JP3783946B2 - Fiber optic cable - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical fiber cable used for a subscriber-system optical wiring of an access-system optical network.
[0002]
[Prior art]
As an optical fiber cable for wiring to subscribers such as general houses and buildings, a tensile body 2 made of two steel wires is arranged above and below the optical fiber core 1 as shown in FIG. The cable body 4 is formed by providing a jacket 3 made of a thermoplastic resin such as polyethylene on the outer periphery thereof, and this is a cable support wire 6 provided with a coating layer 5 that is extrusion-coated integrally with the jacket 3 on the outer periphery. A supported structure is known.
[0003]
In such an optical fiber cable, the tensile strength member 2 is disposed with the optical fiber core 1 sandwiched therebetween mainly to prevent an increase in transmission loss of the optical fiber due to a temperature change. If not provided, the jacket 3 expands and contracts due to temperature changes during use or cable manufacture, and accordingly, the optical fiber core 1 may be distorted and transmission loss may be greatly increased.
[0004]
However, even if the tensile body 2 is arranged, if the adhesion between the tensile body 2 and the jacket 3 is insufficient, the expansion and contraction of the jacket 3 due to temperature changes cannot be sufficiently prevented, resulting in transmission loss. May increase. Therefore, conventionally, an adhesive coating / baking layer is provided on the surface of the strength member 2, thereby increasing the adhesion between the strength member 2 and the jacket 3.
[0005]
[Problems to be solved by the invention]
However, in such a conventional optical fiber cable, the process for applying and baking the adhesive must be performed on a line different from the cable production line, resulting in an increase in production cost and production. There was a problem that time became long.
There is also a problem that an organic solvent contained as a solvent in the adhesive may volatilize during application baking to contaminate the environment.
[0006]
The present invention has been made to solve such a problem, and can be manufactured by one line without providing another line, and requires a separate line for applying and baking an adhesive. The purpose is to provide an optical fiber cable that can reduce the manufacturing cost and the manufacturing time, and does not require the use of harmful chemical substances and has a low environmental impact compared to the optical fiber cable of And
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 is directed to an optical fiber core, a tensile body arranged in parallel to the optical fiber core, and a first extrusion coated on the outer periphery thereof. A second thermoplastic resin different from the first thermoplastic resin that is melted by heat when the outer cover is extrusion coated on the surface of the tensile body. The coating made of the second thermoplastic resin is a low-density polyethylene or straight coating having a melt viscosity (MFR) of 0.8 g / 10 min or more coated in the same line as the outer coating. An optical fiber cable having a coating made of chain low density polyethylene.
[0008]
In the optical fiber cable having the above-described configuration, the surface of the tensile strength body is provided with a coating made of a thermoplastic resin (second thermoplastic resin) that melts with heat when the coating is extrusion coated. At the time of extrusion coating, the coating made of the thermoplastic resin (second thermoplastic resin) provided on the surface of the tensile body is once melted, and then cooled together with the thermoplastic resin (first thermoplastic resin) that forms the jacket. As a result, it is solidified integrally, and the adhesion between the strength member and the jacket is ensured. This eliminates the need for a separate line for applying and baking an adhesive to a conventional tensile strength body, and can be manufactured on a single line, reducing manufacturing costs and manufacturing compared to conventional optical fiber cables. Time can be shortened. In addition, since no harmful chemical substances such as organic solvents are used, the burden on the environment is reduced.
[0009]
To achieve the above object, the invention described in claim 2 is characterized in that, in the optical fiber cable according to claim 1, the thickness of the coating made of the second thermoplastic resin is 10 to 150 μm. An optical fiber cable.
[0010]
If the thickness of the coating made of the second thermoplastic resin is less than 10 μm, there is a risk that sufficient adhesion between the strength member and the jacket may not be obtained, and if it exceeds 150 μm, the thickness of the cable increases. In order to prevent this, the jacket must be relatively thin, and the mechanical strength is reduced.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a first embodiment of the optical fiber cable of the present invention.
[0014]
In FIG. 1, reference numeral 10 denotes a single-core optical fiber core 11 and steel wires or FRPs (glass fiber reinforced plastics) arranged parallel to each other with a space above and below the single-core optical fiber core 11. 1 shows a cable body composed of a tensile body 12 made of the above and a jacket 13 made of a thermoplastic resin that is collectively extruded and coated on the outside thereof, and 14 is a jacket made of a thermoplastic resin on the outer periphery. 15 shows a cable support wire made of a steel wire or the like provided with 15. The jacket 13 and the jacket 15 of the cable support line 14 are joined together by a narrow neck 16 made of a thermoplastic resin that is integrally extruded with the jacket 13. In order to facilitate the separation of the cable support wire 14 from the cable body 10 and the removal of the single-core optical fiber core wire 11 in cable terminal processing, a notch 17 for tearing is provided.
