JP2001099755A - Optical fiber sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convert a deformation or a collapse or the like of a hazardous point such as a slope existing in a wide area such as, for example, along a road into a deformation or a rupture of an optical fiber for safely and quickly observing the deformation or the like of the hazardous point by light. SOLUTION: In this optical fiber sensor, optical fiber holding parts 31a and 32a holding an optical fiber 12 are each provided on a pair of connecting members 31 and 32 separately connected to a pair of adjacent retaining wall blocks 14 which are monitoring objectives existing in different positions and these optical holding parts 31a and 32a are moved nearer to each other while holding the optical fiber 12 at different positions in a longitudinal direction for causing a deformation of bending or the like or a rupture in the optical fiber 12 by relative displacement between the connecting members 31 and 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a natural object such as an unstable stratum which is likely to collapse, a rock which may be displaced,
Alternatively, the present invention relates to an optical fiber sensor that monitors displacement and deformation of a monitoring target such as a retaining wall.

[0002]

2. Description of the Related Art For example, road maintenance and disaster prevention management such as landslides around a road generally rely on daily or emergency patrols. To avoid road interruptions due to disasters such as landslides (including burial of roads due to landslides from adjacent slopes, and collapse of the roads themselves or the ground under the roads), frequent patrols etc. Measures such as grasping have been taken conventionally. If the road is interrupted, traffic will be cut off and the transportation of daily goods will be interrupted. If you find something like that, you need to repair it quickly.

[0003]

However, it is extremely difficult to perform a thorough inspection in a short period of time on a long road or the ground around the road. Even when monitoring targets such as roads to be monitored and the ground around the roads are scattered at a plurality of locations, it is difficult to perform short patrols due to the travel time between the monitoring positions. In addition, when the road is interrupted, it is difficult to move to the monitoring position itself. In particular, when a disaster occurs in a wide area due to an earthquake or the like, the movement to the monitoring position becomes practically impossible. Even in daily patrol, there is a problem that the patrol itself involves danger near slopes where landslides are likely to occur or on cliffs where roads are likely to collapse. Patrol in bad weather or at night is also a dangerous operation, and the patrol efficiency is reduced due to bad conditions such as poor visibility.

In view of the above problems, for example, it is conceivable to install a strain gauge on a slope or a monitoring facility using an imaging device such as an ITV in order to grasp a predictive phenomenon of a landslide. It is limited to point observation near the position, and cannot be constantly monitored over a long road. In particular, in a monitoring facility using an imaging device such as an ITV, there is a drawback that the monitoring range is narrow under bad weather such as heavy rain, so that a large number of installations are inevitable, resulting in an increase in cost. In addition, areas where monitoring equipment is particularly required for disaster prevention are often in areas where the weather changes drastically, such as in mountainous areas. There is also a problem that the device is likely to fail under the influence of the induced current. Since it is difficult to secure a view for monitoring in an urban area where buildings and the like are densely arranged, a large number of monitoring equipment using an imaging device such as an ITV must be installed, and the cost increases. In addition, the above-mentioned problem is not limited to roads, and becomes remarkable when the monitoring area is long, such as a railway line, a river embankment, a breakwater provided on the coast of a coast or a lake, or the like.

In recent years, as a method of observing a continuous light loss distribution in the longitudinal direction of an optical fiber, it has been proposed that the intensity of Rayleigh scattered light, which is one of the back scattering phenomena of an optical fiber, depends on the optical loss of the optical fiber. Developed a method using
It has been put to practical use and is being applied to various sensing applications. However, various embankments such as river embankments, ground slopes, bedrock,
There are few optical fiber sensors that can efficiently measure the displacement and deformation of buildings and the like such as bridges (including elevated roads and railways). In other words, the optical fiber sensor is excellent in workability such as mounting on various monitoring objects such as buildings such as river embankments, ground slopes, rocks, bridges, etc. There is a demand for a structure that efficiently acts on bending and breaking of the steel sheet, and there is no suitable structure that satisfies such conditions. Furthermore, there is also a demand for cost reduction, and it has been necessary to develop an optical fiber sensor that satisfies these conditions.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is excellent in workability at a target position, and at a low cost in which an external force can be efficiently applied to deformation such as breakage or bending of an optical fiber. It is an object of the present invention to provide an optical fiber sensor.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a natural structure such as an unstable stratum which is likely to collapse, a rock which may be displaced, or an artificial structure such as a retaining wall. An optical fiber sensor that monitors the displacement and deformation of the monitored object by light, for the monitored object located at different positions from each other, or for the monitored reference object composed of stable rock and the like and the monitored reference object. An optical fiber holding portion for holding an optical fiber is provided on each of a pair of connecting members separately connected to the object to be monitored which may be displaced with respect to the monitoring object, and these optical fiber holding portions are provided on the optical fiber. It is characterized by being arranged close to each other while holding different positions in the longitudinal direction, and causing relative deformation between the connecting members to cause deformation or breakage such as bending or the like in the optical fiber. To.

In the optical fiber sensor according to the present invention, the optical fiber is connected to the optical pulse tester, and the installation location of the optical fiber sensor is abnormal, that is, an unstable formation which may collapse, and a rock which may displace. Monitoring the occurrence of displacement and deformation of a monitoring target such as a natural object such as a natural object or an artificial structure such as a retaining wall (monitoring an abnormality). The monitoring of the abnormality is performed by detecting that the optical fiber incorporated in the optical fiber sensor has undergone deformation such as breakage or bending. The deformation or breakage of the optical fiber is caused by the relative displacement between the plurality of connecting members due to the displacement or deformation of the monitored object, and can be detected from the observation result of the return light of the incident light from the optical pulse tester. The optical pulse tester performs test light incidence and return light observation on an optical fiber (optical test).

