JP6289972B2 - Optical fiber cable and optical signal fluctuation detection sensor system - Google Patents

Description

  The present invention relates to an optical fiber cable in which an optical fiber core is inserted into a metal tube, and an optical signal fluctuation detection sensor system including the optical fiber cable.

  The cut slopes or embankment slopes of railways and roads may cause traffic disturbance due to heavy rain or earthquakes, and may lead to train derailment. There is a need to prevent a derailment accident from occurring by detecting that the slope has collapsed during such a disaster and stopping train operation and traffic.

  Disaster management of slopes due to heavy rain or earthquakes is generally performed by patrol monitoring by personnel. However, there are an enormous number of slopes that should be patroled, and there are limits to monitoring by patrol. In addition, during a disaster such as heavy rain or an earthquake, the patrol itself is dangerous and it is difficult to fully patrol.

  On the other hand, a detection system has been proposed in which a sensor for detecting a collapse is installed on the slope, and the collapse information is automatically transmitted when the slope collapses. Various types of detection systems have been proposed, but detection systems using optical fibers are prominent because of the fact that the sensor itself is an optical fiber cable and can be extended, and there is no influence of lightning or other inductive disturbances. Proposed as a detection system.

  The collapse detection system using an optical fiber is configured by installing an optical fiber cable in which an optical fiber is inserted into a metal tube on a slope to be monitored, and connecting an optical pulse transmitting / receiving device to the optical fiber cable. And when the collapse of the slope occurs and the optical fiber core wire of the installed optical fiber cable changes in pressure, bends, or breaks, the backscattered light from that part is analyzed, and physical quantities such as strain, optical loss, etc. The change is recognized as a slope fall and the fall is detected.

  When detecting a landslide using an optical fiber cable, in order to improve the reliability of the detection of a landslide, it is necessary to reliably deform the optical fiber core in the event of a landslide. A measure is taken in which a low-strength portion having a lower strength than other portions is formed in advance on a part of the metal tube of the fiber cable. By forming the low-strength portion in the metal tube in this way, the metal tube that receives the load from the collapsed earth and sand is easily deformed at the position of the low-strength portion, and accordingly, the optical fiber core wire in the metal tube Will definitely deform.

  As a method of providing such a low-strength portion on the metal tube, there is a method of scraping or caulking the metal tube. For example, Patent Document 1 describes that a low strength portion is formed by caulking a metal tube at a plurality of positions in the longitudinal direction of an optical fiber cable. Thus, the method using caulking is effective in that the formation of the low-strength portion is simple because it is only necessary to locally compress the metal tube from the outside by the caulking processing device.

JP2007-271513 A

  As the caulking structure, for example, flat caulking that caulks the metal tube in a plane in the direction of one straight line (hereinafter also referred to as “diameter line”) perpendicular to the axis of the metal tube, or all metal tubes are used. There is a circumferential caulking that reduces the diameter in the diameter direction over the circumference. Of these, when the low-strength portion is formed by circumferential caulking, it is ideal because the strength is constant throughout the entire circumferential direction of the low-strength portion, but in reality it is a perfect circle by shifting the axis. This is often difficult, and it takes time and effort to form a uniform shape. On the other hand, flat caulking is effective in that it can easily form a low-strength portion by simply compressing a metal tube from the outside with a caulking processing device, and also can keep the machining quality constant. is there.

  When the low strength portion is formed in the metal tube by flat caulking, the low strength portion is most easily deformed when an external force is applied in a direction perpendicular to the caulking surface. In other words, when an external force is applied in a direction having almost no angle with respect to the caulking surface, for example, in a direction parallel to the caulking surface, a situation may occur in which the low-strength portion is not easily deformed. This means that directionality occurs at the circumferential position of the metal tube in the ease of deformation at the low strength portion of the optical fiber cable.

  In view of such circumstances, the present invention can easily and surely deform the low-strength portion of the metal tube to deform the optical fiber core wire, no matter what direction the optical fiber cable receives external force. It is an object of the present invention to provide an optical fiber cable that can be used and an optical signal fluctuation detection sensor system including the optical fiber cable.

  According to the present invention, the above-described problem is solved by the optical fiber cable according to the first invention and the optical signal fluctuation detection sensor system according to the second invention.

<First invention>
An optical fiber cable according to a first aspect of the present invention is an optical fiber cable in which an optical fiber core is inserted into a metal tube, and facilitates deformation of the metal tube when an external force is applied to a plurality of locations in the longitudinal direction of the metal tube. A low-strength part is provided, and the low-strength part is provided by caulking the metal tube with one straight line direction orthogonal to the axis as a caulking direction. When the metal tubes are viewed in the longitudinal direction, they have a crossing angle with each other.

  By providing low strength parts with different caulking directions in the metal tube in this way, no matter which position in the circumferential direction of the metal tube is subjected to bending stress due to external force, any low strength part will cause the caulking surface. On the other hand, since an external force can be received in a substantially right angle direction, the low-strength portion can be easily and reliably deformed to deform the optical fiber core wire in the metal tube.

  In the present invention, it is preferable that the low-strength portions having crossing angles are formed adjacent to each other at a plurality of locations in the longitudinal direction of the metal tube. By adopting such a configuration, when any external force is applied to any of the plurality of locations, any low-strength portion is reliably deformed by receiving the external force in a direction substantially perpendicular to the caulking surface. To do.

