JP2585169B2 - Landslide detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a landslide detection device for automatically detecting a landslide disaster on a railway, a road or the like and preventing an accident from occurring.

[0002]

2. Description of the Related Art For example, railway lines are often laid on embankments, and one or both sides of the railway lines are often sloped. For this reason, there is a high risk of terrain displacement, and when terrain displacement occurs and hinders safe operation of the train, it is necessary to stop the train before the train reaches the site.

Also, in the case of a road, if a landslide can be detected, measures such as prohibiting the passage of vehicles can be taken, so that safety can be improved. Conventionally, a landslide detection device has been proposed in which a metal wire is stretched, one end thereof is connected to a switch, and when the wire is pulled by the landslide, the switch operates to detect an abnormality.

[0004]

In a conventional landslide detection device using a metal wire and a switch, the wire expands and contracts due to temperature fluctuations, the wire loosens due to loosening of a fixed portion, etc., and operates properly due to a lightning strike or the like. There is a possibility that it will not work or malfunction. . Also, to detect landslides over a long distance, one wire cannot be stretched long,
Since relatively short wires are to be sequentially stretched, it is difficult to lay them.

[0005] For these reasons, the wire method has not been put to practical use, and at present, visual confirmation is performed by a watchman. This manual check is accurate,
The disadvantage is that it takes a long time to find and requires much effort.
It is an object of the present invention to provide a landslide detection device that can automatically detect a landslide without manual intervention and that can monitor over a wide range.

[0006]

SUMMARY OF THE INVENTION In the present invention, an landslide detection device is constructed by utilizing the fact that the optical fiber has a characteristic that the propagation characteristic of light greatly changes when the optical fiber is deformed. That is, an optical fiber is laid at a place where the occurrence of a landslide is to be monitored, light is propagated through the optical fiber, and a change in light propagating through the optical fiber is detected to detect the occurrence of the landslide.

[0007] More specifically, two optical fibers are laid at a place to be monitored, and light having high coherence and light having low coherence are propagated through the two optical fibers, and the optical fibers are propagated. The change in the phase of the highly coherent light is monitored by the optical interferometer, and the change in the transmission loss of the light with low coherence transmitted through the optical fiber is monitored by the optical loss detector. A high-sensitivity landslide detection device is configured to detect a precursor of a landslide with the high-sensitivity landslide detection device, and to configure a landslide detection device that reliably detects occurrence of the landslide with an optical fiber and an optical loss detector.

[0008]

FIG. 1 shows an embodiment of the present invention. In the figure, reference numeral 1 denotes a first light emitting light having good coherence (for example, 1.55 μm).
The light source 2 is a second light source that emits light having low coherence (for example, 0.85 μm). The first light source 1 is, for example, 1.55 μm
DFB laser light source can be used. The second light source 2 is a multi-mode laser light source, a light emitting diode (LE).
D), a white light source can be used. In this embodiment, since 1.3 μm band polarization maintaining fibers are used for the optical fibers 5A and 5B, the 0.85 μm light becomes multimode during propagation through the optical fiber, so that the coherence is reduced.

The light emitted from the first light source 1 and the light emitted from the second light source 2 are multiplexed by a multiplexer 3 and are superimposed on each other and provided to an optical coupler 4. The optical coupler 4 has a characteristic that the light having the light wavelength is branched at a ratio of approximately 50: 50%, and the light having the light wavelength is hardly branched. Therefore, the two optical fibers 5A connected to the output side of the optical coupler 4
And 5B, the light is split by 50%, and the light is output to one of the optical fibers, 5A in this example.

As the optical fibers 5A and 5B, for example, a polarization preserving fiber can be used, and the optical fiber is covered with a protective covering having appropriate elasticity, and when an external force is applied, light is applied from above the protective covering. It is configured such that pressure is applied to the fiber strand. Specifically, the applicant has already proposed “Japanese Patent Application No. 4-195257: Terrain displacement detection sensor”.
Structures such as "Japanese Patent Application No. 4-195258: An optical fiber laying structure for detecting terrain displacement" and "Japanese Patent Application No. 4-195260: Optical fiber cable for pressure sensor" can be adopted.

