JPH07151945A - Optical fiber cable - Google Patents

Abstract

PURPOSE:To make inexpensive laying possible and to the continuous detection of positions possible where landslides, etc., break out with high accuracy by coating a coated optical fiber by using a thermoplastic resin constituted to break down when a bending stress is applied thereon. CONSTITUTION:The circumference of an optical fiber cord A composed by aggregating many pieces of 'Kevlar (R)' around the coated optical fiber 1 to reinforce this coated fiber and coating the circumference thereof with a vinyl sheath 3 is coated with a foamed polyethylene(PE) resin coating 5 enclosing many thermally expandable hollow spheres 4. The foamed PE resin coating 5 of such optical fiber cable breaks down and the coated optical fiber 1 buckles when the bending stress is generated in this cable in accordance with the sand and soil pressure by the landslide. An increase in the transmission loss of the buckled part is then resulted. This increase in the transmission loss is read by a measuring instrument, such as OTDR, by which the position of the landslide is specified. The foamed PE resin coating 5 preferably breaks down when the bending stress of >=5% is applied thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber cable, and more particularly to an optical fiber cable whose main purpose is to detect landslides and avalanches.

[0002]

2. Description of the Related Art Conventionally, a large number of sensors are installed on the ground surface or the like to detect the occurrence of landslides and avalanches. Also, as a means other than the above, laying a wire rope etc.,
There is a method to detect the occurrence of landslides based on changes in the tension of the wire rope and wire breakage.

[0003]

In the method of installing a large number of sensors on the ground surface, etc., there is a problem that not only a large amount of cost is required, but also continuous position detection corresponding to the occurrence of a landslide or the like cannot be performed. there were. In addition, in the method of laying wire ropes and the like, there is a problem that it is difficult to specify the location where landslides occur.

The present invention aims to provide a novel optical fiber cable which can be laid at low cost and is capable of continuously detecting the position of occurrence of a landslide or the like with high accuracy, and thus the above-mentioned conventional optical fiber cable. The problem of is solved.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to an optical fiber cable in which an optical fiber core wire is coated with a thermoplastic resin, and the resin coating is a resin configured to break when bending strain is applied. The present invention relates to an optical fiber cable including a coating. And, it is desirable to use a resin coating that breaks when a bending strain of 5% or more is applied.

[0006] Specifically, a large number of Kevlar 2 are gathered around the optical fiber core wire 1 to reinforce it, and the periphery of the optical fiber cord A whose outer circumference is covered with a vinyl sheath 3 is provided with a thermally expandable hollow sphere 4. Including foam polyethylene resin coating 5
It is configured to be covered with. The metal pipe 7 may be used instead of the vinyl sheath 3 described above.

[0007]

If the optical fiber cable according to the present invention is laid in a place where landslide or the like is likely to occur, when the landslide occurs, bending strain occurs in the cable due to the earth and sand pressure and the polyethylene foam resin coating 5 is formed. It breaks and the optical fiber core wire 1 which is the cable core buckles. Therefore, the transmission loss of the buckling portion is significantly increased, and the position of landslide or the like is specified by reading this with a measuring instrument such as OTDR.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention. In the figure, A is an optical fiber cord,
A large number of Kevlar 2 are gathered around the optical fiber core wire 1 to reinforce it, and the circumference thereof is covered with a vinyl sheath 3. An optical fiber cable is constructed by covering the periphery of the optical fiber cord A with a foamed polyethylene resin coating 5 including a large number of thermally expandable hollow spheres 4.

That is, the above optical fiber cable is
It is laid in a place where landslides etc. are likely to occur. When landslides occur, if bending strain occurs in the cable due to sediment pressure, the foamed polyethylene resin coating 5 breaks and the optical fiber core wire that is the cable core. 1 is buckled, and the transmission loss of the buckled portion is significantly increased.

FIG. 2 shows a second embodiment of the present invention. This is the optical fiber cord A described in the first embodiment, that is, the optical fiber cord A in which a large number of Kevlar 2 are gathered around the optical fiber core wire 1 to reinforce, and the vinyl sheath 3 is coated, and above this. An optical fiber cable is constructed by covering the support wires 6 positioned in parallel with a foamed polyethylene resin coating 5a containing a large number of heat-expandable hollow spheres 4a in a gourd shape.

In the second embodiment described above, when the cable is laid in a place where a landslide or the like is likely to occur, the support wire 6 is laid and tensioned in order to prevent the foaming polyethylene resin coating 5a from being broken by the laying tension. Support line 6 later
The occurrence of a landslide or the like can be detected by separating the support wire 6 or cutting the support wire 6 at regular intervals. The detection action is performed based on the reading of the transmission loss of the buckling portion based on the buckling of the optical fiber core wire 1, as in the case of the first embodiment.

FIG. 3 shows a third embodiment of the present invention. This is an optical fiber core wire in which a metal pipe 7 is used instead of the vinyl sheath 3 in the optical fiber cable described in the first embodiment, and a large number of Kevlar 2 are gathered around the metal pipe 7 and reinforced. 1 is configured to be stored.

