JP2009128009A - Optical fiber sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber sensor which is capable of eliminating errors in temperature compensation and detecting distortion caused only by the deformation and thickness loss of a measurement object, which protects an optical fiber from damage caused by external stress so that the measurement of distortion is not affected, and capable of easily leading out the optical fiber without causing disconnection. <P>SOLUTION: The optical fiber sensor 1A(1) comprises a first optical fiber 3 for the detection of distortion and a second optical fiber 4 for temperature compensation which are provided on the same substrate 2. The first optical fiber is provided to be fixed on the substrate, and the second optical fiber is provided in a cavity 5A formed on the substrate, in close proximity to the first optical fiber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical fiber sensor that can accurately detect the amount of distortion caused by deformation of a measurement object.

  It is very important to detect the distortion caused by the deformation of the structure when judging the stability of the structure. For example, by detecting the distortion of pipes installed in power plants, plants, etc., it is possible to identify the location of local expansion and the degree of expansion associated with pipe thinning and prevent serious accidents from occurring. can do. And important information can be obtained not only for piping but also for various other structures by detecting distortion.

  Conventionally, various sensors using optical fibers have been proposed as sensors for detecting such distortion of structures such as piping. This is because the continuous distribution of strain in the longitudinal direction of the optical fiber can be observed with high accuracy, and the frequency shift amount of Brillouin shift scattered light, which is one of the nonlinear phenomena, depends on the strain of the optical fiber. Is used. An electrical sensor requires a power source, is easily affected by noise such as induced current, and its construction requires cost and labor, whereas such an optical fiber sensor can solve these problems. Has attracted attention.

If the optical fiber sensor is laid on the structure to be measured, it will also be distorted as the measurement object is distorted. Therefore, according to the principle described above, the distortion of the measurement object can be easily detected. It is possible.
However, the distortion of the optical fiber is caused not only by the deformation of the measurement object but also by the temperature change of the optical fiber. For example, when the measurement object is thermally expanded, or when the measurement object is provided in a place where the temperature change is large, the amount of strain caused by the deformation of the measurement object and the measurement object or A combination of the distortion amount due to the heat transmitted from the heat source to the optical fiber is detected. That is, the amount of distortion caused by heat becomes noise, and the amount of distortion cannot be accurately detected.

  As a solution to this problem, there has been proposed an optical fiber sensor in which an optical fiber for detecting distortion and an optical fiber for temperature compensation that is not affected by the distortion caused by deformation of the measurement object are provided (for example, , See Patent Document 1).

  In a distributed sensor using a first optical fiber for strain detection and an optical fiber for temperature compensation, it is very important to perform strain detection and temperature compensation for each measurement point. In other words, the optical fiber sensor described in Patent Document 1 and the like can perform more accurate measurement by subtracting the amount of distortion caused by the temperature change detected by the second optical fiber for temperature compensation from the amount of distortion detected. It is intended to detect the distortion amount of the object.

  However, in such an optical fiber sensor, it is highly possible that the exterior covering resin repeatedly expands and contracts as the ambient temperature changes, and the position of the temperature compensating second optical fiber shifts accordingly. As long as the first optical fiber for strain detection is fixed on the base material and the base material is also fixed to the object to be measured, the attached position will not be shifted with respect to the temperature change. If the laying position of the two optical fibers is shifted, accurate temperature compensation cannot be performed at each measurement point, and there is a high possibility that the temperature compensation error increases each time a repeated temperature cycle is applied.

  In addition, these optical fiber sensors do not consider that the temperature compensating optical fiber is used in an extremely high temperature environment (for example, about several hundred degrees Celsius). However, there was a problem that there was a limit.

Further, in the optical fiber sensor described in Patent Document 1, the second optical fiber for temperature compensation is covered with a metal tube. However, when the fiber is led out, only the metal pipe is cut and the inner fiber is removed. When taking out, there is a possibility of cutting the entire fiber by mistake. If all of the lead-out surplus length portion is cut, the target laying length is shortened, and the extra cost of re-laying the sensor is required. Even if only the pipe can be cut, there is a high possibility that the fiber is hooked and disconnected when the pipe is pulled out.
JP 2001-228378 A

  The present invention has been devised in view of such a conventional situation, eliminates temperature compensation errors, and stably detects only distortion caused by deformation, thinning, etc. of a measurement object in a distributed manner. An optical fiber sensor capable of protecting the optical fiber from external stresses, preventing the strain measurement from being disturbed, and allowing the fiber to be easily opened without disconnecting the optical fiber. The purpose is to provide.

