DE102004035809A1 - Optical cable and method of making an optical cable - Google Patents

Abstract

An optical cable (1) comprises a cable sheath (11) and a plurality of optical transmission elements (101, 102) which are arranged within the cable sheath (11). Each of the transmission elements comprises a plurality of optical fibers (10101, 10102) and a wire sheath (1011) surrounding the optical fibers. The buffer tube (1011) contains a matrix material and a filler embedded in the matrix material. The melting point of the matrix material is more than 85 ° C. and the mass fraction of the filler at the core sheath is at least 30%.

Description

The The invention relates to an optical cable with optical transmission elements, the one vein cover with low elongation at break exhibit. The invention also relates to a process for the preparation of optical cable, a heating of optical transmission elements to temperatures of more than 85 ° C allows.

One Optical cable includes multiple optical transmission elements, too be referred to as veins or "units". The optical cable further comprises a cable core and a cable sheath, which surrounds the cable core. The multiple optical transmission elements are arranged inside the cable core. The cable sheath of the optical cable serves both the protection and the discharge of the optical transmission elements. A suitable material for the cable sheath has a high melting point. Well-known materials for one Cable sheath contain, for example, polyamide (PA), polyethylene (PE) or polyvinyl chloride (PVC).

One Optical cable can have a number of 12 optical transmission elements include. The optical transmission elements can characterized by a number of 12 distinguishable colors be. Based on the colors used to label the optical transmission elements are, can be exposed at both ends of a piece of cable Ends of the optical transmission elements uniquely assign each other.

One optical transmission element includes a number of optical fibers and a wire sheath, which surrounds the number of optical fibers. The vein cover of a optical transmission element allows a classification of optical fibers contained in an optical cable into distinguishable groups. Thus, the optical fibers easily and quickly can be exposed should the vein cover without be special tools to remove. A suitable material for the core case should therefore be soft. In particular, it should have a low tensile strength and elongation at break exhibit. Known materials for such a soft core sheath of optical transmission elements For example, be filled with chalk poly-vinyl chloride or high filled Ethyl vinyl acetate.

For example can be an optical transmission element comprise a number of 12 optical fibers. The optical fibers can characterized by a number of 12 distinguishable colors be. Based on the colors used to mark the optical fibers are those at the two ends of a section of a Loose Tube uncovered ends of the optical fibers uniquely assign each other.

One Optical waveguide comprises a fiber coating (Coating) and a Glass fiber surrounded by the fiber coating. Usually is the optical fiber through the color of the fiber coating characterized.

A Number of 144 optical fibers contained in an optical cable For example, it can be divided into a number of 12 groups of one each Number of 12 optical fibers to be divided. In particular, can a number of 12 optical transmission elements an optical cable and a number of 12 optical fibers in each case one of the opti's transmission elements characterized using the same 12 distinguishable colors be. For example, the wire hull of an optical transmission element through one of the 12 colors and the fiber coating of each fiber optic cable in the optical transmission element another one of the 12 colors will be marked. In this case leave The two ends of one of the 144 fiber optic cables in the optical cables are included, based on the color of the fiber coating the optical waveguide and the color of the buffer tube of the optical transmission element, to which the optical fiber belongs assign each other.

The optical transmission elements are arranged in the cable sheath such that in a portion of the optical cable having a certain length, sections of optical transmission elements run, which have a slightly greater length. This excess length of optical transmission elements inside the optical cable ensures that when bending or Stretch the optical cable no excessive tensile stresses in the optical transmission elements occur. For example, you can in the case of a round-section optical cable, the optical transmission elements in the form of a helix about a along the longitudinal axis of the cable running Be stranded central element. The central element has a rigidity on, the tensile and compressive loads in the longitudinal direction of the optical cable prevented.

