JP2005107441A - Optical fiber cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber cable having a tensile strength nature and flexural rigidity required for thin diameter optical fiber cable and of which a tensile body is not fractured. <P>SOLUTION: In the optical fiber cable 1, an optical fiber 3 and an organic high tension fiber bunch 4 are covered by low-density polyethylene jacket 9 by batch and a polyethylene covering layer 5 with high degree of elasticity in comparison with that of the jacket 9 is provided around the high tension fiber bunch 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical fiber cable, and more particularly to an optical fiber cable in which an optical fiber and a high-tensile fiber bundle are covered and integrated with a jacket.

In recent years, as the demand for optical communication systems increases, an optical fiber cable as an optical transmission line is often used. As an optical fiber cable used for applications such as FTTH (Fiber To The Home), it is distributed to each one or a plurality of optical fibers from a multi-core optical fiber cable laid over a utility pole etc. The drop cable (for example, refer patent documents 1-3) pulled down to a person's house can be mentioned. An example of an optical fiber cable used as the drop cable is shown in FIG.
As shown in FIG. 4, the conventional optical fiber cable 100 has a configuration in which a main body portion 107 and a messenger wire portion 108 are connected by a neck portion 105.

  The main body 107 is formed by coating a single optical fiber 101 disposed substantially at the center and two strength members 102 with a resin 103. That is, the resin 103 constitutes the outer cover of the main body 107. The two strength members 102 are juxtaposed in the same plane as the optical fiber 101, and the optical fiber 101 is disposed between the two strength members 102.

  As the optical fiber 101 used here, an optical fiber 101 having a structure in which an outer periphery of a double-structured glass body composed of a core and a clad is coated with an ultraviolet curable resin and having an outer diameter of 0.25 mm can be exemplified. . For example, a single mode optical fiber or a multimode optical fiber can be applied to the glass optical fiber. Some of the ultraviolet curable resins are provided with a colored layer on the outer periphery.

The strength member 102 is made of steel, glass fiber reinforced plastic (glass FRP), or the like, and has a circular outer shape in cross section. The glass FRP is generally formed by impregnating a high-strength fiber assembled with a matrix resin and then heating and curing the matrix resin.
Since the optical fiber 101 and the tensile body 102 are collectively covered, the tensile body 102 receives an external force such as a tensile force applied to the optical fiber cable 100 and protects the optical fiber 101 from the external force.

  Further, two notches 104 cut out toward the optical fiber 101 are provided on the outer periphery of the main body 107. The notch 104 is for facilitating the removal of the optical fiber 101, and the removal is performed by cutting the resin 103 between the notches 104 using two notches 104 and tearing the resin 103. .

The messenger wire portion 108 is for securing strength for supporting the optical fiber cable 100 in an aerial manner, and a steel support wire 106 is covered with a resin 103.
The neck 105 is made of the same resin material as that of the main body 107 and the messenger wire 108. For example, the main body 107 and the messenger wire 108 are integrally formed of thermoplastic resin.

  Here, the optical fiber cable 100 having the single optical fiber 101 is illustrated here. However, the conventional drop cable has a plurality of optical fibers or an optical fiber tape core in which a plurality of optical fibers are taped. Some have

In addition, drop-type optical fiber cables, when laid in a state where they are drawn indoors from the outside, are replaced with non-inductive steel wires instead of inductive steel wires so that the induced current generated by lightning strikes is not transmitted indoors. Already used is a known glass FRP used as a tensile body.
For example, Patent Document 1 discloses using glass FRP, polyester (PET), aramid fiber, or the like as a tensile body of an optical fiber cable.

  Further, when the optical fiber cable 100 shown in FIG. 4 is drawn into the building from an aerial space, the messenger wire portion 108 for supporting the aerial space becomes unnecessary, so the neck portion 105 is torn and the main body portion 107 and the messenger wire portion 108 is divided. And as shown in FIG. 5, the indoor type optical fiber cable 100a comprised only by the main-body part 107 is wired in a building.

JP 2002-365499 A Japanese Patent Laid-Open No. 2000-171474 JP 2002-328276 A

  By the way, when a glass FRP in which glass fibers are integrated with a matrix resin is used as a tensile body of the above-described thin optical fiber cable, the optical fiber cable is bent with a bending diameter smaller than the allowable bending diameter. The glass FRP may break and break. If the glass FRP is broken, not only the tensile strength of the broken portion is lowered, but also the optical fiber cable is easily bent at a small angle, and the internal optical fiber may be broken.