[0015]
In this embodiment, the surface of each strength member 12 is a thermoplastic resin that is different from the thermoplastic resin constituting the outer cover 13 and is melted by heat when the outer cover 13 is extrusion-coated. A coating 12a made of resin is provided, and the adhesion force between the strength member 12 and the outer jacket 13 is ensured by the coating 12a.
[0016]
Here, the thermoplastic resin constituting the outer sheath 13 and the thermoplastic resin constituting the coating 12a on the surface of the tensile strength body 12 are melted by the heat of the outer sheath 13 by extrusion coating. The type is not particularly limited as long as it satisfies the condition of performing, and may be the same type or different types.
[0017]
However, in any case, the polyolefin-based thermoplastic resin is preferable because generation of hydrogen gas that deteriorates the characteristics of the optical fiber is not observed. Specifically, as the thermoplastic resin constituting the outer cover 13, a flame retardant or filling Low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene copolymer, and other polyolefins with additives such as additives On the other hand, the thermoplastic resin constituting the coating 12a on the surface of the strength member 12 is preferably a low-density polyethylene, a linear low-density polyethylene, or a high-density polyethylene containing no or almost no additive. , Polypropylene, ethylene-vinyl acetate copolymer, Len - ethyl acrylate copolymer, ethylene - polyolefin thermoplastic resin such as propylene copolymer is preferably used.
[0018]
In the present invention, the use of low-density polyethylene or linear low-density polyethylene having a melt viscosity (MFR) of 0.8 g / 10 min or more as the thermoplastic resin constituting the coating 12a on the surface of the strength member 12 is particularly preferred. preferable.
[0019]
Further, the thickness of the coating 12a on the surface of the strength member 12 is preferably in the range of 10 to 150 μm, and if the thickness of the coating 12a is less than 10 μm, the adhesion force between the strength member 12 and the jacket 13 may not be sufficiently obtained. If the thickness exceeds 150 μm, the jacket 13 must be made relatively thin in order to prevent an increase in the thickness of the cable, and the mechanical strength is lowered.
[0020]
In the optical fiber cable configured as described above, the coating 12a made of a thermoplastic resin that melts by heat when the coating 13 is extrusion coated on the surface of the strength member 12 is provided. At the time of coating, the coating 12a made of a thermoplastic resin provided on the surface of the strength member 12 is once melted, and then cooled together with the thermoplastic resin forming the outer sheath 13 to be solidified integrally. Is ensured. For this reason, a separate line for applying and baking an adhesive to the strength member 12 as in the prior art is not required, and it can be manufactured in a single line, and the manufacturing cost can be reduced as compared with the conventional optical fiber cable. Manufacturing time can be shortened. In addition, since no harmful chemical substances such as organic solvents are volatilized during production, the burden on the environment is small.
[0021]
Next, another embodiment of the present invention will be described.
FIG. 2 is a cross-sectional view according to the second embodiment of the present invention, and parts common to FIG.
[0022]
The optical fiber cable of the present embodiment is an optical fiber in which four optical fiber strands 18a are arranged in parallel instead of the single-core optical fiber core 11 in the first embodiment, and a collective coating 18b is applied to the outer periphery thereof. The optical fiber ribbon 18 is used, and two strength members 12 are arranged in parallel on both sides in the width direction with the optical fiber ribbon 18 interposed therebetween.
[0023]
Also in the optical fiber cable configured as described above, as in the case of the first embodiment, the coating 12a made of the thermoplastic resin provided on the surface of the strength member 12 is once melted during the extrusion coating of the outer cover 13, and thereafter Since it is cooled together with the thermoplastic resin forming the outer cover 13 to solidify integrally and the tensile body 12 and the outer cover 13 are bonded, another line for applying and baking an adhesive on the conventional tensile body 12 Therefore, the manufacturing cost can be reduced and the manufacturing time can be shortened as compared with the conventional optical fiber cable. In addition, since no harmful chemical substances such as organic solvents are volatilized during production, the burden on the environment is small.
