JP2012088155A - Measuring method using fbg sensor, and device thereof - Google Patents

Abstract

【Task】
In the measurement method and apparatus using the FBG sensor, the strain and temperature can be measured simultaneously by dividing the FBG sensor into one FBG sensor that senses strain and temperature and the FBG part that senses only temperature. It can be so.
[Solution]
Fix a part of the optical fiber with the diffraction grating on the core in a state that depends on the strain of the object to be measured, and fix the other part of the optical fiber with the diffraction grating on the core in a state that does not depend on the distortion of the object to be measured. Using a signal detected from a fixed portion fixed in a state dependent on the strain of the optical fiber to be measured and a signal detected from a portion fixed in a state independent of the strain of the optical fiber to be measured The strain and temperature of the object to be measured were measured.
[Selection] Figure 1

Description

The present invention relates to a measurement method and apparatus using an FBG sensor that includes a diffraction grating formed in an optical axis direction in an optical fiber and simultaneously measures temperature and strain.

In recent years, an FBG sensor system using a fiber Bragg grating (hereinafter referred to as FBG) has been proposed as means for measuring the temperature or strain of an object using an optical fiber. In the FBG sensor, a diffraction grating is formed by periodically repeating a high refractive index portion and a low refractive index portion at regular intervals in an optical fiber core.
FIG. 17 illustrates the principle of the FBG sensor. (A) shows the wavelength distribution of the optical signal input to the FBG sensor, and (b) shows a cross-sectional view of the FBG sensor. (C) shows the wavelength distribution of the optical signal reflected and output by the FBG sensor among the input optical signals, and (d) shows the wavelength distribution of the optical signal transmitted through the FBG sensor among the input optical signals. The optical fiber 500 is configured by a grad 502 that is arranged around a core 501 that is a thin material formed of quartz glass and covers the periphery thereof. Since quartz glass is fragile, it is covered with a protective coating 503. In the core 501, a periodic diffraction grating 505 is formed in a range of a length L at a pitch Λ. The diffraction grating 505 is formed by periodically changing the refractive index of the core 501 by irradiating the optical fiber core 501 with interference fringes of ultraviolet light (for example, around 250 nm wavelength) by a method not shown. Is possible. A portion where the diffraction grating 505 is formed is referred to as an FBG sensor.

If the interval between the interference fringes is changed, the diffraction grating formed on the core 501 can be manufactured at an arbitrary pitch. When an optical signal 506 having a multi-wavelength λ is incident on the FBG sensor, only the λ _B optical signal 507 is reflected by the FBG sensor according to the relational expression λ _B = N _eff Λ, and the other optical signals 508 are λ _B The optical signal 507 is transmitted with the removed distribution. Here, N _eff is the refractive index of the optical fiber, and Λ is the period of the diffraction grating. The reflection wavelength of the FBG sensor changes depending on the physical quantity that changes the refractive index of the optical fiber and the period of the diffraction grating. For example, when a thermal change occurs in the FBG sensor, the refractive index of the core 501 changes due to a temperature change, and the period of the diffraction grating 505 changes, so the wavelength of the reflected light 507 shifts. The shift amount due to this temperature is about 10 pm / ° C. when a wavelength band of 1.5 μm is used. Further, when the FBG sensor is distorted, the core 501 is stretched and contracted, so that the period of the diffraction grating 505 varies. The shift amount due to this distortion is about 1.2 pm / με. Therefore, when the FBG sensor is used as a measuring means, it is difficult to specify whether the wavelength change due to temperature change or the wavelength change due to distortion is only measured by measuring the change in reflection wavelength.
As a method for measuring temperature, there is a method described in Patent Document 1. In this method, the pad is fixed to an optical fiber in which a plurality of diffraction grating portions are formed at intervals in a core, a pad fixed to a temperature measurement object, and a groove formed in the measurement object. The optical fiber inserted in the protective tube in the pad is disposed. According to the present invention, since the optical fiber is fixed to the measurement object together with the pad, it is easier to measure the temperature of the measurement object as compared with the method of directly fixing the optical fiber to the measurement object.
As a method for measuring strain, there is a method described in Patent Document 2. In this method, a base fixed to a measurement target, a pair of arm portions erected on one surface side of the base via elastically deformable hinges, and an intermediate position between the pair of arm portions And a connecting portion for connecting the two through elastically deformable hinges, and is integrally formed of a material having an expansion coefficient equal to that of the measurement target, and receives the force for expanding and contracting the base from the measurement target. Of the first FBG fiber between the positions of one end side of the pair of arm portions of the fiber support that are separated by a predetermined distance from each other. Both ends are fixed in tension, and the second FBG fiber having the same characteristics as the first FBG fiber is disposed on the other end side of the pair of arm portions of the fiber support that is separated from the coupling portion by the predetermined distance. Balanced between positions It has been fixed. Therefore, for the distortion of the measurement object, the absolute value of the wavelength change amount of the reflected light of both FBG fibers is equal, the direction of the wavelength change is reversed, and for the temperature change, the reflected light of both FBG fibers is reflected. The absolute value of the wavelength change amount and the direction of the wavelength change are equal. Therefore, it becomes possible to accurately detect the distortion component to be measured in a state in which the influence of the temperature change is removed by subtracting the wavelength change amounts of both FBG fibers.

