JPH0573797A - Linear external pressure sensor and cable using this sensor - Google Patents

Abstract

PURPOSE:To detect the position of the occurrence of abnormality by constituting a linear external pressure sensor of a linear body arranged in the center, a coated optical fiber spirally wound around the outside periphery of the linear body, and a protective layer having projecting stripes on the inside surface. CONSTITUTION:With respect to a linear external pressure sensor 21, a coated optical fiber 23 is spirally wound around the outside periphery of a linear body 22 arranged in the center, and its outside periphery is coated with a corrugate pipe 24 as the protective layer. If abnormality occurs to apply an external pressure to the sensor 21, the corrugate pipe 24 is deformed in this position, and projecting stripes on the inside surface are pressed to the coated optical fiber 23. Thus, the coated optical fiber 23 receives the lateral pressure and is bent, and the transmission loss is quickly increased in this position. This transmission loss is monitored in the end part of the coated optical fiber 23 by an OTDR (optical fiber defective point research device) to detect the occurrence and the position of abnormality. This linear external pressure sensor 21 is extended along a cable core 32 to constitute a submarine power cable 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear external pressure sensor using an optical fiber and a cable capable of detecting an accident point using this sensor.

[0002]

2. Description of the Related Art An anchorage of a ship is often caught on a cable laid on the seabed, especially on a strait where the ship frequently travels, which may damage the seabed cable or cause a worst case. In case of, there is an accident such as being disconnected.

Conventionally, various studies have been made to detect the occurrence of such an accident. As one of them, an external pressure sensor 11 as shown in FIG. 14 has been put to practical use. this is,
A pair of insulated wires 12 are twisted together, and a conductive wire strip made of a pair of copper wires along the valleys formed on both sides of the wires.
It is a twist of 13. That is, in this state, the pair of conductive linear bodies 13 are in an insulated state.

If such an external pressure sensor 11 is housed in the submarine cable, a large external pressure is applied to the submarine cable when the anchor of the ship is caught in the laid submarine cable. It is transformed as shown in FIG. That is, the insulating linear body 12 escapes to both sides, and the conductive linear body 13 comes closer to the center and comes into contact. As a result, the pair of conductive linear members 13 are electrically connected at that position,
If this is electrically detected at the end of the submarine cable, it can be detected that the anchor has been caught.

[0005]

Although the conventional sensor can detect that the anchor is caught on the submarine cable, it cannot detect its position. Therefore, there is a problem that it is difficult to identify the ship that caused the accident at a later date. The above is about the detection of an accident in a submarine cable, but damage to the cable due to abnormal external pressure can occur even in an underground cable or an aerial cable, and detection of an accident point in such a case is an important issue. is there.

Further, such an accident point detection is not limited to a cable, and when an abnormality occurrence in a certain section or a certain route is monitored for the purpose of crime prevention or disaster prevention, for example, not only the presence or absence of the abnormality occurrence is detected. If it is possible to detect at which position the abnormality has occurred, it is effective in improving the monitoring accuracy.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a linear external pressure sensor which solves the above-mentioned problems, and has a linear body arranged at the center and a spiral winding on the outer periphery thereof. Alternatively, it is provided with at least one optical fiber core wire provided vertically and a protective layer coated on the outer periphery thereof, and the protective layer is pressed against the inner surface of the optical fiber core wire when the protective layer receives an external pressure. It is characterized in that the optical fiber has a ridge or a protrusion that causes an increase in transmission loss.

The protective layer can take various forms, for example, a corrugated pipe. In addition, a wavy tape wound around the outer periphery of the core material and the optical fiber core and a sheath covered on the outer periphery thereof can be used. It can also be configured with a tape with protrusions wound around it and a sheath coated on the outer periphery thereof.

In the present invention, a wire rod may be used instead of the ridge or protrusion that is pressed against the optical fiber core wire and causes an increase in transmission loss in the optical fiber core wire.
In the case of using a wire rod, a linear member arranged at the center, at least one optical fiber core wire spirally or vertically attached to the outer circumference thereof, and a spiral wire wound around the outer circumference thereof so as to intersect the optical fiber core wire. Alternatively, it is configured to include at least one wire that is vertically provided and a protective layer that is coated on the outer periphery of the wire. Further, in this configuration, it is possible to replace the optical fiber core wire with the wire material so that the wire material is the inner layer side and the optical fiber core wire is the outer layer side.

