CN114964547A - High-precision high-resolution optical fiber temperature sensing device and method based on bidirectional Raman scattering - Google Patents
High-precision high-resolution optical fiber temperature sensing device and method based on bidirectional Raman scattering Download PDFInfo
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Abstract
The invention relates to the field of distributed optical fiber sensing, and discloses a high-precision high-resolution bidirectional Raman scattering optical fiber temperature sensing device and a method, wherein the device comprises the following steps: the pulse laser source is connected with a port a of the first wavelength division multiplexer, a port c and a port d of the first wavelength division multiplexer are respectively connected with the first avalanche photodetector and the second avalanche photodetector, a port b of the first wavelength division multiplexer and the continuous optical semiconductor laser are respectively connected with one input end of the optical fiber coupler, the output end of the optical fiber coupler is connected with one end of the sensing optical fiber through the scaling optical fiber ring, the other end of the sensing optical fiber is connected with a port a of the second wavelength division multiplexer, and a port c and a port d of the second wavelength division multiplexer are respectively connected with the third avalanche photodetector and the fourth avalanche photodetector; the outputs of the first, second, third and fourth avalanche photodetectors are connected to a computer. The invention can improve the signal-to-noise ratio of the system, thereby improving the sensing distance, the temperature measurement precision and the temperature resolution.
Description
Technical Field
The invention relates to the field of distributed optical fiber sensing, in particular to a high-precision high-resolution bidirectional Raman scattering optical fiber temperature sensing device and method.
Background
The Raman distributed optical fiber sensing system can continuously measure the distributed temperature along the sensing optical fiber in real time. In addition, the Raman distributed optical fiber sensor has the characteristics of electromagnetic interference resistance, electric insulation, corrosion resistance, intrinsic safety, high sensitivity, light weight, small volume, embeddability (object) and the like, and is widely applied to the fields of traffic infrastructure, national defense safety monitoring and the like at present.
In the raman distributed fiber sensing technology, the signal-to-noise ratio (SNR) is an extremely important technical index. Currently, the sensing detection signal in the raman distributed fiber sensing technology is a spontaneous raman scattering signal with extremely weak intensity (the light intensity is only 50dB of the incident signal). And the raman signal intensity gradually weakens with the increase of the optical fiber sensing distance. Due to the technical bottleneck, the sensing distance of the conventional Raman distributed optical fiber sensing technology cannot reach 100km, the temperature measurement precision and the temperature resolution cannot break through 0.01 ℃, and the application of the Raman distributed optical fiber sensing technology is greatly limited.
Based on this, it is necessary to improve the existing raman distributed optical fiber sensing device and temperature demodulation method, so as to solve the technical bottleneck that the existing raman distributed optical fiber sensing system has a low signal-to-noise ratio (SNR), and further improve the sensing distance, temperature measurement accuracy and temperature resolution of the system.
Disclosure of Invention
In order to solve the technical bottleneck that the signal to noise ratio of the existing Raman distributed optical fiber temperature sensing system is low, and finally the sensing distance, the temperature measurement precision and the temperature resolution of the sensing system are low, the invention provides a high-precision high-resolution optical fiber temperature sensing device and method based on bidirectional Raman scattering.
In order to solve the technical problems, the invention adopts the technical scheme that: a high-precision high-resolution optical fiber temperature sensing device based on bidirectional Raman scattering comprises: the device comprises a pulse laser source, a first wavelength division multiplexer, a continuous optical semiconductor laser, an optical fiber coupler, a calibration optical fiber ring, a sensing optical fiber, a second wavelength division multiplexer, a first avalanche photodetector, a second avalanche photodetector, a third avalanche photodetector, a fourth avalanche photodetector and a computer;
the pulse laser output by the pulse laser source is connected with an a port of a first wavelength division multiplexer, a c port and a d port of the first wavelength division multiplexer are respectively connected with a first avalanche photodetector and a second avalanche photodetector, a b port of the first wavelength division multiplexer is connected with an input port of an optical fiber coupler, the continuous optical semiconductor laser is connected with the other input port of the optical fiber coupler, an output port of the optical fiber coupler is connected with one end of a sensing optical fiber through a calibration optical fiber ring, the other end of the sensing optical fiber is connected with an a port of a second wavelength division multiplexer, and a c port and a d port of the second wavelength division multiplexer are respectively connected with a third avalanche photodetector and a fourth avalanche photodetector; the output ends of the first avalanche photodetector, the second avalanche photodetector, the third avalanche photodetector and the fourth avalanche photodetector are connected with a computer;
the port wavelengths of the first wavelength division multiplexer and the second wavelength division multiplexer are respectively as follows: a. the wavelength of the port b is equal to the wavelength of the pulse laser, the wavelength of the port c is equal to the wavelength of Stokes light, the wavelength of the port d is equal to the wavelength of anti-Stokes light, and continuous laser output by the continuous light semiconductor laser is used for generating Raman gain on the anti-Stokes light in the sensing optical fiber.
