JP2007024798A - Liquid leakage detection device by optical fiber sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid leakage detection device by an optical fiber sensor detecting leakage liquid, and specifying liquid leakage, by utilizing ultrasonic leakage generated by contact of an object like water having ultrasonic propagation speed lower than the optical fiber with the optical fiber, by making ultrasonic waves propagate through the optical fiber. <P>SOLUTION: In this device equipped with the optical fiber 1, an ultrasonic oscillator 8 for making the ultrasonic wave propagating through the optical fiber 1 generated, and a measuring means measuring the intensity of the ultrasonic wave propagating through the optical fiber 1, lowering of the ultrasonic intensity generated by leakage of the ultrasonic wave at a contact spot of liquid (water) with the optical fiber 1 is measured by the measuring means, to thereby detect the liquid leakage. As a means of measuring the intensity of the ultrasonic waves, an FBG sensor detecting the ultrasonic wave by FBG 6 by providing the FBG 6 in the optical fiber 1, or a piezoelectric sensor is used. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical fiber sensor leakage detection device applied as, for example, an optical fiber sensor leakage detection device that detects leakage in a pipeline, a building, or the like.

  The following research has been reported in academic papers regarding water leakage detection using optical fiber sensors. Spirin et al. Attach an optical fiber with a fiber Bragg grating (hereinafter referred to as "FBG") to a material that absorbs and expands water so that the optical fiber is distorted by water absorption. A method for detecting leaks is proposed. The distortion which an optical fiber receives can be measured from the reflection wavelength of FBG (refer nonpatent literature 1).

  MacLean et al. Proposed to attach an optical fiber to a water-swelling material, distort the optical fiber by water absorption, and evaluate the distortion of the optical fiber using the OTDR method (Optical Time Domain Reflectometry) (see Non-Patent Document 2). .

  Conventionally, the following invention is known as a water leak detection method using an optical fiber sensor. The same as MacLean wrote in the paper, but strains the optical fiber using a material that absorbs or expands or absorbs water, measures the strain received by the optical fiber by the OTDR method, and determines whether there is water leakage from the strain change. The invention to detect is proposed (refer patent document 1).

  And the invention which detects water leak using the big bending | flexion to an optical fiber by a deformation | transformation of a water absorption expansion | swelling material at the time of water leakage, and an optical transmission loss increases is proposed (refer patent document 2). In the present invention, water leakage can be detected by measuring the change in light intensity that enters the optical fiber and reaches the other end.

  Furthermore, an invention that blocks the optical transmission path by water leakage using a water-absorbing expansive material (see Patent Document 3), a water-absorbing expansion material and an optical fiber are put in the pipe, and the expansion material is deformed by the water leakage, and transmission of the optical fiber An invention (see Patent Document 4) that detects water leakage by increasing loss has been proposed.

  The present inventor has already proposed means for providing an ultrasonic sensor by providing an FBG in an optical fiber as a technique for measuring the intensity of ultrasonic waves propagating in an optical fiber (see Patent Document 5).

JP 2004-45226 A JP 2004-45220 A JP-A-9-43089 JP-A-5-322690 Japanese Patent Laid-Open No. 2005-9937 By Spirin, Optics and Lasers inEngineering, 32, 2000, p.497-503 MacLean, Sensors and Actuators A 109,2003, p.60-67

  The conventionally proposed leak detection device using an optical fiber as described above utilizes a method such as deforming an optical fiber through a material that deforms due to water absorption or blocking optical transmission. The principle is to examine the presence or absence of water leakage by measuring the deformation of the optical fiber or measuring the light intensity.

Such a conventional water leak detector using an optical fiber has the following problems.
(1) Non-Patent Document 1 discloses a means for measuring deformation caused by a water-absorbing expansion material on an optical fiber by FBG. However, since the FBG can only measure the strain in the vicinity, it is necessary to provide a large number of FBGs over the entire measurement area in order to detect water leakage. If water leakage occurs at a location away from the FBG installation location, it cannot be detected.

