High-speed chaotic brillouin sensing device and method based on correlation method multiple access positioning

Abstract

The application relates to the field of distributed optical fiber sensing, and discloses a high-speed chaotic Brillouin sensing device and method based on a correlation method multi-address positioning method, wherein strong periodic broadband chaotic laser is divided into two beams through a first beam splitter, one beam is used as probe light and sequentially enters a sensing optical fiber after passing through a single sideband modulator and an erbium-doped fiber amplifier; the other beam sequentially passes through an optical delay line, an erbium-doped fiber amplifier, and a second beam splitter to be divided into pump light and reference light, the pump light passes through an optical circulator and occurs stimulated Brillouin amplification with the probe light at different positions in the sensing optical fiber; the signal in the sensing optical fiber is output after passing through the optical circulator, Stokes light is filtered out by a tunable optical filter and is detected by a first photodetector, the reference light is detected by a second photodetector, a data acquisition unit collects two-way signals and sends the two-way signals to a computer for data processing; the application improves the signal-to-noise ratio of the system, widens the sensing distance, and realizes high-speed and accurate positioning of multiple sensing points.

Description

Technical Field

[0001] This invention relates to the field of distributed optical fiber sensing, specifically a high-speed chaotic Brillouin sensing device and method based on correlation-based multiple access positioning. Background Technology

[0002] Currently, distributed fiber optic sensing technology has become a new generation of sensors that countries are vying to develop due to its large measurement range, resistance to electromagnetic interference, and ability to detect multiple parameters. It has been widely used in the field of safety monitoring of large infrastructure, and has great social benefits and national strategic value.

[0003] Distributed fiber optic sensing technology based on Brillouin scattering is highly favored because it can achieve dual-parameter measurement of temperature and strain. Among them, the effective number of sensing points, i.e., the ratio of sensing distance to spatial resolution, is a key parameter for evaluating the performance of distributed fiber optic sensors. The spatial resolution of Brillouin optical time-domain technology is limited by the phonon lifetime, which is difficult to break through the meter level. Although researchers have proposed modulation techniques based on differential pulse pairs, pre-pump pulses and other light sources, as well as schemes such as deconvolution and rising edge demodulation, for example, Optics Letters, 2020, 45(15):4152-4155; Optics Letters, 2021, 46(14):3440-3443 to optimize the spatial resolution and make it reach the sub-meter level, it is still difficult to meet the requirements of millimeter or even sub-millimeter level spatial resolution in fields such as transportation infrastructure. The highest number of effective sensing points is only one million [Optics Letters, 2017, 42(10):1903-1906]. Brillouin optical correlation domain (BIR) technology, based on narrowband correlation peak excitation of the Brillouin acoustic field, can overcome the limitation of phonon lifetime and achieve spatial resolution at the centimeter or even millimeter level. For example, *Light: Science & Applications*, 2016, 5(2): 123-130; *Journal of Lightwave Technology*, 2019, 37(15): 3706-3712, making it a research hotspot for long-distance precise positioning. To increase the number of effective sensing points, researchers have proposed techniques such as time-domain gating, dual-modulation schemes, differential measurement, and first-order Raman amplification. For example, *Journal of Lightwave Technology*, 2023, 41(1): 341-346, achieving an effective sensing point count of over 2 million. However, the increase in the number of effective sensing points inevitably limits the system's measurement speed, making real-time monitoring a challenge.

[0004] Furthermore, Chinese invention patent ZL202010455193.5 proposes a multi-point parallel high-speed chaotic Brillouin dynamic strain monitoring device and method. This method simultaneously measures multiple correlation peaks in an optical fiber, determines the sensing position through pulse flight time, and ultimately achieves multi-point parallel monitoring. However, this method requires the use of an expensive pulse modulator to modulate continuous light into pulsed light. To avoid nonlinear effects, the power of the pulsed light cannot be too high, and there is a certain loss during transmission in the optical fiber. With increasing sensing distance, the energy loss of the pulsed light becomes severe, and the intensity noise of the chaotic light itself further leads to an extremely weak Brillouin gain signal at the end of the optical fiber, making it difficult to identify. Even if it can be identified, the weak gain signal results in an extremely low signal-to-noise ratio, preventing accurate positioning and further limiting the sensing distance and hindering the increase in the number of effective sensing points. Simultaneously, after modulating continuous light into pulsed light, only the high-level portion of the pulse interacts with the detection path. To increase the intensity of the interaction between the two beams, the pulse width cannot be too small, resulting in only one correlation peak within the pulse width range. Therefore, the remaining positions within this range and the positions corresponding to the low level of the pulse still need to be measured in a distributed manner by adjusting the optical delay line, and the scanning speed remains limited.

