CN114942087B - Raman Stokes light intensity dynamic self-calibration distributed temperature detection system and method - Google Patents
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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 a Raman Stokes light intensity dynamic self-calibration distributed temperature detection method. It comprises the following steps: 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 positioned in a constant temperature environment, and the calculation unit is used for acquiring the temperature at the measurement point based on the luminous flux of the back anti-Stokes Raman scattered light and the luminous flux of the back anti-Stokes Raman scattered light at any point of the reference optical fiber section and the luminous flux of the back anti-Stokes Raman scattered light and the luminous flux of the back Stokes Raman scattered light at the measurement 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 a Raman Stokes light intensity dynamic self-calibration distributed temperature detection 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 the optical fiber to realize real-time continuous monitoring of the 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 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.
The raman scattering effect occurs when light is transmitted in an optical fiber, producing stokes raman scattered light and anti-stokes raman scattered light. The distributed optical fiber temperature sensing system (Distributed temperature fiber sensors, DTS) uses Stokes Raman scattered light as reference light and anti-Stokes light as signal light, and adopts a scattered light intensity ratio method to combine an optical time domain reflection technology to perform temperature demodulation and positioning on each scattering point.
In order to improve the temperature measurement accuracy of the DTS system, the prior art has been subjected to a great deal of research and correction. 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 wavelet mode maximum denoising algorithm of a dynamic noise suppression method of a photoelectric detector and the like are provided; in order to solve the problems of the correlation loss of Stokes light and anti-Stokes light wavelength and the additional loss caused by the bending of the optical fiber or the change of the environment where the optical fiber is positioned, a dual light source correction method, a ring-shaped optical fiber structure correction method, a fitting attenuation difference method, a temperature self-compensation method 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 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.
It is found that when the DTS system performs temperature measurement on the environment where the optical fiber is located, if the temperature of the detected area increases, the scattered light intensity in the optical fiber increases with the increase of the temperature. When the ambient temperature was raised by 300 ℃, the anti-stokes light intensity was changed by about 237% while the stokes light intensity was also changed by 34%. The local increase in stokes light intensity in the fiber causes a decrease in the ratio of anti-stokes light intensity to stokes light intensity in the region being measured, resulting in a deviation of the demodulated temperature from the actual temperature.
In order to eliminate the temperature measurement error, the traditional method is to place the whole sensing optical fiber in the same temperature to measure the Stokes light intensity distribution in the optical fiber before the temperature measurement is carried out by the DTS system, and the Stokes light intensity distribution is taken as a reference light to demodulate the temperature. The method takes fixed Stokes light intensity as a reference, and cannot eliminate the influence of light source jitter. If equipment such as sensing optical fibers is replaced in the measuring process, the Stokes light intensity distribution needs to be measured and calibrated again, and the optical fibers need to be placed at the same temperature in the measuring and calibrating process, so that the calibrating condition is difficult to realize in many engineering applications.
Disclosure of Invention
The invention provides a Raman Stokes light intensity dynamic self-calibration distributed temperature detection system, which can overcome certain or some defects in the prior art.
The Raman Stokes light intensity dynamic self-calibration distributed temperature detection system according to the invention comprises:
A detection fiber for deployment at the temperature measurement region;
a pulse laser for generating a laser pulse;
a wavelength division multiplexer for transmitting the laser pulse as incident light to the detection optical fiber and for filtering the back-scattered light of the detection optical fiber to obtain back-stokes raman scattered light and back-anti-stokes raman scattered 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 calculation unit is used for calculating the luminous fluxes of the back stokes Raman scattered light and the back anti-stokes Raman scattered light at any point of the detection optical fiber according to the signals acquired by the acquisition unit and calculating and acquiring the detection temperature at any measurement point of the detection optical fiber;
the detection optical fiber is provided with a reference optical fiber section in a constant temperature T 0 environment, and the calculation unit is used for calculating the luminous flux of the back anti-Stokes Raman scattered light at any point of the reference optical fiber section And luminous flux/>, of back stokes raman scattered lightAnd the luminous flux of the back anti-stokes raman scattered light at the measurement pointAnd luminous flux/>, of back stokes raman scattered lightAcquiring the temperature T at a measuring point; wherein,
Where k is a boltzmann constant, h is a planck constant, and Δv is a raman shift amount.
