Chaotic Brillouin Optical Frequency Domain-Correlation Domain Fusion Reflective Sensing Device and Method

Abstract

The present invention relates to the field of distributed optical fiber sensing, and discloses a chaotic Brillouin optical frequency domain - correlation domain fusion reflection sensing device and method. In the device, the phase - type chaotic laser output by a phase - type chaotic laser source is divided into two beams by a beam splitter. One beam serves as the signal light and is incident on a sensing optical fiber after passing through a modulator and an optical circulator in sequence. The generated chaotic backward Brillouin scattered light enters a combiner through the optical circulator. The other beam serves as the reference light and enters the combiner through a programmable optical delay generator to produce a beat - frequency effect with the chaotic backward Brillouin scattered light. The generated Brillouin beat - frequency signal is collected by a broadband photodetector. The signal output end of the broadband photodetector is connected to the first signal input end of a mixer. The second signal input end of the mixer is connected to a radio - frequency signal. The signal output end is connected to a vector network analyzer through a low - pass filter. The present invention can achieve high - precision positioning, high spatial resolution, and high - precision measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of distributed optical fiber sensing, and in particular to a chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing device and method. Background Art

[0002] Distributed fiber optic sensing technology can realize the spatiotemporal distribution perception of external physical, chemical, and biological parameters through characteristic parameters such as internal loss, polarization, and dispersion of optical fibers. Due to its high sensitivity, high resolution, and large capacity, it has been widely used in important fields such as life science monitoring, infrastructure structural health monitoring, marine geophysical exploration, and military border security.

[0003] One of the core challenges of distributed fiber optic sensing is simultaneously achieving accurate measurement of the measured parameter and precise spatial positioning. The specific technical requirement is a sensing method that combines high spatial resolution, high measurement accuracy, and high positioning accuracy. Currently, to achieve simultaneous monitoring of multiple parameters, Brillouin scattering sensors that are sensitive to both strain and temperature are rapidly developing. Based on the principle of scattering measurement, spontaneous Brillouin scattering schemes employ a single-ended reflection structure, suitable for long-distance linear projects and harsh environments. Stimulated Brillouin scattering schemes often employ a double-ended analytical structure, suitable for loop projects and susceptible to fiber breakage and loss. Based on the principle of spatial positioning, time-domain schemes utilize single-frequency optical pulses to achieve gain excitation and spatial positioning, resulting in a long sensing distance. However, this approach is inherently conflicting with spatial resolution. Correlation-domain schemes utilize broad-spectrum, low-coherence light to provide micron-level spatial resolution, extending the sensing distance to several kilometers. Optical frequency-domain schemes employ continuously frequency-modulated lasers for distributed positioning along the optical fiber, theoretically achieving a decoupling of distance and spatial resolution. Therefore, optical correlation domain reflectometry (BOCDR) and optical frequency domain reflectometry (BOFDR) sensing technologies based on spontaneous Brillouin scattering have great development potential in modern distributed fiber optic sensing networks.

[0004] However, the current high spatial resolution BOCDR and BOFDR face the following difficulties: (1) The monitoring and positioning of the sinusoidal frequency modulated BOCDR system is achieved by adjusting the sinusoidal signal frequency or random sequence code rate. Therefore, the scanning process is accompanied by the deterioration of spatial resolution and positioning accuracy, resulting in monitoring blind spots. (2) The frequency-continuously modulated narrowband laser BOFDR obtains the scattering information distribution in the optical fiber through the spatial point spread function. As the sensing distance increases, the spatial point spread function will continue to deteriorate due to light source noise, external interference, etc., resulting in a sharp drop in measurement accuracy and positioning accuracy. In addition, both of the above devices will be affected by the weak spontaneous Brillouin scattering signal, resulting in a poor overall signal-to-noise ratio of the system, difficulty in increasing the sensing distance, and a more significant bottleneck effect of achieving both high resolution and high accuracy. (3) The spatial positioning of the chaotic laser BOCDR system relies on a mechanical scanning device, and an electrically controlled programmable optical delay line with a delay accuracy far less than the spatial resolution of the system is used to achieve all-fiber equal precision and blind spot-free sensing measurement. However, this method requires advance calibration and is difficult to put into practical use.

