JP2004077560A - Optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber cable using hollow pipes for insertion of optical fibers, which pipes are highly flexible, suppress the collapse by side pressure, permit easy insertion of optical fibers, and are stable for a long period even when the optical fiber cable is laid in the state of exposing the hollow pipes outdoors. <P>SOLUTION: The optical fiber cable (6) is provided with one or more hollow pipes (2) to be inserted with optical fiber units (3). The hollow pipes (2) to be inserted with the units (3) are thermoplastic resins having a crosslinked structure of 30 to 80% in the degree of crosslinking. <P>COPYRIGHT: (C)2004,JPO

Description

【００２０】
以上の内径減少率試験結果より、樹脂の架橋度を３０％以上で構成したものは、パイプに１００％の伸び歪みが印可されても、その伸び歪みは張力解放後には、ほとんど復元されることが判る。なお、この１００％伸び時の張力は２００Ｎｆ程度であり、この張力は中空パイプ単体での敷設張力の約１．３倍の張力である。
内径減少率試験の結果より、架橋度を３０％以上で構成した中空パイプは、敷設張力によるパイプの伸び歪み（パイプの内径減少）に対しても優れていることを示すものである。この結果より明らかなように、中空パイプの敷設時などで発生する伸び（パイプの内径減少）を防止する目的で用いている抗張力体を用いることなく中空パイプを構成することが可能であることを示すものである。
【００２１】
【表１】

