KR20200076311A - distributed optical fiber sensor apparatus and control method thereof - Google Patents

Abstract

The present invention relates to a Rayleigh-Brillouin hybrid distributed optical fiber sensor device for simultaneous measurement of temperature and strain and control method thereof and includes: a first measuring unit for applying a first wavelength variable optical signal to a sensing optical fiber and detecting Rayleigh scattered light which is scattered from the sensing optical fiber; a second measuring unit for detecting Brillouin scattered light which is generated in the sensing optical fiber when a probe light and a pump light are incident through opposite ends of the sensing optical fiber and progress in opposite directions; and the signal processing unit for controlling the operation of the first measurement unit and the second measurement unit, but only when the Rayleigh scattered light measured by the first measurement unit is out of a reference range, operating the second measurement unit for a corresponding abnormality detection section to calculate temperature and strain.

Description

Rayleigh-Brillouin hybrid distributed optical fiber sensor device for simultaneous measurement of temperature and strain and its control method

The present invention relates to a Rayleigh-Brillouin hybrid distributed optical fiber sensor device for simultaneous measurement of temperature and strain and a control method thereof, and specifically, a distributed optical fiber sensor capable of increasing measurement accuracy and measurement speed for each of temperature and strain. It relates to an apparatus and a control method thereof.

Recently, various techniques for measuring physical quantity using optical fibers have been proposed and used.

As an example, when the temperature or the size of a strain (hereinafter referred to as strain) is changed, the wavelength of the optical signal reflected from the optical fiber grid changes. Therefore, it can be used to measure the wavelength change of the light reflected from the optical fiber grating and measure the physical quantity such as external temperature, strain, pressure, etc. from the amount of change in the wavelength.

However, when two physical quantities of temperature and strain are simultaneously applied, the optical fiber grating reacts to both physical quantities at the same time, so it is impossible to know how much the temperature and strain are changed by measuring only the change in the reflected wavelength.

As a way to solve this, Korean Patent Publication No. 1998-0082465 discloses a method for calculating temperature and strain using a pair of optical fiber gratings in which two optical gratings having different outer diameters are connected in series.

However, the disclosed method of measuring temperature/strain has difficulty in manufacturing because a pair of optical fiber lattices having different outer diameters must be manufactured and used for the same base material.

Meanwhile, recently, a method of measuring temperature and strain using Brillouin scattered light scattered from a single mode optical fiber has been variously proposed, such as Korean Patent Publication No. 10-2011-0075679. However, the patent also has a problem in that when the two physical quantities of temperature and strain are simultaneously applied, it is impossible to know how much the temperature and the strain are respectively changed from the scattered light measured by the optical fiber reacting to the two physical quantities simultaneously.

The present invention was devised to solve the above requirements, using a single-mode fiber, but it is possible to increase the measurement accuracy for each of the temperature and strain while increasing the measurement speed while simultaneously measuring the temperature and strain. The objective is to provide a Brillouin hybrid distributed optical fiber sensor device.

In order to achieve the above object, the Rayleigh-Brillouin hybrid distributed optical fiber sensor device for simultaneous measurement of temperature and strain according to the present invention comprises: a sensing optical fiber installed to extend along a measurement path; A first measuring unit for applying a first wavelength-tunable optical signal to the sensing optical fiber and detecting the Rayleigh scattered light scattered from the sensing optical fiber; A second measuring unit configured to detect the Brillouin scattered light generated from the sensing optical fiber by injecting probe light and pump light to opposite ends of the sensing optical fiber in opposite directions; The first measuring unit is controlled to measure the frequency of the Rayleigh scattering signal from the Rayleigh scattered light detected for the sensing optical fiber, and when it is determined that the measured Rayleigh scattering frequency is out of the set reference range, the reference range in the measurement path Determine the section of the sensing optical fiber where the Rayleigh scattering frequency outside is detected as an abnormality detection section, and scan the determined abnormality detection section to control the second measurement unit to detect the Brillouin scattered light, and for the abnormality detection section. Abnormality of the sensing optical fiber by using the raillane scattering signal frequency measured by the first measuring unit and the Brillouin scattering signal frequency information measured from the Brillouin scattering light measured by the second measuring unit for the abnormality detection section. It is provided with a signal processing unit for calculating the temperature and strain for each position of the detection section.