The wavelength of the pulse laser source is 1550nm, and the wavelength of the continuous optical semiconductor laser is 1350 nm.
The port wavelengths of the first wavelength division multiplexer and the second wavelength division multiplexer are respectively as follows: a. the wavelength of the port b is 1550nm, the wavelength of the port c is 1450nm, and the wavelength of the port d is 1650 nm.
The pulse laser source comprises a semiconductor laser, an electro-optic modulator and a pulse generator, the output end of the pulse generator is connected with the control end of the electro-optic modulator, and laser output by the semiconductor laser forms pulse laser after being subjected to pulse modulation by the electro-optic modulator.
The high-precision high-resolution optical fiber temperature sensing device based on the bidirectional Raman scattering further comprises a high-speed data acquisition card, wherein the input end of the high-speed data acquisition card is connected with the output ends of the first avalanche photodetector, the second avalanche photodetector, the third avalanche photodetector and the fourth avalanche photodetector, and the output end of the high-speed data acquisition card is connected with the computer.
The nonlinear parameter of the sensing optical fiber is more than 10W -1 km -1 The nonlinear optical fiber of (1).
The length of the calibration optical fiber ring is larger than the optical transmission distance corresponding to the pulse width of the pulse laser.
In addition, the invention also provides a high-precision high-resolution optical fiber temperature sensing method based on the bidirectional Raman scattering, and the high-precision high-resolution optical fiber temperature sensing device based on the bidirectional Raman scattering comprises the following steps:
s1, calibration stage: setting the temperature of the calibration fiber loop to be constant at T 0 (ii) a Detecting the Raman backward anti-Stokes optical signal intensity phi in the calibration optical fiber ring through the first avalanche photodetector and the second avalanche photodetector as0 (T 0 L) and Raman backward Stokes light signal intensity phi s0 (T 0 L); respectively detecting the intensity phi of the Raman forward anti-Stokes optical signal in the sensing optical fiber through a third avalanche photodetector and a fourth avalanche photodetector as1 (T 0 L) and Raman forward Stokes light signal intensity phi s1 (T 0 ,L)；
S2, measurement stage: detecting Raman backward anti-Stokes optical signal intensity phi in sensing optical fiber by a first avalanche photodetector and a second avalanche photodetector as0 (T, L) and Raman backward Stokes light signal intensity phi s0 (T, L); respectively detecting the intensity phi of the Raman forward anti-Stokes optical signal in the sensing optical fiber through a third avalanche photodetector and a fourth avalanche photodetector as1 (T, L) and Raman Forward Stokes light Signal Strength Φ s1 (T,L)；
S3, calculation stage: calculating the temperature T along the optical fiber according to the measurement results of the steps S1 and S2, wherein the calculation formula is as follows:
where k is Boltzmann constant,. DELTA.v is the Raman frequency shift,. sup.h is the Planckian constant, F Com (T, L) represents the first signal ratio obtained during the measurement phase, F Com (T 0 L) represents the second signal ratio obtained in the scaling stage; first signal ratio F Com (T, L) and a second signal ratio F Com (T 0 And L) are respectively as follows:
compared with the prior art, the invention has the following beneficial effects:
compared with the existing distributed optical fiber sensing device, the high-precision high-resolution optical fiber temperature sensing device and method based on bidirectional Raman scattering can improve the signal-to-noise ratio (SNR) of the system, thereby realizing the improvement of the sensing distance, the temperature measurement precision and the temperature resolution of the system, and is expected to expand the sensing distance of the traditional Raman distributed optical fiber sensing technology to 100km and optimize the temperature resolution and the temperature measurement precision to 0.01 ℃.
