CN114942087A - Raman Stokes light intensity dynamic self-calibration distributed temperature detection system and method - Google Patents
Raman Stokes light intensity dynamic self-calibration distributed temperature detection system and method Download PDFInfo
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- CN114942087A CN114942087A CN202210466254.7A CN202210466254A CN114942087A CN 114942087 A CN114942087 A CN 114942087A CN 202210466254 A CN202210466254 A CN 202210466254A CN 114942087 A CN114942087 A CN 114942087A
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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
- G01K11/324—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 Raman scattering
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
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Abstract
The invention relates to the technical field of distributed optical fiber temperature sensing, in particular to a Raman Stokes light intensity dynamic self-calibration distributed temperature detection system and method. It includes: the device comprises a detection optical fiber, a pulse laser, a wavelength division multiplexer, a photoelectric detector and a calculation unit; the detection optical fiber is provided with a reference optical fiber section located in a constant temperature environment, and the calculation unit is used for acquiring the temperature at the measuring point based on the luminous flux of the back anti-Stokes Raman scattering light and the luminous flux of the back anti-Stokes Raman scattering light at any point of the reference optical fiber section, and the luminous flux of the back anti-Stokes Raman scattering light and the luminous flux of the back Stokes Raman scattering light at the measuring point. The method of the invention is realized based on the system. The invention can better improve the accuracy of temperature measurement.
Description
Technical Field
The invention relates to the technical field of distributed optical fiber temperature sensing, in particular to a Raman Stokes light intensity dynamic self-calibration distributed temperature detection system and method.
Background
The distributed optical fiber temperature sensing technology is a sensing technology which is developed in recent years and utilizes the Raman scattering effect in optical fibers to realize real-time and continuous monitoring of spatial temperature distribution in a large range. Compared with the traditional temperature detection method, the distributed optical fiber temperature sensing technology has the advantages of electromagnetic interference resistance, long-distance and large-range temperature monitoring and the like, and is widely applied to the fields of road tunnel safety, oil and gas pipeline leakage, fire monitoring and early warning and the like.
When light is transmitted in the optical fiber, a Raman scattering effect is generated, and Stokes Raman scattered light and anti-Stokes Raman scattered light are generated. In a Distributed optical fiber temperature sensing system (DTS), stokes raman scattering light is mostly used as reference light, anti-stokes light is mostly used as signal light, and a scattered light intensity ratio method is adopted in combination with an optical time domain reflection technology to demodulate and position the temperature of each scattering point.
In order to improve the temperature measurement accuracy of the DTS system, the prior art has conducted a great deal of research and calibration. Such as: in order to reduce the influence of optical fiber dispersion on temperature measurement errors, a light speed correction method, a 3-section Hermite interpolation algorithm, a dispersion compensation translation algorithm and the like are provided; in order to reduce the influence of noise, a Rayleigh noise suppression algorithm, a photoelectric detector dynamic noise suppression method wavelet mode maximum denoising algorithm and the like are provided; in order to solve the Stokes light and anti-Stokes light wavelength related loss and the additional loss generated by the bending of the optical fiber or the change of the environment, a double-light-source correction method, an annular optical fiber structure correction method, a fitting attenuation difference method, temperature self-compensation and the like are provided.
The correction method can effectively reduce the temperature measurement error of the DTS system, but the influence of the temperature response of the Stokes light intensity serving as the reference light on the temperature measurement accuracy is ignored when the DTS system demodulates the temperature by using a scattered light intensity ratio method.
According to researches, when the DTS system measures the temperature of the environment where the optical fiber is located, if the temperature of the measured area rises, the intensity of scattered light in the optical fiber increases along with the rise of the temperature. When the ambient temperature rises by 300 ℃, the anti-stokes light intensity changes by about 237%, and the stokes light intensity also changes by 34%. The local increase in stokes light intensity in the fiber reduces the ratio of anti-stokes light intensity to stokes light intensity in the measured region, resulting in a deviation of the demodulated temperature from the actual temperature.