  Therefore, when laying the optical fiber cable or when the user handles the laid optical fiber cable, it is necessary to be careful not to bend the optical fiber cable below the allowable bending diameter. It was in the situation that cannot be obtained.

  In addition, when an aramid fiber is used as a tensile body of the optical fiber cable as described above, it does not break even if it is bent. Bending rigidity is difficult to obtain. For this reason, it is necessary to increase the bending rigidity of other components of the optical fiber cable. In this case, the optical fiber cable cannot be put into practical use due to problems such as an increase in size. It can be aggravated.

  In addition, when PET is used as the tensile body of the optical fiber cable as described above, it is bent without breaking even if it is bent, but its elastic modulus is about 2000 to 3000 MPa, and has tensile strength. Low. Therefore, when PET is used as a tensile strength body, a cross-sectional area of 20 times or more of glass FRP, aramid fiber, or the like is required, and a practical optical fiber cable is difficult to obtain.

  An object of the present invention is to provide an optical fiber cable that has tensile strength and bending rigidity necessary for a small-diameter optical fiber cable and that does not break the tensile body.

The optical fiber cable according to the present invention that can achieve the above-mentioned object is an optical fiber cable in which an optical fiber and an organic high-tensile fiber bundle are collectively covered with a plastic resin jacket, Around the high-tensile fiber bundle, at least one coating layer of a plastic resin having a higher elastic modulus than that of the jacket is provided.
Here, the high-tensile fiber bundle has a function as a tensile body of the optical fiber cable, and is a bundle of a plurality of organic high-tensile fibers. A plurality of optical fibers and high-tensile fiber bundles may be provided.

  In the optical fiber cable of the present invention, the coating layer is preferably composed of a plurality of layers.

  In the optical fiber cable of the present invention, the high-tensile fiber bundle is preferably integrated with a matrix resin. More preferably, the high-tensile fiber bundle is obtained by impregnating the aggregated high-tensile fibers with a matrix resin, and then heating and curing the matrix resin to integrate them.

  In the optical fiber cable of the present invention, it is preferable that the jacket and the coating layer are the same type of plastic resin.

  In the optical fiber cable of the present invention, it is preferable that the jacket and the coating layer be a thermoplastic resin.

  In the optical fiber cable of the present invention, it is preferable that the jacket and the coating layer are polyolefin resins.

  In the optical fiber cable of the present invention, the jacket is preferably low-density polyethylene, and the coating layer is preferably high-density polyethylene or linear polyethylene.

  In the optical fiber cable of the present invention, the optical fiber has a mode field diameter of 9.0 μm or less as defined by Petermann-I at a wavelength of 1.3 μm and a screening level of 1.2% or more. It is preferable that the optical fiber has undergone a tensile strength test.

  In the optical fiber cable of the present invention, it is preferable that a support wire for supporting the optical fiber cable in an aerial manner is provided.

  Since the optical fiber cable of the present invention uses an organic high-strength fiber bundle as a strength member, it does not break even when bent, and the high-tensile fiber bundle is formed with a coating layer having a higher elastic modulus than the jacket. The bending rigidity is improved by covering. Therefore, according to the present invention, it is possible to provide an optical fiber cable that has tensile strength and bending rigidity necessary for a small-diameter optical fiber cable and that does not break the tensile body.

Hereinafter, an example of an embodiment of an optical fiber cable according to the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of an optical fiber cable according to the present invention, which is an indoor type optical fiber cable.
As shown in FIG. 1, the optical fiber cable 1 of the present embodiment includes a single optical fiber 3 and two high-tensile fiber bundles 4 arranged substantially at the center in a lump by a plastic resin jacket 9. It is what is covered. The two high-tensile fiber bundles 4 are arranged in the same plane as the optical fiber 3, and the optical fiber 3 is disposed between the two high-tensile fiber bundles 4. The jacket 9 is provided with two notches 10 that facilitate the removal of the optical fiber 3.

  The optical fiber 3 used here will be described. The optical fiber 3 has a structure in which a glass fiber having a core and a clad and the outer periphery of the glass fiber are covered with a protective coating layer. For example, a single mode optical fiber or a multimode optical fiber can be applied to the glass fiber. Moreover, a thin film-like carbon layer may be coated around the glass fiber. The protective coating layer may consist of a plurality of layers. Further, a colored layer having a thickness of about 1 μm to 10 μm may be formed on the outer periphery of the protective coating layer. The outer diameter dimension of the optical fiber 3 is, for example, 0.25 mm.

  As a glass fiber applicable to the present invention, a glass fiber having any refractive index distribution, such as a glass fiber composed of a core and a clad of a plurality of layers, can be applied. In addition, the optical fiber cable 1 may be provided with a plurality of optical fibers, or may be provided with an optical fiber ribbon that is a tape of the plurality of optical fibers.

