JP7192626B2 - Temperature measuring device, temperature measuring method and temperature measuring program - Google Patents

Description

The present application relates to a temperature measuring device, a temperature measuring method, and a temperature measuring program.

Optical fiber temperature measurement using backward Raman scattered light has been developed as a method for measuring temperature. In this temperature measurement, the temperature is calculated from the ratio of the Stokes and anti-Stokes components backscattered in the optical fiber. However, when the optical fiber degrades, the temperature measurement may become erroneous.

Therefore, attempts have been made to estimate and correct the amount of attenuation due to deterioration of the backward Raman scattered light. For example, a method of estimating attenuation from data of a reference thermometer has been disclosed (see Patent Document 1, for example). Further, a method of estimating the attenuation of back Raman scattering is disclosed by examining the wavelength dependence of attenuation from the intensity of back Rayleigh scattered light using a plurality of light sources with different wavelengths (see, for example, Patent Document 2). .

Japanese Unexamined Patent Application Publication No. 2016-3905 JP 2017-9509 A

However, even with a reference thermometer, it is difficult to estimate nonlinear attenuation with optical fiber distance. If a plurality of light sources are used, corresponding light receivers and the like are also required, which increases the cost.

In one aspect, an object of the present invention is to provide a temperature measuring device, a temperature measuring method, and a temperature measuring program capable of estimating attenuation caused by deterioration of an optical fiber at low cost.

In one aspect, the temperature measurement device measures the time-series data of the amount of backscattered light from the optical fiber at the sampling positions of the optical fiber arranged along the predetermined path after the first time point. A fitting unit that extracts low-frequency components of fluctuations in the amount of backscattered light with respect to time by performing fitting for a time range of; a correction unit that corrects the amount of backscattered light using the results of the fitting unit; a temperature measurement unit that measures the temperature of the sampling position using the amount of backscattered light corrected by the correction unit.

Attenuation due to optical fiber degradation can be estimated at low cost.

1(a) is a schematic diagram showing the overall configuration of the temperature distribution measuring device 0, and FIG. 1(b) is a block diagram for explaining the hardware configuration of a control section. FIG. It is a figure showing the component of backscattered light. (a) is a diagram illustrating the relationship between the elapsed time after light pulse emission by a laser and the light intensity of a Stokes component and an anti-Stokes component, and (b) is a temperature calculated using the detection result of (a). be. FIG. 5 is a diagram illustrating the amount of backscattered light when deterioration occurs in a temperature measurement target section of an optical fiber and loss occurs. FIG. 4 is a diagram illustrating a wound portion provided outside a temperature measurement target section of an optical fiber; (a) and (b) are diagrams illustrating an outline of a technique for extracting a portion related to deterioration of the amount of backscattered light. (a) to (c) are diagrams for explaining an example of calculating the amount of attenuation due to deterioration. FIG. 5 is a diagram illustrating a flowchart executed by a control unit; (a) to (c) are diagrams for explaining a simulation of attenuation and correction due to deterioration. (a) to (c) are diagrams for explaining a simulation of attenuation and correction due to deterioration. It is an example of data of the amount of backscattered light.

Hereinafter, embodiments will be described with reference to the drawings.

(embodiment)
FIG. 1(a) is a schematic diagram showing the overall configuration of the temperature measuring device 100. FIG. As illustrated in FIG. 1A, the temperature measuring device 100 includes a measuring instrument 10, a controller 20, an optical fiber 30, and the like. The measuring instrument 10 includes a laser 11, a beam splitter 12, an optical switch 13, a filter 14, a plurality of detectors 15a and 15b, and the like. The control unit 20 includes an instruction unit 21, a temperature measurement unit 22, a storage unit 23, a deterioration determination unit 24, a model creation unit 25, a fitting unit 26, a correction unit 27, and the like.

