JPH05196685A - Linear external pressure sensor and cable using it - Google Patents

Abstract

(57) [Summary] [Structure] Interposition 25 with a groove having a spiral groove 27 on the outer periphery.
And an optical fiber core wire 29 housed in the groove 27, and a protective layer 31 covering the outer periphery of the grooved interposition 25, and a ridge 33 is formed at the bottom of the groove 27 so that the groove depth When H and the outer diameter D of the optical fiber core wire are applied to the protective layer 31 by external pressure, the optical fiber core wire
29 is pressed against the ridge 33. [Effect] When external pressure is applied, the optical fiber core wire in the protective layer is pressed against the ridges, receives lateral pressure, and is bent with a small bending radius, so that the transmission loss of the optical fiber core wire increases at that position. Occur. 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.

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. 12 has been put to practical use. This is one in which a pair of insulating linear members 12 are twisted together, and a pair of conductive linear members 13 made of a copper wire and the like are twisted along the valleys formed on both sides thereof. 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 deforms 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 overhead cable, and detection of an accident point in such a case is also 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 structure in which a spiral shape is formed on the outer circumference (the spiral direction changes at appropriate intervals, so-called inversion). A grooved interposition having a spiral groove) or a linear groove, an optical fiber core wire housed in the groove of the grooved interposition, and a protective layer coated on the outer periphery of the grooved interposition, A ridge or protrusion is formed at the bottom of the grooved interposition, and the relationship between the depth of the groove and the outer diameter or thickness of the optical fiber core wire is such that when the external pressure is applied to the protective layer, the optical fiber core wire It is characterized in that it is pressed against a ridge or a protrusion. As the optical fiber core wire, a single core optical fiber core wire, a round multi-core optical fiber core wire,
A tape-shaped multi-core optical fiber core wire or the like can be used.

Further, in the present invention, instead of forming a projection or a ridge on the bottom of the grooved interposition, a ridge is formed on the bottom or opening of the grooved interposition on the surface facing the optical fiber core wire. Alternatively, a tape having a protrusion may be stored. In this case, the relationship between the groove depth of the grooved interposition, the outer diameter or thickness of the optical fiber core wire, and the thickness of the tape is such that when the external pressure is applied to the protective layer, the optical fiber core wire causes the projection or protrusion of the tape. It becomes a relationship that is pressed against.

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.

[0010]

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 in the optical fiber core is subjected to a lateral pressure at that position by the groove bottom or the tape projection or protrusion. , Bend. For this reason, the transmission loss of the optical fiber at that position increases sharply, and if this is monitored by the OTDR (optical fiber fault point search device) at the end of the optical fiber core wire, the linear external pressure sensor It becomes possible to detect that an external force is applied (abnormality occurrence) and its position (distance from the end of the optical fiber core).

When the linear external pressure sensor is arranged along the cable core to form a cable containing the external pressure sensor,
For example, if the cable is a submarine cable, it is possible to detect the occurrence of an abnormality and its position when the anchor is caught. Further, in the case of the underground buried cable, for example, when an abnormal external pressure is applied due to subsidence of the ground, the occurrence of the abnormality and the position thereof can be detected.

[0012]

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. The linear external pressure sensor 21 includes a plastic grooved interposition 25 having a tension member 23 at the center. A spiral groove 27 is formed on the outer periphery of the grooved interposition 25, and an optical fiber core wire 29 is housed in the groove 27. Further, a protective layer 31 is coated on the outer periphery of the grooved interposition 25 accommodating the optical fiber core wire 29. The protective layer 31 is usually
It is formed by extrusion coating of plastic, but it can also be formed by tape winding.

In the bottom of the groove 27 of the grooved interposition 25, innumerable ridges 33 extending in the width direction of the groove are formed so as to form a corrugation in the longitudinal direction of the groove. Ridge
It is stored so that it can be placed on top of 33 (see FIG. 2).