The optical fiber sensor according to claim 1 of the present invention is an optical fiber sensor in which a first optical fiber for strain detection and a second optical fiber for temperature compensation are provided on the same base material, The first optical fiber is fixedly disposed on the base material, and the second optical fiber is disposed in the space formed on the base material in the immediate vicinity of the first optical fiber. It is characterized by being.
An optical fiber sensor according to a second aspect of the present invention is the optical fiber sensor according to the first aspect, wherein a plurality of the first optical fibers are disposed on the substrate so as to sandwich the second optical fiber, and the first light A lid is disposed so as to straddle the top of each first optical fiber when viewed from the axial direction of the fiber, and the gap is formed by the base material, the first optical fiber, and the lid. It is characterized by being.
An optical fiber sensor according to a third aspect of the present invention is the optical fiber sensor according to the first aspect, wherein the gap is configured such that a part of the base material covers an outer periphery of the second optical fiber along the second optical fiber. It is formed by winding around.
An optical fiber sensor according to a fourth aspect of the present invention is the optical fiber sensor according to the third aspect, wherein one surface of the base material is in contact with a part of the end of the wound base material, or there is a gap between them. The diameter of the second optical fiber is smaller than that of the second optical fiber.
The optical fiber sensor according to claim 5 of the present invention is characterized in that, in claim 1, the second optical fiber is formed by a pipe-shaped forming material having a gap.
The optical fiber sensor according to a sixth aspect of the present invention is the optical fiber sensor according to the fifth aspect, wherein a joint of the foaming material is in contact with the base material.

  In the optical fiber sensor of the present invention, a first optical fiber for strain detection and a second optical fiber for temperature compensation are provided on the same base material, and the second optical fiber for temperature compensation is the strain detection. In the immediate vicinity of the first optical fiber for use, it is arranged inside a gap formed on the substrate.

  By adopting such a configuration, the second optical fiber for temperature compensation is disposed on the base material, but is not fixed to the base material. Therefore, the second optical fiber for temperature compensation is It is not affected by the distortion of the measurement object. That is, it is possible to detect only distortion due to expansion and contraction accompanying the temperature change of the temperature compensating second optical fiber itself without detecting distortion of the measurement object. This eliminates the error in temperature compensation, and as a result, by correcting the detection value of the first optical fiber for strain detection with the detection value of the second optical fiber for temperature compensation, pure deformation of the measurement object, Only distortion caused by thinning or the like can be stably detected in a distributed manner. Moreover, the optical fiber sensor of this invention can protect an optical fiber from the damage | wound by external stress by arrange | positioning an optical fiber inside a space | gap part, and does not interfere with distortion measurement. In addition, since the optical fiber sensor of the present invention can be easily cut with a general-purpose tool, the optical fiber sensor can be easily opened without breaking the optical fiber.

  Hereinafter, an embodiment of a semiconductor device according to the present invention will be described with reference to the drawings.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below at all. In the following, “strain” means “strain in the longitudinal direction of the optical fiber” unless otherwise specified.

<First embodiment>
1A and 1B show an example of an optical fiber sensor of the present invention, in which FIG. 1A is a perspective view when cut along a plane perpendicular to the longitudinal direction of the optical fiber, and FIG. 1B is a cross-sectional view.
An optical fiber sensor 1 of the present invention is an optical fiber sensor in which a strain detection first optical fiber 3 and a temperature compensation second optical fiber 4 are provided on the same base material 2. The optical fiber 3 is fixedly disposed on the base material 2, and the second optical fiber 4 is disposed in the space 5 formed on the base material 2 in the immediate vicinity of the first optical fiber 3. It is characterized by.

