JP2000155040A - Monitoring system for survey object with optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor a survey object with an optical fiber at a low cost. SOLUTION: In this monitoring system, many U-shaped optical fibers 4 are fitted to a linear core 3 with tip portions 5 drifted in sequence in the axial direction of the core 3 to form a linear sensor 2. The linear sensors 2 are arranged vertically and horizontally in a mesh shape on a survey object such as a ridge, natural ground or a structure, and the optical fibers 4 of the linear sensors 2 are connected to a monitoring device 6 specifying the damage position of an optical fiber by utilizing the phenomenon that transmitted light disappears due to its rupture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitoring system for an object to be searched, and more particularly to a monitoring system for monitoring damage of an optical fiber.

[0002]

2. Description of the Related Art Generally, it is desired to be able to appropriately predict and warn about so-called landslides in which rocks and topsoils on hillsides suddenly fall down on cliffs and steep slopes, and landslides in tunnels. On the other hand, in the case of a structure or the like, it is desired that prediction and warning can be appropriately obtained in the same manner in consideration of the deterioration of the structure.

At present, in a search for a landslide, as shown in FIG. 9, displacement meters 11 are arranged in a row on a mountain 1 to be searched. Originally, the displacement meter 11
Are desired to be densely arranged in a plurality of rows.
Are arranged in a line because the displacement gauge is expensive, so that many measurement points cannot be obtained due to the installation cost.

[0004]

By the way, it has been considered to use an optical fiber sensor for exploring a landslide. An optical fiber sensor utilizing polarization, interference, backscattering phenomenon, and the like of light propagating in an optical fiber is used.

However, the polarization, interference,
In the case of an optical fiber sensor that uses the phenomenon that the intensity of light propagating due to the backscattering phenomenon, etc., processing of the optical fiber becomes necessary and the evaluation device becomes expensive, so it is necessary to use a part of the mountain to be searched. There is a problem that many measurement points cannot be obtained, such as installing only a device.

For example, so-called high refractive index portions (gratings) are formed at equal intervals in a part of the core of an optical fiber, so that light of a certain wavelength is reflected by the gratings and the remaining light is transmitted. There is a Bragg grating sensor. The principle of this Bragg grating sensor is that, when it is attached to a building frame or the like, the sensor fiber expands and contracts due to the deformation of the frame. Since the wavelength of the (Bragg reflection) light changes, this change is measured and analyzed to grasp the magnitude of the expansion and contraction of the lattice, that is, the state of the distortion of the frame or the like. According to this Bragg grating sensor, it is possible to increase the number of measurement points by changing the grating length for each measurement point, and it is possible to configure a sensor using only sensor fibers, and since the grating can be processed with an excimer laser, it is rich in mass productivity. .

However, since the method of processing the optical fiber provided with the grating is a special technique, it is still expensive at present, and no practical application of the Bragg grating sensor to strain measurement has been made. Also, the measurement and evaluation device used simultaneously with the Bragg grating sensor is very expensive and is not suitable for general use in the construction field.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to monitor an object to be searched inexpensively by using an inexpensive optical fiber and utilizing a phenomenon that transmitted light disappears due to its breakage. It is to provide a system that can do it.

[0009]

In order to achieve the above object, a monitoring system for an object to be searched using an optical fiber according to the present invention comprises an optical fiber bent in a U-shape on a linear core material. A linear sensor is formed by attaching the leading portion while sequentially shifting the core in the axial direction of the core material, and the linear sensor is arranged in a mesh or vertical or horizontal direction on an exploration target such as a mountain, a ground, or a structure, and the lines are arranged. In this configuration, the optical fiber of the shape sensor is connected to a monitoring device that specifies a damaged position of the optical fiber by utilizing a phenomenon that transmitted light disappears due to breakage.

Since an inexpensive optical fiber for communication is used, the linear sensor itself is inexpensive. In addition, since a monitoring device that identifies the damage position of the optical fiber using the phenomenon that transmitted light disappears due to the breakage of the optical fiber is used, the monitoring device also uses light polarization, interference, back scattering phenomenon, etc. It can be configured at a lower cost than a monitoring device.