【００２２】
【発明の効果】
以上説明したように、本発明の光ファイバケーブルは、中空パイプ内に抗張力体を用いず、架橋された熱可塑性樹脂で製造された中空パイプから構成され、その中空パイプの材料である熱可塑性樹脂は、架橋度が３０％以上８０％以下としているので、敷設時及び敷設後の側圧による潰れが少なく、光ファイバの挿入性に優れ、中空パイプの集合工程、またはケーブル敷設時での施工性に優れたものである。また、屋外に曝露状態で敷設されても長期間安定である。さらに、ケーブル内に抗張力体を用いていないので、ケーブルの外径を小さくすることができる。
【図面の簡単な説明】
【図１】本発明のケーブルの一例の断面図であり、１本の中空パイプのみからなるパイプ単体型光ファイバケーブルである。
【図２】本発明のケーブルの他の一例の断面図であり、複数の中空パイプを使用したパイプ集合型光ファイバケーブルである。
【符号の説明】
１　　パイプ単体型光ファイバケーブル
２　　中空パイプ
ａ　パイプ内径
ｂ　パイプ外径
３　　光ファイバユニット
４　　光ファイバユニットの被覆層
５　　光ファイバ心線
６　　パイプ集合型光ファイバケーブル
７　　押え巻
８　　ケーブル被覆層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical fiber cable having a hollow pipe for inserting an optical fiber core wire, and more particularly to a hollow pipe for inserting an optical fiber having improved lateral pressure characteristics.
[0002]
[Prior art]
In recent years, with the accelerated use of optical communication and the increase in the amount of information, optical fibers have been expanded to include short-distance communication from communication stations to subscribers in addition to long-distance communication between communication stations. There is a situation where optical fibers are laid down to the eaves. As one of the laying methods, a hollow pipe is laid to the eaves of a general household, and if necessary, an optical fiber is fed into the hollow pipe by a pneumatic method or pushed by hand, etc. A method has been studied in which a lead wire is inserted into the inside, and the optical fiber is drawn into and inserted into the hollow pipe by connecting the lead wire and the optical fiber, and some methods have been adopted.
As a method of laying such an optical fiber on a predetermined route, a cable having a required number of hollow pipes is laid on the route, and the optical fiber is later sent and laid by a pneumatic system into the hollow pipe. A method is known from Japanese Patent Publication No. 22921/1990.
[0003]
Some of the pipes used in these pipes have a tensile strength material such as steel wire or tensile strength fiber embedded in the pipe in order to prevent the pipe from being stretched due to the tension at the time of laying. . Also, in office buildings and the like, there is known a method of laying a pipe-assembled cable composed of several hollow pipes and inserting an optical fiber later by a pneumatic method or manual pushing as necessary.
For the hollow pipe, high-density polyethylene is generally widely used based on the price of the material, the frictional force with the optical fiber core wire, the track record of use as a cable constituent material, and the like.
[0004]
[Problems to be solved by the invention]
However, the above-mentioned hollow pipe for inserting an optical fiber using high-density polyethylene (hereinafter simply referred to as “hollow pipe”) is easily used when laying the cable or when laying only the hollow pipe (pipe-only cable). Since the hollow pipe is easily bent, the hollow pipe is crushed (buckled). Also, the hollow pipe may be crushed by an external force such as accidentally crushing the cable or the hollow pipe. In addition, the hollow pipe may be crushed by an external force applied to the optical fiber cable and the hollow pipe after the installation.
When trying to insert an optical fiber into a partially crushed hollow pipe, the optical fiber is caught at the crushed portion of the hollow pipe, which causes a problem that insertability is hindered. Further, if the hollow pipe is crushed by the lateral pressure after the optical fiber has already been inserted, problems such as an increase in transmission loss in the optical fiber inserted into the hollow pipe occur.
In addition, for those in which a tensile strength member is embedded in a hollow pipe, in a single-pipe optical fiber cable or a pipe-assembled optical fiber cable configured by assembling pipes, depending on the direction of bending, the pipe alone or The tensile strength member in the pipe of the pipe-aggregated optical fiber cable becomes tight, causing problems such as no bending.
The present invention is an optical fiber insertion hollow which is excellent in flexibility, suppresses crushing due to lateral pressure, has excellent optical fiber insertion properties, and is stable for a long time even when laying outdoors in a state where a hollow pipe is exposed. It is an object to provide an optical fiber cable using a pipe.
[0005]
[Means for Solving the Problems]
Means for Solving the Problems In view of the above objects, the present inventors have conducted intensive studies on the material of a hollow pipe and found that a resin having a crosslinked structure is good. Therefore, the present invention has been made based on these findings.
In order to achieve the above object, the present invention provides
(1) An optical fiber cable comprising one or more hollow pipes into which an optical fiber is inserted, wherein the hollow pipe into which the optical fiber is inserted is a thermoplastic resin having a crosslinked structure.
(2) The optical fiber cable according to (1), wherein the thermoplastic resin having a crosslinked structure has a degree of crosslinking of 30% or more and 80% or less.
(3) The optical fiber cable according to (1) or (2), wherein the optical fiber cable does not use a tensile member as a constituent member.
Is provided.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of the optical fiber cable having the hollow pipe of the present invention will be described in detail, but is not limited thereto, and various embodiments are possible within the scope described in the claims. is there.
1 and 2 show a typical configuration of the optical fiber cable according to the present invention in a state where an optical fiber is inserted.
FIG. 1 is a cross-sectional view schematically showing one example of the optical fiber cable of the present invention. The cable is a single-pipe optical fiber cable composed of only one hollow pipe. It can satisfy the characteristics as a cable. In FIG. 1, an optical fiber cable 1 has an optical fiber unit 3 inserted into a hollow pipe 2. The optical fiber unit 3 is composed of an optical fiber core 5 and a coating layer 4 of the optical fiber unit which covers the periphery thereof. The coating layer 4 of the optical fiber unit is made of polyethylene resin, styrene elastomer resin, rubber type. Resin or the like can be used. In this figure, the optical fiber unit 3 is represented by one optical fiber core 5, but if necessary, a plurality of optical fiber cores 5 may be assembled, or a plurality of optical fiber cores 5 may be used. Are arranged in parallel, and one or a plurality of tape-type optical fibers coated in a lump are laminated.
[0007]
FIG. 2 is a cross-sectional view schematically showing another example of the optical fiber cable of the present invention, which is a pipe aggregated optical fiber cable 6. .. Are assembled around a central hollow pipe 2, a holding roll 7 is provided on the outer periphery thereof, and the periphery thereof is covered with a cable coating layer 8. An optical fiber unit 3 having the same configuration as that described with reference to FIG. 1 is inserted into the hollow pipe 2. In the figure, seven hollow pipes 2 are shown in the pipe-assembled optical fiber cable 6, but the number of hollow pipes can be appropriately set according to demand in laying. Similarly, in the figure, the optical fiber unit 3 is inserted into the three hollow pipes 2, but the optical fiber unit 3 can be inserted as needed. The cable coating layer 8 can be composed of a sheath made of polyethylene, polyvinyl chloride, or the like.
As shown in FIGS. 1 and 2, the optical fiber cable according to the present invention does not use a tensile member such as a fiber such as an aromatic polyamide or a metal such as a steel wire anywhere. Further, the hollow pipe may have any size and the shape is circular in the figure, but may be flat if necessary.
[0008]
The hollow pipe 2 of the optical fiber cable of the present invention is made of a thermoplastic resin, and is not particularly limited as a thermoplastic resin. For example, a polyolefin type, an acrylic type, an α-olefin type, an ethylene / vinyl acetate type, Polyamide-based, vinyl chloride-based and the like, preferably, high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, the most preferred of the above materials is a pipe-type optical fiber cable It is a high-density polyethylene that has been used as a pipe construction material. The above-mentioned thermoplastic resins can be used alone or as a mixture of two or more as required.