[0005] Therefore, there is a need to invent a high-speed demodulation technology for Brillouin distributed fiber optic sensing and monitoring with a massive number of sensor points to meet the requirements of real-time monitoring. Summary of the Invention

[0006] To address the challenges of slow measurement speed in existing Brillouin optical correlation domain analysis systems, which hinders real-time monitoring and practical application, this invention provides a high-speed chaotic Brillouin sensing device and method based on correlation-based multiple access positioning. This aims to meet the current application requirements for rapid real-time monitoring of massive numbers of distributed fiber optic sensing points.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a high-speed chaotic Brillouin sensing device based on correlation-based multiple access positioning, comprising: a highly correlated time-domain self-synchronizing chaotic laser source, wherein the highly correlated time-domain self-synchronizing chaotic laser source is used to output a strong periodic broadband chaotic laser, the strong periodic broadband chaotic laser is split into two beams by a first beam splitter, one beam is used as a probe beam and is sequentially down-shifted by a single-sideband modulator, and then amplified by a first erbium-doped fiber amplifier before being incident on one end of a sensing fiber; the other beam is sequentially passed through an optical delay line and a second erbium-doped fiber amplifier, and then split into a pump beam and a reference beam by a second beam splitter, the pump beam enters from the other end of the sensing fiber after passing through an optical circulator and meets the probe beam at different positions in the sensing fiber, and undergoes stimulated Brillouin amplification; the signal in the sensing fiber is output by the optical circulator, Stokes light is filtered out by a tunable optical filter and detected by a first photodetector, the reference light is detected by a second photodetector, and the two detection signals are simultaneously acquired by a data acquisition unit and sent to a computer for data processing.

[0008] The single-sideband modulator is used to modulate the probe light with a single-sideband, so that the frequency difference between it and the pump light is a Brillouin frequency shift; the optical delay line is used to adjust the optical path of the pump light so that the probe light and the pump light meet at different positions in the sensing fiber.

[0009] Preferably, the strong-period broadband chaotic laser is a strong-period broadband chaotic laser with a correlation coefficient greater than 0.9.

[0010] Preferably, the high-speed chaotic Brillouin sensing device based on correlation-based multiple access positioning further includes an optical polarizer and an optical isolator, wherein the optical polarizer and the optical isolator are disposed between one end of the first erbium-doped fiber amplifier and the sensing fiber; the optical polarizer is used to reduce the polarization sensitivity of the probe light, and the optical isolator is used to isolate stray light output from one end of the sensing fiber.

[0011] Preferably, the first and second beam splitters are 1×2 fiber couplers. The output of the highly correlated time-domain self-synchronizing chaotic laser source is connected to the input of the first beam splitter via a single-mode fiber jumper. The first output of the first beam splitter is connected to the input of a single-sideband modulator via a single-mode fiber jumper. The output of the single-sideband modulator is connected to the input of a first erbium-doped fiber amplifier via a single-mode fiber jumper. The output of the first erbium-doped fiber amplifier is connected to the input of an optical polarizer via a single-mode fiber jumper. The output of the optical polarizer is connected to the input of an optical isolator via a single-mode fiber jumper. The output of the optical isolator is connected to one end of a sensing fiber.

[0012] The second output of the first beam splitter is connected to the input of the optical delay line via a single-mode fiber optic patch cord; the output of the optical delay line is connected to the input of the second erbium-doped fiber amplifier via a single-mode fiber optic patch cord; the output of the second erbium-doped fiber amplifier is connected to the input of the second beam splitter via a single-mode fiber optic patch cord; the first output of the second beam splitter is connected to the first port of the optical circulator via a single-mode fiber optic patch cord; the second port of the optical circulator is connected to the other end of the sensing fiber, and the third port is connected to the input of the tunable optical filter via a single-mode fiber optic patch cord; the output of the tunable optical filter is connected to the input of the photodetector via a single-mode fiber optic patch cord, and the second output of the second beam splitter is connected to the input of the photodetector via a single-mode fiber optic patch cord.

[0013] Preferably, the high-speed chaotic Brillouin sensor based on correlation-based multiple access positioning further includes a broadband microwave signal source, which is used to drive the single-sideband modulator and is connected to the data acquisition unit.

[0014] Preferably, the highly correlated time-domain self-synchronizing chaotic laser source is used to output a strong periodic broadband chaotic laser with a -3dB spectral linewidth greater than 5 GHz and a -3dB power spectral bandwidth greater than 10 GHz.

[0015] Preferably, the sensing fiber is a G652 single-mode fiber or a G655 single-mode fiber.

[0016] Preferably, the specific method for the computer to perform data processing is as follows: cross-correlation operation is performed between the sensing signal detected by the first photodetector and the reference signal detected by the second photodetector to obtain the time delay value corresponding to each correlation peak in the cross-correlation curve, and multiple access positioning and demodulation are achieved through each time delay value and each correlation peak value.