According to an aspect of the present invention, the first measurement unit includes a first light source unit for emitting a first optical signal having a variable wavelength; A first optical coupler for distributing the first optical signal emitted from the first light source unit into a first minute background path and a second minute background path; A second optical coupler for distributing light traveling through the first minute background path into a third minute background path and a fourth minute background path; A first light outputting a first optical signal proceeding in the third minute background path to a first sensing end, and outputting a Rayleigh scattering light traveling in reverse through the first sensing end from the sensing optical fiber to a first sensing end Circulatory system; A frequency monitoring interferometer generating frequency monitoring interference light to monitor a frequency of the first optical signal traveling through the second minute background path; A third optical coupler which combines and outputs the Rayleigh scattered light output from the first detection end of the first optical circulator and the first optical signal traveling through the fourth minute background path; A first optical detector for detecting light output from the third optical coupler and providing the signal to the signal processor; And a second photodetector that detects light output from the frequency monitoring interferometer and provides it to the signal processor.

In addition, the second measurement unit is a second light source unit for controlling the signal processing unit to output light of a modulated frequency; Light generated to generate the probe light and the pump light including a sideband signal using the light output from the second light source unit, and to apply the pump light and the probe light to one end and the other end of the sensing optical fiber, respectively. A modulator; A second optical circulator for outputting the pump light generated by the light modulator through a second sensing stage, and outputting light traveling in the reverse direction from the second sensing stage to a second detection stage; An optical switch configured to connect one end of the sensing optical fiber to any one of the first sensing end and the second sensing end; And a third photodetector that detects the Brillouin scattered light output from the second detection stage and provides it to the signal processing unit. The signal processing unit provides a connection path of the optical switch. Control, measure the frequency of the Rayleigh scattering signal for the sensing optical fiber from the signals output from the first and second photodetectors, and measure the Brillouin scattering signal frequency using the signal received from the third photodetector. .

Preferably, the signal processing unit is a Rayleigh scattering signal frequency (v _R ) calculated using a signal received through the first photodetector and a signal received through the second photodetector, and the third photodetector. Rayleigh corresponding to the difference between the initial value of the Rayleigh scattering signal frequency set for the Brillouin scattering signal frequency (v _B ) calculated using the received signal and the Rayleigh scattering signal frequency measured for the anomaly detection section. From the difference value of the scattering signal frequency (Δv _R ) and the initial value of the set Brillouin scattering signal frequency and the Brillouin scattering signal frequency difference value (Δv _B ) corresponding to the difference between the measured Brillouin scattering signal frequency for the abnormality detection section

)및 변형률 변화값(

)을 산출하고,Change temperature by the formula of

) And strain change value (

),

는 레일레이 신호의 온도에 대한 주파수 감도이고,

는 레일레이 신호의 변형률에 대한 대한 주파수 감도이고,

는 브릴루앙 신호의 온도에 대한 주파수 감도이고,

는 브릴루앙 신호의 변형률에 대한 주파수 감도이다.here,

Is the frequency sensitivity to the temperature of the Rayleigh signal,

Is the frequency sensitivity to the strain of the Rayleigh signal,

Is the frequency sensitivity to the temperature of the Brillouin signal,

Is the frequency sensitivity to the strain of the Brillouin signal.

In addition, in order to achieve the above object, the control method of the distributed optical fiber sensor device according to the present invention includes a sensing optical fiber installed to be extended along a measurement path, and a first optical signal having a variable wavelength to the sensing optical fiber and applying the sensing optical fiber. A first measurement unit for detecting the Rayleigh scattered light scattered from, and a second measurement unit for detecting the Brillouin scattered light generated from the sensing optical fiber by injecting probe light and pump light to opposite ends of the sensing optical fiber in opposite directions. And, in the control method of the distributed optical fiber sensor device having a signal processing unit for calculating the temperature and strain for each position of the sensing optical fiber while controlling the driving of the first and second measuring unit, a. Measuring the frequency of the Rayleigh scattering signal from the Rayleigh scattered light measured for the sensing optical fiber while driving the first measurement unit; I. Determining whether the Rayleigh scattering frequency measured in step A is outside a preset reference range; All. Extracting an abnormality detection section of the sensing optical fiber in which the Rayleigh scattering frequency outside the reference range is detected when it is determined in step B that the Rayleigh scattering frequency is outside the set reference range; la. Scanning the abnormality detection section and driving the second measurement unit to detect the Brillouin scattered light; hemp. Calculating temperature and strain for each position of the abnormality detection section from the Brillouin scattering signal frequency information measured through the step La for the abnormality detection section and the Rayleigh scattering frequency measured for the abnormality detection section; It includes.

