JPH10232333A - Optical fiber unit and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to easily provide a sheath which is hardly breakable and to make mass smaller when this optical fiber unit is of the same outside diameter as an optical fiber unit not provided with this sheath and has the same rigidity by making the outermost layer to low-foaming or non- foaming. SOLUTION: For example, 7 pieces of optical fibers 1 are used and are stranded or are bundled without stranding these fibers. The bundle formed in such a manner is coated thereon with a primary coating layer 2. For example, optical fibers coated with a UV curing resin of 0.25mm in outside diameter are used as the optical fibers 1. The primary coating layer 2 is the foaming layer of foamed polyethylene(PE), etc. The secondary coating layer 3 applied on the primary coating layer 2 is a layer of lower foaming than the foaming layer of the primary coating layer or a non-foaming layer is used for the same. For example, the low-foaming or non-foaming PE is used. The low-foaming is determined from the degree at which the sheath hardly receives external flaws and buckling. The low-foaming is thus a foaming rate of <=40%, more preferably <=30%. As a result, the surface is made smooth and marked characters and symbols are made easier to read.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber unit laid by a flow of a fluid in a laid pipe, and a method of manufacturing the same.

[0002]

2. Description of the Related Art An optical fiber unit laid by a flow of a fluid in a laid pipe is disclosed in Japanese Unexamined Patent Publication No. Hei.
As described in Japanese Patent No. 289805, there is used an optical fiber unit in which optical fibers are assembled, a primary coating is applied, and a secondary coating of foamed polyethylene is applied thereon.

FIG. 3 is a sectional view of a conventional optical fiber unit. In the figure, 1 is an optical fiber, 7 is a primary coating layer, and 8 is a secondary coating layer. The primary coating layer 7 is a non-foamed layer of nylon, ultraviolet curable resin, silicone resin, or the like. The secondary coating layer 8 applied on the primary coating layer 7
It is a polyethylene foam layer and is provided with a sufficient thickness.

The reason why the foam layer is used as the secondary coating layer 8 of the optical fiber unit is that the coating is reduced in weight by using the foam layer so that a longer pipe route can be transmitted in a shorter time. It is. However, if the foaming rate is too high because the weight of the unit is too low, the rigidity is reduced and the optical fiber is easily broken due to local bending, or the foamed layer is broken and the optical fiber jumps out, or the foamed layer is crushed. Therefore, there is a problem that the contact area between the unit and the pipe is increased and the frictional resistance is increased, thereby deteriorating the pumping characteristics or making it difficult to mark on the optical fiber unit.

[0005] The optical fiber unit described in Japanese Patent Application Laid-Open No. Hei 3-238410 has a structure in which hollow spheres are mixed in consideration of a problem in the production of a foamed layer and adhesion of a foamed layer and a base. However, there is a problem that the hollow spheres must be uniformly mixed with the energy-curable resin composition.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and solves the problem of the strength of a foamed layer to effectively use an optical fiber unit using a foamed layer. It is intended to aim at.

[0007]

According to a first aspect of the present invention, there is provided an optical fiber unit laid by a flow of a fluid in a laid pipe, wherein the optical fiber unit includes at least one optical fiber. A foam layer is formed on the outer periphery of the bundle, and a low-foam or non-foam coating layer having a thickness smaller than that of the foam layer is formed thereon.

According to a second aspect of the present invention, in the optical fiber unit according to the first aspect, a non-foamed layer is provided between the converged optical fiber and the foamed layer. It is.

According to a third aspect of the present invention, in the method for manufacturing an optical fiber unit laid by a flow of a fluid in a laid pipe, a foam layer is formed on an outer periphery where at least one optical fiber is bundled. After that, a low-foaming or non-foaming coating layer thinner than the foamed layer is applied thereon in tandem.

According to a fourth aspect of the present invention, there is provided a method of manufacturing an optical fiber unit laid by a flow of a fluid in a laid pipe, wherein a foam layer is formed on an outer periphery where at least one optical fiber strand is focused. The present invention is characterized in that a low-foaming or non-foaming coating layer having a thickness smaller than that of the above foaming layer is applied by a dual die.

According to a fifth aspect of the present invention, in the method for manufacturing an optical fiber unit laid by a flow of a fluid in a laid pipe, a foam layer is formed on an outer periphery where at least one optical fiber is bundled. Then, heat is applied to the periphery of the foamed layer to melt the surface, so that only the surface of the foamed layer is a low foaming or non-foaming coating layer.

According to a sixth aspect of the present invention, in the method for manufacturing an optical fiber unit according to any one of the third to fifth aspects, heat is applied to the optical fiber before applying the foamed layer. It is a feature.

