JP2007101274A - Fiber optic state change detection apparatus and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect displacements at a plurality of positions easily at low cost with less variation in loss with respect to displacement and stably and prevent a break in an optical fiber. <P>SOLUTION: The state change detection apparatus 69 has a rotation mechanism for providing a fiber optic cable 5 within a metallic tube 4 with bending when a block 8 is displaced beyond a predetermined displacement. The displacement between the block 8 and an anchor (not shown) anchoring the state change detection apparatus 69 when a state change occurs in a slope 3 is provided to a loss generation section 70 through a rod 7 and a link mechanism. The rotation of the loss generation section 70 provides the metallic tube 4 and the fiber optic cable 5 therewithin with bending. An OTDR is used for the measurement of a loss in light caused by the bending of the fiber optic cable 5. From the measurement result of the loss in light by the OTDR, the presence or absence of state changes in the slope 3 and the location of the occurrence of state changes are detected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technique for detecting a change in slope / slope, for example, detecting the presence or absence of a change in a river bank slope due to rainfall or water increase, and a change position.

  In recent years, sensors that use optical fiber as a means to monitor and manage river embankments, etc. to predict the collapse of river embankments due to rainfall and water increase and the collapse of rock walls on mountain roads in advance. Attention has been paid.

  In other words, an optical fiber having features such as non-inductive, explosion-proof, and corrosion resistance is promising as a component of the above-described disaster prevention system, as well as being capable of online measurement over a long period of time as a sensor function. Many proposals have been made as optical fiber sensors for measuring displacement of a monitoring object using various characteristics of optical fibers.

  For example, Patent Document 1 discloses an optical fiber sensor (hereinafter referred to as “No. 1”) that detects the presence or absence of displacement, deformation, collapse, etc. of an object to be monitored from the loss of light due to breakage or bending of the optical fiber, and grasps the occurrence location. 1). In other words, the first conventional example changes, for example, the deformation of a dangerous point such as an inclined surface along a road or the like to a deformation or breakage of an optical fiber by changing the deformation of the dangerous point or the like, and the like. For the purpose of observing more safely and quickly, an optical fiber holding portion is provided for each of a pair of connecting members separately connected to a pair of adjacent retaining wall blocks as monitoring objects existing at different positions. These optical fiber holders hold different positions in the longitudinal direction of the optical fiber and come close to each other, and the optical fiber undergoes deformation or breakage of the optical fiber due to the relative displacement between the connecting members. The presence or absence of etc. is detected.

  Also, in Patent Document 2, two U-shaped metal fittings are prepared, one is fixed to the pile and the other is fixed to the girder so that the cuts overlap, and the overlapping cuts are configured through the optical fiber cable to cause relative displacement. Describes a device (hereinafter referred to as a second conventional example) that detects a displacement of a detection target and a position where the displacement is generated from a loss of light. That is, this second conventional example uses a plurality of piles and a girder and an optical fiber laid along the plurality of piles. A relative displacement occurs between the piles and the girder, and the optical fiber is deformed to output light. In a device that detects the occurrence of slope failure by detecting the decay, as a displacement detection structure, U-shaped brackets with cuts on both sides are fixed so that the cuts overlap on both piles and girders. Through optical fiber, when relative displacement occurs due to slope failure, the optical fiber is deformed by bending, and it is possible to detect displacement reliably with a simple optical fiber holding structure. Yes.

JP 2001-99755 A Japanese Utility Model Publication No. 6-18923

  However, in the first conventional example, when the deformation of the monitoring object is large, it is assumed that the optical fiber does not stay in the deformation but breaks, and when the optical fiber is broken in this way, In order to enable detection again, it is necessary to reconstruct the optical fiber cable. In addition, when a large loss occurs due to the displacement at a certain location, it becomes difficult to detect two or more locations.

  Further, in the second conventional example, as in the first conventional example, if the deformation of the detection target is large, the optical fiber may be broken. There is a problem that construction is necessary, and when a large loss occurs due to displacement at a certain location, detection at other locations becomes difficult. In addition, in the second conventional example, since there is no U-shaped fitting adjustment / positioning means in the longitudinal direction of the optical fiber cable, variation in the loss of output light due to deformation of the optical fiber occurs. For this reason, when the threshold value of loss is set, there remains a big problem that accurate detection becomes difficult.

  The object of the present invention is to reduce the loss variation with respect to the displacement with a simple and low-cost configuration, to stably detect the displacement at a plurality of locations, and to prevent the optical fiber from being broken again. An object of the present invention is to provide an optical fiber type deformation detection device and system that can be used.

  In order to solve the above-described problem, in the present invention, the deformation detection device is provided with a mechanism that holds the longitudinal direction of the optical fiber cable at at least two points and a mechanism that rotates according to the displacement of the load, and holds the optical fiber cable. In addition, the rotation mechanism is provided with a bend, a stopper that prevents the rotation mechanism from rotating until the optical fiber cable is broken, and a positioning means for positioning a position where the rotation mechanism bends the optical fiber cable.

  As a result, a simple basic configuration of a mechanism for holding the optical fiber cable and a mechanism for bending the optical fiber cable by rotating according to the displacement of the load, variation in loss with respect to the displacement of each deformation detecting device by the positioning means. Since the optical fiber cable can be prevented from being broken by the stopper, the displacement and the like at a plurality of locations can be detected stably.