According to the Rayleigh-Brillouin hybrid distributed optical fiber sensor device for simultaneous measurement of temperature and strain according to the present invention and a control method thereof, the second measurement unit is operated only for an abnormality detection section while increasing the measurement accuracy for each of the temperature and strain This provides the advantage of improving the measurement speed by performing precise measurements.

1 is a view showing a Rayleigh-Brillouin hybrid distributed optical fiber sensor device for simultaneous measurement of temperature and strain according to the present invention,
2 is a flow chart showing a control process of the distributed optical fiber sensor device according to the present invention.

Hereinafter, a Rayleigh-Brillouin hybrid distributed optical fiber sensor device for simultaneous measurement of temperature and strain according to a preferred embodiment of the present invention and a control method thereof will be described in detail with reference to the accompanying drawings.

1 is a view showing a Rayleigh-Brillouin hybrid distributed optical fiber sensor device for simultaneous measurement of temperature and strain according to the present invention.

Referring to FIG. 1, the distributed optical fiber sensor device 10 according to the present invention includes a sensing optical fiber 30, a first measuring unit 100, a second measuring unit 200, and a signal processing unit 300.

The sensing optical fiber 30 is installed to extend along the measurement path.

It is preferable that the single-mode optical fiber is applied to the sensing optical fiber 30.

The first measurement unit 100 applies a first variable-wavelength optical signal to the sensing optical fiber 30, detects the Rayleigh scattered light scattered from the sensing optical fiber 30, and provides it to the signal processing unit 300.

The first measurement unit 100 is constructed by optical frequency domain reflection (OFDR).

The first measurement unit 100 is a wavelength-tunable laser 110, a first optical coupler 121, a second optical coupler 122, a third optical coupler 123, a first optical circulator 131, a frequency monitoring interferometer 140, a first photodetector (PD1) 151, a second photodetector (PD2) 152, and a polarization controller (PC) 160.

The tunable laser 110 is applied as a first light source unit, and is controlled by the signal processing unit 300 to emit a first optical signal with a variable wavelength.

The first optical coupler 121 distributes and outputs the first optical signal emitted from the wavelength-tunable laser 110 to the first minute background path 121a and the second minute background path 121b.

The second optical coupler 122 distributes the light traveling through the first minute background path 121a to the third minute background path 122a and the fourth minute background path 122b to output the light.

The first optical circulator 131 receives the first optical signal going through the third minute background path 122a through the input terminal and outputs it to the first sensing terminal 131a, and the first sensing terminal from the optical fiber sensor 30 ( The Rayleigh scattered light traveling in reverse through 131a) is output to the first detection end 131b.

The frequency monitoring interferometer 140 generates frequency monitoring interference light and provides it to the second photodetector 152 to monitor the frequency of the first optical signal going through the second minute background path 121b.

The frequency monitoring interferometer 140 includes an interference coupler 141, a reference optical fiber 142, and a delayed optical fiber 143.

The interference coupler 141 distributes and outputs light traveling through the second minute background path 121b to the reference stage 141a and the delay stage 141b, respectively, and reverses the output from the reference stage 141a and the delay stage 141b. Proceed as follows and output the combined monitoring interference light to the second light detector 152 through the combined output terminal 141c.

The reference optical fiber 142 is connected to the reference end 141a of the interference coupler 141.

The end of the reference optical fiber 142 is formed to reflect the incident light and proceed in the reverse direction, for example, a reflection mirror 145 may be installed at the end.

The delayed optical fiber 143 is connected to the delayed end 141b of the interference coupler 141 and has a longer length than the reference optical fiber 142.

The end of the delayed optical fiber 143 is also formed to reflect the incident light and can be reversed, for example, a reflection mirror 146 may be installed at the end.

