CN115388918A - Distributed temperature and vibration measurement system and method - Google Patents
Distributed temperature and vibration measurement system and method Download PDFInfo
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- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
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- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
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Abstract
The invention discloses a distributed temperature and vibration measuring system and method, which comprises a laser light source, an acousto-optic modulator, a first circulator, a weak grating array, a first coupler, a second circulator, a second coupler, two reflectors and a data processing module, wherein the laser light source, the acousto-optic modulator, the first circulator and the weak grating array are sequentially connected, the first coupler, the second circulator, the second coupler and the reflectors are sequentially connected, the other end of the first coupler is connected with the output end of the first circulator, and the data processing module is respectively connected with the first coupler and the second coupler. The invention solves the problems of high cost and poor signal-to-noise ratio of a distributed temperature and vibration measurement system in the prior art.
Description
Technical Field
The invention relates to the technical field of grating optical fiber sensing, in particular to a distributed temperature and vibration measuring system and method.
Background
Optical fiber sensing technology has many advantages to electric sensor, and in the face of the huge demand of the high-speed development of the internet of things industry, optical fiber sensing technology is facing new opportunity and challenge, but has the contradiction between the variety of optical fiber sensing demand and the optical fiber sensing function unicity, at oil gas well exploitation and detection, oil gas pipeline, gas holder, large-scale piping lane etc., if can monitor the sound attitude signal of vibration and temperature simultaneously, then can significantly reduce monitored control system's cost to improve the validity and the reliability of monitoring.
The method is based on optical backscattering technology sensing, and can be used for measuring quasi-static physical quantities such as temperature, strain and the like, for example, the Brillouin scattering technology can be used for measuring the temperature or the strain in a distributed manner; another is to use the interference effect in the optical fiber to measure dynamic signals such as vibration, such as those based on rayleigh scattered light polarization effect, C-OTDR, sagnac interference and Mach-Zender interference, which uses phase or polarization information in the optical fiber and is very sensitive to rapidly changing dynamic signals, but cannot measure quasi-static temperature/strain parameters. Some scholars use Raman scattering or Brillouin scattering with
The integration realizes the distributed demodulation of dynamic and static sensing signals, but the system has poor signal-to-noise ratio and high cost; for the current method using the combination of rayleigh scattering and brillouin scattering, because brillouin scattering can generate large frequency shift due to temperature or vibration, a detector and an acquisition card required by the system have large bandwidth, which leads to the increase of the overall cost of the system; in addition, there is a solution that uses a tunable light source and a narrow line width light source as a detection light source, and uses a grating array as a sensor, but the pulse modulation process and the signal acquisition process require extra cost for processing.
Therefore, it is desirable to provide a system and method for simultaneously measuring temperature and vibration to solve the problems of poor signal-to-noise ratio and high cost of the prior art distributed demodulation system for simultaneously measuring dynamic and static sensing signals.
Disclosure of Invention
The invention aims to overcome the technical defects, provides a distributed temperature and vibration measuring system and a distributed temperature and vibration measuring method, and solves the technical problems of poor signal-to-noise ratio and high cost of a distributed demodulation system for simultaneously measuring dynamic and static sensing signals in the prior art.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a distributed temperature and vibration measurement system comprising:
the laser light source, the acousto-optic modulator, the first circulator, the weak grating array, the first coupler, the second circulator, the second coupler, the two reflectors and the data processing module are sequentially connected, the first coupler, the second circulator, the second coupler and the reflectors are sequentially connected, the other end of the first coupler is connected to the output end of the first circulator, and the data processing module is respectively connected to the first coupler and the second coupler;
the laser light source is used for generating continuous light;
the acousto-optic modulator is used for modulating the continuous light into corresponding pulse light and inputting the pulse light to the first circulator;
the first circulator is used for receiving the pulse light and inputting the pulse light into the weak grating array;
the weak grating array is used for generating a first reflection signal according to the pulse light and inputting the first reflection signal to the first circulator;
the first circulator is also used for conveying the first reflection signal to a first coupler;
the first coupler is used for receiving the first reflection signal and dividing the first reflection signal into a detection signal and a detection signal;
the second circulator is used for receiving the detection signal and inputting the detection signal to the second coupler;
the second coupler is used for receiving the detection signal and generating three groups of second reflection signals based on the two reflection mirrors;
the data processing module is used for receiving the detection signal and the three groups of second reflection signals and respectively converting the detection signal and the second reflection signals into a first electric signal and three groups of second electric signals.
