JP2005337831A - Optical fiber sensor composite cable and network for optical fiber monitoring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized optical fiber composite cable capable of detecting a strain in a wide range with the small number when, for example, integrated into a disaster prevention network, and reducing cost of an optical fiber monitoring system, and executable without damaging an appearance. <P>SOLUTION: This optical fiber composite cable is formed by burying an optical fiber wherein at least one optical fiber grating type strain sensor is formed, into a reinforcement comprising an elastic body. As for the reinforcement, the elastic module of a sensor coating part for coating a part where the optical fiber grating type strain sensor is formed is set to be lower compared with other parts. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is an optical fiber sensor composite cable including an optical fiber partially formed with a strain sensor and a net having the optical fiber sensor composite cable, and is mainly used in an optical fiber monitoring system for crime prevention and disaster prevention. The present invention relates to an optical fiber monitoring system net.

In recent years, strain sensors using light and optical fiber monitoring systems using optical fibers have been widely used for crime prevention and disaster prevention.
For example, as an approach detection system, a method is known in which an optical fiber is built in a barbed wire, and the intrusion is detected by detecting a transmission loss due to distortion of the optical fiber while preventing the penetration by the barbed wire.

  Further, as a conventional defense management system, for example, there is a rock fall information management system using a fiber grating type optical fiber sensor (hereinafter also abbreviated as FBG sensor) disclosed in Patent Document 1. In this rock fall information management system, a rock fall prevention net (FIG. 17A) composed of a plurality of wire ropes 101 is placed on a rock to prevent rock fall and the ends of the wire lobe 101 are fixed with anchor bolts. The FBG 102 is attached to the rope 101 for monitoring.

  In this rockfall information management system, a strain sensor 105 configured to include an FBG sensor for detecting wire rope distortion is fixed at appropriate locations on the wire rope 101 by a fastening portion 104 (FIG. 17B). doing. As shown in FIG. 17B, the strain sensor 105 is connected to the strain measuring device 106 by a signal transmission optical fiber cable 103.

  The fiber optic grating type strain sensor used in this defense management system is a sensor with excellent detection sensitivity that can detect dynamic strain of the microstrain order. This utilizes the phenomenon that only the corresponding specific wavelength (Bragg wavelength) is selectively reflected in the fiber grating. That is, when strain is applied to the detection element portion (length is, for example, 10 mm), the period of the fiber grating changes, so that a shift occurs in the wavelength of the reflected light, and the amount of distortion added from the shift amount of the wavelength is calculated. It can be measured.

  As an optical fiber grating type strain sensor, for example, as disclosed in Patent Document 2, an affixed structure is proposed in which the FBG 102 is bonded to a film 109 and the film is placed on an object to be detected ( FIG. 18). In other words, it is a structure in which the film 109 is surface-bonded or surface-bonded with an adhesive 111 obtained by uniformly and thinly stretching the film 109 at a detected location, the FBG 102 is covered with the resin 110, and the resin 110 is shaped into a film and cured.

  There has also been a method of detecting intrusion by detecting distortion by the bending condition of the optical fiber. 19A and 19B show a conventional optical fiber cable for strain detection. This is a sensor cable for detecting intrusion by sensing a change in transmission loss due to bending of a fiber, and includes a spacer 202 made of an elastic body having a groove formed on the outer peripheral portion, and at least one of the grooves housed in the groove. An optical fiber 204 and a tensile strength fiber 205 spirally wound around the outer periphery of the spacer are housed in a sheath 206. When tension is applied to the optical fiber cable configured as described above, a centripetal force acts on the tensile strength fiber 205 and the spacer 202 is tightened by the tensile strength fiber 205. When the tension exceeds a predetermined tension, the deformation of the spacer 202 becomes large, and the tensile strength fiber 205 is tightened in a state where the optical fiber in the groove of the spacer is wound. As a result, the optical fiber is bent to increase the loss. By measuring the increase in the transmission loss, it is detected that a tension is applied to the sensor cable 204. This system is described in Patent Document 3.

Optical fibers are also used in systems that detect concrete damage in invisible areas. FIG. 20 shows a damage detection unit using an optical fiber disclosed in Patent Document 4. This damage detection unit has a strain sensor formed between a concrete structure and a reinforcing material by bending a continuous optical fiber cable 307, knitting with a fixing warp 303 into a net shape, and pulling out the optical fiber. The progress of damage is confirmed by measuring strain by detecting Brillouin scattered light from one end of the cable.
Japanese Patent No. 3150943 JP 2001-296110 A JP 5-2689 Patent No. 29811206

However, as shown in FIG. 18, the conventional optical fiber grating type strain sensor is used by being fixed to a tape or the like and adhered to a test object with a surface. For example, the container is tied to a thick rope. Since it was configured, there was a problem that it was not suitable for small ones.
In addition, the conventional optical fiber grating type strain sensor has a problem that it is necessary to increase the number of sensors when incorporated in a disaster prevention net or the like.
Furthermore, in the method of detecting an abnormality using an optical fiber cable, the location where the abnormality has occurred cannot be accurately identified, the strain detection sensitivity is low, and dynamic fluctuations such as measuring strain over time are not possible. There was a problem in detection.

  Accordingly, the present invention is an optical fiber that is small in size and capable of detecting a wide range of strains with a small number when it is incorporated into a disaster prevention net, for example, can reduce the cost of an optical fiber monitoring system and can be installed without impairing the appearance. It is a first object to provide a sensor composite cable.

  A second object of the present invention is to provide an optical fiber monitoring system net that can detect a wide range of strains with a small number of optical fiber grating strain sensors.

  In order to achieve the above object, an optical fiber sensor composite cable according to the present invention is an optical fiber in which an optical fiber in which at least one optical fiber grating type strain sensor is formed is embedded in a reinforcing material made of an elastic body. In the sensor composite cable, the reinforcing material is set such that an elastic modulus of a sensor covering portion covering a portion where the optical fiber grating type strain sensor is formed is lower than that of other portions. .

Since the optical fiber sensor composite cable according to the present invention configured as described above is configured by using an optical fiber in which an optical fiber grating type strain sensor is integrated in part, the sensor unit can be extremely small. In addition, the strain transmitted to the part other than the sensor part can be effectively transmitted to the optical fiber grating type strain sensor by the high elastic modulus cable, and can be detected with high sensitivity by the low sensor covering part.
Therefore, for example, it can be attached to a net made of a relatively thin thread used in ordinary households, schools, etc., and even in that case, the scenery does not deteriorate, and the sensor part protrudes and becomes an obstacle. There is nothing.
In addition, when used in an optical fiber monitoring system net, the number of installed fiber optic grating strain sensors can be reduced without lowering the detection sensitivity, and strain can be detected over a wide range of surfaces. The low cost of the fiber monitoring system can be realized.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
Embodiment 1 according to the present invention relates to an optical fiber sensor composite cable including an optical fiber in which an optical fiber grating type strain sensor (FBG) 2 is partially formed.

