Raman distributed fiber temperature sensing device for intelligent mine temperature detection

Abstract

The application relates to the field of distributed optical fiber sensing, and particularly relates to a high-precision Raman distributed optical fiber temperature sensing device based on double-pumping wavelengths and oriented to temperature detection of intelligent mines, which comprises an optical amplification module, a wavelength division multiplexer, a sensing optical fiber, a photoelectric detector, a data acquisition card and a computer; the output ends of first and second pulse lasers are respectively connected with two input ends of an optical switch, the output end of the optical switch is connected with the input end of the optical amplification module, the first output end of the optical amplification module is connected with port a of the wavelength division multiplexer, the second output end is connected with port b of the wavelength division multiplexer, port c and port d of the wavelength division multiplexer are respectively connected with the photoelectric detector and one end of the sensing optical fiber; the output signal of the photoelectric detector is output to the computer after being collected by the data acquisition card to obtain temperature information of the sensing optical fiber along the line. The application does not need to be calibrated, has high measurement precision and high resolution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of distributed optical fiber sensing, and particularly to a Raman distributed optical fiber temperature sensing device for intelligent mine temperature detection. BACKGROUND

[0002] The Raman distributed optical fiber sensing technology can simultaneously utilize an optical fiber as a sensing element and a transmission medium to detect temperature field changes at different positions along the sensing optical fiber. Due to its advantages of continuous temperature measurement, high safety, corrosion resistance, intrinsic safety, and anti-electromagnetic interference, the technology has great social demand and application prospects in the field of health monitoring of large infrastructure structures, such as tunnel, power cable, gas pipeline, dam, and other major infrastructure projects. The technology can provide comprehensive data support for intelligent mine temperature detection.

[0003] In the traditional Raman distributed optical fiber sensing technology, calibration is the most critical step for accurate temperature demodulation. This is because the direct measurement only obtains the relative temperature values along the optical fiber. Only after calibration, the real absolute temperature values can be measured. The calibration process is as follows: first, place the entire sensing optical fiber in the same environment temperature T0 to obtain the light intensity information of each position of the sensing optical fiber at T0, and then set the temperature of different positions of the sensing optical fiber to T according to the measurement environment to be laid, and calculate the value of T through the traditional temperature demodulation formula. That is, the existing Raman distributed optical fiber temperature sensing demodulation method must perform optical fiber calibration before measurement, and then perform distributed temperature demodulation based on the light intensity ratio of Raman Stokes light and Raman anti-Stokes light. This measurement scheme has three serious technical bottlenecks in actual engineering applications. They are:

[0004] (1) When the system laser, photodetector, sensing optical fiber, or any device of the system is replaced during measurement, recalibration is required, which seriously affects the measurement time of the system and also leads to redundant system demodulation steps;

[0005] (2) When the optical fiber is severely bent or damaged at a certain point, a serious temperature error will occur at that point during measurement;

[0006] (3) During the system calibration process, a large amount of optical noise is introduced in the Raman Stokes light and Raman anti-Stokes light channels, which ultimately leads to the deterioration of the signal-to-noise ratio of the system, thereby affecting the sensing distance and temperature measurement accuracy of the sensing system, and other performances;

[0007] (4) There is a 200nm wavelength difference between Raman Stokes light and Raman anti-Stokes light. The traditional system is affected by the optical fiber dispersion caused by this wavelength difference, which ultimately seriously affects the measurement accuracy of the system.

[0008] In addition, since the Raman distributed optical fiber sensing system has a sensing signal of weak spontaneous Raman scattering signal (the light intensity is only 50dB of the incident signal), and the sensing optical cable is laid in the field with large optical fiber loss and harsh environment, once the signal intensity measurement in the calibration process has an error, the calibration temperature measurement will have a large deviation, and the final temperature measurement result will be directly affected, thereby greatly deteriorating the performance of the sensing system.

[0009] In summary, the above technical bottleneck greatly limits the application of the Raman distributed optical fiber sensing technology, and therefore it is necessary to improve the existing Raman distributed optical fiber sensing device and temperature demodulation method to solve the technical bottleneck that the temperature demodulation needs to be carried out through the calibration process in the existing Raman distributed optical fiber sensing system, and to improve the sensing performance such as sensing distance, temperature measurement accuracy and temperature resolution of the system. SUMMARY

[0010] In order to avoid the technical bottleneck of system measurement accuracy, sensing distance, signal-to-noise ratio deterioration and redundant demodulation steps caused by the above-mentioned traditional temperature demodulation scheme, the present application proposes a Raman distributed optical fiber temperature sensing device for intelligent mine temperature detection to improve the accuracy of intelligent mine temperature detection and reduce the measurement time.