JP 2009-281789 A JP 2009-222397 A

However, the temperature measurement method described in Patent Document 1 can measure the temperature change of the object to be measured, but cannot measure the strain generated on the spot. In addition, the strain measurement method described in Patent Document 2 has a problem in that accurate temperature measurement cannot be performed although strain measurement capable of compensating for strain by temperature is possible. In either case, only temperature or strain alone can be measured in the FBG fiber.
The present invention has been made in view of the above-described problems, and an FBG sensor capable of simultaneously measuring temperature change and strain is used without using a plurality of FBG sensors even in a situation where temperature change and strain change occur simultaneously. An object of the present invention is to provide a measurement method and an apparatus therefor.

In order to achieve the above object, according to the present invention, in a measurement method using an FBG sensor, a part of an optical fiber in which a diffraction grating is formed on a core is fixed in a state depending on the strain of an object to be measured. The other part of the optical fiber on which the diffraction grating is formed is fixed in a state that does not depend on the distortion of the object to be measured, and the signal detected from the part of the optical fiber that is fixed in a state that depends on the distortion of the object to be measured and the optical fiber The strain and temperature of the object to be measured are measured using a signal detected from a fixed portion that is not dependent on the distortion of the object to be measured.
In order to achieve the above object, in the present invention, a measuring device using an FBG sensor is fixed in a state depending on the distortion of the object to be measured, and the other part is set to be a distortion of the object to be measured. An optical fiber in which a diffraction grating is formed on a core fixed in an independent state, light source means for emitting light, and light emitted from the light source means is incident on the optical fiber to cause distortion of the object to be measured. The reflected light reflected from the diffraction grating of the fixed part in the dependent state and emitted from the optical fiber, and the optical fiber reflected from the diffraction grating of the fixed part in a state independent of the distortion of the optical fiber to be measured A light detecting means for detecting the reflected light emitted from the light, a computing means for processing the signal obtained by detecting the reflected light by the light detecting means to calculate the strain and temperature of the object to be measured, and the computation Of measured object calculated by means It was constructed and an output means for outputting information about the temperature.

  According to the measurement method and the measurement apparatus using the FBG sensor of the present invention described above, strain and temperature can be measured simultaneously. Furthermore, it is possible to measure the same place at the same time. Furthermore, if a plurality of FBG parts are connected to a single optical fiber and the FBG part is attached in the same manner, there is an excellent effect that strain and temperature can be measured at a plurality of places.