  Specifically, the optical fiber grating type strain sensor 2 is configured by embedding an optical fiber 1 formed in a part thereof in a fiber reinforced plastic, and in the fiber reinforced plastic covering the optical fiber 1, The elastic modulus is different between the portion where the fiber grating type strain sensor 2 is formed (sensor covering portion) and the other portion. As described later, the other part has a function of applying a bending stress to the sensor covering part by using an external force received by the net part of the fence as a rotational moment, and is hereinafter referred to as an external force transmission part.

  That is, in the optical fiber sensor composite cable of the first embodiment, the elastic modulus of the fiber reinforced plastic of the sensor covering portion 4 is set to be lower than the elastic modulus of the fiber reinforced plastic of the external force transmitting portion 5, and the sensor covering portion 4. The tension applied to the other optical fiber sensor composite cable is transmitted to the sensor covering portion 4 so that the optical fiber grating type strain sensor (FBG) can be applied to any position of the optical fiber sensor composite cable. ) 2 to enable detection.

  Hereinafter, some examples of the manufacturing method of the optical fiber sensor composite cable according to the first embodiment will be described.

<First manufacturing method>
In the first manufacturing method, first, an optical fiber 1 having an optical fiber grating type strain sensor (FBG) 2 formed in a part thereof is prepared as shown in FIG. 1A. The optical fiber 1 is covered with, for example, a color resin.
Next, a cylindrical sleeve formed by knitting fibers, which is loosely knitted so that the portion in which the optical fiber grating type strain sensor (FBG) 2 is accommodated is more easily expanded and contracted than the other portions. Then, the optical fiber 1 of FIG. 1A is passed through (FIG. 1B), and the resin is poured into the inside and outside of the sleeve.
Here, for example, an alumina fiber is used as the plastic reinforcing fiber, and a sleeve 3 having an inner diameter of 0.8 mm produced by knitting the alumina fiber into a cylindrical shape is used. Moreover, the sensor coating | coated part 4 in which FBG2 is located makes fiber filling rate small about 25% compared with another part, for example.

  When molding the resin, the sleeve 3 is fixed to a concave casting mold having a curvature radius of 1.8 mm at the bottom, and a transparent epoxy resin is poured and cured as a matrix resin of fiber reinforced plastic (curing time). Is different depending on the resin, for example, it is cured for 3 days). In the casting mold, the sleeve 3 and the optical fiber 1 can be fixed so that the optical fiber protrudes from the sleeve 3 and the optical fibers at both ends are pressed against the sleeve. In addition, it is preferable to draw a release sheet or apply a release agent to the casting mold in advance.

As described above, the optical fiber sensor composite cable in which the optical fiber 1 is embedded in the fiber reinforced plastic shown in FIG. 1C can be manufactured.
In the optical fiber sensor composite cable produced in this way, the fiber of the sleeve 3 is loosely knitted in the portion where the optical fiber grating type strain sensor 2 is accommodated. Can be made lower than other parts of fiber reinforced plastic (high elastic modulus external force transmission part 5 -low elastic modulus sensor covering part 4 -high elastic modulus external force transmission part 5).
In this optical fiber sensor composite cable, the tension applied to the optical fiber sensor composite cable other than the sensor coating portion 4 is transmitted to the sensor coating portion 4 to expand and contract the optical fiber grating type strain sensor 2 of the sensor coating portion 4.

<Second production method>
In the second manufacturing method, first, the optical fiber 1 of FIG. 1A is passed through a sleeve made of an aramid fiber (aromatic polyamide fiber) having an inner diameter of 0.5 mm, for example, and impregnated with a resin. Curing is performed to produce a first fiber reinforced plastic wire.
Next, the first fiber reinforced plastic wire is passed through, for example, a sleeve made of alumina fiber having an inner diameter of 1.3 mm, and the matrix resin is gradually soaked from both ends, and the resin is sufficiently soaked in the outer sleeve. , Cure.
As described above, the sensor coating portion 4 which is thinner and has a lower elastic modulus than the other portion reinforced with the aramid fiber, and the external force having a thick and high elastic modulus double-reinforced by the aramid fiber and the outer sleeve on both sides thereof. The optical fiber sensor composite cable shown in FIG.

<Third production method>
In the third manufacturing method, a part of the 0.8 mm inner diameter sleeve made of the alumina fiber used in the first manufacturing method is pulled and thinned, and the optical fiber grating type strain sensor 2 is formed in the thinned portion. Is positioned so that the optical fiber 1 is passed through the sleeve.
Then, the entire sleeve 3 is impregnated with resin, dried and cured.
As described above, it is possible to manufacture the optical fiber sensor composite cable shown in FIG. 2B, which includes the sensor covering portion 4 that is thinner than other portions and has a low elastic modulus, and the thick external force transmission portions 5 that are thick on both sides thereof. it can.

  In the present invention, an optical fiber sensor composite cable embedded in a fiber reinforced plastic having a high elastic modulus-low elastic modulus-high elastic modulus can be easily manufactured by various methods other than the method described above.

Next, an example of integration with the network of the optical fiber sensor composite cable of the first embodiment (an example of incorporation into the network) will be described.
In the optical fiber sensor composite cable according to the first embodiment, the rigidity of the external force transmission unit 5 other than the sensor coating unit 4 is set to be relatively high. Therefore, when attaching to a wire mesh with a relatively small mesh, simply pass through the wire mesh using the rigidity of the wire mesh and the rigidity of the optical fiber sensor composite cable (especially the rigidity of the external force transmission part other than the sensor cover). It can be fixed (FIG. 3A, FIG. 3B).

3A and 3B show an example in which a stainless steel wire having an outer diameter of 0.5 mm is fixed to a wire mesh 6 knitted by spiral knitting as a thread through an optical fiber sensor composite cable.
Further, when the mesh of the wire mesh is large and the optical fiber sensor composite cable cannot be fixed firmly, as shown in FIG. 4, it can be firmly fixed by making the mesh of the wire mesh partially fine.
As described above, the optical fiber sensor composite cable according to the first embodiment can be easily incorporated into the wire mesh by adjusting the size of the wire mesh stitches as necessary using its rigidity.

