CN110631735A - Pipeline temperature measurement system and method based on distributed sensing optical fiber - Google Patents
Pipeline temperature measurement system and method based on distributed sensing optical fiber Download PDFInfo
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- G—PHYSICS
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
- G01K11/322—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres using Brillouin scattering
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
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Abstract
The invention provides a pipeline temperature measurement system and a method based on distributed sensing optical fibers, wherein a first sensing optical fiber and a second sensing optical fiber are arranged in parallel, the temperature changes of the first sensing optical fiber and the second sensing optical fiber are basically the same, the first sensing optical fiber is influenced by temperature and pressure, a second sensing pipeline is provided with a pressure shielding cover and is only influenced by temperature, the temperature and the Brillouin frequency shift caused by strain of the first sensing optical fiber are measured when the first sensing optical fiber is gated by switching a first optical switch and a second optical switch, the Brillouin frequency shift caused by the temperature of the second sensing optical fiber is measured when the second sensing optical fiber is gated, so that the temperature value can be obtained, the pressure value can be analyzed according to the linear relation between the Brillouin frequency shift of the optical fibers and the pressure and the temperature value obtained by the second sensing optical fiber, and the pipeline temperature measurement system has a simple structure, the simultaneous measurement of pressure and temperature can be realized, and the problem of temperature and pressure cross sensitivity can be avoided.
Description
Technical Field
The invention relates to the field of optical fiber sensing, in particular to a pipeline temperature measurement system and method based on distributed sensing optical fibers.
Background
In recent years, the optical fiber sensing technology is continuously advanced, and the optical fiber sensing technology is widely used in various fields such as military affairs, national defense, aerospace, industrial and mining enterprises, energy environmental protection, industrial control and the like, and has the advantages of strong anti-interference performance, high reliability, capability of being applied to various complex environments and the like. With the continuous progress of the optical fiber sensing technology, the distributed optical fiber sensing technology is widely used as a sensing technology for long-distance monitoring in safety monitoring of, for example, fire-fighting pipelines. The distributed optical fiber sensing technology analyzes signals of monitoring points in real time by arranging optical cables along a monitoring line, intelligently identifies behaviors of all the points and reasonably generates an alarm to reduce manpower and material resources required on the detection line, and improves monitoring efficiency.
The principle of the optical fiber sensing technology is as follows: when light waves are transmitted along the optical fiber under the action of the total reflection principle and enter an optical sensing probe (which can be an optical fiber or other photosensitive elements), the sensing probe modulates optical signals under the action of external measured parameters (temperature, pressure, deformation, acceleration, magnetic field and the like) to enable the light waves to generate changes in intensity, polarization state, interference effect, diffraction effect, scattering effect and the like to become modulated signal light, then the modulated signal light is transmitted to an optical detector and a demodulator through the optical fiber to extract parameters such as light intensity, phase, amplitude, polarization state, wavelength and the like representing the characteristics of the optical signals, and the corresponding measured changes are demodulated according to the changes of the parameters.
However, in practical application, the Brillouin optical time domain analyzer based on a single mode fiber can not distinguish the influences of two parameters of temperature and stress, and has the cross sensitivity problem, the cross sensitivity problem is eliminated by using the traditional principle that the Brillouin frequency shift of the middle core and the outer core of a multi-core fiber has difference to the change of the temperature and the stress, however, since the multi-core fiber is a leading-edge technology and is not widely used in the commercial field, the optical devices based on the multi-core fiber are not common, generally expensive and the process is not as mature as the single-mode fiber devices, in order to combine a multi-core fiber with a single-mode system, a specific mode multiplexing and demultiplexing means is required, for inputting a specified core in the multi-core fiber in the single-mode fiber, meanwhile, the light of the specified fiber core in the multi-core fiber is output to a single-mode system, so that the difficulty in building the system is increased; therefore, in order to solve the above problems, the present invention provides a pipeline temperature measurement system based on a distributed sensing optical fiber, which has a simple structure, can realize simultaneous measurement of pressure and temperature, and can avoid the cross sensitivity problem of temperature and pressure.