  (2) Non-Patent Document 2 discloses a technique for measuring deformation of an optical fiber using OTDR. OTDR measuring devices are very expensive and take time to measure. In addition, the position resolution of OTDR strain measurement is 1 meter or more, and the location accuracy of the water leakage location is poor.

  (3) Patent Document 1 discloses that a strain is applied to an optical fiber via a water-swelled material and the strain is measured by OTDR. This means is disclosed in Non-Patent Document 1 above. There are similar shortcomings.

  (4) Patent Document 2 discloses a means for examining the presence or absence of water leakage from a change in optical transmission intensity caused by bending loss of an optical fiber because the material that has absorbed and expanded water gives bending strain to the optical fiber. The influence of the bending of the fiber on the light transmission intensity is small, and it is difficult to detect water leakage with high sensitivity by this means.

  In the conventional technologies listed in Patent Documents 1 to 4 and Non-Patent Documents 1 and 2, water leakage is detected by utilizing deformation of the liquid-absorbing expansion material. However, the expansion coefficient of the absorbent material is considered to depend on the type of liquid to be absorbed. For this reason, when inspecting leakage of other liquids such as oil, it is considered that the expansion material needs to be replaced for each liquid to be detected.

  An object of the present invention is to solve the above-mentioned conventional problems. An ultrasonic wave is propagated through an optical fiber, and an object whose propagation speed is lower than that of the optical fiber, such as water, contacts the optical fiber. An optical fiber sensor leakage detection device that detects leakage, specifies a leakage location, and the like by utilizing ultrasonic leakage generated by the above is realized. In addition, the object in which ultrasonic leakage occurs includes most liquids such as oil in addition to water.

  In order to solve the above-described problems, the present invention includes an optical fiber, an ultrasonic oscillator that generates an ultrasonic wave that propagates through the optical fiber, and a measurement unit that measures the intensity of the ultrasonic wave that propagates through the optical fiber. The optical fiber sensor leakage detection device detects a leakage by measuring a decrease in ultrasonic intensity caused by leakage of the ultrasonic wave at a location where the liquid is in contact with the optical fiber by the measuring means. An optical fiber sensor leakage detection device is provided.

  The means for measuring the intensity of the ultrasonic wave preferably includes an FBG sensor that detects an ultrasonic wave by providing an FBG on the optical fiber, or a piezoelectric sensor.

  The optical fiber may be provided with a plurality of FBG sensors as means for measuring the intensity of the ultrasonic wave, so that the location of leakage can be identified.

In order to solve the above-described problems, the present invention provides an optical fiber and an ultrasonic oscillator that generates ultrasonic waves that propagate through an optical fiber that is not water-absorbing and is disposed on a support base having a small ultrasonic propagation attenuation. An optical fiber sensor leakage detection device comprising a measuring means for measuring the intensity of ultrasonic waves leaked at a location where the liquid contacts the optical fiber,
A plurality of measuring means for measuring the intensity of the ultrasonic wave are provided around the optical fiber, and the plurality of measuring means can respectively detect a leaking ultrasonic wave to identify a liquid leak location. An optical fiber sensor leakage detection device is provided. In the present invention, “without water absorption” includes not only a structure without water absorption but also a structure with “low water absorption”.

  The liquid to be detected for leakage is a liquid whose ultrasonic propagation speed is lower than that of the optical fiber, and may be configured to leak a part of the ultrasonic wave that propagates by contacting the optical fiber.

  The liquid to be detected for liquid leakage may be water, oil alcohol, or liquid sodium, and may have a configuration of an optical fiber sensor leakage detection device.

 According to the optical fiber sensor leakage detection device according to the present invention having the above-described configuration, a plurality of FBGs are provided as ultrasonic sensors, and the leakage location is identified by examining the change in ultrasonic intensity detected by each FBG. be able to.

