Patent Application
20100278494
This application claims the benefit of German Application No. 202009006357.7 filed on Apr. 30, 2009, the entire contents of which are herein incorporated by reference.
In one embodiment, an optical cable comprises optical transmission elements which are intended for the transmission of light over relatively great distances. Each of the optical transmission elements may contain a number of optical waveguides, which are surrounded by a buffer tube. A number of these optical transmission elements may be arranged in a stranded manner in the cable core of the optical cable.
The stranded arrangement of the optical transmission elements gives the optical cable great flexibility. In the case of SZ stranding, the optical transmission elements are stranded in the longitudinal direction of the cable core initially with a number of revolutions in one direction of rotation and subsequently stranded in the longitudinal direction of the cable with a number of revolutions in the opposite direction. Consequently, the optical transmission elements are arranged alternately in an S stranded form and a Z stranded form on adjacent portions of the cable core. To fix the stranding, the optical transmission elements are held together by a holding helix.
As a result of the stranding, the optical transmission elements have an excess length with respect to the length of the cable. The excess length is used to splice the optical waveguides of the optical transmission elements with further optical waveguides, in particular at a reversal position, at which the stranding direction changes from the S stranded form to the Z stranded form. For this purpose, the holding helix is removed at a reversal position.
It is often necessary to provide an already laid optical cable with branching nodes, at which the optical waveguides of the optical cable branch in different directions. For protection, the cable core of an optical cable may be surrounded by an outer cable jacket, with the result that the reversal points cannot be directly located by viewing the cable from the outside. If branching of the optical transmission elements by splicing optical waveguides of the optical cable with further optical waveguides is retroactively performed in the case of an optical cable with a cable jacket, the cable jacket must be removed at a reversal position of the stranding direction of the optical transmission elements. If, for example, the optical cable has reversal positions at intervals of 50 cm, in the worst case the cable jacket has to be removed over the entire 50 cm portion of the cable in order to find the reversal position.
In a region around the reversal position, the holding helix that holds the optical transmission elements together is removed. On account of the excess length, the optical waveguides contained in the buffer tubes of the optical transmission elements can be easily placed into a splicing device and spliced with further optical waveguides.
It is desirable to specify an optical cable in which a reversal position at which the stranding direction changes can be easily established. Furthermore, it is desirable to specify an arrangement for producing an optical cable in which a reversal position at which the stranding direction of the optical transmission elements changes can be easily established.
An embodiment of an optical cable comprises a number of stranded optical transmission elements which contain at least one optical waveguide. The optical transmission elements are arranged in a stranded manner such that the optical transmission elements are stranded in a first direction of rotation on a first portion of the cable and are stranded in a second direction of rotation, which is different from the first direction of rotation, on a second portion of the cable, arranged adjacent to the first portion. The cable also has a sheath, surrounding the optical transmission elements, with a marking arranged on a surface of the sheath to identify a position between the first portion and the second portion of the cable. The marking is designed in such a way that the marking is distinguishable from a region of the sheath surrounding the marking.
According to a further embodiment, the sheath surrounds the optical transmission elements in such a way that the marking on the surface of the sheath is arranged between the first portion and the second portion of the cable. According to a further embodiment, the optical transmission elements are arranged in a stranded manner such that a change between the first direction of rotation and the second direction of rotation takes place at a position between the first portion and the second portion of the cable. To identify the position on the surface of the sheath, the marking is arranged at the position of the sheath at which the sheath surrounds the position.
According to a further embodiment, the marking is designed in such a way that the position identified by the marking on the surface of the sheath is detectable. According to a further embodiment, the material of the marking is distinguishable from a material of a region of the sheath surrounding the marking.
The marking may be arranged on a side of the surface of the sheath that is facing the optical transmission elements. The marking may be arranged circumferentially around the optical transmission elements on the side of the surface of the sheath that is facing the optical transmission elements. According to a further embodiment of the optical cable, the marking may be formed as a component which is arranged on the surface of the sheath by an adhesive connection. The marking may be formed as a metal strip. The marking may, for example, contain aluminium or a magnetic material. According to a further embodiment, the marking may be formed as a transponder.