Moreover, it is preferable that the optical fiber 3 conforms to G652 defined by ITU-T (International Telecommunication Union-Telecommunication standardization sector).
Further, the optical fiber 3 has a mode field diameter (MFD) according to the definition of Petermann-I at a wavelength of 1.3 μm so as not to cause an increase in transmission loss that would be a practical problem even when bent to a radius of about 15 mm. Diameter) is preferably 9.0 μm or less. Furthermore, if the mode field diameter at a wavelength of 1.55 μm is 8.0 μm or less, microbend loss and bending loss (macrobend loss) due to lateral pressure can be reduced, and the allowable bending radius is reduced to about 7.5 mm. Can do. Therefore, it is possible to suppress an increase in transmission loss due to an external force or bending that is applied when the optical fiber cable 1 is handled.

  Further, as the optical fiber 3, it is desirable to use an optical fiber that has undergone a tensile strength test with a screening level of 1.2% or more. Screening here is a guarantee of the strength of the optical fiber to be commercialized, and is a tensile strength test by providing a tension application section in the travel line before winding the drawn optical fiber around a bobbin or the like. is there. That is, by setting the tension applied in the tension application section to an arbitrary value, the elongation percentage (%) of the optical fiber can be set as the screening level. Thereby, a low-strength optical fiber that does not satisfy a desired screening level can be broken, and only a portion that does not break can be wound on a bobbin or the like to obtain a product.

  An optical fiber satisfying such a screening level of 1.2% or more has a very low cumulative fracture probability against the tension applied in the normal installation environment of the optical fiber cable 1. Therefore, it is not necessary to strengthen the tensile strength (tensile strength) of the optical fiber cable 1 more than necessary.

  As described above, the optical fiber 3 used in the optical fiber cable 1 of the present embodiment can exhibit good optical transmission characteristics even when a lateral pressure, bending, tension, or the like is applied. Therefore, the optical fiber cable 1 can effectively obtain a high-quality optical transmission line with high reliability.

As an organic high-tensile fiber used for the high-tensile fiber bundle 4, an aramid fiber can be mentioned as a suitable example.
Further, the high-tensile fiber bundle 4 may be a so-called FRP in which the matrix resin is impregnated and then the matrix resin is thermally cured to be integrated.
As the matrix resin, unsaturated polyester resin, vinyl ester, epoxy, acrylic, or the like can be used.

When the high-tensile fiber bundle 4 is formed as FRP, not only the tensile strength and bending rigidity can be improved, but also the anti-shrinkage property is remarkably improved. Therefore, shrinkage of the jacket 9 integrally covering the high-tensile fiber bundle 4 can be prevented, and the optical fiber cable 1 can be prevented from shrinking in the longitudinal direction due to a change with time.
In this embodiment, glass fiber is not used as the high-strength fiber constituting the FRP, and an organic material is used. Therefore, even when the optical fiber cable is bent and bent with a small radius of curvature, the fiber can be bent. However, it can be prevented from being broken and broken like glass FRP.

  In the present embodiment, a coating layer 5 made of a plastic resin having a higher elastic modulus than that of the plastic resin constituting the outer cover 9 is provided around the high-tensile fiber bundle 4 (including those made into FRP). ing. That is, by providing the high-elastic modulus coating layer 5 integrally with the high-tensile fiber bundle 4, the high-tensile fiber bundle 4 and the coating layer 5 have a function as the tensile body 8, and the tensile body is made organic. The optical fiber cable 1 can be provided with a bending rigidity of a size that cannot be obtained when only the high-strength high-strength fiber bundle 4 is used. Thereby, the bending rigidity required for a small-diameter optical fiber cable such as an indoor optical fiber cable can be obtained.

In addition, by providing the coating layer 5, even when the high-tensile fiber bundle 4 made into FRP is bent, it absorbs and softens the outward impact force generated by the buckling, Damage to the optical fiber 3 can be prevented.
Here, the term “buckling” means that plastic deformation occurs when bent and the folds remain.

Here, the plastic resin suitably used as the outer jacket 9 and the coating layer 5 will be described.
The jacket 9 and the coating layer 5 are preferably made of the same type of plastic resin. By using the same kind of plastic resin for the jacket 9 and the coating layer 5, high adhesion between them can be obtained. By increasing the adhesion between the jacket 9 and the coating layer 5, that is, the adhesion between the jacket 9 and the tensile body 8, the expansion and contraction of the jacket 9 can be effectively prevented.