  By adopting such a configuration, the second optical fiber 4 is disposed on the base material 2 but is not fixed to the base material 2. Unaffected by distortion. That is, it is possible to detect only the strain due to expansion and contraction accompanying the temperature change of the second optical fiber 4 without detecting the strain of the measurement object. As a result, there is no temperature compensation error. As a result, the detection value of the first optical fiber 3 is corrected with the detection value of the second optical fiber 4, resulting in pure deformation or thinning of the measurement object. Only distortion can be detected in a distributed manner.

  In particular, in the optical fiber sensor 1 </ b> A (1) of the present embodiment, a plurality of first optical fibers 3 are disposed on the base material 2 so as to sandwich the second optical fiber 4, and the axial center of the first optical fiber 3. The lid 6 is disposed so as to straddle the top of each first optical fiber 3 when viewed from the direction, and the gap 5A is formed by the base material 2, the first optical fiber 3, and the lid 6. Yes.

  In this embodiment, the 2nd optical fiber 4 is arrange | positioned between the some 1st optical fibers distribute | arranged on the base material 2, and the top part of each 1st optical fiber 3 is straddled with thin cover bodies 6, such as a film. Thus, the structure was such that the fixing agent 8 was further applied thereon. By covering the plurality of first fibers, a gap 5A is formed in the base material 2, the first optical fiber 3, and the cover 6 over the sensor longitudinal direction. The second fiber is disposed in the gap 5A.

  As described above, the second optical fiber 4 is arranged in the gap portion 5A existing in the longitudinal direction of the sensor, and is protected by the lid body 6, so that the second optical fiber 4 is damaged by the external adaptation force. It can be protected so that it does not interfere with strain measurement.

  Further, in the optical fiber sensor 1A, the base material 2 and the first optical fiber 3 can be separated by bending the base material 2 in the direction opposite to the direction in which the fibers are arranged, and at the same time, the optical fiber sensor 1A is arranged inside the gap 5A. The second optical fiber 4 is also led out. The lid 6 can be easily torn by cutting with a general-purpose tool such as a scissors, razor, nipper or the like, and the fiber can be easily led out. Since the second optical fiber 4 has an extra length equal to or greater than the elongation strain due to the expansion of the pipe, no elongation strain is applied.

In the present invention, it is preferable to use a flexible material as the substrate 2, and examples of such a preferable material include various metals such as stainless steel, various resins having flexibility and heat resistance, and the like. Can do.
Moreover, it is preferable that the base material 2 is a sheet-like shape.

The first optical fiber 3 is disposed on the base material 2 by being fixed by a fixing agent 7. Therefore, the first optical fiber 3 is integrally deformed with the distortion of the measurement object.
As the fixing agent 7, it is preferable to use a resin foam such as a thermosetting resin. As such a resin foam, a conventionally known one may be used and is not particularly limited.

The lid 6 is preferably a heat resistant film.
The heat-resistant film is not particularly limited as long as it has a heat-resistant temperature equal to or higher than the highest temperature achieved in the intended laying environment. For example, polyethersulfone or polyarylate (long-term heat-resistant temperature 150 ° C.), A film made of a material such as polyetherimide (long-term heat resistant temperature 170 ° C.), polyamideimide, polyetheretherketone or wholly aromatic polyester (long-term heat resistant temperature 230 to 240 ° C.) is used.

  In addition, it is difficult to tear a heat-resistant film by hand, but it can be easily cut by a general-purpose tool such as a scissors, a razor, and a nipper. Therefore, the optical fiber sensor 1A of the present invention using such a heat-resistant film is used. Can be easily extracted without disconnecting the second optical fiber 4 for temperature compensation.

  In addition, since the heat resistant film also functions as a protective material for the first optical fiber 3 and the second optical fiber 4, even if the sensor surface is touched after the sensor is laid, the fiber is not damaged and the loss increases. It is possible to eliminate the factors that affect the strain measurement. In addition, it is not necessary to provide a separate sensor protection member after laying the sensor, and material costs and laying time can be reduced.