The sheath may contain a dielectric material or a material composed of polyester or a material composed of paper. The sheath may, for example, contain a material which brings about an increase in volume of the sheath on contact with water. According to a further embodiment of the optical cable, the sheath may be surrounded by a filament or yarn. Furthermore, the sheath may be surrounded by a cable jacket. The marking is designed in such a way that the position identified by the marking is detectable through the cable jacket.
According to a further embodiment of the optical cable, the optical transmission elements may be surrounded by a holding element. The optical transmission elements may be arranged in a stranded manner around a central element. The optical transmission elements may, for example, be arranged in an SZ stranding pattern. According to a further embodiment of the optical cable, an armouring of a metallic material is arranged between the sheath and the cable jacket. It is also possible, for example, for yarns of aramid or glass to be arranged between the sheath and the cable jacket.
An arrangement for producing an optical cable according to one of the embodiments given above is specified below. The arrangement comprises a stranding device for stranding the optical transmission elements of the optical cable. The stranding device is formed in such a way that the optical transmission elements are arranged such that they are stranded in a first direction of rotation on a first portion of the optical cable and are stranded in a second direction of rotation, which is different from the first direction of rotation, on a second portion of the optical cable, which is arranged adjacent to the first portion. A switching over of the stranding device between the first direction of rotation and the second direction of rotation is controlled by a control signal. The arrangement has, furthermore, an identification device for applying a marking to a strip to identify a position between the first portion and the second portion of the cable. The application of the marking is controlled by the control signal. Furthermore, the arrangement comprises a sheath forming device for forming the strip into a sheath around the optical transmission elements of the optical cable in such a way that the marking is arranged between the first portion and the second portion of the cable.
According to a further embodiment of the arrangement, the stranding device and the identification device are respectively arranged at a distance from the sheath forming device, so that the marking is arranged between the first portion and the second portion of the optical cable after the sheath has been formed around the cable core. Furthermore, a transporting speed with which the optical transmission elements are fed to the sheath forming device from the stranding device, and a transporting speed with which the strip is fed to the sheath forming device from the identification device are chosen in such a way that the marking on the surface of the sheath is arranged between the first portion and the second portion of the cable. In the case of a further embodiment of the arrangement, the optical transmission elements are stranded by the stranding device in such a way that a change between the first direction of rotation and the second direction of rotation takes place at a position between the first portion and the second portion of the cable. The marking is arranged by the identification device on the surface of the strip at a position at which the strip formed into a sheath surrounds the position. For example, the marking is arranged on the strip at an interval which corresponds to the length of one of the first and second portions of the cable. The marking may, for example, be adhesively attached on the strip when the identification device is activated by the control signal. A material which contains a metal may be arranged on the strip by the identification device. Furthermore, a transponder may be arranged on the strip by the identification device.
The sheath forming device may be formed in such a way that, after the sheath has been formed around the optical transmission elements, the marking is arranged on a surface of the sheath that is facing the optical transmission elements. Furthermore, the arrangement comprises an extruding device for surrounding the sheath with a cable jacket. According to a further embodiment, the arrangement may comprise a detecting unit for detecting the marking, an armouring winding device for arranging the armouring over the sheath and a printing device for applying an identification to the cable jacket of the optical cable. The detecting unit is arranged between the sheath forming device and the armouring winding device and the armouring winding device is arranged between the detecting unit and the printing unit. The printing unit arranges the identification on the cable jacket when the detecting unit detects the marking.
A method for producing an optical cable is specified below. According to the method, a number of optical transmission elements which contain at least one optical waveguide are provided. The optical transmission elements are stranded along a first portion of the optical cable in a first direction of rotation and are stranded along a second portion of the optical cable, arranged adjacent to the first portion, in a second direction of rotation, which is different from the first direction of rotation, wherein switching over between the stranding in the first direction of rotation and the second direction of rotation takes place by activating a stranding device with a control signal. A marking is applied to the surface of the strip by activating an identification device for arranging the marking with the control signal. The marking is designed in such a way that the marking is distinguishable from a region of the strip surrounding the marking. The strip is formed into a sheath. The optical transmission elements are surrounded by the sheath in such a way that the marking is arranged between the first portion and the second portion of the optical cable.