In some embodiments, the distributed temperature and vibration measurement system further comprises a signal generator connected to the acousto-optic modulator for generating a drive signal to vary the period and pulse width of the pulsed light output by the acousto-optic modulator.
In some embodiments, the distributed temperature and vibration measurement system further comprises an erbium-doped fiber amplifier disposed between the acousto-optic modulator and the first circulator for amplifying the pulsed light; the acousto-optic modulator is used for inputting the pulse light to the first circulator, and specifically includes that the acousto-optic modulator transmits the pulse light to the erbium-doped fiber amplifier, and the pulse light is amplified by the erbium-doped fiber amplifier and then input to the first circulator.
In some embodiments, the laser light source is configured to generate continuous light, and specifically, the output wavelength of the continuous light is gradually increased by a set wavelength, and the wavelength of the continuous light can be expressed by the following formula: lambda [ alpha ] m ＝λ 1 +mΔλ 1 Wherein λ is 1 At the initial wavelength, λ m To terminate the wavelength, Δ λ 1 M is a wavelength change coefficient.
In some embodiments, the data processing module comprises a photodetector, a first digital processing unit and a second digital processing unit, the photodetector being connected to the first coupler, the second coupler, the first digital processing unit and the second digital processing unit, respectively;
the photoelectric detector is used for receiving the detection signals and the three groups of second reflection signals and converting the detection signals and the three groups of second reflection signals into first electric signals and three groups of second electric signals;
the first digital processing unit is used for receiving the first electric signal, processing the first electric signal through a preset temperature processing program and determining the changed temperature;
and the second digital processing unit is used for receiving the three groups of second electric signals, sequentially carrying out decoding demodulation and calibration on the second electric signals and determining vibration phase information.
In some embodiments, the processing the first electrical signal by a preset temperature processing program to determine the changed temperature includes:
acquiring an initial room temperature value, scanning the continuous light with all wavelengths based on the initial room temperature value, and acquiring initial spectrum data of all gratings in the weak grating array;
calibrating the corresponding relation between the spectrum drift amount and the temperature change value according to the initial spectrum data, and determining the correlation parameter between the drift amount and the temperature change value;
acquiring intensity information reflected by the grating under all wavelength states;
establishing a cross-correlation relationship between the initial spectrum data and the intensity information, and determining a spectrum drift amount;
and determining the changed temperature according to the spectrum drift amount, the initial room temperature value and the associated parameters.
In some embodiments, said sequentially performing decoding demodulation and calibration on said second electrical signal to determine vibration phase information includes:
based on the second digital processing unit, demodulating the second electric signals of all wavelengths in one scanning period to obtain a demodulated phase value in each sensing area;
and calibrating the phase values under different wavelengths so as to enable the demodulation phase to determine vibration phase information of a unified standard according to a set wavelength reference.
In some embodiments, the arm difference between two of the mirrors is consistent with the spacing between two adjacent gratings, wherein the adjacent weak grating spacing may be expressed by the following equation:
where L is the spatial resolution of the system, c is the speed of light in vacuum, τ is the modulated optical pulse width, and n is the effective index of refraction of the fiber.
In some embodiments, the first coupler is a 1*2 coupler and the second coupler is a 3*3 coupler.
In a second aspect, the present invention also provides a method of distributed temperature and vibration measurement, comprising:
acquiring continuous light and modulating the continuous light into corresponding pulse light;
acquiring a first reflection signal according to the pulsed light;
receiving the first reflection signal, and dividing the reflection signal into a detection signal and a detection signal;
obtaining three groups of second reflection signals according to the detection signals;
and receiving the detection signal and the three groups of second reflection signals, and determining the changed temperature value and vibration phase information according to the detection signal and the three groups of second reflection signals respectively.