Drawings
Fig. 1 is a schematic structural diagram of a raman distributed optical fiber sensing device capable of implementing high-precision and high-resolution sensing according to an embodiment of the present invention;
in the figure: 1: semiconductor laser, 2: electro-optical modulator, 3: pulse generator, 4: first wavelength division multiplexer, 5: 1350nm continuous optical semiconductor laser, 6: fiber coupler, 7: calibration fiber ring, 8: sensing fiber, 9: second wavelength division multiplexer, 10: first avalanche photodetector, 11: second avalanche photodetector, 12: third avalanche photodetector, 13: fourth avalanche photodetector, 14: high-speed data acquisition card, 15: and (4) a computer.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Example one
As shown in fig. 1, a high-precision and high-resolution optical fiber temperature sensing device based on bidirectional raman scattering according to an embodiment of the present invention includes: the device comprises a pulse laser source, a first wavelength division multiplexer 4, a continuous optical semiconductor laser 5, an optical fiber coupler 6, a calibration optical fiber ring 7, a sensing optical fiber 8, a second wavelength division multiplexer 9, a first avalanche photodetector 10, a second avalanche photodetector 11, a third avalanche photodetector 12, a fourth avalanche photodetector 13 and a computer 15.
The pulse laser output by the pulse laser source is connected with a port a of a first wavelength division multiplexer 4, a port c and a port d of the first wavelength division multiplexer 4 are respectively connected with a first avalanche photodetector 10 and a second avalanche photodetector 11, a port b of the first wavelength division multiplexer 4 is connected with an input port of an optical fiber coupler 6, a continuous optical semiconductor laser 5 is connected with the other input port of the optical fiber coupler 6, an output port of the optical fiber coupler 6 is connected with one end of a sensing optical fiber 8 through a scaling optical fiber ring 7, the other end of the sensing optical fiber 8 is connected with a port a of a second wavelength division multiplexer 9, and a port c and a port d of the second wavelength division multiplexer 9 are respectively connected with a third avalanche photodetector 12 and a fourth avalanche photodetector 13; the output ends of the first avalanche photodetector 10, the second avalanche photodetector 11, the third avalanche photodetector 12 and the fourth avalanche photodetector 13 are connected with a computer 15; the computer 15 demodulates the distributed temperature information along the sensing optical fiber according to the acquired detection information of the first avalanche photodetector, the second avalanche photodetector, the third avalanche photodetector and the fourth avalanche photodetector.
The port wavelengths of the first wavelength division multiplexer 4 and the second wavelength division multiplexer 9 are respectively: a. the wavelength of the b port is equal to the wavelength of the pulse laser, the wavelength of the c port is equal to the wavelength of Stokes light generated in the optical fiber by the pulse laser, the wavelength of the d port is equal to the wavelength of anti-Stokes light generated in the optical fiber by the pulse laser, the continuous laser output by the continuous optical semiconductor laser 5 is used for generating Raman gain on the anti-Stokes light in the optical fiber, and the wavelength meets the Raman gain condition.
Specifically, in the present embodiment, the wavelength of the pulsed laser source is 1550nm, and the wavelength of the continuous optical semiconductor laser 5 is 1350 nm. Specifically, in this embodiment, the port wavelengths of the first wavelength division multiplexer 4 and the second wavelength division multiplexer 9 are respectively: a. the wavelength of the port b is 1550nm, the wavelength of the port c is 1450nm, and the wavelength of the port d is 1650 nm.
Further, in this embodiment, the pulse laser source includes a semiconductor laser 1, an electro-optic modulator 2 and a pulse generator 3, an output end of the pulse generator 3 is connected to a control end of the electro-optic modulator 2, and laser output by the semiconductor laser 1 is pulse-modulated by the electro-optic modulator 2 to form pulse laser. Specifically, in the present embodiment, the central wavelength of the semiconductor laser 1 is 1550nm, and the central wavelength of the continuous optical semiconductor laser 5 is 1350nm, so as to amplify the raman anti-stokes signal in the optical path. The optical fiber coupler 6 used is a 1 × 2 optical fiber coupler.