[0011] In order to solve the above technical problems, the technical scheme adopted by the present application is as follows: a Raman distributed optical fiber temperature sensing device for intelligent mine temperature detection, comprising a first pulse laser, a second pulse laser, an optical switch, an optical amplification module, a wavelength division multiplexer, a sensing optical fiber, a photodetector, a data acquisition card and a computer.

[0012] The output ends of the first pulse laser and the second pulse laser are respectively connected with the two input ends of the optical switch, the output end of the optical switch is connected with the input end of the optical amplification module, the first output end of the optical amplification module is connected with port a of the wavelength division multiplexer, the second output end is connected with port b of the wavelength division multiplexer, and port c and port d of the wavelength division multiplexer are respectively connected with the photodetector and one end of the sensing optical fiber.

[0013] The wavelength of the Raman scattering Stokes light generated by the laser output by the first pulse laser in the sensor optical fiber is equal to the wavelength of the Raman scattering anti-Stokes light generated by the laser output by the second pulse laser in the sensor optical fiber.

[0014] The Raman scattering Stokes light generated by the laser output by the first pulse laser in the sensor optical fiber and the Raman scattering anti-Stokes light generated by the laser output by the second pulse laser in the sensor optical fiber return to port d of the wavelength division multiplexer, and are output to the photodetector through port c for detection.

[0015] The output signal of the photoelectric detector is collected by a data acquisition card and output to a computer to calculate the temperature information of the sensing optical fiber along the line.

[0016] The optical amplification module comprises a first optical amplifier and a second optical amplifier.

[0017] The wavelength of the first pulse laser is 1350nm, and the wavelength of the second pulse laser is 1550nm.

[0018] The wavelength of the a port of the wavelength division multiplexer is 1350nm, the wavelength of the b port is 1550nm, the wavelength of the c port is 1350nm / 1450nm / 1550nm, and the wavelength of the d port is 1450nm.

[0019] The sensing optical fiber is a multimode nonlinear optical fiber with a nonlinear parameter greater than 10W -1 km -1 .

[0020] The optical switch is a 2x1 multimode optical switch, and the first pulse laser and the second pulse laser are pulse semiconductor lasers.

[0021] The incident power of the first pulse laser and the second pulse laser into the sensing optical fiber is the same.

[0022] The calculation formula for the computer to calculate the temperature information of the sensing optical fiber along the line is:

[0023]

[0024] Wherein, T represents the temperature of the sensing optical fiber at the L position, F Back (T,L) represents the ratio of the Raman back anti-Stokes light generated by the laser output by the second pulse laser at the L position of the sensing optical fiber to the Raman back anti-Stokes light generated by the laser output by the first pulse laser at the L position of the sensing optical fiber; k is the Boltzmann constant, Δv is the Raman shift, and h is the Planck constant.

[0025] The incident power of the first pulse laser and the second pulse laser into the sensing optical fiber is different.

[0026] The calculation formula for the computer to calculate the temperature information of the sensing optical fiber along the line is:

[0027]

[0028] Wherein, T represents the temperature of the sensing optical fiber at the L position, F Back(T, L) represents the ratio of the intensity of the Raman back anti-Stokes light generated by the second pulsed laser output laser at the L position of the sensing fiber to the Raman back anti-Stokes light generated by the first pulsed laser output laser at the L position of the sensing fiber; k is the Boltzmann constant, Delta v is the Raman shift, h is the Planck constant, and P1 / P2 represents the ratio of the incident power of the first laser and the second laser output laser.

[0029] Compared with the existing distributed optical fiber sensing device, the Raman distributed optical fiber temperature sensing device for intelligent mine temperature detection provided by the application is realized based on double pumping wavelengths, and has the following beneficial effects:

[0030] (1) The calibration process of the system before measurement is eliminated, and the measurement time of the system is optimized.

[0031] (2) The technical bottleneck that measurement error occurs at the point where the optical fiber is severely bent or damaged is solved.

[0032] (3) The technical bottleneck that a large amount of optical noise is introduced in the Raman Stokes light and Raman anti-Stokes light channels during the calibration process of the system is solved, the signal-to-noise ratio of the system is optimized, and the sensing distance, temperature measurement accuracy and temperature resolution of the system are ultimately improved.

