Fast measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection

Abstract

The application relates to a distributed optical fiber sensing system and discloses a fast measurement BOTDA sensing device based on chaotic light polarization orthogonal detection, which comprises a narrow-line-width laser; signals output by the narrow-line-width laser are divided into two paths: one path is used as injection light to enter a chaotic light generation module to make the module output chaotic light with a wide spectrum, the chaotic light is used as detection light and sequentially connected with one end of a sensing optical fiber after passing through an optical isolator, an electro-optic modulator, a polarization maintaining optical fiber and an erbium-doped fiber amplifier; the other path is used as pump light and sequentially connected with the other end of the sensing optical fiber after passing through a semiconductor optical amplifier and a first circulator; after polarization orthogonal detection light is transmitted to the other end of the sensing optical fiber, the polarization orthogonal detection light is output through a first circulator output end and is coherently detected and data processed by a coherent detection module to obtain a Brillouin gain spectrum of the sensing optical fiber along a line. The application can realize Brillouin gain sweep-free measurement and improve the measurement speed.

Description

Technical Field

[0001] This invention relates to distributed fiber optic sensing systems, specifically a rapid measurement BOTDA (Brillouin Optical Time Domain Analysis) sensing device based on chaotic optical polarization orthogonal detection. Background Technology

[0002] Slope deformation monitoring is a crucial aspect of geological engineering safety control, requiring sensing technologies to possess long sensing distances, high measurement accuracy, and real-time dynamic response capabilities. Stimulated Brillouin Scattering (BOTDA)-based optical time-domain analysis (OTDA) technology has been adopted for slope deformation measurement due to its advantages such as large measurement range, high spatial resolution, and high measurement accuracy. However, limitations imposed by factors such as averaging times, frequency switching time, and sweep frequency step size restrict the measurement speed of traditional BOTDA, often requiring several minutes to complete a single measurement, thus limiting its application in rapid dynamic measurements.

[0003] Currently, several methods have been proposed to improve the measurement speed of BOTDA sensors. For example, the ramp-assisted method fixes the frequency difference between the pump and probe beams near the linear region of the rising or falling ramp of the Brillouin gain spectrum, achieving dynamic strain measurement by demodulating the probe beam power. However, this technique is typically limited to measuring dynamic strain at specific points on the sensing fiber, restricting its engineering applications. Frequency agility utilizes a high-performance arbitrary waveform generator to perform IQ modulation on a vector microwave source, thereby rapidly sweeping the probe beam, reducing the frequency switching time from milliseconds to nanoseconds. However, frequency agility technology places high demands on the arbitrary waveform generator or digital signal processor, significantly increasing system cost and hindering engineering applications. Optical frequency comb technology introduces a frequency comb into the pump or probe beam to demodulate the Brillouin gain spectrum, achieving frequency sweep-free operation. However, because optical frequency combs are susceptible to dispersion and nonlinear effects in optical fibers, low-dispersion fibers and phase compensation techniques are required, increasing system complexity. Optical chirped chaining modulates pump or probe light into linearly swept pulses to obtain the Brillouin gain spectrum. Due to the rapid frequency change of the probe light, the obtained Brillouin spectrum shape no longer maintains the Lorentz line shape, requiring line shape compensation during frequency shift extraction. Polarization orthogonal detection technology adjusts the polarization states of the high- and low-frequency sideband light generated by carrier-suppressed modulation to orthogonality, causing them to undergo stimulated Brillouin gain and loss processes simultaneously with the pump light in the sensing fiber. The scattered light, differentially collected by a balanced detector, is independent of polarization state, thus reducing the number of signal averaging operations. However, the main method for achieving orthogonality of the polarization states of high- and low-frequency probe light currently involves using a dense wavelength division multiplexer to split the high-frequency and low-frequency sidebands of the probe light, and then adjusting their polarization states separately. This process often introduces multiple devices, leading to system instability. Furthermore, existing polarization orthogonal detection techniques can only reduce the averaging time for eliminating polarization noise; frequency sweeping is still required to obtain the complete Brillouin gain spectrum, limiting the system measurement speed due to the sweep time.