Compared with the prior art, the distributed temperature and vibration measuring system and method provided by the invention have the advantages that continuous light is generated by the laser light source, the continuous light is modulated into corresponding pulse light by the acousto-optic modulator, the pulse light is input into the weak grating array by the first circulator to obtain a first reflection signal, then the weak grating array reflects the first reflection signal to the first circulator and inputs the first reflection signal to the first coupler by the first circulator, then the first coupler divides the first reflection signal into a detection signal and a detection signal, then the detection signal is input to the second coupler by the second circulator, the second coupler inputs the detection signal to the second coupler and generates three groups of second reflection signals based on the two reflectors, and finally the detection signal and the three groups of reflection signals are converted into electric signals by the data processing module; the invention adopts a laser light source as a detection light source, does not need to additionally process the modulation of the light source and the acquisition of signals in the later period, saves the cost, adopts the grating array as a sensor, can measure the temperature according to the drift of the grating spectrum on the one hand, and can reflect the signals stronger than the common Rayleigh scattering on the other hand, and can obtain the signals with higher signal-to-noise ratio at a demodulation end.
Furthermore, the first reflected light is divided into the detection signal and the detection signal through the first coupler, temperature change information can be obtained through the detection signal, then the detection light is divided into three groups of second reflected signals through the second coupler and the two reflectors, and vibration phase information can be obtained through the three groups of second reflected signals, so that the purpose of simultaneously measuring temperature and vibration is achieved, and the signal-to-noise ratio of the sensor is improved in a grating array mode.
Drawings
FIG. 1 is a schematic block diagram of an embodiment of a distributed temperature and vibration measurement system provided by the present invention;
FIG. 2 is a graph of intensity information distribution of all gratings at different probing wavelengths in an embodiment of a distributed temperature and vibration measurement system provided by the present invention;
FIG. 3 is a flow chart of temperature determination in one embodiment of a distributed temperature and vibration measurement system provided by the present invention;
FIG. 4 is a flow chart of vibration phase information determination in one embodiment of a distributed temperature and vibration measurement system provided by the present invention;
FIG. 5 is a graph of a distribution of phase values demodulated by different wavelengths of probe light in an embodiment of a distributed temperature and vibration measurement system provided by the present invention;
FIG. 6 is a flow chart of one embodiment of a distributed temperature and vibration measurement method provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
The distributed optical fiber sensing is widely applied by virtue of the advantages of electromagnetic interference resistance, no electricity, corrosion resistance, high temperature resistance, low unit cost and the like, wherein the detection of temperature information and vibration information is very concerned, especially in some important infrastructures, the vibration detection can effectively detect cracks, the change of temperature is closely related to the generation of the cracks, and meanwhile, the fire monitoring of large civil buildings can be detected.
The distributed temperature and vibration measuring system and method not only overcome the problem of low signal-to-noise ratio in the traditional temperature vibration detecting system, but also overcome the problems of complex structure and high cost of the traditional detecting system; fig. 1 is a schematic structural diagram of a distributed temperature and vibration measurement system 10 according to an embodiment of the present invention, including: the laser light source 11, the acousto-optic modulator 12, the first circulator 13, the weak grating array 14, the first coupler 15, the second circulator 16, the second coupler 17, the two reflectors 18 and the data processing module 19, wherein the laser light source 11, the acousto-optic modulator 12, the first circulator 13 and the weak grating array 14 are sequentially connected, the first coupler 15, the second circulator 16, the second coupler 17 and the reflectors 18 are sequentially connected, the other end of the first coupler 15 is connected to the output end of the first circulator 13, and the data processing module 19 is respectively connected to the first coupler 15 and the second coupler 17;
the laser light source 11 is used for generating continuous light;
the acousto-optic modulator 12 is configured to modulate the continuous light into corresponding pulsed light, and input the pulsed light to the first circulator 13;
the first circulator 13 is used for receiving the pulsed light and inputting the pulsed light into the weak grating array 14;
the weak grating array 14 is configured to generate a first reflection signal according to the pulsed light, and input the first reflection signal to the first circulator 13;
the first circulator 13 is further configured to transmit the first reflected signal to a first coupler 15;
the first coupler 15 is configured to receive the first reflected signal and divide the first reflected signal into a detection signal and a detection signal;
the second circulator 16 is configured to receive the detection signal and input the detection signal to the second coupler 17;
the second coupler 17 is configured to receive the detection signal and generate three sets of second reflection signals based on two of the mirrors 18;
the data processing module 19 is configured to receive the detection signal and the three sets of second reflection signals, and convert the detection signal and the second reflection signals into a first electrical signal and three sets of second electrical signals, respectively.