In order to eliminate the temperature measurement error, the conventional method is to place the whole sensing optical fiber at the same temperature before the temperature measurement is performed by the DTS system to measure the stokes light intensity distribution in the optical fiber, and use the stokes light intensity distribution as the reference light to demodulate the temperature. The method takes fixed Stokes light intensity as reference, and cannot eliminate the influence of light source jitter. If equipment such as a sensing optical fiber and the like is replaced in the measurement process, the Stokes light intensity distribution needs to be measured and calibrated again, and the optical fiber needs to be placed at the same temperature in the measurement and calibration process, so that the calibration condition is difficult to realize in many engineering applications.
Disclosure of Invention
The present invention provides a raman stokes light intensity dynamic self-calibrating distributed temperature detection system that overcomes some or all of the deficiencies of the prior art.
The Raman Stokes light intensity dynamic self-calibration distributed temperature detection system comprises:
a detection optical fiber for deployment at a temperature measurement region;
a pulsed laser for generating laser pulses;
a wavelength division multiplexer for transmitting the laser pulse as incident light to a detection fiber and for filtering backscattered light of the detection fiber to obtain backscattered Stokes Raman light and backscattered anti-Stokes Raman light;
a photodetector for converting the back-stokes Raman scattered light and the back-anti-stokes Raman scattered light into corresponding electrical signals;
the acquisition unit is used for acquiring corresponding signals output by the photoelectric detector; and
the calculating unit is used for calculating the luminous flux of the backward Stokes Raman scattering light and the backward anti-Stokes Raman scattering light at any point of the detection optical fiber according to the signals collected by the collecting unit and calculating and acquiring the detection temperature at any measuring point of the detection optical fiber;
the detection optical fiber has a constant temperature T 0 A reference fiber segment in the environment, a computing unit for calculating a reference fiber segment based onBack anti-stokes Raman scattered light flux at any point of reference fiber segment
And the luminous flux of the back-Stokes Raman scattered light
And the luminous flux of the back-anti-stokes Raman scattered light at the measurement point
And the luminous flux of the back-Stokes Raman scattered light
Acquiring the temperature T at the measuring point; wherein the content of the first and second substances,
wherein k is Boltzmann constant, h is Planckian constant, and Δ v is Raman frequency shift.
By arranging a constant temperature T at the position of the detection optical fiber 0 The reference optical fiber section under the environment can better ensure that the backward Stokes Raman scattering light at the reference optical fiber section is not influenced by temperature, and the calculation of the backward Stokes Raman scattering light at any point of the detection optical fiber can be better realized based on the backward Stokes Raman scattering light at the reference optical fiber section, so that the influence on the temperature measurement accuracy caused by temperature change can be better reduced.
Preferably, the photodetector is a photo avalanche diode. It is possible to preferably convert the back-stokes raman scattered light and the back-anti-stokes raman scattered light into electric signals.
Preferably, the reference optical fiber section is arranged at the first section of the detection optical fiber. It can be preferably facilitated to implement and control.
Based on any one of the systems, the invention also provides a dynamic self-calibration distributed temperature detection method for Raman Stokes light intensity, which comprises the following steps:
step S1, arranging a reference optical fiber section at the position of the detection optical fiber, and arranging the reference optical fiber section in a constant temperature environment;
step S2, obtaining the luminous flux of the back anti-Stokes Raman scattered light at any point of the reference fiber section
And the luminous flux of the back-Stokes Raman scattered light
And the luminous flux of the back-anti-stokes Raman scattered light at the measurement point
And the luminous flux of the back-Stokes Raman scattered light
Step S3, the temperature T at the measurement point is acquired, wherein,
wherein k is Boltzmann constant, h is Planckian constant, and Δ v is Raman frequency shift.