  Thus, in the optical fiber type deformation detection device of the present invention, in the optical fiber type deformation detection device for monitoring the deformation of the monitored object by the loss of light propagating through the optical fiber cable, the optical fiber cable and the light By holding at least two points in the longitudinal direction of the fiber cable, the cable fixing base to which the optical fiber cable is fixed, and the cable fixing base can be rotated in a direction orthogonal to the longitudinal direction around a predetermined rotation axis. After the one end side is connected to a load that moves due to the deformation of the monitored object and rotates to a predetermined angle in the orthogonal direction by the movement of the load, the other end side contacts the optical fiber cable. A loss generating member that generates a loss by bending the optical fiber cable, and prevents the loss generating member from rotating beyond the predetermined angle. A stopper for the loss generating member between the holding points of the cable fixing base of said two points and having a positioning means for positioning a position abutting to the optical fiber cable.

  According to this configuration, the optical fiber cable is bent by rotating according to the load in which the loss generating member moves due to the deformation of the monitored object while holding the longitudinal direction of the optical fiber cable at at least two points by the cable fixing base. Therefore, the loss of light is generated, so that it is possible to detect the deformation of the monitored object by monitoring the loss of light. In addition, since the loss generating member has a stopper that prevents the loss generating member from rotating beyond a predetermined angle, it becomes possible to effectively prevent the optical fiber cable from being bent or broken more than necessary by setting the predetermined angle. Furthermore, since it has positioning means for positioning the position where the loss generating member comes into contact with the optical fiber cable, it is possible to suppress variations in loss with respect to the displacement for each deformation detecting device, so that the detection of displacement or the like at a plurality of locations can be performed stably. be able to.

The predetermined angle is an angle in a range where the loss generating member bends the optical fiber cable but does not break the optical fiber cable.
According to this configuration, it is possible to reliably prevent the optical fiber cable from being broken.

The positioning means can be composed of a compression spring and a spacer attached to the rotating shaft from both sides of the loss generating member.
According to such a configuration, the positioning means can be easily configured by the compression spring and the spacer, and variation in loss can be sufficiently suppressed.

The loss generating member may be connected to the load by a connecting member via a link mechanism.
According to this configuration, it becomes possible to convert the displacement of the load into the rotational operation of the loss generating member with high sensitivity.

Further, the loss generating member has a first rotation radius consisting of a length from the rotating shaft to a position where it abuts on the optical fiber cable, and a length from the rotating shaft to a position connected to the load. It is possible to make it possible to change the second turning radius mutually.
According to such a configuration, for example, the displacement and load until the optical fiber cable is bent can be changed by shifting the position of the rotating shaft at the design stage, so that the deformation detecting device can be downsized. become.

On the other hand, a plurality of the above-described optical fiber type deformation detection devices are provided at a predetermined interval of the optical fiber cable constituting at least one line, and a plurality of loads are provided at a predetermined interval of the monitoring object. And an optical fiber type abnormality detection system comprising an optical monitoring device for monitoring a loss of light propagating through the optical fiber cable constituting the at least one line.
According to such a configuration, the variation in loss with respect to the displacement is small with a simple and low-cost configuration, and it is possible to stably detect the displacement and the like at a plurality of locations and to prevent the optical fiber from being broken again. An optical fiber deformation detection system that can be used can be provided.

  According to the present invention, with a simple and low-cost configuration, variation in loss with respect to displacement is small, and it is possible to stably detect displacement and the like at a plurality of locations, and to prevent the optical fiber from being broken again. An optical fiber type deformation detection device and system that can be used can be provided.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. Here, in the accompanying drawings, the same reference numerals are given to the same members, and duplicate descriptions are omitted. The embodiment of the invention is a particularly useful embodiment in which the present invention is implemented, and the present invention is not limited to the embodiment.

  FIG. 1 is a diagram showing a basic configuration of an optical fiber type deformation detection system according to an embodiment of the present invention. 2A and 2B are external views of the deformation detection unit used in the optical fiber type deformation detection system. FIG. 2A shows the overall configuration of the deformation detection unit, and FIG. 2B shows the main part of the deformation detection unit. Enlarged view. 3 is an external view showing a mechanism part of the deformation detection device used in the deformation detection unit, FIG. 4 is an enlarged side view showing a main part of the mechanism part of the deformation detection device of FIG. FIG. 6 is a cross-sectional view of the deformation detection device, and FIG. 6 is a view for explaining a method of fixing the optical fiber cable to the deformation detection device. FIG. 7 is a diagram showing a state in which the loss generation unit bends the optical fiber cable in the deformation detection device, and FIG. 8 is a diagram showing a rotation operation of the loss generation unit in the deformation detection device.

  As shown in FIG. 1, the optical fiber type deformation detection system according to the present embodiment is a light in which the deformation detection unit 6 constitutes one line along the slope 3 of the river embankment that is an object to be monitored. A plurality of fiber cables 5 are provided at predetermined intervals. Each deformation detection unit 6 includes a deformation detection device 69, and each of the deformation detection devices 69 is connected to a block 8 as a load. Further, the optical fiber type deformation detection system according to the present embodiment includes an OTDR (not shown in FIG. 1) as an optical monitoring device that monitors the loss of light propagating through the optical fiber cable 5. The deformation of the slope 3 of the river bank due to the water increase is regarded as a displacement between the block 8 in each deformation detection unit 6 and an anchor (not shown in FIG. 1) for fixing the deformation detection device 69, and the displacement is predetermined. When the threshold value is exceeded, the deformation of the slope 3 is detected.

  In FIG. 1, reference numeral 1 denotes a river, 2 denotes a river bank, and 3 denotes a slope of the bank. 4 is a metal tube, 5 is an optical fiber cable, and 6 is a deformation detection unit.