If the linear external pressure sensor as described above is provided along the core of a cable such as a power cable, a communication cable or a water supply cable, a cable with an external pressure sensor can be constructed.

[0011]

In the linear external pressure sensor of the present invention, when an external force is applied at a certain position in the longitudinal direction, the optical fiber core wire receives a lateral pressure at that position due to the ridges or projections on the inner surface of the protective layer or the intersecting wires. , Bend. For this reason, the transmission loss of the optical fiber core at that position increases rapidly, and if this is monitored by the OTDR (optical fiber fault point search device) at the end of the optical fiber core, the linear external pressure It is possible to detect that an external force is applied to the sensor (abnormality occurrence) and its position (distance from the end of the optical fiber).

If a cable with an external pressure sensor is formed by arranging the linear external pressure sensor along the cable core, if the cable is a submarine cable, for example, if an anchor is caught, the fact and its position are determined. If it is a cable buried in the ground, for example, when abnormal external pressure is applied due to ground subsidence, that and its position can be detected.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 and 2 show an embodiment of the present invention. This linear external pressure sensor 21 has an optical fiber core wire 23 spirally wound around the outer circumference of a linear body 22 arranged at the center, and a corrugated pipe 24 as a protective layer around the outer circumference.
Is coated.

The linear member 22 is usually made of plastic, but may be made of metal. If necessary, an optical cable or the like having a sheath for the optical fiber core for communication may be used.

The optical fiber core wire 23 is a protective coating on the optical fiber, and at least one optical fiber core wire 23 may be used, but a plurality of optical fiber core wires 23 are preferably used in order to improve the detection accuracy. Also, the optical fiber core wire 23 may be wound around one, or may be wound around in a state where a plurality of the optical fibers 23 are assembled. Further, the shape is not limited to a circular cross section, and may be in the form of a tape-shaped optical fiber core wire.

Although the corrugated pipe 24 is made of metal, a plastic coating may be provided on the outer periphery thereof if necessary. The corrugated pipe 24 is preferably formed so that a slight gap is formed between the corrugated pipe 24 and the winding layer of the optical fiber core wire 23.
In this way, the optical fiber core wire 23 is not restrained by the corrugated pipe 24, so that increase in transmission loss due to causes other than the occurrence of an abnormality is unlikely to occur.

In order to detect an abnormality with this linear external pressure sensor 21, the sensor 21 is laid on the route for which abnormality detection is to be performed, and at the end thereof, an OTDR is connected to an optical fiber core wire 23 to generate an optical pulse. Input a signal to constantly monitor. In this state, if external pressure is applied to any part of the linear external pressure sensor 21 (an abnormality occurs), the corrugated pipe 24 is deformed at that position, and the ridges on its inner surface press against the optical fiber core wire 23. Optical fiber core wire
23 thereby receives local lateral pressure and is bent. Therefore, a sudden increase in transmission loss occurs at that position,
The OTDR can detect the occurrence of an abnormality and its position from the reflected wave.

That is, when the linear external pressure sensor 21 receives an external pressure, the optical fiber core wire 23 wound around the linear body 22 locally receives a lateral pressure by the ridge on the inner surface of the corrugated pipe 24, and the small external pressure sensor 21 Since it is bent at the bending diameter, the transmission loss increase appears more clearly at the obstacle position. Therefore, the abnormality can be detected with high detection sensitivity.

The corrugated pipe 24 may be permanently deformed by receiving external pressure, or may be deformed by receiving external pressure and then restored to its original sectional shape when the external pressure is removed. Which one is used depends on the application of the sensor.

FIG. 3 shows another embodiment of the present invention. The linear external pressure sensor 21 has an optical fiber core wire on the outer periphery of the linear body 22.
23 is spirally wound with a plastic cord 25, and a corrugated pipe 24 is coated on the outer periphery thereof. The cord 25 is made of a material that is easily deformed by an external pressure, and its outer diameter is slightly larger than that of the optical fiber core wire 23. Further, the corrugated pipe 24 is formed such that the protrusion on the inner surface thereof is in slight contact with the string 25.

