Raman high-resolution sensing device and method based on cosine and sine differential pulses

Abstract

The invention relates to the technical field of distributed optical fiber sensing, and discloses a Raman high-resolution sensing device and method based on cosine and sine differential pulses. The device comprises a laser device, after laser output by the laser device is modulated by an electro-optical modulator, the output modulated laser enters a sensing optical fiber after passing through a wavelength division multiplexer; a Raman backward scattering light signal output from the sensing optical fiber is output by the wavelength division multiplexer, is detected by the photoelectric detector, is converted into an electric signal, is acquired by the data acquisition card, and is sent to the computer for data processing; the sine and cosine waveform generator is used for sequentially outputting a single-cycle cosine signal and a single-cycle sine signal to drive the electro-optical modulator, so that the electro-optical modulator outputs a cosine laser signal and a sine laser signal; and the computer is used for calculating the temperature along the optical fiber according to the difference value of the Raman backward scattering light signal excited by the cosine laser signal and the sine laser signal. The method can improve the spatial resolution and reduce the sampling rate requirement.

Description

Technical Field

[0001] The invention relates to the technical field of distributed optical fiber sensing, in particular to a Raman high-resolution sensing device and method based on cosine and sine differential pulses. Background Art

[0002] Raman distributed fiber optic sensing technology uses the functional relationship between the intensity of Raman scattering signals and temperature in optical fibers to detect temperature changes at different locations along the sensing fiber. Spatial resolution characterizes the minimum fiber length that the sensing fiber can resolve, and is an extremely important technical indicator of Raman distributed fiber optic sensing technology. When the length of the optical fiber to be measured is less than the spatial resolution of the system, the temperature measured by the system will be less than the actual ambient temperature. Therefore, the spatial resolution of the Raman distributed fiber optic sensing system can also reflect the minimum length of optical fiber required for the system to accurately measure the ambient temperature.

[0003] The detection signals used in the Raman distributed fiber optic sensing system are all pulse signals. Its positioning principle is the pulse time flight method, and the spatial resolution mainly depends on the half-maximum full width of the light source pulse. Limited by the half-maximum full width of the light source pulse, the spatial resolution of the existing Raman distributed fiber optic system is limited to the meter level. In addition, as the sensing distance increases, the fiber dispersion will cause the light source pulse width to broaden, and ultimately the spatial resolution of the system will further deteriorate with the increase of the sensing distance. Its spatial resolution performance reaches several meters or even tens of meters at the end of the optical fiber, which greatly limits the application of Raman distributed fiber optic sensing technology.

[0004] In addition, the optimal effective number of sensing points for existing long-distance Raman distributed fiber optic sensing technology is 60,000. How to restore the real signal in the temperature change zone under a lower sampling rate is also a problem that the fiber optic sensing system needs to solve.

[0005] At present, Raman distributed fiber optic sensing technology urgently needs to realize high spatial resolution temperature sensing monitoring under low sampling rate conditions. Based on this, it is necessary to improve the existing Raman distributed fiber optic sensing device and temperature demodulation method to solve the technical bottleneck of the existing Raman distributed fiber optic sensing system. Summary of the invention

[0006] In order to solve the technical bottleneck that the spatial resolution of the traditional Raman optical time-domain reflectometry distributed optical fiber sensing system cannot exceed the meter level under low sampling rate conditions, the present invention proposes a Raman high-resolution sensing device and method based on cosine and sine differential pulses to meet the requirements of Raman distributed optical fiber sensing technology for high spatial resolution.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a Raman high-resolution sensing device based on cosine and sine differential pulses, comprising: a laser, an electro-optical modulator, a trigger signal generator, a sine-cosine waveform generator, a wavelength division multiplexer, a sensing optical fiber, a photodetector, a data acquisition card, and a computer. The laser output by the laser is modulated by the electro-optical modulator, and the output modulated laser enters the sensing optical fiber after passing through the wavelength division multiplexer. The Raman backscattered light signal output from the sensing optical fiber is output by the wavelength division multiplexer, detected by the photodetector, and converted into an electrical signal, which is collected by the data acquisition card and sent to the computer for data processing.