Through steps S1-S3, the influence of temperature variation on the temperature measurement accuracy can be preferably reduced.
Preferably, the luminous flux
And luminous flux
The actual measurement value is obtained after the calculation unit performs conversion according to the corresponding signal acquired by the acquisition unit. Thus can be preferredThe temperature calculation is performed.
Preferably, the luminous flux
And luminous flux
For calculating the value, the calculation value is obtained by the calculation unit according to the following formula,
wherein, the first and the second end of the pipe are connected with each other,
-(α o +α s ) To detect the attenuation coefficient of the optical fiber;
luminous flux
By substituting l ═ l 0 Obtaining luminous flux
By bringing in l ═ l x Obtaining of x The length from the point to be measured to the head end of the detection optical fiber.
Through the above, the intensity of the backward stokes raman scattering light at any point in the detection optical fiber can be calculated based on the intensity of the backward stokes raman scattering light at any point of the reference optical fiber section, and temperature measurement errors caused by temperature response can be avoided due to the fact that the reference optical fiber section is in a constant temperature environment.
Preferably, the attenuation coefficient of the optical fiber is detected as — (. alpha.) o +α s ) Universal jointThe method comprises the following steps:
step SA, constructing the luminous flux of the back Stokes Raman scattered light of each point of the reference fiber segment
And a calculation model of the length L from the corresponding point to the head end of the detection optical fiber,
wherein alpha is o For the average transmission loss of incident light in the detection fiber, alpha s For the average transmission loss of the back-Stokes Raman scattered light in the detection fiber, K S Coefficient of back-Stokes Raman scattering light relative to scattering cross section of optical fiber, S is back scattering factor of detection optical fiber, V S The frequency of the back-stokes raman scattered light,
for the light flux of the incident light into the detection fiber, R s (T) is the temperature modulation function of the back-stokes raman scattered light;
step SB of
Taking L as independent variable as dependent variable, obtaining multiple groups of data of reference optical fiber section, performing curve fitting on the calculation model, and further obtaining attenuation coefficient- (alpha) of the detection optical fiber o +α s )。
By the above, the calculation model can be fitted based on the measured value, and the attenuation coefficient- (α) of the optical fiber can be obtained o +α s )。
Preferably, in step SA, the temperature modulation function R of the back-Stokes Raman scattered light s (T) is a group of,
drawings
FIG. 1 is a schematic diagram of a Raman Stokes light intensity dynamic self-calibration distributed temperature detection system in embodiment 1;
FIG. 2 is a graph showing the intensity distribution of back-stokes Raman scattered light and back-anti-stokes Raman scattered light in the detection optical fiber in example 1;
FIG. 3 is a distribution curve of the intensity of the original Stokes Raman scattered light and the intensity of the Stokes Raman scattered light after exponential fitting in the detection optical fiber in example 1;
FIG. 4 is a temperature measurement curve of measured values when temperature measurements are taken for ambient temperatures of 50 ℃ and 75 ℃ for a conventional DTS system/method and the protocol of example 1;
figure 5 shows the deviation of the temperature measurements for the conventional DTS system/method and the protocol of example 1 when measuring ambient temperatures of 50 c and 75 c.
Detailed Description
For a further understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings and examples. It is to be understood that the examples are illustrative of the invention and not restrictive.
Example 1
As shown in fig. 1, the present embodiment provides a dynamic self-calibration distributed temperature detection system for raman stokes light intensity, and based on the system, the present embodiment also provides a dynamic self-calibration distributed temperature detection method for raman stokes light intensity. The reference optical fiber section is arranged at the position of the detection optical fiber, calculation of the backward Stokes Raman scattering light at any point of the detection optical fiber can be better realized based on the backward Stokes Raman scattering light at the position of the reference optical fiber section, so that the influence of temperature on the backward Stokes Raman scattering light can be better reduced, and the aim of improving the temperature measurement accuracy is fulfilled.
