JP2002162211A - Strain measuring device and its installing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the measurement of a highly accurate strain by very easily and highly accurately attaching an optical fiber for a sensor having a plug greeting part on a curved object to be measured. SOLUTION: The optical fiber for the sensor 11 having an FBG part 21 reflecting light from a light source is previously inserted in a cylindrical protection tube 10 having flexibility. A screw part 16 is provided on both the ends of the optical fiber for the sensor 11. The protection tube 10 is adhered and fixed on the surface of the object S to be measured, and the screw part 16 is screwed on a support part 13. The optical fiber for the sensor 11 is expanded and contracted by rotating the optical fiber for the sensor 11, in a state that it is tightened by prescribed tension, a gap is opened to support it along the object S to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain measuring device used for detecting distortion of various structures and displacement of the ground or the like by using an optical fiber, and a method of installing the same.

[0002]

2. Description of the Related Art Conventionally, in order to avoid dangers such as collapse of earth and sand and rocks, a guard has been patrolling to grasp the situation. However, such monitoring by patrols is not only very inefficient but also inaccurate, so strain gauges are used to detect crustal deformation and grasp the situation. Is also used, for example, for detecting distortion of a steel structure such as an iron bridge or a building such as a building, and these defects are grasped in advance.

[0003] However, the strain gauge can only detect a local strain, and is not suitable for a long structure or the like. For this reason, in recent years, a strain measurement device that measures a strain by using an optical fiber and detecting a change in the wavelength of reflected light corresponding to the expansion and contraction rate of the optical fiber has been developed.

[0004]

A strain measuring apparatus using an optical fiber of this type is measured by attaching an optical fiber, which is a sensor thereof, to a predetermined tension along an object to be measured. Although it is possible to measure the distortion of an object, if the object to be measured has a complicated shape curved into, for example, a U-shape or an S-shape, an optical fiber can be precisely formed along the object to be measured. However, there is a problem that high precision strain measurement cannot be performed.

[0005] In addition, the work of mounting the optical fiber in a state where the optical fiber is tensioned at a predetermined tension along the object to be measured is extremely complicated. However, there is a problem that a great deal of labor and time are required, and it is also required to easily adjust the tension state of the optical fiber after installation.

The present invention has been made in view of the above circumstances, and it is possible to attach a curved object to be measured very easily and accurately to measure distortion with high accuracy. It is an object of the present invention to provide a low-cost strain measuring apparatus and a method for installing the same, which can easily install even a large number of pieces to perform good measurement, and can easily adjust a tension state, and can be installed at a low cost. And

[0007]

According to a first aspect of the present invention, there is provided a distortion measuring apparatus which is provided with a light source and a light source provided with a gap along an object to be measured. An optical fiber for a sensor having a Bragg greeting portion that reflects light of a specific wavelength according to an expansion / contraction ratio, and expansion / contraction of the optical fiber for a sensor is detected from light reflected by the Bragg greeting portion of the optical fiber for the sensor. A strain measuring device having a measuring device and measuring a strain of the object to be measured based on a detection result of expansion and contraction of the optical fiber for sensor, wherein both ends of the optical fiber for sensor are fixed to the object to be measured. The intermediate portion including the Bragg greeting portion supported by the supported support portion is inserted through a flexible cylindrical protective tube fixed to the object to be measured. .

In other words, since the sensor optical fiber has a structure in which the intermediate portion including the Bragg greeting portion is covered by the protective tube, the Bragg greeting portion for detecting the distortion can be reliably protected. Further, since the flexible protective tube is fixed to the object to be measured, the protective tube can be arranged according to the shape of the object to be measured, whereby the sensor inserted through the protective tube can be provided. The optical fiber for use can be accurately arranged along the object to be measured. In other words, even in the case where the surface of the object to be measured is curved in a U-shape or S-shape, the optical fiber for the sensor is secured to the surface which is the measurement surface of the strain of the object to be measured. Since the sensor optical fiber is provided along the hole of the tube, the optical fiber for the sensor can be supported in a state of being provided along the measurement surface of the object to be measured, and a good measurement result can be obtained.

[0009] The distortion measuring device according to the second aspect is the first aspect.
In the strain measuring device described above, the protective tube is formed of resin.