[0005] Therefore, it is necessary to invent a Brillouin distributed optical fiber sensing device and method with both high resolution and high precision to meet the requirements of accurate measurement of the measured parameters and precise positioning of the spatial position. Summary of the Invention

[0006] To address the problem that existing Brillouin distributed fiber optic sensing systems cannot achieve both high resolution and high precision, the present invention provides a chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing device and method, aiming to meet the current needs of accurate measurement of measured parameters and precise positioning of spatial positions in large-scale building structures and major infrastructure.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing device, comprising: a phase-type chaotic laser source, the phase-type chaotic laser output by the phase-type chaotic laser source is divided into two beams by a beam splitter, one beam is used as signal light and is incident on the sensing optical fiber after passing through a modulator and an optical circulator in sequence, and the chaotic backward Brillouin scattered light generated in the sensing optical fiber is output by the optical circulator and then enters the optical combiner; the other beam is used as reference light and enters the optical combiner through a programmable optical delay generator; the chaotic backward Brillouin scattered light and the reference light generate a beat effect in the optical combiner, and the generated Brillouin beat signal is collected by a broadband photodetector, the signal output end of the broadband photodetector is connected to the first signal input end of the mixer, the second signal input end of the mixer is connected to the radio frequency signal, and the signal output end is connected to the vector network analyzer through a low-pass filter;

[0008] Among them, the modulator is used to perform frequency scanning or frequency offset on the signal light; the mixer is used to down-convert the Brillouin beat signal output by the broadband photodetector; the low-pass filter is used to filter out incoherent noise, and the vector network analyzer is used to perform data acquisition and correlation demodulation to obtain sensing information.

[0009] Both the optical splitter and the optical combiner are 1×2 fiber couplers, and the modulator is an electro-optic modulator.

[0010] The specific method for the vector network analyzer to perform data acquisition and correlation demodulation to obtain sensing information is as follows:

[0011] When the signal light performs frequency sweeping, perform frequency-domain processing on the Brillouin beat signal, demodulate the Brillouin frequency shift distribution along the fiber, and realize event positioning along the fiber.

[0012] When the signal light is single-frequency, perform correlation-domain processing on the Brillouin beat signal, demodulate the Brillouin gain spectrum at a single point position on the fiber, and realize the measurement of sensing information in the event area.

[0013] The described chaotic Brillouin optical frequency-domain - correlation-domain fusion reflection sensing device further includes an optical polarization scrambler, a high-power erbium-doped fiber amplifier, and a low-noise erbium-doped fiber amplifier. The signal light is incident on the sensing fiber after passing through the electro-optic modulator, the optical polarization scrambler, the high-power erbium-doped fiber amplifier, and the optical circulator in sequence. The optical polarization scrambler is used to perturb the polarization of the signal light to reduce the polarization dependence of the high-power erbium-doped fiber amplifier, and the high-power erbium-doped fiber amplifier is used to amplify the signal light.

[0014] The reference light enters the optical combiner after passing through the low-noise erbium-doped fiber amplifier and the programmable optical delay generator in sequence.

[0015] The central wavelength of the phase-type chaotic laser is 1550 nm, the -3dB spectral linewidth is 6.7 - 10.5 GHz, and the spectral shape is a symmetric Gaussian distribution.

[0016] The described chaotic Brillouin optical frequency-domain - correlation-domain fusion reflection sensing device further includes an arbitrary waveform generator and a microwave signal source. The arbitrary waveform generator is used to drive the modulator, and the microwave signal source is used to input a radio frequency signal to the mixer.

[0017] In addition, the present invention also provides a chaotic Brillouin optical frequency-domain - correlation-domain fusion reflection sensing method, which is realized based on the described chaotic Brillouin optical frequency-domain - correlation-domain fusion reflection sensing device, and includes a frequency-sweeping sensing process and a single-frequency sensing process.