As is well known, when light is incident on an optical fiber, Fresnel reflected light at a broken portion of the optical fiber or at a connector connecting portion, or light scattering (Rayleigh scattering) due to minute non-uniformity such as the density of the optical fiber. It is known that the backscattered light generated by the light returns to the input end of the optical fiber, and the time from when the test light enters the optical fiber from the optical pulse tester (OTDR) to when the return light is received. By measuring (hereinafter, “return time”), the position of the break point (distance from the optical pulse tester) can be grasped. From the optical fiber, usually, only return light due to light scattering inherent to the optical fiber, such as the backscattered light of Rayleigh scattered light, is observed.For example, when this optical fiber breaks, from the optical pulse tester to the break point The backscattered light of the Rayleigh scattered light and the strong Fresnel reflected light from the breaking point are observed by the optical pulse tester, and the backscattered Rayleigh scattered light from the optical fiber after the breaking point is not observed. Thereby, the break of the optical fiber is detected, and the position of the break point can be grasped from the return time of the return light of the Fresnel reflected light. Even if the optical fiber is not broken, when the optical fiber is deformed, for example, the optical fiber is rapidly bent, and by observing an increase in light loss at the bent portion, it is possible to detect the bent portion. is there. Further, an increase in light loss is also observed due to crushing of the optical fiber in the cross-sectional direction or the like. That is, from the point where the intensity of the return light suddenly changes in the optical pulse tester (return time of the return light to the optical pulse tester), the existence of the deformed part such as bending of the optical fiber and the position thereof are determined. I can understand.

[0010] The optical fiber sensor of the present invention is capable of displacing or deforming a monitored object such as an unstable stratum which may collapse, a natural object such as rock which may be displaced, or an artificial structure such as a retaining wall. Causes deformation or breakage of the optical fiber, such as bending. Therefore, by detecting deformation, breakage, and the like of the optical fiber by the optical pulse tester, displacement, deformation, and the like of the monitored object can be detected. The break or bending of the optical fiber is detected by observing the Fresnel reflected light from the break point of the optical fiber or observing an increase in loss.

For example, when the optical fiber of the optical fiber sensor breaks, Fresnel reflected light from the break point is observed, an increase in loss at a bent portion or the like is observed, or return light from the optical fiber after the break point is observed. Is stopped, displacement, deformation, collapse, etc. of the object to be monitored provided with the optical fiber sensor are detected. Also, when a plurality of optical fiber sensors are connected to the optical pulse tester, it is also possible to grasp the break position of the optical fiber for each optical fiber sensor from the return time of the Fresnel reflected light, etc. It is possible to ascertain the position where the monitoring object is displaced, deformed, or collapsed. Depending on the cross-sectional shape of the broken optical fiber at the break point, Fresnel reflected light of sufficient intensity may not be generated, but also observe the presence or absence of return light from the optical fiber after the break point, increase in loss, etc. Thus, the presence or absence of a break point and the presence or absence of a deformed portion of the optical fiber can be reliably grasped. As described above, in the present invention, by detecting a deformed portion or the like such as breakage or bending of the optical fiber,
By detecting the occurrence of displacement, deformation, collapse, etc. of the monitored object, and by measuring the position of the break point or bend point of the optical fiber from the return time of the return light to the optical pulse tester, etc. The location where displacement, deformation, collapse, etc. occur can be grasped.

In the construction of a high-speed information communication network, the laying of optical cables using roads, railway tracks, and river embankments is rapidly expanding.
It is suitable to connect an optical fiber of an optical fiber sensor to an optical pulse tester by using an optical fiber of a communication optical cable laid on a gutter of a road or a railway line, a river embankment, or the like. In addition, by connecting the optical fiber of the optical fiber sensor to an appropriate portion of an optical cable for communication laid on a road, a railway line, a river embankment, or the like, a road, a railway line, a river embankment, or the like is present. Unstable formations that may collapse, rocks and other natural objects that may displace,
Alternatively, the optical fiber sensor can be easily installed on an artificial structure such as a retaining wall. For this reason, even if a road, a railroad track, a river embankment, or the like is long, an optical fiber sensor can be easily and appropriately installed at a necessary place.

According to a second aspect of the present invention, in the optical fiber sensor according to the first aspect, the other connecting member moves in a direction perpendicular to the longitudinal direction of the optical fiber with respect to the one connecting member. It is characterized by having a guide means for guiding. According to this optical fiber sensor, since the moving direction of the connecting member is a direction orthogonal to the longitudinal direction of the optical fiber, the optical fiber is deformed in the shearing direction. Since the connecting member is relatively displaced while maintaining the close state of the optical fiber holding portions, even if the relative displacement amount is small, the bending deformation is surely given to the optical fiber in a narrow region between the optical fiber holding portions which are close to each other. And it is reliably broken. If the deformation of the optical fiber is small, bending deformation occurs in the optical fiber, but if the relative displacement between the connecting members increases and the amount of deformation of the optical fiber increases, the optical fiber is broken. In any case, with this optical fiber sensor, the displacement or deformation of the monitored object is reliably converted into bending or breaking of the optical fiber.

According to a third aspect of the present invention, there is provided the first or second aspect.
In the optical fiber sensor according to the above, the optical fiber is housed in a plastically deformable protective tube, the optical fiber holding portion holds the protective tube, and the protective tube is deformed by relative displacement between the connecting members. The optical fiber may be deformed or broken. In the present invention, since the protective tube can be plastically deformed,
After the deformation of the protective tube causes deformation such as bending of the optical fiber, the optical fiber does not return to its original shape unless the protective tube returns to its original shape by another external force. Etc. can be reliably detected. For this reason, for example, the collapse of the soft earth mass
Without giving a large deformation to the optical fiber of the optical fiber sensor,
Even if the optical fiber is not broken, once the optical fiber is deformed by bending or the like, the deformation of the optical fiber is maintained by the plastic deformation of the protective tube, and can be reliably detected by an optical test.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The optical fiber sensor according to the present embodiment is an example of application to an optical monitoring device included in a road management system, and includes a ground and a pavement forming a road, a ground around a road, a cliff or a slope adjacent to the road, a cliff or the like. Monitor the occurrence of displacement and deformation of various monitoring objects such as a retaining wall provided on a slope (in FIGS. 1 and 3, a retaining wall 13 provided on a ground slope 10).
Monitoring).