FIG. 1B is a block diagram for explaining the hardware configuration of the controller 20. As shown in FIG. As illustrated in FIG. 1B, the control unit 20 includes a CPU 101, a RAM 102, a storage device 103, an interface 104, and the like. Each of these devices is connected by a bus or the like. A CPU (Central Processing Unit) 101 is a central processing unit. CPU 101 includes one or more cores. A RAM (Random Access Memory) 102 is a volatile memory that temporarily stores programs executed by the CPU 101 and data processed by the CPU 101 . The storage device 103 is a non-volatile storage device. As the storage device 103, for example, a ROM (Read Only Memory), a solid state drive (SSD) such as a flash memory, a hard disk driven by a hard disk drive, or the like can be used. By executing the temperature measurement program stored in the storage device 103 by the CPU 101, the control unit 20 is instructed by an instruction unit 21, a temperature measurement unit 22, a storage unit 23, a deterioration determination unit 24, a model generation unit 25, a fitting unit 26, A correction unit 27 and the like are realized. Note that each part of the control unit 20 may be hardware such as a dedicated circuit.

The laser 11 is a light source such as a semiconductor laser, and emits laser light within a predetermined wavelength range according to instructions from the instruction unit 21 . In this embodiment, the laser 11 emits light pulses (laser pulses) at predetermined time intervals. The beam splitter 12 causes the optical pulse emitted by the laser 11 to enter the optical switch 13 . The optical switch 13 is a switch that switches the emission destination (channel) of the incident optical pulse. In the double-ended method, the optical switch 13 alternately injects light pulses into the first end and the second end of the optical fiber 30 at regular intervals according to instructions from the instruction unit 21 . In the single-ended system, the optical switch 13 causes the optical pulse to enter either the first end or the second end of the optical fiber 30 according to instructions from the instruction section 21 . The optical fiber 30 is arranged along a predetermined path for temperature measurement.

A light pulse incident on the optical fiber 30 propagates through the optical fiber 30 . The light pulse propagates through the optical fiber 30 while gradually attenuating while generating forward scattered light traveling in the propagation direction and backscattered light (return light) traveling in the return direction. The backscattered light passes through the optical switch 13 and reenters the beam splitter 12 . Backscattered light incident on the beam splitter 12 is emitted to the filter 14 . The filter 14 is a WDM coupler or the like, and extracts a long wavelength component (Stokes component, which will be described later) and a short wavelength component (an anti-Stokes component, which will be described later) from the backscattered light. The detectors 15a and 15b are light receiving elements. The detector 15a converts the received light intensity of the Stokes component into an electric signal at a predetermined cycle and stores the electric signal in the storage unit 23 . Thereby, the storage unit 23 stores the time-series data of the light amount of the Stokes component. The detector 15b converts the received light intensity of the anti-Stokes component into an electric signal at the same period as the detector 15a, and stores the electric signal in the storage unit 23. FIG. Thereby, the storage unit 23 stores the time-series data of the light amount of the anti-Stokes component. The temperature measurement unit 22 measures the temperature at each sampling position in the temperature measurement target range of the optical fiber 30 using the light intensity of the Stokes component and the light intensity of the anti-Stokes component stored in the storage unit 23, thereby measuring the temperature of the optical fiber. The temperature distribution in the stretching direction of No. 30 is measured.

The details of the temperature distribution measurement will be described below. FIG. 2 is a diagram showing components of backscattered light. As illustrated in FIG. 2, the backscattered light is roughly classified into three types. These three types of light are, in descending order of light intensity and closeness to the incident light wavelength, Rayleigh scattered light used for OTDR (optical pulse tester), Brillouin scattered light used for strain measurement, temperature measurement, etc. is the Raman scattered light used for Raman scattered light is generated by interference between light and lattice vibrations in the optical fiber 30 that change according to temperature. Constructive interference produces short wavelength components, called anti-Stokes components, and destructive interference produces long wavelength components, called Stokes components.

FIG. 3A is a diagram illustrating the relationship between the elapsed time after the laser 11 emits a light pulse and the light intensity of the Stokes component and the anti-Stokes component. The elapsed time corresponds to the propagation distance in the optical fiber 30 (position in the optical fiber 30). As illustrated in FIG. 3(a), the light intensity of both the Stokes component and the anti-Stokes component decrease with time. This is due to the light pulse propagating through the optical fiber 30 gradually attenuating while generating forward scattered light and back scattered light.