[0004] In summary, existing BOTDA measurement devices need to be improved to address issues such as slow measurement speed, system complexity, or high cost. Summary of the Invention

[0005] To address the technical problems of slow measurement speed, system complexity, or high cost in existing BOTDA systems, this invention proposes a rapid measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection. It utilizes a broadband chaotic light source as the probe light to achieve frequency sweep-free Brillouin gain measurement, and combines polarization orthogonal detection technology to reduce the averaging number, thereby realizing rapid measurement using Brillouin optical time-domain analysis technology.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a fast measurement BOTDA sensing device based on chaotic light polarization orthogonal detection, comprising a narrow linewidth laser; the signal output by the narrow linewidth laser is split into two paths: one path is injected as injection light into a chaotic light generation module to output a wide-spectrum chaotic laser, the chaotic laser is used as probe light and passes sequentially through an optical isolator, an electro-optic modulator, a polarization-maintaining fiber, and an erbium-doped fiber amplifier before being connected to one end of a sensing fiber; the other path is used as pump light and passes sequentially through a semiconductor optical amplifier and a first circulator before being connected to the other end of the sensing fiber.

[0007] The electro-optic modulator is used to modulate the chaotic laser into a high- and low-frequency double-sideband probe light, and the polarization-maintaining fiber is used to adjust the high-frequency sideband and low-frequency sideband in the high- and low-frequency double-sideband probe light to a polarization-orthogonal state to obtain polarization-orthogonal probe light; the semiconductor optical amplifier is used to pulse modulate the pump light.

[0008] After the polarization orthogonal probe light is transmitted to the other end of the sensing fiber, it is output through the first circulator output terminal and coherently detected and processed by the coherent detection module to obtain the Brillouin gain spectrum along the sensing fiber.

[0009] The chaotic light generation module includes: a distributed feedback laser, a second circulator, a first coupler, a second coupler, an attenuator, a first polarization controller, and a second polarization controller; the output of the distributed feedback laser is connected to the reflecting end of the second circulator via the second polarization controller, the output of the second circulator is connected to the input of the second coupler, the first output of the second coupler is connected to the first input of the first coupler via the attenuator and the first polarization controller, the output of the first coupler is connected to the incident end of the second circulator, and the second input of the first coupler is connected to the output of the narrow linewidth laser.

[0010] The aforementioned fast measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection further includes a microwave signal source and a pulse generator. The microwave signal source is used to drive the electro-optic modulator, and the pulse generator is used to drive the semiconductor optical amplifier.

[0011] The polarization-maintaining fiber is fused to the slow axis of the polarization-maintaining pigtail of the electro-optic modulator at a 45° angle.

[0012] The fast measurement BOTDA sensing device based on chaotic light polarization orthogonal detection further includes a polarization-maintaining coupler and a third polarization controller. The input end of the polarization-maintaining coupler is connected to the output end of the narrow linewidth laser, the first output end is connected to the light injection end of the chaotic light generation module, and the second output end is connected to the input end of the semiconductor optical amplifier.

[0013] The third polarization controller is positioned between the optical isolator and the electro-optic modulator to adjust the polarization state of the chaotic light.

[0014] The aforementioned fast measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection further includes a third coupler. The second output terminal of the polarization-maintaining coupler is connected to the input terminal of the third coupler, and the first output terminal of the third coupler is connected to the input terminal of the semiconductor optical amplifier. The second output terminal of the third coupler is used to output a reference optical signal to the coherent detection module.

[0015] The aforementioned fast measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection further includes a seventh coupler, which is used to split the reference optical signal into two beams, and the two beams of reference optical signal are used to beat the high-frequency sideband and low-frequency sideband output in the sensing optical fiber, respectively.

[0016] The coherent detection module includes a fourth coupler, a first filter, a second filter, a fifth coupler, a sixth coupler, a balanced detector, and a data acquisition and processing unit. The polarization-orthogonal detection light output from the output of the first circulator is split into two beams by the fourth coupler. One beam is filtered by the first filter to remove high-frequency sidebands and then beats with the first reference light in the fifth coupler. The other beam is filtered by the second filter to remove low-frequency sidebands and then beats with the second reference light in the sixth coupler. The two beat signals are differentially acquired by the balanced detector and then sent to the data acquisition and processing unit for data processing.