Disclosure of Invention
In view of this, the invention provides a pipeline temperature measurement system based on a distributed sensing optical fiber, which has a simple structure, can realize simultaneous measurement of pressure and temperature, and can avoid the problem of cross sensitivity of temperature and pressure.
The technical scheme of the invention is realized as follows: the invention provides a pipeline temperature measurement system based on a distributed sensing optical fiber, which comprises a laser, a coupler, a circulator, a pulse pump light generation unit, a continuous detection light generation unit, a photoelectric detection unit, a first optical switch, a second optical switch, a first sensing optical fiber and a second sensing optical fiber, wherein the first optical switch is connected with the second optical switch through a first optical fiber;
the second sensing pipeline is provided with a pressure shielding cover, and the first sensing optical fiber and the second sensing optical fiber are arranged in parallel;
an optical signal generated by a laser is divided into two paths of optical paths through a coupler, wherein one path of optical path generates pulse pump light through a pulse pump light generating unit, the pulse pump light enters a port 1 of a circulator, the other path of optical path generates continuous probe light through a continuous probe light generating unit, one end of a first sensing optical fiber and one end of a second sensing optical fiber are respectively connected with the output end of a first optical switch in a one-to-one correspondence manner, one end of the first sensing optical fiber and one end of the second sensing optical fiber are respectively connected with the input end of a second optical switch in a one-to-one correspondence manner, the continuous probe light enters one end of the first sensing optical fiber or one end of the second sensing optical fiber through the first optical switch, the continuous probe light is transmitted through the first sensing optical fiber or the second sensing optical fiber and reaches a port 3 of the circulator through the second optical switch, and a port 2 of the circulator is connected with the input.
On the basis of the above technical solution, preferably, the first sensing fiber and the second sensing fiber include a plurality of sensing fibers fused to the same optical fiber path, and the sensing fibers included in the first sensing fiber and the second sensing fiber are the same.
On the basis of the technical scheme, preferably, the pulse pump light generation unit comprises an acousto-optic pulse modulator, an erbium-doped fiber amplifier and a first polarizer which are connected in sequence;
an optical signal generated by the laser is divided into two paths of optical paths through the coupler, wherein one path of optical signal generates narrow pulse pump light with fixed frequency through the acousto-optic pulse modulator, the narrow pulse pump light is amplified to optical power of more than 20dBm through the erbium-doped optical fiber amplifier, and the amplified optical signal enters a port 1 of the circulator.
Further preferably, the extinction ratio of the acousto-optic pulse modulator is greater than 40 dB.
Further preferably, the continuous detection light generating unit includes an electromagnetic frequency modulator, a microwave generator, a second polarizer and an isolator;
the electro-optical frequency modulator generates continuous detection light with adjustable frequency shift, the microwave generator generates microwaves for adjusting the frequency shift of the continuous detection light, and the continuous detection light reaches the input end of the first optical switch after passing through the second polarizer and the isolator.
Further preferably, the degree of polarization of both the first polarizer and the second polarizer is less than 5%.
Further preferably, the photo detection unit comprises a photo detector and a digital signal processor;
the 2 ports of the circulator are electrically connected with the input end of the digital signal processor through the photoelectric detector.
On the other hand, the invention provides a pipeline temperature measurement method based on a distributed sensing optical fiber, which comprises the following steps:
s1, building a pipeline temperature measuring system;
s2, emitting continuous detection light to one of the sensing optical fibers through one 1 x 2 optical switch, transmitting the continuous detection light in the sensing optical fibers and transmitting the continuous detection light to a photoelectric detection unit through the other 1 x 2 optical switch, analyzing and knowing Brillouin frequency shift influenced by pressure and temperature by the photoelectric detection unit, gating the continuous detection light to the sensing optical fibers with pressure shielding covers and the photoelectric detection unit by the 1 x 2 optical switch, and analyzing and knowing the Brillouin frequency shift influenced by temperature by the photoelectric detection unit;
s3, the photoelectric detection unit analyzes the two Brillouin frequency shifts, a mathematical equation for measuring the same path and simultaneously laying two groups of sensing optical fibers is established according to the linear relation between the Brillouin frequency shifts and pressure and temperature, and the pressure value of the sensing optical fibers is solved according to the two Brillouin frequency shifts and the mathematical equation measured by the Brillouin analyzer.