As exemplified in FIG. 3A, the light intensity of the anti-Stokes component is stronger at the high temperature position in the optical fiber 30 than the Stokes component, and is higher at the low temperature position than the Stokes component. become weak. Therefore, the temperature at each position in the optical fiber 30 can be detected by detecting both components with the detectors 15a and 15b and utilizing the characteristic difference between the two components. In addition, in FIG. 3A, the region showing the maximum is a relatively high temperature region. Also, the region showing the minimum is a region of relatively low temperature.

In the present embodiment, the temperature measuring unit 22 obtains the time-series data of the light intensity of the Stokes component and the light intensity of the anti-Stokes component stored in the storage unit 23 from each sampling position ( Measure the temperature of each compartment). That is, the temperature measurement unit 22 measures the temperature distribution of the temperature measurement target section in the extending direction of the optical fiber 30 . Since the characteristic difference between both components is used, the temperature can be measured with high accuracy even if the light intensity of both components is attenuated according to the distance. FIG. 3(b) shows temperatures calculated using the detection results of FIG. 3(a). The horizontal axis of FIG. 3B is the position within the optical fiber 30 calculated based on the elapsed time. By detecting the Stokes component and the anti-Stokes component as illustrated in FIG. 3B, the temperature at each sampling position in the temperature measurement target section of the optical fiber 30 can be measured.

By repeating the same temperature measurement each time the laser 11 outputs an optical pulse, the temperature measurement unit 22 can repeat the measurement of the temperature distribution in the temperature measurement target section of the optical fiber 30 at the output period of the optical pulse. . Thereby, the temperature measurement unit 22 can acquire the change over time of the temperature distribution in the temperature measurement target section.

However, over time, optical fiber 30 may degrade. For example, optical fiber 30 may degrade due to microbending, absorption of specific wavelengths of light by water or hydrogen in the glass, radiation-induced defects, dopant diffusion due to high temperatures, and the like. When the optical fiber 30 deteriorates, loss occurs and the attenuation width of the amount of backscattered light tends to increase.

FIG. 4 is a diagram illustrating the amount of backscattered light when deterioration occurs in the temperature measurement target section of the optical fiber 30 and loss occurs. As illustrated in FIG. 4, when loss occurs, the attenuation width of the amount of backscattered light increases at each sampling position of the optical fiber 30 . In optical fiber temperature measurement using back-Raman scattered light, attenuation of incident light and attenuation of returned light affect the amount of back-scattered light measured. In the method of calculating the temperature from the ratio of the Stokes component and the anti-Stokes component, which are two components of the backward Raman scattered light, if the attenuation ratio of the Stokes component and the anti-Stokes component due to deterioration are different, the temperature cannot be measured. error occurs.

Therefore, in the present embodiment, attenuation of the amount of backscattered light caused by deterioration of the optical fiber 30 is estimated, and the amount of backscattered light is corrected based on the estimated attenuation.

In order to estimate the attenuation of the amount of backscattered light due to deterioration of the optical fiber 30, it is preferable to first confirm that the optical fiber 30 has deteriorated. Therefore, the deterioration determining unit 24 determines whether or not the optical fiber 30 has deteriorated.

If the optical fiber 30 is not degraded, the ratio (or logarithmic difference) between the light amount of the Stokes component and the light amount of the anti-Stokes component will approximately match at two different sampling positions at the same temperature. Therefore, in the present embodiment, in the optical fiber 30, it is determined whether deterioration has occurred in the temperature measurement target section with reference to the outside of the temperature measurement target section. In order to use the outside of the temperature measurement target section as a reference, the winding portion is provided outside the temperature measurement target section.