[0017] The data acquisition and processing unit is used to process the signal of the balanced detector through windowed Fourier transform to obtain the Brillouin gain spectrum along the sensing fiber.

[0018] The linewidth of the narrow-linewidth laser is less than 10 kHz.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. Significantly Improved Measurement Speed: Traditional BOTDA technology requires several minutes for a single measurement, making it unsuitable for early warning of sudden slope changes in extreme environments. This invention utilizes the wide-spectrum characteristics of chaotic lasers as probe light to achieve frequency-sweep-free measurement, obtaining complete Brillouin gain spectrum information in a single operation, eliminating the frequency sweep process and improving measurement speed. Combined with polarization orthogonal detection technology to reduce signal averaging, the measurement time is shortened to ≤0.1 seconds (an improvement of 3 orders of magnitude), enabling the capture of dynamic slope deformation processes caused by sudden disasters such as rainstorms and earthquakes.

[0021] 2. Reduced system cost and high stability: Existing technologies such as frequency agile conversion and optical frequency comb rely on high-performance hardware (such as arbitrary waveform generators and femtosecond lasers), which are costly and complex to debug. This invention eliminates the need for frequency sweeping and polarization interference modules by using chaotic light frequency sweeping-free and polarization orthogonal detection frequency sweeping-free design, reducing hardware cost by more than 10% and improving system stability. It is suitable for long-distance monitoring in the field (such as a sensing distance of 10 km).

[0022] 3. High measurement accuracy: Traditional techniques are affected by polarization fading and noise, resulting in strain measurement errors ≥10 με; this invention uses a balanced detector to differentially acquire polarization-orthogonal Brillouin gain / loss spectra, effectively suppressing common-mode noise and further improving strain measurement accuracy;

[0023] 4. True distributed dynamic measurement: Existing technologies such as the slope-assisted method can only monitor specific points on the optical fiber and cannot cover the entire slope; this invention realizes distributed strain measurement (sensing distance 10km) through chaotic optical broadband spectrum and windowed Fourier transform, and supports dynamic response frequencies above 100Hz, which can simultaneously acquire the surface deformation and internal stress distribution of the slope.

[0024] In summary, this invention proposes a rapid measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection. It utilizes the stimulated Brillouin scattering effect between the wide-spectrum chaotic probe light and the narrow-linewidth pump light in the sensing fiber, which can obtain complete Brillouin gain spectrum information without frequency sweeping, thereby realizing rapid and high-precision measurement of distributed strain. Moreover, the device has a simple structure and low cost. Attached Figure Description

[0025] Figure 1 A schematic diagram of the structure of a fast measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection provided in an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram illustrating the modulation principle of the pump light in an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the polarization orthogonal modulation principle of the probe light in an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram illustrating the principle of sliding processing through windowed Fourier transform in an embodiment of the present invention.

[0029] In the diagram: 1. Narrow linewidth laser; 2. Polarization-maintaining coupler; 3. First coupler; 4. First polarization controller; 5. Attenuator; 6. Second circulator; 7. Second polarization controller; 8. Distributed feedback laser; 9. Second coupler; 10. Optical isolator; 11. Third polarization controller; 12. Electro-optic modulator; 13. Microwave signal source; 14. Fusion splice; 15. Polarization-maintaining fiber; 16. Erbium-doped fiber amplifier; 17. Sensing fiber; 18. Third coupler; 19. Semiconductor optical amplifier; 20. Pulse generator; 21. First circulator; 22. Fourth coupler; 23. First filter; 24. Fifth coupler; 25. Second filter; 26. Sixth coupler; 27. Seventh coupler; 28. Balanced detector; 29. ​​Data acquisition and processing unit. Detailed Implementation

[0030] 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.

[0031] like Figure 1 As shown, this embodiment of the invention provides a fast measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection, including a narrow-linewidth laser 1. The signal output from the narrow-linewidth laser 1 is split into two paths by a polarization-maintaining coupler 2: one path is injected into a chaotic light generation module to generate a wide-spectrum chaotic laser with a flat output spectrum. The chaotic laser passes sequentially through an optical isolator 10, an electro-optic modulator 12, a polarization-maintaining fiber 15, and an erbium-doped fiber amplifier 16 before being connected to one end of the sensing fiber 17; the other path is used as pump light, passing sequentially through a semiconductor optical amplifier 19 and a first circulator 21 before being connected to the other end of the sensing fiber 17. The polarization orthogonal detection light is transmitted in the sensing fiber 17 to the other end of the sensing fiber 17, and is output through the output end of the first circulator 21. It is then coherently detected and processed by a coherent detection module to obtain the Brillouin gain spectrum along the sensing fiber 17.