  And as above-mentioned, the 2nd optical fiber 4 is the space | gap part 5 formed on the base material 2 (in this embodiment, the space | gap part 5 is the base material 2, the 1st optical fiber 3, and the said cover body 6). It is formed by.) The second optical fiber 4 is not fixed to the surface of the base material 2. In other words, the second optical fiber 4 can be expanded and contracted along the longitudinal direction inside the gap portion 5 in accordance with a temperature change (hereinafter sometimes abbreviated as “loose”).

  Therefore, the second optical fiber 4 is not fixed to the base material 2 along the longitudinal direction while being disposed on the base material 2. That is, the second optical fiber 4 is not affected by the distortion of the measurement object, does not detect the distortion of the measurement object, and only detects the distortion caused by the expansion and contraction accompanying the temperature change of the second optical fiber 4 itself. It can be detected.

  Thus, by arranging the second optical fiber 4 inside the gap portion 5A, the second optical fiber 4 can be brought into a state in which distortion due to surrounding stress is not applied at all. As a result, the second optical fiber 4 can detect only distortion due to temperature change, that is, distortion caused by Brillouin frequency shift and linear expansion of the optical fiber itself. Since the amount of strain changes linearly with respect to temperature change, the temperature can be accurately obtained from the measured amount of strain.

In the optical fiber sensor 1 </ b> A, the fixing agent 8 is applied so as to cover the first optical fiber 3 and the lid body 6.
As the fixing agent 8, it is preferable to use a resin foam such as a thermosetting resin. As such a resin foam, a conventionally known one may be used and is not particularly limited.

  The optical fiber sensor 1A (1) of the present invention is used by being laid on a measurement object with the base material 2 as a laying surface. When the measurement object is deformed to generate distortion, the optical fiber sensor 1 also generates distortion in an integrated manner, so that the distortion at this time is detected. For the detection of distortion, for example, an optical pulse tester (so-called BOTDR) for observation of Brillouin scattered light is connected to an optical fiber, and the optical fiber is tested using the optical pulse tester to observe the Brillouin scattered light. Do that. Specifically, when test light is incident on an optical fiber, if distortion occurs in the longitudinal direction of the optical fiber, Brillouin scattered light, which is one of the backscattered light, is generated, and the wavelength of the emitted Brillouin scattered light. Is deviated from the wavelength of the incident test light, so that the amount of distortion of the light-emitting fiber can be detected from this frequency shift amount. In addition, by detecting the time (return time) until the Brillouin scattered light is received and observed by the optical pulse tester after the test light is incident, an outline of the position where the optical fiber is distorted is grasped. Can do.

However, when a change in temperature occurs in the optical fiber, the amount of strain actually detected by the optical fiber is the sum of the amount of distortion of the measurement object and the amount of distortion of the optical fiber itself caused by the change in temperature of the optical fiber. It becomes a thing.
In the optical fiber sensor 1 of the present invention, the strain amount of the measurement object can be measured with high accuracy by subtracting the strain amount detected by the second optical fiber 4 from the strain amount detected by the first optical fiber 3. it can. That is, as described above, the second optical fiber 4 is loose inside the gap 5. As a result, the distortion of the measurement object itself does not occur, and only the amount of distortion due to expansion and contraction accompanying the temperature change of the second optical fiber 4 itself is detected. Therefore, the strain amount of the second optical fiber 4 is determined from the strain amount detection value of the first optical fiber 3 that detects the sum of the strain amount associated with the strain of the measurement object and the strain amount due to its own expansion and contraction due to its own temperature change. By subtracting the detection value, the amount of distortion of the measurement object can be accurately measured.

  Specifically, the correction of the influence of temperature is performed as follows. That is, from the optical test data of the second optical fiber 4, the shift amount due to the temperature change of the frequency with respect to the incident light of the Brillouin scattered light is obtained, and the shift amount is detected by the Brillouin scattered light detected by the optical test of the first optical fiber 3. The frequency shift amount of the Brillouin scattered light caused by the distortion of the measurement object of the first optical fiber 3 can be obtained by subtracting from the frequency shift amount.