Further, the high-precision high-resolution optical fiber temperature sensing device based on bidirectional raman scattering according to this embodiment further includes a high-speed data acquisition card 14, an input end of the high-speed data acquisition card 14 is connected to output ends of the first avalanche photodetector 10, the second avalanche photodetector 11, the third avalanche photodetector 12, and the fourth avalanche photodetector 13, and an output end of the high-speed data acquisition card is connected to the computer. The high speed data acquisition card 14 is used to pass throughThe first avalanche photodetector 10 and the second avalanche photodetector 11, and the third avalanche photodetector 12 and the fourth avalanche photodetector 13 collect raman stokes light and raman anti-stokes light signals in the sensing fiber in real time. The nonlinear parameter of the sensing optical fiber 8 is more than 10W -1 km -1 The nonlinear optical fiber of (1).
Example two
The embodiment of the invention provides a high-precision high-resolution optical fiber temperature sensing method based on bidirectional Raman scattering, which is realized by adopting the high-precision high-resolution optical fiber temperature sensing device based on the bidirectional Raman scattering, and comprises the following steps:
s1, calibration stage: setting the temperature of the calibration fiber loop to be constant at T 0 (ii) a Detection of Raman backward anti-Stokes light signal intensity phi in a calibration fiber ring by a first avalanche photodetector 10 and a second avalanche photodetector 11 as0 (T 0 L) and Raman backward Stokes light signal intensity phi s0 (T 0 L); the intensity phi of the Raman forward anti-Stokes optical signal in the sensing optical fiber is respectively detected by a third avalanche photodetector 12 and a fourth avalanche photodetector 13 as1 (T 0 L) and Raman forward Stokes light Signal intensity phi s1 (T 0 ,L)；
S2, measurement stage: detection of Raman backward anti-Stokes light signal intensity phi in sensing fiber by first avalanche photodetector 10 and second avalanche photodetector 11 as0 (T, L) and Raman backward Stokes light signal intensity phi s0 (T, L); the intensity phi of the Raman forward anti-Stokes optical signal in the sensing optical fiber is respectively detected by a third avalanche photodetector 12 and a fourth avalanche photodetector (13) as1 (T, L) and Raman Forward Stokes light Signal Strength Φ s1 (T,L)；
S3, calculation stage: calculating the temperature T along the optical fiber according to the measurement results of the steps S1 and S2, wherein the calculation formula is as follows:
where k is Boltzmann constant,. DELTA.v is the Raman frequency shift,. sup.h is the Planckian constant, F Com (T, L) represents the first signal ratio obtained during the measurement phase, F Com (T 0 L) represents the second signal ratio obtained in the scaling stage; first signal ratio F Com (T, L) and a second signal ratio F Com (T 0 And L) are respectively as follows:
specifically, in this embodiment, the length of the calibration fiber loop 7 is greater than the optical transmission length corresponding to the laser pulse width.
The distributed temperature demodulation principle of the present invention is described below.