On the basis of the above technical solution, preferably, the linear relationship between the brillouin frequency shift and the pressure and temperature in S3 is as follows: v. ofB＝CcP·P+CvT·T+vB0；
In the formula, vBIs the Brillouin frequency shift, v, of an optical fiber under the influence of pressure and temperatureB0The Brillouin frequency shift of the optical fiber when the pressure and the temperature are zero simultaneously, P is the pressure to be measured, T is the temperature to be measured, CcPIs the coefficient of Brillouin pressure, constant, CvTIs a temperature coefficient and is a constant.
On the basis of the above technical solution, preferably, the mathematical equation for simultaneously measuring two groups of sensing fibers arranged in the same path according to the linear relationship between the brillouin frequency shift and the pressure and temperature in S3 is as follows:
wherein the condition C must be satisfiedvP,1·CvT,2≠CvP,2·CvT,1。
Compared with the prior art, the pipeline temperature measuring system and method based on the distributed sensing optical fiber have the following beneficial effects:
(1) the first sensing optical fiber and the second sensing optical fiber are arranged in parallel, the first sensing optical fiber is influenced by temperature and pressure, the second sensing pipeline is provided with a pressure shielding cover, the second sensing optical fiber is isolated from strain and is only influenced by temperature because the pressure shielding cover is arranged outside the second sensing optical fiber, when the first sensing optical fiber is gated by switching the first optical switch and the second optical switch, the phase change caused by the temperature and the strain of the first sensing optical fiber is measured at the moment, when the second sensing optical fiber is gated, the Brillouin frequency shift caused by the temperature of the second sensing optical fiber is measured at the moment, and further the temperature value can be obtained, because the first sensing optical fiber and the second sensing optical fiber are arranged in parallel, the temperature change of the first sensing optical fiber and the second sensing optical fiber is basically the same, and according to the linear relation between the Brillouin frequency shift of the optical fibers and the pressure and the temperature, and the temperature value in the linear relation is obtained through the second sensing optical fiber, so that the pressure value can be analyzed.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a structural diagram of a pipeline temperature measuring system based on a distributed sensing optical fiber according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Example 1
As shown in fig. 1, the pipeline temperature measurement system based on the distributed sensing optical fiber of the present invention includes a laser, a coupler, a circulator, a pulsed pump light generation unit, a continuous probe light generation unit, a photoelectric detection unit, a first optical switch, a second optical switch, a first sensing optical fiber, and a second sensing optical fiber.
The specific connection relation and the optical path are as follows: an optical signal generated by a laser is divided into two paths of optical paths through a coupler, wherein one path of optical path generates pulse pump light through a pulse pump light generating unit, the pulse pump light enters a port 1 of a circulator, the other path of optical path generates continuous probe light through a continuous probe light generating unit, one end of a first sensing optical fiber and one end of a second sensing optical fiber are respectively connected with the output end of a first optical switch in a one-to-one correspondence manner, one end of the first sensing optical fiber and one end of the second sensing optical fiber are respectively connected with the input end of a second optical switch in a one-to-one correspondence manner, the continuous probe light enters one end of the first sensing optical fiber or one end of the second sensing optical fiber through the first optical switch, the continuous probe light is transmitted through the first sensing optical fiber or the second sensing optical fiber and reaches a port 3 of the circulator through the second optical switch, and a port 2 of the circulator is connected with the input.