<Example of installation in an optical fiber monitoring system>
FIG. 5A shows an installation example in which the optical fiber sensor composite cable of the first embodiment is incorporated in an optical fiber monitoring system net. In this example, similar to the one used in FIG. 3, a wire knitted by spiral knitting using a 0.5 mm stainless wire as a thread is connected, and two 1 m long and 2 m wide wire meshes 6 are connected and supported by a pillar 8. . In the present invention, a rigid optical fiber composite cable may be incorporated for each network, and the connection portion between the optical fiber composite cables in the portion connecting the two networks is shown in FIG. As shown to 5B, you may be connected by the flexible optical fiber F5. 5B is an enlarged view showing a connection portion between the optical fiber composite cables in a portion where the two nets in FIG. 5A are connected, and FIG. 5C is a view showing a modification thereof. Since the strain transmission distance of the wire mesh 6 (which depends largely on the material of the wire mesh) was 50 cm, in this example, the single optical fiber sensor composite wire of the first embodiment (FIG. 1) is connected to the wire mesh. It was passed through the stitches in the center according to the elasticity. With this arrangement, the shortest distance to the optical fiber sensor composite cable is within 50 cm in any part of the wire mesh, and any force applied to any part of the wire mesh is transmitted to the optical fiber sensor composite cable. Here, an optical fiber in which two optical fiber grating type strain sensors 2 are formed is used, and one sensor 2 is arranged in each network. For comparison, FIG. 5D shows an example in which a conventional commercially available bonded optical fiber grating strain sensor is wound and fixed with a thread made of an aramid fiber.

  In the example using the optical fiber sensor composite cable of Embodiment 1 shown in FIG. 5A, for example, the force applied to the location 7 is transmitted to the optical fiber sensor composite cable at the shortest distance, and the transmitted force is Further, the optical fiber sensor composite cable was transmitted without being attenuated in the direction of the arrow 10, and the optical fiber grating type strain sensor 2 inside the sensor coating portion 4 detected the strain. Similarly, when a force was applied to another part of the wire mesh, the optical fiber grating type strain sensor 2 inside the sensor coating 4 detected the strain.

  As described above, only one optical fiber sensor composite cable is provided at the center of the wire mesh. However, no matter where the force is applied to the wire mesh, it is transmitted to the optical fiber sensor composite cable, and the optical fiber grating strain sensor 2 is distorted. Was detected.

  On the other hand, in the case of the comparative example 1, since the optical fiber 101 does not have the strain transmission capability, the strain of the wire mesh that can be detected by the optical fiber grating type strain sensor 102 is that the strain transmission distance of the wire mesh is 50 cm. It is limited to a circle with a radius of 50 cm centered on the strain sensor 102. Therefore, in order to be able to detect any force applied to any part of the wire mesh, it is necessary to attach a large number of optical fiber grating type strain sensors 102 as shown in FIG. 5D. . Specifically, the strain cannot be detected unless a total of 18 optical fiber grating strain sensors 102 are installed. Needless to say, as in this comparative example, the work of fixing many optical fiber grating type strain sensors 102 to the stainless steel wire of the metal mesh is extremely inefficient.

As described above, according to the optical fiber sensor composite cable of the first embodiment, it is possible to reduce the number of installation locations of the optical fiber grating type strain sensor without reducing the strain detection sensitivity in the optical fiber sensor monitoring system.
In addition, the installation when installing the optical fiber sensor monitoring system can be very simple, and the scenery can be provided without deteriorating the scenery.
On the other hand, in a conventional optical fiber sensor monitoring system using strain sensors, it is necessary to lay a large number of strain sensors, which not only requires a relatively expensive strain sensor but also requires a lot of work. Therefore, there is a problem that installation is expensive and the detection system for measuring the light source and light becomes large.

FIG. 6 shows another example in which the optical fiber sensor composite cable of the first embodiment is used in an optical fiber sensor monitoring system.
In this example, a net having the same material and structure as the example of FIG. 5 and having a vertical width of 1 m and a horizontal width of 5 m is used.
This example is particularly characterized in that the meshed fiber portions 7 are provided on both sides of the mesh so as to securely fix the optical fiber sensor composite cable. Thus, even when the length (width) of the wire mesh is increased, it is possible to expand the monitoring area by one strain sensor, and the number of strain sensors installed is 10 minutes compared to the conventional method. Can be reduced to 1 or less.

When the optical fiber sensor composite cable of the first embodiment described above is incorporated into a wire mesh for the purpose of application to an optical fiber monitoring system, the elastic modulus of the wire mesh may be smaller than the elastic modulus of the sensor coating portion 4. Thus, even when the mesh is relatively soft and abnormal strain is absorbed by the mesh and the strain is difficult to be transmitted to the sensor coating portion, the external force transmission portion 5 has received the elasticity because the elastic modulus of the external force transmission portion 5 is high. The stress is transmitted to the sensor covering portion 4 promptly and with almost no attenuation.
Further, since the elastic modulus of the sensor covering portion 4 in which the strain sensor 2 is embedded is low, the optical fiber grating type strain sensor 2 can be effectively distorted by the transmitted stress or vibration.

As described above, according to the optical fiber sensor composite cable of the first embodiment, the number of installed optical fiber grating strain sensors in the optical fiber sensor monitoring system can be reduced, and the cost can be reduced. A wider area becomes possible.
Further, since the optical fiber sensor composite cable can be integrated by passing it through a net, the appearance is not impaired. Also, the workability is good, and the optical fiber grating strain sensor integrated with the wire is built into the net, so the optical fiber grating strain sensor does not fall off and the reliability and safety are improved. The place is not limited.
In addition, if the fiber optic cable is stretched and the sensor unit is protruded and attached as in the conventional case, not only the appearance will be damaged, but there is a risk of damage or dropping, and the installation location is limited. The optical fiber sensor composite cable according to mode 1 has no such inconvenience.

  Furthermore, since the structure is such that the optical fiber is coated with fiber reinforced plastic, its elastic modulus can be controlled by the wire diameter, the type of fiber contained in the fiber reinforced plastic, the fiber packing density, and the type of resin. is there. As a result, the elastic modulus of the optical fiber sensor composite cable can be controlled in accordance with the application such as the material of the net to be incorporated and the size of the region to be detected.