  As shown in FIGS. 2A and 2B, the deformation detection unit 6 includes a deformation detection device 69 that detects displacement, and a method of the bank 1 that uses the deformation detection device 69 as a monitoring object. An anchor 66 for fixing to the surface 3, a block 8 for transmitting the displacement of the slope 3 to the deformation detector 69 as a load that moves due to the deformation of the slope 3 as a monitoring object, and a deformation detector 69 It is comprised from the rod 7 which connects the block 8. FIG. Then, a pedestal portion 72A of a cable fixing base 72 (to be described later) of the deformation detecting device 69 is used by being fixed with bolts in a state where it is placed on a pedestal 66A of a fixing anchor 66. The deformation detection device 69 is provided with a metallic cover 75 and the like. As described above, each of the deformation detection units 6 includes the deformation detection device 69, and each deformation detection device 69 includes the link mechanism 71 shown in FIGS. 4 and 5. As shown in FIGS. 1 and 2, the rod 7 is connected to one end side, and the rod 7 is connected to the other end side of the block 8.

  In order to detect the deformation, it is necessary to bend the optical fiber cable 5 when a predetermined displacement is exceeded to generate a light loss. In the present embodiment, the deformation detection device 69 has a mechanism for bending the optical fiber cable 5 in the metal tube 4 when the block 8 is displaced beyond a predetermined displacement. As shown, the use of a rotating mechanism as the mechanism for imparting this bending is a major feature of the present invention. That is, the displacement between the block 8 at the time of deformation of the slope 3 and the anchor 66 for fixing the deformation detection device 69 is given to the loss generation unit 70 via the rod 7 and the link mechanism 71, and the loss generation unit 70 rotates. Thus, the metal tube 4 and the optical fiber cable 5 inside thereof are bent. Although waterproofing or the like in the deformation detection device 69 is not required, a cover such as a metallic cover 75, which will be described later, is attached and used even when buried in the lower part of the slope 3 of the levee 2 so that earth and sand do not enter.

  For the measurement of light loss, an optical time domain reflectometer (OTDR) 12 as an optical monitoring device shown in FIG. 12 to be described later is used. From the measurement result of the light loss by the OTDR 12, the presence / absence of deformation on the slope 3 and the occurrence location of the deformation are detected. It is possible to install any number of deformation detection devices 69 over a tens of kilometers per line. However, due to restrictions on the dynamic range of the OTDR 12, the number of deformation detection devices 69 that can occur at the same time can be detected. It is a deformation of. In addition, when a change is detected, the observer goes to the place where the change occurred, and repairs, monitors, or adjusts it as a countermeasure to repair the slope 3 and prevent a disaster. In addition, as will be described later, it is possible to perform monitoring again by returning the bent metal tube 4 and the optical fiber cable 5 (removing the bending as much as possible).

  Next, the deformation detection device 69 will be described in detail with reference to FIGS. 3 to 8, the deformation detecting device 69 shows only the configuration of the main part from which the cover such as the metallic cover 75 is removed. The deformation detection device 69 is mainly composed of a metal plate and a rod (shaft), and as shown in FIGS. 3 to 5, the optical fiber cable 5 (the metal tube 4 having an inside thereof, hereinafter simply referred to as an optical fiber). The optical fiber cable 5 is fixed at two points by holding the longitudinal direction of the cable 5 (which may be referred to as a cable 5), and the cable fixing base 72 is orthogonal to the longitudinal direction about the rotation shaft 74. The other end side is connected to the optical fiber cable 5 by being connected to a block 8 as a load and rotating to a predetermined angle in the above-mentioned orthogonal direction by the movement of the block 8 as a load. After the contact, the loss generating part 70 as a loss generating member for bending the optical fiber cable 5 to generate a loss, and the loss generating part 70 rotate beyond the predetermined angle. As a positioning means for positioning the position where the loss generating portion 70 between the stopper 73 for preventing this and the two holding points of the cable fixing base 72 comes into contact with the optical fiber cable 5, both sides of the loss generating portion 70 are arranged on the rotary shaft 74. Compression springs 78 and spacers 76 respectively attached thereto.

  The cable fixing base 72 includes a pedestal portion 72A and two cable fixing members 72B and 72C that stand upright at a predetermined interval on the pedestal portion 72A. The cable fixing members 72B and 72C of the cable fixing base 72 are formed with notches 723 and holding portions 723b and 723c for holding the optical fiber cables 5 through the upper portions thereof. The notches 723 and 723 are formed for passing the optical fiber cable 5, and the drop portions 723 b and 723 c are formed for holding and fixing the optical fiber cable 5 after dropping. The cable fixing members 72B and 72C of the cable fixing base 72 have through holes 72b and 72c for fixing the optical fiber cable 5 dropped into the dropping portions 723b and 723c, respectively, as shown in FIGS. Is formed. As will be described later, the through holes 72b and 72c are inserted into the optical fiber cable 5 dropped into the dropping portions 723b and 723c and fixed to the through holes 72b and 72c, as will be described later. It is formed to hold and fix securely.

  In the space between the cable fixing members 72B and 72C of the cable fixing base 72, a rotating shaft 74 having both ends fixed to the cable fixing members 72B and 72C is provided in the center slightly above the center. A loss generating portion 70 is rotatably supported on the shaft 74. As shown in FIG. 5, the loss generation unit 70 is formed of a substantially rectangular plate material slightly smaller than the cable fixing members 72 </ b> B and 72 </ b> C, and is supported by the rotary shaft 74 at the center slightly above the center. .