[0017] Furthermore, this invention also provides a high-speed chaotic Brillouin sensing method based on correlation-based multiple access localization, implemented using the aforementioned device, comprising the following steps:

[0018] S1. Stimulated Brillouin amplification occurs between the probe light and the pump light in the sensor fiber.

[0019] S2. Synchronously acquire the chaotic Stokes optical signal and reference signal output from the sensing fiber, and perform correlation processing on the acquired chaotic Stokes optical signal and reference path signal to demodulate and obtain Brillouin gain signals at multiple locations.

[0020] S3. Adjust the optical path of the pump light by delaying the delay line so that the probe light and pump light undergo stimulated Brillouin amplification at different positions of the sensing fiber. Repeat step S2 to achieve scanning of the sensing fiber along multiple correlation peaks, thereby obtaining event information along the entire sensing fiber.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This invention provides a high-speed chaotic Brillouin sensing device and method based on correlation-based multiple access positioning. It employs a strong-period broadband chaotic laser with high correlation time-domain self-synchronization characteristics as the light source, exciting multiple correlation peaks at highly correlated positions in an optical fiber. Utilizing the intensity-noise characteristics of the chaotic laser itself, the chaotic reference light and the probe light with Brillouin gain are correlated. The position of each sensing point is determined based on the correlated time delay information. Adjusting a high-precision delay line to allow the correlation peaks to sweep across the interval between adjacent correlation peaks enables high-speed distributed measurement, significantly improving the system's measurement speed. Furthermore, the autocorrelation curve of the strong-period chaotic laser has an extremely high peak-to-sidelobe ratio; the larger the oscillation amplitude of the chaotic signal, the higher the peak-to-sidelobe ratio, enabling high signal-to-noise ratio signal detection. Therefore, this invention can not only simultaneously identify multiple correlation peaks in an optical fiber but also accurately identify weak Brillouin gain signals in long-distance microscale event regions, achieving distributed sensing for long-distance high-speed measurement.

[0023] 2. This invention uses a strong-period broadband chaotic laser as the light source, which has high correlation time-domain self-synchronization characteristics. Multiple correlation peaks are generated in the optical fiber, and the interval between these peaks is determined by the light source period. Multiple scans are performed by moving the positions of the correlation peaks to achieve fully distributed measurement. The number of scans is determined by the interval between the correlation peaks and is independent of the optical fiber length. Therefore, this invention can meet the application requirements of long-distance, high-speed, real-time monitoring.

[0024] 3. Compared to Brillouin optical correlation domain analysis techniques based on sinusoidal modulation combined with time-domain data processing, in this invention, the interval of the correlation peaks is determined by the period of the light source. The movement of the correlation peaks is achieved by adjusting a high-precision delay line, and the offset of the correlation peak position remains constant, enabling linear, uniform, and fully covered distributed measurement. Simultaneously, the spatial resolution of the system is determined solely by the light source linewidth. No operation is applied to the light source during the entire measurement process, and the light source linewidth remains constant. Therefore, the spatial resolution of the system is a constant value, enabling high-speed and accurate positioning of multiple sensing points.

[0025] 4. Compared to the multi-point parallel high-speed chaotic Brillouin dynamic strain monitoring device and method (Chinese Invention Patent ZL202010455193.5), this invention does not require additional modulation of optical pulses for positioning. Instead, it fully utilizes the intensity-noise characteristics of the chaotic laser itself, and performs multi-point positioning based on time delay information after correlation calculation. Furthermore, the greater the intensity fluctuation, the higher the signal-to-noise ratio of the signal obtained after correlation processing. Therefore, by cross-correlating the strong-period broadband chaotic laser with the probe light that obtains Brillouin gain, the weak gain at the end of long-distance optical fibers can be accurately identified, improving the system's signal-to-noise ratio. Meanwhile, in the multi-point parallel high-speed chaotic Brillouin dynamic strain monitoring device and method, continuous light is modulated into pulsed light, inevitably reducing the correlation between the pulsed pump light and the continuous probe light, resulting in a weakened stimulated Brillouin gain. This invention, however, does not use a pulsed light modulator, ensuring strong correlation between the two optical signals, resulting in a larger excited acoustic field intensity, a stronger gain signal, improved system signal-to-noise ratio, extended sensing distance, and further increased the number of effective sensing points.