[0032] Specifically, in this embodiment, a wide-spectrum chaotic laser refers to a chaotic laser with a spectral width greater than or equal to 500MHz.

[0033] The semiconductor optical amplifier 19 is used to pulse-modulate the pump light. For example... Figure 2 As shown, after passing through the semiconductor optical amplifier, the continuous pump light with frequency V0 is converted into pulsed light. The electro-optic modulator 12 is used to modulate the broadband chaotic laser into high- and low-frequency double-sideband probe light. Assuming the modulation frequency of the electro-optic modulator 12 is V0...B If the center frequency of the chaotic laser output by the chaotic light generation module is V0, then the frequency of the high-frequency sideband in the high- and low-frequency double-sideband probe light is V0 + V. B The frequency of the low-frequency sideband is V0-V B The polarization-maintaining fiber 15 is used to adjust the high-frequency sideband and low-frequency sideband in the high- and low-frequency double-sideband probe light to a polarization-orthogonal state, thereby obtaining polarization-orthogonal probe light.

[0034] Specifically, such as Figure 1 As shown, in this embodiment, the chaotic light generation module includes: a distributed feedback laser 8, a second circulator 6, a first coupler 3, a second coupler 9, an attenuator 5, a first polarization controller 4, and a second polarization controller 7; the output end of the distributed feedback laser 8 is connected to the reflecting end of the second circulator 6 via the second polarization controller 7, the output end of the second circulator 6 is connected to the input end of the second coupler, the first output end of the second coupler 9 is connected to the first input end of the first coupler 3 via the attenuator 5 and the first polarization controller 4, the output end of the first coupler 3 is connected to the incident end of the second circulator 6, and the second input end of the first coupler 3 is connected to the output end of the narrow linewidth laser 1.

[0035] In this embodiment, the laser output from the distributed feedback laser 8 is split into two parts by the second coupler 9. The laser output from the first output terminal of the second coupler 9, as feedback light, is incident on the first coupler 3 after its intensity and polarization are adjusted by the attenuator 5 and the first polarization controller 4. The first coupler 3 couples the injection light and feedback light output from the narrow linewidth laser 1 together and returns them to the distributed feedback laser 8 through the second circulator 6. Under the action of the injection light and feedback light, the distributed feedback laser 8 is disturbed, causing it to output a chaotic laser with a flat spectrum. The second polarization controller 7 is located at the output port of the distributed feedback laser 8 and is used to adjust the polarization of the injection light and feedback light injected into the distributed feedback laser 8. The chaotic laser is output from the second output terminal of the second coupler 9.

[0036] Furthermore, the fast measurement BOTDA sensing device based on chaotic light polarization orthogonal detection in this embodiment also includes a microwave signal source 13 and a pulse generator 20. The microwave signal source 13 is used to drive the electro-optic modulator 12, and the pulse generator 20 is used to drive the semiconductor optical amplifier 19. The optical isolator 10 is used to prevent backlight interference with the light source stability of the chaotic laser output by the chaotic light generation module.

[0037] Furthermore, in this embodiment, the polarization-maintaining fiber 15 is fused to the slow axis of the polarization-maintaining pigtail of the electro-optic modulator 12 at a 45° angle, such as... Figure 1As shown, fusion splice 14 is located between polarization-maintaining fiber 15 and the polarization-maintaining pigtail of electro-optic modulator 12. The length of polarization-maintaining fiber 15 is determined by the frequency difference between the high and low frequency sidebands. Utilizing the differential group delay characteristics of polarization-maintaining fiber, the polarization states of the high-frequency and low-frequency sidebands can be adjusted to be mutually orthogonal after transmission through polarization-maintaining fiber 15, resulting in orthogonally polarized probe light. Figure 3 As shown, in the polarized orthogonal probe light obtained in this embodiment, the frequency is V0+V B The polarization direction of the high-frequency sideband is the X direction, and the frequency is V0-V. B The polarization direction of the low-frequency sideband is the Y direction. Here, V0 represents the frequency of the pump light, and V... B This indicates the modulation frequency of the electro-optic modulator 12, which is equal to the Brillouin frequency shift of 10.8 GHz (depending on the sensing fiber used).