The dynamic self-calibration distributed temperature detection system for Raman Stokes light intensity of the embodiment comprises:
a detection optical fiber for deployment at a temperature measurement region;
a pulsed laser for generating laser pulses;
a wavelength division multiplexer for transmitting the laser pulse as incident light to a detection optical fiber head end and for filtering backscattered light of the detection optical fiber to obtain backscattered Stokes Raman light and backscattered anti-Stokes Raman light;
a photodetector for converting the back-stokes Raman scattered light and the back-anti-stokes Raman scattered light into corresponding electrical signals;
the acquisition unit is used for acquiring corresponding signals output by the photoelectric detector; and
the calculating unit is used for calculating the luminous flux of the backward Stokes Raman scattering light and the backward anti-Stokes Raman scattering light at any point of the detection optical fiber according to the signals collected by the collecting unit and calculating and acquiring the detection temperature at any measuring point of the detection optical fiber;
the detection optical fiber has a constant temperature T 0 A reference fiber segment in the environment, a computing unit for calculating the luminous flux of back-to-back anti-Stokes Raman scattered light based on the luminous flux at any point of the reference fiber segment
And the luminous flux of the back-Stokes Raman scattered light
And the luminous flux of the back-anti-stokes Raman scattered light at the measurement point
And the luminous flux of the back-Stokes Raman scattered light
Acquiring the temperature T at the measuring point; wherein the content of the first and second substances,
wherein k is Boltzmann constant, h is Planckian constant, and Δ v is Raman frequency shift.
By arranging a constant temperature T at the position of the detection optical fiber 0 The reference optical fiber section under the environment can better ensure that the backward Stokes Raman scattering light at the reference optical fiber section is not influenced by temperature, and the calculation of the backward Stokes Raman scattering light at any point of the detection optical fiber can be better realized based on the backward Stokes Raman scattering light at the reference optical fiber section, so that the influence on the temperature measurement accuracy caused by temperature change can be better reduced.
In this embodiment, the photodetector is an avalanche photodiode. It is possible to preferably convert the back-stokes raman scattered light and the back-anti-stokes raman scattered light into electric signals.
In this embodiment, the reference optical fiber segment is disposed at the first segment of the detection optical fiber. It can be preferably facilitated to implement and control.
Based on the system of the embodiment, the embodiment also provides a dynamic self-calibration distributed temperature detection method for the Raman Stokes light intensity, which comprises the following steps:
step S1, setting a reference optical fiber section at the position of the detection optical fiber, and setting the reference optical fiber section in a constant temperature environment;
step S2, obtaining the luminous flux of the back anti-Stokes Raman scattered light at any point of the reference fiber section
And the luminous flux of the back-Stokes Raman scattered light
And the luminous flux of the back-anti-stokes Raman scattered light at the measurement point
And the luminous flux of the back-Stokes Raman scattered light
Step S3, the temperature T at the measurement point is acquired, wherein,
wherein k is Boltzmann constant, h is Planckian constant, and Δ v is Raman frequency shift.
Through steps S1-S3, the influence of temperature variation on the temperature measurement accuracy can be preferably reduced.
In the embodiment, the backward stokes raman scattering light of any point at the detection optical fiber can be solved based on the attenuation coefficient by referring to the backward stokes raman scattering light in the optical fiber section, so that the intensity distribution of the backward stokes raman scattering light is not required to be obtained by placing the whole detection optical fiber at the same temperature, the operation is convenient, and the influence of light source jitter on calibration can be better eliminated.
In this example, the luminous flux
And luminous flux
The actual measurement value is obtained after the calculation unit performs conversion according to the corresponding signal acquired by the acquisition unit. The calculation of the temperature can be preferably performed.