FIG. 1 is a block diagram showing a configuration of a first example of an embodiment for carrying out the present invention. FIG. 2A is a front sectional view of the FBG sensor showing a state in which the FBG sensor is attached to an object to be measured in Example 1 of the present invention. FIG. 2B is a table showing the conditions of each region of the FBG sensor when the FBG sensor is attached to the object to be measured in Example 1 of the present invention. FIG. 2C is a front sectional view of the FBG sensor showing a state in which a part of the surface of the FBG sensor is coated with the same metal as the material of the object to be measured and attached to the object to be measured in Example 1 of the present invention. FIG. 2D is a side view of the FBG sensor showing a state in which a part of the surface of the FBG sensor is covered with the same metal plate as the material of the object to be measured and attached to the object to be measured in Example 1 of the present invention. Sectional drawing and (b) are front sectional drawings. FIG. 3A is a front view of a multiple FBG sensor, and FIG. 3B is a graph showing wavelength characteristics of reflected light detected from the multiple FBG sensor. 4A is a graph showing the wavelength characteristics of the reflected light detected from the FBG sensor, and FIG. 4B is a graph showing a differential waveform signal obtained by subjecting the detected waveform of the reflected light detected from the FBG sensor to differential processing. is there. FIG. 5 is a front view of a screen showing a display screen according to the present invention. FIG. 6A is a front view of the FBG sensor showing a state in which the FBG sensor is free with respect to the object to be measured. FIG. 6B is a graph showing a wavelength distribution waveform of reflected light detected from the FBG sensor before and after distortion occurs in the measurement object in a state where the FBG sensor is free with respect to the measurement object. FIG. 7A is a front view of the FBG sensor showing a state in which the FBG sensor is free with respect to the object to be measured. FIG. 7B is a graph showing a wavelength distribution waveform of reflected light detected from the FBG sensor before and after a temperature change occurs in the measurement object in a state where the FBG sensor is free with respect to the measurement object. . FIG. 8A is a front view of the FBG sensor showing a state in which the FBG sensor is entirely fixed to the object to be measured. FIG. 8B is a graph showing a wavelength distribution waveform of reflected light detected from the FBG sensor before and after distortion occurs in the measurement object in a state where the FBG sensor is fixed to the entire measurement object. FIG. 9A is a front view of the FBG sensor showing a state in which the FBG sensor is entirely fixed to the object to be measured. FIG. 9B is a graph showing a wavelength distribution waveform of reflected light detected from the FBG sensor before and after a temperature change occurs in the object under measurement with the FBG sensor fixed to the object under measurement. FIG. 10A is a front view of the FBG sensor showing a state in which a part of the FBG sensor according to the first embodiment of the present invention is fixed to the object to be measured and the other part is free from the object to be measured. FIG. 10B shows before and after distortion occurs in the measured object in a state where a part of the FBG sensor in the first embodiment of the present invention is fixed to the measured object and the other part is free with respect to the measured object. It is a graph which shows the wavelength distribution waveform of the reflected light detected from this FBG sensor. FIG. 11A is a front view of the FBG sensor showing a state in which a part of the FBG sensor according to the first embodiment of the present invention is fixed to the object to be measured and the other part is free with respect to the object to be measured. FIG. 11B occurs before and after the temperature change occurs in the measurement object in a state where a part of the FBG sensor in Example 1 of the present invention is fixed to the measurement object and the other part is free with respect to the measurement object. It is a graph which shows the wavelength distribution waveform of the reflected light detected from a later FBG sensor. FIG. 11C is a front view of the FBG sensor showing a state in which a part of the FBG sensor according to the first embodiment of the present invention is fixed to the object to be measured and the other part is free with respect to the object to be measured. FIG. 11D occurs before and after the temperature change occurs in the measurement object in a state in which a part of the FBG sensor in Example 1 of the present invention is fixed to the measurement object and the other part is free with respect to the measurement object. The graph showing the wavelength distribution waveform of the reflected light detected from the subsequent FBG sensor shows that the threshold value is set to determine the change in the wavelength width before and after the temperature change in the object to be measured. FIG. 12 is a flowchart for carrying out the present invention. FIG. 13A is a front sectional view of the FBG sensor showing a state in which the FBG sensor according to the second embodiment of the present invention is fixed to an object to be measured. FIG. 13B is a table showing conditions of each region of the FBG sensor when the FBG sensor is attached to the object to be measured in Example 2 of the present invention. FIG. 14 is a front sectional view of the FBG sensor showing a state in which the FBG sensor is attached to an object to be measured in the third embodiment of the present invention. FIG. 15 is a block diagram illustrating a case where the FBG sensor described in the first to third embodiments is applied to measurement of a generator in the fourth embodiment of the present invention. FIG. 16 is a block diagram illustrating a case where the FBG sensor described in the first to third embodiments is applied to measurement of a nuclear power generation facility in the fourth embodiment of the present invention. 17A and 17B are diagrams showing the principle of the optical FBG sensor. FIG. 17A shows the wavelength distribution of the optical signal input to the FBG sensor, and FIG. 17B shows a cross-sectional view of the FBG sensor. (C) shows the wavelength distribution of the optical signal reflected and output by the FBG sensor among the input optical signals, and (d) shows the wavelength distribution of the optical signal transmitted through the FBG sensor among the input optical signals.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 to FIG. 12 show a first example of an embodiment for carrying out the FBG sensor measuring method and measuring apparatus of the present invention.

  The configuration of a measuring apparatus using the FBG sensor in the first embodiment of the present invention will be described with reference to FIGS.

  The measuring apparatus using the FBG sensor in the present embodiment is configured to include an optical fiber 1 in which an FBG sensor 2 is formed in part, an FBG sensor measuring unit 6, a calculation unit 7, and a control unit 8.

  As shown in FIG. 2A, the FBG sensor 2 formed on a part of the optical fiber 1 fixes a part 2 a to the object to be measured 3 with an FBG sensor fixing member 4. The remaining part of the FBG sensor 2b is fixed by the optical fiber fixing member 5 in a free state so as not to depend on the distortion of the object 3 to be measured. When the FBG sensor fixing member 4 and the optical fiber fixing member 5 are used as adhesives, as shown in FIG. 2B, the adhesive used in the region 2a has the same thermal expansion coefficient and hardness as the object 3 to be measured. The adhesive used in the region 2b is not specified in terms of thermal expansion coefficient and hardness, but it is desirable to select an adhesive that can withstand the strain and temperature applied to the object 3 to be measured.

As a method of fixing the part 2a of the FBG sensor 2 with the FBG sensor fixing member 4, other methods are shown in FIGS. 2C and 2D.
In FIG. 2C, the surface of the FBG sensor 2b of the optical fiber 1 is coated with the same metal as the material of the object 3 to be measured 600. For example, if the DUT 3 is copper, the coating 600 may be copper. Further, the same effect can be obtained even if the FBG sensor 2b and the fixing member 601 of the object to be measured 3 are fixed by welding or brazing with the same material.
In FIG. 2D, a plate 603 made of the same metal as the material of the measurement object 3 is installed on the surface of the FBG sensor 2 b of the optical fiber 1. For example, if the DUT 3 is copper, the plate 603 may be copper. Even if the plate 603 is pressed and fixed so as to fix the FBG sensor 2b by the fixing tool 604, the same effect can be obtained.