That is, since the protective tube is formed of resin, when the protective tube is fixed along the object to be measured, it can be easily deformed and fixed according to its shape. In addition, damage due to sliding with the sensor optical fiber inserted through the protective tube can be suppressed.

According to a third aspect of the present invention, there is provided a strain measuring apparatus.
Alternatively, the distortion measuring device according to claim 2, wherein the protective tube is bonded and fixed to the object to be measured by an adhesive.

That is, since the protective tube is adhered to the object to be measured by the adhesive, the labor required for the fixing operation can be greatly reduced as compared with fixing means such as screw fixing.

According to a fourth aspect of the present invention, there is provided a strain measuring apparatus.
The strain measuring apparatus according to any one of claims 1 to 3, wherein the measuring instrument includes a strain measuring optical fiber in which a plurality of the sensor optical fibers supported by the plurality of objects to be measured are connected by a transmitting optical fiber. The measuring instrument detects the expansion and contraction of the sensor optical fiber of the strain measuring optical fiber, and measures the distortion of the object to be measured.

As described above, since a plurality of sensor optical fibers are connected by the transmission optical fiber to use the single strain measuring optical fiber, the reflected light of the Bragg greeting portion of each sensor optical fiber is used. By using different wavelengths, it is possible to measure the strain of a large number of objects using a single optical fiber for strain measurement, especially for measuring the strain of a large number of objects arranged over a long distance. It is advantageous.

According to a fifth aspect of the present invention, there is provided a distortion measuring apparatus.
5. The strain measuring device according to any one of to 4, wherein a screw portion having a male screw is provided at both ends of the sensor optical fiber, and the support portion fixed to the object to be measured has the screw portion. By having a female screw to be screwed, and screwing the screw portion to the support portion, the sensor optical fiber is disposed along the object to be measured, and the sensor optical fiber is screwed together. The screw and the female screw of the support part are oppositely screwed at both ends of the optical fiber for sensor.

That is, by screwing the threaded portions at both ends of the sensor optical fiber having the Bragg greeting portion to the supporting portion fixed to the object to be measured, the sensor optical fiber can be very easily placed along the object to be measured. In addition, since the external thread of the screw part and the internal thread of the support part are reverse-threaded at both ends, the optical fiber for the sensor can be rotated, The tension can be adjusted by expanding and contracting the optical fiber without twisting while being supported on the object to be measured very easily. As a result, even if there are many objects to be measured,
The sensor optical fiber can be easily and quickly supported on the object under predetermined tension.

According to a sixth aspect of the present invention, there is provided a method for installing a distortion measuring device, wherein a light source and a light having a specific wavelength corresponding to the expansion and contraction ratio of the light from the light source are arranged with a gap along the object to be measured. A sensor optical fiber having a Bragg greeting portion to be formed, and a measuring instrument for detecting expansion and contraction of the sensor optical fiber from light reflected by the Bragg greeting portion of the sensor optical fiber, wherein the sensor light A method for installing a strain measuring device that measures a strain of the object to be measured based on a detection result of expansion and contraction of a fiber, wherein the sensor optical fiber is inserted in advance through a flexible cylindrical protective tube. The protective tube is put on the outer periphery of the intermediate portion including the Bragg greeting portion, and the protective tube is fixed to the object to be measured, and the optical fiber for the sensor is Said end portion is supported by the object to be measured along the measurement object is characterized in that is arranged with a gap.

As described above, since the intermediate portion including the Bragg greeting portion of the optical fiber for the sensor is inserted in advance through the flexible tubular protective tube, the optical fiber for the sensor can be reliably protected. In particular, damage during transportation and installation can be reliably prevented. Moreover, since the flexible protective tube is fixed to the object to be measured and both ends of the sensor optical fiber are supported by the object to be measured, the surface of the object to be measured is curved in a U-shape or an S-shape. Even in such a case, the sensor optical fiber is arranged along the measurement surface of the measurement object by the inner peripheral surface of the protective tube fixed to the surface which is the measurement surface of the distortion of the measurement object. It can be supported in a state, and good measurement results can be obtained.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a strain measuring apparatus and a method for installing the same according to the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a distortion measuring device according to the present embodiment. This strain measuring device 1 has a plurality of strain measuring optical fibers 2, and these strain measuring optical fibers 2 are connected to an optical channel selector 3.
A light source 5 and a multi-wavelength meter (measuring device) 6 are connected to the optical channel selector 3 via a circulator 4.