  In the present invention, the crossing angle is preferably about 90 degrees. If the crossing angle is set to be small, any low strength portion may receive an external force in a direction having almost no angle with respect to the crimping surface, and the low strength portion cannot be sufficiently deformed. There is a fear. On the other hand, by setting the crossing angle as large as approximately 90 degrees as in the present invention, any low strength portion can be more reliably applied to the crimping surface regardless of the external force from any direction. Since an external force can be received in a substantially right angle direction, the deformation of the low-strength portion, and thus the optical fiber core wire, can be promoted.

<Second invention>
An optical signal fluctuation detection sensor system according to a second invention comprises an optical fiber cable according to the first invention, a light source part for making an optical signal incident on the optical fiber core, and a light receiving part for detecting the optical signal, and an optical fiber cable. It is characterized in that the light receiving part detects the fluctuation of the optical signal accompanying the deformation of the light.

  As described above, since the optical fiber cable according to the first invention is easily and reliably deformed in the low strength portion of the metal tube subjected to external force and the optical fiber core wire, the optical fiber cable of the second invention provided with the optical fiber cable is provided. According to the optical signal fluctuation detection sensor system, the fluctuation of the optical signal accompanying the deformation of the optical fiber core can be reliably detected by the light receiving unit.

  As described above, in the present invention, the caulking direction diameter lines in the low-strength portions at a plurality of locations of the metal tube have an intersection angle when the metal tube is viewed in the longitudinal direction. In any low strength part, an external force is applied in a direction substantially perpendicular to the caulking surface at any low strength part, and the low strength part and thus the optical fiber core wire in the metal tube can be easily and reliably deformed to be deformed. Can do. Further, according to the optical signal fluctuation detection sensor system including the optical fiber cable, the optical signal fluctuation accompanying the deformation of the optical fiber core wire can be reliably detected by the light receiving unit.

(A) is a figure which shows the use condition of 1st embodiment apparatus as a landslide detection system, (B) is a figure which shows the state which supported the optical fiber cable with the mooring member. It is a schematic block diagram of the apparatus of the first embodiment. 2 is a schematic configuration diagram showing one of a plurality of detection units included in the apparatus together with an optical fiber cable. It is a figure which shows the displacement margin of the optical fiber cable in 1st embodiment, (A) is before a deformation | transformation of an optical fiber cable, (B) has shown the state after a deformation | transformation of an optical fiber cable. It is the figure which showed the state which the easy displacement part of the optical fiber cable in 2nd embodiment displaces. It is a figure which shows an example of the suppression member provided in the easy displacement part of the optical fiber cable in 2nd embodiment. It is a figure which shows the other example of the suppression member provided in the easy displacement part of the optical fiber cable in 2nd embodiment. It is a figure which shows the other example of the suppression member provided in the easy displacement part of the optical fiber cable in 2nd embodiment, (A) is a front view, (B) is a side view. It is a figure which shows the modification of the easy displacement part of the optical fiber cable in 2nd embodiment. (A), (B) is a perspective view which shows an example of the optical fiber cable low intensity | strength part in 3rd embodiment, respectively. It is a figure which shows the cross section of the optical fiber cable low intensity | strength part in 4th embodiment. An example of the pressure receiving member in 5th embodiment is shown, (A) is a front view, (B) is a longitudinal cross-sectional view, (C) is a top view. The other example of the pressure receiving member in 5th embodiment is shown, (A) is a front view, (B) is a longitudinal cross-sectional view, (C) is a top view. It is a figure which shows the usage condition of the pressure receiving member in 5th embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<First embodiment>
FIG. 1A is a diagram showing a use state of the apparatus of this embodiment as a landslide detection system, and FIG. 1B is a diagram showing a state in which an optical fiber cable is supported by a mooring member described later. 2 is a schematic configuration diagram of the apparatus of the present embodiment, and FIG. 3 is a schematic configuration diagram illustrating one of a plurality of detection units included in the apparatus of FIG. 2 together with an optical fiber cable.

  The apparatus of this embodiment has a landslide collapse monitoring apparatus 10 as a monitoring base station installed in a station building or the like, and the landslide collapse monitoring apparatus 10 includes a number of detection units 11 (four detection units 11A and 11B in FIG. 2). , 11C, and 11D), a control device 12 that controls these and determines the output from the detection unit 11, and a display device 13 that displays the result. The control device 12 is connected to a wireless communication device 15 that communicates with the train 14.

  Optical fiber cables 16A, 16B, 16C, and 16D extend from each of the detection units 11A, 11B, 11C, and 11D, and these optical fiber cables 16A, 16B, 16C, and 16D have one trunk cable as a preferred form. It is summarized as 17 and extends toward the slope where landslide should be detected. As described above, since a large number of the detection units 11 are provided, the corresponding number of optical fiber cables 16 are inserted into one trunk cable 17. As shown in FIG. 2, one trunk cable 17 has a plurality of sections (in FIG. 2, for example, section 1, section 2, 4 sections of section 3 and section 4 are shown), the optical fiber cables 16A, 16B, 16C, 16D are drawn out from the trunk cable 17 so as to be sequentially installed. Further, instead of inserting a plurality of optical fiber cables 16 into the main cable 17, for example, an optical fiber in which a plurality of optical fibers are accommodated in the main cable 17 and the optical fibers are inserted into a metal tube. The cable 16 may be branched from the trunk cable 17 to each section.

  In general, for example, as shown in FIG. 1A, the slope is a cut slope R on one side which is a highland side and a lowland with respect to a flat track laying band Q where the railroad track P is laid. There is an embankment slope S on the other side as a side. The track laying band Q may be a road.