  As shown in FIG. 4, the distance between the cable fixing base 72 and the loss generating portion 70 is set in the rotating shaft 74 so that the spacer 76 and the compression spring 78 are sandwiched from both sides of the loss generating portion 70. By applying a compressive force that does not hinder the rotation of the loss generating part 70, the distance between the cable fixing base 72 and the loss generating part 70 is always kept constant in such a manner that the loss generating part 70 is pressed down. Thereby, since the variation of the loss in each deformation detection device 69 is suppressed, the deformation can be accurately detected even when a loss threshold for setting the deformation is set. In this embodiment, as shown in FIGS. 3, 4, and 7, the loss generating unit 70 is located closer to the cable fixing member 72 </ b> B than the center of the rotating shaft 74 between the cable fixing members 72 </ b> B and 72 </ b> C. It is supported by. A spacer 76 is incorporated between the cable fixing member 72B and the loss generating part 70 of the rotating shaft 74, and a compression spring 78 is incorporated between the cable fixing member 72C and the loss generating part 70. With this configuration, as shown in FIG. 7, the optical fiber cable 5 is bent more greatly between the cable fixing member 72 </ b> B and the loss generation unit 70 due to the rotation of the loss generation unit 70. As a result, since a larger loss occurs between the cable fixing member 72B and the loss generation unit 70, it is known that the loss generation and the detection sensitivity are improved, and the deformation can be detected more reliably.

  As shown in FIGS. 3 and 5, a link mechanism 71 is provided on one end side (the lower end side in the height direction) of the loss generating unit 70. The loss generating unit 70 is connected to the rod 7 as a connecting member via the link mechanism 71 and is connected to the block 8 as a load. A notch 703 is formed on the other end side (the upper end side in the height direction) of the loss generation unit 70. The notch 703 is formed at a position corresponding to the notch 723 of the cable fixing members 72 </ b> B and 72 </ b> C above the loss generating part 70. This notch 703 is formed by cutting from the side opposite to the notch 723 of the cable fixing members 72B and 72C [see FIG. 9B] to a position corresponding to the rotating shaft 74 as shown in FIG. Has been. As the loss generating part 70 rotates, the loss generating part 70 abuts on the optical fiber cable 5 at the bottom of the notch 703 (position corresponding to the rotating shaft 74), and further rotates to press and bend to generate loss. It is supposed to let you. The notch 703 also has a meaning of providing an insensitive area with respect to a minute displacement of the block 8 as a load.

In addition, a substantially columnar stopper 73 is provided in the gap between the cable fixing members 72B and 72C of the cable fixing base 72. Both ends of the cable fixing members 72B and 72C are held by the cable fixing members 72B and 72C. As described above, the stopper 73 prevents the loss generating unit 70 from rotating beyond the predetermined angle. As shown in FIGS. 5 and 6, movement guide grooves 79 (not shown in FIGS. 3 and 4) of the stopper 73 are formed in the cable fixing members 72B and 72C of the cable fixing base 72, respectively. The stopper 73 can be fixed at a desired height position in the movement guide groove 79.
In addition, four fixing holes 72a for fixing to the base 66A of the fixing anchor 66 with bolts are formed in the base 72A of the cable fixing base 72.

  Referring again to FIG. 1, the deformation detection units 6 are provided at regular intervals along the longitudinal direction of the slope 3 of the dike 2. That is, each deformation detecting device 69 is fixed by anchors 66 [see FIG. 2 (a)] at regular intervals along the longitudinal direction of the slope 3 of the levee 2, and the block 8 is below the slope 3 The deformation detection device 69 and the rod 7 are connected to each other.

  At this time (in the initial state), as shown in FIGS. 5 and 8, the optical fiber cable 5 is positioned at the tip of the notch 703 of the loss generating portion 70 in each deformation detecting device 69. As shown, the notches 723 and 723 of the notches 723 and 723 of the cable fixing base 72 are aligned on the same line. Further, in this initial state, as shown in FIG. 5, the rear side surface of the loss generating portion 70 and the rear side surface of the cable fixing base 72 are on the same plane.

  As the slope 3 is deformed, the block 8 shown in FIG. 1 is displaced, so that the displacement is applied to the load point of the loss generating unit 70 in the deformation detecting device 69. That is, for example, as shown in FIG. 1, when a crack 32 is generated on the slope 3 of the dike 2, the block 8 connected to the deformation detecting device 69 installed at the location where the crack 32 is generated is displaced. Displacement is loaded on the loss generation unit 70 via the rod 7 and the link mechanism 71. As shown in FIG. 8, the loss generating unit 70 loaded with this displacement rotates around the rotating shaft 74, and the bottom of the notch 703 of the loss generating unit 70 is attached to the cable fixing base 72 by the clamping screw described above. It contacts the fixed optical fiber cable 5. This is due to the predetermined displacement, and no loss occurs. After that, the loss generating unit 70 in contact with the optical fiber cable 5 continues to rotate around the rotation shaft 74, and as shown in FIGS. 7 and 8, the cable fixing base 72 and the loss generating unit 70 (of the notch 703 of the notch 703. Shear deformation is applied to the optical fiber cable 5 with respect to the bottom. This shear deformation causes a loss of light in the optical fiber cable 5. As shown in FIGS. 3, 4, 7, and 8, the loss of light due to the shear deformation does not become excessive or the loss generating portion 70 does not rotate until the optical fiber cable 5 is broken. The fixed base 72 is provided with a stopper 73 that restricts the rotation of the loss generating part 70. The loss generating unit 70 stops rotating by coming into contact with the stopper 73. At this time, the light propagating through the optical fiber cable 5 has a plurality of detectable magnitudes, for example, a loss of 1 to 2 dB. By measuring these using the OTDR 12, the slope 3 of the dike 2 is measured. The presence or absence of deformation and the location of deformation are detected. In the optical fiber type deformation detection system of the present embodiment, the mounting interval of each deformation detection device 69 in the optical fiber cable line is set to 1 m in order to improve the measurement sensitivity.