[0018] The sweep-frequency sensing process is as follows: Control the signal light to output a sweep frequency. Synchronously collect the Brillouin beat signal and the sweep signal of the signal light through a vector network analyzer, and perform frequency-domain processing on the Brillouin beat signal with the sweep signal to obtain the Brillouin frequency shift distribution curve along the sensing optical fiber.

[0019] The single-frequency sensing process is as follows: Control the signal light to output a single frequency. Perform correlation-domain processing on the collected Brillouin beat signal through a vector network analyzer, demodulate to obtain the Brillouin gain spectrum at a single point position of the sensing optical fiber, and combine it with the Brillouin frequency shift distribution curve to further obtain the sensing information and the corresponding position.

[0020] The described chaotic Brillouin optical frequency-domain / correlation-domain fusion reflection sensing method further includes the following steps:

[0021] Adjust the optical path of the reference light through a programmable optical delay generator, repeat the single-frequency sensing process, and then obtain the sensing information at the next position. Then repeat the adjustment of the optical path of the reference light and the single-frequency sensing process to achieve a fully distributed scan of the correlation peak along the sensing optical fiber, so as to obtain the sensing information along the sensing optical fiber.

[0022] During the sweep-frequency sensing process, control the signal light to output a sweep frequency through a modulator.

[0023] The present invention has the following beneficial effects compared with the prior art:

[0024] 1. The present invention proposes a chaotic Brillouin optical frequency-domain / correlation-domain fusion reflection sensing device and method, which uses a phase-type chaotic laser with low-power noise as the sensing signal, makes full use of the Gaussian broadband characteristic of the chaotic laser spectrum, generates a spontaneous Brillouin acoustic wave field with a millimeter-scale spatial scale at highly correlated positions in the optical fiber, performs coherent beat-frequency processing and frequency-domain correlation demodulation on the frequency-scanned chaotic backscattered light and the chaotic reference light, and realizes millimeter-scale high-precision positioning along the optical fiber according to the frequency scanning accuracy and range; at the same time, performs correlation-domain synchronous processing on the single-row chaotic backscattered light and the chaotic reference light to realize millimeter-scale spatial resolution temperature and strain measurement at specific positions of the optical fiber, and adjusts the high-precision programmable optical delay generator to scan the millimeter-scale correlation peak; the chaotic Brillouin optical frequency-domain / correlation-domain fusion reflection sensing method described in the present invention can ensure the positioning and measurement of correlation peaks with the same spatial scale, thereby realizing all-fiber high-precision positioning, high spatial resolution, and high-precision measurement.

[0025] 2. The present invention uses phase-type chaotic laser. The peak-to-peak value of the timing fluctuation is very small and approaches the relative intensity noise of a single-frequency laser. The phase maintains chaotic random characteristics, and the spectrum presents a symmetric Gaussian distribution. Both the spectrum shape and the spectral linewidth have obvious tunability, which can ensure that the spatial resolution of the system reaches the millimeter level. The output power of the phase-type chaotic laser is stable, and the spectral state is stably adjustable. Stable sideband modulation and scanning can be realized by using a sine signal. Based on this, high-precision frequency-domain and correlation-domain joint demodulation of the Brillouin frequency shift distribution curve and the Brillouin gain spectrum is completed, realizing distributed sensing with high-precision positioning, high spatial resolution, and high measurement accuracy. In addition, the phase-type chaotic laser eliminates the influence of the signal-to-noise ratio deterioration introduced by the intensity fluctuation of the chaotic laser, suppresses the coherent noise and beat frequency noise introduced by the intensity correlation of the chaotic laser, and is more conducive to realizing the high-precision positioning and high spatial resolution measurement described in the present invention.

