JP3312575B2 - Method of laying optical fiber sensor for detecting terrain displacement and terrain displacement detecting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting terrain displacement from a break in an optical fiber buried in the ground, and more particularly to terrain displacement detection that has a constant detection sensitivity and can reliably identify a location where terrain displacement has occurred. TECHNICAL FIELD The present invention relates to an optical fiber sensor for use, a method of laying the same, and a terrain displacement detecting device using the same.

[0002]

2. Description of the Related Art Railway lines and highways are often provided on embankments. Therefore, it is necessary to detect topographical displacement of the embankment in order to maintain a railway line or an expressway. Here, terrain displacement means displacement, deformation,
Collapse, for example, landslides, and also includes the collapse and rock fall of surrounding objects.

FIG. 7 shows a conventional technique for detecting terrain displacement in a relatively long place. One side of the track 1 has a slope inclined upward, and the other side has a slope 71 inclined downward.
, A metal wire 72 is disposed on the down slope along the track 1 or buried in the ground, one end of which is fixed to the pile 73, and the other end of which is fixedly attached to the switch 74. To the metal wire 72
Are stretched as shown by solid lines. When the landslide occurs, as shown by the dotted line, the metal wire 72 is pulled by the falling earth and sand, and the switch 74 operates, thereby notifying that an abnormality has occurred.

[0004]

In the prior art, when the length of the metal wire 72 is long, it is difficult to maintain a state where the metal wire 72 is pulled with a substantially constant strength. The detection sensitivity is not constant due to loosening. Also, the metal wire 72
Are provided at short intervals so as not to lengthen the switch 74.
Power supply is required for each switch portion and the device becomes complicated. In addition, the switch 74 has poor mechanical reliability because it has a movable part. Also, there is a risk of damage due to lightning.

As described above, the prior art is not practical for detecting terrain displacement, and at present the guards are patroling.

On the other hand, an optical fiber is buried underground,
It has been proposed to detect a terrain displacement from an increase in optical transmission loss due to a strain generated in an optical fiber due to the terrain displacement. In order to enhance the practicality of such an optical fiber system, it is important that the detection sensitivity is constant and that the location where the terrain displacement occurs can be reliably specified.

An object of the present invention is to solve the above problems, and constant detection sensitivity, the method of laying terrain displacement sensing optical fiber sensor terrain displacement generating portion can be reliably identified, 及
And a terrain displacement device.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a terrain displacement detection method is provided.
The installation method of the intelligent optical fiber sensor depends on the detection of terrain displacement.
Do not break due to terrain displacement along long elephant places.
Lay two transmission optical fibers in a
Optical fiber in advance in each of the detection sections
Harden around the bar with a solid material to withstand the specified stress load
Linear parts that can be broken by higher stress loads
The optical fiber is made by the material
An optical fiber sensor for detecting terrain displacement that is disconnected
Install the fiber optic sensors for terrain detection in each section.
Connection between the two transmission optical fibers.
It is a sign .

[0009]

[0010] The transmission optical fiber may be laid with an extra length so as not to be disconnected by terrain displacement.

The optical fiber sensor for detecting terrain displacement includes:
It may be connected between the start point of the section of one transmission optical fiber and the end point of the section of the other transmission optical fiber.

The above-mentioned optical fiber sensor for detecting terrain displacement includes:
The detection section may be laid back and forth through different places.

In the terrain displacement detecting device according to the present invention , two transmission optical fibers are laid along a long place where the terrain displacement is to be detected so as not to be disconnected by the terrain displacement.
Pre the respective detection sections obtained by dividing the long location more
The optical fiber around the optical fiber with a solid material
And has the strength to be destroyed by a higher stress load.
A linear member, and the optical
A terrain displacement detecting optical fiber in which the fiber is disconnected is laid, and a terrain displacement detecting optical fiber sensor in each section is connected between the two transmission optical fibers in the section to form a ladder-shaped optical circuit. A light source that generates pulsed light is connected to one end of one transmission optical fiber, and a photodetector is connected to one end of the other transmission optical fiber. A signal processing unit for specifying a section where displacement has occurred is provided.

[0014]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, a trunk cable 3 containing a first optical fiber 2a and a second optical fiber 2b is embedded in parallel with the line 1. These optical fibers 2
Reference numerals a and 2b denote transmission optical fibers 2 used exclusively for transmitting optical signals, and a trunk cable 3 incorporating such a transmission optical fiber 2 does not break the transmission optical fiber 2 due to terrain displacement. It is a structure.
For this purpose, in the present embodiment, a spacer-type exterior is used. In addition, snake laying has a certain extra length so that it does not break even if the trunk cable 3 moves due to terrain displacement, and it takes a laid form that allows room.
A trough is provided and laid in the trough.