The known materials for soft core sheaths have the disadvantage that their melting point or softening point is less than 85 ° C. Already temperatures of about 85 ° C therefore have a softening or melting of the buffer tubes of the optical transmission elements result. In this case, the wire sheaths of two adjacently arranged optical transmission elements of the optical cable can merge together or stick together. Furthermore, the wire sheath of an optical Übertragungsele Mentes also stick to the cable sheath of the optical cable or with an enclosed by the wire sheath fiber optic cable. Adhesion of the core sheaths of two adjacent optical transmission elements with each other or sticking of the core sheath of an optical transmission element to the cable sheath has a disadvantageous effect on the assembly and connection technology of the optical cable. Adhesion of the core sheath of an optical transmission element with an optical waveguide has a disadvantageous effect on the optical transmission properties. At a gluing point, bending of the optical transmission element may result in macrobending of the optical waveguide. Between two gluing sites, a compressive load caused by the bending can lead to microbending of the optical waveguide. Both macrobending and microbending amplify the light output from the glass fiber and thus the attenuation of optical signals. Furthermore, the separation of a bonded to the core tube optical waveguide is difficult.

By the use of one of the known soft materials for the core of a optical transmission element is the temperature at which the optical transmission element is used can be limited to temperatures below 85 ° C. In particular, the temperature is in which the optical transmission element can be further processed to an optical cable, to temperatures below 85 ° C limited.

One optical cable is made by first optical transmission elements formed and then the optical transmission elements to a optical cables are further processed. Each one of the optical transmission elements is formed by the optical waveguides are fed to an extruder head, in which a vein cover is extruded around the optical fibers. The optical transmission elements are processed into an optical cable by a cable sheath around the optical transmission elements is trained. In this case, the cable sheath is formed by in particular the optical transmission elements supplied to an extruder head in which a transverse pressure-stable protective cover around the optical transmission elements is extruded.

at the further processing of the optical transmission elements for the production of the optical cable, especially when extruding the transverse pressure stable Cover, can the vein cover one of the optical transmission elements a dependent on the material and the withdrawal speed of the protective cover temperature from above Reach 85 ° C, what a sticking of the conductor sleeve with an optical waveguide of the optical transmission element, with the buffer tube an adjacent optical transmission element or with the cable sheath of the optical cable result.

Further known materials for the vein cover optical transmission elements are, for example, polybutylene terephthalate (PBT), polycarbonates (PC), mixtures of polybutylene terephthalates and polycarbonates but also polypropylene.

These However, materials have the disadvantage that they are very hard. Therefore, you can Wire sheaths off these materials can not be removed without special tools, to expose the optical fibers.

Accordingly It is an object of the invention to provide an optical cable, its optical transmission elements a vein cover have, the elongation at break so small is that the vein cover Can be removed without special tools to the optical fibers and whose melting point is so high that the vein cover at Temperatures of up to 85 ° C not softened.

According to the invention Task solved by an optical cable having the features of claim 1.

The according to the invention optical Cable comprises a cable sheath with at least two optical transmission elements, which are arranged within the cable sheath. Of the at least two optical transmission elements comprises at least one optical waveguide and a conductor sheath, which surrounds the at least one optical waveguide. The vein sheath contains a Matrix material and a filler embedded in the matrix material, the melting point of the matrix material is at least 85 ° C and the Mass fraction of the filler on the entire mass of the conductor sleeve is at least 30%.

The wire sheath of the optical transmission element thus comprises a matrix material and a filler. The melting point of the buffer tube is determined by the melting point of the matrix material. By choosing a matrix material with a melting point of at least 85 ° C to obtain a wire sheath that does not melt or soften during further processing of the optical transmission element for producing an optical cable. An optical cable with optical transmission elements having such a core sheath is therefore very flexible and can be bent without the attenuation of optical signals in the optical waveguides increases. Further, the elongation at break of the buffer tube is determined by the mass fraction of the matrix material embedded filler on the entire mass of the buffer tube determined. If, for example, the mass fraction of the filler in the total mass of matrix material and filler is at least 30%, the elongation at break or the tensile strength of the buffer tube are reduced so that they can be removed without special tools. This greatly simplifies the handling of an optical cable having optical transmission elements having such a buffer tube.