In the present embodiment, continuous light is generated by the laser light source 11, the continuous light is modulated into corresponding pulsed light by the acousto-optic modulator 12, the pulsed light is input into the weak grating array 14 by the first circulator 13, a first reflection signal is obtained, then the weak grating array 14 reflects the first reflection signal to the first circulator 13 and inputs the first reflection signal to the first coupler 15 by the first circulator 13, then the first coupler 15 divides the first reflection signal into a detection signal and a detection signal, then the detection signal is input into the second coupler 17 by the second circulator 16, three sets of second reflection signals are generated based on the two mirrors 18, and finally the detection signal and the three sets of reflection signals are converted into electrical signals by the data processing module 19; the invention adopts a laser light source 11 as a detection light source, does not need to additionally process the modulation of the light source and the acquisition of signals in the later period, saves the cost, adopts the grating array 14 as a sensor, can measure the temperature according to the drift of a grating spectrum on the one hand, and can reflect a signal stronger than the common Rayleigh scattering to the detection signal within the grating bandwidth on the other hand, and can obtain a signal with higher signal-to-noise ratio at a demodulation end.
It should be noted that the optical fiber used in the embodiment of the present invention is a weak grating array with identical low reflectivity, the grating is a chirped grating, the 3dB bandwidth exceeds 3nm, the reflectivity is-50 dB, and the grating array interval is 3m or 5 m.
Wherein, as a preferred embodiment, the first coupler is 1*2 coupler, and the second coupler is 3*3 coupler.
In some embodiments, the distributed temperature and vibration measurement system 10 further comprises a signal generator 1a, wherein the signal generator 1a is connected to the acousto-optic modulator 12 and is used for generating a driving signal so as to change the period and the pulse width of the pulsed light output by the acousto-optic modulator 12.
It should be noted that by providing the signal generator 1a, the pulse and period of the acousto-optic modulator 12 can be changed, so that the continuous light passing through the acousto-optic modulator 12 is finally modulated into the required pulse light.
In some embodiments, the distributed temperature and vibration measurement system 10 further includes an erbium-doped fiber amplifier 1b, the erbium-doped fiber amplifier 1b being disposed between the acousto-optic modulator 12 and the first circulator 13, for amplifying the pulsed light; the acousto-optic modulator 12 is configured to input the pulsed light to the first circulator 13, and specifically includes that the acousto-optic modulator 12 transmits the pulsed light to the erbium-doped fiber amplifier 1b, and the pulsed light is amplified by the erbium-doped fiber amplifier 1b and then input to the first circulator 13.
In the present embodiment, by providing the erbium-doped fiber amplifier 1b, the intensity of the pulse light input into the first circulator 13 can be ensured, so that the vibration and temperature measurement accuracy can be improved.
In some embodiments, the laser light source is configured to generate continuous light, and specifically, the output wavelength of the continuous light is gradually increased by a set wavelength, and the wavelength of the continuous light can be expressed by the following formula: lambda [ alpha ] m ＝λ 1 +mΔλ 1 Wherein λ is 1 Is the initial wavelength, λ m To terminate the wavelength, Δ λ 1 M is a wavelength change coefficient.
In this embodiment, the phase obtained by demodulating the detection light of each wavelength is calibrated, and compared with using a fixed wavelength in the tunable light source as the detection light, the method makes full use of the wavelength resource, improves the response speed of the system, and increases the vibration response bandwidth.
In a specific embodiment, please refer to fig. 2, where fig. 2 is intensity information obtained when all gratings in a grating array are detected at corresponding wavelengths, where an abscissa represents a wavelength sequence of emitted laser, an ordinate represents a grating serial number in the grating array, and when a detection pulse of each wavelength returns, intensity information corresponding to the wavelength at a position of the grating is obtained, and when a tunable laser scans all wavelengths, grating spectrum data at the time can be obtained according to the collected intensity information.