[0008] The sine-cosine waveform generator is used to sequentially output a single-cycle cosine signal and a sine signal to drive the electro-optical modulator so that it outputs a cosine laser signal and a sine laser signal;

[0009] The trigger signal generator is used to output a trigger signal to simultaneously trigger the sine-cosine waveform generator and the data acquisition card, so that the data acquisition card respectively acquires the corresponding cosine laser signal and the Raman backscattered light signal excited by the sine laser signal;

[0010] The computer is used to calculate the temperature along the optical fiber according to the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal.

[0011] The temperature calculation formula along the optical fiber is:

[0012]

[0013] Where T represents the temperature in the temperature change zone, Δv is the Raman frequency shift, h is the Planck constant, k is the Boltzmann constant, and T 0 is the calibration temperature of the sensing fiber, Φ Diff (T, L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the position of the optical fiber L during the measurement phase; Φ Diff (T 0 , L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the optical fiber L position during the calibration phase.

[0014] The sine signal and cosine signal output by the sine-cosine waveform generator have the same period.

[0015] The Raman backscattered light signal detected by the photoelectric detector is a Raman backscattered anti-Stoke light signal.

[0016] The computer obtains the position and length of the temperature change zone through the position of the point with equal intensity in the intensity change area of ​​the Raman backscattered light signal.

[0017] The trigger signal generator is an arbitrary signal generator, and the sine and cosine waveform generator is an arbitrary waveform generator; the laser is a distributed feedback continuous laser with a central wavelength of 1550nm.

[0018] The Raman high-resolution sensing device based on cosine and sine differential pulses also includes an erbium-doped fiber amplifier, which is arranged between the electro-optic modulator and the wavelength division multiplexer and is used to amplify the intensity of the laser signal output by the electro-optic modulator.

[0019] In addition, the present invention also provides a Raman high-resolution sensing method based on cosine and sine differential pulses, which is implemented based on the above-mentioned Raman high-resolution sensing device based on cosine and sine differential pulses, and includes the following steps:

[0020] Step 1: Keep the temperature of the sensing fiber at T during the calibration phase 0 , so that the sine and cosine waveform generator outputs a single-cycle cosine signal and a sine signal to drive the electro-optical modulator, so that the electro-optical modulator sequentially outputs a cosine laser signal and a sine laser signal; collects the Raman backscattered light signal Φ corresponding to the cosine laser signal and the sine laser signal in the calibration stage acos (T 0 ,L) and Φ asin (T 0 ,L), and calculate its difference value Φ Diff (T 0 ,L);Φ Diff (T 0 , L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal in the calibration stage;

[0021] Step 2: In the measurement phase, the sine-cosine waveform generator outputs a single-cycle cosine signal and a sine signal to drive the electro-optical modulator, so that the electro-optical modulator sequentially outputs a cosine laser signal and a sine laser signal; and the Raman backscattered light signal Φ corresponding to the cosine laser signal and the sine laser signal in the measurement phase is collected. acos (T,L) and Φ asin (T,L), and calculate its difference value Φ Diff (T,L); Φ Diff (T, L) represents the difference between the Raman backscattered light signals excited by the cosine laser signal and the sine laser signal during the measurement phase;

[0022] Step 3: Calculate the temperature of the temperature change zone based on the differential value in the measurement phase.

[0023] The step three also includes the following steps: determining the positions of points with equal differential values ​​in the differential value change region of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal during the measurement phase, wherein the position corresponding to the first point with equal differential values ​​is the starting point of the temperature change zone, and the position corresponding to the last point is the end point of the temperature change zone, thereby determining the position and length of the temperature change zone, and then demodulating the temperature of the temperature change zone through the differential value of the starting point or the end point.

[0024] The calculation formula of the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal in the calibration stage and the measurement stage is:

[0025] Φ Diff (T 0 ,L)=Φ acos (T 0 ,L)-Φ asin (T 0 ,L);

[0026] Φ Diff (T,L)=Φ acos (T,L)-Φ asin (T,L);

[0027] The calculation formula of the temperature in the temperature change zone is:

[0028]

[0029] Where T represents the temperature in the temperature change zone, Δv is the Raman frequency shift, h is the Planck constant, k is the Boltzmann constant, and T 0 is the calibration temperature of the sensing fiber, Φ Diff (T, L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the position of the optical fiber L during the measurement phase; Φ Diff (T 0 , L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the optical fiber L position during the calibration phase.