As for the optical fiber core wire 29, a single optical fiber core wire 35 is coated with a coating 37 as shown in FIG. 3 (a), and a plurality of optical fiber core wires 29 are formed as shown in FIG. 3 (b). In the form of a round multi-core optical fiber core wire in which one optical fiber element wire 35 is covered with a coating 37, or a flat coating 37 is formed on a plurality of optical fiber element wires 35 arranged in parallel as shown in FIG. It may be in the form of a tape-shaped multi-core optical fiber coated with.

The relationship between the depth H of the groove 27 of the grooved interposition 25 and the outer diameter (thickness in the case of a tape-shaped multi-core optical fiber core) D of the optical fiber core wire 29 is determined by the external pressure applied to the protective layer 31. When it is applied, the optical fiber core wire 29 is pressed against the ridge 33 at the bottom of the groove. Therefore, H and D are 0.9H ≦ D ≦ 1.1H
It is good to have a relationship.

At least one groove 27 and one optical fiber core wire 29 of the grooved interposer 25 may be provided, but it is preferable to provide a plurality of grooves 27 in order to improve detection accuracy. Further, the groove 27 of the grooved interposition 25 is preferably formed in a spiral shape,
Depending on the application, it may be formed in a linear shape.

In order to detect an abnormality by the linear external pressure sensor 21, the sensor 21 is laid on a route for detecting an abnormality, and an OTDR is connected to an optical fiber core wire 29 at an end of the sensor 21 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 protective layer 31 is deformed at that position and the optical fiber core wire 29 is pressed against the ridge 33. The optical fiber core wire 29 receives a local lateral pressure and bends. For this reason, a sudden increase in transmission loss occurs at that position, and a reflected wave is generated.
By observing, the occurrence of an abnormality and its position can be detected.

4 and 5 show another embodiment of the present invention. The linear external pressure sensor 21 has a large number of protrusions 39 formed on the bottom of the groove 27 of the grooved interposition 25. The rest of the configuration is the same as that of the above-mentioned embodiment, so the same parts are given the same reference numerals and explanations thereof are omitted.

FIGS. 6 and 7 show still another embodiment of the present invention. The linear external pressure sensor 21 of FIG. 6 is formed by forming a plurality of protrusions 33 having a triangular cross-section extending in the longitudinal direction of the groove at the bottom of the groove 27 of the grooved interposition 25, and the linear external pressure sensor 21 of FIG. In the grooved interposition 25, a ridge 33 having a chevron cross-section extending in the longitudinal direction of the groove is formed at the bottom of the groove 27. Since the configuration other than the above is the same as that of the embodiment shown in FIGS. 1 and 2, the same parts are designated by the same reference numerals and the description thereof will be omitted.

FIG. 8 shows still another embodiment of the present invention.
In this linear external pressure sensor 21, the bottom of the groove 27 of the grooved interposition 25 is flat, the tape 41 is stored in the bottom of the groove 27, and the optical fiber core wire 29 is stored thereon. tape
As shown in FIGS. 9 (a) to 9 (c), reference numeral 41 denotes a ridge 33 or a projection 39 formed on at least one surface. The ridge 33 or the projection 39 is opposed to the optical fiber core wire 29 to form the groove 27. It is stored at the bottom of the. The tension member 23 is located at the center of the grooved interposition 25, and the protective layer 31 is located on the outer periphery of the grooved interposition 25, as in the above-described embodiments.

The depth H of the groove 27 of the grooved interposition 25, the outer diameter (or thickness) D of the optical fiber core wire 29, and the thickness T of the tape 41.
The relationship with the optical fiber core wire is that the external pressure is applied to the protective layer 31.
29 is pressed against the ridge 33 or the protrusion 39 of the tape 41. Therefore, H, D and T are 0.9H ≦
It is advisable to have a relationship of D + T ≦ 1.1H.

Even with such a structure, the same effect as that of the linear external pressure sensor shown in FIGS. 1 and 2 can be obtained, and since it is not necessary to form a protrusion or a protrusion on the bottom of the groove,
This has the advantage of facilitating the manufacture of the grooved interposition.