In this example, the luminous flux
And luminous flux
For calculating the value, the calculation value is obtained by the calculation unit according to the following formula,
wherein the content of the first and second substances,
-(α o +α s ) To detect the attenuation coefficient of the optical fiber;
luminous flux
By substituting l ═ l 0 Obtaining luminous flux
By bringing in l x Obtaining of x The length from the point to be measured to the head end of the detection optical fiber.
Through the above, the intensity of the backward stokes raman scattering light at any point in the detection optical fiber can be calculated based on the intensity of the backward stokes raman scattering light at any point of the reference optical fiber section, and temperature measurement errors caused by temperature response can be avoided due to the fact that the reference optical fiber section is in a constant temperature environment.
This is because, in a uniform, unbroken optical fiber, the increase in scattered light signal along the length of the fiber decays exponentially, so that by the above formula it can be obtained that any point of the detection fiber is at the reference temperature (i.e. the ambient temperature T at which the reference fiber section is located) 0 ) The light flux of the back-stokes raman scattering light is calculated by using the estimated value as the reference light and using the above-mentioned ratio method to calculate the temperature, so that the influence of the local increase of the intensity of the back-stokes raman scattering light caused by the temperature increase on the temperature detection accuracy can be eliminated.
In this embodiment, the attenuation coefficient (. alpha.) of the detection fiber o +α s ) The method comprises the following steps:
step SA, constructing the luminous flux of the back Stokes Raman scattered light of each point of the reference fiber segment
And a calculation model of the length L from the corresponding point to the head end of the detection optical fiber,
wherein alpha is o For the average transmission loss of incident light in the detection fiber, alpha s For the average transmission loss of the back-Stokes Raman scattered light in the detection fiber, K S Coefficient of back-Stokes Raman scattering light relative to scattering cross section of optical fiber, S is back scattering factor of detection optical fiber, V S The frequency of the back-stokes raman scattered light,
for the light flux of the incident light into the detection fiber, R s (T) is the temperature modulation function of the back-stokes raman scattered light;
step SB of
Taking L as independent variable as dependent variable, obtaining multiple groups of data of reference optical fiber section, performing curve fitting on the calculation model, and further obtaining attenuation coefficient- (alpha) of the detection optical fiber o +α s )。
By the above, the calculation model can be fitted based on the measured value, and the attenuation coefficient- (α) of the optical fiber can be obtained o +α s )。
In this embodiment, in step SA, the temperature modulation function R of the backward stokes raman scattered light s (T) is a group of,
it is known that for a DTS system (distributed fiber optic temperature sensing system), it demodulates the temperature with the ratio of the intensities of the signal light (back-to-back stokes raman scattered light) and the reference light (back-to-back stokes raman scattered light).
The luminous flux of the back-stokes raman scattered light generated by the laser pulse (i.e. incident light) in the detection fiber
And the luminous flux of the back-ward anti-Stokes Raman scattered light
Can be expressed as:
formula (1):
formula (2):
wherein the subscripts S, AS, O denote parameters relating to the back-Stokes Raman scattered light, the back-anti-Stokes Raman scattered light, and the incident light, respectively,
representing the luminous flux, K is the coefficient related to the scattering cross section of the fiber, S is the fiber backscattering factor, V is the frequency of the scattered photons,
is the luminous flux of a laser pulse incident on the fiber, alpha is the average transmission loss of light in the detection fiber, L is the distance that the laser pulse travels within the fiber, and R (T) is a function of temperature modulation.
Wherein the content of the first and second substances,
formula (3):
formula (4):
wherein k is Boltzmann constant, h is Planckian constant, Deltav is Raman frequency shift quantity, and T is the temperature of the environment where the corresponding point of the detection optical fiber is located.
The light flux of the backward Stokes Raman scattering light of each point of the reference optical fiber section can be preferably obtained by carrying out logarithm operation on the formula (1)
A calculation model of the length L from the corresponding point to the head end of the detection optical fiber; through the calculation model, the expression of the intensity distribution of the backward Stokes Raman scattering light of the reference optical fiber section can be preferably realized.