  Further, since the optical fiber sensor composite cable of the first embodiment is integrated by forming an optical fiber grating type strain sensor in a part of the optical fiber 1, the sensor portion does not protrude and is extremely small. it can. Therefore, for example, it can be attached to a net made of a relatively thin thread used at home, school, etc., and even in that case, the scenery does not deteriorate, and the sensor part protrudes and becomes an obstacle. There is nothing.

  In the first embodiment, the optical fiber sensor composite cable is configured using fiber reinforced plastic as a preferable example. However, the present invention is not limited to this, and the sensor covering portion 4 and the external force transmitting portion 5 It can comprise by the reinforcing material which consists of another elastic body which can vary an elasticity modulus between.

Embodiment 2. FIG.
The optical fiber sensor composite cable according to the second embodiment of the present invention is an optical fiber sensor composite cable in which an optical fiber on which an optical fiber grating type strain sensor is formed is embedded in a resin reinforcing material. Is an ellipse having a major axis and a minor axis, and the optical fiber is eccentrically provided in the minor axis direction from the center in the reinforcing material.
In the second embodiment, the cross-sectional shape of the reinforcing material is an ellipse, but the present invention is not limited to this, and a flat shape having a major axis and a minor axis so as to have anisotropic elasticity. If it is.

The optical fiber sensor composite cable according to the second embodiment configured as described above has anisotropy with different elasticity in the major axis direction and the minor axis direction due to the elliptical cross-sectional shape of the reinforcing material. In addition, since the optical fiber is embedded in an eccentric direction (short axis direction), the detection efficiency by bending is increased, and the sensitivity can be improved.
In addition, the variation in the zero strain wavelength in the absence of strain can be reduced, and the variation in the amount of wavelength shift from the zero strain wavelength when a constant stress is applied can be reduced.

Below, the manufacturing method of the optical fiber sensor composite cable of Embodiment 2 is demonstrated.
In this manufacturing method, an optical fiber 1 (FIG. 7A) on which an optical fiber grating type strain sensor 2 is formed is prepared, and, for example, passed through a sleeve 23 made of aramid fiber and having an inner diameter of 0.8 mm (FIG. 7B). Press the fiber into the sleeve.
Here, as the optical fiber 1, one coated with a color resin is used.

Next, the sleeve 3 through which the optical fiber 1 is passed is fixed to a concave casting mold having a curvature radius of 0.5 mm at the bottom, and a transparent epoxy resin is poured into it. The resin is cured while pressed with a mold. In addition, it is preferable to draw a release sheet in advance or apply a release agent to the casting mold.
For example, when the wire is taken out of the mold after being cured for 3 days, an optical fiber sensor composite cable in which the optical fiber 1 is embedded in the resin reinforcing material 24 shown in FIG. 7C is obtained.

  As shown in FIG. 8, the cross section of the optical fiber sensor composite cable produced in this way is an ellipse, and the position of the optical fiber grating type strain sensor 2 is deviated from the center in the minor axis direction.

The optical fiber sensor composite cable of Embodiment 2 manufactured as described above has elastic anisotropy that is easily bent in the minor axis direction, and high sensitivity to the force in the minor axis direction was obtained.
Further, in the optical fiber sensor composite cable of the second embodiment, (a) the optical fiber grating type strain sensor 2 is eccentrically embedded near the sleeve 3, and (b) the optical fiber grating type in the optical fiber. The portion where the strain sensor 2 is formed is colorless with the color resin coat being peeled off, while the other portion is colored with the color resin coat, (c) a resin reinforcing material using a transparent epoxy resin Is advantageous in that the position where the optical fiber grating type strain sensor 2 is embedded can be easily recognized from the outside. This is very convenient, for example, in assembling and laying in knitting.

  Three optical fiber sensor composite cables according to the second embodiment are manufactured by the above-described method, and for comparison, three wires are embedded without controlling the embedment position of the optical fiber having a cross-sectional shape close to a perfect circle. Made and compared. Of the three comparative examples, two were relatively close to the surface of the fiber optic grating strain sensor, but the other could confirm where the fiber optic grating strain sensor was. There wasn't.

A strain test was performed on these.
The three optical fiber sensor composite cables according to the second embodiment are gradually applied with a force parallel to the direction in which they are easily bent (the direction indicated by reference numeral 25 in FIG. 8), and the amount of distortion and the amount of wavelength shift. I investigated the relationship with. In addition, as for the comparative example, two optical fiber grating type strain sensors positioned relatively close to the surface are set in such a manner that the optical fiber grating type strain sensor is positioned in front and bent back and forth. Tests were conducted.

As a result, with respect to the three optical fiber sensor composite cables according to the second embodiment, the same center wavelength and wavelength shift were obtained with respect to the same bending amount. On the other hand, in the comparative example, the dispersion of the center wavelength and the wavelength shift is large, and the required specification in the intrusion detection system that requires multipoint measurement that performs detection with a wavelength shift of several nm is not satisfied.
Further, the wavelength shift amount with respect to the strain obtained in the comparative example was smaller than the wavelength shift amount obtained with the optical fiber sensor composite cable according to the second embodiment with respect to the same strain.
From the above results, in the optical fiber sensor composite cable according to the second embodiment, the strain applied to the wire is efficiently applied to the optical fiber grating type strain sensor, and the high sensitivity of the optical fiber grating type strain sensor is not wasted. You can save it.

  Furthermore, since the optical fiber sensor composite cable according to the second embodiment is manufactured by embedding an optical fiber in which an optical fiber grating type strain sensor is formed in a fiber reinforced plastic, it can be easily manufactured. It is also possible to adjust the elasticity of the wire according to the weight of the object, the magnitude of the stress, and the direction of the strain to be detected. As a result, malfunction can be prevented and reliability can be prevented. Can be improved.

Embodiment 3 FIG.
In the optical fiber sensor composite cable according to Embodiment 3 of the present invention, only the portion of the reinforcing portion 24 that covers the optical fiber grating type strain sensor is formed into a flat cross section having a major axis and a minor axis, and only the sensor covering portion. Has elastic anisotropy (FIGS. 9A and 9B).
9A and 9B are external views of the optical fiber sensor composite cable according to Embodiment 3 as viewed from two orthogonal directions. In the third embodiment, the sensor covering portion 26 is manufactured to have an elliptical cross section.