[0030] Compared with the existing Raman distributed optical fiber sensing system, the Raman high-resolution sensing device and method based on cosine and sine differential pulses proposed in the present invention have the following beneficial effects:

[0031] (1) The present invention uses cosine and sine differential laser signals to replace traditional square wave pulse or Gaussian pulse laser signals. The spatial resolution of the Raman optical time domain reflectometer system is inversely proportional to the half-maximum full width of the incident laser signal. Therefore, the present invention uses cosine and sine differential laser signals, and the differential laser signal has the characteristic of a small period. Under the condition that its period is ≤1ns, the corresponding system spatial resolution can reach ≤10cm. In contrast, if the half-maximum full width of the traditional square wave pulse or Gaussian pulse laser signal reaches this level, its production cost will increase greatly. Therefore, the present invention can maintain the spatial resolution of the device under the condition of reducing costs;

[0032] (2) The cosine and sine differential laser signals have the characteristic that the integral results are equal only at the beginning and end of a single cycle, that is, the intensity of the backward Raman anti-Stokes scattered light signal excited by the differential laser signal is equal only when it just enters the temperature change zone and completely enters the temperature change zone. Therefore, the position and length of the temperature change zone can be known by the position of the points with equal intensity in the intensity change area of ​​the backward Raman anti-Stokes scattered light signal. Therefore, the present invention has a low requirement for the sampling rate, and can achieve accurate positioning and demodulation of the temperature change zone under low sampling rate conditions, thereby greatly reducing the acquisition time of the sensor signal, thereby effectively improving the transmission speed of the system signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic structural diagram of a Raman high-resolution sensing device based on cosine and sine differential pulses provided in Embodiment 1 of the present invention;

[0034] Figure 2 Schematic diagram of the waveforms of the cosine modulation signal and the sine modulation signal used in the first embodiment of the present invention;

[0035] Figure 3 This is the temperature demodulation curve obtained by simulation.

[0036] In the figure: 1: laser, 2: electro-optic modulator, 3: trigger signal generator, 4: sine and cosine waveform generator, 5: erbium-doped fiber amplifier, 6: wavelength division multiplexer, 7: sensing fiber, 8: avalanche photodetector, 9: data acquisition card, 10: computer. DETAILED DESCRIPTION

[0037] In order to make the purpose, 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 part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0038] Embodiment 1

[0039] like Figure 1 As shown, the first embodiment of the present invention provides a Raman high-resolution sensing device based on cosine and sine differential pulses, comprising: a laser 1, an electro-optical modulator 2, a trigger signal generator 3, a sine-cosine waveform generator 4, a wavelength division multiplexer 6, a sensing optical fiber 7, an avalanche photodetector 8, a data acquisition card 9, and a computer 10. The laser output by the laser 1 is modulated by the electro-optical modulator 2, and the output modulated laser enters the sensing optical fiber 7 after passing through the wavelength division multiplexer 6. The Raman backscattered light signal output from the sensing optical fiber is output by the wavelength division multiplexer 6 and then detected by the photodetector 8 and converted into an electrical signal, which is collected and transmitted by the data acquisition card 9. The data are sent to the computer 10 for data processing; the sine-cosine waveform generator 4 is used to sequentially output a single-cycle cosine signal and a sine signal to drive the electro-optical modulator 2, so that it outputs a cosine laser signal and a sine laser signal; the trigger signal generator 3 is used to output a trigger signal to simultaneously trigger the sine-cosine waveform generator 4 and the data acquisition card 9, so that the data acquisition card 9 respectively collects the corresponding cosine laser signal and the Raman backscattered light signal excited by the sine laser signal; the computer 10 is used to calculate the temperature along the optical fiber according to the differential value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal.

[0040] Specifically, Figure 2 As shown, in this embodiment, the periods of the sine signal and cosine signal output by the sine-cosine waveform generator 4 are the same.

[0041] Specifically, in this embodiment, the Raman backscattered light signal detected by the avalanche photodetector 8 is a Raman backscattered anti-Stoke light signal. The computer 10 obtains the position and length of the temperature change zone by the position of the point with equal intensity in the intensity change region of the Raman backscattered light signal.