[0026] 3. Compared with the chaotic Brillouin optical frequency domain / correlation domain analysis sensing device and method, the solution described in the present invention can realize single-ended fiber link monitoring, meet the application requirements of long-distance linear projects, and the system is not affected by fiber breakpoints and is more suitable for harsh working environments. Compared with the chaotic Brillouin optical correlation domain reflectometry sensing device and method, the present invention uses phase-type chaotic laser, and its advantages are as described in 2. At the same time, the present invention abandons optical delay line positioning and uses frequency-domain signal processing to achieve high-precision positioning along the fiber, without the need for prior calibration of the sensing position, greatly shortening the system positioning time and improving the system practicability.

[0027] 4. Compared with the Brillouin optical correlation domain reflectometry technology based on sine signal frequency modulation combined with time-domain data processing, in the chaotic Brillouin optical frequency domain-correlation domain fusion reflectometry sensing device and method described in the present invention, there is a unique Brillouin correlation peak with a spatial scale of millimeters in the measured optical fiber. The millimeter-level high-precision positioning of the fiber along the line is realized by using the optical fiber frequency-domain analysis method. The positioning accuracy always remains consistent with the spatial resolution and does not change with the sensing position. By adjusting the high-precision optical delay generator, the movement of the correlation peak can be realized, and the offset of the correlation peak is always a constant, enabling linear uniform and full-coverage distributed measurement. In addition, the chaotic laser used in the present invention is a broadband light source, which has a higher stimulated Brillouin scattering threshold in the optical fiber. The spontaneous Brillouin scattering intensity can be increased by appropriately increasing the input fiber power, and thus a longer sensing distance can be realized without additional pulse modulation. At the same time, the spatial resolution of the system described in the present invention is only determined by the coherence length of the light source, and the coherence length of the light source remains unchanged during the measurement process, enabling distance-independent high spatial resolution measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of the chaotic Brillouin optical frequency domain-correlation domain fusion reflectometry sensing device provided in Embodiment 1 of the present invention;

[0029] Figure 2 Schematic structural diagram of the chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing device provided in the second embodiment of the present invention;

[0030] In the figure: 1 - Phase-type chaotic laser source, 2 - Optical splitter, 3 - Modulator, 4 - Optical polarization scrambler, 5 - High-power erbium-doped fiber amplifier, 6 - Optical circulator, 7 - Sensing optical fiber, 8 - Arbitrary waveform generator, 9 - Low-noise erbium-doped fiber amplifier, 10 - Programmable optical delay generator, 11 - Optical combiner, 12 - Wideband photodetector, 13 - Mixer, 14 - Microwave signal source, 15 - Low-pass filter, 16 - Vector network analyzer. Specific implementation manners

[0031] 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. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Embodiment 1

[0033] As Figure 1 shown, Embodiment 1 of the present invention provides a chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing device, including: a phase-type chaotic laser source 1, an optical splitter 2, a modulator 3, an optical circulator 6, a sensing optical fiber 7, a programmable optical delay generator 10, an optical combiner 11, a wideband photodetector 12, a mixer 13, a low-pass filter 15, and a vector network analyzer 16; the phase-type chaotic laser output by the phase-type chaotic laser source 1 is split into two beams by the optical splitter 2, one beam serves as a signal light and is incident on the sensing optical fiber 7 after passing through the modulator 3 and the optical circulator 6 in sequence, and the chaotic backward Brillouin scattering light generated in the sensing optical fiber exits through the optical circulator 6 and enters the optical combiner 11; the other beam serves as a reference light and enters the optical combiner 11 through the programmable optical delay generator 10; the chaotic backward Brillouin scattering light and the reference light generate a beat frequency effect in the optical combiner 11, and the generated Brillouin beat frequency signal is collected by the wideband photodetector 12. The signal output end of the wideband photodetector 12 is connected to the first signal input end of the mixer 13. The second signal input end of the mixer 13 is connected to a radio frequency signal, and the signal output end is connected to the vector network analyzer 16 through the low-pass filter 15;

[0034] wherein, the modulator 3 is used to perform frequency scanning or frequency offset on the signal light; the mixer 13 is used to perform down-conversion processing on the Brillouin beat frequency signal output by the wideband photodetector 12; the low-pass filter 15 is used to filter out incoherent noise, and the vector network analyzer 16 is used to perform data acquisition and correlation demodulation to obtain sensing information.