  In the example of FIG. 1 (A), the main cable 17 extends from both sides of the line laying band Q, that is, near the boundary between the line laying band Q and the cut slope R and near the boundary between the embankment slope S. An outgoing optical fiber cable 16 is installed. The line laying band Q is divided into a plurality of sections, for example, section 1, section 2, section 3, and section 4, as seen in FIG. As seen in FIG. 2, the optical fiber cables 16A, 16B, 16C, and 16D drawn from the trunk cable 17 are connected to the ground in each section, that is, section 1, section 2, section 3, and section 4. Are supported by the mooring member 18 and extend over the respective ranges of the sections 1, 2, 3 and 4.

  In the present embodiment, the optical fiber cables 16A, 16B, 16C, 16D are not only cut on the cut slope R side, but also draw the other optical fiber cable 16 from the main line cable 17 so that the section 1, section 2, section 3, By providing the section 4 on the embankment slope S side in the same manner, it is possible to detect landslides on both slopes.

  For example, as shown in FIG. 1B, the anchoring member 18 supports the optical fiber cable 16 in a state in which the optical fiber cable 16 can be moved in the longitudinal direction by a hook portion 18A that can hook the optical fiber cable 16 from the side. It has a pile shape and is driven against the ground at a plurality of positions at intervals in the longitudinal direction. The anchoring member 18 is preferably provided at the position of the low strength portion 21A of the metal tube 21 of the optical fiber cable 16 described later in the longitudinal direction. By providing the mooring member 18 at the position of the low-strength portion 21A in this way, when the optical fiber cable 16 receives a load from the collapsed earth and sand, the mooring member 18 serves as a fulcrum to make the low-strength portion 21A easy. Deformed. The mooring member 18 only needs to support the optical fiber cable 16 with respect to the ground, and is not limited to the shape shown in FIG.

  In addition, it is not essential to previously form the low-strength portion 21A in the optical fiber cable 16. After the optical fiber cable 16 in which the low-strength portion 21A is not formed in the metal tube 21 is supported by the anchoring member 18, the low-strength portion 21A The low strength portion 21A may be formed by caulking the metal tube 21 at a position supported by the mooring member 18. As a form of supporting the optical fiber cable by the mooring member 18, for example, in addition to the form shown in FIG. The optical fiber cables 16A, 16B, 16C, and 16D are combined as one trunk cable 17 as described above, but are connected to the corresponding detection units 11A, 11B, 11C, and 11D in the station building. ing.

  Each of the optical fiber cables 16A, 16B, 16C, 16D (since each optical fiber cable has the same form, FIG. 3 shows the optical fiber cable 16 and thus the detection unit is also shown as the detection unit 11). As shown in (A), two optical fiber core wires 22A and 22B are inserted into the metal tube 21, and one of the optical transmission paths is the forward path section and the other is the return path section. . The two optical fiber cores 22A and 22B are connected by appropriate means so as to form a folded loop portion 22C at one end (right end in FIG. 3), and one optical fiber core wire forming the forward path portion at the other end. 22 A is connected to the light source unit 23, and the other optical fiber core wire 22 B forming the return path unit is connected to the light receiving unit 24. A metal tube 21 into which the optical fiber core wires 22A and 22B are inserted has a cap-shaped or box-shaped protective member 25 attached at one end thereof, and the folded loop 22C is protected. The two optical fiber cores 22A and 22B in the metal tube 21 are connected so that one ends thereof form a loop back for convenience of work, but one long and continuous optical fiber core wire is folded back to the forward path portion. You may make it have a return path part. In the present embodiment, the light source unit 23 and the light receiving unit 24 are combined as one detection unit 11. Since the detection unit 11 detects not the degree of change of the optical signal (hereinafter also simply referred to as “light”) but the presence / absence (blocking), compared to OTDR or BOTDR based on measurement of the fluctuation amount of light, Extremely simple configuration and low cost.

  The metal tube 21 has low-strength portions 21A formed at a plurality of positions spaced in the longitudinal direction. The low-strength portion 21 </ b> A is a part that is locally processed to have a lower strength in order to preferentially deform than the other portions when an external force is applied to the metal tube 21. For example, in the example of FIG. 3A, the metal tube 21 is crimped (crushed) with the direction of one straight line (hereinafter also referred to as “diameter line”) orthogonal to the axis of the metal tube 21 as the crimping direction. The strength is reduced by forming the flat part by applying the above. Of course, the caulking process is performed in a processing dimension range that does not affect the optical fiber core wires 22A and 22B in the metal tube 21. The low-strength portion can be made by other methods, for example, by thinning the corresponding portion without depending on the caulking process. When the metal tube 21 formed with the low-strength portion 21A receives a force from the earth and sand caused by the landslide on the slope as an external force, the metal tube 21 displaces the optical fiber cable 16 to be described later (FIG. 4A). , (B)), the optical fiber cable moves in the range of FIG. 3B to the state of FIG. 3C. In particular, the low strength portion 21A is greatly deformed. Since the optical fiber core wires 22A and 22B in the metal tube 21 are significantly lower in strength than the metal tube 21 and have brittleness, they are easily broken and disconnected. That is, when the external force is received, the light that has passed through the optical fiber core wires 22A and 22B is blocked. FIG. 3C shows an example in which both of the optical fiber cores 22A and 22B are disconnected. However, in order to block light, at least one of the optical fiber cores 22A and 22B must be disconnected. That's fine.