The optical fibers 5A and 5B are laid at the place to be monitored, and their length can be about 40 to 50 km.
An optical coupler 6 is connected to the tip, and the light that has passed through the two optical fibers 5A and 5B is multiplexed by the optical coupler 6, and the multiplexed light is given to an optical interference detector 7, The interference detector 7 monitors whether or not the phase difference between the light passing through the two optical fibers 5A and 5B changes. According to the optical interference detector, when two lights are input in the same phase, the lights reinforce each other, so that the light intensity becomes maximum (a value substantially equal to the amount of light emitted from the light source 1), and the light intensity becomes 0 when the phases are opposite. . A change in the phase of the two lights can be detected from the change in the light intensity.

The other output light of the optical coupler 6 is demultiplexed only by the demultiplexer 8 and taken out, and this light is supplied to the loss detector 9 to monitor a change in the amount of light reaching. It is known that even when a small external force is applied to an optical fiber as a characteristic of the optical fiber, the phase of light propagating through the optical fiber changes. Therefore, by monitoring the change in the mutual phase of the light propagating through the two optical fibers 5A and 5B in the optical interference detector 7, if a slight difference occurs in the disturbance given to the optical fibers 5A and 5B, Changes can be detected. In other words, a slight topographic change that occurs before the landslide can be captured. When a landslide occurs and a large external force is applied to the optical fiber, the amount of change in the optical fibers 5A and 5B increases, so that the amount of attenuation of the propagating light increases, and the change is detected by the loss detector 9. .

[0013]

As described above, according to the present invention, the optical interference detector 7 monitors the change in the mutual phase of the light propagating through the two optical fibers 5A and 5B, thereby achieving high sensitivity. Landslide detector can be configured. Therefore, it is possible to catch a sign of the landslide and to give a forecast of the landslide.

When a landslide occurs in earnest, the optical fibers 5A and 5B are greatly deformed in response to a change in terrain. As a result, the arrival rate of light propagating through the optical fiber 5A or 5B decreases, so that the loss detector 9 can detect an increase in loss and notify the occurrence of landslide. As described above, according to the present invention, the landslide can be automatically detected without manual intervention. Therefore, the occurrence of the landslide can be notified in a very short time after the occurrence. Moreover, since the sensor unit for detecting the landslide is composed of the optical fibers 5A and 5B, the optical fibers 5A and 5B can be extended and laid. Therefore, landslides can be monitored over a wide area without human intervention. In addition, since a high-sensitivity landslide detector can be configured, a precursor of a landslide can be detected.
As a result, it is possible to provide a forecast of a landslide, thereby obtaining an advantage that safety management can be thoroughly performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 first light source 2 second light source 3 multiplexer 4, 6 optical coupler 5A, 5B optical fiber 7 optical interference detector 8 duplexer 9 loss detector light with high coherence light with low coherence

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Motohara 1-21-6 Dogenzaka, Shibuya-ku, Tokyo Inside Japan Aviation Electronics Industry Co., Ltd. (72) Inventor Shuichi Aihara 1-21 Dogenzaka, Shibuya-ku, Tokyo No. 6 Inside Japan Aviation Electronics Industry Co., Ltd. (72) Yuzo Takasaka Inventor 1-21-6 Dogenzaka, Shibuya-ku, Tokyo Japan Inside (72) Inventor Masaaki Ujikawa 1-chome Dogenzaka, Shibuya-ku, Tokyo 21-6 Japan Aviation Electronics Industry, Ltd. (56) References JP-A-4-80618 (JP, A) JP-A-2-242119 (JP, A)

Claims (1)

(57) [Claims] 1. A. First Embodiment B. a first light source that emits light having high coherence; B. a second light source that emits light having a wavelength different from the wavelength of the light of the first light source and low coherence; D. a multiplexer for multiplexing the light of the first light source and the light of the second light source; B. an optical coupler that branches the superimposed light obtained from the multiplexer into two optical paths; B. two optical fibers connected to the two optical paths branched by the optical coupler and to be laid at the monitored part; The high coherence obtained through these two optical fibers
An optical interference detector measuring the change in phase difference had light, G. A landslide detection device comprising: a loss detector configured to measure a loss amount of the low coherence light obtained through two optical fibers.