According to a seventh aspect of the present invention, in the method for manufacturing an optical fiber unit according to any one of the third to fifth aspects, a non-foamed layer is applied before the foamed layer is applied. Things.

[0014]

FIG. 1 is a sectional view of an optical fiber unit according to a first embodiment of the present invention. In the figure, 1 is an optical fiber, 2 is a primary coating layer, and 3 is a secondary coating layer. In this embodiment, seven optical fiber wires 1 are used, twisted or bundled without being twisted, and the primary coating layer 2 is coated thereon. The number of optical fiber strands to be focused is not limited to seven, but may be one or two or more. In addition, the present invention is not limited to focusing only the optical fiber, but may include an intervening string or a tear string together. In the specific example, an optical fiber coated with an ultraviolet curable resin having an outer diameter of 0.25 mm was used as the optical fiber. The primary coating layer 2 is a foamed layer made of foamed polyethylene or the like.
The secondary coating layer 3 is a layer that is lower in foaming than the foaming layer of the primary coating layer 2 or a non-foaming layer. In a specific example, low foaming or non-foaming polyethylene was used.

Here, the low foaming is determined based on the degree to which the outer cover is hardly damaged or damaged, and has a foaming ratio of 40% or less, preferably 30% or less. If the foaming ratio exceeds 50%, the foamed layer tends to be crushed. If the foaming ratio exceeds 70%, the casing is deformed only by winding the unit around a drum or the like. Regarding the influence of a wound or the like on the foaming ratio and the deformation state, the coating thickness of the foamed layer is 0.2 mm to
This is true if the range is 1.0 mm.

FIG. 4 shows the mass of the optical fiber unit when the outer diameter and the rigidity are the same among the outer diameter, rigidity and mass of the optical fiber unit which are the main parameters for determining the pumping characteristics of the optical fiber unit. It is a comparison of the mass of a conventional optical fiber unit.

An optical fiber unit according to an embodiment of the present invention comprises:
Seven strands of an optical fiber having an outer diameter of 0.25 mm are twisted together, coated with 50% foamed polyethylene until the outer diameter becomes 1.3 mm, and a 0.1 mm non-foamed layer ( Polyethylene).

The conventional optical fiber unit has an outer diameter of 0.2
After twisting seven 5 mm optical fiber strands,
Polyethylene having a foaming ratio of 27% is coated so that the rigidity becomes the same as that of the optical fiber of the present invention until the outer diameter becomes 5 mm.

Both have an outer diameter of 1.5 mm and a rigidity of 13.
6 kg · mm ² , but the mass of the optical fiber unit of the present invention is 1.12 g / m, which is 1.24 g / m of the conventional product.
It is lighter in weight and has excellent pumping characteristics.

The foaming rate of the outermost layer of the optical fiber unit according to the embodiment of the present invention is 0%, that is, non-foamed,
Since the foaming ratio was smaller than 27% of the conventional optical fiber unit, the surface was smooth and the characters and symbols marked were easy to read.

FIG. 2 is a sectional view of a second embodiment of the optical fiber unit according to the present invention. In the figure, 1 is an optical fiber, 4 is a primary coating layer, 5 is a secondary coating layer, and 6 is a tertiary coating layer. This embodiment differs from the first embodiment in that a non-foamed layer is interposed between the optical fiber and the foamed layer. Other parts are the same as those described in the first embodiment. Therefore, the secondary coating layer 5 and the tertiary coating layer 6 of this embodiment are the same as the primary coating layer 2 and the secondary coating layer 3 of the first embodiment. The description may be omitted because it may be the same as that described in the first embodiment.

For the non-foamed layer used as the primary coating layer 4, for example, an ultraviolet curable resin or a nylon resin is used.
For the primary coating layer 4, it is preferable to select a material having good adhesion to both the optical fiber and the foamed layer of the secondary coating layer.

Also in the optical fiber unit of this embodiment, the weight of the optical fiber unit is reduced as compared with the conventional product, and the optical fiber unit has excellent pumping characteristics.

As for the coating of the coating layer in the method of manufacturing the optical fiber unit of the present invention, it is possible to adopt a method of coating each coating layer by a tandem method in which the coating layers are sequentially coated using a coating die. In this manufacturing method, since the low-foaming or non-foaming coating layer can be applied after the foaming layer is applied and before winding on a drum or the like, the foaming layer is crushed and it is difficult to apply the low-foaming or non-foaming coating layer. The problem does not arise.

Further, depending on the foaming rate of the foamed layer, a low-foamed or non-foamed coating layer can be immediately applied after the foamed layer is applied using a dual die. In the case of the optical fiber unit described in the second embodiment, the primary coating layer and the secondary coating layer may be coated with a dual die, and the tertiary coating may be coated with tandem.