This embodiment is a specific example, the pulse laser can generate laser pulse with 10ns pulse width and 20KHz repetition frequency, and the laser pulse can enter the detection fiber as incident light through 1 × 3 wavelength division multiplexer with 35dB-40dB isolation. The laser pulse can generate a Raman scattering effect on the detection optical fiber, and further generates Stokes Raman scattering light and anti-Stokes Raman scattering light; the backward Stokes Raman scattering light and the anti-Stokes Raman scattering light can realize photoelectric conversion and signal amplification at the photoelectric detector after being filtered by the wavelength division multiplexer; and the acquisition unit can adopt a dual-channel high-speed acquisition card, can acquire the signal processed by the photoelectric detector and transmits the signal to the calculation unit for processing and storage. Thereby preferably achieving distributed measurement of temperature.
In order to verify the system and method provided by the embodiment, in the embodiment, the total length of the detection optical fiber is set to 1800 m; referring to fig. 1, the "I" section of the detection optical fiber is a reference optical fiber section with a length of 90m, which can be disposed in a water bath box, for example, so as to better ensure a constant temperature environment; the section III of the detection optical fiber can be used as a test optical fiber section, the length of the test optical fiber section is 90m, and the test optical fiber section can be arranged in an incubator, so that the environmental temperature of the test optical fiber section can be preferably controlled; the section II and the rest of the detection optical fiber are set as common optical fiber sections.
In fig. 2, the intensity distributions of the back-stokes raman scattered light and the back-anti-stokes raman scattered light in the detection fiber at different temperatures are given.
In fig. 2, the temperature of the "I" section of the detection optical fiber is 35 ℃, the temperatures of the "II" section and the "IV" section of the detection optical fiber are room temperature, and in the "III" section of the detection optical fiber, "- - -" represents an actual measurement value of the stokes raman scattered light intensity at a temperature of 50 ℃, and "· - ·" represents an actual measurement value of the stokes raman scattered light intensity at a temperature of 75 ℃. "… …" represents the actual measurement of the anti-stokes raman scattered light intensity at a temperature of 50 deg.c, "-" represents the actual measurement of the anti-stokes raman scattered light intensity at a temperature of 75 deg.c.
As can be seen from FIG. 2, after the temperature of the section "III" of the detection optical fiber rises, the anti-Stokes light intensity is obviously increased, and the Stokes light intensity is also obviously increased.
In fig. 3, the distribution curves of the intensity of the original stokes raman scattered light (i.e., measured value) and the intensity of the stokes raman scattered light after exponential fitting (i.e., calculated value) in the detection fiber are given.
In fig. 3, "□" and "o" indicate measured values of stokes raman scattering light intensity in the detection optical fiber, the temperature of the "I" section of the detection optical fiber is 35 ℃, the temperatures of the "II" section and the "IV" section of the detection optical fiber are room temperature, in the "III" section of the detection optical fiber, "□" indicates a temperature of 50 ℃, and "o" indicates a temperature of 75 ℃. "-" denotes a distribution curve of the intensity of the stokes raman scattered light (i.e., a calculated value) after being exponentially fitted with an actually measured value of the stokes raman scattered light intensity of the detection optical fiber "I" section "□". "-" indicates a distribution curve of the intensity of stokes raman scattered light (i.e., a calculated value) after being exponentially fitted to an actual measurement value of the stokes raman scattered light intensity of the section "I" o "of the detection optical fiber.
As can be seen from fig. 3, the environments of the "I" sections of the detection fibers are consistent, but under the influence of the disturbance of the light source, the actually measured curves of the stokes raman scattering light intensities of the "I" sections of the detection fibers do not coincide.
Stokes light intensity distribution in the whole optical fiber is obtained by utilizing the Stokes light intensity distribution simulation in the reference optical fiber acquired in real time, dynamic self-calibration is carried out on Stokes light, the goodness fit between an exponential fit Stokes light intensity curve and an original curve is high, and the influences of light source disturbance and temperature change of the constant temperature box are eliminated.