  If a material with low ultrasonic propagation attenuation is used as an optical fiber support base and a material with low water absorption or low water absorption and low ultrasonic propagation attenuation is used, and an optical fiber is disposed thereon, an optical fiber is provided. Ultrasonic waves leaking from the light propagate to the optical fiber support. By arranging the ultrasonic sensor on the optical fiber support and specifying the ultrasonic wave generation source, it is possible to specify the location of liquid leakage.

  DESCRIPTION OF EMBODIMENTS Embodiments of an optical fiber sensor leakage detection device according to the present invention will be described below with reference to the drawings based on examples.

(principle)
The operation principle of the optical fiber sensor leakage detection device according to the present invention will be described. In the present invention, the principle of ultrasonic propagation is used. This principle will be described first. When the object A having the ultrasonic propagation velocity V ₁ is in contact with the object B having the ultrasonic propagation velocity V ₂ , the ultrasonic wave propagating through the object A parallel to the interface is an angle θ ( It is known that it propagates at an angle from the vertical direction of the interface (Snell's law).

Formula 1 always holds in the range of V ₁ > V ₂ , and a part of the ultrasonic wave propagates from the object A to the object B, that is, the ultrasonic wave leaks from the object A to the object B. On the other hand, when V ₁ <V _2, the ultrasonic wave propagating through the object A is totally reflected at the interface with the object B and does not leak to the object B.

An optical fiber sensor leakage detection device according to the present invention applies the above-described ultrasonic wave propagation principle, and its operation principle will be described with reference to FIG. Longitudinal ultrasonic waves 2 are propagated to an optical fiber 1 from an ultrasonic oscillator (not shown). Longitudinal wave velocity of the optical fiber ₁ V 1 = 5,380m / s, a longitudinal wave velocity V ₂ = 1,480m / s of water, satisfying the condition of V _1> V ₂ in Equation 1.

  Accordingly, when the optical fiber 1 comes into contact with the water 3, a part of the ultrasonic wave 2 propagating through the optical fiber 1 leaks into the water 3, and the intensity of the ultrasonic wave propagating through the optical fiber 1 is reduced. By detecting a decrease in the intensity of ultrasonic waves propagating through the optical fiber due to this leakage, it is possible to detect ultrasonic leakage into the water 3.

  The liquid to be detected by the liquid leakage is a liquid whose ultrasonic propagation speed is lower than that of the optical fiber 1, and may be any liquid that leaks a part of the ultrasonic wave 2 that propagates by contacting the optical fiber 1. . The ultrasonic propagation velocity is proportional to the square root of the quotient of Young's modulus and density of the propagation medium. Liquids have a lower Young's modulus compared to solids and should almost always be lower than the speed of sound of ultrasonic wave 2 where light propagates through the fiber (glass fiber).

  Therefore, the detection target can be applied not only to water but also to detection of liquids such as oil and alcohol. In the present invention and the present specification, “oil” is a general term for liquids produced from petroleum such as heavy oil, light oil, gasoline, and lubricating oil, other mineral oils, and vegetable oils.

  In addition, since the component of the optical fiber 1 is silica and can be used up to a high temperature of 1000 ° C. or higher, a molten metal having a melting point lower than that, such as liquid sodium (used as a coolant for a nuclear reactor), is an object of detection. obtain. The specific configuration of the optical fiber 1 sensor leakage detection device according to the present invention based on the above operation principle will be described in the following examples.

  FIG. 2 is a diagram showing a configuration example of a device for realizing leakage detection based on the above principle, and is also a diagram for explaining Example 1 of the optical fiber sensor leakage detection device 4 according to the present invention. FBG has a property of reflecting narrowband light centered on a certain wavelength, called a Bragg wavelength. This Bragg wavelength is known to change in proportion to the strain experienced by the FBG.