  In any case, any means can be used as long as the FBG sensor 2b is fixed to the object 3 to be measured.

  The optical fiber 1 can constitute a plurality of FBG sensors 2. FIG. 3A shows the configuration of the optical fiber 1 of the multiple FBG sensor, and FIG. 3B shows the detected waveform. FBG sensors 2-1, 2-2, 2-3 and 2 -n are formed on the optical fiber 1 in accordance with an arbitrary pitch. Each FBG sensor 2 can change the reflection wavelength by changing the pitch Λ of the diffraction grating 505 shown in FIG. Furthermore, since the reflection wavelengths can be prevented from being overlapped by being separated from the estimated measurement temperature and the strain change wavelength by being separated from each other, it is possible to prevent erroneous detection. The detection waveforms of the plurality of FBG sensors are detected as λ-1, λ-2, λ-3, and λ-n.

  The FBG sensor measurement unit 6 includes a light source 9, an optical circulator 10, a photoelectric converter 11, and an A / D converter 12. Light emitted from the light source 9 passes through the optical circulator 10 and is projected onto the optical fiber 1. Only the wavelength corresponding to the pitch of the diffraction grating applied to the FBG sensor 2 is reflected from the light of the light source 9 by the FBG sensor 2. The light reflected by the FBG sensor 2 is reflected by the optical circulator 10 and received by the photoelectric converter 11. Here, the light source 9 uses a light source having a wide wavelength band such as an ASE (Amplified Spontaneous Emission) light source. Further, a swept light source capable of sweeping a wavelength in a wide band may be used. The wavelength range of the light source to be used is described in the present invention as a wavelength of about 1500 nm to 1590 nm, but any wavelength range may be used as long as the applied wavelength of the optical fiber 1 to be used corresponds to the FBG sensor 2. The photoelectric converter 11 receives light having a wavelength reflected by the FBG sensor 2, but uses a light whose wavelength and light amount can be detected as an output. The reflected light of the FBG sensor 2 detected by the photoelectric converter 11 is digitally converted by the A / D converter 12 and transmitted to the calculation unit 7.

  The calculation unit 7 includes a fixed part wavelength calculator 13, a free part wavelength calculator 14, a strain amount calculator 15, and a temperature calculator 16. The fixed portion wavelength calculator 13 calculates the wavelength from the light reflected by the fixed portion 2 a of the FBG sensor 2. The free part wavelength calculator 14 calculates the wavelength from the light reflected by the free part 2 b of the FBG sensor 2. The distortion amount calculator 15 converts the wavelength change calculated by the fixed portion wavelength calculator 13 into distortion and outputs the distortion. The temperature calculator 15 converts the wavelength change calculated by the free part wavelength calculator 14 into a temperature and outputs the temperature.

  FIG. 4 illustrates an embodiment for calculating the wavelength of the detected waveform. FIG. 4A shows a detection waveform 20 when reflected light from a general FBG sensor is detected. The horizontal axis of the graph indicates the wavelength, and the vertical axis indicates the reflected light detection output obtained by detecting the reflected light from the FBG sensor. FIG. 4B shows a differentiated waveform 21 obtained by subjecting the detected waveform 20 to a differentiation process. By calculating the intersection point 22 of the differential waveform 21 between the base level 23 and the differential waveform 21, the center wavelength of the detected waveform 20 can be calculated. In the calculation unit 7 shown in FIG. 1, the calculation of the wavelengths in the fixed part center calculator 13 and the free part center calculator 14 can be performed by the method described above. There is no problem even if other methods are used to obtain the wavelength of the detected waveform.

  In FIG. 1, the control unit 8 includes measurement condition input means 17, display means 18, and output means 19. The measurement condition input means 17 sets conditions necessary for measurement and determination conditions for measurement results. The display means 18 displays the measurement location, the display of the detected waveform, the display of the waveform center, the distortion after calculation, the temperature measurement result, and the like. The output means 19 can output the screen, measurement results, measurement conditions, etc. displayed by the display means 18 to an external memory or paper.

  FIG. 5 shows an example of a display screen on the display means 18. The display screen 300 includes an entire waveform display unit 301 of the FBG sensor 2, an enlarged display unit 302 of the entire waveform display 301, a measurement location display unit 303, a condition setting unit 304, a measurement result display unit 305, and a measurement result graph display unit 306. ing. In the entire waveform display unit 301, a waveform to be enlarged can be selected by a frame 307. In the enlarged display unit 302, the waveform in the frame 307 is enlarged. In the enlarged waveform, a frame 308 and a frame 309 can be set, and waveform processing is performed within this frame. The threshold 310 can be set in each of the frame 308 and the frame 309. In the processing of the detected waveform, the wavelength is calculated using a waveform having a threshold value 310 or more within the frames 308 and 309.