The reference optical fiber section positioned in the constant temperature T 0 environment is arranged at the detection optical fiber, so that the back Stokes Raman scattered light at the reference optical fiber section can be better prevented from being influenced by temperature, and the calculation of the back Stokes Raman scattered light at any point of the detection optical fiber can be better realized based on the back Stokes Raman scattered 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. The back stokes raman scattered light and the back anti-stokes raman scattered light can be preferably converted into electrical signals.
Preferably, the reference optical fiber section is provided at the first section of the detection optical fiber. Thus, the implementation and control can be preferably facilitated.
Based on any one of the above systems, the invention also provides a Raman Stokes light intensity dynamic self-calibration distributed temperature detection method, which comprises the following steps:
s1, setting a reference optical fiber section at a 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 optical fiber section And luminous flux/>, of back stokes raman scattered lightAnd luminous flux/>, of back anti-stokes raman scattered light at the measurement pointAnd luminous flux of back stokes raman scattered light
Step S3, a temperature T at the measurement point is acquired, wherein,
Where k is a boltzmann constant, h is a planck constant, and Δv is a raman shift amount.
Through the steps S1-S3, the influence on the temperature measurement accuracy caused by temperature change can be reduced.
Preferably, the luminous fluxAnd luminous flux/>The actual measurement value is obtained after the calculation unit converts according to the corresponding signals acquired by the acquisition unit. So that the calculation of the temperature can be preferably performed.
Preferably, the luminous fluxAnd luminous flux/>For the calculated value, the calculated value is calculated and obtained by a calculating unit according to the following formula,
Wherein,
For the measured value of the luminous flux of the back stokes raman scattered light at a further arbitrary point of the reference optical fiber segment, l 01 is the length from the further arbitrary point to the head end of the detection optical fiber;
- (α o+αs) is the attenuation coefficient of the detection fiber;
Luminous flux Obtained by substituting l=l 0, luminous flux/>Obtained by bringing in l=l x, l x is the length from the point to be measured to the head end of the detection fiber.
By the method, the intensity of the back Stokes Raman scattered light at any point in the detection optical fiber can be calculated based on the intensity of the back Stokes Raman scattered light at any point in the reference optical fiber section, and the temperature measurement error caused by the response to temperature can be avoided better because the reference optical fiber section is in a constant temperature environment.
Preferably, the attenuation coefficient- (α o+αs) of the detection fiber is obtained by:
step SA, constructing luminous flux of back Stokes Raman scattered light of each point of the reference fiber segment And a calculation model from the corresponding point to the length L of the head end of the detection optical fiber,
Wherein alpha o is the average transmission loss of incident light in the detection optical fiber, alpha s is the average transmission loss of back stokes raman scattered light in the detection optical fiber, K S is the coefficient of the back stokes raman scattered light related to the scattering cross section of the optical fiber, S is the back scattering factor of the detection optical fiber, V S is the frequency of the back stokes raman scattered light,R s (T) is the temperature modulation function of the back Stokes Raman scattered light for the luminous flux of the incident light into the detection fiber;
step SB, by And taking L as an independent variable to obtain multiple groups of data of the reference optical fiber section, and performing curve fitting on the calculation model to obtain the attenuation coefficient- (alpha o+αs) of the detection optical fiber.
By the method, the calculation model can be fitted based on the actual measurement value, so that the attenuation coefficient- (alpha o+αs) of the optical fiber can be obtained.
Preferably, in step SA, the temperature modulation function R s (T) of the backscattered Stokes Raman light is,
Drawings
FIG. 1 is a schematic diagram of a dynamic self-calibrating distributed temperature detection system for Raman Stokes light intensity in example 1;
FIG. 2 is an intensity distribution of the back Stokes Raman scattered light and the back anti-Stokes Raman scattered light detected in the optical fiber in example 1;
FIG. 3 is a distribution curve of the intensity of original Stokes Raman scattered light and the intensity of Stokes Raman scattered light after exponential fitting in the detection fiber in example 1;
FIG. 4 is a graph of measured values of the conventional DTS system/method versus the ambient temperature of 50℃and 75℃for the embodiment of example 1;
Fig. 5 is a graph of the temperature bias of the conventional DTS system/method versus the embodiment of example 1 when measuring ambient temperatures of 50 c and 75 c.
Detailed Description
For a further understanding of the present invention, the present invention will be described in detail with reference to the drawings and examples. It is to be understood that the examples are illustrative of the present invention and are not intended to be limiting.