[0035] Further, in this embodiment, it further includes an arbitrary waveform generator 8 and a microwave signal source 14. The arbitrary waveform generator 8 is used to drive the modulator 3, and the microwave signal source 14 is used to input a radio frequency signal to the mixer 13.

[0036] Specifically, in this embodiment, the central wavelength of the phase-type chaotic laser is 1550 nm, the -3 dB spectral linewidth is 6.7 - 10.5 GHz, and the spectral shape is a symmetric Gaussian distribution.

[0037] Both the optical splitter 2 and the optical combiner 11 are 1×2 fiber couplers with a splitting ratio of 50:50, and the modulator 3 is an electro-optic modulator.

[0038] The working principle of this embodiment is as follows.

[0039] 1. For the phase-type chaotic laser with a central wavelength of 1550 nm, a central frequency of v0, a -3 dB spectral linewidth of about 6.7 - 10.5 GHz, and a symmetric Gaussian spectral shape, its theoretical spatial resolution is on the order of millimeters; the peak-to-peak value of the timing signal fluctuation is very small, and the output optical power is stable. The phase-type chaotic laser is divided into two paths, one path serves as the signal light, and the other path serves as the reference light. After the signal light enters the sensing optical fiber 7, spontaneous stimulated Brillouin scattering occurs in the sensing optical fiber. The generated backward scattered light is output from the sensing optical fiber 7 through the optical circulator 6, and then beats with the reference light at the optical combiner 11. The Brillouin gain spectrum can be obtained.

[0040] 2. When the chaotic signal light entering the sensing optical fiber is a swept-frequency laser through the modulator 3, there is a frequency difference between the chaotic backward scattered light and the chaotic reference light in the optical fiber. By scanning the frequency difference between the two beams of light and collecting the intensity I of the beat signal between the backward scattered light and the reference light at each frequency beat , and based on the established baseband transfer function P(f, f b ), the frequency-domain demodulation of the Brillouin frequency shift along the optical fiber can be realized. The expressions for the beat signal intensity I beat and the baseband transfer function P(f, f b ) are as follows:

[0041]

[0042]

[0043] Among them, E0 is the optical electric field, f b is the beat frequency, which is near the Brillouin frequency shift of the optical fiber; t represents time, f represents the frequency domain of the beat signal, Δv represents the swept frequency, and δ represents the Dirac function. R represents the photoelectric efficiency of the photodetector.

[0044] Therefore, the present invention scans the frequency of the signal optical light, collects the power of the beat signal between the signal optical light and the reference optical light in real time, and uses the baseband transmission function for demodulation to achieve high-precision demodulation of the Brillouin frequency shift amount along the optical fiber, complete high-precision and rapid positioning of the event area, and the positioning accuracy Δz' = V / 2Δν. Wherein, V represents the group velocity of light in the optical fiber.

[0045] 3. When the chaotic signal optical light entering the sensing optical fiber is a single-frequency laser, the chaotic backward scattering light and the reference optical light undergo a coherent beat frequency effect due to the phase correlation characteristics, and the spontaneous Brillouin scattering gain information will be analyzed within the beat frequency correlation peak. The width of the correlation peak is determined by the original line width Δf of the chaotic laser, and the system spatial resolution The phase-type chaotic laser light source adopted by the present invention can improve the system spatial resolution to the millimeter level, that is, millimeter-level spatial resolution can be achieved.

[0046] In this embodiment, when the signal optical light is a single-frequency laser, according to the Brillouin frequency shift information corresponding to the measured Brillouin gain spectrum, the temperature and strain information of the event area are obtained; the beat signal obtained during frequency sweeping is demodulated by using the baseband transmission function, and then combined analysis is performed to obtain the Brillouin frequency shift distribution curve of each position along the sensing optical fiber, and the event occurrence position can be accurately determined, thereby realizing distributed high-spatial-resolution and high-precision measurement along the sensing optical fiber 7.