The polarization controller 160 adjusts the polarization of light traveling through the fourth minute background path 122b of the second optical coupler 122 and outputs it to the third optical coupler 123.

The polarization controller 160 adjusts the polarization state of light traveling through the fourth minute background path 122b to increase the intensity of the interference signal when the Rayleigh scattered light generated from the sensing optical fiber 30 is combined by the third optical coupler 123. Of course, it can be omitted as it is applied to maximize.

The third optical coupler 123 combines the Rayleigh scattered light output from the first detection end 131b of the first optical circulator 131 with the first optical signal traveling through the fourth minute background path 122b to generate the first optical signal. It outputs to the photodetector 151.

The first photodetector 151 detects the light output from the third photocoupler 123 and provides it to the signal processing unit 300.

Unlike this, a polarization separator (not shown) for separating light output from the third optical coupler 123 into vertical polarization and horizontal polarization, respectively, and a signal processing unit that detects vertical polarization and horizontal polarization output separately from the polarization separator, respectively. Of course, it can be constructed with a plurality of light detectors (not shown) provided to the 300.

The second photodetector 152 detects the light output from the frequency monitoring interferometer 140 and provides it to the signal processing unit 300.

The second measurement unit 200 detects the Brillouin scattered light generated from the sensing optical fiber 30 by injecting probe light and pump light to both ends of the sensing optical fiber 30 in opposite directions.

The second measurement unit 200 is constructed by a Brillouin Optical Correlation Domain Analysis (BOCDA).

The second measurement unit 200 includes a second light source unit 210, a light modulation unit 220, a second light circulator 271, an optical switch (OS) 271, and a third light detector (PD3) 273. To be equipped.

The second light source unit 210 controls the signal processing unit 300 to output light of a modulated first frequency.

Here, the first frequency is adjusted by the signal processing unit 300 according to the detection position on the measurement path of the sensing optical fiber 30.

The second light source unit 210 includes a waveform generator 211 that generates a sine wave waveform corresponding to the first frequency determined by the signal processor 300 and a first frequency corresponding to the waveform generated by the waveform generator 211. It is a semiconductor laser (LFB LD) 212 that outputs modulated light.

The semiconductor laser 212 may be a distributed feed-back laser diode (DFB LD).

The light modulator 220 generates pump light for probe light including a sideband signal and light modulated at a first frequency by using the light output from the second light source unit 210, and pump light and probe Light is applied to one end and the other end of the sensing optical fiber 30, respectively.

The optical modulation unit 220 includes a polarization maintenance coupler (PMC) 231, a first modulation unit 240, and a second modulation unit 260.

The polarization maintaining coupler 231 distributes light through the fifth minute background path 231a and the sixth minute background path 231b while maintaining the polarization state of the light output from the second light source unit 210.

The polarization holding coupler 231 is applied to match the polarization state of light traveling through the fifth minute background path 231a and light passing through the sixth minute background path 231b, in which case the maximum induced Brillouin scattering amplification Can get

The first modulator 240 modulates light traveling through the fifth minute background path 231a into probe light.

The first modulator 240 modulates the optical signal of the first frequency to include a sideband signal whose frequency is shifted by an offset frequency according to the signal generated by the bias controller 241 and the microwave generator 242. A single sideband modulator 243 for generating probe light is applied, but is not limited thereto.

The polarization switch (PSW) 251 may periodically change the polarization of the probe light output from the first modulator 240.

For example, the polarization switch 251 may receive a signal from a signal generator (not shown), and rotate the polarization of the probe light once to 0° and the other to 90° according to the received signal. The above-described polarization angles of 0° and 90° are merely exemplary, and in another embodiment, the polarization switch 251 may periodically change the polarization of the probe light to different angles.

When the polarization of the probe light and the pump light coincide with each other, induced Brillouin scattering amplification occurs, but since the polarization of the probe light and the pump light can change with time and space, the polarization of the probe light is changed using the polarization switch 251. The polarization problem can be solved by performing the measurement while performing the measurement and using the average value of the measured values.

The delayed optical fiber 253 can be positioned such that any one of the Brilliant gain peaks on both sides of the sensing optical fiber 30 is positioned at the center of the entire optical path by appropriately adjusting the length.

The optical amplifier 255 amplifies the optical signal.