In this way, the optical fiber core wire 23 and the corrugated pipe 24 are not in contact with each other in a normal state, and the ridges on the inner surface of the corrugated pipe 24 press the optical fiber core wire 23 only when an external pressure is applied. It will be. Therefore, the transmission loss of the optical fiber core wire 23 in the normal state is small, and the detection accuracy when an abnormality occurs is high.

FIG. 4 shows still another embodiment of the present invention.
In this linear external pressure sensor 21, an optical fiber core wire 23 is spirally wound around the linear body 22, and a corrugated tape 26 as shown in FIG. The sheath 27 is covered. That is, in this embodiment, the corrugated tape 26 and the plastic sheath 27 serve as a protective layer. However, even with such a configuration, since a large number of ridges are formed on the inner surface of the protective layer, the corrugated pipe is covered. The same action and effect can be obtained.

Although the corrugated tape 26 is a metal tape, a heat-fusible plastic film is preliminarily laminated on the outer surface when wound, and is integrally formed with a plastic sheath 27 which is extrusion coated. It is desirable to make it a so-called laminated sheath structure.

FIG. 6 shows still another embodiment of the present invention.
In this linear external pressure sensor 21, an optical fiber core wire 23 is spirally wound around an outer circumference of a linear body 22, and a tape 28 with a projection as shown in FIG. The sheath 27 is covered.

In this embodiment, the tape 28 with protrusions and the plastic sheath 27 serve as a protective layer. However, even with such a structure, a large number of protrusions are formed on the inner surface of the protective layer, and when the external pressure is applied, the protrusions are made into an optical fiber core. Since the wire 23 is pressed, the same effect as that of the corrugated pipe covered can be obtained.

8 and 9 show still another embodiment of the present invention. In this linear external pressure sensor 21, an optical fiber core wire 23 is spirally wound on the outer circumference of a linear body 22, and a wire rod 29 is provided on the outer circumference thereof.
Is wound in the opposite direction, and the outer circumference thereof is covered with a plastic sheath 27. As the wire 29, a metal wire or a hard plastic wire is used.

Since the optical fiber core wire 23 and the wire rod 29 are spirally wound in opposite directions, an intersecting portion is formed, and when external pressure is applied, the optical fiber core wire 23 is pressed by the wire rod 29 at the intersection portion and bent. , Increase loss will occur. As described above, the use of the wire rod 29 has the advantages of higher productivity and lower cost than the case of using a corrugated pipe or a corrugated tape.

FIG. 10 shows still another embodiment of the present invention.
In this linear external pressure sensor 21, an optical fiber core wire 23 is vertically provided on the outer circumference of a linear body 22, a wire material 29 is spirally wound on the outer circumference thereof, and a plastic sheath 27 is covered on the outer circumference thereof. Even with such a configuration, the optical fiber core wire 23 and the wire rod 29
Since the intersection is formed, the same effect as the embodiment of FIGS. 8 and 9 can be obtained.

11 and 12 show another embodiment of the present invention. In this linear external pressure sensor 21, a wire material 29 is spirally wound around the outer circumference of a linear body 22, and an optical fiber core wire 23 is wound around the outer circumference thereof.
Is wound in the opposite direction, and the outer circumference thereof is covered with a plastic sheath 27. That is, the positions of the optical fiber core wire 23 and the wire rod 29 of the linear external pressure sensor of FIGS. 8 and 9 are interchanged. In this configuration, when external pressure is applied, the optical fiber core wire 23 is pressed against the wire rod 29 and bent, resulting in an increase in loss.

FIG. 13 shows a submarine power cable 31 incorporating the linear external pressure sensor 21 as shown in each of the above embodiments. Reference numeral 32 denotes three twisted cable cores, and the linear external pressure sensor 21 is twisted in a valley portion between the cable cores 32 together with an intervening cord 33 such as a jute cord or a plastic cord. 34 is a seat made of plastic strings and the like provided on the outside, 35 is armor made of steel wire, and 36 is a seat made of plastic strings and the like provided on the outermost layer.

If such a cable 31 is laid on the seabed, and an OTDR is connected to the optical fiber core wire in the linear external pressure sensor 21 at the end portion thereof to constantly monitor the cable 31, the anchor of the ship is caught by the cable 31. In this case, an increase in the transmission loss of the optical fiber due to the external pressure makes it possible to immediately detect the occurrence of the accident and its position.