In fig. 4, a temperature measurement curve of measured values when temperature measurement is performed for ambient temperatures of 50 ℃ and 75 ℃ for the conventional DTS system/method and the scheme of the present embodiment is given.
In fig. 4, "□" represents the measurement of the conventional DTS system/method at an ambient temperature of 50 ℃, and "Δ" represents the measurement of the solution of the present embodiment at an ambient temperature of 50 ℃; ". o" indicates the measurement value of the conventional DTS system at an ambient temperature of 75 c,
represents the measurements of the protocol of this example at an ambient temperature of 75 ℃.
As can be seen from fig. 4, the conventional DTS system/method deviates more from the actual value, and the solution of the embodiment can have more accurate measurement value.
In fig. 5, the deviation of the temperature measurement when the ambient temperature of 50 ℃ and 75 ℃ is measured is given for the conventional DTS system/method and the solution of the present embodiment.
In fig. 5, "□" represents the deviation value of the conventional DTS system/method at an ambient temperature of 50 ℃, and "Δ" represents the deviation value of the scheme of the present embodiment at an ambient temperature of 50 ℃; ". o" indicates a deviation value of the conventional DTS system at an ambient temperature of 75 c,
shows the deviation of the protocol of this example at an ambient temperature of 75 c.
As can be seen from fig. 5, the deviation of the conventional DTS system/method is about 2.5 ℃ at an ambient temperature of 50 ℃, and the deviation of the embodiment is about 1.5 ℃ at an ambient temperature of 50 ℃; the conventional DTS system/method has a deviation of about 7 ℃ at an ambient temperature of 75 ℃, and the protocol of the present example has a deviation of about 3.5 ℃ at an ambient temperature of 75 ℃. Therefore, it can be known that the deviation of the DTS system increases with the increase of the temperature, and the deviation can be better suppressed by the solution in the embodiment, so that the accuracy is better.
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Claims (8)
1. The distributed temperature detection system of Raman stokes light intensity developments self calibration, it includes:
a detection fiber for deployment at a temperature measurement region;
a pulsed laser for generating laser pulses;
a wavelength division multiplexer for transmitting the laser pulse as incident light to a detection fiber and for filtering backscattered light of the detection fiber to obtain backscattered Stokes Raman light and backscattered anti-Stokes Raman light;
a photodetector for converting the back-stokes Raman scattered light and the back-anti-stokes Raman scattered light into corresponding electrical signals;
the acquisition unit is used for acquiring corresponding signals output by the photoelectric detector; and
the calculating unit is used for calculating the luminous flux of the backward Stokes Raman scattering light and the backward anti-Stokes Raman scattering light at any point of the detection optical fiber according to the signals collected by the collecting unit and calculating and acquiring the detection temperature at any measuring point of the detection optical fiber;
the detection optical fiber has a constant temperature T 0 A reference fiber segment in the environment, a computing unit for calculating the luminous flux of the back-to-back anti-Stokes Raman scattering light at any point of the reference fiber segment
And the luminous flux of the back-Stokes Raman scattered light
And the luminous flux of the back-anti-stokes Raman scattered light at the measurement point
And the luminous flux of the back-Stokes Raman scattered light
Acquiring the temperature T at the measuring point; wherein the content of the first and second substances,
wherein k is Boltzmann constant, h is Planckian constant, and Δ v is Raman frequency shift.
2. The raman stokes light intensity dynamic self-calibrating distributed temperature detection system of claim 1, wherein: the photodetector is a photo avalanche diode.
3. The raman stokes light intensity dynamic self-calibrating distributed temperature detection system of claim 1, wherein: the reference optical fiber section is arranged at the first section of the detection optical fiber.