The measurement light from the light source 5 is transmitted to the circulator 4
The optical fiber is sent to the optical channel selector 3 via the optical fiber selector 2, and is sent to the strain measuring optical fiber 2 selected by the optical channel selector 3 among the plurality of strain measuring optical fibers 2. The reflected light from the strain measuring optical fiber 2 to which the measuring light has been sent is sent from the optical channel selector 3 to the multiwavelength meter 6 via the circulator 4.

Next, the strain measuring optical fiber 2 will be described. As shown in FIG.
Has a plurality of sensor optical fibers 11, and the sensor optical fibers 11 are connected to each other and between the sensor optical fiber 11 and the optical channel selector 3 by a transmission optical fiber 12.

The optical fibers 11 for the sensors are attached to the object S to be measured, and measure the distortion of the object S to be measured. As shown in FIGS. 3 and 4, the object to be measured S has a pair of support portions 1 installed at intervals.
The support portion 13 supports the sensor optical fiber 11 of the strain measuring optical fiber 2 with a gap along the measured object S.

This sensor optical fiber 11 is, for example,
It is inserted through a flexible tubular protective tube 10 made of a resin such as polyimide or Teflon (registered trademark). The protective tube 10 is bonded and fixed to the surface of the measurement target S with an adhesive. The protective tube 10 may be formed of a flexible metal material.

As shown in FIG. 5, the optical fiber 11 for the sensor is connected to the transmission optical fiber 12 covered with the coating material 12a by being fused at both ends thereof. The fused portion 14 is provided with a screw portion 16 on the outer periphery of which a male screw 15 is formed. Then, this optical fiber for sensor 11
The threaded portion 16 on which the male thread 15 is formed is screwed and supported by the female thread 17 of the support portion 13 provided on the measured object S.

Here, the external thread 15 of the thread 16 at both ends of the optical fiber 11 for the sensor and the internal thread 1 of the support 13
Numerals 7 are reverse screws. That is, by rotating the optical fiber for sensor 11, the threaded portions 1 on both ends are
The amount of screwing of the 6 into the support portion 13 is changed so that the sensor optical fiber 11 can be expanded and contracted without twisting.

As shown in FIG. 6, the support portion 13 includes a base support portion 13a fixed to the object S to be measured, and a cover support portion 13b fixed on the base support portion 13a by screws 13c. The base support 1
In a state where the screw portion 16 is disposed on the female screw 17 of 3a, the cover support portion 13b is covered and fixed by the screw 13c to be integrated, so that the screw portion 16 is screwed to the female screw 17 of the support portion 13. It is to be supported in the state where it was.

The sensor optical fiber 11 has a fiber Bragg grating (hereinafter referred to as FBG)
Unit 21). The FBG part 21 reflects the light by Bragg diffraction and reflects the laser beam from the side to the core 11b formed at the center of the clad 11a to change the refractive index, as shown in FIG. A plurality of reflection plate portions 22 having different refractive indexes with respect to other portions are formed by a processing method such as a laser irradiation method.

That is, when light is incident on the FBG portion 21, a part of the light is reflected by each of the reflection plate portions 22 of the FBG portion 21, interferes with each other, strengthens each other, and is returned as a relatively large reflected light. It has become.

When the FBG portion 21 expands and contracts, the interval between the reflection plate portions 22 changes, and accordingly, the wavelength of the reflected light that interferes with each other and returns also changes. That is, by detecting a change in the wavelength of the reflected light from the FBG unit 21, the amount of expansion and contraction of the sensor optical fiber 11 is determined, and the sensor optical fiber 11
The distortion of the object S to be measured provided with is provided.

Each of the sensor optical fibers 11 provided on each of the strain measuring optical fibers 2 is provided with a different predetermined tension in advance, whereby the reflected light of each of the sensor optical fibers 11 is reduced. The wavelengths do not overlap, and the reflected light of each sensor optical fiber 11 in each strain measuring optical fiber 2 can be specified. That is, as shown in FIGS. 8 and 9, the sensor optical fiber 1 is within the measurable wavelength range Ws (see FIG. 8), which is the range of the wavelength of the measurable light.
The reflection wavelength ranges Wb (see FIG. 9), which are the wavelength ranges including the fluctuation of the reflected light from 1 due to the distortion of the measurement object S, are prevented from overlapping each other.