Wherein the second sensing line is provided with a pressure shielding case; the first sensing optical fiber and the second sensing optical fiber are arranged in parallel, the first sensing optical fiber is influenced by temperature and pressure, and the second sensing optical fiber is externally provided with a pressure shielding cover, so that the second sensing optical fiber is isolated from strain, and only affected by temperature, when the first sensing optical fiber is gated by switching the first optical switch and the second optical switch, at the moment, the phase change caused by the temperature and the strain of the first sensing optical fiber is measured, and when the second sensing optical fiber is gated, measuring the Brillouin frequency shift caused by the temperature of the second sensing optical fiber, further obtaining the temperature value, because the first sensing optical fiber and the second sensing optical fiber are arranged in parallel, the temperature change suffered by the first sensing optical fiber and the second sensing optical fiber is basically the same, according to the linear relation between the Brillouin frequency shift of the optical fiber and the pressure and the temperature, and the temperature value in the linear relation is obtained through the second sensing optical fiber, so that the pressure value can be analyzed.
Further preferably, the first sensing optical fiber and the second sensing optical fiber each include a plurality of sensing optical fibers fused to the same optical fiber path, wherein each of the second sensing optical fibers is disposed in the pressure shielding case.
Further preferably, the pulsed pump light generation unit comprises an acousto-optic pulse modulator, an erbium-doped fiber amplifier and a first polarizer which are connected in sequence; an optical signal generated by the laser is divided into two paths of optical paths through the coupler, wherein one path of optical signal generates narrow pulse pump light with fixed frequency through the acousto-optic pulse modulator, the narrow pulse pump light is amplified to optical power of more than 20dBm through the erbium-doped optical fiber amplifier, and the amplified optical signal enters a port 1 of the circulator. The extinction ratio of the acousto-optic pulse modulator is larger than 40dB, and the polarization degree of the first polarizer is smaller than 5%.
Further preferably, the continuous detection light generating unit includes an electromagnetic frequency modulator, a microwave generator, a second polarizer and an isolator; the electro-optical frequency modulator generates continuous detection light with adjustable frequency shift, the microwave generator generates microwaves for adjusting the frequency shift of the continuous detection light, and the continuous detection light reaches the input end of the first optical switch after passing through the second polarizer and the isolator. Wherein the polarization degrees of the second polarizers are all less than 5%.
Further preferably, the photo detection unit comprises a photo detector and a digital signal processor; the 2 ports of the circulator are electrically connected with the input end of the digital signal processor through the photoelectric detector.
The working principle of the embodiment is as follows: the emergent light of the narrow linewidth optical fiber feedback laser is divided into two paths by an optical coupler, wherein one path generates narrow pulse pump light V with fixed frequency by an acousto-optic pulse modulator with extinction ratio larger than 40dBPAmplifying the optical power to be more than 20dBm by an erbium-doped fiber amplifier; the other path of light passes through a high-bandwidth electro-optical frequency modulator to generate continuous probe light V with adjustable frequency shiftP-VSThe frequency of which is controlled by a microwave generator, whereinThe electro-optical frequency modulator can perform upper sideband suppression under the control of bias current, only a lower sideband is left as detection light, and further noise is reduced, and the continuous detection light intensity is generally controlled below a milliwatt level so as to reduce pulse attenuation and improve the signal-to-noise ratio. Frequency difference V between pulsed light and continuous lightSAnd remains near the fiber brillouin frequency shift range. Because the polarization correlation of the stimulated Brillouin scattering is obvious, the two ends of the optical fiber are respectively connected with the polarization controllers with the polarization degrees less than 5% in series so as to inhibit the polarization mismatch fading of the Brillouin signal. The optical isolator is used for preventing external signal light from entering the laser to interfere with the emitted laser light. When the two columns of light propagate in opposite directions in the fibre and the frequency difference at which they meet at a point in the fibre approaches the brillouin frequency shift v at that locationBWhile detecting the light VP-VSWill be amplified so that V can be adjusted stepwise in a frequency sweep fashionSSo that v can be obtained while measuring the Brillouin gain signalB. The signal processing unit and the photoelectric detector receive and process signals according to the time sequence to judge and calculate the pulse flight time, and the signal-to-noise ratio can be improved through the accumulation average of repeated measurement.