The optical separator 257 serves to block high-power pump light from going through the sensing optical fiber 30 to the first modulator 240 and an optical isolator may be applied.

The second modulator 260 modulates the first frequency to generate pump light chirped at a second frequency having a preset ratio of light traveling through the sixth minute background path 231b.

The second modulator 260 is a phase modulator 262 that phase-modulates the optical signal received from the polarization-maintaining coupler 231 according to the modulated signal generated by the function generator 261, but is not limited thereto.

The optical amplifier 265 amplifies and outputs pump light.

The second light circulator 271 outputs the pump light generated by the second modulator 260 through the second sensing end 271a, and the second Brillouin scattering light proceeding in reverse from the second sensing end 271a. It outputs to the detection end 271b.

The optical switch 272 is controlled by the signal processing unit 300 so that one end of the sensing optical fiber 30 can be connected to any one of the first sensing end 131a and the second sensing end 271a.

The third photodetector 273 detects the Brillouin scattered light output from the second sensing stage 271b in the reverse direction of the second sensing stage 271a, and outputs it as an electrical signal.

The lock-in amplifier 280 intermittently detects the Brillouin scattered light by synchronizing the signal output from the third photodetector 272 to the function generator 261 of the second modulator 260 to signal the noise-removed signal processing unit ( 300).

The signal processing unit 300 controls the connection path of the optical switch 272 and controls the driving of the first measurement unit 110 and the second measurement unit 200 while controlling the temperature and strain of each sensing optical fiber 30 by location. Calculate.

Preferably, the signal processing unit 300 detects a corresponding abnormality detection section only when an abnormality detection section occurs in the second measurement unit 200 in which the scan speed for the sensing optical fiber 30 is relatively slower than the first measurement unit 110. It is constructed to detect the Brillouin scattered light only for calculating the temperature and strain for the abnormality detection section.

That is, the signal processing unit 300 controls the first measurement unit 100 to measure the frequency of the Rayleigh scattering signal from the Rayleigh scattered light detected for the sensing optical fiber 30, and the reference range in which the measured Rayleigh scattering frequency is set. If it is judged that it is out of range, the section of the sensing optical fiber 30 in which the Rayleigh scattering frequency outside the reference range in the measuring path of the sensing optical fiber 30 is detected is determined as an abnormality detection section.

Here, the reference range may be appropriately applied to correspond to the temperature or the strain of the region of interest as it is outside the normal temperature.

Thereafter, the signal processing unit 300 controls the second measurement unit 200 to detect the Brillouin scattered light by scanning the determined abnormality detection section. Here, the signal processing unit 300 does not scan the entire measuring path of the sensing optical fiber 30, and controls the second measuring unit 200 to detect the abnormality by controlling the second measuring unit 200 so that the correlation point between the probe light and the pump light coincides only in the abnormal detection section. Scan information is extracted only for the section.

In addition, the signal processing unit 300 from the raillane scattering signal frequency measured by the first measurement unit 100 for the abnormality detection section, and the Brillouin scattered light measured by the second measurement unit 200 for the abnormality detection interval The measured Brillouin scattering signal frequency information is used to calculate the temperature and strain for each position of the abnormality detection section of the sensing optical fiber 30.

The control process of the signal processing unit 300 will be described with reference to FIG. 2.

First, the first measurement unit 100 is driven (step 410), and the rail-ray scattering signal frequency v _R is measured from the rail-ray scattered light measured for the sensing optical fiber 30 along the measurement path (step 420). .

That is, the signal processing unit 300 is a wavelength variable laser 110 while the optical switch 272 is controlled so that one end of the sensing optical fiber 30 is connected to the first sensing end 131a of the first optical circulator 131. While varying the wavelength of the first light circulator 131 is scattered with respect to the light transmitted to the sensing optical fiber 30 through the first sensing terminal 131a and the optical switch 272 of the first optical circulator 131 of the first optical circulator 131 Using the signal detected by the first photodetector 151 and the signal detected by the second photodetector 152 for the Rayleigh scattered light proceeding to the first detection terminal 131b, the optical fiber 30 senses the Rayleigh scattering signal frequency. ) Is measured for the entire measuring path.