  The condition setting unit 304 can perform measurement start 3041, measurement stop 3042, FBG fiber switching 3043, threshold setting 3044, calculation range setting 3045, strain upper limit setting 3046, and temperature upper limit setting 3047.

  The measurement result display unit 305 can display the measurement results of strain and temperature corresponding to the FBG sensor. The measured value that is equal to or higher than the upper limit set by the condition setting unit 304 can be highlighted different from the display of other detection results.

  The measurement result graph display unit 306 graphs and displays the measurement results of strain and temperature displayed by the measurement result display unit 305.

The operation of the measuring apparatus using the FBG sensor having the above configuration will be described.
FIG. 6A shows a state diagram in which the FBG sensor 2 of the optical fiber 1 is arranged in a free state without contacting the object 3 to be measured, and a detection waveform at that time. The graph of FIG. 6B shows the detection wavelength on the horizontal axis and the reflected light output of the FBG sensor on the vertical axis. The waveform 24 is detected with the steady state before the change is applied. By pulling the DUT 3 in the left-right direction, the DUT 3 can be distorted. The FBG sensor 2 in a state where this distortion has occurred detects the waveform 25. It can be seen that the steady state waveform 24 and the distorted state waveform 25 do not change and there is no wavelength change. That is, when the FBG sensor 2 is in a free state, the distortion of the DUT 3 is not transmitted, and the diffraction grating of the FBG sensor 2 does not change.

  FIG. 7A and FIG. 7B are diagrams showing waveform changes when the temperature of the device under test 3 rises in the state of FIG. 6A. In the steady state, a waveform 27 as shown in FIG. 7B is detected. As shown in FIG. 7A, when a temperature rise occurs in the DUT 3, the temperature change is transmitted to the FBG sensor 2 and a waveform 28 as shown in FIG. 7B is detected. Compared to the steady-state waveform 27, when the temperature rises, the waveform is shifted to the longer wavelength side. That is, even if the FBG sensor 2 is free, the refractive index at the diffraction grating portion of the FBG sensor 2 changes due to the increase in the ambient temperature, and the wavelength moves to the longer wavelength side. It should be noted that when the temperature drops and changes to a low temperature, it is clear that the detected waveform moves to the short wavelength side, although not shown.

  FIG. 8A is a state diagram in which the FBG sensor 2 of the optical fiber 1 is completely fixed to the object to be measured 3 with an adhesive 24 or the like, and FIG. 8B shows a detection waveform at that time. In the state of FIG. 8A, the DUT 3 is pulled in the left-right direction under the same conditions as in FIG. The steady state is a waveform 28, and a waveform 29 is detected in a state where distortion has occurred. That is, since the FBG sensor 2 is distorted similarly to the object 3 to be measured, the diffraction grating interval of the FBG sensor 3 is changed, and the waveform of the reflected light is shifted to the long wavelength side. This change amount 30 corresponds to the amount of distortion generated in the DUT 3. If the distortion acts on the compression side, the detection waveform moves to the short wavelength side although not shown.

  FIG. 9A shows a state in which the FBG sensor 2 of the optical fiber 1 is completely fixed to the object to be measured 3 with an adhesive 24 or the like, similarly to FIG. 8A. FIG. 9B shows a waveform change when the temperature of the device under test 3 rises in this state. As in the case of FIG. 8B, the waveform 31 is detected in the steady state. When a temperature rise occurs in the DUT 3, a temperature change is transmitted to the FBG sensor 2, and a waveform 32 is detected. Compared with the steady-state waveform 31, a change amount 33 is calculated. The amount of change 33 detects the temperature change of the DUT 3 if the distortion caused by the heat of the adhesive 24 is ignored.

  FIG. 10A and FIG. 10B explain waveform changes due to the fixed method in the present invention. 10A, as described in FIGS. 1 and 2, a part 2a of the FBG sensor 2 of the optical fiber 1 is fixed to the object 3 to be measured by the FBG sensor fixing member 4, and the remaining part of the FBG sensor 2b is A state in which the optical fiber fixing member 5 is fixed in a free state so as not to depend on the distortion of the DUT 3 is shown. In this state, the DUT 3 is pulled in the left-right direction under the same conditions as described in FIGS. 6A and 8A. In FIG. 10B, the steady state is the waveform 34, and the waveform 35 is detected in a state where distortion has occurred. In the waveform 35, focusing on a range 36 a corresponding to the range 2 a fixed to the DUT 3 and a range 36 b corresponding to the range 2 b fixed in a free state, the waveform has two peaks. This is because the initial distortion is generated by fixing the range 2a to the object 3 to be measured, and the diffraction grating interval slightly changes between the range 2a and the range 2b, so that the two regions separated by the fixed boundary are separated. Each peak is considered to occur. Since the measurement object 3 is distorted by the pulling, in the range 2a, as described with reference to FIG. 8B, the wavelength changes to the long wavelength side, and the change amount 37 is calculated. On the other hand, in the range 2b, as described with reference to FIG. 6B, since there is no influence of distortion, there is no wavelength change and the change amount 38 is zero.