  Therefore, the laser oscillation wavelength is adjusted to a wavelength at which the gradient change in the reflectance-wavelength relationship of the FBG is steep, and the reflected light or transmitted light intensity of the FBG or both light intensities are measured. Usually, the laser oscillation wavelength is set to a wavelength at which the reflectance is halved. Since the reflectivity of the FBG at the laser oscillation wavelength varies according to the strain caused by the ultrasonic wave, when the ultrasonic wave propagates through the FBG, the reflected light and transmitted light intensity change.

  In FIG. 2, a laser light source 5 is connected via an optical circulator 7 to an optical fiber 1 provided with an FBG 6 (a sensor having an FBG 6 is referred to as an FBG sensor). The optical fiber 1 is attached to the ultrasonic oscillator 8 with an adhesive. The ultrasonic oscillator 8 has a role of receiving an ultrasonic excitation signal from the signal generator 9 to generate an ultrasonic wave and propagating the ultrasonic wave to the optical fiber 1.

  The optical circulator 7 is connected to a reflected light photoelectric converter 10 for measuring the intensity of reflected light from the FBG. The FBG 6 is connected to the distal end side of the optical fiber 1, and further on the distal end side, the optical fiber 1 is connected to a transmitted light photoelectric converter 11 that measures the transmitted light intensity of the FBG. The reflected light photoelectric converter 10 and the transmitted light photoelectric converter 11 are connected to a data recording device 12. A range from a point fixed to the ultrasonic oscillator 8 to a place where the FBG 6 is provided is a water leakage detection region.

  When water leakage is detected, the optical fiber 1 in the range of the water leakage detection region is placed on an object 13 having no water absorption. Laser light from the laser light source 5 enters the optical fiber 1 provided with the FBG 6 via the optical circulator 7. The reflected light from the FBG 6 enters the reflected light photoelectric converter 10 via the optical circulator 7. The transmitted light of the FBG 6 is incident on the transmitted light photoelectric converter 11. The above “not having water absorption” includes the case of “low water absorption”. The same applies to “no water absorption” described below.

  Furthermore, ultrasonic waves are propagated from the ultrasonic oscillator 8 to the optical fiber 1, and the laser oscillation wavelength is adjusted to a wavelength at which the reflectance of the FBG 6 is reduced by half, so that the reflected light photoelectric converter 10 and the transmitted light photoelectric converter 11 Measure each output. When water comes into contact with the optical fiber 1 and a part of the ultrasonic wave propagating through the optical fiber 1 leaks, the intensity of the ultrasonic wave propagating through the optical fiber 1 decreases, and the output of the photoelectric converter changes.

(Experimental example)
In order to confirm the effect of the optical fiber sensor leakage detection device according to the present invention, a verification experiment of the optical fiber sensor leakage detection device was performed. In this experiment, a setup as shown in FIG. That is, by providing the flange 15 as a jig under the pipe 14, water leakage from the pipe 14 can be collected in the flange 15.

  In this experiment, as shown in FIG. 3 (a), the optical fiber 1 is disposed in a recessed portion of the flange 15 (length 1 meter), and one end of the optical fiber 1 is attached to the ultrasonic oscillator 8 with an adhesive. The FBG 6 is provided at the other end. Then, 2ml of water was dropped on the jar to simulate water leakage.

  In this experiment, in order to generate longitudinal wave ultrasonic waves in the optical fiber 1, a shear ultrasonic wave generation type having a center frequency of 250 kHz was used for the ultrasonic oscillator 8. A 250 kHz tone burst wave was used as an ultrasonic excitation signal from a signal generator (not shown). Also, the coating layer of the optical fiber in the detection range is removed for the purpose of increasing the ultrasonic wave propagation efficiency of the optical fiber.

  The result of this experiment is shown in FIG. FIG. 3B shows the ultrasonic excitation signal sent to the ultrasonic oscillator and the reflected light output from the FBG 6 before and after leakage (corresponding to the light intensity detected by the reflected light photoelectric converter 10 in FIG. 2). Show.