FIG. 5 is a diagram illustrating a wound portion provided outside the temperature measurement target section of the optical fiber 30. As shown in FIG. As illustrated in FIG. 5 , a first wound portion 31 is provided between the first end of the optical fiber 30 and the temperature measurement target section 33 . A second wound portion 32 is provided between the second end of the optical fiber 30 and the temperature measurement target section 33 . The first wound portion 31 and the second wound portion 32 are wound at the same location so as to obtain the same temperature distribution. In this configuration, the first winding 31 and the second winding 32 are assumed to have the same temperature. Therefore, if attenuation due to deterioration does not occur in the wound portion, the ratio (or difference in logarithms) between the amount of light of the Stokes component and the amount of light of the anti-Stokes component will substantially match. Based on this condition, it can be determined whether deterioration has occurred in the temperature measurement target section 33 of the optical fiber 30 .

For example, the logarithm of the light amount of the Stokes component of the first wound portion 31 is assumed to be ST1, and the logarithm of the light amount of the anti-Stokes component of the first wound portion is assumed to be AS1. The logarithm of the light amount of the Stokes component of the second wound portion 32 is assumed to be ST2, and the logarithm of the light amount of the anti-Stokes component of the second wound portion 32 is assumed to be AS2. When the light enters the first end of the optical fiber 30, Δ(ST-AS) is defined as (ST1-AS1)-(ST2-AS2). If Δ(ST-AS) increases, the ratio of the Stokes component and the anti-Stokes component will deviate between the first wound portion 31 and the second wound portion 32, and the temperature measurement of the optical fiber 30 will be affected. Degradation is progressing in the target section. Therefore, if Δ(ST−AS) exceeds the threshold value α, the deterioration determination unit 24 determines that deterioration has occurred in the temperature measurement target section of the optical fiber 30 . The threshold α may be, for example, 3σ which is three times the standard deviation σ of Δ(ST-AS) when the optical fiber 30 is not degraded.

After it is determined that the optical fiber 30 has deteriorated, for each sampling position, the portion related to the deterioration of the backscattered light amount caused by the deterioration of the optical fiber 30 is extracted to estimate the attenuation of the backscattered light amount. FIGS. 6(a) and 6(b) are diagrams illustrating an outline of a technique for extracting a portion related to deterioration of the amount of backscattered light in this embodiment. FIG. 6A is a diagram illustrating temporal changes in the amount of backscattered light at predetermined sampling positions in the temperature measurement target section. In the example of FIG. 6A, deterioration occurs in the optical fiber 30 at a certain point. Here, the amount of backscattered light is the sum of a component related to temperature and a component related to deterioration. The frequency of the component related to temperature is different from the frequency of the component related to deterioration. When the environment is constant, the degradation-related component has a sufficiently low frequency compared to the temperature-related component. Therefore, as exemplified in FIG. 6B, by extracting the low-frequency component of the variation of the backscattered light amount with respect to time, it is possible to separate and extract the portion related to the degradation of the backscattered light amount by frequency. If it is possible to estimate the amount of attenuation due to deterioration of the cut and extracted portion, the temperature error can be eliminated by adding the amount of light corresponding to the amount of attenuation to the measured amount of light.

FIGS. 7(a) to 7(c) are diagrams for explaining an example of calculating attenuation due to deterioration. FIG. 7A is a diagram illustrating temporal changes in the amount of backscattered light at predetermined sampling positions in the temperature measurement target section. The model creating unit 25 creates a model before deterioration from the amount of backscattered light in the time interval in which Δ(ST-AS) does not exceed the threshold value α. The model of the Stokes component before degradation is called STM. A model of the anti-Stokes component before degradation is called ASM. Each time a new STM and ASM are created, the STM and ASM are updated with the new STM and ASM. For example, as exemplified in FIG. 7A, the model creation unit 25 averages, for example, a time interval in which the amount of backscattered light is not affected by deterioration with respect to time transition of the amount of backscattered light for each sampling position. data. Thereby, the model creation unit 25 creates STM and ASM for each sampling position.