[0038] Furthermore, the fast measurement BOTDA sensing device based on chaotic light polarization orthogonal detection in this embodiment also includes a polarization-maintaining coupler 2. The input end of the polarization-maintaining coupler 2 is connected to the output end of the narrow linewidth laser 1, the first output end is connected to the light injection end of the chaotic light generation module, and the second output end is connected to the input end of the semiconductor optical amplifier 19.

[0039] Furthermore, the fast measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection in this embodiment also includes a third coupler 18. The second output terminal of the polarization-maintaining coupler 2 is connected to the input terminal of the third coupler 18, and the first output terminal of the third coupler 18 is connected to the input terminal of the semiconductor optical amplifier 19. The second output terminal of the third coupler 18 is used to output a reference optical signal to the coherent detection module.

[0040] Furthermore, the fast measurement BOTDA sensing device based on chaotic optical polarization orthogonal detection in this embodiment also includes a seventh coupler 27. The seventh coupler 27 is used to split the reference optical signal into two beams: a first reference beam and a second reference beam. The two beams of reference optical signals are used to beat the high-frequency sideband and low-frequency sideband output from the sensing fiber 17, respectively. Specifically, the second output terminal of the third coupler 18 is connected to the input terminal of the seventh coupler 27.

[0041] Specifically, in this embodiment, the coherent detection module includes a fourth coupler 22, a first filter 23, a second filter 25, a fifth coupler 24, a sixth coupler 26, a balanced detector 28, and a data acquisition and processing unit 29. The polarization-orthogonal detection light output from the output end of the first circulator 21 is split into two beams by the fourth coupler 22. One beam is filtered by the first filter 23 to remove high-frequency sidebands and then beats with the first reference light in the fifth coupler 24. The other beam is filtered by the second filter 25 to remove low-frequency sidebands and then beats with the second reference light in the sixth coupler 26. The two beat signals are differentially acquired by the balanced detector 28 to obtain Brillouin scattering signals independent of polarization state, which are then sent to the data acquisition and processing unit 29 for data processing. The data acquisition and processing unit 29 performs sliding processing on the broadband Brillouin scattering information obtained by differential acquisition through windowed Fourier transform, and finally obtains the Brillouin spectrum information at each position along the sensing fiber 17, realizing distributed measurement. Figure 4 As shown, a window function of a certain width is used to window and truncate the acquired broadband Brillouin time-series information, and Fourier transform is performed on the truncated signal to obtain the corresponding Brillouin gain curve; Brillouin gain curves at different positions are obtained by sliding the window function; and the series of Brillouin gain curves are reconstructed into a Brillouin gain spectrum.

[0042] Furthermore, in this embodiment, the data acquisition and processing unit 29 is used to process the signal of the balanced detector 28 through windowed Fourier transform to obtain the Brillouin gain spectrum along the sensing fiber 17.

[0043] Specifically, in this embodiment, the linewidth of the narrow linewidth laser 1 is less than 10 kHz.

[0044] Specifically, in this embodiment, polarization-maintaining coupler 2 is a 1×2 fiber optic polarization-maintaining coupler with a splitting ratio of 50:50; the first coupler 3 is a 1×2 fiber optic coupler with a splitting ratio of 30:70, wherein the 30% port and the 70% port are respectively connected to the first output terminal of polarization-maintaining coupler 2 and the output terminal of the first polarization controller 4; the third coupler 18 has a splitting ratio of 30:70, wherein the 30% port and the 70% port are respectively connected to the input terminal of the seventh coupler 27 and the input terminal of the semiconductor optical amplifier 19; the second coupler 9, the fourth coupler 22, the fifth coupler 24, the sixth coupler 26, and the seventh coupler 27 are all 1×2 fiber optic couplers with a splitting ratio of 50:50.