[0033] (4) The technical bottleneck that measurement error occurs due to fiber dispersion in the traditional system is solved, and the measurement accuracy of the system is optimized. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A structure diagram of a Raman distributed optical fiber temperature sensing device for intelligent mine temperature detection is provided for the first embodiment of the application.

[0035] Figure 2 A structure diagram of a Raman distributed optical fiber temperature sensing device for intelligent mine temperature detection is provided for the second embodiment of the application.

[0036] In the figure: 1: first pulsed laser, 2: second pulsed laser, 3: optical switch, 4: optical amplification module, 5: wavelength division multiplexer, 6: sensing optical fiber, 7: photodetector, 8: data acquisition card, 9: computer, 10: first optical amplifier, 11: second optical amplifier. DETAILED DESCRIPTION

[0037] To make the objectives, 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. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] like Figure 1 As shown, Embodiment 1 of the present invention provides a Raman distributed fiber optic temperature sensing device for temperature detection in smart mines. It improves accuracy and measurement efficiency based on dual-pump wavelengths. It includes a first pulse laser 1, a second pulse laser 2, an optical switch 3, an optical amplification module 4, a wavelength division multiplexer 5, a sensing fiber 6, a photodetector 7, a data acquisition card 8, and a computer 9.

[0040] Specifically, in this embodiment, the output terminals of the first pulsed laser 1 and the second pulsed laser 2 are respectively connected to the two input terminals of the optical switch 3, the output terminal of the optical switch 3 is connected to the input terminal of the optical amplification module 4, the first output terminal of the optical amplification module 4 is connected to port a of the wavelength division multiplexer 5, the second output terminal is connected to port b of the wavelength division multiplexer 5, and ports c and d of the wavelength division multiplexer 5 are respectively connected to one end of the photodetector 7 and the sensing fiber 6.

[0041] The wavelength of the Raman-scattered Stokes light generated by the laser output from the first pulsed laser 1 in the sensor fiber 6 is equal to the wavelength of the Raman-scattered anti-Stokes light generated by the laser output from the second pulsed laser 2 in the sensor fiber 6.

[0042] The Raman-scattered Stokes light generated by the laser output from the first pulsed laser 1 in the sensor fiber 6 and the Raman-scattered anti-Stokes light generated by the laser output from the second pulsed laser 2 in the sensor fiber 6 return to port d of the wavelength division multiplexer 5, and are output to the photodetector 7 via port c; the output signal of the photodetector 7 is acquired by the data acquisition card 8 and then output to the computer 9 to calculate the temperature information along the sensing fiber 6.

[0043] Specifically, in this embodiment, the optical amplification module 4 is an erbium-doped fiber amplifier. It includes two output terminals, one for amplified laser signals from the first pulse laser and the other for amplified laser signals from the second pulse laser. The output photodetector 7 is an avalanche photodetector.

[0044] Specifically, in the embodiment, the wavelength of the first pulsed laser 1 is 1350 nm, and the wavelength of the second pulsed laser 2 is 1550 nm; the wavelength of the a port of the wavelength division multiplexer 5 is 1350 nm, the wavelength of the b port is 1550 nm, the wavelength of the c port is 1350 nm / 1450 nm / 1550 nm, and the wavelength of the d port is 1450 nm. The sensing optical fiber 5 is a multimode nonlinear optical fiber with a nonlinear parameter greater than 10 W -1 km -1

[0045] The first pulsed laser 1 and the second pulsed laser 2 are pulsed semiconductor lasers.

[0045] Further, in the embodiment, the input incident power of the first pulsed laser 1 and the second pulsed laser 2 in the sensing optical fiber 6 is the same.

[0046] The wavelength of the first pulsed laser is 1350 nm, and the wavelength of the second pulsed laser 2 is 1550 nm. The demodulation principle of the embodiment of the application will be introduced below. In the high-precision Raman distributed optical fiber temperature sensing device based on double pumping wavelengths, the position L in the sensing optical fiber is taken as a reference point to obtain the Raman backscattering signal generated in the sensing optical fiber.