In addition, a large number of U-shaped bent optical fibers are attached to a linear core material while the leading portions thereof are sequentially shifted in the axial direction of the core material to constitute a linear sensor. The leading portion of the fiber is held at a fixed position in the axial direction of the core material, and does not fluctuate.
Therefore, a large number of optical fibers can be handled collectively as one linear sensor, and a large number of optical fibers can be laid at a predetermined pitch simply by laying an appropriate number of these linear sensors as a unit. Therefore, the laying is very easy compared to the case where the individual optical fibers are laid independently.

Further, since the above-mentioned linear sensors are arranged in a mesh shape or vertically and horizontally on an object to be searched, such as a mountain, a mountain, or a structure, a wide area can be measured, and the location of the change of the object to be searched can be determined. It can be detected two-dimensionally. In addition, since the monitoring device can be placed in a remote place that is convenient for monitoring away from the object to be searched, it is possible to easily perform maintenance and inspection of a structure that is difficult to perform daily inspection such as a collapse of a tunnel.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment. The optical fiber can be used as a damage detection sensor because the light intensity does not change midway even when the measurement range becomes long. The present invention utilizes a phenomenon in which the intensity of light propagating when an optical fiber is damaged and broken is greatly reduced and disappears.

FIG. 1 shows a state in which a linear sensor 2 is arranged in a mesh shape or vertically and horizontally on a mountain 1 to be searched. These linear sensors 2 are, as shown in FIG.
A number of U-shaped optical fibers 4 are bent into their leading portions 5.
Are attached while being shifted in the axial direction of the core material 3 sequentially. As shown in FIG. 1, each optical fiber 4 of these linear sensors 2 is connected to a monitoring device 6 that specifies a damaged position of the optical fiber by utilizing a phenomenon that transmitted light disappears due to breakage.

The monitoring device 6 identifies a position such as a landslide from an optical fiber that has been broken and has become non-translucent. The principle of the search performed by the monitoring device 6 is that, for example, as shown in FIG. 3, the linear sensor 2 having the optical fibers 4 </ b> A to 4 </ b> D whose head portions 5 are sequentially shifted has a breakage 7 at a position as shown in the drawing. 4A and 4B of the optical fibers 4A to 4D are cut, and the remaining optical fibers 4C and 4D remain without being cut. Accordingly, although light is not transmitted through the optical fibers 4A and 4B, light is transmitted through the optical fibers 4C and 4D, and thus damage occurs between the leading portion 5 of the optical fiber 4B and the leading portion 5 of the optical fiber 4C. It is understood that.

FIGS. 4 to 7 show examples of the configuration of the linear sensor 1 which is advantageous in actual production. An inexpensive optical fiber for communication is used as the material of the optical fiber 4 and a rubber striated body having a diameter of 4.0 mm is used as the material of the inexpensive core material 3. However, as the core material 3, a material to which a coating material or the like can be attached by viton can be used.

As shown in FIG. 4, an optical fiber 4
An insertion hole 8 for passing through is formed in the diameter direction. The insertion holes 8 determine the positions of the leading portions of a large number of optical fibers 4 belonging to the core material 3, and these insertion holes 8 are formed at a predetermined pitch so as to draw a spiral locus 9 as shown in FIG. It can also be provided.

FIG. 7A is a plan view of the core material 3 provided with the through holes 8. FIG. 7B is a cross-sectional view of the core 3 in the insertion hole 8. In the example shown in FIG. 7, the length L of the core material 3 is 1.5 to 2.0 m,
The pitch P of the insertion holes 8 in the axial direction is 10 cm. Further, the diameter of the insertion hole 8 is 1.0 mm, and the insertion holes 8 are formed at intervals of 10 cm as shown in FIG.
Are shifted by 30 °. By displacing the perforated positions in this way, even when a large number of optical fibers 4 are assigned, the processing and handling become easy.