Example 1
As shown in fig. 1, this embodiment provides a raman stokes light intensity dynamic self-calibration distributed temperature detection system, and based on this system, this embodiment also provides a raman stokes light intensity dynamic self-calibration distributed temperature detection method. According to the method, the reference optical fiber section is arranged at the detection optical fiber, the calculation of the back Stokes Raman scattered light at any point of the detection optical fiber can be better realized based on the back Stokes Raman scattered light at the reference optical fiber section, so that the influence of temperature on the back Stokes Raman scattered light can be better reduced, and the aim of improving the temperature measurement accuracy is fulfilled.
The raman stokes light intensity dynamic self-calibration distributed temperature detection system of the embodiment comprises:
A detection fiber for deployment at the temperature measurement region;
a pulse laser for generating a laser pulse;
The wavelength division multiplexer is used for transmitting the laser pulse as incident light to the head end of the detection optical fiber and filtering the back scattered light of the detection optical fiber to obtain back Stokes Raman scattered light and back anti-Stokes Raman scattered 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 calculation unit is used for calculating the luminous fluxes of the back stokes Raman scattered light and the back anti-stokes Raman scattered light at any point of the detection optical fiber according to the signals acquired by the acquisition unit and calculating and acquiring the detection temperature at any measurement point of the detection optical fiber;
the detection optical fiber is provided with a reference optical fiber section in a constant temperature T 0 environment, and the calculation unit is used for calculating the luminous flux of the back anti-Stokes Raman scattered light at any point of the reference optical fiber section And luminous flux/>, of back stokes raman scattered lightAnd the luminous flux of the back anti-stokes raman scattered light at the measurement pointAnd luminous flux/>, of back stokes raman scattered lightAcquiring the temperature T at a measuring point; wherein,
Where k is a boltzmann constant, h is a planck constant, and Δv is a raman shift amount.
The reference optical fiber section positioned in the constant temperature T 0 environment is arranged at the detection optical fiber, so that the back Stokes Raman scattered light at the reference optical fiber section can be better prevented from being influenced by temperature, and the calculation of the back Stokes Raman scattered light at any point of the detection optical fiber can be better realized based on the back Stokes Raman scattered 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 a photo avalanche diode. The back stokes raman scattered light and the back anti-stokes raman scattered light can be preferably converted into electrical signals.
In this embodiment, the reference optical fiber section is disposed at the first section of the detection optical fiber. Thus, the implementation and control can be preferably facilitated.
Based on the system of the embodiment, the embodiment also provides a dynamic self-calibration distributed temperature detection method for the light intensity of the Raman Stokes, which comprises the following steps:
s1, setting a reference optical fiber section at a 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 optical fiber section And luminous flux/>, of back stokes raman scattered lightAnd luminous flux/>, of back anti-stokes raman scattered light at the measurement pointAnd luminous flux of back stokes raman scattered light
Step S3, a temperature T at the measurement point is acquired, wherein,
Where k is a boltzmann constant, h is a planck constant, and Δv is a raman shift amount.
Through the steps S1-S3, the influence on the temperature measurement accuracy caused by temperature change can be reduced.
In this embodiment, the back stokes raman scattered light at any point at the detecting optical fiber can be solved based on the attenuation coefficient by referring to the back stokes raman scattered light in the optical fiber section, so that the whole detecting optical fiber is not required to be placed at the same temperature to obtain the intensity distribution of the back stokes raman scattered light, the operation is convenient, and the influence of light source jitter on calibration can be eliminated.
In the present embodiment, the luminous fluxAnd luminous flux/>The actual measurement value is obtained after the calculation unit converts according to the corresponding signals acquired by the acquisition unit. So that the calculation of the temperature can be preferably performed.
In the present embodiment, the luminous fluxAnd luminous flux/>For the calculated value, the calculated value is calculated and obtained by a calculating unit according to the following formula,
Wherein,
For the measured value of the luminous flux of the back stokes raman scattered light at a further arbitrary point of the reference optical fiber segment, l 01 is the length from the further arbitrary point to the head end of the detection optical fiber;
- (α o+αs) is the attenuation coefficient of the detection fiber;
Luminous flux Obtained by substituting l=l 0, luminous flux/>Obtained by bringing in l=l x, l x is the length from the point to be measured to the head end of the detection fiber.
By the method, the intensity of the back Stokes Raman scattered light at any point in the detection optical fiber can be calculated based on the intensity of the back Stokes Raman scattered light at any point in the reference optical fiber section, and the temperature measurement error caused by the response to temperature can be avoided better because the reference optical fiber section is in a constant temperature environment.