Next, as exemplified in FIG. 7B, the fitting unit 26 performs fitting on the time-series data of the amount of backscattered light with a fitting function having an attenuation frequency caused by deterioration, and obtains the latest Find the fitting value. For example, the fitting unit 26 performs fitting with a fitting function having a frequency of attenuation due to deterioration to recent past time-series data of the backscattered light amount, and obtains a fitting value at the current time from the fitting function. Linear regression, curve regression, or the like can be used for fitting. The fitting value of the Stokes component at the current time is called STF, and the fitting value of the anti-Stokes component at the current time is called ASF. The fitting unit 26 obtains STF and ASF for each sampling position.

The correction unit 27 uses the difference between the model and the fitting value as an attenuation estimated value due to deterioration. For example, for the Stokes component, the correction unit 27 estimates (STM-STF) as the amount of attenuation of the amount of light of the Stokes component. Further, the correction unit 27 estimates (ASM-ASF) as the amount of attenuation of the light amount of the anti-Stokes component for the anti-Stokes component. The correction unit 27 creates an attenuation estimated value distribution by obtaining the attenuation estimated value at each sampling position in the temperature measurement target section.

FIG. 7(c) is a diagram illustrating an attenuation estimation distribution. In FIG. 7(c), the solid line represents the estimated attenuation distribution. As illustrated in FIG. 7(c), the attenuation estimated value distribution contains errors due to gradual temperature changes, fitting accuracy, and the like. Therefore, it is preferable to improve the precision of the attenuation estimated value distribution by filtering. The amount of attenuation due to deterioration inevitably increases with the optical fiber distance from the laser 11 because the light travels while being attenuated. In addition, since it is possible to predict what kind of frequency it will be with respect to distance from the nature of deterioration (for example, the distribution that depends on the installation state), filter processing such as a low-pass filter is applied to the obtained attenuation amount estimate distribution. By doing so, it is possible to improve the accuracy. In FIG. 7(c), the dotted line represents the attenuation estimated value distribution after filtering.

The correction unit 27 performs correction by adding the highly accurate attenuation estimated value to the measured backscattered light amount. For example, the correcting unit 27 adds (STM-STF) to the light amount of the Stokes component measured for each sampling position. Further, the correction unit 27 adds (ASM-ASF) for the light of the anti-Stokes component measured for each sampling position. The temperature measurement unit 22 measures the temperature at each sampling position using the light amount of the Stokes component and the light amount of the anti-Stokes component corrected by the correction unit 27 .

If a plurality of sampling positions with the same temperature are provided in the temperature measurement target section, it is possible to further increase the accuracy by calculating the attenuation estimated value using the conditions. Also, if there is a correlation between temperature and deterioration, it is possible to increase the accuracy by calculating the temperature from the corrected amount of backscattered light and recalculating the attenuation estimated value from the temperature information. .

FIG. 8 is a diagram illustrating a flowchart executed by the control unit 20. As shown in FIG. First, the deterioration determining unit 24 acquires time-series data of the amount of backscattered light for a predetermined time range for each sampling position from the storage unit 23 (step S1). Next, the deterioration determining unit 24 extracts the time-series data of the first wound part 31 and the second wound part 32 from the acquired time-series data of the amount of backscattered light, and extracts the latest time Δ(ST-AS) Calculate

Next, the deterioration determining unit 24 determines whether or not Δ(ST-AS) exceeds the threshold value α (step S2). If determined as "No" in step S2, the model creation unit 25 creates model data (STM and ASM) from the time-series data acquired in step S1 (step S3). If there are already created STM and ASM, the model creating unit 25 updates them to the STM and ASM created in step S3. Thereafter, the temperature measurement unit 22 performs temperature measurement for each sampling position using the latest light intensity of the Stokes component and the latest light intensity of the anti-Stokes component (step S4). Then, after a predetermined period of time, the process is executed again from step S1.

If the determination in step S2 is “Yes”, the deterioration determining unit 24 determines that the difference between Δ(ST′−AS′), which is the previous Δ(ST−AS), and the current Δ(ST−AS) is , exceeds the threshold value β (step S5). The threshold β may be, for example, 3σ which is three times the standard deviation σ of Δ(ST'-AS')-Δ(ST-AS) when there is no deterioration. By executing step S5, it becomes possible to determine whether the deterioration of the optical fiber 30 is progressing.