Since the track 1 to be detected for terrain displacement extends over a long place, the track 1 is divided into a plurality of detection sections A, B, and C, and a connection box 4 is installed in each of the detection sections, and these connection sections are connected. An optical splitter / demultiplexer 5a, 5b for splitting / combining light from the transmission optical fiber 2 is provided in the box 4;
An optical fiber sensor 6 for detecting terrain displacement according to the present invention is laid between a and 5b. Since the optical fiber sensor 6 for detecting terrain displacement in each section is connected between the two transmission optical fibers 2 in the section, the optical circuit has a ladder shape. In the embodiment of FIG. 1, the terrain displacement detecting optical fiber sensor 6 is connected between the start point of the section of one transmission optical fiber 2 and the start point of the section of the other transmission optical fiber 2. . The terrain displacement detecting optical fiber sensor 6 is a combination of two optical fibers 7, 7, and the optical fiber 7 is laid back and forth in the section. These optical fibers 7, 7 are configured such that light having passed through one optical fiber 7 returns to the other optical fiber 7 by fusion splicing at a terminal 8. The terrain displacement detecting optical fiber sensor 6 is laid along the track 1 where the terrain displacement is to be detected.

The terrain displacement detecting optical fiber sensor 6
As shown in FIG. 2, is a linear member 10 in which the optical fiber 7 and the solid material 9 are integrally formed by solidifying the optical fiber 7 with a solid material 9 in advance. It has the strength to withstand and to be destroyed by a higher stress load. The linear member 10 is buried in a location to be detected, and the optical fiber 7 is also disconnected when the linear member 10 is broken due to terrain displacement. In this embodiment, plastic concrete or epoxy resin is used as the solid material 9. In FIG. 2, two optical fibers 7 are incorporated in one linear member 10 according to the embodiment of FIG.

As shown in FIG. 1, a measuring device 11 is provided at one end of the trunk cable 3. A light source (pulse generator) 12 connected to one end of one transmission optical fiber 2 to generate pulse light and connected to one end of the other transmission optical fiber 2 return to the measuring device 11. A light receiver 13 for receiving the pulse light is provided, and a signal processing unit 14 for specifying a section where the terrain displacement occurs from the pulse light train reaching the light receiver 13 is provided. In this embodiment,
For the sake of simplicity, the number of sections is three, and sections A, B, and C are arranged from the side closer to the measuring device 11.
Also, by using the connection box 4 for storing the optical branching multiplexers 5a and 5b and the connection box for storing the connection part of the terminal 8 of the optical fiber 7 of the optical fiber sensor 6 for detecting terrain displacement,
The number of connection boxes 4 is reduced.

The operation of the terrain displacement detecting device shown in FIG. 1 will be described.

The pulse light emitted from the light source (pulse generator) 12 enters the first optical fiber 2a and propagates in the first optical fiber 2a in the longitudinal direction. The light is branched by the wave device 5a, and is divided into a pulse light component propagating in the first optical fiber 2a in the longitudinal direction as it is and a pulse light component branching and propagating to the optical fiber sensor 6 for detecting terrain displacement. The pulse light component branched to the terrain displacement detecting optical fiber sensor 6 reciprocates in a portion laid along the line 1 and is multiplexed to the second optical fiber 2b by the optical branching / combining device 5b. Such optical branching / combining is performed in each section. Accordingly, the pulse light transmitted through the optical fiber sensor 6 for detecting terrain displacement in each of the sections A, B, and C is collected on the second optical fiber 2b and received by the light receiver 13. The signal obtained after the photoelectric conversion by the photodetector 13 is a pulse time series signal based on the delay time corresponding to each section since the pulse light propagates in different distances.

The time-series signal shown in FIG. 3A is a signal at a normal time, and the pulses are arranged in the order of propagation in the section closer to the measuring device, that is, in the order of the A section, the B section, and the C section. . This time-series signal is sent to the signal processing unit 14. In the signal processing unit 14, the normal state of the time-series signal is stored in advance and compared with the received time-series signal. When a pulse at any point is not received, it is determined that the optical fiber has been disconnected in a corresponding section, that is, terrain displacement has occurred. The time-series signal shown in FIG. 3B has no pulse in the B section. Therefore, it is specified that the terrain displacement has occurred in the section B.

In the present invention, since the optical fiber sensor 6 for detecting terrain displacement is constituted by the linear member 10 formed by solidifying the optical fiber 7 with a solid material 9 around the optical fiber 7, the linear member is detected by terrain displacement. When a stress load is applied to the wire 10, the linear member 10 is deformed and destroyed by a stress load exceeding its strength. At this time, the optical fiber 7 is also disconnected. Therefore, when the terrain displacement occurs in the section B, the pulse in the section B does not return as shown in FIG. The breaking strength can be arbitrarily set by changing the thickness of the solid material 9 of the linear member 10 or storing the linear member 10 in a conduit.

As a method of installing the linear member 10, 1
When one section is long and it is difficult to cover one linear member 10, as shown in FIG. 4, piles 41 are provided at regular intervals along the track, and a connection box is 4
2 and the optical fibers 43 are connected by the connection means 44, so that the length per one linear member 10 can be reduced.

Next, another embodiment will be described.