The low-foaming or non-foaming coating layer is not limited to applying a layer different from the foaming layer using a tandem or dual die, and heat is applied around the coated foaming layer. In addition, the outermost coating layer may be applied by melting the surface so that only the surface of the foam layer becomes a low-foaming or non-foaming coating layer.

In the method of manufacturing an optical fiber unit according to the first embodiment, the optical fiber is heated before the foamed layer is coated on the optical fiber, so that A method of improving the adhesion between the optical fiber and the foam layer by slightly melting the applied foam layer may be adopted.

[0028]

As is clear from the above description, according to the first aspect of the present invention, the outermost layer is low foamed or non-foamed, so that the outer cover is not easily broken. Also, since the mass increases in proportion to the square of the outer diameter, the stiffness increases in proportion to the fourth power of the jacket, so that an optical fiber unit having a low foaming or non-foaming layer as the outermost layer Has the advantage of being able to reduce the mass when it has the same outer diameter and the same rigidity as compared with an optical fiber unit not provided with this. In addition, if the outermost layer is a foam layer, markings may be blurred,
Although it is difficult to discriminate due to bleeding, when the outermost layer is a low-foaming layer or a non-foaming layer, there is an effect that the marking is hardly blurred or bleeding. In addition, the low foaming or non-foaming coating layer is thinner than the foaming layer,
An increase in mass due to this provision can be reduced.

According to the second aspect of the present invention, since the non-foaming layer is provided between the converged optical fiber and the foaming layer, the covering of the foaming layer becomes easy and the adhesion is good. By selecting the material, the integration of the optical fiber and the foam layer can be enhanced.

According to the third aspect of the present invention, by applying the low foaming or non-foaming coating layer on the foaming layer in tandem, the foaming layer is crushed and it is difficult to apply the low foaming or non-foaming coating layer. Problem occurrence probability can be reduced.

According to the fourth aspect of the present invention, the coating can be applied simultaneously by applying the low-foaming or non-foaming coating layer on the foaming layer with a dual die.

According to the fifth aspect of the present invention, after applying the foamed layer, the surface is melted by applying heat to the periphery of the foamed layer,
By forming only the surface of the foam layer as a low-foaming or non-foaming coating layer, the coating process can be simplified.

According to the sixth aspect of the present invention, by applying heat to the optical fiber before applying the foamed layer, the adhesion between the optical fiber and the layer thereon can be improved.

According to the seventh aspect of the present invention, by applying the non-foamed layer before applying the foamed layer, an optical fiber unit having high adhesion between the foamed layer and the optical fiber can be manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical fiber unit according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an optical fiber unit according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a conventional optical fiber unit.

FIG. 4 is an explanatory diagram comparing characteristics of an optical fiber unit according to the present invention and a conventional optical fiber unit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical fiber strand, 2 ... Primary coating layer, 3 ... Secondary coating layer, 4 ... Primary coating layer, 5 ... Secondary coating layer, 6 ... Tertiary coating layer.

Claims (7)

[Claims] 1. An optical fiber unit laid by a flow of a fluid in a laid pipe, wherein the optical fiber unit is provided with a foam layer on an outer periphery where at least one optical fiber element is bundled, and a foam layer is formed thereon. An optical fiber unit provided with a low-foaming or non-foaming coating layer which is thinner than the foamed layer. 2. A non-foamed layer is provided between the converged optical fiber and the foamed layer.
An optical fiber unit according to item 1. 3. A method of manufacturing an optical fiber unit laid by a flow of a fluid in a laid pipe,
An optical fiber, comprising: applying a foamed layer to an outer periphery where at least one optical fiber strand is bundled; and applying a low-foamed or non-foamed coating layer having a thickness smaller than the foamed layer thereon in tandem. Unit manufacturing method. 4. A method of manufacturing an optical fiber unit laid by a flow of a fluid in a laid pipe,
A method of manufacturing an optical fiber unit, comprising applying a foam layer and a low-foam or non-foam coating layer having a thickness smaller than that of the foam layer on a periphery of at least one optical fiber bundle by a dual die. Method. 5. A method for manufacturing an optical fiber unit laid by a flow of a fluid in a laid pipe,
After applying a foam layer to the outer periphery where at least one optical fiber is bundled, heat is applied around the foam layer to melt the surface, and only the surface of the foam layer is coated with low foam or non-foam. A method for manufacturing an optical fiber unit, comprising a layer. 6. The method of manufacturing an optical fiber unit according to claim 3, wherein heat is applied to the optical fiber before applying the foam layer. 7. The method of manufacturing an optical fiber unit according to claim 3, wherein a non-foamed layer is applied before the foamed layer is applied.