  As the material of the metal tube 21, stainless steel, nickel alloy, copper, titanium, aluminum or the like can be used. The optical fiber cable 16 is covered with vinyl chloride resin, polyethylene, nylon, urethane, or the like, or the inside of the metal tube 21 is filled with a resin such as an epoxy resin or a urethane resin or a synthetic oil of a hydrocarbon polymer. be able to.

  In this embodiment, the other end of the optical fiber cable 16, that is, the end connected to the landslide collapse monitoring device 10 provided in the station building, of the two optical fiber core wires 22 </ b> A and 22 </ b> B in the metal tube 21. One of the optical fiber cores 22A is connected to the light source unit 23, and the other optical fiber core wire 22B is connected to the light receiving unit 24. Therefore, in normal times when no landslides have occurred on the slope, the light emitted from the light source section 23 travels through one optical fiber core 22A as the forward path section, passes through the return loop section 22C on one end side, and returns to the return path section. And enters the other optical fiber core wire 22B and is received by the light receiving unit 24.

In the present embodiment, the optical fiber cable 16 has a length having a “displacement allowance” that allows deformation of the low-strength portion 21A. The “displacement” is a margin length for allowing bending displacement in a straight-line optical fiber cable. As seen in FIG. 4 (A), the optical fiber cable 16 is wound portion 32 formed by winding the optical fiber cable by the local is formed, the total length of the winding portion 32 as a white the displacement It is secured. In the present embodiment, the winding portion 32 is formed in a range that does not include the low-strength portion.

When the optical fiber cable 16 is subjected to load from soil collapse, as seen in FIG. 4 (B), the load optical fiber cable 16 which forms the winding portion 32 within the range of the length of the winding portion 32 Accordingly, the optical fiber cable 16 can be bent and displaced in a range including the low-strength portion 21A by moving toward the low-strength portion 21A. As a result, as described above, the optical fiber core wires 22A and 22B are easily broken and disconnected at the position of the low strength portion 21A.

As can be seen by comparing FIG. 3B showing the optical fiber cable 16 before deformation and FIG. 3C showing the optical fiber cable 16 after deformation, the low strength after deformation of the optical fiber cable 16 shown in FIG. The difference between the length (l ₂ + l ₃ ) in the vicinity of the portion 21A and the length l ₁ in the vicinity of the low-strength portion 21A after the deformation of the optical fiber cable 16 shown in FIG. (L ₂ + l ₃ −l ₁ ) is the length of the movement at the displacement.

  If such a displacement allowance is not given to the metal tube 21, the metal tube 21 must maintain a linear shape, and bending displacement becomes difficult, and light is only cut by shearing in a straight state. Although the fiber core wires 22A and 22B cannot be disconnected, the load from the collapsible earth and sand does not reach the shearing of the metal tube 21 by providing a displacement margin as in the present embodiment. However, since the metal tube 21 is easily bent and displaced by the low-strength portion 21A, the optical fiber core wires 22A and 22B in the metal tube 21 can be easily disconnected, and the collapse of the earth and sand can be reliably detected. .

In the present embodiment, the displacement allowance has been and it is formed by the winding portion 32 by winding the optical fiber cable 16 by the local, the form of white displacement is not limited to this, for example, optical fiber cable 16 It may be formed by curving at a local part.

  In this embodiment, in order to promote the deformation of the low strength portion 21A of the optical fiber cable 16 when a landslide occurs, the pressure receiving member 27 described later receives the landslide sand and transmits the received pressure to the low strength portion 21A. It is also possible to configure so as to. As shown in FIG. 1, each low-strength portion 21 </ b> A of the metal pipe 21 of the optical fiber cable 16 installed in the vicinity of the boundary portion between the track laying band Q and the embankment slope S is downward along the embankment slope S. A wire 26 serving as an extending cable body is suspended. A pressure receiving member 27 that receives the load of collapsible earth and sand is locked and attached to the wire 26 at a plurality of positions in the longitudinal direction of the wire 26. The pressure receiving member 27 is formed with a receiving surface for receiving the flow of collapsible earth and sand, and maintains a posture in which the receiving surface is substantially perpendicular to the inclination direction of the embankment slope S. Therefore, when the earth and sand on the embankment slope S collapses and the pressure receiving member 27 receives a load from the flow of the collapsed earth and sand on the receiving surface, the pressure receiving force generates tension on the wire 26, and this tension is applied to the optical fiber cable 16. This is transmitted to the low-strength portion 21A, and the deformation of the low-strength portion 21A and thus the disconnection of the optical fiber core wires 22A and 22B are promoted. That is, the sensitivity of the low-strength portion 21 </ b> A that causes deformation due to an external force is enhanced as compared with other portions.

  Further, a weight (not shown) may be engaged with the wire 26 together with the pressure receiving member 27 or instead of the pressure receiving member 27. By holding the weight in this way, when the sediment collapses, the load due to the weight of the weight acts on the wire 26 in the area where the sediment is absent, and the tension corresponding to the load is applied to the wire 26. Arise. As a result, the tension is transmitted to the low strength portion 21A of the optical fiber cable 16, the low strength portion 21A is deformed, and the disconnection of the optical fiber core wires 22A and 22B is promoted.

  In the form shown in FIG. 1, the above-described wire 26, pressure receiving member 27, and weight are not provided in the optical fiber cable 16 installed in the vicinity of the boundary between the track laying band Q and the cut slope R. However, when the cut slope R collapses, the optical fiber cable 16 receives the flow of the collapsed soil and deforms. However, for example, when the optical fiber cable 16 is installed on the cut slope R above the position shown in FIG. 1, it is possible to provide the optical fiber cable 16 with a wire 26, a pressure receiving member 27, and a weight. is there.