  Now, in the optical fiber type deformation detection system of this embodiment, the variation in loss in each of the deformation detection devices 69 provided at a predetermined interval of the optical fiber cable 5 constituting one line is different from each other. Depends on the variation in the distance between the cable fixing base 72 and the loss generating unit 70 in the shape detecting device 69. Therefore, in the optical fiber type deformation detection system of the present embodiment, the distance between the cable fixing base 72 and the loss generation unit 70 is such that the spacer 76 and the compression spring 78 are moved from both sides of the loss generation unit 70 as shown in FIG. The cable fixing base 72 and the cable fixing base 72 are pressed in such a manner that the loss generating part 70 is pressed by being inserted into the rotating shaft 74 so as to be sandwiched, and applying a compressive force that does not hinder the rotation of the loss generating part 70 in the longitudinal direction of the rotating shaft 74. The distance from the loss generation unit 70 is always kept constant. Thereby, since the variation of the loss in each deformation detection device 69 is suppressed, the deformation can be accurately detected even when a loss threshold for setting the deformation is set.

  Since the loss generating unit 70 applies the displacement of the load point to the optical fiber cable 5 by the rotation mechanism, the rotation radius 1 (the loss is generated from the rotation shaft 74 shown in FIG. 8) by shifting the fixed position of the rotation shaft 74 at the design stage. The length until the position where the portion 70 contacts the optical fiber cable 5) and the rotation radius 2 (the length from the rotating shaft 74 to the load point, that is, the position where the loss generating portion 70 is connected to the load) It is possible to change. As a result, the displacement and load until the bending is caused can be changed, so that the deformation detecting device 69 can be downsized.

  In the optical fiber type deformation detection system of this embodiment, the optical fiber cable 5 is housed in a metal tube 4 as a protective tube that can be plastically deformed. Thereby, the effect which further prevents the fracture | rupture of the optical fiber cable 5 by a deformation | transformation is also acquired. In addition, there is an effect of protecting the optical fiber cable 5 from an external force after installation, and the optical fiber cable 5 can be prevented from being damaged by the external force.

  Next, a method for actually laying the deformation detection unit 6 along the slope 3 of the dike 2 will be described. FIGS. 9A and 9B are diagrams for explaining a method of installing the optical fiber cable in the deformation detection device, where FIG. 9A shows before installation, FIG. 9B shows during installation, and FIG. 9C shows after installation. FIG. 10 is an external view of a state where the rotation detecting jig is attached to the deformation detecting device 69 as viewed from the rear in the actual laying method.

  As described above, the deformation detection unit 6 includes the deformation detection device 69 that detects the displacement, the anchor 66 for fixing the deformation detection device 69 to the slope 3 of the bank 2 of the river 1, The block 8 transmits the displacement to the deformation detection device 69, and the rod 7 connects the deformation detection device 69 and the block 8.

  First, the anchor 66 is installed by being embedded in the slope 3 of the dike 2 so that the base 66A of the anchor 66 is horizontal, and the base 72A of the cable fixing base 72 of the deformation detecting device 69 is fixed. The anchor 66 is mounted with bolts using the four fixing holes 72a in a state of being placed on the pedestal 66A. Next, the installation of the optical fiber cable 5 to the cable fixing base 72 in each deformation detecting device 69 is illustrated from the state in which the loss generating portion 70 shown in FIG. 9 (b), the loss generating part 70 is tilted backward, the optical fiber cable 5 is passed through the notches 723, 723 of the cable fixing base 72 from the rear, and the cut is made as shown in FIG. 9 (c). This is done by dropping the optical fiber cable 5 into the dropping portions 723b and 723c of the notches 723 and 723. Thereby, the optical fiber cable 5 can be easily passed through the deformation detection device 69. And installation of the optical fiber cable 5 to the cable fixing base 72 in each deformation | transformation detection apparatus 69 provided with every predetermined space | interval of the optical fiber cable 5 which comprises one line is first carried out to each loss generating part. 70 is tilted backward, and the optical fiber cable 5 is passed through the notches 723 and 723 of each cable fixing base 72 from the rear. Thereby, since it is not necessary to pass the optical fiber cable 5 for each of the deformation detection devices 69, workability is greatly improved in construction such as installation on the slope 3 in the bank 2 of the river 1.

When the installation of the optical fiber cable 5 is completed, one side of the optical fiber cable 5 is fixed to the cable fixing base 72. That is, the clamping screw is inserted into and fixed to the optical fiber cable 5 only in one of the through holes 72b and 72c formed in the cable fixing members 72B and 72C of the cable fixing base 72 described above. Note that a clamping screw or the like may be inserted into both of the through holes 72b and 72c to fix both sides of the optical fiber cable 5 to the cable fixing base 72. In this embodiment, however, the optical fiber cable 5 is bent. In order to reduce the load required for this, only one side was fixed with a clamping screw. In this state, as shown in FIG. 8, the loss generating unit 70 is set to an initial state. Then, as shown in FIG. 10, a rotation preventing jig 69b of the loss generating unit 70 is attached to the deformation detecting device 69 so that the loss generating unit 70 does not rotate. Thereafter, the block 8 is installed at a predetermined position, that is, at a lower portion of the slope 3, and the block 8 is connected to the loss generating unit 70 by the rod 7. Specifically, the rod 7 is connected to a link mechanism 71 coupled to the loss generating unit 70. When the loss generating unit 70 and the block 8 can be connected through the rod 7 and the link mechanism 71 in this way, the rotation preventing jig 69b is removed from the deformation detecting device 69, and the metallic cover 75 or the like is attached. The installation of the state detection unit 6 is completed. FIG. 11 is an external view of a state in which the cover is attached to the deformation detection device 69 as viewed from the right side. As shown in FIG. 11, when the deformation detection device 69 is actually used, the right side of the deformation detection device 69 is covered with a metallic cover 75. The metallic cover 75 is formed with a protrusion 75a so as not to disturb the movement of the link mechanism 71. Although not visible in FIG. 11, the left side and top surface of the deformation detection device 69 are also covered with a metallic cover. The reason why the deformation detection device 69 is covered with the metal cover in this way is to prevent earth and sand from entering the cable fixing base 72 and making detection difficult.