  11A and 11B are diagrams for obtaining a wavelength change from the peak position of the waveform when the object to be measured 3 rises in temperature under the same conditions as in FIGS. 7A and 7B, FIGS. 9A and 9B. The FBG sensor 2 is fixed to the object to be measured 3 as shown in FIG. 11A. As shown in FIG. 11B, the waveform detected in this state is the waveform 39 in the steady state, and changes to the waveform 40 as the temperature rises. In the range 2a of the FBG sensor 2, as described with reference to FIG. 9B, since the refractive index changes due to the temperature rise in the fixed FBG sensor 2a, the wavelength changes to the long wavelength side, and the change amount 41 is calculated. In the range 2b, as described with reference to FIG. 6B, the refractive index changes in the FBG sensor 2b as the temperature of the object to be measured 3 rises as it is in a free state. Therefore, the wavelength change 42 is calculated.

  FIG. 11C and FIG. 11D are diagrams for obtaining the wavelength change from the waveform shape with the temperature rise. The FBG sensor 2 is fixed to the object to be measured 3 as shown in FIG. 11C as in the case of FIG. 11A. Similarly to FIG. 11B, the steady state is a waveform 39 as shown in FIG. 11D, and changes to a waveform 40 as the temperature rises. In the range 2a of the FBG sensor 2, as the temperature rises, the wavelength changes to the longer wavelength side, and the change amount 41 is calculated. Although the range 2b of the FBG sensor 2 is also free, the wavelength change 42 occurs as the temperature of the device under test 3 rises. A threshold value 52 is set for the waveform 39 and the waveform 40. A wavelength width 53 is obtained from the intersection of the threshold value 52 and the waveform 39. Next, the wavelength width 54 is obtained from the intersection of the threshold value 52 and the waveform 40. The difference 54a between the wavelength width 54 on the long wavelength side and the wavelength width 53 is the same as the wavelength change 42 described above. Further, the difference 54b is the same as the wavelength change 41. Therefore, by obtaining the difference 54b, it is possible to obtain the temperature change generated in the DUT 3 from the wavelength. This method does not calculate the wavelength change from the peak position of the waveform, and can handle even when there are a plurality of peak positions or when the peak position is unknown, thereby enabling more stable and highly sensitive measurement.

  That is, the change in wavelength of the FBG sensor 2a fixed to the object to be measured 3 is caused by distortion, and the change in wavelength of the FBG sensor 2b not fixed to the object to be measured 3 is caused by temperature. For this reason, the FBG sensor 2b can perform temperature measurement and strain measurement using the difference between the FBG sensor 2a and the FBG sensor 2b. The amount of strain and temperature can be calculated by multiplying the changed wavelength by a coefficient. When the wavelength band of 1.5 μm is used, the coefficient due to temperature is approximately 10 pm / ° C., and the coefficient due to strain is approximately 1.2 pm / με. If the wavelength band to be used is different from 1.5 μm, the coefficient may be multiplied.

  FIG. 12 illustrates a measurement flow of the measurement apparatus using the FBG sensor according to the present invention. First, the FBG sensor is set on the object to be measured by the method described above (S1201). Next, a detection condition is set on the display screen 300 of the display means 18 (S1202), and measurement is started (S1203). Illumination light is incident on the optical fiber 1 by the illumination light source 9 to irradiate the FBG sensor 2 (S1204), and reflected light from the FBG sensor 2 is detected by the photoelectric converter 11 (S1205). The reflected light signal detected by the photoelectric converter 11 is amplified by the A / D converter 12, converted into a digital signal, sent to the calculation unit 7, and the wavelength in the fixed FBG range is fixed by the fixed unit wavelength calculator 13. Calculated (S1206), the wavelength in the free FBG range is calculated by the free portion wavelength calculator 14 (S1207), and the distortion amount is calculated from the wavelength change amount in the fixed FBG range calculated by the fixed portion wavelength calculator 13. The temperature is calculated (S1208), and the temperature is calculated from the amount of wavelength change in the free FBG range calculated by the free unit wavelength calculator 14 (S1209). These calculated results are displayed on the display screen 300 of the display means 18 (S1210), the calculated results are output externally as necessary (S1211), and the measurement is terminated.