In some embodiments, the data processing module 19 comprises a photodetector 191, a first digital processing unit 192 and a second digital processing unit 193, the photodetector 191 being connected to the first coupler 15, the second coupler 17, the first digital processing unit 192 and the second digital processing unit 193, respectively;
the photodetector 191 is configured to receive the detection signals and the three sets of second reflection signals, and convert the detection signals and the three sets of second reflection signals into first electrical signals and three sets of second electrical signals;
the first digital processing unit 192 is configured to receive the first electrical signal, process the first electrical signal through a preset temperature processing program, and determine a changed temperature;
the second digital processing unit 193 is configured to receive the three sets of the second electrical signals, and sequentially perform decoding demodulation and calibration on the second electrical signals to determine vibration phase information.
In this embodiment, the first digital processing unit 192 processes the detection signal to obtain a first electrical signal, and then processes the first electrical signal through a temperature processing program to obtain a temperature variation value, so as to obtain a temperature value after variation, thereby achieving the purpose of temperature detection; the three sets of second reflection signals are processed by the second digital processing unit 193 to obtain three sets of second electrical signals, and vibration phase information is obtained according to the second electrical signals, so that the vibration information is monitored.
In some embodiments, referring to fig. 3, the processing the first electrical signal by a predetermined temperature processing program to determine the changed temperature includes:
s301, acquiring an initial room temperature value, scanning the continuous light with all wavelengths based on the initial room temperature value, and acquiring initial spectrum data of all gratings in the weak grating array;
s302, calibrating the corresponding relation between the spectrum drift amount and the temperature change value according to the initial spectrum data, and determining the correlation parameter between the drift amount and the temperature change value;
s303, acquiring intensity information reflected by the grating under all wavelength states;
s304, establishing a cross-correlation relationship between the initial spectrum data and the intensity information, and determining a spectrum drift amount;
s305, determining the changed temperature according to the spectrum drift amount, the initial room temperature value and the related parameters.
In the present embodiment, first at room temperature T 0 Under the condition, the tunable laser scans continuous light with all wavelengths once to obtain initial spectrum data of all gratings in the grating array, and then calibrates the corresponding relation between the grating spectrum drift quantity delta lambda and the temperature change value delta T to obtain the correlation parameter k value between the drift quantity and the temperature change value; acquiring intensity information of the reflection of the grating obtained by each detection, judging whether all the wavelengths are scanned or not, if not, continuing to scan to acquire complete grating spectrum information, and if so, comparing the spectrum data with the room temperature T 0 Performing cross-correlation operation on the obtained spectrum data under the condition, wherein the maximum value index in the operation result is consistent with the drift amount of the grating spectrum, so that the drift amount of the grating spectrum generated due to temperature change at the moment can be obtained, and finally, the formula T = T 0 + k Δ λ, the temperature T after the change can be calculated 1 。
In some embodiments, referring to fig. 4, the sequentially performing decoding demodulation and calibration on the second electrical signal to determine vibration phase information includes:
s401, demodulating second electric signals of all wavelengths in a scanning period based on the second digital processing unit, and acquiring a demodulated phase value in each sensing area;
s402, calibrating the phase values under different wavelengths to enable the demodulation phase to be in accordance with a set wavelength reference, and determining vibration phase information of a unified standard.
In this embodiment, since the second coupler is a 3 × 3 coupler, the output phase differs by 120 °, firstly, the wavelength difference of the probe light is neglected, the 3*3 algorithm processing is performed on the three-way interference signal, and the phase change value of each sensing area is obtained by demodulation
After the tunable laser scans all the wavelengths, a demodulation phase as shown in fig. 5 can be obtained, m phase values are obtained by demodulation in a single sensing area, and the phase obtained by demodulation can be matched with the wavelength according to the corresponding relation between the detection wavelength and time. FIG. 5 shows the phase values obtained by demodulating the probe light of different wavelengths in one scanning cycle, with the abscissa being the wavelength sequence λ of the emitted laser light 1 ～λ m The emission time t corresponding to the wavelength is marked later 1 ～t m The ordinate is the serial numbers 1-n-1 of the sensing area, and each row of data represents the phase value obtained by detection and demodulation in the sensing area.