[0047] First, the pulsed laser with a wavelength of 1350 nm emitted by the first pulsed laser is input to the optical amplifier for amplification. At this time, only the pulsed laser with a central wavelength of 1350 nm exists in the optical path between the optical switch and the wavelength division multiplexer. After amplification, the optical signal with a wavelength of 1350 nm is input to the sensing optical fiber 6 through the wavelength division multiplexer 5. The pulsed laser excites Raman scattering at each point on the sensing optical fiber 6. In this process, the pulsed laser excites Raman backscattering light with a wavelength of 1250 nm and Raman backscattering light with a wavelength of 1450 nm at the same time. Through the wavelength screening of the wavelength division multiplexer, only the Raman backscattering light with a wavelength of 1450 nm excited at each point along the sensing optical fiber returns to the wavelength division multiplexer and is output from the c port, and then is detected by the avalanche photodetector. At this time, the intensity of the back Raman Stokes scattering light signal with a wavelength of 1450 nm detected by the avalanche photodetector is:

[0048]

[0049] wherein P1 is the incident power of the 1350 nm laser, K represents a coefficient related to the backscattering cross section, S is the backscattering factor of the optical fiber, v s (λ) respectively represent the frequency of the Raman Stokes scattering signal related to the wavelength, α0(λ), α s(λ) are the wavelength-dependent loss coefficients of the incident light and the Raman-Stokes light in the sensing fiber, respectively, Δν is the Raman shift, h is the Planck constant, k is the Boltzmann constant, and T is the temperature of the sensing fiber.

[0050] R s (T) is the temperature coefficient, and its expression is as follows:

[0051]

[0052] Then, the optical switch 3 is adjusted to pass the pulsed laser of the second pulsed laser with the output wavelength of 1550 nm, and the pulsed laser is amplified by the optical amplifier and then enters the sensing fiber through the wavelength division multiplexer 4. At this time, only the pulsed laser with the central wavelength of 1550 nm exists in the optical path between the optical switch and the wavelength division multiplexer, and the amplified 1550 nm optical signal excites Raman scattering at each point on the whole optical fiber. In this process, the pulsed laser simultaneously excites Raman back anti-Stokes scattering light with the wavelength of 1450 nm and Raman back Stokes scattering light with the wavelength of 1650 nm. After the wavelength screening of the wavelength division multiplexer, only the Raman back anti-Stokes scattering light with the wavelength of 1450 nm excited at each point along the sensing fiber 5 returns to the wavelength division multiplexer 4 and is output from the c port thereof to be detected by the photodetector. At this time, the intensity of the back Raman anti-Stokes scattering light signal with the wavelength of 1450 nm detected in the photodetector is as follows:

[0053]

[0054] wherein P2 is the incident power of the 1550 nm laser, K represents a coefficient related to the backscattering cross section, S is the backscattering factor of the optical fiber, v as (λ) respectively represent the frequency of the Raman-Stokes scattering signal related to the wavelength, α0(λ), α as (λ) are the wavelength-dependent loss coefficients of the incident light and the Raman-Stokes light in the sensing fiber, respectively, Δν is the Raman shift, h is the Planck constant, k is the Boltzmann constant, and T is the temperature of the sensing fiber.

[0055] R a (T) is the temperature coefficient, and its expression is as follows:

[0056]

[0057] According to the formula (1) and the formula (3), under the premise that the incident powers are the same, that is, P1=P2, the ratio of the intensity of the back Raman anti-Stokes scattering signal with the wavelength of 1450 nm to the intensity of the Raman-Stokes scattering signal with the wavelength of 1450 nm is as follows:

[0058]

[0059] Since the wavelength of the back Raman anti-Stokes scattering signal at this time is the same as that of the Raman Stokes scattering signal, and v as (λ), v s (λ), α as (λ) and α s (λ) are all wavelength-dependent parameters, formula (5) can be simplified as follows:

[0060]

[0061] Let:

[0062]

[0063] From formula (6) and (7), the temperature of the optical fiber along the line can be expressed as:

[0064]

[0065] where T represents the temperature at the position L of the sensing optical fiber, F Back (T, L) represents the ratio of the intensity of the Raman back anti-Stokes light generated by the laser output by the second pulse laser at the position L of the sensing optical fiber to the Raman back anti-Stokes light generated by the laser output by the first pulse laser at the position L of the sensing optical fiber, k is the Boltzmann constant, Δv is the Raman shift, and h is the Planck constant.