The sensor optical fiber 11 having the FBG portion 21 having the above structure is covered on its outer peripheral side with a coating 23 made of an ultraviolet curable resin. Further, a tubular reinforcing member 24 made of a resin such as plastic is adhered and fixed to the sensor optical fiber 11 on the outer peripheral side of the coating 23 in a portion where the FBG portion 21 is formed. The hardness of the part is increased, and the elastic modulus is relatively lower than that of the other parts.

Next, a case where the sensor optical fiber 11 of the strain measuring optical fiber 2 is supported by the workpiece S will be described. First, the sensor optical fiber 11 (FIG. 1)
0) is passed through the protective tube 10 in advance (see FIG. 11).

Next, a screw portion 16 is attached to the fusion spliced portion 14 of the sensor optical fiber 11 (see FIG. 12). Note that the screw portion 16 is provided with a stopper 25 on the side of the protective tube 10.
As a result, the opening end of the protection tube 10 is closed to prevent entry of foreign matter and the like into the protection tube 10 and the sensor optical fiber 11 is reliably protected.

On the other hand, a base support 13a constituting the support 13 is fixed to the object S to be measured (see FIG. 13). The screw portions 16 at both ends of the sensor optical fiber 11 are disposed on the base support portion 13a fixed to the workpiece S (see FIG. 14). In this state, the cover support portion 13b is covered and fixed by the screws 13c. Then, the screw portion 16 is screwed into the female screw 17 of the support portion 13 to support the sensor optical fiber 11 along the workpiece S (see FIG. 15). In addition, the optical fiber for sensor 11
Is secured to the surface of the measuring object S with an adhesive.

When the adhesive for fixing the protective tube 10 to the object S is hardened, the sensor optical fiber 11 is rotated to extend the sensor optical fiber 11 with a predetermined tension (see FIG. 16). .

Here, the external thread 15 of the threaded portion 16 at both ends of the optical fiber 11 for the sensor and the internal thread 1 of the support portion 13
7, since the sensor optical fibers 11 are oppositely screwed, the amount of screwing of the screw portions 16 at both ends into the support portion 13 is changed by rotating the sensor optical fiber 11, thereby twisting the sensor optical fiber 11. It is stretched without.

By performing the above operation, the sensor optical fiber 11 can be easily supported along the measured object S with a gap therebetween, so that the strain can be measured. After installing the sensor optical fiber 11 on the object S as described above, the upper part of the object S including the sensor optical fiber 11 may be covered with a waterproof cover 26, if necessary.
(See FIG. 17).

According to the strain measuring apparatus 1 having the above structure, the measuring light emitted from the light source 5 is sent to the optical channel selector 3 via the circulator 4 and is used for measuring the strain selected by the optical channel selector 3. It is sent to the optical fiber 2. In the strain measuring optical fiber 2 into which the measuring light is sent, the light is reflected by the FBG unit 21 of the sensor optical fiber 11 supported by the measured object S, and is returned as reflected light.

The reflected light reflected by the FBG section 21 of the sensor optical fiber 11 is redirected by the circulator 4 and sent to the multi-wavelength meter 6, where the light is reflected by the multi-wavelength meter 6. The reflected light from the optical fiber 11 is detected, and the state is displayed.

That is, from the fluctuation of the wavelength of the reflected light from each sensor optical fiber 11 detected by the multi-wavelength meter 6, the distortion of the object S on which each sensor optical fiber 11 is supported is detected. Can be. In the optical channel selector 3, the strain measuring optical fibers 2 are sequentially selected and connected, whereby the strain of the object S in the plurality of strain measuring optical fibers 2 is constantly monitored.

In the optical fiber 11 for the sensor,
The FBG portion 21 has a relatively low elastic modulus compared to other portions and is suppressed from expanding and contracting by the reinforcing member 24 provided on the outer peripheral side thereof. The amount of expansion and contraction in the portion 21 is reduced, and the range of fluctuation of the reflected light from the FBG portion 21 is reduced. Therefore, in the measurable wavelength range Ws which is the range of the wavelength of the measurable light, more The reflection wavelength range Wb can be provided, whereby the installation amount of the sensor optical fiber 11 that can be installed on one strain measurement optical fiber 2 can be greatly increased.