The optical fiber 4 is passed through each insertion hole 8 so that the core material 3
As shown in FIG. 5, the head portion 5 is sequentially shifted at a predetermined pitch P in the axial direction of the core material 3 as shown in FIG. While keeping the optical fibers aligned in the axial direction, the surface is coated with a rubber or epoxy resin material to complete the sensor. Accordingly, each of the optical fibers 4 has a specific measurement range, and serves as a sensor for monitoring a specific position of the one-dimensional member.

Therefore, based on the principle described with reference to FIG. 3, it is possible to specify a damaged position, that is, a landslide portion generated in the hill 1 to be searched in FIG. 1 by cutting the optical fiber 4.

The advantage of this search system is that the linear sensor 2 and the monitoring device 6 using an inexpensive communication optical fiber can perform two-dimensional monitoring of a damage position such as a landslide. In addition, since the monitoring device 6 can be placed in a place that is convenient for monitoring away from the exploration target,
Maintenance and inspection of structures that are difficult to perform daily inspections such as tunnel collapse can be easily performed, and a major accident (disaster) can be prevented.

In the above embodiment, the mountain 1 to be searched is
In FIG. 8, a large number of linear sensors 2 are arranged in a mesh or vertical and horizontal directions. As shown in FIG. 8, a first linear sensor 21 is horizontally folded in a single-stroke shape, and a second linear sensor 21 is vertically folded in a single-stroke shape.
May be arranged in a form crossing the mountain 1. By arranging the linear sensors 2 continuously and vertically at predetermined intervals in this way, it is possible to perform a wide-area measurement instead of one-dimensional measurement such as displacement meter measurement, and to specify the coordinate values. Thus, it is possible to detect the location of the change in the ground. In the above-described embodiment, the mountain 1 has been described as an example of the search target. However, the present monitoring system is not limited to this, and may be applied to a mountain or a structure.

[0023]

As described above, according to the monitoring system of the present invention, since the inexpensive optical fiber which has not been subjected to special processing is used, the linear sensor itself is inexpensive. In addition, since the damage position of the optical fiber is specified by using the phenomenon that transmitted light disappears due to breakage, the monitoring device is configured at a very low cost as compared with those using light polarization, interference, back scattering phenomenon, etc. be able to.

Also, since a large number of U-shaped bent optical fibers are attached to the linear core material while the leading portions thereof are sequentially shifted in the axial direction of the core material, the linear sensor is constituted. Optical fibers can be handled collectively as one linear sensor, and installation is easy.

Further, since the linear sensors are arranged in a mesh shape or vertically and horizontally on an object to be searched, such as a mountain, a mountain, or a structure, a wide area can be measured.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a monitoring target monitoring system using an optical fiber according to the present invention.

FIG. 2 is a perspective view showing a part of a linear sensor used in the monitoring system of FIG. 1;

FIG. 3 is a plan view showing a state in which a linear sensor is damaged in the middle.

FIG. 4 is a plan view showing a core material which is a component of the linear sensor.

FIG. 5 is a plan view showing a linear sensor.

FIG. 6 is a perspective view showing a core material which is a component of the linear sensor and an insertion hole formed in the core material.

FIGS. 7A and 7B show a core material which is a component of the linear sensor. FIG. 7A is a plan view of the core material, and FIG.

FIG. 8 is a diagram showing another embodiment of the monitoring system of the present invention.

FIG. 9 is a diagram showing a conventional landslide search system.

[Explanation of symbols]

 Reference Signs List 1 mountain 2 linear sensor 3 linear core material 4 optical fiber 5 head part 6 monitoring device 7 breakage 8 insertion hole 9 locus

Claims (1)

[Claims] 1. A linear sensor comprising a plurality of U-shaped bent optical fibers attached to a linear core material while sequentially shifting the leading end thereof in the axial direction of the core material. It is arranged in a mesh or vertical or horizontal direction on the object to be searched, such as a mountain, a mountain, or a structure. A monitoring system for an exploration target using an optical fiber, which is connected to a monitoring device to be specified.