[0026] 5. Compared to the Brillouin distributed fiber optic sensing device and method for location based on chaotic correlation (Chinese Invention Patent ZL201610305960.8), the probe light obtaining Brillouin gain is filtered by two filters to extract the Rayleigh scattering light and the Stokes frequency sidebands of the probe light. The position signal of fiber temperature or strain is determined by calculating the correlation function between the pump light's backscattered Rayleigh signal and the reference signal. Simultaneously, the Brillouin gain spectrum of the fiber is determined by calculating the relationship between the power of the probe light sideband signal and the modulation frequency, thereby obtaining the temperature or strain value at any location in the fiber. This invention eliminates the need for two separate filters; the probe light obtaining Brillouin gain is directly cross-correlated with the chaotic reference signal. The positions of multiple correlation peaks can be determined based on the different delays at different locations. If there is a change in temperature or stress at a certain correlation peak, the magnitude of the correlation peak will fluctuate compared to correlation peaks in other non-event regions. Furthermore, by extracting the frequency information of the Brillouin gain spectrum, accurate temperature or strain values ​​can be obtained, saving costs, simplifying the data acquisition process, and improving measurement speed.

[0027] In summary, this invention uses chaotic correlation to replace pulse-flight method to achieve synchronous positioning of any number of sensing points in an optical fiber. It makes full use of the intensity-noise characteristics of chaotic lasers and performs multi-point positioning based on time delay information after correlation calculation. The greater the intensity fluctuation, the higher the signal-to-noise ratio of the signal obtained after correlation processing. It can accurately identify the weak Brillouin gain signal at the end of the optical fiber, improve the system signal-to-noise ratio, further extend the sensing distance, and achieve high-speed and accurate positioning of multiple sensing points. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a high-speed chaotic Brillouin sensor based on correlation-based multiple access localization provided in Embodiment 1 of the present invention;

[0029] Figure 2 The time series diagram (a) and its correlation curve (b) of the strong periodic chaotic laser output from the highly correlated time-domain self-synchronized chaotic laser source in Embodiment 1 of the present invention are shown.

[0030] Figure 3 The signal-to-noise ratios of strong periodic chaotic laser signals with different peak-to-peak oscillation amplitudes after correlation processing are shown in (a), where (a) is the time series diagram of a strong periodic chaotic laser signal with a peak-to-peak value of 12mV, (b) is the correlation curve corresponding to (a), (c) is the time series diagram of a strong periodic chaotic laser signal with a peak-to-peak value of 60mV, and (d) is the correlation curve corresponding to (c).

[0031] Figure 4 This is a schematic diagram of the structure of a high-speed chaotic Brillouin sensor based on correlation method multiple access positioning provided in Embodiment 2 of the present invention;

[0032] In the figure: 1-Highly correlated time-domain self-synchronizing chaotic laser source, 2-First beam splitter, 3-Single-sideband modulator, 4-First erbium-doped fiber amplifier, 5-Optical polarizer, 6-Optical isolator, 7-Broadband microwave signal source, 8-Optical delay line, 9-Second erbium-doped fiber amplifier, 10-Second beam splitter, 11-Optical circulator, 12-Sensing fiber, 13-Tunable optical filter, 14-First photodetector, 15-Second photodetector, 16-Data acquisition unit, 17-Computer. Detailed Implementation

[0033] 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.

[0034] Example 1

[0035] like Figure 1 As shown, Embodiment 1 of the present invention provides a high-speed chaotic Brillouin sensing device based on correlation-based multiple access positioning, comprising: a highly correlated temporal self-synchronizing chaotic laser source 1, the highly correlated temporal self-synchronizing chaotic laser source 1 being used to output a strong periodic broadband chaotic laser, the strong periodic broadband chaotic laser being split into two beams by a first beam splitter 2, one beam serving as a probe beam being sequentially down-shifted by a single-sideband modulator 3, and then amplified by a first erbium-doped fiber amplifier 4 before being incident on one end of a sensing fiber 12; the other beam being sequentially passed through an optical delay line 8 and a second erbium-doped fiber amplifier 9, and then split into a pump beam and a reference beam by a second beam splitter 10, the pump beam being passed through an optical circulator 1. The probe light enters from the other end of the sensing fiber 12 and encounters the probe light at different positions within the sensing fiber, resulting in stimulated Brillouin amplification. The signal in the sensing fiber 12 is output by the optical circulator 11, filtered by the tunable optical filter 13 to extract Stokes light, which is then detected by the first photodetector 14. The reference light is detected by the second photodetector 15. Both detection signals are simultaneously acquired by the data acquisition unit 16 and then sent to the computer 17 for data processing. The single-sideband modulator 3 is used to modulate the probe light so that its frequency difference with the pump light is equal to the Brillouin frequency shift. The optical delay line 8 is used to adjust the optical path of the pump light. The optical delay line 8 is a high-precision optical delay line. In this embodiment, the optical delay line has a delay range of 169 mm, a delay accuracy of 0.3 μm, and a delay step of 0.001 mm.