[0042] Furthermore, in this embodiment, the trigger signal generator 3 is an arbitrary signal generator, the sine and cosine waveform generator 4 is an arbitrary waveform generator; the laser 1 is a distributed feedback continuous laser with a central wavelength of 1550 nm. The data acquisition card 9 is a high-speed data acquisition card with a sampling rate greater than 200 MHz. The minimum requirement for the sampling rate is related to the period of the sine and cosine waveforms. The sampling rate satisfies the requirement that 5 sample points are collected within each sine and cosine waveform period to truly restore the signal.

[0043] Furthermore, if Figure 1As shown, a Raman high-resolution sensing device based on cosine and sine differential pulses in this embodiment also includes an erbium-doped fiber amplifier 5, which is arranged between the electro-optical modulator 2 and the wavelength division multiplexer 6, and is used to amplify the laser signal intensity output by the electro-optical modulator 2.

[0044] In this embodiment, the output end of the laser 1 is connected to the a port of the electro-optic modulator 2, the b port of the electro-optic modulator 2 is connected to the input end of the erbium-doped fiber amplifier 5, the output end of the trigger signal generator 3 is simultaneously connected to the input end of the sine-cosine waveform generator 4 and the a port of the data acquisition card 9, the output end of the sine-cosine waveform generator 4 is connected to the c port of the electro-optic modulator 2, and the output end of the erbium-doped fiber amplifier 5 is connected to the a port of the wavelength division multiplexer 6. The b port of the wavelength division multiplexer 6 is connected to the input end of the avalanche photodetector 8, the c port of the wavelength division multiplexer 6 is connected to the sensing optical fiber 7, and the output end of the avalanche photodetector 8 is connected to the b port of the data acquisition card 9. The c port of the data acquisition card 9 is connected to the computer 10, and the computer 10 processes the signal collected by the data acquisition card 9, thereby calculating the temperature change along the sensing optical fiber.

[0045] The a-port and c-port of the electro-optic modulator 2 are located at the input end, and the b-port is located at the output end. The wavelengths of the a-port and the b-port are both 1550nm, and the c-port receives an electrical signal. The a-port of the wavelength division multiplexer 6 is located at the input end, the b-port is located at the output end, and the c-port is the input / output end. The output is the laser signal input from the a-port, and the input is the Raman anti-Stokes optical signal backscattered by the sensing optical fiber. The port wavelengths are: the a-port wavelength is 1550nm, the b-port wavelength is 1450nm, and the c-port wavelength is 1450nm / 1550nm. The sensing optical fiber 7 has a nonlinear parameter greater than 10W-1km -1 The multimode nonlinear optical fiber has a core diameter of 62.5 μm. The a port and the b port of the data acquisition card 9 are located at the input end, and the c port is located at the output end.

[0046] The distributed temperature detection and demodulation principle of the present invention is introduced below.

[0047] In this embodiment, the position of the optical fiber propagation distance L is used as a reference point to obtain the Raman backward anti-Stokes scattered light signal generated in the sensing optical fiber. The laser 1 emits a stable continuous laser, which is incident on the electro-optical modulator 2 for modulation. The trigger signal generator 3 sends a trigger signal (whose high-level duration is the same as the signal period generated by the sine-cosine waveform generator 4) to simultaneously trigger the sine-cosine waveform generator 4 and the data acquisition card 9, so that the data acquisition card collects the corresponding single-cycle cosine and sine signal-excited Raman backward scattering signal. The sine-cosine waveform generator 4 sequentially sends a single-cycle cosine and sine modulation signal to the electro-optical modulator 2 to drive it to modulate the continuous laser, and finally outputs the cosine and sine laser signals at the output end of the electro-optical modulator 2. After the laser signal is amplified by the erbium-doped fiber amplifier 5, it is incident on the sensing optical fiber 7 through the wavelength division multiplexer 6, and a 1450nm Raman backward anti-Stokes scattered light signal is generated at each point along the sensing optical fiber. After passing through the wavelength division multiplexer 6, the Raman backward anti-Stokes scattered light signal is detected by the avalanche photodetector 8 and converted into an electrical signal, which is collected by the data acquisition card 9 and sent to the computer 10 for data processing, so that the temperature distribution along the sensing optical fiber can be known.