Preferably is the matrix material of the wire hull an optical transmission element thermoplastic polymer having a melting point of at least 110 ° C and the filler embedded in the matrix material is a mineral.

By the choice of a thermoplastic polymer having a melting point of more than 110 ° C as Matrix material receives a vein cover the optical transmission element, their melting point significantly higher as 85 ° C lies. Therefore, at the further processing of the optical transmission element for the production an optical cable can also be applied to process steps a warming the vein cover to temperatures of more than 85 ° C cause. By choosing a mineral as a filler is ensured that too the filler temperatures from above 85 ° C withstands. Further among the minerals are both passive fillers that only one Reduction of elongation at break the vein cover cause, as well as active fillers, the vein cover additional confer advantageous properties. For example, suitable active ones fillers By elimination of water cause a flame retardancy of the buffer tube or by water absorption, a propagation of water in the longitudinal direction prevent the optical cable.

Preferably is the mass fraction of the filler on the wire hull an optical transmission element between 60 and 70%.

If the matrix material of the buffer tube an optical transmission element in addition to a sufficiently high melting point or softening point one too big Has hardness, then the required reduction of the elongation at break of the buffer tube by increase the mass fraction of the filler on the entire mass of filler and matrix material.

Preferably contains the matrix material of the buffer tube an optical transmission element Polyolefin.

The Matrix material of the buffer tube an optical transmission element may also contain polyethylene, for example "Low Density Polyethylene" (LDPE), "Medium Density Polyethylene" (MDPE) or "High Density Polyethylene" (HDPE).

Especially For example, the matrix material of the buffer tube of an optical transmission element can be polypropylene contain.

Preferably contains the matrix material of the buffer tube an optical transmission element Elastomer or a copolymer of an elastomer.

Especially can the filler the vein cover an optical transmission element Chalk included.

in the Generally, chalk reduces as a filler in a matrix material embedded with a melting point of at least 85 ° C, only the elongation at break the vein cover. Chalk is a passive filler.

Preferably contains the filler the vein cover an optical transmission element Magnesium hydroxide or aluminum hydroxide.

in the Generally, a metal hydroxide acts as a filler is inserted into a matrix material having a melting point of more than 85 ° C, a Flame retardancy of the vein cover. Metal hydroxides are active fillers. The flame retardance of matrix materials containing metal hydroxides filled are, is due to that Metal hydroxides on oxidation split off water.

One active filler can also be a swellable Powder contain (SAP = super absorbent polymer). The swellable powder can be a polyacrylic acid or a salt of a polyacrylic acid such as sodium polyacrylate included.

Preferably The cable sheath of the optical cable comprises polyethylene or polypropylene or Polyamide.

at the further processing of the optical transmission elements for the production an optical cable whose cable sheath is one of these materials contains occur in general process steps in the course of which buffer tube an optical transmission element reaches a temperature of over 85 ° C. Therefore, an optical cable with such a cable jacket should have optical transmission elements with a conductor sleeve contained, which withstands these temperatures.

It Another object of the invention is a method of preparation specify an optical cable, in which the bonding of an optical transmission element with a further optical transmission element, is avoided with the cable sheath or with an optical fiber.

According to the invention The object is achieved by the method for producing an optical cable solved with the features of claim 9.

The inventive method for making an optical cable comprises a step of Generating at least two optical transmission elements and a subsequent Step of creating a cable sheath around the at least two optical transmission elements, the heating the vein cover to a temperature of at least 85 ° C. In this case, the generation takes place of at least one of the two optical transmission elements by a Step of providing at least one optical fiber, a subsequent Step of providing a mixture comprising a matrix polymer with a melting point of at least 85 ° C and a filler wherein the mass fraction of the filler in the total mass of the filler and the matrix polymer is at least 30%, and a subsequent step the formation of a conductor sleeve around the at least one optical waveguide by extruding the buffer tube from the mixture of the filler and the matrix polymer.