Example 2
On the basis of embodiment 1, this embodiment provides a method for measuring temperature of a pipeline based on a distributed sensing optical fiber, including the following steps:
s1, building a pipeline temperature measuring system;
s2, emitting continuous detection light to one of the sensing optical fibers through one 1 x 2 optical switch, transmitting the continuous detection light in the sensing optical fibers and transmitting the continuous detection light to a photoelectric detection unit through the other 1 x 2 optical switch, analyzing and knowing Brillouin frequency shift influenced by pressure and temperature by the photoelectric detection unit, gating the continuous detection light to the sensing optical fibers with pressure shielding covers and the photoelectric detection unit by the 1 x 2 optical switch, and analyzing and knowing the Brillouin frequency shift influenced by temperature by the photoelectric detection unit;
s3, the photoelectric detection unit analyzes the two Brillouin frequency shifts, a mathematical equation for measuring the same path and simultaneously laying two groups of sensing optical fibers is established according to the linear relation between the Brillouin frequency shifts and pressure and temperature, and the pressure value of the sensing optical fibers is solved according to the two Brillouin frequency shifts and the mathematical equation measured by the Brillouin analyzer.
The Brillouin frequency shift of the optical fiber has a linear relation with pressure and temperature at the same time as follows: v. ofB＝CcP·P+CvT·T+vB0 (1)；
In the formula, vBIs the Brillouin frequency shift, v, of an optical fiber under the influence of pressure and temperatureB0The Brillouin frequency shift of the optical fiber when the pressure and the temperature are zero simultaneously, P is the pressure to be measured, T is the temperature to be measured, CcPIs the coefficient of Brillouin pressure, constant, CvTIs a temperature coefficient, is a constant;
two groups of sensing optical fibers with different response characteristics are simultaneously distributed on the same measuring point or measuring path, two groups of measured values are obtained, an equation set is constructed, and the solution is represented in mathematical expression as follows:
wherein the condition C must be satisfiedvP,1·CvT,2≠CvP,2·CvT,1；
Further converting the formula (2) to obtain the following formula (3), solving the formula (3) to obtain the pressure value and the temperature value:
the above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. The utility model provides a pipeline temperature measurement system based on distributed sensing optical fiber, its includes laser instrument, coupler, circulator, pulse pump light generation unit, continuous probe light generation unit and photoelectric detection unit, its characterized in that: the optical fiber sensor also comprises a first optical switch, a second optical switch, a first sensing optical fiber and a second sensing optical fiber;
the second sensing pipeline is provided with a pressure shielding cover, and the first sensing optical fiber and the second sensing optical fiber are arranged in parallel;
the optical signal generated by the laser is divided into two paths of optical paths through the coupler, wherein one path of optical path generates pulse pump light through the pulse pump light generating unit, the pulse pump light enters the port 1 of the circulator, the other path of optical path generates continuous probe light through the continuous probe light generating unit, one end of the first sensing optical fiber and one end of the second sensing optical fiber are respectively connected with the output end of the first optical switch in a one-to-one correspondence manner, one end of the first sensing optical fiber and one end of the second sensing optical fiber are respectively connected with the input end of the second optical switch in a one-to-one correspondence manner, the continuous probe light enters one end of the first sensing optical fiber or one end of the second sensing optical fiber through the first optical switch, and the continuous probe light is transmitted in the first sensing optical fiber or the second sensing optical fiber, and reaches the 3 port of the circulator through the second optical switch, and the 2 port of the circulator is connected with the input end of the photoelectric detection unit.
2. The pipeline temperature measurement system based on the distributed sensing optical fiber as claimed in claim 1, wherein: the first sensing optical fiber and the second sensing optical fiber comprise a plurality of sensing optical fibers which are welded into the same optical fiber passage, and the number of the sensing optical fibers contained in the first sensing optical fiber and the second sensing optical fiber is the same.