1 and 3, reference numeral 1 is an optical monitoring device, 2 is a road, 3 and 4 are transmission devices, 5 and 6 are optical cables, 7 is a monitoring unit, 8 is an information box, 9
Is a closure, 10 is a mountain slope, and 11 is an optical fiber sensor. The optical fiber 12 incorporated in the optical fiber sensor 11 has a core diameter of several μm to 10 μm, for example.
A single mode optical fiber having a diameter of about μm and a diameter of 125 μm is employed. Also, the OTDR which is the optical pulse tester 50
For example, a high-resolution type 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 2 m or more (as short as possible) is employed.

FIG. 1 illustrates a retaining wall 13 provided on a mountain slope 10 facing the road 2 as an example of an object to be monitored by the optical monitoring device 1. One or more optical fibers 12 (two in FIG. 1) laid so as to be stretched over an area where there is a risk of deformation or collapse of the retaining wall 13 (hereinafter referred to as a “monitoring target area”). A fiber sensor 11 is provided. The optical fiber sensor 11 causes the optical fiber 12 to deform or break such as bending due to local displacement or deformation of the retaining wall 13. And the retaining wall 13
An abnormal point such as deformation or breakage caused in the optical fiber 12 due to local displacement or deformation of the optical fiber 12 is detected by an optical pulse tester 5 connected to the optical fiber 12 via the optical fiber or the like of the optical cable 5.
The local displacement and deformation of the retaining wall 13 are detected by detecting the incident light from 0 and the optical test based on the observation of the return light.

More specifically, as shown in FIG. 2, one protection tube 12 laid so as to extend around the monitoring target area is provided.
The optical fibers 12 are inserted from both ends of a, respectively.
As shown in FIG. 3, two optical fibers 12 are housed over substantially the entire length of the protection tube 12a. Further, the protective tube 12a is filled with jelly 12c, and the optical fibers 12 are stably stored without vibration. Waterproofing or the like is performed on both ends 12d in the longitudinal direction of the protective tube 12a. The protective tube 12a is preferably made of a plastically deformable material such as metal, and is preferably a material that does not cause a decrease in strength due to corrosion. For example, a stainless steel tube or the like is suitable. However, even when a metal pipe such as a stainless steel pipe is adopted, in consideration of the necessity of laying a curve, etc.,
It is preferable to employ one that can be easily bent and deformed on site. In the present embodiment, a stainless steel tube of about φ2.0 is employed.

The optical fiber sensor 11 causes the optical fiber 12 to undergo deformation such as breakage or bending due to local displacement or deformation of the retaining wall 13. Local displacement or deformation of the retaining wall 13 is mainly caused by deformation of the ground slope 10, such as downward movement of soil on the ground slope 10 side or deterioration of the ground on the road 2 side. Downward, earth pressure on the ground slope 10, water pressure of spring from the ground slope 10, bulging due to overhang of tree roots growing on the ground slope 10, and other retaining walls There is a displacement, a drop, etc. due to a decrease in anchoring force on the ground slope 10 due to aged deterioration of the retaining wall block 14 constituting the block 13 and the like. The retaining wall 13 is constructed by stacking a number of retaining wall blocks 14 vertically and horizontally. The retaining wall block 14 is made of concrete, and is stably installed so as not to move on the ground slope 10 due to its own weight or the anchoring force of the anchor. Each of the retaining wall blocks 14 is also an object to be monitored independently, and the optical fiber sensor 11 monitors the relative displacement between the retaining wall blocks 14 and the deformation of a specific retaining wall block 14 to thereby determine the retaining wall 1.
3. Monitor the local displacement and deformation of the whole. By detecting a small displacement or deformation of the retaining wall block 14 which is a predictive phenomenon such as a collapse of the retaining wall 13, the information can be used for disaster prevention measures such as a collapse of the retaining wall 13. In addition, as the retaining wall, cast-in-place concrete, a wall formed by mortar spraying, and the like also exist, but the above-described local displacement and deformation is a problem that similarly occurs in these walls, and the present invention Monitoring of displacement and deformation by the optical fiber sensor is performed in the same manner as in the case of the retaining wall 13 including the retaining wall block 14. However, in the case of cast-in-place concrete or a wall formed by spraying mortar, the retaining wall block 1
Since it is not divided into a plurality as in 4, an optical fiber sensor is installed at a location where local displacement or deformation may occur, and relative displacement between different positions of the wall is detected.

FIGS. 4A and 4B are front views showing the operation of the optical fiber sensor 11, wherein FIG. 4A shows the state before the retaining wall 13 is deformed, FIG. 4B shows the state after the retaining wall 13 is deformed, and FIG. (A) is normal (no partial displacement or deformation occurs in the retaining wall 13), and (b) is a bending of the optical fiber 12 due to displacement between the retaining wall blocks 14. (C) shows a state in which the optical fiber 12 is broken by the displacement between the retaining wall blocks 14. As shown in FIG. 5A, the optical fiber sensor 11 is installed between adjacent retaining wall blocks 14, and a pair of connecting members 31 fixed to different retaining wall blocks 14 by anchors 30, respectively.
32. The optical fiber holding portions 31a and 32a provided on the connection members 31 and 32 respectively hold the protection tubes 12a at different positions in the longitudinal direction of the optical fiber 12 (different positions in the longitudinal direction of the protection tube 12a) and hold each other. Being close.

In FIG. 5A, the optical fiber holding unit 3
1a and 32a are formed by bending the edges of the plate-shaped connecting members 31 and 32 into a tubular shape for accommodating the protective tube 12a, and the connecting members 31 and 32 are relatively rotatable about the protective tube 12a, respectively. It has a hinge structure. Since the protective tube 12a is housed in each of the optical fiber holding portions 31a and 32a in which the respective central axes are arranged on the same straight line, and the free movement is regulated, the optical fiber 12 housed in the protective tube 12a is also free. Since the movement is restricted, there is no fear of inadvertently applying vibration or the like. The optical fiber sensor 11 includes a pair of optical fiber holding portions 31a provided at two locations of one connecting member 31 which are separated from each other.
The optical fiber holding portions 32a provided so as to protrude from the other connecting member 32 are inserted into the space 33 secured therebetween, and the central axes of the optical fiber holding portions 31a and 32a are aligned on the same straight line. Then, these optical fiber holding portions 31
The protective tube 12a is communicated with the a and 32a to be assembled. The two optical fiber holding portions 31a on the connecting member 31 side are fixed when the optical fiber sensor 11 is assembled because the two optical fiber holding portions 31a on the connecting member 31 side are fixed with their central axes aligned on the same straight line. The center axis of the optical fiber holding portion 32a on the other connecting member 32 side is made to coincide with the center axis of the other. As a result, the protection tube 12a communicated with each of the optical fiber holding portions 31a and 32a and the optical fiber 12 in the protection tube 12a are connected to both the optical fiber holding portions 3a.
It will extend along the central axis of 1a, 32a.