By the inventive method for making an optical cable are optical transmission elements with a wire sheath, which has a high melting point and a low elongation at break, generated. Therefore, in the further processing of the optical transmission elements for producing the optical cable even when heating the buffer tube at temperatures above 85 ° C no sticking of the optical transmission element with a further optical transmission element, with the cable sheath or with an optical fiber.

Preferably The step of providing the matrix material comprises one Step of providing a thermoplastic polymer and the step of providing a filler is a step of Providing a mineral.

Preferably The step of creating the cable sheath comprises a step of extruding polyethylene or polypropylene or polyamide.

The Figure shows an optical cable according to an embodiment of the present invention.

The optical cable shown in the figure 1 includes a cable sheath 11 and a plurality of optical transmission elements 101 and 102 , The cable sheath 11 may contain polyethylene (PE) or polypropylene (PP) or polyamide (PA). The optical transmission elements 101 and 102 are inside the cable sheath 11 arranged. The optical cable 1 has a round cross-section. In a section of the optical cable 1 which has a certain length are portions of the optical transmission elements 101 and 102 arranged, which have a slightly greater length. Due to this excess length of the optical transmission elements 101 and 102 in the section of the optical cable 1 can when bending or stretching the optical cable 1 no excessive mechanical stresses in the optical transmission elements 101 and 102 occur. For example, the excess length of the optical transmission elements 101 and 102 by shrinking the cable sheath 11 or by roping on a central element, for example a source yarn 12 , be generated.

The optical cable 1 may be a number of 12 optical transmission elements, such as the optical transmission elements 101 and 102 , contain. The number of 12 optical transmission elements may be characterized by a corresponding number of distinguishable colors. For example, the core sleeve 1011 of the transmission element 101 have one of the 12 distinguishable colors.

The optical transmission element 101 includes a vein cover 1011 and multiple optical fibers 10101 and 10102 , The buffer tube contains a matrix polymer and a filler embedded in the matrix polymer. The matrix polymer has a melting or softening point greater than 85 ° C. The buffer tube preferably contains a thermoplastic polymer having a melting point of at least 110 ° C, that is, 110 ° C or more than 110 ° C. The core can contain a polyolefin, in particular polyethylene (PE) or polypropylene (PP). In particular, the matrix polymer may contain "Low Density Polyethylene" (LDPE) or "Medium Density Polyethylene" (MDPE) or "High Density Polyethylene" (HDPE). The buffer tube may also contain an elastomer or a copolymer of an elastomer. The filler embedded in the matrix polymer reduces the elongation at break and tensile strength of the buffer tube. The mass fraction of the filler in the total mass of the buffer tube is at least 30%, ie 30% or more than 30%. Preferably, the mass fraction of the filler on the wire sheath is 60% to 70%. The filler preferably contains a mineral. For example, the filler may contain chalk. The filler may also contain a metal hydroxide, for example magnesium hydroxide or aluminum hydroxide, or a swellable material, for example a polyacrylic acid or a salt of a polyacrylic acid, such as sodium polyacrylate.

The optical fibers 10101 and 10102 are inside the wire hull 1011 arranged. The illustrated optical transmission element 101 has a round cross-section. In a section of the optical transmission element 101 which has a certain length are portions of the optical fibers 10101 and 10102 arranged, which have a slightly greater length. Due to this excess length of optical fibers 10101 and 10102 in the section of the optical transmission element 101 can when bending or stretching the optical cable 1 no excessive tensile stress in the optical fibers 10101 and 10102 occur. For example, the optical fibers 10101 and 10102 be arranged in the form of a helix about the longitudinal axis of the section.