The high-precision high-resolution optical fiber temperature sensing system for bidirectional Raman scattering provided by the embodiment of the invention takes the position of an optical fiber propagation L as a reference point to acquire a corresponding Raman forward scattering signal and a corresponding Raman backward scattering signal generated in a sensing optical fiber. Pulse laser enters the calibration optical fiber ring 7 and the sensing optical fiber 8 after passing through the first wavelength division multiplexer 5, Raman scattering occurs at each point on the whole optical fiber, and in the process, the continuous optical semiconductor laser 5 simultaneously amplifies Raman anti-Stokes scattering light with the wavelength of 1450nm generated by Raman forward scattering and Raman backward scattering. The raman backward anti-stokes signals excited at each point along the sensing fiber return to the first wavelength division multiplexer 4 and are output from the c port thereof to be detected by the first avalanche photodetector, and the backward raman anti-stokes scattered light signal intensity detected in the first avalanche photodetector is as follows:
raman backward Stokes signals excited by each point in the sensing optical fiber return to the first wavelength division multiplexer and are output from a d port of the first wavelength division multiplexer to be detected by the second avalanche photodetector, and the backward Raman Stokes scattered light signal intensity detected in the second avalanche photodetector is as follows:
raman forward anti-Stokes signals excited by each point in the sensing optical fiber pass through the second wavelength division multiplexer and are output from a c port of the second wavelength division multiplexer to be detected by a third avalanche photodetector, and the forward Raman anti-Stokes scattered light signal intensity detected in the third avalanche photodetector is as follows:
raman Stokes signals generated by Raman forward scattering at each point in the sensing optical fiber pass through the second wavelength division multiplexer and are output from a d port of the second wavelength division multiplexer to be detected by a fourth avalanche photodetector, and the forward Raman Stokes scattered light signal intensity detected in the fourth avalanche photodetector is as follows:
the expressions of the temperature coefficients appearing in the formulae (1) to (4) are as follows:
wherein P is the incident power of the pulse laser, K as 、K s Respectively represent and raman inverseCoefficients relating to backscattering cross-sections of the Tokes signal and the Raman Stokes signal, S being the backscattering factor of the optical fibre, v as 、v s Respectively representing the frequencies of the Raman anti-Stokes scattering signal and the Raman Stokes scattering signal, mu a Showing the amplification factor, alpha, for the gain produced for the Raman anti-Stokes scattered signal 0 、α as 、α s The loss coefficients of incident light, Raman anti-Stokes light and Raman Stokes light in the sensing optical fiber are respectively, l is the total length of the optical fiber, delta v is Raman frequency shift, h is a Planckian constant, k is a Boltzmann constant, and T is the temperature of the sensing optical fiber.
The ratio of the backward raman anti-stokes scattering signal intensity to the raman stokes scattering signal intensity is calculated by using formula (5) and formula (6):
the ratio of the forward raman anti-stokes scattering signal intensity to the raman stokes scattering signal intensity is calculated by using formula (8) and formula (9):
taking the geometric mean value of the formula (12) and the formula (13) to obtain the formula (14):
at the front end L of the sensing optical fiber 0 Setting a calibration optical fiber ring with the length slightly larger than the laser pulse width, and recording the ambient temperature of the sensing optical fiber as T 0 . At a constant temperature T 0 The intensities of the corresponding raman forward scattering signal and raman backward scattering signal generated in the sensing fiber at this time are acquired. In the high-precision and high-resolution optical fiber temperature sensing system based on the bidirectional Raman scatteringThe laser emitted by the semiconductor laser generates pulse laser under the modulation of the electro-optical modulator and the pulse generator, the pulse laser enters the calibration optical fiber ring and the sensing optical fiber after passing through the first wavelength division multiplexer, and Raman scattering occurs at each point on the whole optical fiber. The laser light emitted from the continuous optical semiconductor laser 5 simultaneously generates amplification gain for anti-stokes scattered light generated by raman forward scattering and raman backward scattering. In the process, according to the working principle of the fiber Raman amplifier, based on the stimulated Raman scattering effect in the fiber, when light with a certain wavelength is transmitted in the fiber, the energy of the incident light field is partially converted into scattered light field energy with lower frequency and molecular vibration energy due to the interaction of the incident light field and the nonlinear parameter of the molecular medium. Under certain conditions, raman scattering is a property of laser light, and both stokes light and anti-stokes light are coherent light. Thus, when the weak signal light and the strong pump light are transmitted in the optical fiber at the same time, and the wavelength of the weak signal light is arranged in the Raman gain spectrum of the pump light, the light energy is transferred from the pump light to the signal light, thereby realizing the light amplification of the weak signal light. Therefore, the light with the wavelength of 1350nm emitted by the continuous optical semiconductor laser 5 can perform light amplification on the anti-stokes light with the wavelength of 1450nm in the photosensitive fiber as long as the light intensity of 1350nm is greater than that of 1450 nm. Since the intensity of the anti-stokes light is generally weak, the intensity of the 1350nm laser light is much higher than that of the anti-stokes light, that is, the condition of light amplification is satisfied.