When there is no displacement between the adjacent retaining wall blocks 14 (initial state), the state where the central axes of the optical fiber holding portions 31a and 32a are aligned on the same straight line is maintained, and the protective tube is maintained. No deformation such as bending is given to the optical fiber 12a and the optical fiber 12 (see FIGS. 4A and 5A). However, when a positional displacement occurs between the adjacent retaining wall blocks 14 and the relative displacement between the connecting members 31 and 32 is caused integrally with the retaining wall block 14, first, the protective tube 12a and the optical fiber 1 are first displaced.
2 is deformed (see FIG. 5B). If the relative displacement is large, the deformation of the protection tube 12a becomes large (or breaks), and the optical fiber 12 is broken (see FIG. 5C). .

In FIGS. 5 (a), 5 (b) and 5 (c),
A pair of optical fiber holding portions 31a of one connecting member 31
Function as guide means for guiding the movement of the other connecting member 32 in a direction orthogonal to the longitudinal direction of the optical fiber 12 (a direction orthogonal to the central axis of the two optical fiber holding portions 31a). The fiber 12 is given only a deformation force in the shear direction. As a result, when a displacement occurs between the adjacent retaining wall blocks 14 in a direction away from each other, the optical fiber 12 is bent or broken due to the relative displacement. FIG. 5A,
In (b) and (c), since the connecting members 31 and 32 are plate-shaped, the relative displacement between the connecting members 31 and 32 in the direction perpendicular to the longitudinal direction of the optical fiber 12 is different from each other. It is possible in any direction except the plate thickness of the members 31 and 32. For this reason, for example, even if one of the pair of adjacent retaining wall blocks 14 is displaced in the direction of being pushed out from the ground slope 10 (the direction of projection toward the road 2), the relative position between the retaining wall blocks 14 is similarly determined. The displacement affects the bending or breakage of the optical fiber 12. Conversely, FIG.
In the figure, the retaining wall blocks 14 on both sides in the horizontal direction are depressed toward the ground slope 10 around the joint 14a (vertical joint) where the optical fiber sensor 11 is installed. Although relative displacement occurs in the direction away from each other between 32, the optical fiber sensor 11 of the present embodiment can also detect such deformation of the retaining wall 13.

As shown in FIG. 5A, in the initial state,
The space 33 having a shape in which a part of one connecting member 31 of the optical fiber sensor 11 is cut out has a size substantially coincident with the optical fiber holding portion 32 a of the other connecting member 32. The optical fiber holding portion 32a is abutted against the portion 34, and the optical fiber holding portion 32a
No relative displacement between the connecting members 31 and 32 in a direction in which the connecting members 31 and 32 are pushed, that is, such that the connecting members 31 and 32 approach each other or overlap each other. Therefore, in the optical fiber sensor 11, the coupling members 31 and 32 are relatively displaced from each other, and the coupling members 31 and 32 are relatively rotated (rotation about the longitudinal direction of the protective tube 12a and the optical fiber 12). Such relative displacement is possible, and the deformation or the like of the retaining wall 13 that causes such displacement can be detected. In addition,
The configuration of the optical fiber sensor can be appropriately changed in design.For example, if a structure is adopted in which the optical fiber holding portions of both connecting members do not interfere with portions other than the optical fiber holding portion of the mating connecting member, the connecting member can be changed. Relative displacement such that they approach each other and overlap each other is also possible, and displacement that the adjacent retaining wall blocks 14 approach can also be detected.

The displacement between adjacent retaining wall blocks 14 includes:
In addition to the approach and separation between horizontally adjacent retaining wall blocks 14, the approach and separation between vertically adjacent retaining wall blocks 14 and the like also exist. For this reason, as shown in FIG. 2, the protective tube 12 a containing the optical fiber 12 is curved around the surface of the retaining wall 13, which is the monitoring target area, and joints 14 a between the horizontally adjacent retaining wall blocks 14 and the like. The optical fiber sensor 11 is installed by laying along the joints 14 b between the vertically adjacent retaining wall blocks 14, etc., so that the optical fiber sensor 11 can detect the displacement between the vertically or horizontally adjacent retaining wall blocks 14. I do. In addition, retaining wall block 1 due to soil thickness, etc.
The optical fiber sensor 11 can be appropriately detected at a position where the 4 itself may be deformed, and this can be detected (for convenience of explanation, reference numeral “11a” is given in FIG. 2). Although FIG. 2 shows the optical fiber sensor 11 including the connecting members 31 and 32 respectively connected to the monitoring object which is the retaining wall block 14, the optical fiber sensor 11 of the present invention is not limited to this. However, for example, a stable rock having little possibility of displacement, a road 2 component anchored to the stable rock, or the like is used as a monitoring reference object, and one of a pair of connecting members serves as the monitoring reference object. , And the other connecting member may be connected to the retaining wall block 14, which is an object to be monitored.

In the optical fiber sensor 11 as described above,
Since the structure is simple and the number of parts is small, manufacturing is easy and cost can be reduced. In addition, since it is easy to reduce the size, it can be installed even in a narrow installation place. Attachment to the object to be monitored is very simple because only the anchoring of the connecting members 31 and 32 and the like are performed.