[0045] The working principle of this invention is as follows:

[0046] 1. The laser emitted by the narrow linewidth laser 1 is split by the polarization-maintaining coupler 2, and a beam of injection light is injected into the distributed feedback laser 8 through the optical feedback loop formed by the second circulator 6, the first coupler 3, the second coupler 9, the attenuator 5, and the first polarization controller 4. The loop perturbation control is applied to generate a broadband chaotic laser with a flat spectrum, and the laser enters the detection optical path of the sensing system.

[0047] 2. The chaotic laser enters the detection optical path as the probe light. In the detection optical path, after the polarization is controlled by the optical isolator 10 and the third polarization controller 11, it is carrier-suppressed and modulated by the electro-optic modulator 12 to generate double-sideband probe light. After the double-sideband probe light passes through a polarization-maintaining fiber 15 of a specific length fused at a 45° angle to the slow axis of the polarization-maintaining pigtail of the electro-optic modulator 12, the polarization states of its high-frequency sideband light and low-frequency sideband light are adjusted to an orthogonal state. The resulting orthogonal polarization probe light is amplified by the erbium-doped fiber amplifier 16 and then incident on the sensing fiber 17.

[0048] 3. The light split from the second output of the polarization-maintaining coupler 2 passes through the third coupler 18. Part of the light enters the pump optical path, where it is modulated into pulse pump light by the semiconductor optical amplifier 19 driven by the pulse generator 20. The pulse pump light then passes through the first circulator 21 and enters from the other end of the single-mode sensing fiber 17. The other part of the light is split into two beams by the seventh coupler 27 as reference light, namely the first reference light and the second reference light.

[0049] 4. The polarized orthogonal probe light and the pulsed pump light incident from the other end of the sensing fiber 17 undergo stimulated Brillouin scattering in the sensing fiber 17.

[0050] 5. After scattering, the polarized orthogonal probe light carrying Brillouin scattering information is output from the first circulator 21 and split into two beams by the fourth coupler 22. One beam is filtered by the first filter 23 to remove high-frequency sidebands and then beats with the first reference light in the fifth coupler 24. The other beam is filtered by the second filter 25 to remove low-frequency sidebands and then beats with the second reference light in the sixth coupler 26. The two beat signals are differentially acquired by the balanced detector 28 to effectively suppress common-mode noise and obtain Brillouin scattering signals independent of polarization state. These signals are then sent to the data acquisition and processing unit 29 for data processing. The data acquisition and processing unit 29 performs sliding processing on the broadband Brillouin scattering information obtained by differential acquisition through windowed Fourier transform, and finally obtains the Brillouin spectrum information at each position along the sensing fiber 17, thereby realizing rapid and high-precision measurement of distributed strain and temperature.

[0051] In summary, this invention provides a rapid measurement BOTDA sensing device based on chaotic light polarization orthogonal detection. The output laser of the narrow linewidth laser 1 is divided into two parts. One part is used as the injection light chaotic light generation module to perturb it so that it outputs broadband chaotic light as the probe light. The other part is used as the pump light injected into the sensing fiber 17. The broadband chaotic probe light and the narrow linewidth pulse pump light undergo stimulated Brillouin scattering in the sensing fiber 17. It can obtain complete Brillouin gain spectrum information without frequency sweeping, realize distributed strain rapid measurement, and improve the measurement speed.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 BOTDA sensing device based on fast measurement of chaotic light polarization quadrature detection, characterized in that, The system comprises a narrow linewidth laser (1), a chaos light generating module, a sensor fiber (17), a first circulator (21), a coherent detection module, a microwave signal source (13) and a pulse generator (20). The narrow linewidth laser (1) outputs a signal which is divided into two paths: one path is used as injection light to enter the chaos light generating module to output wide spectrum chaos laser, and the chaos laser is used as probe light to connect with one end of the sensor fiber (17) after passing through an optical isolator (10), an electro-optical modulator (12), a polarization maintaining fiber (15) and an erbium-doped fiber amplifier (16) in sequence; the other path is used as pump light to connect with the other end of the sensor fiber (17) after passing through a semiconductor optical amplifier (19) and the first circulator (21) in sequence. The electro-optical modulator (12) is used for modulating the chaos laser into high-low frequency double sideband probe light, the polarization maintaining fiber (15) is used for adjusting the high frequency sideband and the low frequency sideband in the high-low frequency double sideband probe light into polarization orthogonal state to obtain polarization orthogonal probe light, and the semiconductor optical amplifier (19) is used for pulse modulation of the pump light.