At a temperature T 0 The raman anti-stokes scattered light signal generated by raman backscattering generated by the section of optical fiber returns to the first wavelength division multiplexer, is output from a c port of the first wavelength division multiplexer and is detected by the first avalanche photodetector, and the intensity of the backshank anti-stokes scattered light signal detected in the first avalanche photodetector is as follows:
at a temperature T 0 The first wave is returned by a Raman Stokes signal generated by Raman backscattering of the optical fiberThe multiplexer is output from a d port of the multiplexer and then detected by a second avalanche photodetector, and the backward Raman Stokes scattered light signal intensity detected in the second avalanche photodetector is as follows:
at a temperature T 0 The raman anti-stokes signal generated by raman forward scattering of the section of optical fiber passes through the second wavelength division multiplexer and is output from the c port of the second wavelength division multiplexer and then is detected by a third avalanche photodetector, and the forward raman anti-stokes scattered light signal intensity detected in the third avalanche photodetector is as follows:
at a temperature T 0 The raman stokes signal generated by raman forward scattering of the section of optical fiber passes through the second wavelength division multiplexer and is output from a d port of the second wavelength division multiplexer and then is detected by a fourth avalanche photodetector, and the forward raman stokes scattered light signal intensity detected in the fourth avalanche photodetector is as follows:
wherein the expression of the temperature coefficient appearing in the formula (10-13) is as follows:
the ratio of the backward raman anti-stokes scattering signal intensity to the raman stokes scattering signal intensity is calculated by using formula (15) and formula (16):
the ratio of the forward raman anti-stokes scattering signal intensity to the raman stokes scattering signal intensity is calculated by using formula (12) and formula (13):
obtaining a formula (23) by taking a geometric mean value of the formula (21) and the formula (22):
calculated using equation (14) and equation (23), F Com (T, L) and F Com (T 0 L) the ratio can be:
from equation (24), the temperature along the final fiber can be expressed as equation (5).
Thus, in actual measurement, first at a known temperature T 0 Sensing optical fiber L 0 And (4) carrying out calibration processing, and demodulating the temperature at the sensing optical fiber L by using a formula (5).
In summary, the invention provides a high-precision high-resolution optical fiber temperature sensing device and method based on bidirectional raman scattering, which amplify anti-stokes light in a sensing optical fiber by raman amplification, and compared with the existing distributed optical fiber sensing device, can improve the signal-to-noise ratio (SNR) of the system, thereby realizing the improvement of the sensing distance, the temperature measurement precision and the temperature resolution of the system, and is expected to expand the sensing distance of the traditional raman distributed optical fiber sensing technology to 100km and optimize the temperature resolution and the temperature measurement precision to 0.01 ℃.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A high-precision high-resolution optical fiber temperature sensing device based on bidirectional Raman scattering is characterized by comprising: the device comprises a pulse laser source, a first wavelength division multiplexer (4), a continuous optical semiconductor laser (5), an optical fiber coupler (6), a scaling optical fiber ring (7), a sensing optical fiber (8), a second wavelength division multiplexer (9), a first avalanche photodetector (10), a second avalanche photodetector (11), a third avalanche photodetector (12), a fourth avalanche photodetector (13) and a computer (15);
the pulse laser output by the pulse laser source is connected with a port a of a first wavelength division multiplexer (4), a port c and a port d of the first wavelength division multiplexer (4) are respectively connected with a first avalanche photodetector (10) and a second avalanche photodetector (11), a port b of the first wavelength division multiplexer (4) is connected with an input port of an optical fiber coupler (6), a continuous optical semiconductor laser (5) is connected with the other input port of the optical fiber coupler (6), an output port of the optical fiber coupler (6) is connected with one end of a sensing optical fiber (8) through a scaling optical fiber ring (7), the other end of the sensing optical fiber (8) is connected with a port a of a second wavelength division multiplexer (9), and a port c and a port d of the second wavelength division multiplexer (9) are respectively connected with a third avalanche photodetector (12) and a fourth avalanche photodetector (13); the output ends of the first avalanche photodetector (10), the second avalanche photodetector (11), the third avalanche photodetector (12) and the fourth avalanche photodetector (13) are connected with a computer (15);
the port wavelengths of the first wavelength division multiplexer (4) and the second wavelength division multiplexer (9) are respectively as follows: a. the wavelength of the port b is equal to the wavelength of the pulse laser, the wavelength of the port c is equal to the wavelength of Stokes light, the wavelength of the port d is equal to the wavelength of anti-Stokes light, and continuous laser light output by the continuous light semiconductor laser (5) is used for generating Raman gain on the anti-Stokes light in the sensing optical fiber.