  Or you may employ | adopt the method of correct | amending the detection data of a Brillouin scattered light from the data which received and detected the backscattered light of the Raman scattered light of the incident light to the 2nd optical fiber 4 with the optical pulse tester. Since the intensity of the backscattered light of the Raman scattered light detected by the incidence of light on the second optical fiber 4 changes depending on the temperature of the second optical fiber 4, the intensity of the backscattered light of the detected Raman scattered light Differ depending on the partial temperature difference of the second optical fiber 4. Then, the intensity may be obtained from the intensity ratio of the detected waveform (OTDR [Optical Time Domain Reflectometer] waveform of Stokes light and anti-Stokes light), and the temperature may be obtained from a predetermined theoretical formula.

Thus, by detecting the strain amount and strain position of the optical fiber, the strain amount and strain position of the measurement object can be specified.
Moreover, since the optical fiber sensor 1 of the present invention has a simple structure, the optical fiber sensor 1 can be easily manufactured at a low cost, and only needs to be installed on the measurement object, and the distortion amount can be easily measured.

  Moreover, since the optical fiber sensor 1 of the present invention has a simple structure, a plurality of first optical fibers 3 and / or second optical fibers 4 may be disposed on the same base material 2 to form the optical fiber sensor 1. good. By providing a plurality of distortion detection points in this way, the accuracy of distortion detection of the measurement object can be further improved.

Hereinafter, a method for manufacturing the optical fiber sensor 1A of the present embodiment will be described.
FIG. 2 is a process diagram showing an example of a manufacturing process of the optical fiber sensor 1A. In FIG. 2, when the same components as those described in FIG. 1 are indicated, the reference numerals used in FIG. 1 are used as they are, and detailed descriptions thereof are omitted.

  A plurality of (here, two) first optical fibers 3 wound in a roll shape are simultaneously introduced into the fixing agent applicator 30. In the fixing agent applicator 30, a solution containing a monomer of a thermosetting resin (that is, the fixing agent 7) is simultaneously applied to these, and the surface of the first optical fiber 3 is collectively covered with the solution.

  Subsequently, the first optical fiber 3 coated with the solution is simultaneously introduced into the heating furnace 31 while being attached on the base material 2. The inside of the heating furnace 31 is set to a temperature higher than the temperature necessary for the monomer to cure, and the first optical fiber 3 is fixed on the substrate 2 from the outlet of the heating furnace 31. What is done is pulled out.

Then, the 2nd optical fiber 4 wound by roll shape is distribute | arranged between the 1st optical fibers 3 [refer FIG.2 (b)].
Then, the lid body 6 is disposed so as to straddle the top of each first optical fiber 3 [see FIG. 2 (c)], and within the fixing agent applicator 32, on the lid body and the first optical fiber 3. A solution containing a monomer of a thermosetting resin (fixing agent 8) is applied, and the base material 2, the lid 6 and the first optical fiber 3 are covered with the solution [see FIG. 4 (a)].

  Subsequently, the base material 2, the first optical fiber 3, the second optical fiber 4, and the lid body 6 covered with the solution are simultaneously introduced into the heating furnace 33. The inside of the heating furnace 33 is set to a temperature equal to or higher than the temperature required for the monomer to cure. From the outlet of the heating furnace 33, the first optical fiber 3 and The one provided with the second optical fiber 4 is drawn out. This completes the curing of the thermosetting resin, which is the fixing agent 8, until the subsequent take-off, so that the optical fiber sensor 1A of this embodiment is obtained, and is finally wound up in a roll shape [see FIG. 2 (c)]. ].

<Second embodiment>
Next, a second embodiment of the present invention will be described.
3A and 3B show a second embodiment of the optical fiber sensor of the present invention, in which FIG. 3A is a perspective view when cut along a plane perpendicular to the longitudinal direction of the optical fiber, and FIG. 3B is a cross-sectional view. It is.
In addition, while attaching | subjecting the same code | symbol about the part similar to 1st embodiment mentioned above, it abbreviate | omits about the detailed description.

  The optical fiber sensor 1B (1) of this embodiment is an optical fiber sensor 1 in which a strain detection first optical fiber 3 and a temperature compensation second optical fiber 4 are provided on the same base material 2. The first optical fiber 3 is fixedly disposed on the base material 2, and the second optical fiber 4 is formed in the space 5 </ b> B formed on the base material 2 in the immediate vicinity of the first optical fiber 3. Arranged inside.