The optical fiber sensor composite cable according to Embodiment 3 can be manufactured as follows.
First, as in the second embodiment, the sleeve and the optical fiber are set in a casting mold, and then the resin is poured into the portion where the optical fiber grating strain sensor is formed, so that the optical fiber grating strain sensor (FBG) is accommodated. Fix the resin with a pressing jig that is short enough to cure the resin.
Next, the optical fiber at both ends is pulled to measure the tension so that the tension becomes zero and the resin is poured in a state where the optical fiber is positioned at the center of the sleeve.
After the pressing mold is set again, the height is adjusted again to adjust the tension to zero, and the poured resin is cured.
As described above, the optical fiber sensor composite cable of Embodiment 3 shown in FIGS. 9A and 9B can be manufactured.

According to the above process, three optical fiber sensor composite cables according to the third embodiment were manufactured, and a strain test similar to that of the second embodiment was performed. It was confirmed that there was almost no variation in wavelength shift.
Further, in the optical fiber sensor composite cable according to the third embodiment, the section of the reinforcing member 24 is circular in the portion of the optical fiber excluding the sensor covering portion 26, and the optical fiber 1 is arranged at the center of the circular reinforcing member 24. Therefore, in this portion, even if the optical fiber sensor composite cable is bent, the distortion of the optical fiber can be reduced.
Therefore, for example, when the optical fiber sensor composite cable is woven into the net and the optical fiber sensor composite cable is fixed, the optical fiber sensor composite cable of the third embodiment can reduce a decrease in transmission loss due to the bending of the wire when woven into the net. This is more advantageous than the optical fiber sensor composite cable of the second embodiment.
When the optical fiber sensor composite cable can be installed so that there is almost no bending, there is no inferiority between the optical fiber sensor composite cable of the second embodiment and the optical fiber sensor composite cable of the third embodiment.

Embodiment 4 FIG.
The optical fiber sensor composite cable according to the fourth embodiment further includes a reference optical fiber in which the optical fiber grating type strain sensor 2 is formed at the center of the reinforcing material in the optical fiber sensor composite cable according to the second embodiment. (FIG. 10), and an optical fiber grating type strain sensor of a reference optical fiber that hardly undergoes strain is intended to detect strain accurately and accurately with reference. FIG. 10 shows a cross section of the optical fiber sensor composite cable in the portion where the optical fiber grating type strain sensor 2 is formed.
In addition, although the cross-sectional shape of the wire rod in the portion where the optical fiber grating type strain sensor is embedded is an ellipse or a shape close thereto, other portions may have the same configuration as in the second embodiment with the cross-section being an ellipse. However, the cross section may be circular so that the configuration is the same as that of the third embodiment.

The optical fiber sensor composite cable of the fourth embodiment can be manufactured as follows.
First, two optical fibers provided with an optical fiber grating type strain sensor (FBG) are prepared, passed through a T glass fiber sleeve having an inner diameter of 1.3 mm, and set to a flow type having a curvature radius of 0.8 mm. In the sleeve, one optical fiber is fixed to the bottom, and the other one is the same as in the third embodiment, and the center of the sleeve is measured while measuring the tensile tension of the optical fibers at both ends so that the tension becomes zero. Set to. In this state, the resin is poured, and after setting the pressing die, the height of the optical fiber is adjusted again, and further, the tension is adjusted to be zero and cured as it is.
Through the above steps, the optical fiber sensor composite cable of Embodiment 4 can be manufactured.

  Next, when a strain test was performed on the optical fiber sensor composite cable according to Embodiment 4 of the present invention manufactured as described above, the optical fiber provided at the center of the wire has almost no wavelength shift with respect to the bending, and the center. It was confirmed that the optical fiber deployed in can be used as a reference optical fiber. This reference optical fiber can function as a temperature sensor, for example. In addition, the wavelength of the optical fiber deployed on the outside changed according to the bending, and the amount of distortion was obtained from the difference between the wavelength and the wavelength of the optical fiber deployed in the center. Such an optical fiber sensor composite cable according to Embodiment 4 of the present invention is suitable for installation in a place where a temperature change occurs relatively.

Embodiment 5 FIG.
In the optical fiber sensor composite cable according to Embodiment 5 of the present invention, the second optical fiber in which the optical fiber grating type strain sensor is further formed in the optical fiber sensor composite cable of Embodiment 4 is further extended from the center of the reinforcing material. It is characterized by being eccentric in the long axis direction. That is, in the fifth embodiment, one optical fiber is disposed at a position near the outer periphery on the minor axis of the ellipse, one at the center, and one at a position near the outer periphery on the major axis of the ellipse.

FIG. 11 shows a cross section of the optical fiber sensor composite cable according to the fifth embodiment in a portion where the optical fiber grating type strain sensor 2 is formed.
In addition, although the cross-sectional shape of the wire rod in the portion where the optical fiber grating type strain sensor is embedded is an ellipse or a shape close thereto, other portions may have the same configuration as in the second embodiment with the cross-section being an ellipse. However, the cross section may be circular so that the configuration is the same as that of the third embodiment.

  The optical fiber sensor composite cable of the fifth embodiment as described above can be manufactured by adjusting the position and tension of the optical fiber using a jig as shown in the third and fourth embodiments. it can.

The optical fiber sensor composite cable according to the fifth embodiment is suitable for use in, for example, a system in which a turbulent flow component is applied and multidirectional force is applied to the sensor. The optical fiber sensor composite cable of the fifth embodiment has elastic anisotropy and has a shape that is difficult to bend except in one direction. However, since the optical fiber grating strain sensor is sensitive, it is difficult to bend (long). When a force is applied in the axial direction, the strain applied in that direction can be measured.
The present inventors have confirmed through a laboratory-level simulation that the flow velocity can be measured by correcting these two disturbance parameters in the short axis direction and the long axis direction.
In addition, the optical fiber sensor composite cable according to the fifth embodiment can also measure temperature with a reference optical fiber arranged in the center.

  Further, in the optical fiber sensor composite cable according to the fifth embodiment, an optical fiber grating type strain sensor arranged at a position close to the outer circumference on the major axis of the ellipse as to whether or not a slight twist is generated in the bending of the wire. And the wavelength observed by the optical fiber grating type strain sensor placed in the center.

Embodiment 6 FIG.
Embodiment 6 according to the present invention is an optical fiber monitoring system net, and its configuration is shown in the plan view of FIG. 12A.
In the optical fiber monitoring system net of the sixth embodiment, the optical fiber sensor composite cable 30 in which the optical fiber grating type strain sensor 2 is formed is incorporated in the network 33 having an anisotropic elastic modulus. The elastic modulus of the mesh 33 in the direction parallel to the optical fiber grating strain sensor 2 is set lower than the elastic modulus of the optical fiber sensor composite cable 30, and the optical fiber grating strain sensor 2 of the mesh 33 is configured. The elastic modulus in the direction orthogonal to the optical fiber sensor composite cable 30 is set higher than the elastic modulus.