A second embodiment of the present invention will be described with reference to FIGS. 13A and 13B. In this embodiment, as shown in FIG. 13A, the area 2 b as well as the area 2 a of the FBG sensor 2 is different from the embodiment 1 in that the area 2 b is fixed to the DUT 3. The measurement object 3 is fixed in the region 2a of the FBG sensor 2 of the optical fiber 1 in the same manner as in FIG. The region 2b has the same thermal expansion coefficient as that of the optical fiber 1 and is fixed to the object to be measured 3 with an adhesive 43 having the same hardness. The distortion in the DUT 3 and the waveform change in the region 2b due to the temperature change are the same as those shown in FIGS. 6B and 7B. According to this method, since the FBG sensor is not exposed to the outside, there is an effect that the FBG sensor can be protected. In this case, even if the physical properties of the adhesive are not the same, it is possible to measure the desired temperature by calculating the wavelength change due to temperature rise from the database by creating a database by preliminarily determining the relationship between the temperature and the elongation of the adhesive It becomes.

FIG. 14 illustrates a third embodiment.
In the present embodiment, the object to be measured 46 is formed with grooves 47 and 48 so that the FBG sensor 44 and the FBG sensor 45 of the optical fiber 1 do not come into contact with each other. The FBG sensor 44 is an area for measuring the strain and temperature of the object to be measured 46 corresponding to the area 2a described in the first embodiment, so that the adhesive 49 and the adhesive 50 do not bend the object to be measured. Bonded in a state of applying a certain tension. The FBG sensor 45 is an area for measuring the temperature of the object to be measured 46 corresponding to the area 2 b described in the first embodiment, and is bonded in a free state by the adhesive 50 and the adhesive 51. According to this method, the strain and temperature can be measured with the FBG sensor 44, and the temperature can be measured with the FBG sensor 45. Therefore, the same effects as in the case of the first embodiment can be obtained. According to this method, since it can fix without applying an adhesive agent on the upper part of an FBG sensor, there also exists an effect which can exclude an influence of an adhesive agent.

Next, an application example of the FBG sensor according to the present invention will be described.
In this embodiment, a case where the present invention is applied to a generator will be described.
FIG. 15 is a schematic diagram of a generator. The turbine 100 is connected to the rotor 102 of the generator 101. The stator 103 is disposed to face the rotor 102. The stator measurement FBG sensor 104 described in the present invention is fixed to the stator 103. Similarly, a rotor measurement FBG sensor 105 is fixed to the rotor 102, and an end thereof is connected to a rotary joint 106 installed on a rotation shaft. The rotary joint 106 prevents the rotor measurement FBG sensor 105 from being twisted by the rotation of the rotor 102. An optical fiber 107 is connected to the outside of the rotary joint 106, and is connected to the FBG sensor measurement unit 6, the calculation unit 7, and the control unit 8 of the optical FBG fiber detector together with the stator measurement FBG fiber 104 laid on the stator 103. The configuration and operation of the FBG sensor measurement unit 6, the calculation unit 7, and the control unit 8 are the same as those described in the first embodiment, and the strain amount and temperature are calculated according to the flow described in FIG. . The FBG sensors installed on the stator measuring FBG sensor 104 and the rotor measuring FBG sensor 105 are fixed by the fixing method described in any one of the first to third embodiments of the present invention. If a plurality of FBG sensors described in FIG. 3 are used, measurement at multiple points of the rotor 102 and the stator 103 is possible.

  In this configuration, it is possible to measure distortion and temperature inside the generator during operation of the generator or during steady operation. Furthermore, since the measurement is performed using an optical fiber, there is no influence of the magnetic field, and the performance of the generator is not deteriorated.

Next, an embodiment when applied to the entire facility such as nuclear power generation will be described.
FIG. 16 is a schematic diagram of a nuclear power generation facility. The turbine 160 is rotated by the nuclear reactor 150 and power can be generated by the generator 161 connected to the turbine 160. The nuclear reactor 150, the turbine 160, and the cooling device 151 are connected by a cooling pipe 152, respectively. The cooling pipe measuring FBG sensor 153 is wound around the cooling pipe 152, and the FBG sensor unit is fixed by the fixing method described in any one of the first to third embodiments of the present invention. The facility measurement FBG sensor 154 extends around the building of the nuclear reactor 150 and similarly fixes the FBG sensor section. Each FBG sensor is connected to the FBG sensor measurement unit 6, the calculation unit 7, and the control unit 8 of the optical FBG fiber detection device. The configuration and operation of the FBG sensor measurement unit 6, the calculation unit 7, and the control unit 8 are the same as those described in the first embodiment, and the strain amount and temperature are calculated according to the flow described in FIG. . As in FIG. 15, if the cooling pipe measuring FBG sensor 153 and the equipment measuring FBG sensor 154 are provided with a plurality of FBG sensors, simultaneous observation at multiple points is possible.

  In this configuration, it is possible to measure the health monitor such as the deformation of the building of the reactor 150 and the abnormal temperature rise, the abnormal temperature rise and abnormal distortion of the cooling pipe 152, and the effect of enabling the safety monitoring of the entire facility can be achieved.