[0036] Furthermore, the strong periodic broadband chaotic laser is a broadband chaotic laser with a correlation coefficient greater than 0.9 and a time-series signal consisting of periodic rectangular pulses. Specifically, when the output chaotic laser is a periodic light source, exhibiting periodic rectangular light pulses in time sequence, and its cross-correlation coefficient is greater than 0.9, the laser source can be considered a highly correlated time-domain self-synchronizing chaotic laser source.

[0037] Furthermore, the highly correlated time-domain self-synchronized chaotic laser source 1 is used to output a strong periodic broadband chaotic laser with a -3dB spectral linewidth greater than 5GHz and a -3dB power spectral bandwidth greater than 10GHz, a duty cycle greater than 85%, a cross-correlation coefficient greater than 0.9, and a peak-to-peak value greater than 100mV; the optical circulator 11 is a high peak power optical circulator compatible with pulsed light transmission, the first photodetector 14 and the second photodetector 15 are low-noise, high-sensitivity detectors, and the sensing fiber 12 uses G652 single-mode fiber or G655 single-mode fiber. In addition, in this embodiment, the timing signal of the chaotic laser output by the highly correlated time-domain self-synchronized chaotic laser source 1 is a periodic rectangular pulse, and the chaotic signal in the high-level portion of the pulse exhibits random oscillation, with its autocorrelation curve showing strong periodicity, such as... Figure 2 As shown.

[0038] Specifically, in this embodiment, the strong periodic broadband chaotic laser output by the highly correlated time-domain self-synchronizing chaotic laser source 1 can be generated by modulation of an electro-chaotic signal, or the intensity of the feedback light can be controlled by an electro-absorption modulator to achieve switching between chaotic laser and steady-state laser, thereby outputting multiple segments of highly correlated chaotic laser oscillations with a cross-correlation coefficient greater than 0.9.

[0039] Furthermore, the first beam splitter 2 and the second beam splitter 11 are 1×2 fiber couplers. The output of the highly correlated time-domain self-synchronizing chaotic laser source 1 is connected to the input of the first beam splitter 2 via a single-mode fiber jumper. The first output of the first beam splitter 2 is connected to the input of the single-sideband modulator 3 via a single-mode fiber jumper. The output of the single-sideband modulator 3 is connected to the input of the first erbium-doped fiber amplifier 4 via a single-mode fiber jumper. The output of the first erbium-doped fiber amplifier 4 is connected to the input of the optical polarizer 5 via a single-mode fiber jumper. The output of the optical polarizer 5 is connected to the input of the optical isolator 6 via a single-mode fiber jumper. The output of the optical isolator 6 is connected to one end of the sensing fiber 12.

[0040] The second output of the first beam splitter 2 is connected to the input of the optical delay line 8 via a single-mode fiber optic patch cord; the output of the optical delay line 8 is connected to the input of the second erbium-doped fiber amplifier 9 via a single-mode fiber optic patch cord; the output of the second erbium-doped fiber amplifier 9 is connected to the input of the second beam splitter 11 via a single-mode fiber optic patch cord; the first output of the second beam splitter 11 is connected to the first port of the optical circulator 11 via a single-mode fiber optic patch cord; the second port of the optical circulator 11 is connected to the other end of the sensing fiber 12, and the third port is connected to the input of the tunable optical filter 13 via a single-mode fiber optic patch cord; the output of the tunable optical filter 13 is connected to the input of the photodetector 14 via a single-mode fiber optic patch cord, and the second output of the second beam splitter 11 is connected to the input of the photodetector 15 via a single-mode fiber optic patch cord.

[0041] Specifically, in this embodiment, the specific method for data processing by computer 17 is as follows:

[0042] The sensing signal detected by the first photodetector 14 and the reference signal detected by the second photodetector 15 are cross-correlated to obtain the time delay value corresponding to each correlation peak in the cross-correlation curve. Multiple access positioning and demodulation are achieved by using each time delay value and each correlation peak value.

[0043] Furthermore, the high-speed chaotic Brillouin sensing device based on correlation-based multiple access positioning in this embodiment is characterized by further including a broadband microwave signal source 7, which is used to drive the single-sideband modulator 3, and the broadband microwave signal source 7 is connected to the data acquisition unit 16.

[0044] The working principle of this invention is as follows.

[0045] 1. A highly correlated time-domain self-synchronizing chaotic laser source 1 outputs a broadband chaotic laser with a center wavelength of 1550 nm, a strong periodicity in its time-series signal with a correlation coefficient greater than 0.9, a center frequency of ν0, a -3 dB spectral linewidth greater than 5 GHz, and a -3 dB power spectral bandwidth greater than 10 GHz. The light output from the source is split into two paths by a first beam splitter 2 formed by a 1×2 fiber coupler with a 10:90 ratio.