In the sixth embodiment, the mesh 33 has a low elastic modulus in one direction (high elasticity) and is knitted by spiral knitting so as to bend easily, and the optical fiber sensor composite cable 30 is incorporated in parallel to the one direction. Yes.
The net 33 is made of, for example, a braided iron wire with an outer diameter of 0.5 mm covered with vinyl, and an optical fiber wire is passed through the net of the net 33.

  In the sixth embodiment, the optical fiber sensor composite cable is formed by covering the optical fiber 1 in which the optical fiber grating type strain sensor 2 is written on a part thereof with a square line 34 with, for example, a vinyl tube 36. FIG. 12B shows a wire made of the optical fiber 1 and the square wire 34 before being covered with the vinyl tube 36. The optical fiber 1 has, for example, a square wire 34 having a cross section of 0.6 mm × 0.4 mm. The optical fiber grating type strain sensor 2 placed on the surface was fixed (molded) on the square line 34 with an elastic resin 35. FIG. 12C shows a cross section of the optical fiber sensor composite cable.

  In order to check the detection sensitivity of the net for the optical fiber monitoring system of the sixth embodiment, the optical fiber sensor composite cable is arranged so that the optical fiber grating strain sensor 2 is positioned at the center of the net 33 having a width of 6 m and a height of 1 m. An optical fiber monitoring system net provided in a direction perpendicular to the longitudinal direction of the net was produced. At the same height as the optical fiber grating type strain sensor 2, a force that protrudes 1 cm in the back (in a direction perpendicular to the surface of the net) was applied to the position 2 m laterally from the optical fiber sensor composite cable (this force). The point where A is added is point A). When such a force was applied, there was a protrusion of 0.5 cm or more at the point of symmetry of point A across the optical fiber grating type strain sensor 2.

  Next, when the same deformation test was performed at a point B at a height of 50 cm higher than the position of the optical fiber grating strain sensor 2 and 2 m away from the optical fiber sensor composite cable, an optical fiber grating strain sensor (FBG) was obtained. A large deformation of the net was confirmed at a symmetric point in almost the same way as in the experiment conducted at the same height.

  Next, the wavelength of the light reflected and returned by the optical fiber grating type strain sensor 2 was analyzed. The amount of wavelength shift when a force was applied to the two locations A and B was compared. As a result, the amount of shift applied to point B with respect to the amount of wavelength shift obtained at point A was 80% or more. When such an experiment was conducted on various parts of the network, the material and configuration of this network can be easily entered (network deformation) by providing only one optical fiber grating strain sensor (FBG) per 1 m × 4 m. ) Can be detected.

That is, in the optical fiber monitoring system net of the sixth embodiment configured as described above, the force received by the network 33 at a distance from the optical fiber grating strain sensor 2 is the optical fiber grating strain of the network 33. Since the elastic modulus in the direction orthogonal to the sensor 2 is high, it is easily transmitted in that direction.
Accordingly, the force received by the net 33 away from the optical fiber grating strain sensor 2 is efficiently transmitted in a direction orthogonal to the optical fiber grating strain sensor 2 and transmitted to the optical fiber sensor composite cable.

In the optical fiber monitoring system net of the sixth embodiment, since the elastic modulus is low in the direction parallel to the optical fiber grating type strain sensor 2 and it is easy to bend in that direction, the optical fiber sensor composite cable with a relatively small force. Since the (optical fiber grating type strain sensor 2) is bent, the strain detection sensitivity does not decrease.
Therefore, in the optical fiber monitoring system net of the sixth embodiment, the strain received away from the optical fiber sensor composite cable is detected by the optical fiber grating type strain sensor 2 with high sensitivity.

  As described above, in the optical fiber monitoring system net of the sixth embodiment, the strain applied to a part of the net is efficiently transmitted in the direction in which the net elastic modulus is high, and the direction in which the net elastic modulus is low. Is detected with high sensitivity by the optical fiber grating type strain sensor provided in the optical fiber grating, so that it is possible to detect a wide range of strains with one optical fiber grating type strain sensor 2, and the number of installed optical fiber grating type strain sensors. The cost can be reduced.

  Further, in the optical fiber monitoring system net of the sixth embodiment, a net knitted with a steel wire is used, and the net is knitted spirally so that the net originally has elastic anisotropy. Surface sensing can be realized easily without imparting anisotropy.

Embodiment 7 FIG.
FIG. 13: is a top view which shows the structure of the optical fiber monitoring system net | network of Embodiment 7 which concerns on this invention.
The net 33a used in the optical fiber monitoring system net according to the seventh embodiment is a knitted yarn made of aramid fibers having an outer diameter of 1 mm. The net 33a was flexible as a whole (high elasticity), and even if a force was applied to one place, only a part was deformed. Therefore, for example, an elastic rod 37 made of vinyl-coated iron was passed through the net 33a and assembled in parallel to the longitudinal direction (direction perpendicular to the optical fiber sensor composite cable). The optical fiber sensor composite cable was the same as that of the sixth embodiment, and was assembled so as to cross the elastic body rod 37.

That is, the net for the optical fiber monitoring system according to the seventh embodiment compares the elastic modulus in one direction with the other direction by passing the elastic rod 37 in one direction of the net 33a having almost no elastic anisotropy. The optical fiber sensor composite cable is incorporated in a direction perpendicular to the one direction.
Thereby, elastic anisotropy is imparted to the net 33a, and the same effect as in the sixth embodiment is obtained.

  In order to investigate the effect and detection sensitivity of the network of the seventh embodiment, as in the sixth embodiment, a network having an optical fiber grating type strain sensor (FBG) provided at the center of a network having a width of 6 m and a height of 1 m is manufactured. And evaluated. The net was horizontal to the ground. A weight of 10 kg from above was placed at a distance of 2 m in the longitudinal direction from the optical fiber grating strain sensor (FBG). Let this location be point C. There was more than 50% sinking of the net even at the point A symmetrical across the optical fiber grating type strain sensor (FBG).

  Next, when a similar deformation test was performed at point D, which was separated from the optical fiber grating strain sensor (FBG) by 50 cm, and further from the fiber by 2 m, the optical fiber grating strain sensor (FBG) was obtained. As in the experiment conducted at the same height, a large deformation of the net was confirmed at a symmetrical point.