In particular, in the optical fiber sensor 1 of the present embodiment, the gap 5B is formed by winding a part 2a of the base material 2 so as to cover the outer periphery of the second optical fiber 4 along the second optical fiber 4. Has been.
That is, the optical fiber sensor 1 of the present embodiment has a structure in which the gap portion 5B is formed by bending a part 2a of the substrate 2 and the second optical fiber 4 is arranged in the gap portion 5B.

  As described above, the second optical fiber 4 fiber is arranged in the gap portion 5B that exists in the longitudinal direction of the sensor, and is protected by a part of the base material 2 so that the second optical fiber 4 is caused by the external adaptation force. It is possible to protect from being injured and no trouble is caused in strain measurement.

  A part of the end 2b of the bent base 2 may be in contact with one surface of the base 2 or a gap may be opened. However, the size of the gap is assumed to be smaller than the diameter of the second optical fiber 4. Thereby, the 2nd optical fiber 4 does not jump out from the space | gap part 5B, and it can protect reliably over a longitudinal direction. A part of the end 2 b of the substrate 2 may be fixed to one surface of the substrate 2 by the fixing agent 10.

  Further, since the end 2b of the part of the bent base material 2 has only a gap or is in contact with the base material 2, it can be easily opened from this point. As a result, the optical fiber can be easily extracted. Since the second optical fiber 4 has an extra length equal to or greater than the elongation strain due to the expansion of the pipe, no elongation strain is applied.

  In the optical fiber sensor 1B (1) having such a configuration, the second optical fiber 4 is disposed on the base material 2 but is not fixed to the base material 2. It is not affected by the distortion of the measurement object. That is, it is possible to detect only the strain due to expansion and contraction accompanying the temperature change of the second optical fiber 4 without detecting the strain of the measurement object. As a result, there is no temperature compensation error. As a result, the detection value of the first optical fiber 3 is corrected with the detection value of the second optical fiber 4, resulting in pure deformation or thinning of the measurement object. Only distortion can be detected in a distributed manner.

Hereinafter, a manufacturing method of the optical fiber sensor 1B (1) of the present embodiment will be described.
FIG. 4 is a process diagram showing an example of a manufacturing process of the optical fiber sensor 1B (1). In FIG. 4, when the same components as those described in FIG. 3 are indicated, the reference numerals used in FIG. 3 are used as they are, and detailed descriptions thereof are omitted.

  The base material 2 and the temperature-compensating second optical fiber 4 wound in a roll shape are simultaneously introduced into the fixing agent applicator 40 with the temperature-compensating second optical fiber 4 attached to the base material 2. To do. And the solution containing the monomer of thermosetting resin (namely, fixing agent 10) is apply | coated to a part on base material 2 in the fixing agent applicator 40 [refer FIG.4 (b)].

  Subsequently, the base material 2 and the second optical fiber 4 coated with the solution are simultaneously introduced into the base material processing device 41. Then, in the base material processing device 41, a part 2 a of the base material 2 is wound along the second optical fiber 4 so as to cover the outer periphery of the second optical fiber 4 and bent. At this time, a gap 5B is provided between the part 2a of the base 2 and the second optical fiber 4.

  Subsequently, the base material 2 partially bent and the second optical fiber 4 for temperature compensation are simultaneously introduced into the heating furnace 42. The inside of the heating furnace 42 is set to a temperature higher than the temperature necessary for the monomer to cure, and from the outlet of the heating furnace 42, a part of the end 2 b of the bent base material 2 is formed. However, what is fixed on one surface of the base material 2 by the fixing agent 10 is drawn out (see FIG. 4C).

Subsequently, the first optical fiber 3 for strain detection wound in a roll shape is simultaneously introduced into the fixing agent applicator 43 with the first optical fiber 3 for strain detection attached to the base material 2. .
Then, in the fixing agent applicator 43, a solution containing a monomer of a thermosetting resin (that is, the fixing agent 9) is applied to the first optical fiber 3 for strain detection, and the first light for strain detection is applied. The fiber 3 is covered with the solution [see FIG. 4 (a)].