This is because, in a uniform, unbroken optical fiber, the scattered light signal decays exponentially along the increase in the length of the optical fiber, so that by the above formula, the luminous flux of the back stokes raman scattered light when any point of the detected optical fiber is at the reference temperature (i.e., the ambient temperature T 0 where the reference optical fiber section is located) can be obtained, and by taking this estimated value as the reference light, and performing the temperature calculation by using the above-mentioned ratio method, the influence on the temperature detection accuracy caused by the local increase in the intensity of the stokes raman scattered light due to the temperature increase can be preferably eliminated.
In this embodiment, the attenuation coefficient- (α o+αs) of the detection fiber is obtained by:
step SA, constructing luminous flux of back Stokes Raman scattered light of each point of the reference fiber segment And a calculation model from the corresponding point to the length L of the head end of the detection optical fiber,
Wherein alpha o is the average transmission loss of incident light in the detection optical fiber, alpha s is the average transmission loss of back stokes raman scattered light in the detection optical fiber, K S is the coefficient of the back stokes raman scattered light related to the scattering cross section of the optical fiber, S is the back scattering factor of the detection optical fiber, V S is the frequency of the back stokes raman scattered light,R s (T) is the temperature modulation function of the back Stokes Raman scattered light for the luminous flux of the incident light into the detection fiber;
step SB, by And taking L as an independent variable to obtain multiple groups of data of the reference optical fiber section, and performing curve fitting on the calculation model to obtain the attenuation coefficient- (alpha o+αs) of the detection optical fiber.
By the method, the calculation model can be fitted based on the actual measurement value, so that the attenuation coefficient- (alpha o+αs) of the optical fiber can be obtained.
In this embodiment, in step SA, the temperature modulation function R s (T) of the backscattered Stokes Raman light is,
It is known that for a DTS system (distributed fiber temperature sensing system) it demodulates the temperature by the ratio of the intensities of the signal light (back anti-stokes raman scattered light) and the reference light (back stokes raman scattered light).
Light flux of back stokes raman scattered light generated by laser pulse (i.e., incident light) in detection fiberAnd luminous flux/>, of back anti-stokes raman scattered lightCan be expressed as:
Formula (1):
Formula (2):
Wherein the subscripts S, AS, O denote parameters related to the back stokes Raman scattered light, the back anti-stokes Raman scattered light, and the incident light, respectively, Represents the luminous flux, K is the coefficient related to the scattering cross section of the fiber, S is the back scattering factor of the fiber, V is the frequency of scattered photons,/>For the luminous flux of the laser pulse incident on the fiber, α is the average transmission loss of light in the detection fiber, L is the distance the laser pulse travels within the fiber, and R (T) is the temperature modulation function.
Wherein,
Equation (3):
Equation (4):
where k is a boltzmann constant, h is a planck constant, Δv is a raman shift, and T is the temperature of the environment where the corresponding point of the detection fiber is located.
The luminous flux of the back Stokes Raman scattered light of each point of the reference optical fiber section can be preferably obtained by carrying out the logarithmic operation of the formula (1)The calculation model is used for calculating 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 back Stokes Raman scattered light of the reference optical fiber section can be preferably realized.
This embodiment is a specific embodiment, and the pulse laser can generate a laser pulse with a pulse width of 10ns and a repetition frequency of 20KHz, and the laser pulse can enter the detection optical fiber as incident light through a1×3 wavelength division multiplexer with an isolation of 35dB-40 dB. The laser pulse can generate a Raman scattering effect in the detection optical fiber, so that Stokes Raman scattered light and anti-Stokes Raman scattered light are generated; the backward Stokes Raman scattered light and the anti-Stokes Raman scattered light can be filtered by a wavelength division multiplexer and then subjected to photoelectric conversion and signal amplification at a photoelectric detector; the acquisition unit can adopt a dual-channel high-speed acquisition card, can acquire signals processed by the photoelectric detector, and transmits the signals to the computing unit for processing and storage. And further, distributed measurement of temperature can be preferably realized.
In order to verify the system and method provided in this embodiment, the total length of the detection fiber is set to 1800m; referring to fig. 1, the "I" section of the detection fiber is a reference fiber section, the length of which is 90m, which can be set in, for example, a water bath tank, so that the constant temperature environment can be preferably ensured; the 'III' section of the detection optical fiber can be used as a test optical fiber section, the length of the 'III' section is 90m, and the 'III' section can be arranged in an incubator, so that the environment temperature of the test optical fiber section can be controlled better; the "II" section of the detection fiber and the remaining portion are set as the ordinary fiber section.