As shown in FIG. 1, a branch connector such as a closure 9 is provided in an information box 8 provided in the middle of optical cables 5 and 6 which constitute a communication line connecting the transmission devices 3 and 4. A large number (multiple cores) of optical fibers 17, 18 of, for example, hundreds or thousands are installed and housed in the optical cables 5, 6, are connected to each other via a connection point 20, and the transmission devices 3, 4, A communication line is configured between them. In addition, a part of the optical fiber 17 of the optical cable 5 is allocated as a dedicated line for monitoring the retaining wall 13 which is an object to be monitored (referred to as “optical fiber 17a” for convenience of explanation). The optical fiber 12 on the optical fiber sensor 11 side is connected via a connection point 20 in the closure 9. Further, another part of the optical fiber 17 of the optical cable 5 has a dedicated maintenance line connected to the water intrusion detection module 40 for detecting water intrusion inside the information box 8 and the closure 9 and the temperature detection module for temperature detection. It is assigned as “optical fiber 17b” for convenience of explanation.
In FIG. 1, one end of the optical fiber 41 of the immersion detecting module 40 installed in the closure 9 is connected to the optical fiber 1.
7b and the other end of the optical fiber 41 are connected to the optical fiber 18 on the optical cable 6 side via the connection point 21, respectively, so that the optical fibers 17b and 18 of the optical cables 5 and 6 are connected via the optical fiber 41. It has become so. Since the optical cable 12b is provided between the retaining wall 13 of the optical fiber 12 and the closure 9, the optical cable 12b is protected from external force such as falling rocks. The optical fiber 12 is
The optical fiber of the optical cable 12b may be connected near the retaining wall 13 via a branch connection box or the like.

In FIG. 1, the connection point 19 between the optical fiber 17a and the optical fiber 12 of the dedicated monitoring line is a fusion splicing part,
A connection point 20 between the optical fiber 17 on the optical cable 5 side and the optical fiber 18 on the optical cable 6 side is a connector connection by an optical connector 22, and a connection between the optical fiber 17b of the maintenance exclusive line and the optical fiber 41 on the immersion detection module 40 side. Point 21
Is a fusion splicing, but the connection points 19, 20, and 21 are not limited to the above-described configuration, and a fusion splicing portion, a connector connection, or the like may be appropriately selected and applied. However, since the connector connection is excellent in connection workability, in this regard, it is advantageous that the connection points 19 and 21 are also the connector connection.

In addition, in the optical cable 5, it is possible to secure an empty optical fiber which is not connected anywhere, in view of the future expansion of communication lines. In FIG. 1, the closure 9 installed in the information box 8 is illustrated as a branch connector, but the branch connector is a closure directly provided on the optical cables 5 and 6 without using the information box 8.
For example, a closure provided in an overhead optical cable may be used. Even in this case, there is no change in the function of accommodating a connection portion between optical fibers. Further, the branch connection body is not limited to the closure, and various configurations such as a branch connection box, a termination box, and an optical distribution board can be adopted.

Meanwhile, the optical cables 5 and 6 are laid by burying underground, laying overhead, etc., and the installation positions of the information box 8 and the closure 9 are various, such as underground, on the ground, in the air, and in a building. The information box 8 is often installed underground or on the ground. For example, for an optical cable installed in an underground pipeline, the information box 8 is provided using a manhole or a handhole. In particular, an information box 8 installed outdoors (including underground) and a closure 9 stored therein.
It is preferable to take measures for waterproofing against inundation such as groundwater and rainwater, and measures against abnormal rise in internal temperature due to geothermal heat and sunshine. In view of this, it has been proposed. The immersion detection module 40 is configured to bend the optical fiber 41 by using the expansion of the hygroscopic swelling material due to the immersion or the floating of the buoyant due to the immersion as a driving force. Further, in FIG. 1, the installation position of the inundation detection module 40 is inside the closure 9, but is not limited to this, and may be installed outside the closure 9 in the information box 8. As the temperature detection module, a configuration or the like that bends the optical fiber 41 by using a deformation of a material having a large linear expansion coefficient, a deformation of a bimetal or a shape memory alloy as a driving force, or the like is adopted. The installation position of this temperature detection module is also determined inside the closure 9 and the information box 8.
It may be installed outside the inner closure 9. Note that the optical fiber sensor 11, the immersion detection module 41, and the temperature detection module may all be configured to break the optical fiber, but may be configured to give a deformation such as bending that does not break the optical fiber. It is preferable in terms of workability for recovery from malfunction due to any cause and cost reduction for reuse after abnormality detection.

The optical fibers 17a and 17b are connected to the optical pulse tester 50 by the monitoring unit 7 installed at the terminal of the optical cable 5. In FIG. 1, specifically, the optical fiber 1
7a is connected to the optical switch 23 via the optical fiber 16 and the optical connector 16a, the optical fiber 17b is directly connected to the optical switch 23, and the optical switch 23 connects the optical fiber 51 on the optical pulse tester 50 side to the optical fiber. 16, 17b
Are selectively connected to the optical fiber tester 50 in units of one fiber. Then, test light is incident on the optical fiber 17a or the optical fiber 17b connected to the optical pulse tester 50 to perform an optical test, and the optical fibers 17a, 17b
Further, by detecting deformation such as disconnection or bending generated in the optical fibers 12 and 41, occurrence of an abnormality can be grasped. The switching connection of the optical fiber 51 on the side of the optical pulse tester 50 to the optical fibers 17a and 17b by the optical switch 23 and the optical test are sequentially and automatically repeated in a predetermined order. Since the time required for the optical test itself is short, the connection of the optical pulse tester 50 to each of the optical fibers 17a and 17b and the optical test are repeatedly and continuously performed, thereby substantially reducing the optical line of the optical fibers 17a and 17b. Constant monitoring is realized.

In the optical test of the optical fibers 17a, 17b, 12, and 41, if the Fresnel reflected light and the loss increase are not observed from places other than the locations where backscattered light and optical loss occur at the connection points 19 and 21, etc. , 17b, 12, 41
No abnormality such as disconnection or bending has occurred in the optical line according to (test result is "normal"). However, if Fresnel reflected light or loss increase is observed from a place other than where the backscattered light or light loss occurs, it is understood that the optical fibers 17a, 17b, 12, 41 have abnormalities such as disconnection or bending (test). The result is "Anomaly detected"). Since the position of the abnormal part can be grasped from the return time of the return light by the optical test, it is possible to determine which of the optical fibers 17a, 17b, 12, 41 caused the abnormality.