Accordingly, even when measuring a large amount of distortion of the object S to be measured, a large amount of the optical fiber 2 for strain measurement can be used.
It is not necessary to prepare the optical fiber 2 and the cost can be greatly reduced, and the work of disposing the optical fiber 2 for strain measurement can be facilitated. Also, since many optical fibers 11 for sensors can be provided in one optical fiber 2 for strain measurement, it is particularly advantageous for measuring the distortion of a large number of objects S to be measured provided over a long distance.

As described above, according to the above-described strain measuring apparatus 1, since the intermediate portion including the FBG portion 21 of the sensor optical fiber 11 is covered with the protective tube 10, the FBG portion 21 for detecting the strain is provided. Can be reliably protected by the protective tube 10. Further, since the flexible protective tube 10 is fixed to the measured object S, the protective tube 10 can be arranged in the shape of the measured object S. The optical fiber 11 for a sensor inserted through the object S can be accurately arranged along the measured object S.

That is, as shown in FIG.
Even when the surface is curved, the sensor optical fiber 11 is stretched along the inside of the hole of the protective tube 10 adhered and fixed to the surface of the object S to be measured for measuring the distortion. Since the sensor optical fiber 11 is supported in the state, the sensor optical fiber 11 can be supported in a state where it is disposed along the measurement surface of the measurement target S.

Further, by forming the protective tube 10 from a resin, when the protective tube 10 is fixed along the workpiece S, it can be easily deformed and fixed according to its shape. Moreover, the protective tube 1
Damage due to sliding with the sensor optical fiber 11 inserted into the sensor optical fiber 11 can also be suppressed.

Further, the protective tube 10 is connected to the object S to be measured.
Since the structure is bonded by an adhesive, the labor required for the fixing operation can be significantly reduced as compared with fixing means such as screw fixing.

Further, since a plurality of optical fibers for sensor 11 are connected by a transmission optical fiber 12 to use a single optical fiber 2 for strain measurement, the reflection of each of the optical fibers 11 for sensor in the FBG section 21 is performed. By making the wavelengths of light different, the strain of many objects S can be measured by one optical fiber 2 for strain measurement, and in particular, many objects S arranged over a long distance can be measured. This is advantageous for the measurement of the distortion.

Further, by screwing the screw portions 16 at both ends of the sensor optical fiber 11 having the FBG portion 21 to the support portion 13 fixed to the object S, the sensor optical fiber 11 can be measured very easily. Since a gap can be provided along the object S and the external thread 15 of the screw portion 16 and the internal thread 17 of the support portion 13 are reverse-threaded at both ends, light for the sensor can be obtained. By rotating the fiber 11, the optical fiber 11 for the sensor can be easily extended and contracted without being twisted while being supported by the object S, and the tension thereof can be adjusted.

Thus, even if there are a large number of objects S to be measured, the sensor optical fiber 1 can be easily and quickly shortened.
1 can be supported on the measured object at a predetermined tension.

According to the installation method of the strain measuring device 1, the intermediate portion including the FBG portion 21 of the optical fiber for sensor 11 is inserted into the flexible tubular protective tube 10 in advance. The optical fiber for sensor 11 can be reliably protected by the protective tube 10,
In particular, damage during transportation and installation can be reliably prevented.

In addition, the flexible protective tube 10
Is fixed to the object S to be measured, and both ends of the sensor optical fiber 11 are supported by the object S. Therefore, even when the surface of the object S is curved, the optical fiber 11 is fixed by the inner peripheral surface of the protective tube 10 which is fixed to the surface of the measurement object S, which is the strain measurement surface.
Can be supported in a state of being arranged along the measurement surface, and a good measurement result can be obtained.

The above-described strain measuring apparatus 1 can be applied to any object for measuring strain. For example, the strain measuring device 1 can be used to measure not only steel structures such as iron bridges and buildings such as buildings, but also strains in the ground. It can also be used for monitoring crustal deformation such as land subsidence, or for measuring distortion of the main wing or fuselage of an airplane.