On the other hand, in the net for the optical fiber monitoring system of the comparative example from which the elastic rod 37 was removed, there was almost no sinking of the net in the symmetrical portion with respect to the optical fibers at the points C and D.
Next, the wavelength of the light reflected and returned by the optical fiber grating type strain sensor 2 was analyzed using the optical fiber monitoring system net of the seventh embodiment. The amount of wavelength shift when a force was applied to the two points C and D was compared. As a result, the amount of shift applied to point D with respect to the amount of shift in wavelength obtained at point C was 80% or more.

  When such an experiment was carried out in various parts of the network, the material and configuration of this network can easily enter (deform the network) just by providing one optical fiber grating type strain sensor 2 in 1 m × 4 m. I found that I could detect it. On the other hand, in the net of the comparative example in which the elastic rod 37 was removed, almost no distortion due to the placement of the points C and D was detected.

As described above, according to the eighth embodiment, an elastic rod having a high rigidity is inserted in a direction perpendicular to the optical fiber grating type strain sensor (FBG), so that it can be easily and easily added to a net having no anisotropy. Elastic anisotropy can be easily imparted, and the same effect as in the sixth embodiment can be obtained.
In addition, the elastic anisotropy of the net can be easily adjusted by changing the number or rigidity of the bars inserted into the net. In addition, when adjusting the elastic anisotropy of the net by inserting a rigid rod into the net, the net itself may inherently have an elastic anisotropy. It does not have to be.

Embodiment 8 FIG.
As shown in FIG. 14, the optical fiber monitoring system net according to the eighth embodiment of the present invention is a large-scale net L33 (FIG. 14) in which a plurality of optical fiber monitoring system nets 33 according to the sixth or seventh embodiment are connected. In FIG. 6, one network 33 is provided with one optical fiber grating type strain sensor 2, and six optical fiber grating type strain sensors 2 are provided as a whole. . The optical fiber sensor composite cable 30 is attached so that the optical fiber grating type strain sensor 2 is located at the center of each net 33, and the optical fiber sensor composite cables are connected to each other between adjacent nets 33. . In addition, in FIG. 14, the part shown with the code | symbol 30a is a connection part of an optical fiber sensor composite cable.
Needless to say, the optical fiber sensor composite cable 30 may be composed of, for example, one of the six optical fiber grating type strain sensors 2 provided at regular intervals.

  As described above, an optical fiber monitoring system net in which one optical fiber sensor composite cable 30 in which a plurality of optical fiber grating strain sensors are provided in a plurality of nets is used as, for example, a protective net or a protective fence. It is easy to install and can be used in a wide range of applications without damaging the beauty and landscape.

As in the eighth embodiment, a large-scale network L33 is configured by combining a plurality of networks 33 (33a), and an optical fiber grating type strain sensor 2 is attached to each network 33 (33a) to connect an optical fiber. By connecting without branching, it is possible to detect the distortion received by each network without being influenced by the surroundings.
In addition, the system can be easily expanded by connecting and extending the networks in sequence, and there is no particular problem in detecting the wavelength of light.

As described above, in the sixth to eighth embodiments, the example using the net formed by spiral knitting has been described, but the present invention is not limited to this, and any one having elastic anisotropy can be used. A net knitted by other knitting methods may be used.
Further, even if the net itself does not have elastic anisotropy, for example, an elastic rod having a high elastic modulus is incorporated as in the seventh embodiment so as to have elastic anisotropy and is applied to the present invention. It is possible.

  For example, an optical fiber monitoring system net using a plain weave net 33b is shown in FIG. In the example shown in FIG. 15, the optical fiber sensor composite cable 1 is woven into a plain weave net 33b. The plain weave net 33b has high mass productivity, can be produced at a low cost, and can easily give elastic anisotropy by changing the distance between the warp and the weft, and the material and thickness. Furthermore, by incorporating a highly rigid rod, large elastic anisotropy can be imparted in the vertical, horizontal and diagonal directions. FIG. 16 shows an example of a network expanded by connecting the network 33b. In this example, a rod 37 having higher rigidity is incorporated in each net 33b to adjust the elastic anisotropy of each net 33b.

Moreover, although Embodiment 6-8 demonstrated the example using the net | network knitted with the thread | yarn by a metal, a fiber, etc., this invention is not limited to these materials.
Furthermore, the optical fiber sensor composite cable used in the present invention is not limited to the materials and configurations shown in the above-described embodiment, but adopts the optimal material and configuration of the optical fiber wires according to the system to be applied. can do.

As described above, according to the optical fiber monitoring system nets of the sixth to eighth embodiments and the modifications thereof according to the present invention, a wide range of strains can be detected with a small number of optical fiber grating strain sensors. A network for optical fiber monitoring systems can be provided.
In addition, an optical fiber grating type strain sensor capable of detecting dynamic strain can be adopted as the detection unit, and the number of installed optical fiber grating type strain sensors (FBG) can be reduced as much as possible without reducing the detection sensitivity. A network that can perform surface sensing can be manufactured and installed at low cost.
An optical fiber monitoring system suitable for wide-area monitoring can be provided at low cost.