[0047] 4. The programmable optical delay generator 10 can be used to further adjust the optical path difference between the backward scattering light and the reference optical light, realize full-distributed scanning of the correlation peak along the optical fiber without omission and repetition, and ensure high-resolution measurement of the full scale of the event area.

[0048] Therefore, in this embodiment, the specific method for the vector network analyzer 16 to perform data acquisition and correlation demodulation to obtain sensing information is as follows:

[0049] When the signal optical light performs frequency sweeping, the Brillouin beat signal is processed in the frequency domain to demodulate the Brillouin frequency shift distribution along the optical fiber and realize event positioning along the optical fiber;

[0050] When the signal optical light is a single frequency, the Brillouin beat signal is processed in the correlation domain to demodulate the Brillouin gain spectrum at a single point position of the optical fiber and realize the measurement of sensing information in the event area.

[0051] Embodiment 2

[0052] Such as Figure 2As shown in the figure, Embodiment 2 of the present invention provides a chaotic Brillouin optical frequency domain - correlation domain fusion reflection sensing device. Different from Embodiment 1, it further includes an optical polarization scrambler 4, a high - power erbium - doped fiber amplifier 5, and a low - noise erbium - doped fiber amplifier 9. The signal light is incident on the sensing fiber 7 after passing through the electro - optic modulator 3, the optical polarization scrambler 4, the high - power erbium - doped fiber amplifier 5, and the optical circulator 6 in sequence. The reference light enters the optical combiner 11 after passing through the low - noise erbium - doped fiber amplifier 9 and the programmable optical delay generator 10 in sequence.

[0053] In this embodiment, the optical polarization scrambler 4 is used to perturb the polarization of the signal light to reduce the polarization dependence of the high - power erbium - doped fiber amplifier 5. The high - power erbium - doped fiber amplifier 5 is used to amplify the signal light; the low - noise erbium - doped fiber amplifier 9 is used to amplify the reference light.

[0054] Embodiment 3

[0055] Embodiment 3 of the present invention provides a chaotic Brillouin optical frequency domain - correlation domain fusion reflection sensing method, which is implemented based on the chaotic Brillouin optical frequency domain - correlation domain fusion reflection sensing device described in Embodiment 1 or 2, and includes a swept - frequency sensing process and a single - frequency sensing process;

[0056] The swept - frequency sensing process is as follows: control the signal light to output a swept - frequency signal, synchronously collect the Brillouin beat signal and the swept - frequency signal of the signal light through the vector network analyzer 16, and perform frequency - domain processing on the Brillouin beat signal through the swept - frequency signal to obtain the Brillouin frequency shift distribution curve along the sensing fiber 7;

[0057] The single - frequency sensing process is as follows: control the signal light to output a single - frequency signal, perform correlation - domain processing on the collected Brillouin beat signal through the vector network analyzer 16, demodulate to obtain the Brillouin gain spectrum at a single - point position of the optical fiber, and combine it with the Brillouin frequency shift distribution curve to further obtain the sensing information and the corresponding position.

[0058] Further, in this embodiment, the following steps are further included:

[0059] Adjust the optical path of the reference light through the programmable optical delay generator 10, repeat the single - frequency sensing process, and then obtain the sensing information at the next position. Then repeat the adjustment of the optical path of the reference light and the single - frequency sensing process to obtain the sensing information along the sensing fiber.

[0060] In this embodiment, the optical path of the reference light is adjusted through the programmable optical delay generator 10, and then the optical path difference between the reference light and the backward Brillouin scattered light is adjusted to realize the full - distributed scanning of the correlation peak along the sensing fiber 7. Then, through the single - frequency sensing process, the sensing information along the sensing fiber can be obtained. At this time, the position corresponding to the temperature and strain information obtained by single - frequency sensing can be obtained by converting the optical path adjusted by the programmable optical delay generator 10.

[0061] In addition, after adjusting the optical path of the reference light each time through the programmable optical delay generator 10, the swept-frequency sensing can be repeated to obtain the positioning information, and then the single-frequency sensing can be performed to obtain the corresponding temperature and strain information. By adjusting the optical path difference multiple times and repeating the single-frequency sensing process and the multi-frequency sensing process multiple times, the sensing information along the sensing optical fiber can be obtained.