2. The BOTDA sensing device based on chaotic light polarization quadrature detection according to claim 1, wherein, After the polarization orthogonal probe light is transmitted to the other end of the sensor fiber (17), the polarization orthogonal probe light is output from the output end of the first circulator (21) and is subjected to coherent detection and data processing by the coherent detection module to obtain the Brillouin gain spectrum of the sensor fiber (17) along the line.

3. The BOTDA sensor device based on chaotic light polarization orthogonal detection according to claim 1, characterized in that, The chaos light generating module comprises a distributed feedback laser (8), a second circulator (6), a first coupler (3), a second coupler (9), an attenuator (5), a first polarization controller (4) and a second polarization controller (7).

4. The BOTDA sensor device based on chaotic light polarization orthogonal detection according to claim 1, characterized in that, The output end of the distributed feedback laser (8) is connected with the reflection end of the second circulator (6) after passing through the second polarization controller (7), the output end of the second circulator (6) is connected with the input end of the second coupler (9), the first output end of the second coupler (9) is connected with the first input end of the first coupler (3) after passing through the attenuator (5) and the first polarization controller (4) in sequence, the output end of the first coupler (3) is connected with the incidence end of the second circulator (6), and the second input end of the first coupler (3) is connected with the output end of the narrow linewidth laser (1). The microwave signal source (13) is used for driving the electro-optical modulator (12), and the pulse generator (20) is used for driving the semiconductor optical amplifier (19). The polarization maintaining fiber (15) is fused with the slow axis of the polarization maintaining tail fiber of the electro-optical modulator (12) at an angle of 45°. The system further comprises a polarization maintaining coupler (2) and a third polarization controller (11), the input end of the polarization maintaining coupler (2) is connected with the output end of the narrow linewidth laser (1), the first output end is connected with the light injection end of the chaos light generating module, and the second output end is connected with the input end of the semiconductor optical amplifier (19). The third polarization controller (11) is arranged between the optical isolator (10) and the electro-optical modulator (12) and is used for adjusting the polarization state of the chaos light.

5. The BOTDA sensor device based on chaotic light polarization quadrature detection according to claim 4, characterized in that, The third coupler (18) is further included, the second output end of the polarization maintaining coupler (2) is connected with the input end of the third coupler (18), the first output end of the third coupler (18) is connected with the input end of the semiconductor optical amplifier (19), and the second output end of the third coupler (18) is used for outputting the reference light signal to the coherent detection module.

6. The BOTDA sensor device based on chaotic light polarization quadrature detection according to claim 5, characterized in that, The seventh coupler (27) is further included, the seventh coupler (27) is used for dividing the reference light signal into two beams, and the two beams of reference light signals are respectively used for beating with the high-frequency sideband and the low-frequency sideband output in the sensing optical fiber (17).

7. The BOTDA sensor device based on chaotic light polarization orthogonal detection according to claim 1, characterized in that, The coherent detection module includes a fourth coupler (22), a first filter (23), a second filter (25), a fifth coupler (24), a sixth coupler (26), a balanced detector (28) and a data acquisition processing unit (29), the polarization quadrature detection light output through the output end of the first circulator (21) is divided into two beams by the fourth coupler (22), one of the two beams is beat with the first reference light in the fifth coupler (24) after the high-frequency sideband is filtered through the first filter (23), the other beam is beat with the second reference light in the sixth coupler (26) after the low-frequency sideband is filtered through the second filter (25), the two beat signals are differentially collected through the balanced detector (28) and then sent to the data acquisition processing unit (29) for data processing.

8. The BOTDA sensor device based on chaotic light polarization quadrature detection according to claim 7, characterized in that, The data acquisition processing unit (29) is used for performing data processing on the signal of the balanced detector (28) through windowed Fourier transform, so as to obtain the Brillouin gain spectrum of the sensing optical fiber (17) along the line.

9. The BOTDA sensor device based on chaotic light polarization orthogonal detection according to claim 1, characterized in that, The linewidth of the narrow linewidth laser (1) is less than 10 kHz.

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