[0048] Temperature detection and demodulation can generally be divided into two stages: first, the calibration stage, in which the sensing optical fiber 7 is placed at a constant ambient temperature T 0 The sensor is calibrated during the process (usually at room temperature, also called the calibration phase, which is equivalent to setting a temperature reference for the temperature to be measured) to obtain the Raman backscattered anti-Stokes light signal intensity generated in the sensing fiber at this time; then comes the measurement phase, in which the sensing fiber is laid in the measurement environment to obtain the Raman backscattered anti-Stokes light signal intensity along the sensing fiber at this time.

[0049] The intensity of the cosine laser signal incident on the fiber incident end is expressed as:

[0050] I cos =I 0 cos(ω m t); (1)

[0051] The intensity of the sinusoidal laser signal incident on the fiber incident end is expressed as:

[0052] I sin =I 0 sin(ω m t); (2)

[0053] Among them, I 0 is the maximum power of the cosine and sine laser signal at the fiber incident end during the cycle, ω m represents the modulation frequency, and t represents the transmission time.

[0054] Only the cosine laser is incident on the sensing fiber, and the Raman anti-Stokes scattered light signal intensity collected during the calibration phase is expressed as:

[0055]

[0056] Only sinusoidal laser is incident on the sensing fiber, and the Raman anti-Stokes scattered light signal intensity collected during the calibration phase is expressed as:

[0057]

[0058] Subtracting equation (4) from equation (3) can obtain the differential Raman anti-Stokes scattered light signal intensity in the calibration stage, as shown in equation (5):

[0059]

[0060] Only the cosine laser is incident on the sensing fiber, and the Raman anti-Stokes scattered light signal intensity collected during the measurement phase is expressed as:

[0061]

[0062] Only the sinusoidal laser is incident on the sensing fiber, and the Raman anti-Stokes scattered light signal intensity collected during the measurement phase is expressed as:

[0063]

[0064] Subtracting equation (7) from equation (6) can obtain the differential Raman anti-Stokes scattered light signal intensity in the measurement phase, as shown in equation (8):

[0065]

[0066] Among them, K a represents the coefficient related to the backscattering cross section of the Raman anti-Stokes scattered light signal, S is the backscattering factor of the optical fiber, and v a Represents the frequency of the Raman anti-Stokes scattered light signal, μ a It indicates the gain amplification factor of the cosine and sine laser signals incident on the optical fiber input end, α 0 and α a R represents the loss coefficient of the incident laser signal and the Raman anti-Stokes scattered light signal in the sensing fiber, L is the position where the fiber generates the Raman anti-Stokes scattered light signal, and Q is the spatial scale corresponding to the period of the cosine and sine laser signals. a (T 0 ) and Ra (T) represents the temperature coefficient, I sin (L1) represents the intensity of the sinusoidal laser signal at position L1, I cos (Ll) represents the cosine laser signal intensity at position Ll, l represents a small distance, its lower limit is LQ, and its upper limit is L.

[0067] The expression for the temperature coefficient is as follows:

[0068] R a (T 0 )=[exp(hΔν / kT 0 )-1] -1 ; (9)

[0069] R a (T) = [exp(hΔν / kT)-1] -1 ; (10)

[0070] Where Δv is the Raman frequency shift, h is the Planck constant, k is the Boltzmann constant, and T 0 is the calibration temperature of the sensing optical fiber, which is generally room temperature, and T is the temperature to be measured.

[0071] From formula (5) and formula (8), we know that the intensity of the Raman anti-Stokes scattered light signal collected during the calibration and measurement phase is the superposition of the cosine and sine laser differential signals in the entire cycle. By finding the original function of the function expression of the cosine and sine laser signals and calculating them, we can know that the following relationship exists within one cycle:

[0072]

[0073] Among them, I cos (0)-I sin (0) represents the integral value of the cosine and sine laser differential signals in the spatial scale corresponding to the beginning of the cycle. In the Raman distributed optical fiber system, the integral value can be considered to represent the power of the cosine and sine laser differential signals when they just enter the temperature change zone of the sensing optical fiber. It represents the integral value of the cosine and sine laser differential signals in the spatial scale corresponding to the entire signal period. In the Raman distributed optical fiber system, it can be considered that the integral value represents the power of the cosine and sine laser differential signals fully coupled into the temperature change zone of the sensing optical fiber.