[0009]
Further, in the hollow pipe 2 of the optical fiber cable of the present invention, it is preferable that the thermoplastic resin is crosslinked to a degree of crosslinking of 30% or more and 80% or less. The degree of cross-linking here is an average degree of cross-linking measured by a test method specified in “Appendix 7 of JIS K 6787“ Water pipe cross-linked polyethylene pipe ””.
The crosslinking method of the thermoplastic resin in the present invention is not particularly limited, but a silane crosslinking method in which a silane compound is grafted and then condensed, a peroxide crosslinking method in which an organic peroxide is blended, an electron beam Alternatively, a radiation irradiation crosslinking method using γ-rays and the like can be mentioned. The silane cross-linking method, which can be directly added to a thermoplastic resin and cross-linked by reacting with steam or the like at the time of extrusion processing or after extrusion processing, is required for equipment cost, production cost, control of the degree of cross-linking, etc. Recommended from a comprehensive perspective.
[0010]
If the degree of cross-linking of the hollow pipe resin is less than 30%, the effect of the mechanical properties improved by the cross-linking will be weakened. Also, when laying or manufacturing a pipe-assembled optical fiber cable, if a tensile stress is applied to the pipe beyond its design, the pipe will expand and become smaller than the designed inside diameter of the pipe, and the Problems such as the inability to insert the fiber occur.
On the other hand, if the degree of crosslinking exceeds 80%, the rigidity of the pipe becomes too large, causing the following disadvantages.
1) In a case where a plurality of pipes are collectively assembled at a certain pitch and a holding coil is applied to form a pipe-assembled type optical fiber cable, it is difficult to twist the pipes at a specified pitch due to the rigidity of the pipe.
2) In the case of an optical cable in which a plurality of pipes are gathered, the bending stiffness of the cable becomes too large, and the workability at the time of laying the cable is impaired, depending on the number of pipes gathered.
Therefore, the degree of crosslinking of the obtained pipe is preferably 30% or more and 80% or less. Although it depends on the cable structure to be configured, the degree of cross-linking is more preferably 40% or more and 75% or less, further preferably 50% or more and 70% or less, in consideration of cable workability and lateral pressure characteristics.
[0011]
Furthermore, depending on the required characteristics, a material that does not contain a halogen-based material such as magnesium hydroxide, aluminum hydroxide, red phosphorus, silicone, or a bromine-based material as long as the function as an optical fiber insertion pipe is not impaired. Adds halogen-based flame retardants such as chlorine-based flame retardants and flame-retardant aids, applies deterioration prevention prescriptions such as carbon, UV inhibitors, and antioxidants, and uses color pigments to identify multiple pipes. And the like can be appropriately added. Further, for the purpose of improving the insertability of the optical fiber, a fatty acid lubricant such as stearic acid, oleic acid or erucic acid, or a silicone lubricant can be added or applied.
[0012]
Further, in order to facilitate the insertion of the optical fiber into the hollow pipe before or after the cable is laid, it is also possible to previously put a cord for drawing the optical fiber into the hollow pipe.
[0013]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
The thermoplastic resin used as an example is prepared by appropriately mixing a silane cross-linking agent with a high-density polyethylene having a density of 950 kg / m ³ and a flexural modulus of 1000 MPa so that the cross-linking degree shown in Table 1 is obtained. A hollow pipe having a diameter of 2.5 mm and an outer diameter of 4.5 mm was manufactured by extrusion molding. The obtained hollow pipe was put into a steam bath at a temperature of 98 ° C. in order to crosslink it, and hollow pipes having the degree of crosslinking of Examples and Comparative Examples were obtained.
The hollow pipe manufactured by the above-described method was tested and evaluated as a single product for a lateral pressure characteristic test, a bending characteristic test, and an inner diameter reduction rate test by the following methods. The results are shown in Table 1 below.
[0014]
(Side pressure characteristic test)
As a method for testing the crushing characteristics of a hollow pipe, one optical fiber unit containing a two-core tape having an outer diameter of 1.2 mm is inserted into the hollow pipe, and the pipe is sandwiched between both sides by a 50 mm length and width flat plate. The transmission loss of the optical fiber unit when a load of 550 N to 550 N was applied was measured using the cutback method. Although the measurement wavelength was set to two wavelengths of 1.31 μm and 1.55 μm, the increase in transmission loss at the measurement wavelength of 1.55 μm needs to be less than 0.1 dB for practical use. Table 1 shows the results of evaluation based on the following criteria.
：: Increase in transmission loss is less than 0.1 dB at the measurement wavelengths of 1.55 μm and 1.31 μm. X: Increase in transmission loss is 0.1 dB or more at either the measurement wavelength of 1.31 μm or 1.55 μm.
From the results of the above-mentioned lateral pressure characteristic test, the hollow pipe used in the example was subjected to a lateral pressure that causes an increase in transmission loss to the inserted optical fiber unit having an outer diameter of 1.2 mm even when a load of 550 N was applied to a 50 mm flat plate. It turns out that it is not. This indicates that the hollow pipe has a resin crosslink degree of 30% or more, thereby improving the lateral pressure characteristics of the pipe.
[0016]
(Bending property test)
As a method for testing the bending characteristics of the hollow pipe, seven hollow pipes having an outer diameter (b) of 4.5 mm (one pipe is disposed at the center as shown in FIG. 2 and six pipes are disposed on the outer periphery thereof) The assembled pipes were set so that the twist pitch was set to 600 mm ± 60 mm, and a press-winding tape was applied to the outer periphery of the collected pipes, and the pipes were fixed so that the pipes could not be untwisted.
The twist pitch of the obtained collective pipe was measured, and those having a finish tolerance of the twist pitch of 10% or less were judged as acceptable (indicated by と し), and those exceeding 10% were judged as unacceptable (indicated by “x”).
[0017]
From the results of the above bending characteristics, the hollow pipes used in the examples are assembled with a tolerance of 10% or less, whereas the hollow pipes of the comparative example with a degree of crosslinking of 90% have a result that the tolerance exceeds 10%. Was. This indicates that when the degree of cross-linking of the resin of the hollow pipe exceeds 80%, the rigidity of the pipe is too large to be assembled at a predetermined twist pitch. Although not shown in the examples, the results show that in the case of a hollow pipe having a degree of cross-linking of the resin of more than 80%, the rigidity as a cable increases.
[0018]
(Inner diameter reduction rate test)
As a method of testing the tensile elongation performance of the hollow pipe, a hollow pipe was cut out to a length of 150 mm using a Tensilon type tensile tester, a 20 mm mark line was attached to the center of the hollow pipe, a gripping interval was 25 mm, and a tensile speed was 50 mm. The tension was applied to the hollow pipe at a rate of / min. Next, the hollow pipe after releasing the tension is allowed to stand for 15 minutes or more, and the central portion between the marked lines attached to the hollow pipe after leaving is thinly sliced in the circumferential direction, and is magnified 10 times with a universal projector. And the inner diameter (a) of the hollow pipe was measured. A hollow pipe having an inner diameter reduction rate of 10% or less was judged as acceptable (indicated by ○), and a hollow pipe having an inner diameter reduction rate exceeding 10% was judged as unacceptable (indicated by ×).
The outer diameter reduction rate was determined by the following equation.
[0019]
(Equation 1)