2. The fiber temperature sensor device with high precision and high resolution based on bidirectional Raman scattering according to claim 1, wherein the wavelength of the pulsed laser source is 1550nm, and the wavelength of the continuous optical semiconductor laser (5) is 1350 nm.
3. The device for sensing the temperature of the optical fiber with high precision and high resolution based on the bidirectional Raman scattering according to claim 2, wherein the port wavelengths of the first wavelength division multiplexer (4) and the second wavelength division multiplexer (9) are respectively as follows: a. the wavelength of the port b is 1550nm, the wavelength of the port c is 1450nm, and the wavelength of the port d is 1650 nm.
4. The high-precision high-resolution optical fiber temperature sensing device based on bidirectional Raman scattering according to claim 1, wherein the pulsed laser source comprises a semiconductor laser (1), an electro-optic modulator (2) and a pulse generator (3), an output end of the pulse generator (3) is connected with a control end of the electro-optic modulator (2), and laser output by the semiconductor laser (1) is pulse-modulated by the electro-optic modulator (2) to form pulsed laser.
5. The fiber temperature sensing device of claim 1, further comprising a high-speed data acquisition card (14), wherein the input end of the high-speed data acquisition card (14) is connected to the output ends of the first avalanche photodetector (10), the second avalanche photodetector (11), the third avalanche photodetector (12), and the fourth avalanche photodetector (13), and the output end is connected to the computer.
6. High-precision Raman scattering-based high-precision optical fiber according to claim 1The optical fiber temperature sensing device with high resolution is characterized in that the nonlinear parameter of the sensing optical fiber (8) is more than 10W -1 km -1 The nonlinear optical fiber of (1).
7. The device for sensing the temperature of the optical fiber with high precision and high resolution based on the bidirectional Raman scattering according to claim 1, wherein the length of the scaling optical fiber ring (7) is greater than the optical transmission distance corresponding to the pulse width of the laser.
8. A high-precision high-resolution optical fiber temperature sensing method based on bidirectional Raman scattering is characterized in that the high-precision high-resolution optical fiber temperature sensing device based on the bidirectional Raman scattering of any one of claims 1-7 is adopted, and the method comprises the following steps:
s1, calibration stage: setting the temperature of the calibration fiber loop to be constant at T 0 (ii) a Detecting the Raman backward anti-Stokes optical signal intensity phi in the calibration fiber ring through a first avalanche photodetector (10) and a second avalanche photodetector (11) as0 (T 0 L) and Raman backward Stokes light signal intensity phi s0 (T 0 L); the intensity phi of the Raman forward anti-Stokes optical signal in the sensing optical fiber is respectively detected by a third avalanche photodetector (12) and a fourth avalanche photodetector (13) as1 (T 0 L) and Raman forward Stokes light signal intensity phi s1 (T 0 ,L)；
S2, measurement stage: detecting Raman backward anti-Stokes optical signal intensity phi in the sensing optical fiber by a first avalanche photodetector (10) and a second avalanche photodetector (11) as0 (T, L) and Raman backward Stokes light signal intensity phi s0 (T, L); the intensity phi of the Raman forward anti-Stokes optical signal in the sensing optical fiber is respectively detected by a third avalanche photodetector (12) and a fourth avalanche photodetector (13) as1 (T, L) and Raman Forward Stokes light Signal Strength Φ s1 (T,L)；
S3, calculation stage: calculating the temperature T along the optical fiber according to the measurement results of the steps S1 and S2, wherein the calculation formula is as follows:
where k is Boltzmann constant,. DELTA.v is the Raman frequency shift,. sup.h is the Planckian constant, F Com (T, L) represents the first signal ratio obtained during the measurement phase, F Com (T 0 L) represents the second signal ratio obtained in the scaling stage; first signal ratio F Com (T, L) and a second signal ratio F Com (T 0 And L) are respectively as follows:
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