  Subsequently, the base material 2, the first optical fiber 3 for strain detection and the second optical fiber 4 for temperature compensation covered with the solution are simultaneously introduced into the heating furnace 44. The inside of the heating furnace 44 is set to a temperature higher than the temperature necessary for the monomer to cure, and from the outlet of the heating furnace 44, a first optical fiber for strain detection is formed on the substrate 2. 3 and the second optical fiber 4 for temperature compensation are drawn out. This completes the curing of the thermosetting resin that is the fixing agent 7 until the subsequent take-off, thereby forming the optical fiber sensor 1B of the present embodiment, and is finally wound up in a roll shape [see FIG. 4 (c)]. ].

<Third embodiment>
Next, a third embodiment of the present invention will be described.
FIG. 5 shows a third embodiment of the optical fiber sensor of the present invention, and is a perspective view when cut along a plane perpendicular to the longitudinal direction of the optical fiber.
In addition, while attaching | subjecting the same code | symbol about the part similar to 1st embodiment mentioned above, it abbreviate | omits about the detailed description.

  The optical fiber sensor 1C (1) of this embodiment is an optical fiber sensor in which a first optical fiber 3 for strain detection and a second optical fiber 4 for temperature compensation are provided on the same base material 2. The first optical fiber 3 for strain detection is fixedly disposed on the substrate 2, and the second optical fiber 4 for temperature compensation is located in the immediate vicinity of the first optical fiber 3 for strain detection. It is disposed inside a gap 5C formed on the material 2.

In particular, in the optical fiber sensor 1C of the present embodiment, the second optical fiber 4 is formed by a pipe-shaped forming material 20 having a gap portion 5C.
That is, the optical fiber sensor 1 of the present embodiment has a structure in which the second optical fiber 4 is arranged in a pipe-shaped forming material 20 having a gap 5C.

  As described above, the second optical fiber 4 is disposed in the gap portion 5C existing in the longitudinal direction of the sensor, so that the second optical fiber 4 can be protected from being damaged by the external adaptation force. , No trouble in strain measurement.

  The forming material 20 is not particularly limited as long as it has a heat resistance temperature equal to or higher than the highest temperature achieved in the intended installation environment. For example, in addition to various metals, polyethersulfone and polyarylate (long-term heat resistance) 150 ° C.), polyether imide (long-term heat-resistant temperature 170 ° C.), polyamideimide, polyetheretherketone, wholly aromatic polyester (long-term heat-resistant temperature 230 to 240 ° C.) and the like are used.

  The forming material 20 has a hollow pipe shape, and the forming material 20 is fixed to the base material 2 with a fixing agent 21 in the longitudinal direction. Since the optical fiber sensor 1C is helically installed in a pipe that is a measurement object, elongation strain due to thermal expansion is mainly applied in the radial direction of the optical fiber. Since the second optical fiber 4 has an extra length equal to or longer than the elongation strain due to the expansion of the pipe, no elongation strain is applied to the second optical fiber 4.

  Thus, by arranging the second optical fiber 4 inside the gap 5C, the second optical fiber 4 can be brought into a state in which no distortion due to the surrounding stress is applied. As a result, the second optical fiber 4 can detect only distortion due to temperature change, that is, distortion caused by Brillouin frequency shift and linear expansion of the optical fiber itself. Since the amount of strain changes linearly with respect to temperature change, the temperature can be accurately obtained from the measured amount of strain.

  Further, the joint 20a of the forming material 20 is in contact with the surface of the base material 2 in the longitudinal direction. When the base material 2 and the first optical fiber 3 are separated by bending the base material 2 in the direction opposite to the direction in which the fibers are arranged, the joint 20a of the forming material 20 that protects the second optical fiber 4 is also external. Will be exposed to. Accordingly, the optical fiber can be easily extracted by opening the joint 20a exposed to the outside. Moreover, the fixing date 21 does not penetrate | invade into an inside from a joint by making the joint date of the forming material 20 contact the base material 2, and protects the 2nd optical fiber 4 over a longitudinal direction reliably. be able to.