Further according to the formula
It can be known that, for the same optical fiber deformation, the phase values obtained by demodulating the probe lights with different wavelengths are different, i.e. the response of the probe lights with different wavelengths to the same vibration condition is different and has an inverse relationship with the wavelength of the probe light, so as to obtain the wavelength λ of the initial probe light 1 For reference, the phase obtained by demodulating the detection light of all wavelengths in fig. 5 can be expressed as
It can be seen that, compared with the actual vibration signal, there is a certain error in the measurement and restoration using the detection light with different wavelengths, so that the demodulation phases under different detection wavelengths need to be calibrated, so that the demodulation phases are unified on a certain wavelength reference, thereby eliminating the error and correctly restoring the vibration information; if at wavelength λ 1 The detected light is used as a reference to perform phase calibration, and the calibration coefficient alpha can be expressed as
Specifically, the demodulation phase obtained in each sensing area is matched with the wavelength of the probe light according to the time correspondence, the matched demodulation phase is multiplied by the calibration coefficient of the corresponding wavelength, so that the demodulation phases can be unified, and the demodulation phases under different wavelengths are converted into the wavelength lambda 1 Demodulation phase for reference:
further, by phase alignment, the wavelength λ is increased phase-changeably 1 The transmission frequency of the system improves the response speed of the system and increases the response bandwidth of vibration.
As a preferred embodiment, the arm difference between two of said mirrors 18 coincides with the spacing between two adjacent gratings, wherein the adjacent weak grating spacing can be expressed by the following formula:
where L is the spatial resolution of the system, c is the speed of light in vacuum, τ is the modulated optical pulse width, and n is the effective index of refraction of the fiber.
In this embodiment, the transmitting mirror 18 is two faraday rotators, the arm length difference between the two faraday rotators and the interval between adjacent weak gratings are both L, reflected signals at adjacent gratings generate interference in the 3*3 coupler, finally the 3*3 coupler outputs 3 interference signals with a phase difference of 120 °, the interference signals are converted into electrical signals by 3 photodetectors respectively, the signal generator drives the acousto-optic modulator and simultaneously provides a synchronous trigger signal for the acquisition card, and after 4 paths of electrical signals are collected and processed, the final result is uploaded to an upper computer for display and storage.
Based on the above-mentioned distributed temperature and vibration measurement system, an embodiment of the present invention further provides a method for measuring distributed temperature and vibration, please refer to fig. 6, which includes:
s601, acquiring continuous light, and modulating the continuous light into corresponding pulse light;
s602, acquiring a first reflection signal according to the pulse light;
s603, receiving the first reflection signal, and dividing the reflection signal into a detection signal and a detection signal;
s604, obtaining three groups of second reflection signals according to the detection signals;
and S605, receiving the detection signal and the three groups of second reflection signals, and determining the changed temperature value and vibration phase information according to the detection signal and the three groups of second reflection signals respectively.
In the embodiment, the first reflected light is divided into the detection signal and the detection signal by the first coupler, the temperature change information can be obtained by the detection signal, then the detection light is divided into three groups of second reflected signals by the second coupler and the two reflectors, and the vibration phase information can be obtained by the three groups of second reflected signals, so that the purpose of simultaneously measuring the temperature and the vibration is realized, and the signal-to-noise ratio of the sensor is improved in a grating array mode.
The above-described embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A distributed temperature and vibration measurement system, comprising: the laser light source, the acousto-optic modulator, the first circulator, the weak grating array, the first coupler, the second circulator, the second coupler, the two reflectors and the data processing module are sequentially connected, the first coupler, the second circulator, the second coupler and the reflectors are sequentially connected, the other end of the first coupler is connected to the output end of the first circulator, and the data processing module is respectively connected to the first coupler and the second coupler;
the laser light source is used for generating continuous light;
the acousto-optic modulator is used for modulating the continuous light into corresponding pulse light and inputting the pulse light to the first circulator;
the first circulator is used for receiving the pulse light and inputting the pulse light into the weak grating array;
the weak grating array is used for generating a first reflection signal according to the pulse light and inputting the first reflection signal to the first circulator;
the first circulator is also used for conveying the first reflection signal to a first coupler;
the first coupler is used for receiving the first reflection signal and dividing the first reflection signal into a detection signal and a detection signal;
the second circulator is used for receiving the detection signal and inputting the detection signal to the second coupler;
the second coupler is used for receiving the detection signal and generating three groups of second reflection signals based on the two reflectors;
the data processing module is used for receiving the detection signal and the three groups of second reflection signals and respectively converting the detection signal and the second reflection signals into a first electric signal and three groups of second electric signals.
