JPH0616837U - Linear external pressure sensor - Google Patents

Abstract

(57) [Summary] [Structure] A linear body 5 having a spiral groove 6 on the outer periphery,
The coated optical fiber 7 housed in the groove 6, the elastic core wrap 8 wound around the outer periphery of the linear body 5, and the protective layer 9 provided on the outer periphery thereof are provided, and the depth of the groove 6 and the coated optical fiber 7 With respect to the outer diameter, the elastic core wrap 8 is compressed when an external pressure is applied to the protective layer 9, and a lateral pressure is applied to the coated optical fiber 7. [Effect] When external pressure is applied to the protective layer, the protective layer and the elastic core wrap are deformed at that position, and the coated optical fiber receives a local lateral pressure, so that the transmission loss of the coated optical fiber increases at that position. By optically detecting the occurrence of this loss increase and its position, it is possible to reliably detect the occurrence of abnormality and its position.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a linear external pressure sensor using an optical fiber.

[0002]

[Prior art]

 A conventional general linear external pressure sensor is shown in FIG. The linear external pressure sensor 1 is formed by twisting a pair of insulating linear members 2 and twisting a pair of metal wires 3 such as copper wires along a valley formed on both sides thereof. That is, in this state, the pair of metal wires 3 are in an insulated state.

If such a linear external pressure sensor 1 is laid on the route for detecting the external pressure, and if external pressure is applied at any of the locations, the linear external pressure sensor 1 will be installed at that location. It transforms like. That is, the insulating linear body 2 escapes to both sides, and the metal wire 3 comes close to the center and contacts. As a result, the pair of metal wires 3 are electrically connected at that position, so that it is possible to detect that external pressure is applied by electrically detecting this at one end.

[0004]

[Problems to be solved by the device]

 The conventional linear external pressure sensor can detect that an external pressure is applied to any place, but there is a problem that it is difficult to detect the position. Such a linear external pressure sensor is used for detecting an accident due to the external pressure (external force) of an electric cable. However, if not only the occurrence of an accident but the position of the accident can be detected, subsequent measures can be taken promptly. it can.

Further, such an accident 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 whether or not there is an abnormality occurrence, If it is possible to detect at which position the abnormality has occurred, it is effective in improving the monitoring accuracy.

[0006]

[Means for Solving the Problems]

 The present invention provides a linear external pressure sensor which solves the above-mentioned problems, and has a structure in which a linear body having a spiral or linear groove on the outer periphery and a groove in the linear body are provided. The coated optical fiber accommodated therein, the elastic core wrap wound around the outer periphery of the linear body, and the protective layer provided on the outer periphery of the elastic core wrap are provided, and the groove depth of the linear body and the coated optical fiber The relationship with the outer diameter or the thickness is such that when the external pressure is applied to the protective layer, the elastic core wrap is compressed and lateral pressure is applied to the coated optical fiber.

The term “coated optical fiber” as used herein refers to an optical fiber element wire or optical fiber core wire obtained by applying a protective coating to an optical fiber, an optical fiber unit (a plurality of optical fiber element wires or a core wire group). , A round multi-fiber optical fiber or a tape-shaped multi-fiber optical fiber.

[0008]

[Action]

 In the linear external pressure sensor of the present invention, when an external force is applied to any position in the longitudinal direction, the coated optical fiber receives a local lateral pressure at that position via the elastic core wrap. For this reason, the transmission loss of the optical fiber increases sharply at that position. 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 sensor It is possible to detect that an external force is applied to the (abnormal occurrence) and its position (distance from the end of the optical fiber).

[0009]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 show an embodiment of the present invention. This linear external pressure sensor 4 is provided with a linear body 5 having a spiral groove 6 formed on the outer periphery thereof, and a coated optical fiber 7 is housed in the groove 6. An elastic core wrap 8 is wound around the outer periphery of the linear body 5 accommodating the coated optical fiber 7, and a protective layer 9 is provided on the outer periphery thereof.