[0074] From formula (11), it can be seen that the cosine and sine differential laser signals have the characteristic that the integral results are equal only at the beginning and end positions of a single cycle. From this analysis, it can be seen that the differential value intensity of the backward Raman anti-Stokes scattered light signal excited just after entering the temperature change zone and completely entering the temperature change zone is equal. Therefore, through the point where the differential value intensity of the backward Raman anti-Stokes scattered light signal excited by the cosine laser signal and the sine laser signal is equal in the area where the intensity of the backward Raman anti-Stokes scattered light signal changes, the starting point and the end point of the temperature change zone can be determined, and then the position and length of the temperature change zone can be known according to the positions of these two points, and the temperature can be accurately demodulated.

[0075] Using formula (5) and formula (8), Φ Diff (T,L) and Φ Diff (T 0 ,L) compared to get:

[0076]

[0077] It can be seen from formula (12) that only the temperature T to be measured is an unknown number, and the rest are known parameters. Substituting them into the formula, the temperature along the optical fiber can be demodulated. The temperature demodulation formula is shown in formula (13).

[0078]

[0079] Where T represents the temperature in the temperature change zone, Δv is the Raman frequency shift, h is the Planck constant, k is the Boltzmann constant, and T 0 is the calibration temperature of the sensing fiber, Φ Diff (T, L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the position of the optical fiber L during the measurement phase; Φ Diff (T 0 , L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the optical fiber L position during the calibration phase.

[0080] Therefore, the difference value Φ of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal is measured. Diff (T, L), the temperature along the optical fiber can be calculated by formula (13).

[0081] like Figure 3As shown in FIG. 1 , it is a simulated temperature demodulation curve obtained when the temperature change zone corresponds to a spatial scale of 1 m, wherein the period of the sine laser signal and the cosine laser signal is 1 ns, and the corresponding spatial scale is 10 cm. By finding the position of the point where the differential value is equal in the differential value curve of the backward Raman anti-Stokes scattered light signal (which is also the position where the temperature is equal in the temperature demodulation curve), the starting point and the end point of the temperature change zone can be known, wherein the position corresponding to the first point where the differential value is equal is the starting point of the temperature change zone, and the position corresponding to the last point is the end point of the temperature change zone, then the position and size of the temperature change zone can be obtained, and then the differential value at the starting point or the end point is obtained as Φ Diff Substituting (T, L) into formula (13) can accurately decode the temperature of the temperature change zone.

[0082] In addition, it should be explained that the demodulation device of this embodiment can accurately locate the temperature change zone and accurately demodulate only when the spatial scale corresponding to the temperature change zone is equal to or greater than the spatial scale corresponding to the period of the sine or cosine laser signal. When the spatial scale corresponding to the temperature change zone is equal to the spatial scale corresponding to the period of the sine or cosine laser signal, there are only two points with equal differential values ​​in the differential value curve of the backward Raman anti-Stokes scattered light signal. When the spatial scale corresponding to the temperature change zone is greater than the spatial scale corresponding to the period of the sine or cosine laser signal, after entering the temperature change zone completely, the differential value curve corresponds to a platform area. At this time, there are several points with equal differential values ​​in the differential value curve of the backward Raman anti-Stokes scattered light signal. The corresponding position of the first point is the starting point of the temperature change zone, and the corresponding position of the last point (also the end point of the platform area) is the end point of the temperature change zone. Since the cosine and sine differential laser signals have the characteristic of a small period, under the condition that their period is ≤1ns, the spatial resolution of the system corresponding to the present invention is ≤10cm.

[0083] Furthermore, in this embodiment, the differential value curve of the backward Raman anti-Stokes scattered light signal can be derived, and the position corresponding to the first peak of the derived curve is the starting point of the temperature change zone. In addition, the end point of the temperature change zone can be determined according to the differential value of the starting point, that is, the position corresponding to the last point in the differential value curve that is equal to the differential value of the starting point is the end point.

