieved that only a relatively small shrinkage during the subsequent annealing the shell and thus only a slight change in length of the waveguide core occurs, which facilitates the further treatment of the waveguide vein after extrusion. In addition, by varying the cooling rate, you get another one Parameters for setting the total shrinkage.

According to a further embodiment of the invention, the room temperature cooled waveguide core in a boiler room preheated to the heating temperature introduced, whereby reproducible shrinkage results can be achieved.

The tempering time then set is preferably in the range of hours, which leads to the complete completion of all shrinking processes.

It has proven to be useful to connect the waveguide vein to a to wind padded drum, whereby it is achieved that the shrinking process on the drum can run off because the bottom of the drum shortens the waveguide vein gives way. The waveguide cores are expediently located between the individual layers elastic layers, e.g., foam layers, are provided so that the envelopes both The lower and upper layers on the drum will shrink in the same way can.

The method according to the invention is described below with reference to a drawing explained in more detail. Shown are: Fig. La a device shown schematically for Implementation of the method, FIG. 1b shows a layer of a wound on a drum Waveguide core and Fig. 1c several layers of a waveguide core on a drum.

In Fig. 1a is a device for the production of plastic-wrapped Waveguide fibers shown for the transmission of optical signals. This device has a supply reel 1 on which the waveguide fiber 2 to be coated is wound is. The waveguide fiber 2 is passed through an extruder 3, which of a with plastic granulate 4 filled container 5 is fed, and the waveguide fiber 2 is provided with a plastic sheath 6 in which the waveguide fiber 2 is at least in a certain way Can move circumference. Of course you can several waveguide fibers 2, e.g. ten, are also located in the plastic sleeve. Of the Plastic for producing the shell 6 is e.g. a partially crystalline thermoplastic, such as polypropylene, polyethylene, polyvinylidene fluoride, polyurethane, or a amorphous plastic such as PVC. The one made of waveguide fiber 2 and plastic sheath 6 existing waveguide veins 7, which may contain a gel inside e.g. to improve their optical properties, is then used in a cooling station 8, e.g. a water bath, and then on a storage drum 9 wound (reeled).

If, for example, the braking force on the Waveguide fiber 2 is chosen so high that the internal friction between waveguide fiber 2 and shell 6 overcome over the entire length between the extruder 3 and the drum 9 is, the waveguide fiber 2 is when the waveguide core 7 is wound up by means of the drum 9 on the inner wall of the shell 6, which is illustrated in Fig. 1b. In this way, the waveguide fiber 2 has a shorter length than the cladding 6, which, among other things, is also determined by the diameter 10 of the drum 9 and values up to can accept one percent. It is thus a certain starting position between Waveguide fiber 2 and cladding 6 set, which is indispensable for the generation a waveguide vein 7, relative to which the waveguide fiber 2 defines a and reproducible excess length.

Of course, such an initial position, in particular in the case of thin fibers, can also be caused by stretching the waveguide fiber 2.

Another starting position can also be created by that with predominant friction between waveguide fiber 2 and Sheath 6 the waveguide fiber 2 always comes to lie in the center of the sheath 6. In In this case, the waveguide fiber 2 has an excess length of zero, so it is exactly the same long as the shell. The range of variation for setting the excess length is in this one However, the case is limited in relation to the areas mentioned above, as none Descender is available.

With regard to a certain extrusion process in which as a result of the used or specially selected cooling conditions the expected overall shrinkage is known or has been specifically determined, the diameter 10 of the drum 9 or the elongation of the waveguide fiber 2 selected so that after the extrusion sets the required short length of the waveguide fiber 2 in relation to the sheath 6. The drum 9 is padded with a suitable foam (not shown), so that the waveguide core 7 remain on the drum 9 during the shrinking process can. The waveguide cores are expediently located between the individual layers 7 further elastic intermediate layers 11, e.g. foam layers, so that the Sheath 6 of the lower waveguide core 7 in the same way as the one above Shell can shrink.