The response signal amplitude V _pp , which was 285 mV before water leakage, dropped to 154 mV after 2 ml of water was dripped. This is because a part of the ultrasonic wave propagating through the optical fiber 1 has leaked, so that the intensity of the ultrasonic wave reaching the FBG 6 is reduced. In this way, it is possible to detect water leakage by detecting the presence or absence of water on the optical fiber using this principle.

  Next, in the configuration shown in FIG. 3 (a), a response is made when water 3 is brought into contact with the optical fiber 1 only at one place as the case 1 and at two places as the case 2 as shown in FIG. 4 (a). I investigated.

  In the experiment shown in FIG. 3, only the reflected light output from the FBG 6 is displayed. However, the same measurement can be performed using the transmitted light output of the FBG 6. In addition, since the response of the transmitted light and the reflected light is in an opposite phase relationship, an ultrasonic response signal having a higher S / N ratio can be obtained by changing and adding the sign of one of the signals.

  That is, the intensity of the ultrasonic wave propagating through the optical fiber 1 gradually attenuates as the propagation distance increases. For this reason, when the inspection region is widened, highly sensitive ultrasonic detection is required. Therefore, by combining the reflected light and transmitted light signal, the S / N ratio of the detection signal is increased to enable wide area detection.

For such signal processing, the present inventors pass the reflected light from the FBG sensor when a broadband light source is used in Japanese Patent Application Laid-Open No. 2004-177134, through an optical filter, and synthesizes the reflected light and the transmitted light. Although it has already been proposed that a signal with a higher S / N ratio can be obtained, the same idea can be applied when a laser light source is used as in the present invention.

  FIG. 4B shows the reflected light intensity and transmitted light intensity (corresponding to the light intensity detected by the transmitted light photoelectric converter 11 in FIG. 2) of the FBG 6 before water is brought into contact with the optical fiber 1, and a combination thereof. Signal strength. The S / N ratio of the reflected light signal was 61 dB. The reflected light and the transmitted light intensity are in opposite phase to each other, and the S / N ratio of the synthesized signal obtained by inverting the sign of the reflected light intensity and adding it to the transmitted light intensity is improved to 70 dB. Thus, by combining the reflected light intensity and the transmitted light intensity, a signal with a higher S / N ratio can be obtained.

FIG. 4C shows a response signal obtained by synthesizing the transmitted light and the reflected light signal in the case of no leakage, case 1 and case 2. The magnitude of the signal amplitude V _pp was 793, 426, and 274 mV for the case 1 and case 2 without water leakage, respectively. That is, compared with the case without water leakage, the response strength of case 1 assuming one place of water leakage is reduced, and in case 2 assuming water leakage at two places, the response strength is further reduced. Thus, as the number of water leakage points increases, the ultrasonic response intensity decreases.

  FIG. 5 is a diagram for explaining the second embodiment. The second embodiment is characterized in that a piezoelectric sensor 16 using a piezoelectric element is adopted as an ultrasonic sensor for detecting an ultrasonic wave propagating through the optical fiber 1. Ultrasonic waves generated from the ultrasonic oscillator 8 as shown in FIG. 5 propagate through the optical fiber and can be detected by the piezoelectric sensor 16 attached to the other end.

  Also in this case, since water adheres to the optical fiber between the piezoelectric sensor 16 and the ultrasonic oscillator 8, and the ultrasonic leak is detected, the ultrasonic intensity detected by the piezoelectric sensor is reduced, so that the water leak can be detected.

  FIG. 6 is a diagram for explaining the third embodiment. The third embodiment has substantially the same configuration as that of the first embodiment shown in FIG. 2, but a plurality of FBG1 to FBGN having different Bragg wavelengths as an ultrasonic sensor are provided on the optical fiber 1 as shown in FIG. 6 (a). It is the structure which enabled it to identify a water leak location by providing in multiple places (N places). The description of the same configuration as that of the first embodiment will be omitted, and the following description will be focused on the features of the third embodiment.