[0066] Therefore, in actual measurement, the present application does not need to place the entire optical fiber in the same temperature environment for calibration, but only needs to directly adjust the output powers of the two lasers so that the powers of the two different wavelength lasers incident into the sensing optical fiber are the same, and then formula (8) can be directly used to demodulate the temperature at the position L of the sensing optical fiber. In addition, in the case where the output powers of the two lasers are different, i.e. P1≠P2, the ratio of the powers of the 1350nm and 1550nm lasers output from the d port of the wavelength division multiplexer can also be recorded, denoted as P1 / P2, and then:

[0067]

[0068] Therefore, combined with formula (7), and v as (λ), v s (λ), α as (λ) and α s (λ) are all wavelength-dependent parameters have:

[0069]

[0070] Through formula (10), the temperature at the position L of the sensing optical fiber can be demodulated.

[0071] Example 2

[0072] like Figure 2 As shown, Embodiment 2 of the present invention provides a Raman distributed optical fiber temperature sensing device for temperature detection in smart mines. Similar to Embodiment 1, it includes a first pulse laser 1, a second pulse laser 2, an optical switch 3, a wavelength division multiplexer 5, a sensing optical fiber 6, a photodetector 7, a data acquisition card 8, and a computer 9.

[0073] Unlike Embodiment 1, in this embodiment, the optical amplification module specifically includes a first optical amplifier 10 and a second optical amplifier 11. One end of the first optical amplifier 10 is connected to one output terminal of the optical switch, and the other end is connected to port a of the wavelength division multiplexer 5. One end of the second optical amplifier 11 is connected to the output terminal of the optical switch, and the other end is connected to port b of the wavelength division multiplexer 5.

[0074] Furthermore, optical switch 3 is a 2×2 optical switch, with ports a and c connected, and ports b and d connected. By switching the state of optical switch 3, the switching between the first pulse laser 1 and the second pulse laser 2 can be achieved. The first optical amplifier 10 and the second optical amplifier 11 are both erbium-doped fiber amplifiers.

[0075] In this embodiment, when the optical switch 3 is in the first state, its ports a and c are connected, and its ports b and d are disconnected. The pulsed laser emitted by the first pulsed laser is input to the first optical amplifier 10 through port c of the optical switch 2 for amplification. At this time, there is only a pulsed laser with a center wavelength of 1350nm in the optical path between the optical switch and the wavelength division multiplexer. The amplified 1350nm optical signal enters the sensing fiber 6 through ports a and d of the wavelength division multiplexer 5. Raman scattering is excited at various points along the entire sensing fiber 6. Among the Raman backscattered Stokes signals excited at various points along the sensing fiber, only the Raman backscattered Stokes light with a wavelength of 1450nm returns to the wavelength division multiplexer and is output from its port c and detected by the avalanche photodetector.

[0076] Then, the optical switch 3 is adjusted to be in the second state, and the port a and the port c are disconnected, and the port b and the port d are connected, the second pulsed laser with the wavelength of 1550 nm is input into the second optical amplifier 11 through the d port of the optical switch, and then is input into the sensing optical fiber through the circuit b port and the d port of the wavelength division multiplexer 4, at this time, only the pulsed laser with the central wavelength of 1550 nm exists in the optical path between the optical switch and the wavelength division multiplexer, and the optical signal with the wavelength of 1550 nm after amplification excites Raman scattering at each point of the whole optical fiber, and only the Raman backward anti-Stokes scattering light with the wavelength of 1450 nm returns to the wavelength division multiplexer 5 and is output from the c port, and then is detected by the photodetector; then, the computer 9 can realize temperature detection of the sensing optical fiber along the line according to the Stokes and anti-Stokes light intensity signals detected under the two states of the optical switch by using formula (7).

[0077] In summary, the present application provides a Raman distributed optical fiber temperature sensing device for intelligent mine temperature detection, compared with the existing distributed optical fiber sensing device, the present application has the following beneficial effects:

[0078] (1) The calibration process of the system before measurement is eliminated, and the measurement time of the system is optimized;

[0079] (2) The technical bottleneck that measurement error occurs at a point of the optical fiber when the optical fiber is severely bent or damaged is solved;

[0080] (3) The technical bottleneck that a large amount of optical noise is introduced in the Raman Stokes light and Raman anti-Stokes light channels during the calibration process of the system is solved, calibration is not needed, the signal-to-noise ratio of the system is optimized, and finally the sensing distance, temperature measurement accuracy and temperature resolution of the system are improved;

[0081] (4) The technical bottleneck that measurement error occurs due to fiber dispersion in the traditional system is solved, and the measurement accuracy of the system is optimized.