  Next, the operation principle of the landslide detection system having such a configuration will be described. As described above, in normal times when no landslide has occurred, the light emitted from the light source unit 23 is one optical fiber core wire 22A (forward path portion), the return loop portion 22C, and the other optical fiber core wire 22B ( The light-receiving unit 24 receives light after traveling the return path portion. Then, the control device 12 determines that the optical fiber core wires 22A and 22B are not disconnected while the light receiving unit 24 is receiving light, that is, no landslide has occurred in any of the sections 1 to 4, and A signal corresponding to the determination result is transmitted to the display device 13. As a result, the display device 13 displays a determination result that no landslide has occurred.

  On the other hand, for example, when a landslide has occurred in the section 2 of the embankment slope S, the pressure receiving member 27 located in the section 2 flows on the receiving surface of the pressure receiving member 27 as described above. The tension is transmitted to the low-strength portion 21A of the optical fiber cable 16B in the section 2 through the wire 26 that receives the load from the collapsed sand and sand and generates tension by the pressure received. As a result, as shown in FIGS. 3C and 4B, the metal tube 21, particularly the low-strength portion 21A is greatly bent and deformed, and the optical fiber cores 22A and 22B in the metal tube 21 are broken. Disconnect. At this time, since the optical fiber cable 16 is supported by the anchoring member 18 at the low-strength portion 21A, the anchoring member 18 driven into the ground serves as a fulcrum and receives low tension from the wire 26. The strength portion 21A is easily deformed.

  When the optical fiber cores 22A and 22B are disconnected, the light passing through the optical fiber cores 22A and 22B is blocked (disrupted), so that the light receiving unit 24 of the detection unit 11B corresponding to the section 2 does not receive light. Become. Therefore, the control device 12 determines that the optical fiber cores 22A and 22B are disconnected in the section 2, that is, the landslide has occurred, and transmits a signal corresponding to the determination result to the display device 13 and the wireless communication device 15. . Then, the display device 13 displays that a landslide has occurred in the section 2 of the embankment slope S. Moreover, the radio | wireless communication apparatus 15 transmits the radio signal corresponding to the said determination result toward the train 14, and notifies the crew member of this train 14 of the occurrence of the landslide in the said area. As a result, by appropriately stopping the train 14, it is possible to reliably prevent the train from being damaged due to a landslide. In addition, for roads, it is possible to prevent accidents by stopping traffic of vehicles.

  Here, the case where a landslide has occurred on the embankment slope S has been described. However, even when a landslide has occurred on the cut slope R, the optical fiber cable 16 is directly deformed by receiving a load from the landslide. Except for this, the operating principle of the landslide detection system is the same as that of the embankment slope S described above, and the description thereof is omitted.

  In this embodiment, since the monitoring area is divided into a plurality of areas and the optical fiber cables are arranged corresponding to each of them, it is possible to immediately detect in which section the disconnection has occurred. In this embodiment, since only the presence or absence of an optical signal is detected, the disconnection position cannot be detected, but since it is possible to detect in which section the disconnection has occurred, the position where the landslide has occurred is thereby determined. Can be easily identified. In addition, in the conventional detection method using backscattered light, landslides are detected based on the amount of change in strain and light loss, so there is ambiguity in the amount of change and threshold setting for setting the detection limit. Since only the presence / absence of an optical signal is detected, a landslide can be reliably detected.

  In addition, the monitoring level can be improved by increasing the number of sections in the area where there is a high possibility of landslides (shortening the section length) and decreasing the number of sections in the area where the possibility is low. Moreover, in this embodiment, since an optical fiber cable should just be replaced | exchanged only about the area where the landslide has occurred, subsequent repair is easy. If a larger number of optical fiber cables than the number of sections are stored in the trunk cable in advance, an extra optical fiber cable can be used as a replacement optical fiber cable, and this point also facilitates repair.

  In the present embodiment, an example in which a plurality of detection units are provided corresponding to each of the optical fiber cables arranged in a plurality of sections is illustrated, but common to each optical fiber cable without using a plurality of detection units. The common detection unit may be sequentially switched and connected to each optical fiber cable. In this way, the cost can be greatly reduced with respect to providing the detection unit.

  Further, in the landslide detection system according to the present embodiment, the presence or absence of light received by the light receiving unit, that is, the light is blocked by using an optical fiber cable having an optical fiber core wire formed with the forward path part and the return path part. Depending on whether or not the optical fiber core wire is broken and the occurrence of landslide is detected, instead of this, for example, when the optical fiber core wire undergoes pressure change, bending, breakage, etc. An optical transceiver (BOTDR or OTDR) that analyzes backscattered light from the light source may be used to detect changes in physical quantities such as strain, light loss, and the like as landslides and detect landslides. When performing such detection, it is not essential to fold the optical fiber core wire to form the forward path portion and the return path portion, and the single optical fiber core wire can be used without being folded back.

<Second embodiment>
This embodiment is a first embodiment in which the easy-displacement part is not provided in that the easy-displacement part in which the metal tube is easily displaced in the predetermined range including the low-strength part than the outside of the predetermined range is provided. It is different from the form. In the present embodiment, since the low strength portion of the metal tube is located within the range of the easy displacement portion, the deformation at the low strength portion is induced by the displacement at the easy displacement portion. Hereinafter, the present embodiment will be described focusing on differences from the first embodiment.