Here, the frequency of the first optical signal emitted from the wavelength-tunable laser 110 from the signal detected by the second optical detection 152 is grasped, and the first optical detector based on the identified frequency information of the first optical signal ( The Rayleigh scattering frequency (v _R ) for the signal output from 151 is calculated.

Thereafter, it is determined whether the Rayleigh scattering frequency (v _R ) measured in step 420 is out of the set reference range (step 430).

If it is determined in step 430 that the Rayleigh scattering frequency (v _R ) is outside the set reference range, a section of the sensing optical fiber 30 in which the Rayleigh scattering frequency outside the reference range is detected is extracted as an abnormality detection section (step 440 ).

Here, the abnormality detection section refers to a section in which the Rayleigh scattered light out of the reference range is generated among the entire measurement paths of the sensing optical fiber 30.

Thereafter, the second measurement unit 200 is driven to detect the Brillouin scattered light by scanning the extracted abnormal detection section (Step 450), and the Brillouin scattering frequency v _B is measured from the measured Brillouin scattered light (Step 460).

Here, the signal processing unit 300 controls the second measuring unit 200 so that the correlation point between the probe light and the pump light coincides only in the abnormal detection section, and scans only the abnormal detection section to extract detection information for the Brillouin scattered light.

That is, the signal processing unit 300 controls the optical switch 272 such that one end of the sensing optical fiber 30 is connected to the second sensing end 171a of the second optical circulator 271.

In addition, the signal processing unit 300 controls the generation of the pump light and the probe light so that a correlation point occurs in the abnormality detection section, and the second optical circulator 271 senses the optical fiber through the second sensing end 271a and the optical switch 272. Brillouin scattering in the abnormal detection section generated by scattering from the pump light transmitted to (30) and the probe light transmitted to the other end of the sensing optical fiber (30) to the second detection end (271b) of the second optical circulator (271) The Brillouin scattering signal frequency is measured from the signal received through the third photodetector 272 and the lock-in amplifier 280 for the signal.

Finally, the temperature and strain of each position for the abnormality detection section are calculated from the Brillouin scattering signal frequency information measured for the abnormality detection section and the Rayleigh scattering frequency measured for the abnormality detection section (step 470).

Hereinafter, the temperature and strain measurement process of the signal processing unit 300 will be described in more detail.

First, the Rayleigh scattering frequency (v _R ) measured through the first measurement unit 100 may be expressed by Equation 1 below.

In addition, the Brillouin scattering frequency (v _B ) measured through the second measurement unit 100 may be represented by Equation 2 below.

는 초기 레일레이 산란 신호 주파수이고,

초기 브릴루앙 산란 신호 주파수이고,

는 레일레이 신호의 온도에 대한 주파수 감도이고,

는 레일레이 신호의 변형률에 대한 주파수 감도이고,

는 브릴루앙 신호의 온도에 대한 주파수 감도이고,

는 브릴루앙 신호의 변형률에 대한 주파수 감도이고,

는 온도 초기값에 대한 온도 변화량이고,

는 변형률 초기값에 대한 변형률 변화량이다. here,

Is the initial Rayleigh scattering signal frequency,

The initial Brillouin scattering signal frequency,

Is the frequency sensitivity to the temperature of the Rayleigh signal,

Is the frequency sensitivity to the strain of the Rayleigh signal,

Is the frequency sensitivity to the temperature of the Brillouin signal,

Is the frequency sensitivity to the strain of the Brillouin signal,

Is the amount of temperature change relative to the initial temperature,

Is the amount of strain change relative to the initial strain value.

는 초기에 산출되는 레일레이 산란신호 주파수 초기값이고,

는 초기에 산출되는 브릴루앙 산란신호 주파수 초기값이고,

,

,

,

는 실험에 의해 산출되어 알고 있는 값이고 신호처리부(300)에 미리 기록되어 있다.here,

Is the initial value of the Rayleigh scattering signal frequency calculated initially,

Is the initial value of the Brillouin scattering signal frequency calculated initially,

,

,

,

Is a known value calculated by an experiment and is previously recorded in the signal processing unit 300.

In addition, the initial temperature of the temperature corresponding to the initial value of the Rayleigh scattering signal frequency and the initial value of the strain corresponding to the initial value of the Brillouin scattering signal frequency are also recorded in advance in the signal processing unit 300.