By the way, the gist of the present invention resides in the use of a resin obtained by heat-expanding a low-density polyethylene resin containing thermally expandable hollow spheres as a coating material for the optical fiber core wire. As a result, when the cable is subjected to bending strain, the resin is broken, and local strain is generated in the optical fiber core wire, which significantly reduces the transmission loss.
The position of a landslide or the like can be specified by reading with a measuring instrument such as R.

The low-density polyethylene resin containing the heat-expandable hollow spheres mentioned above is heated and foamed, preferably the low-density polyethylene resin containing 5% or more of the heat-expandable hollow spheres is heat-expanded. Is preferred. As a result, when the cable is subjected to bending strain of 5% or more, the above-mentioned breakage will occur stably. The reason is that if the compounding ratio of the heat-expandable hollow spheres is less than 5%, the brittleness of the resin coating decreases, so the coating will not break unless subjected to a bending strain of 10%, and therefore the external force detection sensitivity Is significantly reduced.

When a blending ratio of the heat-expandable hollow spheres is set so that the resin coating is broken even when subjected to a bending strain of less than 5%, even when slight bending is applied. Since the resin coating is broken, the cable itself is difficult to manufacture and lay, which causes an adverse effect.

[0016]

INDUSTRIAL APPLICABILITY The present invention is an optical fiber cable in which an optical fiber core wire is coated with a thermoplastic resin, and the resin coating is configured to break when bending strain is applied. Since such an optical fiber cable is installed in a place where a landslide or the like is likely to occur, the place where the landslide or the like occurs can be continuously monitored and the occurrence can be reliably detected. Further, as compared with the conventional one in which a large number of sensors are installed, the installation work cost is significantly reduced.

Further, as described in claim 2, by using a resin coating that breaks when a bending strain of 5% or more is applied, it has been described above when the cable is subjected to bending strain. As described above, the fracture occurs stably, and therefore, the occurrence of landslide and the like can be detected extremely accurately and surely.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a transverse sectional view showing a second embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

 A Optical fiber cord 1 Optical fiber core wire 2 Kevlar 3 Vinyl sheath 4 Thermally expandable hollow sphere 4a Thermally expandable hollow sphere 5 Foam polyethylene resin coating 5a Foam polyethylene resin coating 6 Support wire 7 Metal pipe

[Procedure amendment]

[Submission date] January 19, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

OPTICAL FIBER CABLE

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber cable, and more particularly to an optical fiber cable whose main purpose is to detect landslides and avalanches.

[0002]

2. Description of the Related Art Conventionally, a large number of sensors are installed on the ground surface or the like to detect the occurrence of landslides and avalanches.

As a means other than the above, there is a method in which a wire rope or the like is laid and the occurrence of landslide or the like is detected based on a change in tension of the wire rope or a wire break.

[0004]

In the method of installing a large number of sensors on the ground surface, etc., there is a problem that not only a large amount of cost is required, but also continuous position detection corresponding to the occurrence of a landslide or the like cannot be performed. there were.

Further, in the method of laying wire ropes and the like, there is a problem that it is difficult to specify the position where the landslide occurs.

The present invention aims to provide a novel optical fiber cable which can be laid at a low cost and is capable of continuously detecting the position of occurrence of a landslide or the like with high accuracy. The problem of is solved.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to an optical fiber cable in which an optical fiber core wire is coated with a thermoplastic resin, and the resin coating is a resin configured to break when bending strain is applied. The present invention relates to an optical fiber cable including a coating. And, it is desirable to use a resin coating that breaks when a bending strain of 5% or more is applied.

Specifically, a large number of Kevlar 2 are gathered around the optical fiber core wire 1 to reinforce it and the circumference of the optical fiber cord A whose outer circumference is covered with a vinyl sheath 3 is provided with a thermally expandable hollow sphere 4. It encompasses onset foam polyethylene resin coating 5
It is configured to be covered with. The metal pipe 7 may be used instead of the vinyl sheath 3 described above.

[0009]

Once you have laying optical fiber cables to likely place landslides or the like occurs according to the present invention, when the landslides occurred, the bending strain is generated in the cable based on the soil pressure, foamed polyethylene resin coating 5 Breaks, and the optical fiber core wire 1, which is the cable core, buckles. Therefore, the transmission loss of the buckling portion is significantly increased, and the position of landslide or the like is specified by reading this with a measuring instrument such as OTDR.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention. In the figure, A is an optical fiber cord,
A large number of Kevlar 2 are gathered around the optical fiber core wire 1 to reinforce it, and the circumference thereof is covered with a vinyl sheath 3. Then, the periphery of the optical fiber cord A, depending on the covering a number of thermally expandable hollow spheres 4 encompasses onset foam polyethylene <br/> down resin coating 5, constitute the optical fiber cable.