As shown in FIG. 5, the easily displaceable portion 28 provided in the optical fiber cable 16 is formed by winding a predetermined range including the low strength portion 21 </ b> A in the cable longitudinal direction of the optical fiber cable 16 into a substantially circular shape . ing. By thus forming an easy displacement portion 28 by winding a portion of the optical fiber cable 16, it is possible to use also as a the the easy displacement portion 28 white displacement of the optical fiber cable 16.

  When the earth and sand collapses and the easy-displacement portion 28 receives a downward load in FIG. 5 from the earth and sand, the easy-displacement portion 28, as seen in FIG. 5 to reduce the lateral dimension). As a result, bending deformation is induced in the low-strength portion 21A located at the lowermost portion within the range of the easy-displacement portion 28, and the optical fiber core wires 22A and 22B are easily disconnected at the position of the low-strength portion 21A. It is possible to reliably detect the collapse of earth and sand.

  In order to deform the metal tube 21 with the low-strength portion 21A located within the range of the easy-displacement portion 28, the easy-displacement in the plane including the easy-displacement portion 28 (a plane parallel to the paper surface in FIG. A state in which the displacement portion 28 is fastened, that is, a state in which the optical fiber cables 16 are close to each other in a direction perpendicular to the plane of the intersection between the optical fiber cables 16 (the uppermost portion of the easy displacement portion 28 in FIG. 5). It is preferable to displace the easily displaceable portion 28 in the width direction (lateral direction in FIG. 5) while maintaining it. If the optical fiber cables 16 are separated from each other in the perpendicular direction at the intersecting portion, the stress to be applied to the low strength portion 21A is not concentrated on the low strength portion even if the easily displaceable portion 28 is displaced in the width direction. Since it escapes to the periphery, the low-strength portion cannot be sufficiently deformed.

  In order to surely displace the easily displaceable portion 28 in the width direction of the substantially circular portion, the easily displaceable portion 28 is formed at the intersection of the optical fiber cables 16 (the uppermost portion of the easily displaceable portion 28 in FIG. 5). And a restraining member having a play that allows displacement (movement) in the longitudinal direction of the optical fiber cable while preventing the optical fiber cables 16 from separating in a direction perpendicular to a plane including Is preferred.

The suppression member can adopt various forms. FIG. 6 thru | or FIG. 8 (A), (B) is a figure which shows an example of a suppression member, respectively. In these drawings, the illustration of the low-strength portion 21A is omitted. The restraining member 29 shown in FIG. 6 is configured as a bundling member that bundles the intersecting portions by winding the wire around the intersecting portions of the easily displaceable portion 28 a plurality of times. Moreover, the suppressing member 30 shown by FIG. 7 is comprised as a tubular member which penetrated the said cross member. Further, the suppressing member 31 shown in FIGS. 8A and 8B is configured as a thin box-shaped member that accommodates the entire easily displaceable portion 28. According to these restraining members, it is possible to displace downward while preventing the optical fiber cables 16 from being separated from each other at the intersecting portion in the easily displaceable portion 28, thereby facilitating deformation of the metal tube 21 at the low strength portion 21A. To do.

  5 to 8 in the present embodiment is formed by bending the optical fiber cable so as to form a closed loop when viewed in a direction perpendicular to the paper surface. The portion 28 is not limited to this, and can be formed in various forms. For example, the easy displacement portion 28 may be formed in a substantially Ω shape as shown in FIG. 9 by bending the optical fiber cable 16, or may be formed in a waveform or the like. Even when the easy-displacement portion 28 is formed in these shapes, for example, the easy-displacement portion 28 is accommodated in a thin box-like restraining member (see FIGS. 8A and 8B). It is preferable that the easy-displacement part 28 is deformed while maintaining the state where the easy-displacement part 28 is held in a plane including the part 28.

  Further, as still another form of the easily displaceable portion, for example, a pressing member (not shown) for promoting the deformation of the low-strength portion 21A of the optical fiber cable 16 may be attached to the optical fiber cable 16. For example, the pressing member can be configured as a member having a substantially ring shape surrounding substantially the entire circumference of the low-strength portion 21A, and a wedge-shaped pressing portion that protrudes toward the low-strength portion at the inner edge thereof. . By inserting the optical fiber cable 16 into the inner edge of such a pressing member, when a load is applied from the collapsed earth and sand, the pressing portion of the pressing member bites into the low strength portion 21A, and the low strength portion 21A is more It can be reliably deformed. For example, when the wire 26, the pressure receiving member 27, and the weight described above are provided, the wire 26 is suspended from the pressing member, so that when the landslide collapses, the tension is applied to the wire 26. The member moves downward and the pressing portion of the pressing member bites into the low strength portion 21A, causing the low strength portion 21A to be deformed. Further, for example, by fixing the pressing member to the mooring member 18, when the optical fiber cable 16 moves downward at the time of landslide, the pressing portion of the pressing member bites into the low-strength portion 21 </ b> A. The strength portion 21A is deformed.

<Third embodiment>
In this embodiment, the diameter lines in the caulking direction of the plurality of low-strength portions formed on the metal tube of the optical fiber cable are different from each other, and the diameter lines in the caulking direction of all the low-strength portions are in the same direction. Different from the first and second embodiments located. Hereinafter, the present embodiment will be described based on FIGS. 10A and 10B with a focus on differences from the first and second embodiments.