  Here, it can be illustrated that the same type is preferably a polyolefin resin. Examples of the polyolefin-based resin include polyethylene and polypropylene, and the same type of combination may be polyethylene and polyethylene, polypropylene and polypropylene, or polyethylene and polypropylene. By using a polyolefin-based resin, corrosion resistance, water resistance, and workability are good, and since there is little deterioration against ultraviolet rays, an inexpensive optical fiber cable that can be used outdoors can be obtained.

In the present embodiment, it is preferable that the jacket 9 and the coating layer 5 be a combination of polyethylenes.
Polyethylene can be classified according to the difference in density, and is roughly classified into low density polyethylene (LDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE). Further, the low density polyethylene can be further classified into a high pressure method low density polyethylene (HPLDPE) and a linear low density polyethylene (LLDPE) having a density range different from that of the high pressure method low density polyethylene.
Table 1 shows typical numerical examples of the density (g / cm ³ ) and the tensile modulus (MPa) of the resin suitably used in the present embodiment.

As the plastic resin constituting the outer cover 9, low density polyethylene (LDPE) which contains EVA or EEA and easily imparts flame retardancy is preferable.
In addition, as described above, the coating layer 5 is preferably made of linear low-density polyethylene or high-density polyethylene from the viewpoint of increasing the elastic modulus as compared with the jacket 9.

Next, another embodiment of the optical fiber cable according to the present invention will be described.
As shown in FIG. 2, the optical fiber cable 20 of the present embodiment is an optical fiber cable similar to the above-described optical fiber cable 1 (see FIG. 1), and only the configuration of the strength member 8a is different.

  The strength member 8a used in the present embodiment includes the high-tensile fiber bundle 4 and the coating layer 5 coated around the high-strength fiber bundle 4 in the embodiment described with reference to FIG. In the present embodiment, a coating layer 6 having a higher elastic modulus than the outer cover 9 is further provided around the periphery. That is, the coating layer 7 which forms a part of the strength member 8a is formed by the two coating layers 5 and 6.

Here, the coating layer 6 may be of any type as long as it is a plastic resin having a higher elastic modulus than the outer cover 9. For example, like the coating layer 5, it is preferable to use the polyolefin resin. Usually, the bending rigidity of the optical fiber cable 1 can be improved more effectively by using a resin having a higher elastic modulus than that of the coating layer 5 for the coating layer 6 located outside.
Moreover, in this embodiment, the coating layer 7 is comprised by the two layers which consist of the coating layers 5 and 6. However, in this invention, how many layers may be sufficient.

Thus, the bending rigidity of the optical fiber cable 1 can be further improved by providing a plurality of coating layers 7.
In addition, as shown in FIG. 1, even when there is only one coating layer, it is possible to obtain a desired bending rigidity by appropriately selecting the resin and adjusting the thickness.

Further, the optical fiber cable of the present invention is not limited to the above embodiment.
For example, as shown in FIG. 3, a drop-type optical fiber cable in which the configuration of the optical fiber cable 1 shown in FIG. This optical fiber cable 1 a has a configuration in which a main body 2 and a messenger wire 11 are connected by a neck 13. The messenger wire portion 11 and the neck portion 13 can have the same configuration as a conventional optical fiber cable (see FIG. 4). That is, the support wire 12 provided in the messenger wire portion 11 ensures the strength for supporting the optical fiber cable 1a in an aerial manner.
In addition to the illustrated optical fiber cable, various forms such as a circular outer shape can be used.

Next, examples of the optical fiber cable according to the present invention will be described.
In the form of the optical fiber cable as shown in FIG. 1 and FIG. 2, organic high-tensile fibers (aramid fibers) as FRP (Examples 1 to 3) and inorganic high-tensile fibers as high-tensile fiber bundles (Glass fiber) made of FRP (Examples 4 to 6) was prepared, and among them, those provided with the above-described coating layers 5 and 6 and those not provided were prepared.

As a configuration common to each optical fiber cable, the optical fiber 3 is a glass optical fiber provided with a protective coating layer of an ultraviolet curable resin, and has an outer diameter of 0.25 mm.
The outer dimensions of the jacket 9 are 4 mm in the longitudinal direction and 2 mm in the lateral direction of FIG. 1 or 2, and the material is low density polyethylene (LDPE) imparted with flame retardancy.
The high-tensile fiber bundle 4 uses vinyl ester as the FRP-made matrix resin, and its outer diameter is 0.5 mm.