In fig. 2, the intensity distribution of the back stokes raman scattered light and the back anti-stokes raman scattered light in the detection fiber at different temperatures is given.
In fig. 2, the temperature of the "I" section of the detection fiber is 35 ℃, the temperatures of the "II" section and the "IV" section of the detection fiber are room temperature, and in the "III" section of the detection fiber, "- -" indicates the measured value of the intensity of stokes raman scattering at 50 ℃, and "· - ·" indicates the measured value of the intensity of stokes raman scattering at 75 ℃. "… …" represents the measured value of the intensity of anti-Stokes Raman scattering at a temperature of 50℃and "-represents the measured value of the intensity of anti-Stokes Raman scattering at a temperature of 75 ℃.
As can be seen from FIG. 2, after the temperature of the "III" section of the detection fiber increases, the anti-Stokes light intensity increases significantly, as does the Stokes light intensity.
In fig. 3, a distribution curve of the intensity of original stokes raman scattered light (i.e., measured value) in the detection fiber and the intensity of stokes raman scattered light after exponential fitting (i.e., calculated value) is given.
In fig. 3, "ζ" and "ζ" represent measured values of stokes raman scattered light intensity in the detection fiber, the temperature of the "I" section of the detection fiber was 35 ℃, the temperatures of the "II" section and the "IV" section of the detection fiber were room temperature, and "ζ" represents 50 ℃ and "ζ" represents 75 ℃. "represents a distribution curve of the intensity (i.e., calculated value) of stokes raman scattered light after exponential fitting according to the measured value of stokes raman scattered light intensity of the detection fiber" I "segment" ≡ ". "-" indicates a distribution curve of the intensity (i.e., calculated value) of stokes raman scattered light after exponential fitting according to the measured value of stokes raman scattered light intensity of the detection fiber "I" segment ".
As can be seen from fig. 3, the environment of the section "I" of the detection optical fiber is consistent, but the actual measurement curve of the stokes raman scattering light intensity of the section "I" of the detection optical fiber is not coincident under the influence of the disturbance of the light source.
The Stokes light intensity distribution of the whole optical fiber is obtained by simulating the Stokes light intensity distribution in the reference optical fiber acquired in real time, dynamic self-calibration is carried out on Stokes light, the Stokes light intensity curve after exponential fitting has high coincidence degree with the original curve, and the influence of light source disturbance and temperature change of the incubator is eliminated.
In fig. 4, a temperature profile of measured values when the conventional DTS system/method and the scheme of the present embodiment measure ambient temperatures of 50 ℃ and 75 ℃ is given.
In fig. 4, "≡" represents a measured value of the conventional DTS system/method at an ambient temperature of 50 ℃, and "" represents a measured value of the present embodiment at an ambient temperature of 50 ℃; "o" indicates a measurement of a conventional DTS system at an ambient temperature of 75 c,The measurements of the protocol of this example at ambient temperature of 75 ℃ are shown.
As can be seen from fig. 4, the conventional DTS system/method deviates more from the actual value, and the solution of this embodiment can have more accurate measurement values.
In fig. 5, the temperature measurement deviation of the conventional DTS system/method from the case of measuring the ambient temperature of 50 ℃ and 75 ℃ according to the scheme of the present embodiment is given.
In fig. 5, "≡" indicates the deviation value of the conventional DTS system/method at an ambient temperature of 50 ℃, and "Δ" indicates the deviation value of the scheme of the present embodiment at an ambient temperature of 50 ℃; "" indicates a deviation value of the conventional DTS system at an ambient temperature of 75 c,The deviation value of the protocol of this example at an ambient temperature of 75℃is shown.
As can be seen from fig. 5, the conventional DTS system/method has a deviation of about 2.5 ℃ at an ambient temperature of 50 ℃, and the solution of this example has a deviation of about 1.5 ℃ at an ambient temperature of 50 ℃; the conventional DTS system/method has a deviation of about 7c at an ambient temperature of 75 c and the protocol of this example has a deviation of about 3.5 c at an ambient temperature of 75 c. It is known that the deviation of the DTS system increases with the increase of the temperature, and the deviation can be preferably suppressed by the scheme of the present embodiment, so that the accuracy is better.