The optical transmission element 101 may be a number of 12 optical fibers, such as the optical fibers 10101 and 10102 , contain. The number of 12 optical fibers may be characterized by a corresponding number of distinguishable colors. For example, the optical waveguide may comprise a glass fiber and a fiber coating (coating), which surrounds the glass fiber. In this case, the fiber coating of the optical waveguide may have one of the 12 distinguishable colors.

When bending or stretching the optical cable 1 the optical transmission elements move 101 and 102 inside the cable sheath 11 as well as the optical fibers 10101 and 10102 inside the core 1011 such that mechanical stresses are minimized. For this it is necessary that the optical fibers 10101 and 10102 in the longitudinal direction of the optical transmission element 101 relative to each other and relative to the wire hull 1011 are easily displaced. Furthermore, it is necessary that the optical transmission elements 101 and 102 relative to the longitudinal direction of the cable 1 relative to each other and relative to the cable sheath 11 are displaceable.

According to the invention, the core sheath 1011 of the optical transmission element 101 both a high melting or softening point and a low elongation at break. This will cause sticking of the conductor sleeve 1011 with the optical transmission element 102 , with the cable sheath 11 or with the source yarn 12 prevented. Furthermore, a gluing of the core sheath 1011 of the optical transmission element 101 with the optical fibers 10101 and 10102 prevented. As a result, the optimum mobility of the optical waveguides within an optical transmission element and the optimal mobility of the optical transmission elements within the optical cable is maintained. Mechanical stresses, in particular tensile and compressive stresses on the optical waveguides within an optical transmission element and tensile and compressive stresses on the optical transmission elements within an optical cable can thus be effectively minimized.

As the vein cover 1011 of the optical transmission element 101 According to the invention has a low elongation at break, it can be removed without special tools to expose the optical fibers.

The low tensile strength of the buffer tube associated with the low elongation at break 1011 is not detrimental because of the high melting point or softening point of the buffer tube 1011 a sticking of the conductor sleeve 1001 with adjacent surfaces in the optical cable 1 prevents and thus a high mobility of optical fibers 10101 and 10102 relative to each other and relative to the wire hull 1011 and a high mobility of the optical transmission elements 101 and 102 relative to each other and relative to the cable sheath 11 ensures.

The optical cable 1 is manufactured by first optical transmission elements, such as the optical transmission elements 101 and 102 trained and then processed the optical transmission elements to form an optical cable. In each case one of the optical transmission elements, for example the optical transmission element 101 , is formed by the optical waveguides, such as the optical fibers 10101 and 10102 fed to an extruder head, with which a wire sheath 1011 is formed around the optical waveguide. The vein cover 1011 For example, it is formed by providing a mixture of a matrix material and a filler and the buffer tube 1011 is extruded from the mixture. The matrix material has a melting point of more than 85 ° C and the mass fraction of the filler in the total mass of the mixture is at least 30%. The matrix material is, for example, a thermoplastic polymer having a melting point of at least 110 ° C. The matrix polymer may in particular be a polyolefin, for example polyethylene or polypropylene, in particular LDPE or MDPE or HDPE, or an elastomer or a copolymer of an elastomer.

The optical transmission elements, for example the optical transmission elements 101 and 102 , become an optical cable 1 further processed by a cable sheath 11 is formed around the optical transmission elements. In this case, the cable sheath 11 formed by the optical transmission elements are fed to an extruder head, by means of which a transverse pressure-stable protective cover is extruded around the optical transmission elements. This can be the vein shell 1011 be heated to temperatures of more than 85 ° C.

From the specified materials, a matrix polymer having a melting or softening point sufficiently above the highest in the manufacture of the optical cable can be selected 1 reached temperature is to stick the core cover 1011 with adjacent surfaces within the optical cable 1 to avoid. Further, by filling the matrix polymer with a filler whose mass fraction of the bulk of the buffer layer is at least 30%, an elongation at break of the buffer tube 1011 be set sufficiently low to remove the core cover 1011 from the optical transmission element 101 without allowing special tools.