[0062] Specifically, during the swept-frequency sensing process, the modulator 3 is used to control the signal light to output a swept frequency.

[0063] In this embodiment, the chaotic signal light is modulated by the sine signal output by the arbitrary waveform generator 8 through the modulator 3. By adjusting the working state of the arbitrary waveform generator 8, the signal light can be selected to output a single frequency or a frequency scan. The chaotic signal light undergoes self-induced Brillouin scattering in the sensing optical fiber 7, and the chaotic backward scattered light is output to the optical combiner through the optical circulator; the backward scattered light and the reference light undergo coherent beat frequency, and the Brillouin gain signal is collected by the broadband photodetector, down-converted by the mixer, and noise-reduced by the low-pass filter, and finally sampled and processed by the vector network analyzer. When the signal light outputs a swept frequency, the chaotic Brillouin beat frequency signal and the sine signal output by the arbitrary waveform generator 8 are synchronously collected and subjected to frequency domain processing to demodulate the Brillouin frequency shift distribution along the optical fiber. Then, according to the Brillouin frequency shift distribution curve, high-precision positioning at any position along the sensing optical fiber 7 can be achieved. When the signal light outputs a single frequency, the chaotic Brillouin beat frequency signal is subjected to correlation domain processing to demodulate the Brillouin gain spectrum at a single point position of the sensing optical fiber 7, realizing high spatial resolution and high-precision measurement in the event area; by adjusting the optical path of the reference light through the programmable optical delay generator, the position of the correlation domain Brillouin signal peak in the optical fiber to be measured is scanned, realizing high spatial resolution and high-precision measurement along the entire sensing optical fiber.

[0064] In summary, the present invention provides a chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing device and method, which uses a phase chaotic laser with a Gaussian-type broadband spectrum as the sensing signal, generates a Brillouin acoustic wave field with a millimeter-scale spatial scale at highly correlated positions in the sensing optical fiber, performs frequency domain correlation demodulation after coherent beat frequency of the swept-frequency chaotic backward scattered light and the chaotic reference light, and realizes millimeter-scale high-precision positioning along the optical fiber according to the frequency scanning accuracy and range; at the same time, the single-frequency chaotic backward scattered light and the chaotic reference light are subjected to correlation domain synchronous processing to realize millimeter-scale spatial resolution temperature and strain measurement at specific positions of the optical fiber. The present invention uses a phase-type chaotic laser with very small peak-to-peak values of temporal fluctuations, stable output power, and stable and adjustable spectral state, which can suppress the coherent noise introduced by the intensity correlation of the chaotic laser; the present invention can achieve high-precision positioning and high spatial resolution and high-precision measurement.

[0065] 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 foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A chaotic Brillouin optical frequency domain - correlation domain fusion reflection sensing device, characterized in that, Comprising: A phase-type chaotic laser source (1), the phase-type chaotic laser output by the phase-type chaotic laser source (1) is divided into two beams by a beam splitter (2), one beam is used as the signal light and sequentially passes through a modulator (3) and an optical circulator (6) and then enters a sensing optical fiber (7), the chaotic backward Brillouin scattering light generated in the sensing optical fiber passes through the optical circulator (6) and then enters a combiner (11); the other beam is used as the reference light and enters the combiner (11) through a programmable optical delay generator (10); the chaotic backward Brillouin scattering light and the reference light generate a beat frequency effect in the combiner (11), and the generated Brillouin beat frequency signal is collected by a broadband optoelectronic detector (12), the signal output end of the broadband optoelectronic detector (12) is connected to the first signal input end of a mixer (13), the second signal input end of the mixer (13) is connected to a radio frequency signal, and the signal output end is connected to a vector network analyzer (16) through a low-pass filter (15); Wherein, the modulator (3) is used for frequency scanning or frequency offset of the signal light; the mixer (13) is used for down-converting the Brillouin beat frequency signal output by the broadband optoelectronic detector (12); the low-pass filter (15) is used for filtering out incoherent noise, and the vector network analyzer (16) is used for data acquisition and correlation demodulation to obtain sensing information; The specific method for the vector network analyzer (16) to perform data acquisition and correlation demodulation to obtain sensing information is as follows: When the signal light performs frequency sweeping, the Brillouin beat frequency signal is processed in the frequency domain to demodulate the Brillouin frequency shift distribution along the optical fiber, and event positioning along the optical fiber is realized; When the signal light is single-frequency, the Brillouin beat frequency signal is processed in the correlation domain to demodulate the Brillouin gain spectrum at a single point position of the optical fiber, and sensing information measurement in the event area is realized.