[0046] 2. One of the paths (90%) is used as the probe light and modulated by the single-sideband modulator 3 to generate a probe light with a lower frequency, ν0-ν. B , where ν BThe Brillouin shift is approximately 11 GHz for ordinary single-mode fiber. The single-sideband modulator 3 is driven by a broadband microwave signal source 7, which can output a sinusoidal signal with a frequency range of 9 kHz to 13 GHz and an amplitude range of -20 to 19 dBm. The modulated optical signal is amplified using a first erbium-doped fiber amplifier 4, and the amplified optical signal is incident on the sensing fiber 12, which is either G652 or G655 single-mode fiber.

[0047] 3. The other path (10%) is amplified to an appropriate level by the second erbium-doped fiber amplifier 9 after passing through the high-precision delay line 8 to excite stimulated Brillouin scattering. Then, 99% of the output from the second beam splitter 10, formed by a 1×2 fiber coupler with a ratio of 1:99, is used as pump light. The pump light is incident on the sensing fiber 12 via the optical circulator 11 and encounters the probe light in the sensing fiber 12, where stimulated Brillouin scattering occurs. The 1% output from the second beam splitter 10 is used as reference light.

[0048] 4. The chaotic probe light and pump light traveling in opposite directions meet at a certain position in the sensing fiber, generating a correlation peak. Due to the strong periodicity of the chaotic source signal, multiple correlation peaks can be excited in the fiber, and the stimulated Brillouin amplification is confined to each independent correlation peak. An XTM-50 wavelength-bandwidth adjustable filter 13 is used to filter the probe light. The filtered Stokes light signal is converted into an electrical signal by the first photodetector 14 and input to the data acquisition unit 16 for real-time signal acquisition via a high-frequency coaxial cable. The data acquisition unit 16 acquires the signal power after stimulated Brillouin amplification, in which the frequency difference between the probe light and the pump light is fixed at the Brillouin frequency shift by a broadband microwave source 7. The other light output from the second beam splitter 10 is used as a reference signal, converted into an electrical signal by the photodetector 15, and input to the data acquisition unit 16 for real-time signal acquisition via a high-frequency coaxial cable. The light and the filtered probe light signal are cross-correlated and processed by the data processor 17 to accurately extract event information along the fiber.

[0049] 5. By performing correlation processing with the chaotic reference path signal, the positions of different correlation peaks are determined according to different time delays, thereby achieving synchronous positioning of multiple correlation peaks.

[0050] Let the reference signal x1(t) be expressed as x1(t) = s(t), then the filtered probe signal x2(t) can be expressed as x2(t) = s(tD), where D is the time delay of the two signals. The cross-correlation function between the reference signal x1(t) and the probe signal x2(t) is:

[0051] R x1 x2 =E[s(t)s(t-D+τ)]=Rss(τ-D); (1)

[0052] Among them, R x1 x2 Let E represent the cross-correlation function of the two signals. When the cross-correlation function of the reference signal x1(t) and the probe signal x2(t) reaches its maximum value, Rss(τ-D) also reaches its maximum value. Since Rss(τ-D) ≤ Rss(0), the τ at which the cross-correlation function reaches its maximum value is the time delay D. Therefore, by performing a cross-correlation operation on the two signals and determining the value of the time delay D corresponding to the correlation peak of the cross-correlation function, the position of the correlation peak can be located.

[0053] In this embodiment, since a strong periodic broadband chaotic laser with periodic rectangular pulses as the timing signal is used, the detection path signal contains multiple correlation peaks. Therefore, after correlation processing, there will be multiple time delay peaks. The distance between each time delay peak can be used to determine the spacing between each correlation peak, thereby achieving synchronous positioning of multiple correlation peaks. Then, the information sensing of multiple positioning addresses can be determined simultaneously by the peak value of each correlation peak.

[0054] At the same time, such as Figure 3 As shown, the larger the peak-to-peak oscillation of the chaotic laser time series, the higher the peak-to-sidelobe noise ratio after cross-correlation processing, and the higher the signal-to-noise ratio of the extracted signal. Therefore, this invention can also suppress noise signals at the fiber optic end, extract the Brillouin gain signal of the microscale event region at the fiber optic end, accurately identify event points at the fiber optic end, and improve the monitoring distance of distributed fiber optic sensing. Furthermore, in this invention, the number of scans of the correlation peaks is determined by the interval of the correlation peaks, not the fiber length. The number of scans does not increase with the increase of the sensing fiber length, thus the system can achieve real-time monitoring of long-distance, high-speed sensing.