As an example, the frequency sensitivity to the temperature of the Rayleigh signal is applied to 1.25 GHz/℃, the frequency sensitivity to the strain of the Rayleigh signal is applied to 0.152 GHz/με, and the frequency sensitivity to the temperature of the Brillouin signal is 1.10. MHz/°C is applied, and the frequency sensitivity to strain of the Brillouin signal is applied to 0.048 MHz/με.

)(

)과 현재 측정된 값의 차이값인 레일레이 신호 주파수 차이값(

)과, 브릴루앙 신호 주파수 차이값(

)을 이용하면 아래의 수학식 3의 관계식을 얻을 수 있다.Therefore, the initial values from Equations 1 and 2 (

)(

) And the difference value of the Rayleigh signal frequency, which is the difference between the current measured value (

) And Brillouin signal frequency difference (

) To obtain the relational expression in Equation 3 below.

은 현재시간에 측정한 v_R에서 초기값(v_R0)를 차감한 값이고,

는 현재시간에 측정한 v_B에서 초기값(v_B0)를 차감한 값이다.here,

Is the value obtained by subtracting the initial value (v _R0 ) from v _R measured at the current time,

Is the value obtained by subtracting the initial value (v _B0 ) from v _B measured at the current time.

In addition, the temperature change and the strain change value from Equation 3 above can be calculated through Equation 4 below.

According to the Rayleigh-Brillouin hybrid distributed optical fiber sensor device for simultaneous measurement of temperature and strain as described above, even when both temperature and strain are applied to the sensing optical fiber, it is possible to separate for each of the temperature and strain, so measurement accuracy can be increased. have.

In addition, it is possible to determine whether there is an abnormality detection section through the first measurement section, and by operating the second measurement section only for the identified abnormality detection section, measure the temperature and strain rate of the abnormality detection section to improve the measurement speed for the abnormality occurrence area. It offers the advantages.

30: sensing optical fiber 100: first measurement unit
200: second measurement unit 300: signal processing unit

Claims (8)

A sensing optical fiber installed to extend along a measurement path;
A first measuring unit for applying a first wavelength-tunable optical signal to the sensing optical fiber and detecting the Rayleigh scattered light scattered from the sensing optical fiber;
A second measuring unit configured to detect the Brillouin scattered light generated from the sensing optical fiber by injecting probe light and pump light to opposite ends of the sensing optical fiber in opposite directions;
The first measuring unit is controlled to measure the frequency of the Rayleigh scattering signal from the Rayleigh scattered light detected for the sensing optical fiber, and when it is determined that the measured Rayleigh scattering frequency is out of the set reference range, the reference range in the measurement path Determine the section of the sensing optical fiber where the Rayleigh scattering frequency outside is detected as an abnormality detection section, scan the determined abnormality detection section to control the second measurement unit to detect the Brillouin scattered light, and for the abnormality detection section Abnormality of the sensing optical fiber by using the raillane scattering signal frequency measured by the first measuring unit and the Brillouin scattering signal frequency information measured from the Brillouin scattering light measured by the second measuring unit for the abnormality detection section. And a signal processing unit for calculating temperature and strain for each position of the detection section. The method of claim 1, wherein the first measurement unit
A first light source unit for emitting a first optical signal having a variable wavelength;
A first optical coupler for distributing the first optical signal emitted from the first light source unit into a first minute background path and a second minute background path;
A second optical coupler for distributing light traveling through the first minute background path into a third minute background path and a fourth minute background path;
A first light outputting a first optical signal proceeding in the third minute background path to a first sensing end, and outputting a Rayleigh scattering light traveling in reverse through the first sensing end from the sensing optical fiber to a first sensing end Circulatory system;
A frequency monitoring interferometer generating frequency monitoring interference light to monitor a frequency of the first optical signal traveling through the second minute background path;
A third optical coupler which combines and outputs the Rayleigh scattered light output from the first detection end of the first optical circulator and the first optical signal traveling through the fourth minute background path;
A first photodetector for detecting the light output from the third optical coupler and providing it to the signal processor;
And a second optical detector that detects the light output from the frequency monitoring interferometer and provides it to the signal processing unit. The method of claim 2, wherein the second measurement unit
A second light source unit controlled by the signal processing unit to output light having a modulated frequency;
Light generated to generate the probe light and the pump light including a sideband signal using the light output from the second light source unit, and to apply the pump light and the probe light to one end and the other end of the sensing optical fiber, respectively. A modulator;
A second optical circulator for outputting the pump light generated by the light modulator through a second sensing stage, and outputting light traveling in the reverse direction from the second sensing stage to a second detection stage;
An optical switch configured to connect one end of the sensing optical fiber to any one of the first sensing end and the second sensing end;
Equipped with a third photodetector that detects the Brillouin scattered light that is reversed from the second sensing stage and output from the second detection stage and provides it to the signal processor.
The signal processing unit controls the connection path of the optical switch, measures the frequency of the Rayleigh scattering signal for the sensing optical fiber from the signals output from the first and second optical detectors, and the signal received from the third optical detector. Distribution fiber optic sensor device, characterized in that for measuring the frequency of the Brillouin scattering signal. The method of claim 3, wherein the signal processing unit
The Rayleigh scattering signal frequency (v _R ) calculated using the signal received through the first photodetector and the signal received through the second photodetector, and the signal received through the third photodetector The Rayleigh scattering signal frequency difference value (Δv) corresponding to the difference between the initial value of the Rayleigh scattering signal frequency set for the calculated Brillouin scattering signal frequency (v _B ) and the measured Rayleigh scattering signal frequency for the abnormality detection section. _{From R} ) and the set Brillouin scattering signal frequency initial value and the Brillouin scattering signal frequency difference value (Δv _B ) corresponding to the difference between the measured Brillouin scattering signal frequency for the abnormality detection section