  The low-strength portion 21A of the metal tube 21 is most easily deformed when a load from the collapsed sand is received in a direction perpendicular to the caulking surface. In other words, when all the low-strength portions 21A are formed by caulking in the same direction, the low-strength portions 21A collapse in a direction having almost no angle with respect to the caulking surface, for example, in a direction parallel to the caulking surface. When a load from earth and sand is received, a situation may occur in which these low-strength portions 21A are not easily deformed. This means that directionality occurs at the circumferential position of the metal tube in the deformability of the low-strength portion 21A of the optical fiber cable 16.

  In order to cope with such a situation, the low-strength portion 21A in the present embodiment is such that the diameter lines in the caulking direction of the low-strength portions 21A at a plurality of positions have an intersection angle when the metal tube 21 is viewed in the longitudinal direction. It is formed to have. For example, in the form shown in FIG. 10A, the low-strength portions 21 </ b> A in which the crossing angle between the diameter lines in the caulking direction forms approximately 90 ° are alternately formed in the longitudinal direction of the metal tube 21. In this way, by providing the low strength portion 21A with different caulking directions, any low strength portion 21A can receive any bending stress due to the load from the collapsed soil at any position in the circumferential direction of the metal tube 21. Since the load can be received in a direction substantially perpendicular to the caulking surface, if these different low-strength portions 21A are both located in the same section of the detection area, the collapsed sediment can be taken from any direction. Even if it is received, the low-strength portion 21A is easily and reliably deformed to disconnect the optical fiber core wires 22A and 22B, and the occurrence of landslide can be reliably detected.

  Moreover, in this embodiment, since the said crossing angle is set large as about 90 degree | times, even if it receives collapsed earth and sand from what direction, in any low intensity | strength part 21A, it is more reliably with respect to a crimping surface. Thus, an external force can be received in a substantially perpendicular direction, and the deformation of the low-strength portion 21A, and thus the disconnection of the optical fiber core wires 22A and 22B can be promoted.

  The positions where the low strength portions 21A having different caulking directions are formed are not limited to the form in which the low strength portions 21A are located apart from each other as shown in FIG. 10A. For example, in the longitudinal direction of the metal tube 21 As shown in FIG. 10B, the low-strength portions 21A having different caulking directions may be adjacent to each other. By setting it as such a structure, even if it is any place of the said several places that receive the load of collapsed earth and sand, any low intensity | strength part 21A in the place which received the said load is a crimping surface. On the other hand, it receives the above load in a substantially right angle direction and reliably deforms.

  In the present embodiment, for the low-strength portions 21A having different caulking directions, the crossing angle between the diameter lines in the caulking direction is approximately 90 °. However, the crossing angle is not limited to this, and may be arbitrarily set. it can. In the present embodiment, two types of low-strength portions 21A having crossing angles are provided. Instead, three or more types of low-strength portions 21A having crossing angles are provided. Also good.

<Fourth embodiment>
In the present embodiment, the stress concentration portion having a lower strength is formed in the range of the low strength portion of the metal tube, such a stress concentration portion is not formed, and the strength of the low strength portion is in the entire range. And different from the first to third embodiments. Hereinafter, the present embodiment will be described based on FIG. 11 with a focus on differences from the first to third embodiments. In FIG. 11, only the metal tube 21 is shown, and the optical fiber core wires 22A and 22B are not shown.

  As described above, in the low-strength portion 21A in the present embodiment, a stress concentration portion for further reducing the strength of the low-strength portion 21A is locally formed within the range of the low-strength portion 21A. In the form shown in FIG. 11, the stress concentration portion 21 </ b> B has a plurality of notches as cuts extending in a direction perpendicular to the paper surface of FIG. 11 on the caulking surface of the low-strength portion 21 </ b> A. By forming the stress concentration portion 21B in this way, when the low strength portion 21A receives a load from the earth and sand, stress concentrates on each stress concentration portion 21B, so that the deformation of the low strength portion 21A is promoted. The optical fiber core wires 22A and 22B can be disconnected more reliably, and the occurrence of landslide can be detected.

  The shape of the stress concentration portion is not limited to the notch as shown in FIG. 11, and can be formed by, for example, a groove, a concave portion, an unevenness, or the like that extends at right angles to the paper surface of FIG. 11. For example, the stress concentration portion is formed by forming a machining surface of a caulking tool for forming a low strength portion in a shape corresponding to the stress concentration portion, so that both the low strength portion and the stress concentration portion can be formed by a single caulking process. It becomes possible to form.

<Fifth embodiment>
The present embodiment is characterized by the structure of the pressure receiving member that receives the flow of the collapsed earth and sand. As shown in FIG. 12A, the pressure receiving member 27 in the present embodiment is formed with a pressure receiving body 27A-1 that is driven into the earth and sand of the embankment slope S (see FIG. 1) and receives the flow of the collapsed earth and sand. The portion 27 </ b> A and one locking portion 27 </ b> B that are locked to a cable body such as a wire 26 suspended from the optical fiber cable 16 are integrally formed.

  As shown in FIGS. 12A to 12C, the pressure-receiving main body 27A has a plate-like member at the center in the width direction in FIGS. 12A and 12B (the left-right direction in FIG. 10A). The plate surface is bent in the plate thickness direction so as to form a V shape with a loose cross section, and the inner concave plate surface is formed as a receiving surface 27A-1 that receives the flow of the collapsed earth and sand. By making the receiving surface 27A-1 concave as described above, the collapsed earth and sand are easily accumulated on the receiving surface 27A-1. 12A and 12C, the pressure receiving main body portion 27A has a pointed tip edge (lower edge in FIGS. 12A and 12B), and the pressure receiving main body portion 27A. Can be embedded in the earth and sand easily (see FIG. 14). At this time, the pressure receiving main body 27A is embedded in the earth and sand in such a posture that the receiving surface 27A-1 is substantially perpendicular to the inclination direction of the embankment slope S, as seen in FIG.