[0055] Example 2

[0056] like Figure 4 As shown, this embodiment of the invention provides a high-speed chaotic Brillouin sensing device based on correlation-based multiple access positioning. Similar to Embodiment 1, it includes: a highly correlated time-domain self-synchronizing chaotic laser source 1, a first beam splitter 2, a single-sideband modulator 3, a first erbium-doped fiber amplifier 4, an optical delay line 8, a second erbium-doped fiber amplifier 9, a second beam splitter 10, an optical circulator 11, a sensing fiber 12, a tunable optical filter 13, a first photodetector 14, a second photodetector 15, a data acquisition unit 16, and a computer 17.

[0057] Unlike Embodiment 1, this embodiment also includes an optical polarizer 5 and an optical isolator 6, which are sequentially disposed between one end of the first erbium-doped fiber amplifier 4 and the sensing fiber 12. The optical polarizer 5 is used to reduce the polarization sensitivity of the probe light, and the optical isolator 6 is used to isolate stray light output from one end of the sensing fiber 12.

[0058] Example 3

[0059] Embodiment 3 of the present invention provides a high-speed chaotic Brillouin sensing method based on correlation-based multiple access localization, implemented using the device described in Embodiment 1 or 2, and includes the following steps:

[0060] S1 causes stimulated Brillouin amplification of the probe light and pump light in the sensor fiber.

[0061] In the aforementioned sensing device, the first beam splitter 2 splits the strong periodic broadband chaotic laser output from the highly correlated time-domain self-synchronizing chaotic laser source 1 into two paths, one of which serves as the probe light. The probe light is down-shifted by the single-sideband modulator 3, making the optical frequency difference between the probe light and the pump light a Brillouin frequency shift. The other path is split into two beams after passing through the optical delay line 8 and the second erbium-doped fiber amplifier 9. One beam serves as the pump light, and the pump pulse light and the frequency-shifted probe light are input into the sensing fiber 12 from both ends, where stimulated Brillouin amplification occurs. The other beam serves as the reference light.

[0062] S2. Synchronously acquire the chaotic Stokes optical signal and reference signal output from the sensing fiber, and perform correlation processing on the acquired chaotic Stokes optical signal and reference path signal to demodulate and obtain Brillouin gain signals at multiple locations.

[0063] S3. Adjust the optical path of the pump light by using an optical delay line so that the probe light and pump light undergo stimulated Brillouin amplification at different positions in the sensing fiber. Repeat step S2 to achieve scanning of the sensing fiber along multiple correlation peaks, thereby obtaining event information along the entire sensing fiber.

[0064] In this embodiment, the high peak-to-side-lobe ratio of the autocorrelation curve is achieved by fully utilizing the noise-like characteristics of chaotic lasers. The collected data is processed by correlation operations, and Brillouin gain information at multiple locations is extracted simultaneously. The high signal-to-noise ratio allows for further improvement in sensing distance.

[0065] In summary, this invention utilizes a highly correlated time-domain self-synchronizing chaotic laser to simultaneously excite multiple correlation peaks in an optical fiber. Correlation operations are used to locate these peaks, and fully distributed scanning measurement of the optical fiber is achieved by adjusting the length of a high-precision optical delay line. Simultaneous measurement of multiple correlation peaks significantly improves the system's measurement speed, and the adjustment range of the high-precision optical delay line is limited to the lengths of adjacent correlation peaks, independent of the fiber length, further increasing the system's measurement distance. Cross-correlation processing of the measured probe light signal and the reference path signal further improves the signal-to-noise ratio of the resulting Brillouin gain signal, enabling precise identification of weak Brillouin gain signals in the microscale event region at the fiber end. Ultimately, this achieves high-speed chaotic Brillouin distributed optical fiber sensing measurement of massive amounts of sensor data.