  As shown in FIG. 6A, ultrasonic waves are propagated to the optical fiber 1 from the ultrasonic oscillator 8 located on the laser light source 5 side of the optical fiber 1. At this time, it is assumed that water leaks between FBG2 and FBG3. The ultrasonic intensity detected by the FBG 1 and FBG 2 existing from the ultrasonic oscillator to the water leakage location is not affected by the ultrasonic intensity decrease due to water leakage.

On the other hand, FBG 3 to FBG N existing outside the range of the ultrasonic oscillator-water leakage location are affected by ultrasonic leakage due to water leakage, and the detected ultrasonic intensity is reduced. Now, it is assumed that the reflection characteristics of FBG 1 to FBG N are represented in FIG. For example, when the laser oscillation wavelength is set to λ ₁ , the reflected light photoelectric converter 10 and the transmitted light photoelectric converter 11 detect an ultrasonic response to the FBG 1.

Thus, by setting the laser oscillation wavelength to a wavelength at which the reflectance of the FBG to be measured is reduced by half (in the example shown in FIG. 6B, FBG 1, FBG 2, FBG 3,... For the FBG N, the laser oscillation wavelength is set to λ ₁ , λ ₂ , λ ₃ ,..., Λ _N ), and the ultrasonic response can be detected by selecting from a plurality of existing FBGs. it can. And a leak location can be specified by comparing the ultrasonic response strength of each FBG with the strength before leak.

  FIG. 7 is a diagram for explaining the fourth embodiment. In the fourth embodiment, as shown in FIG. 7 (a), the optical fiber 1 for detecting water leakage has an optical fiber support base 17, such as aluminum or stainless steel, which does not absorb water and has a small attenuation during ultrasonic wave propagation. It is placed on a plastic plate such as a metal plate or acrylic. A plurality of ultrasonic sensors 18 are arranged on the optical fiber support 17, and leaked ultrasonic responses detected by the ultrasonic sensors 18 are recorded in the data recording device 19.

  When water leakage occurs, ultrasonic waves leak from the optical fiber 1 to the optical fiber support 17. The leaked ultrasonic wave reaches the ultrasonic sensor 18 attached to the optical fiber support 17 and is detected. As shown in FIG. 7B, the ultrasonic arrival time detected by each ultrasonic sensor 18 depends on the distance between the ultrasonic generation source and the ultrasonic sensor. From the ultrasonic arrival times detected by the plurality of ultrasonic sensors 18, it is possible to identify the water leak location 20 that is an ultrasonic generation source.

  In Examples 1 to 4 of the optical fiber sensor leakage detection device according to the present invention described above, the details of the attachment object (eg, piping, tank wall, building wall, etc.) for attaching the optical fiber to the surface are partially Although the explanation is duplicated, it is as follows.

  For example, in the case of porous concrete, the water absorption is high, so even if an optical fiber is placed on the concrete, the leaked water is sucked by the concrete. However, when the concrete surface is coated with water absorption, water remains on the surface without being absorbed by the concrete. Among the optical fiber sensor leakage detectors according to the present invention, water leakage using FBG Detection technology (leakage detection technology using leakage ultrasonic waves as shown in Examples 1 to 3 and FIGS. 1 and 6) can be applied.

  However, since the ultrasonic wave propagation attenuation is large in concrete, it is not possible to apply the technique of detecting the leaked ultrasonic wave and locating the leaked point 20 using the ultrasonic sensor 18 shown in the fourth embodiment (see FIG. 7). Absent.

  In such a case, an optical fiber is disposed on a support base 17 such as a metal plate or a plastic plate that has no water absorption and has a small attenuation of ultrasonic wave propagation, and if this support base 17 is passed through, water leakage using FBG will occur. Optical fiber sensor leakage detection according to the present invention, including detection technology (see FIGS. 1 and 6) and technology (see FIG. 7) for detecting leakage ultrasonic waves by using the ultrasonic sensor 18 and locating the water leakage location 20 All the techniques of the device 4 can be applied.