The local displacement, deformation, collapse, and the like of the retaining wall 13 are grasped by detecting an abnormal portion in the optical fiber 12, and the water in the closure 9 is also detected in the optical fiber 41. It is grasped by doing. However, in the monitoring target area, two optical fibers 12 housed in one laid protective tube 12a are broken or deformed by the optical fiber sensor 11 (one of the two optical fibers 12). Only the case where only the break occurs exists in some cases). If an abnormal portion is detected in the optical fibers 17a and 17b, there is a possibility that a failure has occurred due to any cause such as erroneous cutting or mischief due to construction of the road 2. Accordingly, disconnection or abnormal bending of the optical cable 5 for communication can be detected by the optical test of the optical fibers 12 and 41, and the result of the optical test of the optical fibers 12 and 41 can be used for maintenance of the optical cable 5. Can also be used.

In order to connect the plurality of optical fibers 12 laid in the monitored area to the optical fiber 17a of the optical cable 5 by the same closure 9, the number of the optical fibers 12 in the optical fiber 17 in the optical cable 5 is required. The same number of cores is assigned as the optical fiber 17a of the dedicated monitoring line, and each optical fiber 17a is connected to the optical switch 23 so as to be switchably connectable to the optical pulse tester 50. In FIG. 1, four (four cores) optical fibers 12 are connected to two (two cores) and one (four cores) optical fiber 17 of the optical cable 5 for each one monitoring target area. Is assigned as the optical fiber 17a of the dedicated monitoring line (in FIG. 1, only one connection between the optical fibers 12 and 17 is shown, and the others are omitted). Each optical fiber 1 by the optical pulse tester 50
From the results of the optical test of 2, the abnormal location occurring in the monitoring target area can be grasped for each optical fiber 12 by the optical fiber sensor 11 unit, and the position of the abnormal location (optical pulse tester Optical fiber 1)
It can be grasped for every two by the optical fiber sensor 11 unit. The surplus length 24 of the optical fiber 16 is set to 1000 in the monitoring unit 7.
m, and the distance from the monitoring unit 7 is short,
The optical pulse tester 50 enables line monitoring of optical lines for which line monitoring is difficult. Since the optical fiber 16 is detachable from the optical fiber 17a by the optical connector 16a, the optical pulse tester 50 of the optical fiber 12 of the optical fiber sensor 11 can be selectively used by using the optical fiber 16 having an appropriate length. The distance from can be adjusted. The end of each optical fiber 12 (the end farther from the optical pulse tester 50) is subjected to non-reflection processing.

On the other hand, the maintenance dedicated optical fiber 17b is
It suffices to secure one core for the communication optical cable 5, and the presence or absence of occurrence of an abnormality can be easily determined by an optical test. The terminal 18a of the optical fiber 6 of the optical cable 6 connected to the optical fiber 17b via the optical fiber 41 of the immersion detecting module 40, which is farther from the optical pulse tester 50, is subjected to non-reflection processing.

FIG. 6 shows an example of the detection section 52 connected to the optical pulse tester 50. The detecting unit 52 includes the optical fiber 1
From the received light data of the return light by the light test of 7a and 17b,
In the position measurement unit 52a, the position (light pulse test) of the position where the Fresnel reflected light is generated or a significant light loss due to bending of the optical fiber (light loss of a certain level or more; the judgment level is set in advance). The distance read from the database stored in the storage unit 52b is compared with the position of the abnormal part obtained by the position measurement unit 52a by the comparison unit 52c. That is, in the comparing unit 52c, the data obtained by the optical test (the position of the abnormal part grasped by the position measuring unit 52a)
Then, a comparison is made as to whether or not data other than the location of the occurrence of backscattered light or light loss that can be recognized when the result of the light test is “normal” is included.

Data obtained by the light test, and
The “normal” data read from the storage unit 52b is output as an electric signal or the like from the output unit 52d, and is displayed on a map screen by the display unit 53 connected to the detection unit 52 in FIGS. Is displayed. In addition, the data obtained by the light test and the data at the time of “normal” read from the storage unit 52b are distinguishably displayed on the display unit 53 with different colors and the like, so that the data is very long. The location of the abnormal spot on Road 2 and its surroundings is clearly visible on the map screen.
It can be used for quick recovery work and disaster prevention measures. In addition, on the map screen, in addition to the abnormal location identified by the optical test of the optical fibers 12 and 41, the abnormal location (optical fiber 17
Displaying the abnormal points detected at a and 17b) can also be used for recovery from the failure of the communication line. The data output from the output unit 52d is
("HUB" in FIG. 6) or via the router 55, and may be transmitted to a display unit or the like of another management system. By integrating and displaying data from the plurality of optical monitoring devices 1 on a display unit of a road management system that monitors a wider area, for example, in the event of a wide-area disaster, it is useful for grasping the passable road 2 and providing information. be able to.

Further, the display section 53 can display, as detailed information, the presence or absence of occurrence of an abnormality for each optical fiber sensor 11 for each of one or a plurality of monitoring target areas monitored by the optical monitoring apparatus 1. Is preferred. That is,
In the monitoring target area, the position of the abnormal part is grasped for each of the two optical fibers 12 housed in one laid protective tube 12a. Therefore, the position of the abnormal part is grasped from both ends of the protective tube 12a. Thereby, for example, the range of deformation or collapse occurring in the monitoring target area can be grasped. Thereby, retaining wall 1
There is an advantage that it is possible to grasp the scale and the like of deformation and collapse of No. 3, and to take appropriate measures promptly. Since it can be seen that the range in which the monitoring target region has an abnormality exists between the break positions of the two optical fibers 12 or in a region slightly larger than that, the scale (area, area, Deformation width). If the installation density of the optical fiber sensor 11 in the monitoring target area is increased, the size, shape, and the like of the abnormal range in the monitoring target area can be grasped more finely. After one optical fiber 12 breaks, monitoring after the break point by the optical fiber 12 cannot be performed, but observation data is collected from the other optical fiber 12 so that the optical fiber 12 exists after the break point of the one optical fiber 12. The detection of the displacement or deformation of the monitoring target area by the optical fiber sensor 11 can be continued.