[0024]
In each of the above embodiments, the number of the single-core optical fibers 11 is not particularly limited to one, and may be two or more. Also in the second embodiment, the number of the optical fiber ribbons 18 is not limited to one and may be two or more. Further, the configuration of the optical fiber ribbon 18 is not particularly limited to the four-fiber ribbon as illustrated, but for example, a two-fiber ribbon or an eight-fiber ribbon. There may be.
[0025]
Moreover, the cable support line 14 is not necessarily essential, and may be configured by only the cable body 11 depending on the application.
[0026]
【Example】
Next, although the Example of this invention is described, it cannot be overemphasized that this invention is not what is limited to these Examples.
[0027]
Example 1
The optical fiber cable having the structure shown in FIG. 1 was produced on one production line equipped with first and second extruders. The single-core optical fiber core wire 11 is a single-core optical fiber core wire having an outer diameter of 250 μm, the tensile body 12 is made of a wire made of FRP having an outer diameter of 0.4 mm, and the cable support wire 14 is A single steel wire having a diameter of 1.2 mm was used.
First, unextruded low density polyethylene (MFR = 1.0 g / 10 min ) was extruded on the surfaces of the two strength members 12 by the first extruder to form a coating 12a having a thickness of 100 μm, Introduced into the second extruder together with the single-core optical fiber core wire 11 and the cable support wire 14, the outer periphery thereof is extrusion-coated with an ethylene-vinyl acetate copolymer blended with a flame retardant and a filler, and the width of the jacket 13 Is about 3 mm, the same thickness is about 2 mm, and the total width including the cable support line 14 is about 5 mm.
[0028]
Example 2
An optical fiber cable was manufactured in the same manner as in Example 1 except that two single-core optical fibers 11 were arranged in parallel vertically.
[0029]
Example 3
The structure shown in FIG. 2 is the same as that of the first embodiment except that a four-core optical fiber ribbon 18 having a width of about 1.1 mm and a thickness of about 0.3 mm is used in place of the single-core optical fiber 11. An optical fiber cable was manufactured.
[0030]
Example 4
An optical fiber cable was manufactured in the same manner as in Example 3 except that two four-core optical fiber ribbons 18 were laminated in the thickness direction.
[0031]
About the optical fiber cable obtained in each said Example, the heat cycle test and the ironing test were done, and the characteristic was evaluated. In the heat cycle test, 10 heat cycles of −30 ° C. to + 70 ° C. were performed to examine an increase in transmission loss. In the ironing test, the cable was bent 90 ° with a radius of 250 mm, applied with 1960 N tension and subjected to ironing for 10 cycles, followed by 10 heat cycles from -30 ° C to + 70 ° C. The increase in transmission loss was investigated.
[0032]
As a result, in both the heat cycle test and the ironing test, the loss increase amount was 0.03 dB / km or less, and it was confirmed that it had good characteristics. Incidentally, these results were almost the same as those of a conventional optical fiber cable in which an adhesive was applied and baked on the surface of the strength member 12.
[0033]
【The invention's effect】
As described above, according to the optical fiber cable of the present invention, the surface of the tensile strength body is provided with a coating made of a thermoplastic resin that melts with heat when the outer cover is extrusion coated. No separate line for applying and baking adhesive on the body is required, and it can be manufactured on a single line, reducing manufacturing costs and shortening manufacturing time compared to conventional optical fiber cables. Can do. In addition, since no harmful chemical substances such as organic solvents are used, the burden on the environment can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first embodiment of an optical fiber cable of the present invention.
FIG. 2 is a cross-sectional view showing a second embodiment of the optical fiber cable of the present invention.
FIG. 3 is a cross-sectional view showing an example of a conventional optical fiber cable.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ......... Cable body 11 ......... Single-core optical fiber core wire 12 ......... Strength body 12a ......... Coating 13 ......... Outer sheath 18 ......... Optical fiber tape core wire

Claims (2)

An optical fiber core wire, a tensile body disposed in parallel with the optical fiber core wire, and a jacket made of a first thermoplastic resin collectively extrusion-coated on the outer periphery of the optical fiber core wire. The surface is provided with a coating made of a second thermoplastic resin different from the first thermoplastic resin that is melted by heat when the outer cover is extrusion coated. The coating is made of the second thermoplastic resin. The optical fiber is characterized in that the coating is a coating made of low-density polyethylene or linear low-density polyethylene having a melt viscosity (MFR) of 0.8 g / 10 min or more and coated in the same line as the jacket. cable.   The optical fiber cable according to claim 1, wherein a thickness of the coating made of the second thermoplastic resin is 10 to 150 µm.

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