[0084] Embodiment 2

[0085] Embodiment 2 of the present invention provides a Raman high-resolution sensing method based on cosine and sine differential pulses, which is implemented based on a Raman high-resolution sensing device based on cosine and sine differential pulses described in Embodiment 1, and includes the following steps:

[0086] Step 1: Calibration stage: Keep the temperature of the sensing fiber 7 at T 0, so that the sine-cosine waveform generator 4 outputs a single-cycle cosine signal and a sine signal to drive the electro-optical modulator 2, so that the electro-optical modulator 2 sequentially outputs a cosine laser signal and a sine laser signal; collects the Raman backscattered light signal Φ corresponding to the cosine laser signal and the sine laser signal in the calibration stage acos (T 0 ,L) and Φ asin (T 0 ,L), and calculate its difference value Φ Diff (T 0 ,L); the calculation formula is:

[0087] Φ Diff (T 0 ,L)=Φ acos (T 0 ,L)-Φ asin (T 0 ,L); (14)

[0088] Φ Diff (T 0 , L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal in the calibration stage.

[0089] Step 2: In the measurement phase, the sine-cosine waveform generator 4 outputs a single-cycle cosine signal and a sine signal to drive the electro-optical modulator 2, so that the electro-optical modulator 2 sequentially outputs a cosine laser signal and a sine laser signal; and the Raman backscattered light signal Φ corresponding to the cosine laser signal and the sine laser signal in the measurement phase is collected. acos (T,L) and Φ asin (T,L), and calculate its difference value Φ Diff (T,L); the calculation formula is:

[0090] Φ Diff (T,L)=Φ acos (T,L)-Φ asin (T,L); (15)

[0091] Φ Diff (T, L) represents the difference between the Raman backscattered light signals excited by the cosine laser signal and the sine laser signal during the measurement phase.

[0092] Step 3: Calculate the temperature of the temperature change zone according to the intensity difference value in the calibration stage and the measurement stage. The calculation formula of the temperature change zone is the above formula (13).

[0093] Furthermore, the step three also includes the following steps: determining the positions of points where the differential values ​​are equal in the differential value change area of ​​the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal during the measurement phase, wherein the corresponding position of the first point where the differential value is equal is the starting point of the temperature change zone, and the corresponding position of the last point is the end point of the temperature change zone, thereby determining the position and length of the temperature change zone, and then demodulating the temperature of the temperature change zone through the differential value of the starting point or the end point.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Raman high-resolution sensing device based on cosine and sine differential pulses, characterized in that: include: A laser (1), an electro-optic modulator (2), a trigger signal generator (3), a sine-cosine waveform generator (4), a wavelength division multiplexer (6), a sensing optical fiber (7), a photoelectric detector (8), a data acquisition card (9), and a computer (10). The laser light output by the laser (1) is modulated by the electro-optic modulator (2), and the modulated laser light output enters the sensing optical fiber (7) after passing through the wavelength division multiplexer (6). The Raman backscattered light signal output from the sensing optical fiber is output by the wavelength division multiplexer (6), detected by the photoelectric detector (8), and converted into an electrical signal, which is collected by the data acquisition card (9) and sent to the computer (10) for data processing. The sine-cosine waveform generator (4) is used to sequentially output a single-cycle cosine signal and a sine signal to drive the electro-optical modulator (2) so that it outputs a cosine laser signal and a sine laser signal; The trigger signal generator (3) is used to output a trigger signal to simultaneously trigger the sine-cosine waveform generator (4) and the data acquisition card (9), so that the data acquisition card (9) respectively acquires the corresponding cosine laser signal and the Raman backscattered light signal excited by the sine laser signal; The computer (10) is used to calculate the temperature along the optical fiber according to the difference value of the Raman backscattered light signal stimulated by the cosine laser signal and the sine laser signal.

2. A Raman high-resolution sensing device based on cosine and sine differential pulses according to claim 1, characterized in that: The temperature calculation formula along the optical fiber is: Where T represents the temperature in the temperature change zone, Δv is the Raman frequency shift, h is the Planck constant, k is the Boltzmann constant, T0 is the calibration temperature of the sensing fiber, Φ Diff (T, L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the position of the optical fiber L during the measurement phase; Φ Diff (T0, L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the optical fiber L position during the calibration phase.