That is, the above-mentioned optical fiber cable is
Leave laying in place like is likely to occur landslides, when landslides occur, if the strain bending the cable based on the soil pressure occurs, then broken foamed polyethylene resin coating 5, the optical fiber center is a cable heart The wire 1 buckles, and the transmission loss of the buckling portion is significantly increased. FIG. 2 shows a second embodiment of the present invention. This is the optical fiber cord A described in the first embodiment, that is,
Optical fiber cord A in which a large number of Kevlar 2 are gathered around the optical fiber core wire 1 for reinforcement and a vinyl sheath 3 is covered.
When, a support wire 6 is located in parallel form over this, depending on the coating gourd shape a number of thermally expandable hollow spheres 4a in encompasses onset foam coated with a polyethylene resin 5a, the optical fiber cable It is composed.

[0012] The second embodiment described above, upon laying of the cable for likely locations landslides or the like occurs, and laying under tension to the support wire 6 in order to prevent breakage of the foamed polyethylene resin coating 5a by laying tension, Support line 6 after installation
The occurrence of a landslide or the like can be detected by separating the support wire 6 or cutting the support wire 6 at regular intervals. The detection action is performed based on the reading of the transmission loss of the buckling portion based on the buckling of the optical fiber core wire 1, as in the case of the first embodiment.

FIG. 3 shows a third embodiment of the present invention. This is an optical fiber core wire in which a metal pipe 7 is used instead of the vinyl sheath 3 in the optical fiber cable described in the first embodiment, and a large number of Kevlar 2 are gathered around the metal pipe 7 and reinforced. 1 is configured to be stored.

By the way, that the gist of the present invention, as a coating material for optical fibers, in that a resin obtained by heating onset foam low density polyethylene resin containing thermal expansible hollow spheres. As a result, when the cable is subjected to bending strain, the resin is broken, and local strain is generated in the optical fiber core wire, which significantly reduces the transmission loss.
The position of a landslide or the like can be specified by reading with a measuring instrument such as R.

[0015] Note that the low-density polyethylene resins including the thermal expansive hollow spheres are heated onset foam is a resin obtained, thereby preferably heated onset foam low density polyethylene resin containing thermal expansible hollow spheres 5% or more It is desirable to use the above resin. As a result, when the cable is subjected to bending strain of 5% or more, the above-mentioned breakage will occur stably. The reason is that if the compounding ratio of the heat-expandable hollow spheres is less than 5%, the brittleness of the resin coating decreases, so the coating will not break unless subjected to a bending strain of 10%, and therefore the external force detection sensitivity Is significantly reduced.

When the above-mentioned resin coating has a blending ratio of the heat-expandable hollow spheres such that it breaks even when subjected to a bending strain of less than 5%, even when slight bending is applied. Since the resin coating is broken, the cable itself is difficult to manufacture and lay, which causes an adverse effect.

[0017]

INDUSTRIAL APPLICABILITY The present invention is an optical fiber cable in which an optical fiber core wire is coated with a thermoplastic resin, and the resin coating is configured to break when bending strain is applied. Since such an optical fiber cable is installed in a place where a landslide or the like is likely to occur, the place where the landslide or the like occurs can be continuously monitored and the occurrence can be reliably detected. Further, as compared with the conventional one in which a large number of sensors are installed, the installation work cost is significantly reduced.

Further, as described in claim 2, by using a resin coating that breaks when a bending strain of 5% or more is applied, the above-mentioned description is given when the cable is subjected to bending strain. As described above, the fracture occurs stably, and therefore, the occurrence of landslide and the like can be detected extremely accurately and surely.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a transverse sectional view showing a second embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a third embodiment of the present invention.

[Description of symbols] A optical fiber cord 1 optical fiber 2 Kevlar 3 Vinyl sheath 4 thermally expanding hollow spheres 4a thermally expandable hollow spheres 5 shot foaming a polyethylene resin coated 5a onset foam polyethylene resin-coated 6 support wire 7 metal pipe

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure 3]

[Document name to be corrected] Drawing

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[Correction method] Change

[Correction content]

[Fig. 2]

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeru Iwata 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki Hidaka Plant, Hitachi Cable, Ltd. (72) Inventor Yoshio Kawamata 5 Hidaka-cho, Hitachi-shi, Ibaraki 1-1-1 Hitachi Cable Co., Ltd. Hidaka Factory

Claims (4)

[Claims] 1. An optical fiber cable in which an optical fiber core wire is coated with a thermoplastic resin, wherein the resin coating is:
An optical fiber cable comprising a resin coating configured to break when bending strain is applied. 2. The optical fiber cable according to claim 1, wherein the optical fiber cable comprises a resin coating which breaks when a bending strain of 5% or more is applied. 3. A Kevlar (2) around an optical fiber core (1)
Around the optical fiber cord (A) formed by collecting and reinforcing a large number of vinyl sheaths and covering the outer circumference with a vinyl sheath (3),
An optical fiber cable constructed so as to be covered with a foamed polyethylene resin coating (5) containing a thermally expandable hollow sphere (4). 4. A kevlar (2) around an optical fiber core (1).
A foam polyethylene resin coating (5) including a thermally expandable hollow sphere (4) around the optical fiber cord (A) formed by accumulating and reinforcing a large number of metal fibers in a metal pipe (7).
An optical fiber cable configured to be covered with.