The relationship between the depth D of the groove 6 of the linear body 5 and the outer diameter d of the coated optical fiber 7 (thickness in the case of a tape-shaped multi-core optical fiber core) depends on the external pressure applied to the protective layer 9. In this case, the range of 0.9D ≦ d ≦ 1.1D is preferable so that the coated optical fiber 7 is surely subjected to lateral pressure via the elastic core wrap 8, and in particular, both are the same in this embodiment.

As the linear member 5, a plastic member is used, but a member having a tensile strength member at the center or a metallic member can also be used. The bottom surface of the groove 6 may be flat as shown in FIG. 1 or may be curved. At least one groove 6 of the linear body 5 and at least one coated optical fiber 7 are required, but it is desirable to provide a plurality of grooves 6 in order to enhance the detection accuracy. Further, the groove 6 of the linear body 5 is preferably formed in a spiral shape, but may be formed in a linear shape depending on the application.

A rubber tape or the like is preferably used as the elastic core wrap 8, but other materials may be used as long as they can be deformed by external pressure. Further, although the protective layer 9 is composed of a plastic sheath or the like, it is also possible to use a metallic one. The material and thickness of the elastic core wrap 8 and the protective layer 9 are determined by the level of external pressure to be detected. It is preferable that the elastic core wrap 8 and the protective layer 9 be deformed by receiving external pressure and then be restored almost completely to the original cross-sectional shape when the external pressure is removed. This is convenient because it can be used repeatedly.

In order to detect an abnormality by the linear external pressure sensor 4, the sensor 4 is laid on a route to perform abnormality detection, and an OT DR is connected to the coated optical fiber 7 at the end of the sensor 4 to detect an abnormality. Input a pulse signal for constant monitoring. In this state, if an external pressure is applied to any part of the linear external pressure sensor 4 (an abnormality occurs), the protective layer 9 and the elastic core wrap 8 are deformed at that position, and the coated optical fiber 7 receives a local lateral pressure. Receive. For this reason, a sudden increase in transmission loss occurs at that position, and a reflected wave is generated. Therefore, if the reflected wave is observed by OTDR, the occurrence of an abnormality and its position can be detected.

That is, when the linear external pressure sensor 4 receives an external pressure, the coated optical fiber 7 housed in the groove 6 of the linear body bends slightly due to the local lateral pressure transmitted through the protective layer 9 and the elastic core wrap 8. Since it is bent by the diameter, a clear loss increase occurs at the external pressure application position. Therefore, the abnormality can be detected with high sensitivity.

[0015]

[Effect of device]

 As described above, in the linear external pressure sensor according to the present invention, when an external pressure is applied, the protective layer and the elastic core wrap are deformed at that position, and the coated optical fiber receives a local lateral pressure and is bent with a small bending diameter. Therefore, the transmission loss of the coated optical fiber 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.

[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 vertical sectional view of the linear external pressure sensor shown in FIG.

FIG. 3 is a cross-sectional view of a conventional linear external pressure sensor before external pressure detection.

4 is a cross-sectional view of the linear external pressure sensor of FIG. 3 after external pressure is detected.

[Explanation of symbols]

 4: linear external pressure sensor 5: linear body 6: groove 7: coated optical fiber 8: elastic core wrap 9: protective layer

Claims (1)

[Scope of utility model registration request] 1. A linear body having a spiral or linear groove on the outer periphery, a coated optical fiber housed in the groove of the linear body, and an elastic core wrap wound around the outer periphery of the linear body. , A protective layer provided on the outer periphery of the elastic core wrap, the relationship between the groove depth of the linear body and the outer diameter or thickness of the coated optical fiber, the elastic core wrap is compressed when external pressure is applied to the protective layer. A linear external pressure sensor characterized in that a lateral pressure is applied to the coated optical fiber.