As shown in FIG. 5, the optical fiber sensor 6 for detecting terrain displacement has one optical fiber 7 incorporated in one linear member 10. Here, the optical fiber 7 branched from the first optical fiber 2 a in the first connection box 4 is multiplexed with the second optical fiber 2 b in the next connection box 4. That is, the terrain displacement detecting optical fiber sensor 6 is connected between the start point of the section of one transmission optical fiber 2 and the end point of the section of the other transmission optical fiber 2. Although only one optical fiber 7 is laid along the line 1 where the terrain displacement is to be detected, the point that the section can be specified by the time-series signal is the same as in the above embodiment. Thereby, the usage amount of the optical fiber 7 can be reduced.

As shown in FIG. 6, the optical fiber sensor 6 for detecting terrain displacement has one optical fiber 7 incorporated in one linear member 10. Here, the optical fiber 7 branched from the first optical fiber 2a in a certain connection box 4 is finally returned to the same connection box 4 and multiplexed with the second optical fiber 2b. However, these reciprocating optical fibers 7, 7 are built in separate linear members 10, 10, and are laid back and forth through different places even in the same detection section. A wider range can be set as a detection target in the same longitudinal section as compared with the embodiment of FIG.

[0027]

The present invention exhibits the following excellent effects.

(1) Since the optical fiber can be reliably disconnected due to the displacement of the terrain, the detection can be surely performed.

(2) Disconnection of the optical fiber sensor for detecting terrain displacement at a certain location does not hinder detection at other locations.

(3) The location to be detected can be set to any length, and the length of the section can be relatively long.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a terrain displacement detection device using an optical fiber sensor for terrain displacement detection according to an embodiment of the present invention.

FIG. 2 is a structural diagram of an optical fiber sensor for detecting terrain displacement in the embodiment of FIG.

FIG. 3 is a diagram of a time-series signal obtained by the terrain displacement detection device of the present invention.

FIG. 4 is a diagram showing a configuration of an optical fiber sensor for detecting terrain displacement according to the present invention.

FIG. 5 is a configuration diagram of a terrain displacement detection device using a terrain displacement detection optical fiber sensor according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of a terrain displacement detection device using a terrain displacement detection optical fiber sensor according to another embodiment of the present invention.

FIG. 7 is a configuration diagram of a terrain displacement detection device showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Line 2 Transmission optical fiber 3 Trunk cable 4 Connection box 6 Terrain displacement detection optical fiber sensor 7 Optical fiber 9 Solid material 10 Linear member 11 Measuring device 12 Light source 13 Optical receiver 14 Signal processing unit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuhide Motoki 880 Sunazawa-cho, Hitachi City, Ibaraki Prefecture Inside the Takasago Plant of Hitachi Cable Co., Ltd. (56) References JP 8-43148 (JP, A) JP 8-75506 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01D 21/00 E02D 17/20 106 G01B 11/16 G01C 7/02 G02B 6/00

Claims (5)

(57) [Claims] 1. Along a long place where a terrain displacement is to be detected.
To prevent disconnection due to terrain displacement
Fiber is laid, and the above long place is divided into multiple parts.
In each of the sections, solidify around the optical fiber with a solid material in advance.
Withstand the specified stress load, and with a higher stress load
Construct a linear member with strength to be destroyed
Terrain deformation that breaks the optical fiber due to destruction
An optical fiber sensor for position detection is installed, and terrain detection in each section
Optical fiber sensor for the above two transmission optical fibers in the section.
Terrain displacement detection light connected between fibers
How to install fiber sensor. 2. The transmission optical fiber according to the terrain displacement.
It is specially laid out with extra length to prevent disconnection.
2. An optical fiber sensor for detecting terrain displacement according to claim 1.
How to lay sa. 3. The optical fiber sensor for detecting terrain displacement,
Start point of the section of one transmission optical fiber and transmission of the other
Connection between the end of the section of the optical fiber
3. The method of laying an optical fiber sensor for detecting terrain displacement according to claim 1, wherein 4. The optical fiber sensor for detecting terrain displacement,
The cloth goes back and forth through different places in the detection section
3. The method according to claim 1, wherein
How to lay the on- board terrain displacement detection optical fiber sensor. 5. A method according to claim 1, wherein the detection unit detects a terrain displacement along a long place.
To prevent disconnection due to terrain displacement
Fiber is laid, and the above long place is divided into multiple parts.
In each of the sections, solidify around the optical fiber with a solid material in advance.
Withstand the specified stress load, and with a higher stress load
Construct a linear member with strength to be destroyed
Terrain deformation that breaks the optical fiber due to destruction
An optical fiber for position detection is laid to detect terrain displacement in each section.
Connect the optical fiber sensor to the two transmission optical
To form a ladder-like optical circuit.
A light source that generates pulsed light is connected to one end of the optical fiber
A receiver is connected to one end of the other transmission optical fiber.
And the terrain displacement from the pulsed light train reaching the receiver
Characterized by the provision of a signal processing unit that identifies the section where
Terrain displacement detection device.