[0020]
From the results of the above-described inner diameter reduction rate test, in the case where the degree of cross-linking of the resin is 30% or more, even if 100% elongation strain is applied to the pipe, the elongation strain is almost restored after the tension is released. I understand. The tension at 100% elongation is about 200 Nf, and this tension is about 1.3 times the laying tension of the hollow pipe alone.
The results of the inner diameter reduction rate test show that the hollow pipe having a degree of crosslinking of 30% or more is excellent in elongation strain (reduced inner diameter of the pipe) of the pipe due to laying tension. As is clear from this result, it is possible to construct the hollow pipe without using the tensile strength member used for the purpose of preventing the elongation (reduction of the inner diameter of the pipe) that occurs when the hollow pipe is laid. It is shown.
[0021]
[Table 1]

[0022]
【The invention's effect】
As described above, the optical fiber cable of the present invention does not use a tensile member in the hollow pipe, and is formed of a hollow pipe made of a crosslinked thermoplastic resin, and the thermoplastic resin which is a material of the hollow pipe is used. Has a degree of cross-linking of 30% or more and 80% or less, so that it is hardly crushed by lateral pressure at the time of laying and after laying, has excellent optical fiber insertion properties, and is easy to install at the time of assembling hollow pipes or laying cables. It is excellent. Moreover, it is stable for a long period of time even when laid outdoors in an exposed state. Further, since no tensile member is used in the cable, the outer diameter of the cable can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an example of a cable according to the present invention, which is a single-pipe optical fiber cable including only one hollow pipe.
FIG. 2 is a cross-sectional view of another example of the cable of the present invention, which is a pipe-aggregated optical fiber cable using a plurality of hollow pipes.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Single-pipe type optical fiber cable 2 Hollow pipe a Pipe inner diameter b Pipe outer diameter 3 Optical fiber unit 4 Optical fiber unit coating layer 5 Optical fiber core wire 6 Pipe aggregate type optical fiber cable 7 Presser winding 8 Cable coating layer

Claims (3)

An optical fiber cable comprising at least one hollow pipe into which an optical fiber is inserted, wherein the hollow pipe into which the optical fiber is inserted is a thermoplastic resin having a cross-linked structure. The optical fiber cable according to claim 1, wherein the thermoplastic resin having a crosslinked structure has a degree of crosslinking of 30% or more and 80% or less. The optical fiber cable according to claim 1, wherein the optical fiber cable does not use a tensile member as a constituent member.

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