The invention and its embodiments have been described above by way of illustration and not limitation, and the invention is illustrated in the accompanying drawings and described in the drawings in which the actual structure is not limited thereto. Therefore, if one of ordinary skill in the art is informed by this disclosure, the structural mode and the embodiments similar to the technical scheme are not creatively designed without departing from the gist of the present invention.
Claims (8)
1. A raman stokes light intensity dynamic self-calibrating distributed temperature detection system comprising:
A detection fiber for deployment at the temperature measurement region;
a pulse laser for generating a laser pulse;
a wavelength division multiplexer for transmitting the laser pulse as incident light to the detection optical fiber and for filtering the back-scattered light of the detection optical fiber to obtain back-stokes raman scattered light and back-anti-stokes raman scattered 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 calculation unit is used for calculating the luminous fluxes of the back stokes Raman scattered light and the back anti-stokes Raman scattered light at any point of the detection optical fiber according to the signals acquired by the acquisition unit and calculating and acquiring the detection temperature at any measurement point of the detection optical fiber;
the detection optical fiber is provided with a reference optical fiber section in a constant temperature T 0 environment, and the calculation unit is used for calculating the luminous flux of the back anti-Stokes Raman scattered light at any point of the reference optical fiber section And luminous flux/>, of back stokes raman scattered lightAnd luminous flux/>, of back anti-stokes raman scattered light at the measurement pointAnd luminous flux/>, of back stokes raman scattered lightAcquiring the temperature T at a measuring point; wherein,
Where k is a boltzmann constant, h is a planck constant, and Δv is a raman shift amount.
2. The raman stokes light intensity dynamic self-calibrating distributed temperature detection system according to claim 1, wherein: the photodetector is a photo avalanche diode.
3. The raman stokes light intensity dynamic self-calibrating distributed temperature detection system according to claim 1, wherein: the reference optical fiber section is arranged at the first section of the detection optical fiber.
4. The dynamic self-calibration distributed temperature detection method for the Raman Stokes light intensity comprises the following steps:
s1, setting a reference optical fiber section at a 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 optical fiber section And luminous flux/>, of back stokes raman scattered lightAnd luminous flux/>, of back anti-stokes raman scattered light at the measurement pointAnd luminous flux of back stokes raman scattered light
Step S3, a temperature T at the measurement point is acquired, wherein,
Where k is a boltzmann constant, h is a planck constant, and Δv is a raman shift amount.
5. The method for dynamically self-calibrating distributed temperature detection of raman stokes light intensity according to claim 4, wherein the method comprises the steps of: luminous fluxAnd luminous flux/>The actual measurement value is obtained after the calculation unit converts according to the corresponding signals acquired by the acquisition unit.
6. The raman stokes light intensity dynamic self-calibration distributed temperature detection method according to claim 5, wherein: luminous fluxAnd luminous flux/>For the calculated value, the calculated value is calculated and obtained by a calculating unit according to the following formula,
Wherein,
For the measured value of the luminous flux of the back stokes raman scattered light at a further arbitrary point of the reference optical fiber segment, l 01 is the length from the further arbitrary point to the head end of the detection optical fiber;
- (α o+αs) is the attenuation coefficient of the detection fiber;
Luminous flux Obtained by substituting l=l 0, luminous flux/>Obtained by bringing in l=l x, l x is the length from the point to be measured to the head end of the detection fiber.
7. The raman stokes light intensity dynamic self-calibration distributed temperature detection method according to claim 6, wherein: the attenuation coefficient- (alpha o+αs) of the detection fiber is obtained by the following steps:
step SA, constructing luminous flux of back Stokes Raman scattered light of each point of the reference fiber segment And a calculation model from the corresponding point to the length L of the head end of the detection optical fiber,
Wherein alpha o is the average transmission loss of incident light in the detection optical fiber, alpha s is the average transmission loss of back stokes raman scattered light in the detection optical fiber, K S is the coefficient of the back stokes raman scattered light related to the scattering cross section of the optical fiber, S is the back scattering factor of the detection optical fiber, V S is the frequency of the back stokes raman scattered light,R s (T) is the temperature modulation function of the back Stokes Raman scattered light for the luminous flux of the incident light into the detection fiber;
step SB, by And taking L as an independent variable to obtain multiple groups of data of the reference optical fiber section, and performing curve fitting on the calculation model to obtain the attenuation coefficient- (alpha o+αs) of the detection optical fiber.
8. The raman stokes light intensity dynamic self-calibrating distributed temperature detection method according to claim 7, wherein: in step SA, the temperature modulation function R s (T) of the back Stokes Raman scattered light is,
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