[0053]

As described above, the following effects can be obtained by the distortion measuring device and the method of installing the same according to the present invention. According to the strain measuring device of the first aspect, since the intermediate portion including the Bragg greeting portion of the optical fiber for the sensor has a structure covered with the protective tube,
The Bragg greeting portion for detecting distortion can be reliably protected by the protective tube. Further, since the flexible protective tube is fixed to the object to be measured, the protective tube can be arranged according to the shape of the object to be measured, whereby the sensor inserted through the protective tube can be provided. The optical fiber for use can be accurately arranged along the object to be measured. In other words, even in the case where the surface of the object to be measured is curved in a U-shape or S-shape, the optical fiber for the sensor is secured to the surface which is the measurement surface of the strain of the object to be measured. Since the sensor optical fiber is provided along the hole of the tube, the optical fiber for the sensor can be supported in a state of being provided along the measurement surface of the object to be measured, and a good measurement result can be obtained.

According to the second aspect of the present invention, since the protective tube is formed of a resin, when the protective tube is fixed along an object to be measured, it is easily deformed according to its shape. Can be fixed. In addition, damage due to sliding with the sensor optical fiber inserted through the protective tube can be suppressed.

According to the third aspect of the present invention, since the protective tube is adhered to the object to be measured by the adhesive, the labor required for the fixing operation is reduced as compared with fixing means such as screw fixing. It can be greatly reduced.

According to the strain measuring device of the present invention, since a plurality of optical fibers for sensors are connected by a transmission optical fiber to use a single optical fiber for measuring strain, each optical fiber for sensors is used. By making the wavelength of the reflected light different in the Bragg greeting section of, it is possible to measure the distortion of many objects to be measured with one optical fiber for distortion measurement, and in particular, many optical fibers are arranged over a long distance. This is advantageous for measuring the distortion of the measured object.

According to the strain measuring apparatus of the present invention, the screw portions at both ends of the optical fiber for the sensor having the Bragg greeting portion are screwed into the support portion fixed to the object to be measured, so that the sensor optical device is very easily used. The optical fiber can be supported with a gap along the object to be measured,
In addition, since the external thread of the screw portion and the internal thread of the support portion are reversely threaded at both ends, the sensor optical fiber can be extremely easily attached to the object by rotating the sensor optical fiber. It can be expanded and contracted without being twisted in the supported state, and its tension can be adjusted. Thereby, even if there are many objects to be measured, the sensor optical fiber can be supported on the object with a predetermined tension easily and in a short time.

According to the installation method of the strain measuring device according to the sixth aspect, the intermediate portion including the Bragg greeting portion of the optical fiber for the sensor is inserted in advance through the flexible tubular protective tube. This sensor optical fiber can be reliably protected by the protective tube, and in particular, damage during transportation and installation can be reliably prevented. Moreover, since the flexible protective tube is fixed to the object to be measured and both ends of the optical fiber for the sensor are supported by the object to be measured, even if the surface of the object to be measured is curved. The optical fiber for the sensor can be supported in a state where it is arranged along the measurement surface of the measurement object by the inner peripheral surface of the protective tube fixed to the surface that is the measurement surface of the distortion of the measurement object, Good measurement results can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a strain measurement device illustrating a strain measurement device and an installation method thereof according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a strain measuring optical fiber included in the strain measuring device according to the embodiment of the present invention.

FIG. 3 is a plan view illustrating a state in which the optical fiber for sensor of the strain measuring optical fiber of the strain measuring device according to the embodiment of the present invention is attached to an object to be measured.

FIG. 4 is a side sectional view illustrating a state where the optical fiber for sensor of the strain measuring optical fiber of the strain measuring device according to the embodiment of the present invention is attached to the object to be measured.

FIG. 5 is a perspective view illustrating a structure of a sensor optical fiber of the strain measuring device according to the embodiment of the present invention.

FIG. 6 is a perspective view illustrating a structure of a supporting portion that supports a sensor optical fiber of the strain measuring device according to the embodiment of the present invention.

FIG. 7 is a schematic perspective view illustrating the structure of an FBG section provided in the sensor optical fiber of the strain measuring device according to the embodiment of the present invention.

FIG. 8 is a graph illustrating the distribution of reflected light in a strain measurement device using an optical fiber.

FIG. 9 is a graph illustrating the distribution of reflected light in a strain measurement device using an optical fiber.

FIG. 10 is a side view of a sensor optical fiber illustrating a method for installing the strain measuring device according to the embodiment of the present invention.

FIG. 11 is a side view of a sensor optical fiber illustrating a method for installing a strain measurement device according to an embodiment of the present invention.

FIG. 12 is a side view of a sensor optical fiber illustrating a method for installing a strain measuring device according to an embodiment of the present invention.