Hereinafter, a manufacturing method of the optical fiber sensor 1C of the present embodiment will be described.
FIG. 6 is a process diagram showing an example of a manufacturing process of the optical fiber sensor 1C. In FIG. 6, when the same components as those described in FIG. 5 are indicated, the reference numerals used in FIG. 5 are used as they are, and detailed descriptions thereof are omitted.

  The second optical fiber 4 and the forming material 20 wound in a roll shape are simultaneously introduced into the forming machine 50. At this time, the forming material 20 is vertically attached on the outer periphery 41 of the second optical fiber 4. At this time, a gap 5C is provided between the forming material 20 and the second optical fiber 4 (see FIGS. 6B to 6D).

  Subsequently, the base material 2 wound in a roll shape, the first optical fiber 3 and the formed second optical fiber 4 are attached to the base material 2 with the first optical fiber 3 and the second optical fiber 4 attached. At the same time, it is introduced into the fixing agent applicator 51. Then, a solution containing a monomer of a thermosetting resin (that is, the fixing agents 7 and 21) is applied in the fixing agent applicator 51, and the first optical fiber 3 and the forming material 20 are covered with the solution.

  Subsequently, the first optical fiber 3 coated with the solution and the formed second optical fiber 4 are simultaneously introduced into the heating furnace 52 while being attached to the substrate 2. The inside of the heating furnace 52 is set to a temperature that is higher than the temperature necessary for the monomer to cure, and from the outlet of the heating furnace 52, the first solution coated on the substrate 2 The optical fiber 3 and the formed second optical fiber 4 for temperature compensation are provided. This completes the curing of the thermosetting resin as the fixing agents 7 and 21 until the subsequent take-off, and becomes the optical fiber sensor 1C of this embodiment, and is finally wound up in a roll shape [FIG. )reference].

  The optical fiber sensor of the present invention can be applied to an optical fiber sensor used for measuring strains of various structures under extremely high temperature environment such as piping arranged in a power plant, a plant, etc. and a manufacturing method thereof. It is.

It is the perspective view and sectional drawing which show an example of the optical fiber sensor of this invention. It is process drawing which shows an example of the manufacturing process of the optical fiber sensor shown in FIG. It is the perspective view and sectional drawing which show another example of the optical fiber sensor of this invention. It is process drawing which shows an example of the manufacturing process of the optical fiber sensor shown in FIG. It is the perspective view and sectional drawing which show another example of the optical fiber sensor of this invention. It is process drawing which shows an example of the manufacturing process of the optical fiber sensor shown in FIG.

Explanation of symbols

  1A, 1B, 1C optical fiber sensor, 2 substrate, 3 first optical fiber for strain detection, 4 second optical fiber for temperature compensation, 5A, 5B, 5C gap, 6 lid, 7, 8, 10 , 21 Fixing agent, 20 forming material.

Claims (6)

An optical fiber sensor in which a first optical fiber for strain detection and a second optical fiber for temperature compensation are provided on the same base material,
The first optical fiber is fixedly disposed on the substrate;
The optical fiber sensor, wherein the second optical fiber is disposed in the space formed on the substrate in the immediate vicinity of the first optical fiber. A plurality of the first optical fibers are disposed on the substrate so as to sandwich the second optical fiber,
A lid is disposed so as to straddle the top of each first optical fiber as seen from the axial direction of the first optical fiber,
The optical fiber sensor according to claim 1, wherein the gap is formed by the base material, the first optical fiber, and the lid.   2. The gap is formed by winding a part of the base material so as to cover an outer periphery of the second optical fiber along the second optical fiber. Fiber optic sensor.   4. The one surface of the substrate and a part of the end of the wound substrate are in contact with each other, or a gap between them is smaller than the diameter of the second optical fiber. An optical fiber sensor described in 1.   The optical fiber sensor according to claim 1, wherein the second optical fiber is formed by a pipe-shaped forming material having a gap.   The optical fiber sensor according to claim 5, wherein a joint of the forming material is in contact with the base material.

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