DESCRIPTION OF SYMBOLS 1 ... Optical fiber 2 ... FBG sensor 2a ... Fixed FBG sensor 2b ... Free FBG sensor 3 ... DUT 4 ... FBG sensor fixing member 5 ... Optical fiber fixing Member 6 ... FBG waveform measuring device 7 ... arithmetic unit 8 ... control unit 9 ... light source 10 ... optical circulator 11 ... photoelectric converter 12 ... A / D converter 13 .. Fixed part wavelength calculator 14... Free part wavelength calculator 15... Strain amount calculator 16... Temperature calculator 17... Measurement condition input means 18. DESCRIPTION OF SYMBOLS 101 ... Generator 102 ... Rotor 103 ... Stator 104 ... Stator measurement FBG sensor 105 ... Rotor measurement FBG sensor 106 ... Rotary joint 150 Reactor 151 ... Cooling device 1 2 ... cooling pipes 153 ... cooling pipe measured FBG sensor 154 ... facilities measuring FBG sensor for.

Claims (12)

A part of the optical fiber having a diffraction grating formed in the core is fixed in a state depending on the distortion of the object to be measured,
The other part of the optical fiber having a diffraction grating formed on the core is fixed in a state that does not depend on the distortion of the object to be measured,
Using the signal detected from the portion fixed in a state depending on the strain of the object to be measured of the optical fiber and the signal detected from the portion fixed in a state not dependent on the strain of the object to be measured in the optical fiber A measuring method using an FBG sensor, characterized by measuring strain and temperature of an object to be measured.   The signal detected from the fixed portion of the optical fiber depending on the distortion of the object to be measured relates to the wavelength of the reflected light from the diffraction grating of the fixed portion depending on the distortion of the optical fiber to be measured. A signal detected from a portion fixed in a state not dependent on distortion of the object to be measured in the optical fiber is reflected from a diffraction grating in a portion fixed in a state independent of distortion of the object to be measured in the optical fiber. The measurement method using an FBG sensor according to claim 1, wherein the signal is a signal related to a wavelength of light.   2. The method according to claim 1, wherein fixing the part of the optical fiber in a state depending on strain of the object to be measured is performed by fixing a part of the optical fiber to the object to be measured with an adhesive. A measurement method using the FBG sensor according to 2.   Fixing a part of the optical fiber in a state depending on the strain of the object to be measured, and bonding both end parts of the part of the optical fiber to the object to be measured in a state where the part of the optical fiber is not slack The measurement method using the FBG sensor according to claim 1, wherein the measurement method is performed by fixing with an FBG sensor.   Fixing the other part of the optical fiber in a state that does not depend on the strain of the object to be measured, fixing the end of the other part of the optical fiber to the object to be measured, and the remaining part of the other part The measurement method using the FBG sensor according to claim 1, wherein the measurement is performed by making a portion free with respect to the object to be measured.   The other part of the optical fiber is fixed without depending on the strain of the object to be measured. The other part of the optical fiber has the same thermal expansion coefficient as the optical fiber and has the same hardness as the optical fiber. The measurement method using the FBG sensor according to claim 1, wherein the measurement is performed by fixing the object to be measured with an adhesive. An optical fiber in which a diffraction grating is formed on a core in which a part is fixed in a state depending on the distortion of the object to be measured and another part is fixed in a state not depending on the distortion of the object to be measured;
Light source means for emitting light;
Of the light emitted from the light source means, the light is incident on the optical fiber, is reflected by a diffraction grating of a portion fixed in a state depending on the distortion of the object to be measured, and is reflected from the optical fiber. Light detecting means for detecting light and reflected light emitted from the optical fiber by being reflected by a diffraction grating of a portion fixed in a state not depending on distortion of the measurement object of the optical fiber;
Arithmetic means for processing the signal obtained by detecting reflected light with the light detection means to calculate the strain and temperature of the object to be measured;
An measuring device using an FBG sensor, comprising: output means for outputting information on strain and temperature of the object to be measured calculated by the computing means.   8. The FBG according to claim 7, wherein the calculation means calculates strain and temperature of the object to be measured using information on the wavelength of reflected light emitted from the optical fiber detected by the light detection means. Measuring device using a sensor. The part of the optical fiber fixed in a state depending on the strain of the object to be measured is fixed to the object to be measured with an adhesive. 8. A measuring apparatus using the FBG sensor according to 8.   The part of the optical fiber fixed in a state depending on the strain of the object to be measured is bonded to both parts of the part of the optical fiber with no slack in the part of the optical fiber. The measuring device using the FBG sensor according to claim 7 or 8, wherein the measuring device is fixed with an agent. The other part of the optical fiber fixed in a state not dependent on the distortion of the object to be measured is a part of the other part fixed to the object to be measured with an adhesive, and the remaining part of the other part is fixed. 9. The measuring device using the FBG sensor according to claim 7 or 8, wherein the measuring device is in a free state with respect to the object to be measured.   The other part of the optical fiber fixed in a state not dependent on the strain of the object to be measured has the same thermal expansion coefficient as the optical fiber and the same hardness as the optical fiber. The measurement method using the FBG sensor according to claim 7 or 8, wherein the measurement object is fixed to the object to be measured.

Images