FIG. 10 shows still another embodiment of the present invention.
In this linear external pressure sensor 21, the positions of the tape 41 and the optical fiber core wire 29 in FIG. 8 are exchanged, and the tape 41 is arranged in the opening of the groove 27. Since the other structure is the same as that of the embodiment of FIG. 8, the same portions are denoted by the same reference numerals and the description thereof will be omitted.

FIG. 11 shows a submarine power cable 43 incorporating the linear external pressure sensor 21 as shown in each of the above embodiments. Reference numeral 45 denotes three twisted cable cores, and the linear external pressure sensor 21 is twisted in a valley portion between the cable cores 45 together with an interposition string 47 such as a jute string or a plastic string. 49 is a seat made of plastic string or the like provided on the outer side, 51 is armor made of steel wire or the like, and 53 is a seat made of plastic string or the like provided on the outermost layer.

If such a cable 43 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 43, the anchor of the ship is caught by the cable 43. 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 43, 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.

[0028]

As described above, in the linear external pressure sensor according to the present invention, when an external pressure is applied, the optical fiber core wire in the protective layer is pressed against the ridges or projections to receive the lateral pressure,
Since it is bent with a small bending radius, an increase in the transmission loss of the optical fiber core occurs 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 cross-sectional view of a linear external pressure sensor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the longitudinal direction of the groove of the linear external pressure sensor shown in FIG.

3A is a cross-sectional view of a single-core optical fiber core wire used in the linear external pressure sensor of the present invention, FIG. 3B is a cross-sectional view of the same round multicore optical fiber core wire, and FIG. Sectional drawing of a multi-core optical fiber core wire.

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

5 is a cross-sectional view taken along the longitudinal direction of the groove of the linear external pressure sensor shown in FIG.

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

FIG. 7 is a cross-sectional view of a linear external pressure sensor according to still another embodiment of the present invention.

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

9 (a), (b) and (c) are perspective views of a tape used in the linear external pressure sensor of FIG. 8, respectively.

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

FIG. 11 is a cross-sectional view of a cable with an external pressure sensor according to an embodiment of the present invention.

FIG. 12 is a cross-sectional view of a conventional linear external pressure sensor before external pressure detection.

13 is a sectional view of the linear external pressure sensor of FIG. 12 after external pressure is detected.

[Explanation of symbols]

21: linear external pressure sensor 23: tension member 25: interposition with groove 27: groove 29: optical fiber core 31: protective layer 33: ridge 39: protrusion 41: tape 43: submarine power cable 45: cable core

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical indication location H01B 11/22 7244-5G (72) Inventor Atsuro Takase 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (3)

[Claims] 1. A grooved interposition having a spiral or linear groove on the outer periphery, an optical fiber core wire accommodated in the groove of the grooved interposition, and a protective layer coated on the outer periphery of the grooved interposition. A ridge or protrusion is formed on the bottom of the groove of the grooved interposition, and the relationship between the depth of the groove and the outer diameter or thickness of the optical fiber core wire is such that when an external pressure is applied to the protective layer, the optical fiber core wire The linear external pressure sensor is characterized in that it is pressed against a ridge or a protrusion on the bottom of the groove. 2. A grooved interposition having a spiral or linear groove on the outer periphery, an optical fiber core wire accommodated in the groove of the grooved interposition, and an optical fiber core accommodated in the bottom or opening of the groove of the grooved interposition. And a tape having a ridge or protrusion on the surface facing the optical fiber core and a protective layer coated on the outer periphery of the grooved interposition, and the groove depth of the grooved interposition and the outside of the optical fiber core. A linear external pressure sensor characterized in that a relationship between a diameter or a thickness and a thickness of a tape is such that when an external pressure is applied to a protective layer, an optical fiber core wire is pressed against a ridge or a protrusion of the tape. 3. A cable with an external pressure sensor, wherein the linear external pressure sensor according to claim 1 or 2 is housed together with a cable core.