1

optical electric wire

11

cable sheath

12

swellable yarn

101 102

Optical transmission element

1011

buffer tube

10101, 10102

optical fiber

Claims (11)

Optical cable ( 1 ), comprising: a cable sheath ( 11 ); at least two optical transmission elements ( 101 . 102 ) inside the cable sheath ( 11 ) and at least one of which ( 101 ) comprises: at least one optical waveguide ( 10101 . 10102 ); a wire sheath ( 1011 ), which the at least one optical waveguide ( 10101 . 10102 ), wherein the core ( 1011 ) contains a matrix material and a filler embedded in the matrix material, the melting point of the matrix material is more than 85 ° C and the mass fraction of the filler at the core sheath ( 1011 ) is at least 30%. Optical cable ( 1 ) according to claim 1, wherein the matrix material of the buffer tube ( 1011 ) of at least one ( 101 ) of the at least two optical transmission elements ( 101 . 102 ) is a thermoplastic polymer having a melting point of at least 110 ° C and the filler embedded in the matrix material is a mineral. Optical cable ( 1 ) according to claim 1 or 2, in which the mass fraction of the filler on the buffer tube ( 1011 ) of at least one ( 101 ) of the at least two optical transmission elements ( 101 . 102 ) is between 60% and 70%. Optical cable ( 1 ) according to one of claims 1 to 3, in which the matrix material of the buffer tube ( 1011 ) of the one ( 101 ) of the at least two optical transmission elements ( 101 . 102 ) contains a polyolefin having a melting point of at least 110 ° C. Optical cable ( 1 ) according to one of claims 1 to 3, in which the matrix material of the buffer tube ( 1011 ) of the one ( 101 ) of the at least two optical transmission elements ( 101 . 102 ) Polyethylene, polypropylene, an elastomer or a copolymer of an elastomer having a melting point of at least 110 ° C. Optical cable ( 1 ) according to one of claims 1 to 3, in which the matrix material of the buffer tube ( 1011 ) of the one ( 101 ) of the at least two optical transmission elements ( 101 . 102 ) Low Density Polyethylene or Medium Density Polyethylene or High Density Polyethylene with a melting point of at least 110 ° C contains. Optical cable ( 1 ) according to one of Claims 1 to 3, in which the filler of the buffer tube ( 1011 ) of the one ( 101 ) of the at least two optical transmission elements ( 101 . 102 ) Contains chalk or magnesium hydroxide or aluminum hydroxide or a polyacrylic acid or a salt of a polyacrylic acid. Optical cable according to one of Claims 1 to 8, in which the cable sheath ( 11 ) Polyethylene or polypropylene or polyamide. Method for producing an optical cable ( 1 ) comprising the steps: generating at least two optical transmission elements ( 101 . 102 ), wherein generating at least one ( 101 ) of the at least two optical transmission elements ( 101 . 102 ) comprises the steps of: providing at least one optical waveguide ( 10101 . 10102 ); Providing a mixture of a matrix material and a filler, wherein the matrix material has a melting point of at least 85 ° C and the mass fraction of the filler in the total mass of the mixture is at least 30%; and forming a wire sheath ( 1011 ), the at least one optical fiber ( 10101 . 10102 ) surrounds by extruding the wire sheath ( 1011 ) from the mixture; and wherein subsequently a step of producing a cable sheath ( 11 ), which comprises the at least two optical transmission elements ( 101 . 102 ), is provided, the heating of the core sheath ( 1011 ) to a temperature of 85 ° C. The method of claim 9, wherein the step of providing the mixture comprises a step of providing a mixture of a ther moplastic polymer having a melting point of at least 110 ° C and a mineral, the mass fraction in the total mass of the mixture is 60% to 70% comprises. Method according to claim 9 or 10, wherein the production of the cable sheath ( 11 ) comprises: extruding polyethylene or polypropylene or polyamide.