2. The chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing device according to claim 1, characterized in that The beam splitter (2) and the combiner (11) are both 1×2 fiber couplers, and the modulator (3) is an electro-optic modulator.

3. A chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing device according to claim 1, characterized in that It further includes an optical polarization scrambler (4), a high-power erbium-doped fiber amplifier (5), and a low-noise erbium-doped fiber amplifier (9), and the signal light sequentially passes through the modulator (3), the optical polarization scrambler (4), the high-power erbium-doped fiber amplifier (5), and the optical circulator (6) and then enters the sensing optical fiber (7); the optical polarization scrambler (4) is used for disturbing the polarization of the signal light to reduce the polarization dependence of the high-power erbium-doped fiber amplifier (5), and the high-power erbium-doped fiber amplifier (5) is used for amplifying the signal light; The reference light sequentially passes through the low-noise erbium-doped fiber amplifier (9) and the programmable optical delay generator (10) and then enters the combiner (11).

4. A chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing device according to claim 1, characterized in that, The central wavelength of the phase-type chaotic laser is 1550 nm, the -3dB spectral linewidth is 6.7~10.5 GHz, and the spectral shape is a symmetric Gaussian distribution.

5. The chaotic Brillouin optical frequency domain - correlation domain fusion reflection sensing device according to claim 1, characterized in that It further includes an arbitrary waveform generator (8) and a microwave signal source (14), the arbitrary waveform generator (8) is used for driving the modulator (3), and the microwave signal source (14) is used for inputting a radio frequency signal to the mixer (13).

6. A chaotic Brillouin optical frequency domain - correlation domain fusion reflection sensing method, which is realized based on the chaotic Brillouin optical frequency domain - correlation domain fusion reflection sensing device according to any one of claims 1 to 5, and is characterized in that, Including a frequency-sweeping sensing process and a single-frequency sensing process; The sweep-frequency sensing process is as follows: control the signal light to output in a sweep-frequency manner, synchronously collect the Brillouin beat signal and the sweep-frequency signal of the signal light through a vector network analyzer (16), and perform frequency-domain processing on the Brillouin beat signal with the sweep-frequency signal to obtain the Brillouin frequency shift distribution curve along the sensing optical fiber (7); The single-frequency sensing process is as follows: control the signal light to output in a single-frequency manner, perform correlation-domain processing on the collected Brillouin beat signal through a vector network analyzer (16), demodulate to obtain the Brillouin gain spectrum at a single-point position of the sensing optical fiber (7), and combine with the Brillouin frequency shift distribution curve to further obtain the sensing information and the corresponding position.

7. A chaotic Brillouin optical frequency domain - correlation domain fusion reflection sensing method according to claim 6, characterized in that It further includes the following steps: Adjust the optical path of the reference light through a programmable optical delay generator (10), repeat the single-frequency sensing process, and then obtain the sensing information at the next position. Then repeat the adjustment of the optical path of the reference light and the single-frequency sensing process to realize the full distributed scanning of the correlation peak along the sensing optical fiber, so as to obtain the sensing information along the sensing optical fiber.

8. A chaotic Brillouin optical frequency domain-correlation domain fusion reflection sensing method according to claim 6, characterized in that In the sweep-frequency sensing process, control the signal light to output in a sweep-frequency manner through a modulator (3).

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