If it is determined as "Yes" in step S5, the fitting unit 26 performs fitting with a fitting function having an attenuation frequency caused by deterioration to the most recent past time-series data of the amount of backscattered light. Find the fitting value. Thereby, the fitting unit 26 creates STF and ASF for each sampling position (step S6).

Next, the correction unit 27 calculates the attenuation estimated value distribution of the Stokes component by calculating the difference between the STM and the STF (STM-STF) for each sampling position. Further, the correction unit 27 calculates the difference between the ASM and the ASF (ASM-ASF) for each sampling position, thereby calculating the attenuation estimated value distribution of the anti-Stokes component (step S7).

Next, the correction unit 27 performs filtering on the attenuation estimated value distribution obtained in step S7 (step S8). The correction unit 27 stores the filtered value of (STM-STF) as a corrected value, and stores the filtered value of (ASM-ASF) as a corrected value. Next, the correction unit 27 corrects the amount of backscattered light at each sampling position using the filtered attenuation estimated value distribution (step S9). For example, the correction unit 27 adds the attenuation amount to the measured backscattered light amount for each sampling position, thereby canceling out the attenuation caused by the deterioration. After that, the temperature measurement unit 22 executes step S4. In this case, the temperature measurement unit 22 uses the corrected amount of backscattered light.

If the determination in step S5 is "No", the correction unit 27 uses the stored correction values of (STM-STF) and (ASM-ASF) to calculate the result of backscattering light measurement for each sampling position. Correct (step S10). After that, the temperature measurement unit 22 executes step S4. In this case, the temperature measurement unit 22 uses the corrected amount of backscattered light.

FIGS. 9(a) to 9(c) and 10(a) to 10(c) are diagrams for explaining simulations of attenuation and correction due to deterioration. As illustrated in FIG. 9A, the temperature is assumed to change periodically with respect to the position of the optical fiber 30 . Furthermore, it is assumed that the temperature distribution obtained from the optical fiber 30 changes with the average temperature remaining unchanged. Further, as illustrated in FIG. 9(b), it is assumed that at each sampling position, deterioration starts at a certain time after the start of measurement, and the amount of backscattered light attenuates. Note that the example of FIG. 9B shows the amount of backscattered light at a position 25 m from the first end of the optical fiber 30 . The model creating unit 25 creates STM and ASM using the amount of backscattered light in the time interval where there is no degradation, as illustrated in FIG. 9(c).

As exemplified in FIG. 10(a), the fitting unit 26 performs fitting with a fitting function having an attenuation frequency due to deterioration to the most recent past data of the amount of backscattered light to obtain fitting data at the current time. . The correction unit 27 corrected the measured temperature distribution using the attenuation estimated value distribution, as illustrated in FIGS. 10(b) and 10(c). As a result, the temperature error was improved compared to before correction.

FIG. 11 is an example of backscattered light amount data. The amount of backscattered light is measured at certain time intervals for each optical fiber position. Two types of backscattered light amount data, a Stokes component and an anti-Stokes component, can be obtained at the same time, and backscattered light amount data of a plurality of loops can be measured by switching channels depending on the laying of optical fibers.

According to this embodiment, for sampling positions of the optical fiber 30 arranged along a predetermined path, time-series data of the amount of backscattered light from the optical fiber 30 is obtained at a predetermined time after a predetermined point in time. A range fitting is performed. As a result, low-frequency components resulting from deterioration of the optical fiber 30 are extracted from the time-series data of the amount of backscattered light. With this configuration, the attenuation caused by deterioration of the optical fiber 30 can be estimated at low cost. The result of this fitting is used to correct the amount of backscattered light. As a result, attenuation due to deterioration of the optical fiber 30 can be corrected. Therefore, by measuring the temperature at the sampling position using the corrected amount of backscattered light, it is possible to accurately measure the temperature.

The fitting unit 26 preferably determines the predetermined time range for fitting or the frequency of the fitting function from the distribution of the time spectrum of the backward Raman scattered light before the optical fiber 30 deteriorates. That is, it is recommended to perform fitting in a frequency range lower than the temperature change frequency.