Further, since the protective tube 12a has plastic deformation performance, once deformed, the deformed state is maintained unless the deformation is returned intentionally. Even if the connecting member is detached for some reason and the external force that deforms the protective tube 12a is removed, the deformation of the protective tube 12a is maintained as it is, so that the optical fiber 12 is once deformed by the deformation of the protective tube 12a. If given, the state is maintained, and an abnormality can be detected by an optical test.

In FIG. 1, the communication line between the transmission devices 3 and 4 is constituted by connecting optical cables 5 and 6, but the number of optical cables to be connected may be larger.
The number is not limited. Further, the communication line is connected to another communication line, or branched by an optical splitter.
What constitutes a DS (Passive Double Star) line,
It goes without saying that a wide variety of configurations can be employed. The communication optical cable to which the optical fiber 12 on the optical fiber sensor 11 side is connected includes transmission devices 3 and 4.
The communication cables are not limited to those connecting between them, and various types of communication optical cables such as an optical cable connecting between the transmission device 3 and the terminal device can be employed.

If the number of optical cables constituting the communication line is not limited to the two optical cables 5 and 6, and if the number is larger, the number of information boxes 8 and branch connectors installed along the communication line will also increase. For example, the optical fiber 18 of the optical cable 6 may be connected to the optical fiber 18 of the optical fiber sensor 11 or the water immersion detection module 40 by a branch connector installed at a terminal farther from the optical pulse tester 50 of the optical cable 6. When the optical fiber 41 is connected, a part of the large number of optical fibers 18 in the optical cable 6 is allocated to a dedicated monitoring line and a dedicated maintenance line. The connection of the optical fiber 17 on the optical cable 5 side to 18 does not need to be changed. Further, even when a branch connector such as a closure is installed on the side far from the optical pulse tester 50 via another communication optical cable connected to the optical cable 6, the connection between the optical fibers between the communication optical cables is the same. It is. This allows
The optical fiber 12 connected to the optical fiber of the communication line at a position farther from the optical pulse tester 50 than the closure 9
Is also connected to the optical pulse tester 50 via the optical fiber of the optical cable of the communication line. In addition, it is preferable that the optical fibers of the inundation detection module 40 and the temperature detection module installed in a plurality of branch connectors and information boxes are connected in series via the optical fibers of the optical cables 5, 6,. , Only one of the communication lines composed of the optical cables 5, 6,... Needs to be allocated as a maintenance dedicated line, and more of the optical fibers in the optical cables 5, 6,. It can be assigned to a dedicated monitoring line. Further, in the above-described embodiment, the line monitoring is performed only on the optical lines related to the optical fibers 17a and 17b. However, the optical line related to the optical fiber 17 of the communication line is also connected to the optical pulse tester 50 to disconnect the cable. May be monitored.

The optical monitoring device 1 can be easily constructed simply by connecting the optical fiber 12 of the optical fiber sensor 11 to the optical fibers of the optical cables 5, 6,..., And exists at a plurality of locations along the long road 2 in the longitudinal direction. Displacement, deformation, collapse, and the like of the monitoring target can be monitored at one monitoring location installed in a safe place away from the monitoring target. In addition, at the monitoring location, the displacement or deformation of the monitoring target at each location where the optical fiber sensor 11 is installed is determined by information displayed on the display unit 53 or an alarm that is issued when the detection unit 52 detects an abnormal location. , Collapse, etc., can be immediately grasped, so that quick recovery work can be performed, and responsiveness can be obtained. Also, a branch connector such as a closure 9 is installed at an appropriate position of the optical cables 5, 6,... And the optical fiber 12 of the optical fiber sensor 11 is connected to the optical fibers of the optical cables 5, 6,. This can be freely performed by the fiber sensor 11.
In addition, there is no problem of securing the visibility like the ITV.

Further, since the optical fiber sensor 11 can be obtained at a lower cost than an image pickup device such as an ITV, the cost can be significantly reduced, and a wide range of monitoring and monitoring of a plurality of locations can be realized at a low cost. In addition, the optical monitoring device 1 directly monitors the movement of earth and sand by the optical fiber sensor 11 installed in the ground to be monitored by burying the ground, so that a strain gauge that detects only the occurrence of distortion, a visual inspection patrol, and the like. And the occurrence of ground displacement, deformation, and the like, which cannot be confirmed by monitoring with an ITV image, can be used for disaster prevention. In addition, the optical monitoring device 1 has no electrical operation unit other than the optical pulse tester 50 and the display unit 53 installed at the monitoring place, and there is no fear of being affected by an induced current due to a lightning strike or the like. If only the pulse tester 50 and its attached instruments are protected so as not to be affected by the induced current, the monitoring performance will not be impaired even if they are installed in a mountainous area where a lightning strike is likely. The degree of freedom of the installation location is greatly improved.

The present invention is not limited to the above-described embodiment. For example, the details of the optical fiber sensor and the structure of the monitoring unit for the optical test of the optical fiber of the optical fiber sensor can be changed as appropriate. Needless to say. The optical fiber holding portion provided on the connecting member constituting the optical fiber sensor is not limited to the tubular shape housing the protective tube,
A configuration such as a gripping claw for gripping the protection tube can also be adopted. In the present invention, an optical cord or an optical cable may be adopted as the optical fiber. In this case, the protective tube can be omitted. If the protective tube is omitted, the optical fiber holding section has a configuration for holding the optical fiber itself. In the above-described embodiment, the configuration in which the pair of connecting members are attached to the optical fiber via the optical fiber holding unit has been described. However, in the present invention, for example, a single monitoring target object may be separated by one optical fiber sensor. And a configuration in which three or more connecting members connected to the monitoring reference object are attached to the same optical fiber. That is, even in this configuration,
It is considered that the deformation or breakage of the optical fiber, such as bending, is caused between the optical fiber holding portions of the pair of connecting members.
Included in the present invention. The monitoring target (the installation position of the optical fiber sensor) of the optical monitoring device to which the optical fiber sensor of the present invention is applied is not limited to the ground slope facing the road, but the ground itself forming the road, the pavement of the road, and the road side. Mountain slopes, cliffs, etc. that fall downward from the part are also included. Roads include elevated roads made of reinforced concrete, etc.
Local, displacement, deformation, collapse, etc. of this elevated structure can also be monitored. In addition, other than a road through which cars and people pass, for example, a roadbed of a railway track, a cliff around the track, or the like is adopted as a monitoring target. The objects to be monitored are not limited to traffic facilities such as roads and railway tracks, and the surrounding ground, etc. Structures and the like are also included, and it is possible to detect these signs and signs, such as displacement, deformation, and collapse. In recent years, the laying of optical cables for communication using roads, railway tracks, river embankments and the like has been rapidly expanding, and the optical fiber sensor of the present invention uses the optical fiber of the optical cable for communication. Thus, it can be easily connected to the optical pulse tester.