  Here, a deformation detection method using the OTDR 12 in the optical fiber deformation detection system of the present embodiment will be described. FIG. 12 is a functional block diagram showing the overall configuration of the optical fiber type deformation detection system of the present embodiment.

  Now, in the optical fiber type deformation detection system according to the present embodiment, a plurality of the above-described deformation detection units 6 are arranged on the slope 3 of the bank 2 of the river 1 at a predetermined interval. The optical fiber cable 5 is inserted into the shape detection unit 6 and this optical fiber cable 5 is connected to the OTDR 12 as shown in FIG. .

  That is, in the optical fiber type deformation detection system of this embodiment, as shown in FIG. 12, the laser diode (LD) 122 driven by the pulse oscillator 121 outputs an optical pulse, and the optical pulse is a directional coupler. The light enters the optical fiber cable 5 through 123. Backward Rayleigh scattered light or Fresnel reflected light generated by each deformation detection unit 6 in the optical fiber cable 5 returns to the incident end. The light returning to the incident end enters the light receiving element (PD) 124 through the directional coupler 123 and is converted into an electric signal. The converted electric signal is amplified to a required level by the amplifier 125 and then analyzed in the time domain by the analysis processing unit / display unit 126 to display the analysis result. For example, if the deformation detection unit 6 is installed on the slope 3 every 1 m and connected to the OTDR 12 to form a deformation measurement system, the presence / absence of the deformation and the occurrence position can be detected simultaneously. Is possible.

  Next, an extended example of the optical fiber type deformation detection system according to the embodiment of the present invention will be described. As shown in FIG. 13, the optical fiber deformation detection system according to the extended example of the present embodiment includes an observation section 110 and a measurement section 120. The observation section 110 includes an OTDR 12 as an optical monitoring device, a control PC (Personal Computer) 114 connected to the OTDR 12, and an optical channel configured by each optical fiber core wire of the multi-core optical fiber cable 50 connected to the OTDR 12. And an optical channel selector (16 port) 116 for selecting. The measurement section 120 has a branch box 128 for branching the optical fiber core wire of the multi-core optical fiber cable 50 into 16 lines, and each line, that is, the optical fiber cable 5 (see FIG. 1) consisting of one line at predetermined intervals. A plurality of deformation detection units 6 are connected.

  As described above, the measurement by the OTDR 12 is performed by using the multi-core optical fiber cable 50 (having 16 optical fiber core wires) and the optical channel selector (16 port) 116, thereby providing a single measuring device (OTDR 12 and control PC 114). ) Can measure up to 16 lines. Further, since the observation section 110 and the measurement section 120 may be connected (relayed) by one multi-core optical fiber cable 50 (having 16 optical fiber core wires), it is remote from the measurement section 120 (measurement site). It is possible to install an observation section 110 (observation station) on the ground.

  FIG. 14 is a graph showing an example of trace data by OTDR12. By measuring the loss of light caused by the deformation with the OTDR 12, it is possible to detect the occurrence of the deformation and the location where the deformation has occurred. In FIG. 14, the place where the data falls is where the loss of light occurs. Further, the amount of reflected light that has decreased due to deformation from the initial state corresponds to the amount of light loss due to loss occurrence. In the graph of FIG. 14, the amount of reflected light is reduced by about 1.5 dB at a distance of about 485 m, and it can be seen that the occurrence of deformation is detected in the deformation detection unit 6 located at the distance. Thus, in the example shown in FIG. 14, it was found that if a loss of light of about 1.5 dB occurs, the occurrence of deformation and the location where the deformation occurred can be identified from the trace data. Even when only a light loss of less than 1.5 dB occurs, it is sufficient that the falling edge of the data can be recognized and the occurrence of the loss can be confirmed. Therefore, a light loss of about 1.5 dB is preferably generated. Of course, it is desirable, but not limited to this.

  However, in the optical fiber type deformation detection system of this embodiment, as a preferred example, the deformation detection device 69 that generates a light loss of about 1.5 dB with the deformation is designed. FIG. 15 is a diagram illustrating generation of light loss in the optical fiber cable 5 due to the rotation operation of the loss generation unit 70 in the deformation detection device 69, and FIG. 15A illustrates generation of light loss in the optical fiber cable 5. The graph (b) is a diagram showing the operating state of the stopper 73.

  With reference to FIG. 8 in addition to FIG. 15, the loss generating mechanism as this preferred embodiment will be described. Until the predetermined displacement, the optical fiber cable 5 is not bent, and the optical fiber cable 5 is bent when the loss generating portion 70 rotates beyond the predetermined displacement. In addition, a stopper 73 is provided so that the above-described loss does not become about 1.5 dB or more and the optical fiber cable 5 is not broken after bending. That is, as shown in FIG. 8, the loss generating unit 70 rotates from the initial state of (1) to the predetermined displacement state of (2), and at this stage, loss occurs as shown in FIG. 15 (a). do not do. Then, the bending of the optical fiber cable 5 starts from the predetermined displacement state of (2), the loss increases accordingly, and when the loss reaches about 1.5 dB, (3) the stopper 73 is activated. It has become. As shown in FIG. 15 (b), the stopper 73 regulates the loss generating portion 70 so that it cannot rotate any more by contacting the stopper 73, and a predetermined angle at which the loss reaches about 1.5 dB. It is possible to reliably prevent the loss generating part 70 from rotating beyond the range.