  As often seen in FIG. 12A, one locking portion 27B is formed at the centroid position of the receiving surface 27A-1. As is often seen in FIG. 12C, the locking portion 27B is formed with a locking hole 27B-1 for locking to the end portion of the wire 26 as the striated body. Thus, in this embodiment, since one latching | locking part 27B is provided in the centroid position of receiving surface 27A-1, when receiving surface 27A-1 of the pressure receiving member 27 receives the load from collapsed earth and sand. The tension generated in the wire 26 by the force from the locking portion 27B acts in one direction passing through the centroid.

  Therefore, when a load (pressure) is received from the collapsible earth and sand, the pressure receiving member 27 does not rotate around the locking portion 27B as shown in FIG. 14, and the load is almost all over the receiving surface 27A-1. It will be received evenly, and will move down following the collapsed sediment while maintaining the installation posture of the pressure receiving member 27 (see the solid line portion in FIG. 14) in the normal time before the occurrence of the sediment collapse (see two in FIG. 14). (See dotted line position). As a result, the pressure receiving member 27 completely receives the load from the collapsible earth and sand, and a large tension is generated in the wire 26 locked by the locking portion 27B. The tension is applied to the optical fiber cable via the wire 26. The low strength portion 21A is bent and deformed by being transmitted to the low strength portion 21A of 16B, and the optical fiber core wires 22A and 22B are broken and surely disconnected.

  12A to 12C, only one locking portion 27B of the pressure receiving member 27 is provided at the centroid position of the receiving surface 27A-1, but the position of the locking portion 27B is not limited. The number is not limited to this, and can be appropriately designed as long as the resultant tension of the wire 26 passes through the centroid of the receiving surface. For example, in the form shown in FIGS. 13A to 13C, two locking portions 27B are provided on two side edges of the pressure receiving main body portion 27A (edge portions extending in the vertical direction in FIG. 13A). Each side edge is formed by cutting out the side edges (four in total). The center positions of these four locking portions 27B coincide with the centroid of the receiving surface 27A-1.

  In the form of FIGS. 13 (A) to 13 (C), if the lower end of one wire 26 is branched into four and they are locked to each of the four locking portions 27B, four locking Since the center positions of the portions 27B coincide with the centroid of the receiving surface 27A-1, when the receiving surface 27A-1 of the pressure receiving member 27 receives a load from the collapsed soil, the force from the locking portion 27B The resultant tension of the wire 26 acts in one direction passing through the centroid. Accordingly, the pressure receiving member 27 moves following the collapsing earth and sand while maintaining the installation posture of the pressure receiving member 27 in the normal state, and is generated in the wire 26 as in the embodiment of FIGS. 12 (A) to (C) described above. The low-strength portion 21A of the optical fiber cable 16B is bent and deformed by the tension, and the optical fiber core wires 22A and 22B are bent and surely disconnected.

  Although this embodiment demonstrated the example which comprises a pressure receiving member with a plate-shaped member based on FIGS. 12-14, the pressure receiving member should just be a shape which can receive collapsed earth and sand, and is limited to plate shape. For example, it is also possible to comprise a bowl-shaped member. Further, the pressure receiving member may have a mesh or net-like pressure receiving surface for receiving earth and sand. By forming the pressure receiving surface in a mesh or net shape in this way, moisture permeates the pressure receiving surface. For example, rainwater accumulates in the pressure receiving member and the tension generated in the wire by the weight is transmitted to the optical fiber cable. Therefore, it is possible to prevent malfunction.

  Although the already described first to fifth embodiments have been described separately, a plurality of these embodiments can be combined and implemented.

11, 11A, 11B, 11C, 11D Detection unit 16, 16A, 16B, 16C, 16D Optical fiber cable 18 Anchor member 21 Metal tube 21A Low strength portion 21B Stress concentration portion 22A, 22B Optical fiber core wire 22C Folding loop portion 23 Light source Part 24 light receiving part 26 wire (strand body)
27 Pressure-Receiving Member 27A Pressure-Receiving Body 27A-1 Receiving Surface 27B Locking Section 28 Easy Displacement Section 29, 30, 31 Suppression Member

Claims (3)

In an optical fiber cable with an optical fiber core inserted through a metal tube,
A plurality of low-strength portions that facilitate deformation of the metal tube when subjected to external force are provided adjacent to each other at intervals in the longitudinal direction of the metal tube . The adjacent low-strength portions are formed by caulking with the metal tube being located at a distance smaller than the interval in the longitudinal direction, and the metal tube is locally caulked with the direction orthogonal to the axis line,
An optical fiber cable, wherein the caulking directions in the plurality of low-strength portions in each set have a crossing angle when the metal tube is viewed in the longitudinal direction. The optical fiber cable according to claim 1, wherein the crossing angle is approximately 90 degrees. The optical fiber cable according to claim 1 or 2 , a light source unit that makes an optical signal incident on the optical fiber core, and a light receiving unit that detects the optical signal,
An optical signal fluctuation detection sensor system, wherein a light receiving part detects a fluctuation of an optical signal accompanying deformation of an optical fiber cable.

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