[0045]

According to the optical fiber sensor of the first aspect, the optical fiber holding portions provided on the pair of connecting members respectively connected to the monitored object and the monitored reference object are provided with the optical fiber holding portions. When the optical fibers are brought close to each other while holding different positions in the longitudinal direction, and the displacement of the monitored object between the monitored objects or the monitored reference object occurs, the optical fiber is deformed by bending or the like due to relative displacement between the connecting members. Or because it is designed to break,
By monitoring and detecting this by an optical fiber optical test using an optical pulse tester, the displacement and deformation of the monitored object can be monitored with high accuracy, and the signs of disasters such as landslides and landslides can be captured. It can be used for disaster prevention measures. In addition, since the structure can be simple, the cost can be reduced. In addition, since it can be installed at the target position simply by connecting the connecting member to the monitoring object or monitoring reference object, construction is easy, even if it is installed in a large number of monitoring target areas,
It has an excellent effect that it can be constructed in a short construction period.

According to the optical fiber sensor of the second aspect, there is provided a guide means for guiding the one connecting member so that the other connecting member moves in a direction orthogonal to the longitudinal direction of the optical fiber. Since the moving direction of the connecting member is a direction orthogonal to the longitudinal direction of the optical fiber, the optical fiber is more efficiently deformed in the shearing direction, and the bending deformation of the optical fiber, the further This has an excellent effect that the optical fiber is reliably broken due to an increase in the relative displacement of the optical fiber.

According to the optical fiber sensor of the third aspect, since the optical fiber is housed in the plastically deformable protective tube, the protective tube is deformed after the optical fiber is bent or deformed by the deformation of the protective tube. Unless the optical fiber returns to the original shape by another external force, the deformation of the optical fiber does not return to the original shape. Therefore, an excellent effect that the deformation such as bending of the optical fiber can be reliably detected by the optical test is provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical fiber sensor according to an embodiment of the present invention, and is an optical wiring diagram showing an application example to an optical monitoring device.

FIG. 2 is a perspective view showing an installation state of the optical fiber sensor according to the present invention on a retaining wall.

FIG. 3 is a cross-sectional view showing a structure of a protective tube applied to the optical fiber sensor of FIG.

4A and 4B are front views showing the operation of the optical fiber sensor of FIG. 2, wherein FIG. 4A shows a state before the retaining wall is deformed, and FIG. 4B shows a state after the retaining wall is deformed.

5A and 5B are enlarged views showing details of the optical fiber sensor of FIG. 2, wherein FIG. 5A shows a normal state (no partial displacement or deformation occurs in the retaining wall), and FIG. (C) shows a state in which the optical fiber is bent by the displacement of the retaining wall block, and (b) shows a state in which the optical fiber is broken by the displacement between the retaining wall blocks.

FIG. 6 is a block diagram illustrating an example of a configuration of a detection unit in the optical monitoring device in FIG. 1;

[Explanation of symbols]

11, 11a: optical fiber sensor, 12: optical fiber,
12a: protection tube, 13: monitoring object (retaining wall), 14: monitoring object (retaining wall block), 31, 32: connecting member, 3
1a, 32a: Optical fiber holding unit.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kazuya Ogata 1440 Mukurosaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Office (72) Inventor Koichi Katayose 1440 Mutsuzaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Office (72) Inventor Yoshikazu Nomura 1440 Mutsuzaki, Sakura City, Chiba Prefecture Inside Fujikura Sakura Plant (72) Inventor Shoji Ueno 2-61-5 Torocho, Omiya City, Saitama Prefecture Applied Geology Co., Ltd. (72) Inventor Mizuno Toshimi 2-61-5 Torocho, Omiya City, Saitama Prefecture Applied Geology Co., Ltd. (72) Inventor Hiroya Motoki 2-61-5 Torocho, Omiya City, Saitama Prefecture Applied Geology Co., Ltd. F-term (reference) 2G086 CC03 DD01 DD05 2H038 AA03 AA05

Claims (3)

[Claims] 1. Displacement and deformation of a monitored object such as an unstable stratum that is likely to collapse, a natural object such as rock that is likely to be displaced, or an artificial structure such as a retaining wall (13) is detected by light. An optical fiber sensor to be monitored, wherein the monitoring target object may be displaced with respect to a monitoring target object located at a different position from each other, or a monitoring reference object made of stable rock or the like and the monitoring reference object. And a pair of connecting members (31, 32) separately connected to the optical fiber holding portion (31) for holding the optical fiber (12).
a, 32a) are provided, and these optical fiber holding portions are close to each other while holding different positions in the longitudinal direction of the optical fiber, and the optical fiber is deformed by bending or the like due to relative displacement between the connecting members. Alternatively, an optical fiber sensor (11) characterized in that it causes breakage. 2. A guide means (31a) for guiding one connecting member so that the other connecting member moves in a direction perpendicular to the longitudinal direction of the optical fiber. 2. The optical fiber sensor according to 1. 3. The optical fiber is housed in a plastically deformable protective tube (12a), the optical fiber holding portion holds the protective tube, and the protective tube is deformed by a relative displacement between the connecting members. 2. The optical fiber according to claim 1, wherein the optical fiber is deformed or broken.
Or the optical fiber sensor according to 2.