It is a perspective view of the optical fiber used for the optical fiber sensor composite cable of Embodiment 1 which concerns on this invention. FIG. 5 is a perspective view when an optical fiber is inserted into a sleeve in the first manufacturing method of the first embodiment. 2 is a perspective view of an optical fiber sensor composite cable manufactured by the first manufacturing method in Embodiment 1. FIG. 6 is a perspective view of an optical fiber sensor composite cable manufactured by the second manufacturing method in Embodiment 1. FIG. FIG. 6 is a perspective view of an optical fiber sensor composite cable manufactured by the third manufacturing method in the first embodiment. It is a top view which shows an example which integrated the optical fiber sensor composite cable of Embodiment 1 in the net | network. It is a top view which shows the other example which integrated the optical fiber sensor composite cable of Embodiment 1 in the net | network. It is a top view which shows the other example which integrated the optical fiber sensor composite cable of Embodiment 1 in the net | network. It is a top view which shows the enforcement example of the optical fiber sensor monitoring system which integrated the optical fiber sensor composite cable of Embodiment 1 in the net | network. It is a figure which expands and shows the connection part between the optical fiber composite cables in the part which connected the two net | networks in FIG. 5A. It is a figure which shows the modification of FIG. 5B. It is a top view which shows the enforcement example of the optical fiber sensor monitoring system which attached the optical fiber grating type distortion sensor of the comparative example to the net | network. It is a top view which shows the enforcement example of the optical fiber sensor monitoring system different from FIG. 5A which integrated the optical fiber sensor composite cable of Embodiment 1 in the net | network. It is a perspective view of the optical fiber used for the optical fiber sensor composite cable of Embodiment 2 which concerns on this invention. FIG. 10 is a perspective view when an optical fiber is inserted into a sleeve in the first manufacturing method of the second embodiment. 6 is a perspective view of an optical fiber sensor composite cable manufactured by a first manufacturing method according to Embodiment 2. FIG. 6 is a cross-sectional view of an optical fiber sensor composite cable according to Embodiment 2. FIG. It is the perspective view which looked at the optical fiber sensor composite cable of Embodiment 3 which concerns on this invention from one direction. It is the perspective view which looked at the optical fiber sensor composite cable of Embodiment 3 which concerns on this invention from the other direction. It is sectional drawing of the optical fiber sensor composite cable of Embodiment 4 which concerns on this invention. It is sectional drawing of the optical fiber sensor composite cable of Embodiment 5 which concerns on this invention. It is a top view which shows the structure of the net | network for optical fiber monitoring systems of Embodiment 6 which concerns on this invention. FIG. 10 is a plan view showing an internal structure of an optical fiber sensor composite cable in a sixth embodiment. FIG. 10 is a cross-sectional view of an optical fiber sensor composite cable in a sixth embodiment. It is a top view which shows the structure of the net | network for optical fiber monitoring systems of Embodiment 7 which concerns on this invention. It is a top view which shows the structure of the net | network for optical fiber monitoring systems of Embodiment 8 which concerns on this invention. It is a top view which shows the structure of the net | network for optical fiber monitoring systems of the modification which concerns on this invention. It is a top view which shows the structure of the net | network for optical fiber monitoring systems of the other modification concerning this invention. It is a top view which shows the outline | summary of the conventional defense management system. It is a perspective view which shows the state which fixed the optical fiber grading type | mold distortion sensor to the wire rope. It is a perspective view which shows the example of attachment of the conventional paste type optical fiber grating type strain sensor. It is sectional drawing which shows the conventional optical fiber sensor cable. It is a perspective view which shows the internal structure of the conventional optical fiber sensor cable shown to FIG. 19A. It is a figure which shows the example in which the optical fiber was used in the system which detects the damage of concrete.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber, 2 Optical fiber grating type strain sensor, 3 Sleeve, 4 Sensor coating | coated part (low elastic modulus), 5 External force transmission part (High elastic modulus), 6, 33, 33a, 33b Net | network, 8 pillars, 30 Optical fiber Sensor composite cable, 30a Connection portion of optical fiber sensor composite cable, 34 square wire, 5 elastic resin, 36 vinyl tube, 37 elastic body rod.

Claims (17)

In an optical fiber sensor composite cable in which an optical fiber in which at least one optical fiber grating type strain sensor is formed is embedded in a reinforcing material made of an elastic body,
The optical fiber sensor composite cable, wherein the reinforcing material is set so that an elastic modulus of a sensor covering portion covering a portion where the optical fiber grating type strain sensor is formed is lower than other portions. .   2. The optical fiber sensor composite according to claim 1, wherein the reinforcing material has a coating thickness that covers the optical fiber grating type strain sensor made thinner than a coating thickness of the other portion, thereby adjusting an elastic modulus of the sensor coating portion. cable.   The optical fiber sensor composite cable according to claim 1, wherein the reinforcing material is made of fiber reinforced plastic.   4. The optical fiber sensor composite cable according to claim 3, wherein the elastic member has an elastic modulus adjusted by making the type of fiber contained in the sensor covering portion different from that of the other portion.   The optical fiber sensor composite cable according to claim 3, wherein the reinforcing member has an elastic modulus adjusted by making a filling density of reinforcing fibers in the sensor covering portion different from that of the other portions. An optical fiber monitoring system net in which the optical fiber sensor composite cable according to any one of claims 1 to 5 is incorporated in a network,
The net for an optical fiber monitoring system, wherein the elastic modulus of the net is set to be lower than the elastic modulus of the sensor covering portion of the optical fiber sensor composite cable. An optical fiber sensor composite cable in which an optical fiber in which at least one optical fiber grating type strain sensor is formed is embedded in a reinforcing material made of an elastic body,
The reinforcing material for embedding the optical fiber grating type strain sensor has a flat cross-sectional shape having a major axis and a minor axis, and the optical fiber grating type strain sensor is arranged in the minor axis direction from the center in the reinforcing material. An optical fiber sensor composite cable characterized by being provided eccentrically.   The optical fiber sensor composite cable according to claim 7, wherein the cross-sectional shape is an ellipse.   In addition to the optical fiber, the optical fiber grating further includes a second optical fiber on which at least one optical fiber grating type strain sensor is formed, and the second optical fiber is provided eccentrically from the center of the reinforcing material in the major axis direction. The optical fiber sensor composite cable according to claim 7 or 8.   10. The light according to claim 7, further comprising a reference optical fiber on which at least one optical fiber grating type strain sensor is formed, wherein the reference optical fiber is provided at the center of the reinforcing material. Fiber sensor composite cable.   The optical fiber sensor composite cable according to claim 7, wherein the reinforcing material is made of fiber reinforced plastic.   An optical fiber sensor composite cable in which an optical fiber grating type strain sensor is formed is incorporated in a network having an anisotropic elastic modulus, and an elastic modulus in a direction parallel to the optical fiber grating type strain sensor of the network. The optical fiber monitoring is characterized in that the elastic modulus in the direction perpendicular to the optical fiber grating type strain sensor of the network is higher than the elastic modulus of the optical fiber sensor composite cable. System net.   The optical fiber monitoring system net according to claim 12, wherein the optical fiber sensor composite cable is the optical fiber sensor composite cable according to any one of claims 1 to 5 and claims 7 to 11. Net for monitoring system.   14. An optical fiber monitoring system net, wherein a plurality of optical fiber monitoring system nets according to claim 12 or 13 are connected, and the optical fiber sensor composite cables are connected to each other.   The net for an optical fiber monitoring system according to any one of claims 12 to 14, wherein a method of knitting the net is spiral knitting.   15. The method according to any one of claims 12 to 14, wherein the net is knitted in plain weave, and the elastic modulus of the net is made anisotropic by changing the thickness of the warp and the weft, or the interval between the nets. An optical fiber monitoring system net described in 1. 13. The elastic modulus of the mesh in the direction orthogonal to the optical fiber grating strain sensor is increased by assembling a highly rigid elastic rod to the mesh in a direction perpendicular to the optical fiber grating strain sensor. The net | network for optical fiber monitoring systems as described in any one of -16.

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