According to a further embodiment, the marking is arranged on the strip when the stranding device is activated with the control signal. The marking may, for example, be arranged on the strip by adhesively attaching a material that is different from the material of the strip onto the strip. For example, a material which contains a metal may be arranged on the strip. For example, a transponder may be arranged as the marking on the strip.
According to a further embodiment of the production method, the optical transmission elements are surrounded by the sheath in such a way that the marking is arranged on a surface of the sheath that is facing the optical transmission elements.
According to a further embodiment of the production method, the sheath is surrounded by a cable jacket. In the case of a further embodiment of the production method, it is provided that first the detection of the marking is carried out, then the surrounding of the sheath with an armouring and subsequently the application of a marking to the cable jacket, when the marking has been detected.
Embodiments of an optical cable and an arrangement for producing the optical cable are explained on the basis of the following figures. Furthermore, a method for producing such an optical cable is specified on the basis of the figures, in which:
The optical transmission elements 10 are provided for stranding by being arranged on storage devices 1100. In the case of the arrangement shown in
The stranding device 1000 may, for example, comprise an annular disc 1200. By means of a hole in the interior of the annular disc, the outer ring of the disc may be arranged around the reinforcing element 20. The reinforcing element 20 is led through the hollow of the annular disc. The outer ring 1200 of the disc contains openings for guiding the optical transmission elements 10. Each of the optical transmission elements is led through one of the openings.
During rotation of the stranding device 1000, the optical transmission elements 10 are arranged in a stranded manner around the reinforcing element 20 when the reinforcing element is moved through the annular disc in the direction of the arrow. To control the rotation of the annular disc, the stranding device is activated by a control signal S. In dependence on the control signal S, the direction of rotation of the disc 1200 changes. With the stranding device shown in
To create the SZ stranding pattern, the stranding device rotates for a number of revolutions, for example for three revolutions, in one direction, until the direction of rotation is changed by activation of the stranding device with the control signal S. After activation of the stranding device 1000 with the control signal S, the annular disc 1200 of the stranding device rotates for several revolutions in the opposite direction, until the direction of rotation is once again changed by activation of the stranding device with the control signal S. Consequently, reversal positions at which the stranding direction of the optical transmission elements on the cable core changes are produced at certain intervals, for example at intervals of between 0.4 and 0.6 m. In the case of the embodiment of the production line for producing the cable core that is shown in
To fix the stranding, the holding-helix winding device 4000 is provided. By means of the holding-helix winding device 4000, a holding helix 400, for example a filament or a yarn, is wound around the stranded optical transmission elements. In the case of the arrangement for producing the optical cable that is shown in
The cable core 100 may be further processed without any filler or be surrounded by a filling composition 100 in the production arrangement. The filling composition serves for protecting the optical transmission elements 10 from mechanical damage and can additionally prevent the ingress of water into the cable core. In order for the optical transmission elements 10 to be surrounded by the filling composition 500, a filling device 5000 is provided downstream of the holding-helix winding device 4000. The optical transmission elements are surrounded by the filling composition 500 by the filling device 5000. Polyolefin-based greases may be used, for example, as the filling composition.
The cable core 100 is surrounded by a sheath 200. The sheath 200 is first provided on a storage device 2100 in the form of a narrow strip. The storage device 2100 may be a drum, on which the sheath 200 is wound up to form an elongated strip. The sheath 200 may, for example, contain a dielectric material. It may, for example, also comprise a material composed of a plastic, for example of polyester, or composed of paper. The sheath 200 may be provided as a thin film of plastic with a smooth surface or as a nonwoven with a porous surface on the storage drum 2100.