If one linear external pressure sensor 21 is inserted in the cable 31, it is possible to detect an accident, but if multiple linear external pressure sensors 21 are inserted at intervals in the circumferential direction as shown in FIG. The external force can also be detected with high sensitivity.

Although the above embodiment has described the submarine power cable, the present invention is not limited to this. For example, a submarine communication cable, a submarine water pipe, an underground cable (electric power,
The same applies to communication), overhead cables (power, communication), and the like.

[0034]

As described above, in the linear external pressure sensor according to the present invention, when external pressure is applied, lateral pressure is applied to the optical fiber core wire by the ridges or projections on the inner surface of the protective layer or the linear members in the protective layer. As a result, the optical fiber core wire is bent with a small bending radius, so that the transmission loss of the optical fiber core wire increases at that position. Therefore, by optically detecting the occurrence of loss increase and its position, it is possible to reliably detect the occurrence of abnormality and its position. If this linear external pressure sensor is housed in the cable, the occurrence of an accident due to the external pressure of the cable and its position can be reliably detected.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a linear external pressure sensor according to an embodiment of the present invention.

2 is a cross-sectional view of the linear external pressure sensor of FIG.

FIG. 3 is a cross-sectional view of a linear external pressure sensor according to another embodiment of the present invention.

FIG. 4 is a vertical sectional view of a linear external pressure sensor according to still another embodiment of the present invention.

5 is a perspective view of a corrugated tape used in the linear external pressure sensor of FIG.

FIG. 6 is a vertical sectional view of a linear external pressure sensor according to still another embodiment of the present invention.

7 is a perspective view of a tape with protrusions used for the linear external pressure sensor of FIG.

FIG. 8 is a vertical sectional view of a linear external pressure sensor according to still another embodiment of the present invention.

9 is a cross-sectional view of the linear external pressure sensor of FIG.

FIG. 10 is a vertical sectional view of a linear external pressure sensor according to still another embodiment of the present invention.

FIG. 11 is a vertical sectional view of a linear external pressure sensor according to still another embodiment of the present invention.

12 is a cross-sectional view of the linear external pressure sensor of FIG.

FIG. 13 is a cross-sectional view of a cable with an external pressure sensor according to an embodiment of the present invention.

FIG. 14 is a cross-sectional view of a conventional external pressure sensor before detection of external pressure.

15 is a sectional view of the external pressure sensor of FIG. 14 after detection of external pressure.

[Explanation of symbols]

21: Linear external pressure sensor 22: Linear body 23: Optical fiber core wire 24: Corrugated pipe 25: Plastic string
26: Wavy tape 27: Plastic sheath 28: Tape with protrusion 2
9: Wire material 31: Submarine power cable 32: Cable core

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshiaki Mizoda 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (7)

[Claims] 1. A protective layer comprising a linear body arranged at the center, at least one optical fiber core wire spirally or longitudinally attached to the outer periphery thereof, and a protective layer coated on the outer periphery thereof. A linear external pressure sensor having a ridge or a protrusion on its inner surface, which is pressed against the optical fiber core wire when the protective layer receives an external pressure and causes an increase in transmission loss in the optical fiber core wire. 2. The linear external pressure sensor according to claim 1, wherein the protective layer is a corrugated pipe. 3. The linear external pressure sensor according to claim 1, wherein the protective layer has a corrugated tape wound around the outer periphery of the linear body and the optical fiber core wire, and a sheath covered on the outer periphery thereof. Consisting of. 4. The linear external pressure sensor according to claim 1, wherein the protective layer is a tape with protrusions wound around the outer circumferences of the linear body and the optical fiber core with the projections inside, and the outer circumference thereof. It consists of a covered sheath. 5. A linear body arranged at the center, at least one optical fiber core wire spirally or longitudinally attached to the outer periphery thereof, and a spiral wire spirally intersecting with the optical fiber core wire at the outer periphery thereof. A linear external pressure sensor comprising: at least one wire that is vertically provided; and a protective layer that covers the outer circumference of the wire. 6. A linear body arranged at the center, at least one wire wound around or vertically attached to the outer periphery thereof, and an optical fiber wound around or vertically attached to the outer periphery thereof so as to intersect with the wire. A linear external pressure sensor comprising a core wire and a protective layer coated on the outer periphery thereof. 7. A cable with an external pressure sensor, wherein the linear external pressure sensor according to claim 1 is housed together with a cable core.