After the drum 9 is full of several layers of the waveguide core 7 is wound, the wire is severed, with the waveguide fiber 2 and the sheath 6 were clamped together so that the waveguide fiber 2 when present The short length is not drawn into the interior of the sleeve 6. The clamp can be used with further Processing and, if necessary, winding around the waveguide core 7 is expedient be replaced by a pin from the face of the severed wire out between the Waveguide fiber 2 and the inner wall of the sheath 6 is pushed and thus the fiber 2 is blocked.

To heat the cooled to room temperature T1 after extrusion Waveguide core 7 or the tempering thereof, the entire drum 9 with the waveguide core 7 brought into a heatable room which is at a heating temperature T2, which is slightly below the softening temperature of the plastic shell material. There then follows a tempering of the waveguide vein 7, the duration of which is expedient is in the hour range. Typical values are between a half and up to six hours, the subsequent shrinkage with increasing tempering time one Towards saturation.

After the tempering process, the waveguide core 7 is back on the Cooled down to room temperature, e.g. by removing the drum 9 from the boiler room will. The irreversible shortening of the sheath 6 then takes place, the previously set short length compensates or overcompensates, so that there is an over length the waveguide fiber 2 adjusts. By tempering near the softening temperature of the respective plastic is achieved in the event of subsequent temperature loads, e.g. when applying a jacket construction, no further irreversible change in length the plastic sheath 6 can be made more so that the desired e.g. for a cable The value of the excess length can hereby be set in a reproducible manner. Large ascenders are required for stretchable cable cores in aerial cables, for example. The heating temperature However, it can also be lower than that just below the softening temperature of the plastic. In this case, however, it must be ensured that the waveguide vein is later not heated up again above this temperature will. In any case, the heating temperature must be so high that the tempering an irreversible shrinking process of the shell 6 is initiated.

Of course, it is also possible to produce several in this way To strand waveguide cores 7 and to provide them with a common cable sheathing.

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Claims (13)

Claims: 1. A method for producing one from an ontraction-capable Sheath and at least one movably arranged in this at least to a certain extent Waveguide fiber existing waveguide core, in which during winding the waveguide fiber lies in a preselected starting position relative to the cladding, and in which the waveguide core is cooled to room temperature, characterized in that that the waveguide vein (7) after reaching room temperature (T1) again on a Heating temperature (T2), which is significantly above room temperature, is heated and tempered will. 2. The method according to claim 1, characterized in that the contractible Sheath (6) is made of plastic and the heating temperature (T2) is just below the Softening temperature of the plastic is. 3. The method according to claim 1 or 2, characterized in that for Adjustment of the initial position, the friction between the waveguide fiber (2) and the sheath (6) is chosen to be so large that the waveguide fiber is wound without a short length will. 4. The method according to claim 1 or 2, characterized in that for Adjustment of the initial position, the friction between the waveguide fiber (2) and the sheath (6) is selected to be small, and that the waveguide fiber as a result of its braking when winding the waveguide core to the smallest radius of curvature in the envelope lays. 5. The method according to claim 1 or 2, characterized in that for Adjustment of the initial position of the waveguide fiber (2) during winding is stretched. 6. The method according to one or more of claims 1 to 5, characterized characterized in that the waveguide core (7) with only a low cooling rate is cooled to room temperature (T1). 7. The method according to one or more of claims 1 to 6, characterized characterized in that the waveguide core (7) cooled to room temperature (T1) is introduced into a boiler room preheated to the heating temperature (T2). 8. The method according to claim 7, characterized in that the tempering time is in the hour range. 9. The method according to one or more of claims 1 to 8, characterized characterized in that the waveguide core (7) is wound onto a padded drum (9) will. 10. The method according to claim 9, characterized in that between the individual layers of the waveguide cores (7) elastic layers (11), e.g. foam layers, are provided. 11. The method according to claim 2 or one of the following, characterized in that that partially crystalline or amorphous plastics are used as plastics. 12. The method according to one or more of claims 1 to 11, characterized ie that between the waveguide fiber (2) and the sheath (6) is a gel is provided. 13. The method according to one or more of claims 3 to 12, characterized characterized in that for fixing the starting position between the waveguide fiber (2) and the sheath (6) a pin is inserted in the axial direction.