When the coating layer of the high-tensile fiber bundle 4 is only one coating layer 5 as shown in FIG. 1 (Examples 2 and 5), the material of the coating layer 5 is linear low density polyethylene (LLDPE), Its outer diameter is 1.5 mm.
Moreover, when the coating layer of the high-tensile fiber bundle 4 is two coating layers 5 and 6 as shown in FIG. 2 (Examples 3 and 6), the material of the coating layer 5 is linear low density polyethylene (LLDPE). And its outer diameter is 0.8 mm. The material of the covering layer 6 is high density polyethylene (HDPE), and the outer diameter thereof is 1.5 mm.

Then, the bending rigidity when bending the optical fiber cable in the left-right direction in FIG. 1 or FIG. 2 and the damage state of the tensile body and the optical fiber due to the bending of the cable were examined. In addition, the test at the time of bending an optical fiber cable was performed based on the method E17C among the hardness (bending rigidity) tests of the optical fiber cable prescribed | regulated by JISC6851.
The results obtained from such tests are shown in Table 2.

Among the results shown in Table 2, first, those using aramid fibers as high-tensile fibers (Examples 1 to 3) are compared.
When the coating layer 5 (Example 2) and the coating layer 5 and 6 (Example 3) are compared with those without the coating layers 5 and 6 (Example 1) as a reference, the coating It can be seen that the bending rigidity is increased by providing the layer. Further, the tensile strength member when the cable was bent and pressed with a force of 500 gf showed no breakage in 10 samples. Similarly, in the case where the optical fiber when the cable is bent has no coating layer (Example 1), one of the 10 samples was disconnected, but at least one coating layer was provided. In (Examples 2 and 3), no disconnection occurred.

Next, a comparison is made of those using glass fibers as high-tensile fibers (Examples 4 to 6).
When the coating layer 5 (Example 5) and the coating layer 5 and 6 (Example 6) are compared with the coating layer 5 and 6 (Example 4) as a reference, the coating layer 5 and 6 are not coated. The bending rigidity can be improved by providing the layer. However, in any example, it is not possible to prevent breakage of the strength member and disconnection of the optical fiber.

  From the embodiments shown above, in the optical fiber cables of Examples 2 and 3 having the structure according to the present invention, an organic high-strength fiber is used as a tensile strength body, and a coating layer having a higher elastic modulus than the jacket around the outer periphery Therefore, it was found that the bending rigidity can be improved, and the breakage of the strength member and the disconnection of the optical fiber can be prevented.

It is sectional drawing which shows one Embodiment of the optical fiber cable which concerns on this invention. It is an optical fiber cable concerning the present invention, and is a sectional view showing one embodiment provided with a plurality of coating layers. It is an optical fiber cable concerning the present invention, and is a sectional view showing one embodiment provided with a support line. It is sectional drawing which shows an example of the conventional drop type optical fiber cable. It is sectional drawing which shows an example of the conventional indoor type optical fiber cable.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Optical fiber cable 2 Main body part 3 Optical fiber 4 High-tensile fiber bundle 5, 6, 7 Cover layer 8, 8a Strength member 9 Outer cover 10 Notch 11 Messenger wire part 12 Support line 13 Neck part

Claims (9)

An optical fiber cable in which an optical fiber and an organic high-tensile fiber bundle are collectively covered with a plastic resin jacket,
An optical fiber cable characterized in that at least one coating layer of a plastic resin having a higher elastic modulus than that of the jacket is provided around the high-tensile fiber bundle. The optical fiber cable according to claim 1,
The said coating layer is comprised from the multiple layer, The optical fiber cable characterized by the above-mentioned. The optical fiber cable according to claim 1 or 2,
The optical fiber cable, wherein the high-tensile fiber bundle is integrated by a matrix resin. The optical fiber cable according to any one of claims 1 to 3,
The outer jacket and the covering layer are made of the same type of plastic resin. An optical fiber cable according to claim 4,
The outer jacket and the covering layer are made of a thermoplastic resin. An optical fiber cable according to claim 4 or 5,
The outer jacket and the coating layer are made of polyolefin resin. The optical fiber cable according to any one of claims 1 to 6,
The jacket is made of low-density polyethylene, and the coating layer is made of high-density polyethylene or linear polyethylene. The optical fiber cable according to any one of claims 1 to 7,
The optical fiber has a mode field diameter of 9.0 μm or less as defined by Petermann-I at a wavelength of 1.3 μm, and has undergone a tensile strength test with a screening level of 1.2% or more. An optical fiber cable characterized by being. The optical fiber cable according to any one of claims 1 to 8,
An optical fiber cable comprising a support wire for supporting the optical fiber cable in an aerial space.

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