Change temperature by the formula of

) And strain change value (

),
here,

Is the frequency sensitivity to the temperature of the Rayleigh signal,

Is the frequency sensitivity to the strain of the Rayleigh signal,

Is the frequency sensitivity to the temperature of the Brillouin signal,

Is a distributed optical fiber sensor device, characterized in that the frequency sensitivity to the strain of the Brillouin signal. The method of claim 4, wherein the light modulator
A polarization maintenance coupler for distributing light through the fifth and sixth background paths while maintaining the polarization state of the light output from the second light source unit;
A first modulator for modulating light traveling through the fifth minute background path into the probe light;
And a second modulator configured to modulate the light traveling through the sixth minute background path into the pump light. The frequency monitoring interferometer of claim 5,
An interference coupler for distributing and outputting light traveling through the second minute background path to a reference end and a delay end, respectively, and outputting the monitored interference light reversed from the reference end and the delay end to the second light detector; ;
A reference optical fiber connected to the reference terminal;
And a delayed optical fiber that is connected to the delayed stage and extends longer than the reference optical fiber. The distributed optical fiber sensor device according to claim 6, further comprising a polarization controller that adjusts polarization of light traveling through the fourth minute background path of the second optical coupler and outputs it to the third optical coupler. . A sensing optical fiber that is installed to extend along a measurement path, a first measuring unit that applies a first wavelength-tunable optical signal to the sensing optical fiber and detects Rayleigh scattered light scattered from the sensing optical fiber, and probes at both ends of the sensing optical fiber The second measurement unit detects the Brillouin scattered light generated from the sensing optical fiber by incident light and pump light traveling in opposite directions, and the temperature and position of the sensing optical fiber while controlling the driving of the first and second measurement units. In the control method of the distribution type optical fiber sensor device having a signal processor for calculating the strain,
end. Measuring the frequency of the Rayleigh scattering signal from the Rayleigh scattered light measured for the sensing optical fiber while driving the first measurement unit;
I. Determining whether the Rayleigh scattering frequency measured in step A is outside a preset reference range;
All. Extracting an abnormality detection section of the sensing optical fiber in which the Rayleigh scattering frequency outside the reference range is detected when it is determined in step B that the Rayleigh scattering frequency is outside the set reference range;
la. Scanning the abnormality detection section and driving the second measurement unit to detect the Brillouin scattered light;
hemp. Calculating temperature and strain for each position of the abnormality detection section from the Brillouin scattering signal frequency information measured through the step La for the abnormality detection section and the Rayleigh scattering frequency measured for the abnormality detection section; Control method of a distributed optical fiber sensor device comprising a.

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