In the present embodiment, the fitting unit 26 determines the time-series data of the amount of backscattered light from the optical fiber at the sampling positions of the optical fiber arranged along the predetermined path. By performing fitting for a later predetermined time range, it functions as an example of a fitting section that extracts low-frequency components of fluctuations in the amount of backscattered light with respect to time. The correction unit 27 functions as an example of a correction unit that corrects the amount of backscattered light using the result of the fitting unit. The temperature measurement unit 22 functions as an example of a temperature measurement unit that measures the temperature of the sampling position using the backscattered light amount corrected by the correction unit. The model creating unit 25 functions as an example of a model creating unit that creates a model for the time-series data from data before the first point in time. The point in time when Δ(ST-AS) exceeds the threshold value α is an example of the first point in time. The latest time of the time-series data of the amount of backscattered light is an example of the second time point. The first wound portion 31 is an example of the first section before the predetermined section of the optical fiber 30 . The second winding portion 32 is an example of a second section after the predetermined section of the optical fiber 30 .

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations can be made within the scope of the gist of the present invention described in the claims. Change is possible.

10 measuring instrument 11 laser 12 beam splitter 13 optical switch 14 filter 15a, 15b detector 20 control unit 21 instruction unit 22 temperature measurement unit 23 storage unit 24 deterioration determination unit 25 model creation unit 26 fitting unit 27 correction unit 30 optical fiber 31 second 1 winding part 32 2nd winding part 33 temperature measurement target section 100 temperature measuring device

Claims (7)

For sampling positions of an optical fiber arranged along a predetermined path, fitting is performed for a predetermined time range after the first time point with respect to the time series data of the amount of backscattered light from the optical fiber, a fitting unit that extracts low-frequency components of variations in the amount of backscattered light with respect to time;
a correction unit that corrects the amount of backscattered light using the result of the fitting unit;
A temperature measurement device, comprising: a temperature measurement unit that measures the temperature of the sampling position using the amount of backscattered light corrected by the correction unit. A model creation unit that creates a model for the time-series data from data prior to the first time point,
The correction unit corrects the amount of backscattered light using a difference between the model and a value of the fitting function obtained by fitting by the fitting unit at a second time point after the first time point. A temperature measuring device according to claim 1. 3. The temperature measuring device according to claim 2, wherein the correcting unit corrects the backscattered light amount using the filtered difference. The optical fiber has a first section and a second section that provide the same temperature distribution before and after the predetermined section,
Let ST1 be the logarithm of the Stokes component of the first interval, AS1 be the logarithm of the anti-Stokes component of the first interval, ST2 be the logarithm of the Stokes component of the second interval, and ST2 be the logarithm of the anti-Stokes component of the second interval. is AS2, the first time point is a time point after (ST1-AS1)-(ST2-AS2) exceeds a predetermined threshold. The temperature measurement device according to item 1. The fitting unit determines the predetermined time range in which the fitting is performed or the frequency of the fitting function from the distribution of the time spectrum of the backward Raman scattered light from the optical fiber before the first time point. A temperature measuring device according to any one of claims 1 to 4. A fitting unit performs fitting for a predetermined time range after a first point in time to the time-series data of the amount of backscattered light from the optical fiber at the sampling positions of the optical fiber arranged along the predetermined path. By performing, extracting the low frequency component of the fluctuation of the backscattered light amount with respect to time,
A correction unit corrects the backscattered light amount using the result of the fitting unit,
A temperature measuring method, wherein a temperature measuring unit measures the temperature of the sampling position using the backscattered light quantity corrected by the correcting unit. to the computer,
For sampling positions of an optical fiber arranged along a predetermined path, fitting is performed for a predetermined time range after the first time point with respect to the time series data of the amount of backscattered light from the optical fiber, a process of extracting low-frequency components of variations in the amount of backscattered light with respect to time;
A process of correcting the amount of backscattered light using the result of the fitting;
and measuring the temperature at the sampling position using the corrected amount of backscattered light.

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