2. The distributed temperature and vibration measurement system of claim 1 further comprising a signal generator connected to the acousto-optic modulator for generating a drive signal to vary the period and pulse width of the pulsed light output by the acousto-optic modulator.
3. The distributed temperature and vibration measurement system of claim 1, further comprising an erbium doped fiber amplifier disposed between the acousto-optic modulator and the first circulator for amplifying the pulsed light; the acousto-optic modulator is used for inputting the pulse light to the first circulator, and specifically includes that the acousto-optic modulator transmits the pulse light to the erbium-doped fiber amplifier, and the pulse light is amplified by the erbium-doped fiber amplifier and then input to the first circulator.
4. The distributed temperature and vibration measurement system of claim 1, wherein the laser light source is configured to generate a continuous light, and in particular wherein the output wavelength of the continuous light is increased in steps at a set wavelength, and wherein the wavelength of the continuous light is expressed by the following formula: lambda [ alpha ] m ＝λ 1 +mΔλ 1 Wherein λ is 1 Is the initial wavelength, λ m To terminate the wavelength, Δ λ 1 M is a wavelength change coefficient.
5. The distributed temperature and vibration measurement system of claim 4, wherein the data processing module comprises a photodetector, a first digital processing unit, and a second digital processing unit, the photodetector being connected to the first coupler, the second coupler, the first digital processing unit, and the second digital processing unit, respectively;
the photoelectric detector is used for receiving the detection signals and the three groups of second reflection signals and converting the detection signals and the three groups of second reflection signals into first electric signals and three groups of second electric signals;
the first digital processing unit is used for receiving the first electric signal, processing the first electric signal through a preset temperature processing program and determining the changed temperature;
and the second digital processing unit is used for receiving the three groups of second electric signals, sequentially carrying out decoding demodulation and calibration on the second electric signals and determining vibration phase information.
6. The distributed temperature and vibration measurement system of claim 5, wherein said processing the first electrical signal by a preset temperature processing program to determine a changed temperature comprises:
acquiring an initial room temperature value, scanning the continuous light with all wavelengths based on the initial room temperature value, and acquiring initial spectrum data of all gratings in the weak grating array;
calibrating the corresponding relation between the spectrum drift amount and the temperature change value according to the initial spectrum data, and determining the correlation parameter between the drift amount and the temperature change value;
acquiring intensity information reflected by the grating under all wavelength states;
establishing a cross-correlation relationship between the initial spectrum data and the intensity information, and determining a spectrum drift amount;
and determining the changed temperature according to the spectrum drift amount, the initial room temperature value and the associated parameters.
7. The distributed temperature and vibration measurement system of claim 1, wherein said sequentially decoding, demodulating, and calibrating said second electrical signal to determine vibration phase information comprises:
based on the second digital processing unit, demodulating the second electrical signals of all wavelengths in one scanning period to obtain a demodulated phase value in each sensing area;
and calibrating the phase values under different wavelengths so as to enable the demodulation phase to determine vibration phase information of a unified standard according to a set wavelength reference.
8. The distributed temperature and vibration measurement system of claim 1, wherein the arm difference between two of the mirrors is consistent with the spacing between two adjacent gratings, wherein the adjacent weak grating spacing can be expressed by the following equation:
where L is the spatial resolution of the system, c is the speed of light in vacuum, τ is the modulated optical pulse width, and n is the effective index of refraction of the fiber.
9. The distributed temperature and vibration measurement system of claim 1, wherein the first coupler is a 1*2 coupler and the second coupler is a 3*3 coupler.
10. A method of distributed temperature and vibration measurement, comprising:
acquiring continuous light and modulating the continuous light into corresponding pulse light;
acquiring a first reflection signal according to the pulse light;
receiving the first reflected signal, and dividing the reflected signal into a detection signal and a detection signal;
obtaining three groups of second reflection signals according to the detection signals;
and receiving the detection signal and the three groups of second reflection signals, and determining the changed temperature value and vibration phase information according to the detection signal and the three groups of second reflection signals respectively.
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