In a sheath forming device 2000, the strip is formed into a sheath and arranged circumferentially around the cable core 100. The strip 200 may, for example, have a width which corresponds to the circumference of the cable core. The strip may also be slightly wider than the circumference of the cable core, for example wider by 2 mm to 4 mm than the circumference of the cable core. If the strip is wider than the circumference of the cable core, after it has been formed into a sheath the strip surrounds the cable core completely, or the edges of the strip overlap by the width of the strip that goes beyond the circumference of the cable core. If the strip has a width which is greater than the circumference of the cable core, it is ensured that, in the event of shrinkage of the strip as a result of tensile loading or as a result of a temperature change, the cable core is nevertheless completely surrounded by the sheath 200.
After the nonwoven or the film has been formed into a sheath, the sheath serves for protecting the cable core from high temperatures, which occur for example during an extrusion operation when extruding a cable jacket. The strip 200 may be coated on one or both sides with a SAP (Super Absorbent Polymer) powder. If the SAP powder comes into contact with moisture, the material swells and consequently brings about an increase in volume of the sheath. As a result, the cable core is protected from the ingress of water.
Provided between the strip runout of the strip 200 from the drum 2100 and the sheath forming device 2000 is an identification device 3000. In the case of the embodiment shown in
The markings 300 are arranged on the strip 200 by the identification device 3000. The application of the markings takes place by activation of the identification device 3000 with the control signal S, which is also already used for switching over the direction of rotation of the stranding device. When the identification device 3000 is activated with the control signal S, one of the markings, for example one of the aluminium labels, which at first is still applied to the backing strip 320, is pulled off from the backing strip 320 and arranged on the strip 200. For the layer of adhesive 310 of the label 300 to be detached as far as possible without leaving any residue, the backing strip 320 may be coated with Teflon.
Since the same control signal S that also serves as a switching-over signal for changing the direction of rotation of the stranding device is used for controlling the points in time at which the labels are arranged on the strip 200, the application of a marking to the strip 200 takes place synchronously with the changing of the direction of rotation of the annular disc 1200 of the stranding device 1000. Consequently, the markings 300 are arranged on the strip at an interval VL which corresponds to the length of the portion of the cable on which the optical transmission elements are arranged such that they are stranded in one specific direction of rotation.
From the identification device, the strip 200 provided with the markings runs over a compensating element 2200 and a guiding wheel 2300 to the sheath forming device 2000. The compensating element 2200 has various rollers, over which the strip 200 is led. In the case of the arrangement show in
In the case of the embodiment of the cable shown in
In the sheath forming device 2000, the strip is formed into a sheath in such a way that the markings are arranged on a surface 201 on the inner side of the sheath that is facing the cable core 100 and the optical transmission elements 10. The markings are consequently not visible on the outwardly facing surface of the sheath. Since the markings are arranged on the surface 201 of the sheath 200 that is facing the optical transmission elements 10, the markings are protected from becoming detached from the material of the sheath 200 by subsequent method steps, such as for example the extrusion of a cable jacket around the sheath 200.
In order to ensure that the markings 300 are actually arranged over the reversal positions RP after the strip is formed into the sheath 200 around the cable core, the length between the identification device 3000 and the sheath forming device 200 may be adapted to the length between the stranding device 1000 and the sheath forming device 2000. According to a possible embodiment, the length of the distance which the strip 200 passes over between the identification device 3000 and the sheath forming device 2000 corresponds to the length of the distance which the cable core covers between the stranding device 1000 and the sheath forming device 2000. If the cable core 100 with the stranded optical transmission elements 10 and the strip 200 are moved at the same speed, the markings 300 are arranged over the reversal positions RP after the strip has been formed into a sheath and after the sheath has been applied over the cable core.
In the case of the embodiment of the production arrangement 1 shown in
Even if the length of the distance which the strip 200 covers from the identification device 3000 to the sheath forming device 2000 is longer than the distance which the cable core passes over between the stranding device 1000 and the sheath forming device 2000, the identification device 3000 may be controlled by the control signal S to apply the marking 300 to the strip 200. As a result, the marking 300 is arranged on the strip 200 synchronously with the switching over of the direction of rotation of the stranding device 1000. In order to ensure that the reversal position RP on the cable core and the marking 300 on the strip 200 arrive at the sheath forming device at the same time, the transporting speed of the strip 200 may be increased.