4. The Raman Stokes light intensity dynamic self-calibration distributed temperature detection method comprises the following steps:
step S1, setting a reference optical fiber section at the position of the detection optical fiber, and setting the reference optical fiber section in a constant temperature environment;
step S2, obtaining the luminous flux of the back anti-Stokes Raman scattered light at any point of the reference fiber section
And the luminous flux of the back-Stokes Raman scattered light
And the luminous flux of the back-anti-stokes Raman scattered light at the measurement point
And the luminous flux of the back-Stokes Raman scattered light
Step S3, the temperature T at the measurement point is acquired, wherein,
wherein k is Boltzmann constant, h is Planckian constant, and Δ v is Raman frequency shift.
5. The Raman Stokes light intensity dynamic self-calibration distributed temperature detection method according to claim 4, characterized in that: luminous flux
And luminous flux
Is an actual measurement value, the actual measurement value is a meterAnd the calculation unit is used for converting the corresponding signals acquired by the acquisition unit and then acquiring the converted signals.
6. The Raman Stokes light intensity dynamic self-calibration distributed temperature detection method according to claim 5, characterized in that: luminous flux
And luminous flux
For calculating the value, the calculation value is obtained by the calculation unit according to the following formula,
wherein, the first and the second end of the pipe are connected with each other,
-(α o +α s ) To detect the attenuation coefficient of the optical fiber;
luminous flux
By substituting l ═ l 0 Obtaining luminous flux
By bringing in l ═ l x Obtaining of x The length from the point to be measured to the head end of the detection optical fiber.
7. The Raman Stokes light intensity dynamic self-calibration distributed temperature detection method according to claim 6The method is characterized in that: attenuation coefficient of detecting optical fiber o +α s ) The method comprises the following steps:
step SA, constructing the luminous flux of the back Stokes Raman scattered light of each point of the reference fiber segment
And a calculation model of the length L from the corresponding point to the head end of the detection optical fiber,
wherein alpha is o For the average transmission loss of incident light in the detection fiber, alpha s For the average transmission loss of the back-Stokes Raman scattered light in the detection fiber, K S Coefficient of back-Stokes Raman scattering light relative to scattering cross section of optical fiber, S is back scattering factor of detection optical fiber, V S The frequency of the back-stokes raman scattered light,
for the light flux of the incident light into the detection fiber, R s (T) is the temperature modulation function of the back-stokes raman scattered light;
step SB of
Taking L as independent variable as dependent variable, obtaining multiple groups of data of reference optical fiber section, performing curve fitting on the calculation model, and further obtaining attenuation coefficient- (alpha) of the detection optical fiber o +α s )。
8. The Raman Stokes light intensity dynamic self-calibration distributed temperature detection method according to claim 7, characterized in that: in step SA, the temperature modulation function R of the back-Stokes Raman scattered light s (T) is a group of,
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115452202A (en) * | 2022-11-10 | 2022-12-09 | 中国空气动力研究与发展中心设备设计与测试技术研究所 | High-temperature thermocouple calibration method based on coherent anti-Stokes Raman scattering spectrum |
| CN115585910A (en) * | 2022-09-21 | 2023-01-10 | 桐乡泰爱斯环保能源有限公司 | Calibration method of temperature calibration system for distributed optical fiber temperature measurement system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115585910A (en) * | 2022-09-21 | 2023-01-10 | 桐乡泰爱斯环保能源有限公司 | Calibration method of temperature calibration system for distributed optical fiber temperature measurement system |
| CN115452202A (en) * | 2022-11-10 | 2022-12-09 | 中国空气动力研究与发展中心设备设计与测试技术研究所 | High-temperature thermocouple calibration method based on coherent anti-Stokes Raman scattering spectrum |
| CN115452202B (en) * | 2022-11-10 | 2023-01-31 | 中国空气动力研究与发展中心设备设计与测试技术研究所 | High-temperature thermocouple calibration method based on coherent anti-stokes Raman scattering spectrum |
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