  As described above, a loss generation confirmation test was performed to confirm the effect of the deformation detection device 69 designed as a preferred embodiment. FIG. 16 is a block diagram illustrating a test configuration of a loss occurrence confirmation test performed on the deformation detection device 69 according to a preferred example of the present embodiment, and FIG. 17 illustrates the loss occurrence location in the loss occurrence confirmation test. It is a graph which shows the relationship between distance and reflected light quantity. FIG. 18 is a diagram for explaining the relationship between the distance between the stopper and the loss generation part and the loss of light generated in the loss generation confirmation test, and (a) is a diagram between the stopper and the loss generation part. The figure which shows distance, (b) is a graph which shows the relationship between the distance between the stopper in a test result, and a loss generation | occurrence | production part, and the loss of the light to generate | occur | produce.

  In this loss generation confirmation test, in order to give a loss, a load was applied to the loss generation portion 70 to give a displacement of 40 mm. The distance between the cable fixing base 72 and the loss generating part 70 was fixed to 5 mm. Therefore, the magnitude of the loss can be achieved by changing the distance L between the stopper 73 and the loss generation unit 70 when the loss generation unit 70 is in contact with the optical fiber cable 5 as shown in FIG. It was close to the value. As shown in FIG. 16, the optical fiber cable 5 having a total length of 563 m is installed with respect to the deformation detection device 69 so that one is 482 m and the other is 81 m. In the vicinity, the optical fiber cable 5 was accommodated in the metal tube 4 and incorporated. In this loss occurrence confirmation test, the relationship between the distance to the loss occurrence location and the amount of reflected light is shown in FIG. In FIG. 17, the loss is obtained by subtracting the difference between the average of 20 data before and after the fall at the time of loss occurrence and the difference between that at the initial state.

  FIG. 18B shows the measured values in which the distance L between the stopper 73 and the loss generating unit 70 when the loss generating unit 70 is in contact with the optical fiber cable 5 is changed. As shown in FIG. 18B, in order to set the loss to a target value (about 1.5 dB), the distance L between the stopper 73 and the loss generating unit 70 shown in FIG. It turned out that it should just be 8 mm. It was also found that the variation of 10 times remained within ± 0.5 dB (standard deviation: 0.1876 dB). Furthermore, it has been found that the loss occurrence location can be accurately detected from the trace data shown in FIG.

  As the optical fiber cable 5 incorporated in the deformation detecting device 69, for example, a single mode optical fiber cable having a core diameter of about several μm to 10 μm and a diameter of 125 μm can be used.

  As the OTDR 12 that is an optical monitoring device, for example, a high-resolution OTDR having a test light wavelength of 1310 nm, a pulse width of 10 ns or more (as fine as possible), and a spatial resolution of 1 m or more (as short as possible) can be used.

  The optical fiber type deformation detection system of the present embodiment is excellent in workability such as installation / installation on monitoring objects such as various levee bodies such as river embankments, ground slopes, rock bridges, etc. It has a structure that can efficiently act on the bending (bending) of the optical fiber. Further, it has a great advantage that the system can be installed at a relatively low cost. That is, in this embodiment, the deformation detection device 69 can be manufactured at a relatively low cost because of its simple structure, and a relatively inexpensive OTDR 12 is used for measurement. A detection system can be constructed at low cost.

  In FIG. 1, the slope 3 of the dike 2 of the river 1 was mentioned as an example of the monitoring target object of an optical fiber type deformation detection system. When the river water level rises, the infiltration line of the levee rises, and water leakage begins near the bottom of the levee. As a result of this water leakage, changes in the state of the dike near Hojiri appear. According to the optical fiber type deformation detection system of the present invention, this phenomenon can be grasped early and accurately.

  Even if the optical fiber type deformation detection system of the present invention is used for disaster prevention measures in places such as various embankments such as river embankments, ground slopes, rock bridges, etc., since the sensor part is an optical fiber, induction and lightning protection measures There is no need to take

  Furthermore, in the optical fiber type deformation detection system of this embodiment, the optical fiber cable 5 is housed in a metal tube 4 as a protective tube that can be plastically deformed. 72 is fixed. The optical fiber cable 5 is bent by bending the metal tube 4 after the loss generating part 70 contacts the metal tube 4.

  In the invention according to this embodiment, since the optical fiber is housed in a plastically deformable protective tube, the protective tube is restored to its original shape by another external force after the optical fiber is bent due to the bending of the protective tube. Unless this is done, the bending of the optical fiber does not return to its original state, so that the bending of the optical fiber can be reliably detected by the optical monitoring device.

In addition, since the optical fiber is housed in the protective tube, there is no need to worry about disconnection of the optical fiber or the like when performing installation or installation on the monitored object.
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

  For example, in the above-described embodiment, the positioning means is configured by the compression spring 78 and the spacer 76 that are respectively attached to the rotary shaft 74 from both sides of the loss generating portion 70. However, the positioning means is configured by only the compression spring or the spacer. You can also.

  In addition, the loss generation unit 70 is connected to the block 8 as a load by the rod 7 via the link mechanism 71. However, if the displacement can be effectively converted into the rotation operation of the loss generation unit, Other mechanisms and connecting members may be used. Of course, a load other than the block may be used.