3. The Raman high-resolution sensing device based on cosine and sine differential pulses according to claim 1, characterized in that: The sine signal and cosine signal output by the sine-cosine waveform generator (4) have the same period.

4. A Raman high-resolution sensing device based on cosine and sine differential pulses according to claim 1, characterized in that: The Raman backscattered light signal detected by the photoelectric detector (8) is a Raman backscattered anti-Stoke light signal.

5. The Raman high-resolution sensing device based on cosine and sine differential pulses according to claim 1, characterized in that: The computer (10) obtains the position and length of the temperature change zone through the position of the point with equal intensity in the intensity change area of ​​the Raman backscattered light signal.

6. A Raman high-resolution sensing device based on cosine and sine differential pulses according to claim 1, characterized in that: The trigger signal generator (3) is an arbitrary signal generator, and the sine and cosine waveform generator (4) is an arbitrary waveform generator; the laser (1) is a distributed feedback continuous laser with a central wavelength of 1550 nm.

7. A Raman high-resolution sensing device based on cosine and sine differential pulses according to claim 1, characterized in that: It also comprises an erbium-doped optical fiber amplifier (5), which is arranged between the electro-optical modulator (2) and the wavelength division multiplexer (6) and is used to amplify the intensity of the laser signal output by the electro-optical modulator (2).

8. A Raman high-resolution sensing method based on cosine and sine differential pulses, implemented based on a Raman high-resolution sensing device based on cosine and sine differential pulses as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: During the calibration phase, the temperature of the sensing optical fiber (7) is maintained at T0, and the sine-cosine waveform generator (4) outputs a single-cycle cosine signal and a sine signal to drive the electro-optical modulator (2), so that the electro-optical modulator (2) sequentially outputs a cosine laser signal and a sine laser signal; and the Raman backscattered light signals Φ corresponding to the cosine laser signal and the sine laser signal during the calibration phase are collected. acos (T0,L) and Φ asin (T0,L), and calculate its difference value Φ Diff (T0,L);Φ Diff (T0, L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal in the calibration stage; Step 2: In the measurement phase, the sine-cosine waveform generator (4) outputs a single-cycle cosine signal and a sine signal to drive the electro-optical modulator (2), so that the electro-optical modulator (2) sequentially outputs a cosine laser signal and a sine laser signal; and collects Raman backscattered light signals Φ corresponding to the cosine laser signal and the sine laser signal in the measurement phase. acos (T,L) and Φ asin (T,L), and calculate its difference value Φ Diff (T,L); Φ Diff (T, L) represents the difference between the Raman backscattered light signals excited by the cosine laser signal and the sine laser signal during the measurement phase; Step 3: Calculate the temperature of the temperature change zone based on the differential value in the measurement phase.

9. The Raman high-resolution sensing method based on cosine and sine differential pulses according to claim 8, characterized in that: The step three also includes the following steps: determining the positions of points with equal differential values ​​in the differential value change region of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal during the measurement phase, wherein the position corresponding to the first point with equal differential values ​​is the starting point of the temperature change zone, and the position corresponding to the last point is the end point of the temperature change zone, thereby determining the position and length of the temperature change zone, and then demodulating the temperature of the temperature change zone through the differential value of the starting point or the end point.

10. The Raman high-resolution sensing method based on cosine and sine differential pulses according to claim 8, characterized in that: The calculation formula of the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal in the calibration stage and the measurement stage is: Φ Diff (T0,L)=Φ acos (T0,L)-Φ asin (T0,L); F Diff (T,L)=Φ acos (T,L)-Φ asin (T,L); The calculation formula of the temperature in the temperature change zone is: Where T represents the temperature in the temperature change zone, Δv is the Raman frequency shift, h is the Planck constant, k is the Boltzmann constant, T0 is the calibration temperature of the sensing fiber, Φ Diff (T, L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the position of the optical fiber L during the measurement phase; Φ Diff (T0, L) represents the difference value of the Raman backscattered light signal excited by the cosine laser signal and the sine laser signal at the optical fiber L position during the calibration phase.

Images