By setting the time delay with which the markings are arranged on the strip 200, the transporting speed with which the strip 200 and the cable core 100 are moved, or by matching the length of the distance between the stranding device and the sheath forming device on the one hand and the length of the distance between the identification device and the sheath forming device on the other hand, the markings can be arranged over the reversal positions RP on the strip 200 with an accuracy of +/−20 mm.
For fixing the strip 200 that has been formed into a sheath and surrounds the cable core, a holding-helix winding device 6000 is provided. By means of the holding-helix winding device 6000, a holding helix 600, for example a filament yarn, is wound around the sheath 200. The holding helix prevents the backing strip 200 that has been formed into a sheath from coming apart under restoring forces. After the holding helix 600 has been applied to fix the sheath 200, the cable core is wound up on a storage drum 6100.
If they take the form of thin metal platelets that are adhesively attached on the inner side 201 of the sheath 200, for example, the markings may be detected by a metal detector through the cable jacket. If the optical cable is already laid in the ground and/or in a non-metallic pipe, is consequently no longer required to remove the cable jacket over a relatively long portion, corresponding to the interval VL between two reversal positions, in order to find a reversal position. Since the markings are placed on the strip 200 synchronously with the switching over of the direction of rotation of the stranding device and, given suitable adaptation of the distances between the stranding device and the sheath forming device on the one hand and between the identification device and the sheath forming device on the other hand, are arranged on the sheath 200 over the reversal positions, each reversal position can be determined by detecting the marking arranged over it on the underside 201 of the sheath through the cable jacket by means of a reader. Consequently, the cable jacket can be removed specifically at the determined position for the splicing of the optical waveguides. A cable sleeve, which is fitted over the opened location after splicing to protect the interior of the cable, can therefore have small dimensions. Since the marking 300 surrounds the cable core over the entire circumference, the reversal position can be detected by the reader from all sides.
As an alternative to markings in the form of aluminium metal platelets, magnetic labels may also be used. The magnetic labels are coated on the underside with a layer of adhesive and are adhesively attached onto the strip 200 under control of the identification device 3000 or of the stranding device when the identification device is activated by the control signal S, which is also used for controlling the switching over of the direction of rotation of the stranding device. In the case of an optical cable in which the cable core is protected by a cable jacket, labels with magnetic properties can likewise be determined by a reader, for example a negative field detector, through the cable jacket.
A further possibility for identifying a reversal position of the stranding direction is to apply radio transponders, for example RFID transponders, to the strip by means of the identification device 3000. The position of the RFID transponders on the underside of the sheath 200 can likewise be detected through the cable jacket by a reader. Consequently, the reversal points at which the stranding direction of the optical transmission elements changes can be established by a reader through the cable jacket if markings in the form of aluminium labels, magnetic labels or RFID transponders are used.
In the case of the arrangement 2 for producing an optical cable that is shown in
In the case of an optical cable which comprises an armouring composed of metallic components, markings on the sheath 200 that likewise comprise a metallic material cannot be detected. Therefore, in the case of such a cable it is necessary to provide a marking, for example a coloured identification, on the cable jacket 700. To provide the cable jacket with an identification, the arrangement for producing an optical cable that is shown in
In the case of a possible embodiment, the detecting unit 9100 is coupled with the printing unit 9200. If the detecting unit 9100 detects the marking 300 on the sheath 200, the printing unit 9200 is activated by a control signal SD, which is generated by the detecting unit 9100. The printing unit 9200 is formed in such a way that, when the printing unit 9200 is activated with the control signal SD, a coloured identification is applied to the cable jacket 700 by the printing unit 9200.
The distance between the detecting unit 9100 and the printing unit 9200 may, for example, be an integral multiple of the interval between the reversal positions. This ensures that the cable jacket has an identification at every reversal position at which the direction of rotation with which the optical transmission elements are stranded changes. If the distance between the detecting unit 9100 and the printing unit 9200 deviates from a multiple of the interval between the reversal positions, the application of the identification to the cable jacket may take place with a time delay with respect to the activation of the printing unit by the control signal SD. In the case of the arrangement for producing an optical cable that is shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 202009006357.7 | Apr 2009 | DE | national |