  The present invention is the presence or absence of deformation of the river dike slope and the deformation position as long as it is a device, system, method, etc. that can be detected by a switch-like operation of on / off for a predetermined displacement / load. It can be applied not only to devices that detect the above, but also to other devices, systems, methods, etc. for road slope monitoring, landslide detection, seam opening detection of seawalls, intrusion detection (security system) and the like.

It is a figure which shows the basic composition of the optical fiber type deformation detection system which concerns on embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is an external view of the deformation detection unit used for the optical fiber type deformation detection system which concerns on embodiment of this invention, (a) shows the whole structure of a deformation detection unit, (b) is a deformation | transformation detection unit. The main part is shown enlarged. It is an external view which shows the deformation | transformation detection apparatus of FIG. It is a side view which expands and shows the principal part of the deformation | transformation detection apparatus of FIG. It is sectional drawing of the deformation | transformation detection apparatus of FIG. It is a figure for demonstrating the fixing method of the optical fiber cable to the deformation | transformation detection apparatus of FIG. It is a figure which shows the state which a loss generation | occurrence | production part gives a bend to an optical fiber cable in the deformation | transformation detection apparatus of FIG. It is a figure which shows the rotational operation of the loss generation | occurrence | production part in the deformation | transformation detection apparatus of FIG. It is a figure for demonstrating the installation method of the optical fiber cable to the deformation | transformation detection apparatus of FIG. 2, (a) shows before installation, (b) is in the middle of installation, (c) shows after installation, respectively. FIG. 3 is an external view of a state in which an anti-rotation jig is attached as viewed from the rear in the actual laying method of the deformation detection device of FIG. 2. It is the external view which looked at the state which attached the cover to the deformation | transformation detection apparatus of FIG. 2 from the right side. 1 is a block diagram showing an overall configuration of an optical fiber type deformation detection system according to an embodiment of the present invention. It is a block diagram which shows the whole structure of the optical fiber type | mold deformation | transformation detection system which concerns on the extended example of embodiment of this invention. It is a graph which shows the trace data by OTDR in the optical fiber type deformation | transformation detection system which concerns on embodiment of this invention. It is a figure which shows generation | occurrence | production of the light loss in an optical fiber cable by rotation operation | movement of the loss generation part in the deformation | transformation detection apparatus of FIG. 2, (a) is a graph which shows generation | occurrence | production of the light loss in an optical fiber cable, (b) These are figures which show the operating state of a stopper. It is a block diagram which shows the test structure of the loss generation | occurrence | production confirmation test in the optical fiber type deformation | transformation detection system which concerns on embodiment of this invention. It is a graph which shows the relationship between the distance in the loss generation | occurrence | production confirmation test of FIG. It is a figure for demonstrating the relationship between the distance between the stopper and loss generation | occurrence | production part in the loss generation | occurrence | production confirmation test of FIG. 16, and the loss of the generated light, (a) is a figure which shows the distance between a stopper and a loss generation | occurrence | production part. (B) is a graph which shows the relationship between the distance between the stopper in a test result, and a loss generation | occurrence | production part, and the loss of the light to generate | occur | produce.

Explanation of symbols

1 River, 2 Embankment, 3 Slope, 4 Metal pipe, 5 Optical fiber cable,
6 Deformation detection unit, 7 rod, 8 block, 12 OTDR,
66 Anchor for anchoring, 66A base, 69 Deformation detecting device, 70 Loss generating part, 71 Link mechanism, 72 Cable fixing base, 72A base part, 73 Stopper,
74 Rotating shaft, 75 Metal cover, 76 Spacer, 78 Compression spring

Claims (6)

In the optical fiber type deformation detection device for monitoring the deformation of the monitored object by the loss of light propagating through the optical fiber cable,
Fiber optic cable,
A cable fixing base on which the optical fiber cable is fixed by holding the longitudinal direction of the optical fiber cable at at least two points;
The cable fixing base is rotatably provided in a direction orthogonal to the longitudinal direction around a predetermined rotation axis, and one end side is connected to a load that moves due to deformation of the monitoring object, and the movement of the load causes the A loss generating member that generates loss by bending the optical fiber cable after the other end abuts the optical fiber cable by rotating to a predetermined angle in an orthogonal direction;
A stopper that prevents the loss generating member from rotating beyond the predetermined angle;
Positioning means for positioning a position where the loss generating member contacts the optical fiber cable between the two holding points of the cable fixing base;
An optical fiber type deformation detection device comprising: 2. The optical fiber deformation detecting device according to claim 1, wherein the predetermined angle is an angle in a range in which the loss generating member bends the optical fiber cable but does not break the optical fiber cable. An optical fiber type deformation detection device characterized by the above. 3. The optical fiber deformation detecting device according to claim 1, wherein the positioning means is composed of a compression spring and a spacer respectively attached to the rotating shaft from both sides of the loss generating member. Fiber type deformation detector. 4. The optical fiber type deformation detection device according to claim 1, wherein the loss generating member is connected to the load by a connecting member via a link mechanism. 5. The optical fiber type deformation detection device according to claim 1, wherein the loss generating member includes a first rotation radius having a length from the rotation axis to a position where the loss generation member comes into contact with the optical fiber cable, and the rotation axis. An optical fiber type deformation detecting device, characterized in that the second turning radius consisting of a length from a position to a position connected to the load can be changed mutually. 6. A plurality of optical fiber type deformation detecting devices according to claim 1 are provided at predetermined intervals of the optical fiber cable constituting at least one line, and a plurality of optical fiber type deformation detecting devices are provided at predetermined intervals of the monitoring object. An optical fiber deformation detection system comprising an optical monitoring device that is connected to a load and monitors a loss of light propagating through the optical fiber cable constituting the at least one line.

Images