3. The pipeline temperature measurement system based on the distributed sensing optical fiber as claimed in claim 1, wherein: the pulse pump light generating unit comprises an acousto-optic pulse modulator, an erbium-doped fiber amplifier and a first polarizer which are connected in sequence;
the laser generates optical signals which are divided into two paths of optical paths through the coupler, wherein one path of optical signals generates narrow pulse pump light with fixed frequency through the acousto-optic pulse modulator, the narrow pulse pump light is amplified to optical power of more than 20dBm through the erbium-doped optical fiber amplifier, and the amplified optical signals enter a port 1 of the circulator.
4. The pipeline temperature measurement system based on the distributed sensing optical fiber as claimed in claim 3, wherein: the extinction ratio of the acousto-optic pulse modulator is larger than 40 dB.
5. The pipeline temperature measurement system based on the distributed sensing optical fiber as claimed in claim 4, wherein: the continuous detection light generating unit comprises an electromagnetic frequency modulator, a microwave generator, a second polarizer and an isolator;
the electro-optic frequency modulator generates continuous detection light with adjustable frequency shift, the microwave generator generates microwaves for adjusting the frequency shift of the continuous detection light, and the continuous detection light reaches the input end of the first optical switch after passing through the second polarizer and the isolator.
6. The pipeline temperature measurement system based on the distributed sensing optical fiber as claimed in claim 5, wherein: the polarization degrees of the first polarizer and the second polarizer are both less than 5%.
7. The pipeline temperature measurement system based on the distributed sensing optical fiber as claimed in claim 6, wherein: the photoelectric detection unit comprises a photoelectric detector and a digital signal processor;
and the port 2 of the circulator is electrically connected with the input end of the digital signal processor through the photoelectric detector.
8. A pipeline temperature measurement method based on distributed sensing optical fibers is characterized by comprising the following steps: the method comprises the following steps:
s1, building the pipeline temperature measuring system according to claim 1;
s2, emitting continuous detection light to one of the sensing optical fibers through one 1 x 2 optical switch, transmitting the continuous detection light in the sensing optical fibers and transmitting the continuous detection light to a photoelectric detection unit through the other 1 x 2 optical switch, analyzing and knowing Brillouin frequency shift influenced by pressure and temperature by the photoelectric detection unit, gating the continuous detection light to the sensing optical fibers with pressure shielding covers and the photoelectric detection unit by the 1 x 2 optical switch, and analyzing and knowing the Brillouin frequency shift influenced by temperature by the photoelectric detection unit;
s3, the photoelectric detection unit analyzes the two Brillouin frequency shifts, a mathematical equation for measuring the same path and simultaneously laying two groups of sensing optical fibers is established according to the linear relation between the Brillouin frequency shifts and pressure and temperature, and the pressure value of the sensing optical fibers is solved according to the two Brillouin frequency shifts and the mathematical equation measured by the Brillouin analyzer.
9. The method for measuring the temperature of the pipeline based on the distributed sensing optical fiber as claimed in claim 8, wherein: the linear relation between the Brillouin frequency shift and the pressure and temperature in the S3 is as follows: v. ofB＝CcP·P+CvT·T+vB0；
In the formula, vBIs the Brillouin frequency shift, v, of an optical fiber under the influence of pressure and temperatureB0The Brillouin frequency shift of the optical fiber when the pressure and the temperature are zero simultaneously, P is the pressure to be measured, T is the temperature to be measured, CcPIs the coefficient of Brillouin pressure, constant, CvTIs a temperature coefficient and is a constant.
10. The method for measuring the temperature of the pipeline based on the distributed sensing optical fiber as claimed in claim 8, wherein: in the step S3, a mathematical equation for measuring two groups of sensing fibers simultaneously laid on the same path is established according to the linear relationship between the brillouin frequency shift and the pressure and temperature, and the mathematical equation is as follows:
wherein the condition C must be satisfiedvP,1·CvT,2≠CvP,2·CvT,1。
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