  The best mode of the optical fiber sensor leakage detection device according to the present invention has been described above based on the embodiments. However, the present invention is not limited to such embodiments, and the technical scope described in the claims is not limited thereto. It goes without saying that there are various embodiments within the scope of the matter.

  Since the optical fiber sensor leakage detection device according to the present invention is configured as described above, it can be applied to a water leakage detection device in a pipeline, a building, etc. By applying the technology according to the present invention, it is possible to detect rain leaks with high accuracy. Further, leakage of hand-washing is a problem in aircraft, but the technology according to the present invention can also be applied to such a field.

It is a figure explaining the principle of operation of the optical fiber sensor leak detection apparatus concerning the present invention. It is a figure explaining Example 1 of the optical fiber sensor leak detection apparatus which concerns on this invention. It is a figure explaining the experiment example of the optical fiber sensor leak detection apparatus which concerns on this invention. It is a figure explaining the experiment example of the optical fiber sensor leak detection apparatus which concerns on this invention. It is a figure explaining Example 2 of the optical fiber sensor leak detection apparatus which concerns on this invention. It is a figure explaining Example 3 of the optical fiber sensor leak detection apparatus which concerns on this invention. It is a figure explaining Example 4 of the optical fiber sensor leak detection apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Ultrasonic wave 3 Water 4 Optical fiber sensor leak detection apparatus 5 Laser light source 6 FBG
DESCRIPTION OF SYMBOLS 7 Optical circulator 8 Ultrasonic oscillator 9 Signal generator 10 Photoelectric converter for reflected light 11 Photoelectric converter for transmitted light 12, 19 Data recording device 13 Object without water absorption 14 Pipe 15 １６ 16 Piezoelectric sensor 17 Optical fiber support stand 18 Ultrasonic sensor 20 Water leakage point

Claims (6)

An optical fiber sensor leakage detection device comprising: an optical fiber; an ultrasonic oscillator that generates an ultrasonic wave propagating through the optical fiber; and a measuring unit that measures the intensity of the ultrasonic wave propagating through the optical fiber. ,
An optical fiber sensor leakage detection device that detects a leakage by measuring a decrease in ultrasonic intensity caused by leakage of the ultrasonic wave at a location where the liquid is in contact with the optical fiber by the measuring means. .   2. The optical fiber sensor according to claim 1, wherein the means for measuring the intensity of the ultrasonic wave includes an FBG sensor provided with an FBG in the optical fiber and detecting an ultrasonic wave by the FBG, or a piezoelectric sensor. Leak detection device.   2. The optical fiber sensor leakage according to claim 1, wherein the optical fiber is provided with a plurality of FBG sensors as means for measuring the intensity of the ultrasonic wave, and the location of the leakage can be specified. Detection device. An optical fiber disposed on a support base having no water absorption and a small ultrasonic wave propagation attenuation, an ultrasonic oscillator for generating an ultrasonic wave propagating through the optical fiber, and a location where the liquid is in contact with the optical fiber An optical fiber sensor leakage detection device comprising a measuring means for measuring the intensity of leaked ultrasonic waves,
A plurality of measuring means for measuring the intensity of the ultrasonic wave are provided around the optical fiber, and the plurality of measuring means can respectively detect a leaking ultrasonic wave to identify a liquid leak location. An optical fiber sensor leakage detection device.   The liquid as a detection target of liquid leakage is a liquid whose ultrasonic propagation speed is lower than that of an optical fiber, and leaks a part of the ultrasonic wave propagating by contacting the optical fiber. The optical fiber sensor leak detection apparatus in any one of 1-4.   The optical fiber sensor leak detection device according to claim 1, wherein the liquid to be detected for liquid leak is water, oil, alcohol, or liquid sodium.

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