FIG. 13 is a side sectional view of an object to be measured for explaining a method of installing the strain measuring device according to the embodiment of the present invention.

FIG. 14 is a side cross-sectional view of an object to be measured on which an optical fiber for a sensor is supported, illustrating a method for installing the strain measuring device according to the embodiment of the present invention.

FIG. 15 is a side cross-sectional view of an object on which an optical fiber for a sensor is supported, illustrating a method for installing the strain measuring device according to the embodiment of the present invention.

FIG. 16 is a side sectional view of an object to be measured on which an optical fiber for a sensor is supported, illustrating a method for installing the strain measuring device according to the embodiment of the present invention.

FIG. 17 is a side sectional view of an object on which a sensor optical fiber is supported, illustrating a method for installing the strain measuring device according to the embodiment of the present invention.

FIG. 18 is a side sectional view of an object to be measured on which an optical fiber for a sensor is supported, illustrating a method for installing the strain measuring device according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Strain measuring apparatus 2 Strain measuring optical fiber 5 Light source 6 Multiwavelength meter (measuring instrument) 10 Protective tube 11 Sensor optical fiber 12 Transmission optical fiber 13 Supporting part 15 Male screw 16 Screw part 17 Female thread 21 FBG part (Bragg) Greeting part) S Measured object

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiromasa Ito 12 Nishiki-cho, Naka-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Heavy Industries, Ltd. Yokohama Works F-term (reference) 2F065 AA65 BB22 CC23 DD16 FF42 LL02 5G369 AA16 BA01 BB03 DC02 EA01 EA04

Claims (6)

[Claims] An optical fiber for a sensor, comprising: a light source; and a Bragg greeting portion disposed along the object to be measured with a gap therebetween and reflecting light of a specific wavelength according to the expansion and contraction rate of light from the light source. A measuring device for detecting expansion and contraction of the optical fiber for sensor from light reflected by the Bragg greeting portion of the optical fiber for sensor, and detecting the expansion and contraction of the optical fiber for sensor based on a detection result of expansion and contraction of the optical fiber for sensor. A strain measuring device for measuring a strain of a measurement object, wherein the sensor optical fiber has both ends supported by a support unit fixed to the measurement object, and an intermediate unit including the Bragg greeting unit includes the sensor optical fiber. A distortion measuring device, which is inserted through a flexible tubular protective tube fixed to an object to be measured. 2. The strain measuring device according to claim 1, wherein the protective tube is formed of a resin. 3. The strain measuring device according to claim 1, wherein the protective tube is fixedly adhered to the object to be measured with an adhesive. 4. A strain measuring optical fiber in which a plurality of sensor optical fibers respectively supported by a plurality of objects to be measured are connected by a transmission optical fiber is connected to the measuring instrument, and the strain is measured by the measuring instrument. The strain measuring apparatus according to any one of claims 1 to 3, wherein the expansion and contraction of the sensor optical fiber of the measurement optical fiber is detected, and the distortion of the object is measured. 5. The sensor optical fiber is provided with a threaded portion having male threads at both ends thereof, and the supporting portion fixed to the object to be measured is a female thread into which the threaded portion is screwed. By screwing the screw portion to the support portion, the sensor optical fiber is disposed along the object to be measured, and the male screw and the support portion of the screw portion screwed to each other are provided. The strain measuring device according to any one of claims 1 to 4, wherein the female threads are opposite threads at both ends of the sensor optical fiber. 6. An optical fiber for a sensor, comprising: a light source; and a Bragg greeting portion disposed at a gap along the object to be measured and reflecting light of a specific wavelength according to the expansion and contraction rate of light from the light source. A measuring device for detecting expansion and contraction of the optical fiber for sensor from light reflected by the Bragg greeting portion of the optical fiber for sensor, and detecting the expansion and contraction of the optical fiber for sensor based on a detection result of expansion and contraction of the optical fiber for sensor. A method of installing a distortion measuring device for measuring distortion of an object, wherein the sensor optical fiber is inserted in advance through a flexible cylindrical protective tube, and an outer periphery of an intermediate portion including the Bragg greeting portion is provided. And the protective tube is fixed to the object to be measured.
A method for installing a strain measuring apparatus, wherein both ends of the optical fiber for a sensor are supported by the object to be measured and are disposed with a gap along the object to be measured.