[0066] 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 high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning, characterized in that, The application relates to a high-correlation time-domain self-synchronous chaotic laser source (1) for outputting strong periodic broadband chaotic laser, wherein the strong periodic broadband chaotic laser is divided into two beams by a first beam splitter (2), one beam is used as probe light and sequentially subjected to optical frequency downshifting by a single-sideband modulator (3), optical amplification by a first erbium-doped fiber amplifier (4) and then incident to one end of a sensing optical fiber (12); the other beam is sequentially subjected to optical delay by an optical delay line (8) and optical amplification by a second erbium-doped fiber amplifier (9), then divided into pump light and reference light by a second beam splitter (10), the pump light enters the other end of the sensing optical fiber (12) from the other end of the sensing optical fiber (12) after passing through an optical circulator (11) and meets the probe light at different positions in the sensing optical fiber to generate stimulated Brillouin amplification; the signal in the sensing optical fiber (12) is outputted by the optical circulator (11), stokes light is filtered out by an adjustable optical filter (13) and detected by a first photodetector (14), and the reference light is detected by a second photodetector (15), the two detection signals are simultaneously collected by a data acquisition unit (16) and sent to a computer (17) for data processing; The single-sideband modulator (3) is used for single-sideband modulation of the probe light, so that the frequency difference between the probe light and the pump light is the Brillouin frequency shift amount; the optical delay line (8) is used for adjusting the optical path of the pump light, so that the probe light and the pump light meet at different positions in the sensing optical fiber; The chaotic laser outputted by the high-correlation time-domain self-synchronous chaotic laser source (1) is a periodic light source, which is periodic rectangular light pulses in time sequence, and the cross-correlation coefficient is greater than 0.9; The first beam splitter (2) and the second beam splitter (10) are 1*2 optical fiber couplers, the output end of the high-correlation time-domain self-synchronous chaotic laser source (1) is connected with the input end of the first beam splitter (2) through a single-mode optical fiber jumper; the first output end of the first beam splitter (2) is connected with the input end of the single-sideband modulator (3) through a single-mode optical fiber jumper; the output end of the single-sideband modulator (3) is connected with the input end of the first erbium-doped fiber amplifier (4) through a single-mode optical fiber jumper; the output end of the first erbium-doped fiber amplifier (4) is connected with the input end of the optical polarization scrambler (5) through a single-mode optical fiber jumper; the output end of the optical polarization scrambler (5) is connected with the input end of the optical isolator (6) through a single-mode optical fiber jumper; the output end of the optical isolator (6) is connected with one end of the sensing optical fiber (12). ​ The second output end of the first optical splitter (2) is connected with the input end of the optical delay line (8) through a single-mode optical fiber jumper; the output end of the optical delay line (8) is connected with the input end of the second erbium-doped fiber amplifier (9) through a single-mode optical fiber jumper; the output end of the second erbium-doped fiber amplifier (9) is connected with the input end of the second optical splitter (10) through a single-mode optical fiber jumper; the first output end of the second optical splitter (10) is connected with the first port end of the optical circulator (11) through a single-mode optical fiber jumper; the second port of the optical circulator (11) is connected with the other end of the sensing optical fiber (12), and the third port is connected with the input end of the tunable optical filter (13) through a single-mode optical fiber jumper; the output end of the tunable optical filter (13) is connected with the input end of the first photodetector (14) through a single-mode optical fiber jumper, and the second output end of the second optical splitter (10) is connected with the input end of the second photodetector (15) through a single-mode optical fiber jumper.

2. A high-speed chaotic Brillouin sensing device based on correlation method multi-address positioning according to claim 1, characterized in that, Further comprising an optical depolarizer (5) and an optical isolator (6), which are arranged between the first erbium-doped fiber amplifier (4) and one end of the sensing optical fiber (12); the optical depolarizer (5) is used to reduce the polarization sensitivity of the probe light, and the optical isolator (6) is used to isolate stray light output from one end of the sensing optical fiber (12).

3. A high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning according to claim 1, characterized in that, Further comprising a broadband microwave signal source (7) for driving the single sideband modulator (3), which is connected with the data acquisition unit (16).

4. The high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning of claim 1, wherein, The high correlation time domain self-synchronous chaotic laser source (1) is used to output strong periodic broadband chaotic laser with a -3dB spectral line width greater than 5GHz and a -3dB power spectrum bandwidth greater than 10GHz.

5. The high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning of claim 1, wherein, The sensing optical fiber (12) adopts a G652 single-mode optical fiber or a G655 single-mode optical fiber.

6. A high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning according to claim 1, characterized in that, The specific method for the computer (17) to process data is as follows: The sensing signal detected by the first photodetector (14) and the reference signal detected by the second photodetector (15) are subjected to cross-correlation operation to obtain time delay values corresponding to each correlation peak in the cross-correlation curve, and multiple address positioning and demodulation are realized through each time delay value and each correlation peak value.

7. A high-speed chaotic Brillouin sensing method based on correlation method multi-address positioning, implemented by using the device of claim 1, characterized in that, The method comprises the following steps: S1, the probe light and the pump light are subjected to stimulated Brillouin amplification in the sensor optical fiber; S2, the chaotic Stokes light signal output from the sensing optical fiber and the reference signal are synchronously collected, and the collected chaotic Stokes light signal and the reference signal are subjected to correlation processing to demodulate a Brillouin gain signal at multiple positions; S3, the optical path of the pump light is adjusted through the optical delay line to make the probe light and the pump light subjected to stimulated Brillouin amplification at different positions of the sensing optical fiber, and step S2 is repeated to realize scanning of multiple correlation peak edges along the sensing optical fiber, so as to obtain event information along the sensing optical fiber.

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