[0082] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A Raman distributed fiber optic temperature sensing device for temperature detection in smart mines, characterized in that, Includes a first pulse laser (1), a second pulse laser (2), an optical switch (3), an optical amplification module (4), a wavelength division multiplexer (5), a sensing fiber (6), a photodetector (7), a data acquisition card (8), and a computer (9); The output ends of the first pulse laser (1) and the second pulse laser (2) are respectively connected to the two input ends of the optical switch (3). The output end of the optical switch (3) is connected to the input end of the optical amplifier module (4). The first output end of the optical amplifier module (4) is connected to port a of the wavelength division multiplexer (5), and the second output end is connected to port b of the wavelength division multiplexer (5). Port c and port d of the wavelength division multiplexer (5) are respectively connected to one end of the photodetector (7) and the sensing fiber (6). The wavelength of the Raman-scattered Stokes light generated by the laser output from the first pulsed laser (1) in the sensing fiber (6) is equal to the wavelength of the Raman-scattered anti-Stokes light generated by the laser output from the second pulsed laser (2) in the sensing fiber (6). The Raman-scattered Stokes light generated by the laser output from the first pulsed laser (1) in the sensing fiber (6) and the Raman-scattered anti-Stokes light generated by the laser output from the second pulsed laser (2) in the sensing fiber (6) return to port d of the wavelength division multiplexer (5) and are output to the photodetector (7) via port c. The output signal of the photodetector (7) is acquired by the data acquisition card (8) and then output to the computer (9) to calculate the temperature information along the sensing fiber (6); The optical switch (3) is used to switch the first pulse laser (1) and the second pulse laser (2) to output lasers respectively. The photodetector (7) is used to detect the Raman-scattered Stokes light generated in the sensing fiber (6) by the laser output from the first pulse laser (1) and the Raman-scattered anti-Stokes light generated in the sensing fiber (6) by the laser output from the second pulse laser (2). The computer (9) calculates the temperature information along the sensing fiber (6) using the following formula: ； in, Indicates that the sensing fiber is in Temperature at location This indicates the laser output from the second pulse laser in the sensing fiber. The Raman back-stokes light generated at the position and the laser output from the first pulse laser pass through the sensing fiber. The ratio of the intensity of the Raman backward Stokes light generated at the location; Boltzmann's constant, For Raman frequency shift, Let be Planck's constant. This represents the ratio of the incident power of the laser output from the first laser to the incident power of the second laser.

2. The Raman distributed fiber optic temperature sensing device for temperature detection in smart mines according to claim 1, characterized in that, The optical amplification module (4) includes a first optical amplifier (10) and a second optical amplifier (11).

3. The Raman distributed fiber optic temperature sensing device for temperature detection in smart mines according to claim 1, characterized in that, The wavelength of the first pulsed laser (1) is 1350nm, and the wavelength of the second pulsed laser is 1550nm; The wavelength division multiplexer (5) has a wavelength of 1350nm at port a, 1550nm at port b, 1350nm / 1450nm / 1550nm at port c, and 1450nm at port d.

4. The Raman distributed fiber optic temperature sensing device for temperature detection in smart mines according to claim 1, characterized in that, The sensing fiber (6) has a nonlinear parameter greater than 10W. -1 km -1 Multimode nonlinear optical fiber.

5. The Raman distributed fiber optic temperature sensing device for temperature detection in smart mines according to claim 1, characterized in that, The optical switch (3) is a 2×1 multimode optical switch, and the first pulsed laser (1) and the second pulsed laser (2) are pulsed semiconductor lasers.

6. The Raman distributed fiber optic temperature sensing device for temperature detection in smart mines according to claim 1, characterized in that, The first pulsed laser (1) and the second pulsed laser (2) have the same incident power in the input sensing fiber (6).

7. The Raman distributed fiber optic temperature sensing device for temperature detection in smart mines according to claim 6, characterized in that, The computer (9) calculates the temperature information along the sensing fiber (6) using the following formula: ； in, Indicates that the sensing fiber is in Temperature at location This indicates the laser output from the second pulse laser in the sensing fiber. The Raman back-stokes light generated at the position and the laser output from the first pulse laser pass through the sensing fiber. The ratio of the intensity of the Raman backward Stokes light generated at the location; Boltzmann's constant, For Raman frequency shift, is Planck's constant.

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