High-positioning-precision Brillouin sensing device and method based on chaotic frequency-domain correlation demodulation

Abstract

The present invention relates to the field of distributed optical fiber sensing, and specifically to a high-positioning-precision Brillouin sensing device and method using chaotic frequency-domain correlation demodulation. The laser output by a phase-type chaotic laser source is split into two beams. The first beam passes through a first single-sideband modulator, a first optical amplifier, and an optical polarization scrambler in sequence and is incident on one end of a sensing optical fiber as detection light. The second beam passes through a second single-sideband modulator, a second optical amplifier, and a second beam splitter and is split into two beams. One beam is incident on the other end of the sensing optical fiber as pump light, and the other beam is incident on a beam combiner as reference light. The detection light output from the other end of the sensing optical fiber is split into two beams, one of which is incident on the beam combiner and the other is incident on a second photodetector. The light output by the beam combiner is incident on the first photodetector. The present invention can achieve all-fiber high-precision positioning and high-spatial-resolution measurement.

Description

Technical Field

[0001] The present invention relates to the field of distributed optical fiber sensing, and in particular to a high-positioning-precision Brillouin sensing device and method using chaotic frequency-domain correlation demodulation. Background Art

[0002] Since the 21st century, the demand for accurate positioning and high-precision monitoring of micro-scale disaster intervals in large-scale building structures and major infrastructure has become increasingly urgent. Distributed fiber optic sensing technology based on stimulated Brillouin scattering has the advantages of long monitoring distance, high spatial resolution, and the ability to realize multi-parameter monitoring of temperature and strain. It has been widely used in important fields such as smart grids, oil and gas pipelines, transportation infrastructure, water conservancy projects, military border security, etc.

[0003] To meet the significant demand for high-precision monitoring in modern sensor networks, researchers at home and abroad have proposed a variety of innovative solutions. Among them, the spatial resolution of Brillouin optical time-domain technology is limited by the phonon lifetime and is difficult to break through the meter level. Researchers have proposed solutions such as differential pulse pairs, rising edge demodulation, and single pulse self-differentiation [Opt. Lett., 46(14): 3440-3443, 2021; Opt. Lett., 47(19): 5008-5011, 2022] to break through the spatial resolution to the decimeter level, but it is still difficult to meet the needs of disaster area monitoring at the millimeter or even submillimeter scale. Brillouin optical correlation domain technology uses sinusoidal frequency modulated laser, phase coded laser, chaotic laser, etc. as sensing light sources. Based on the narrow-band correlation peak to excite the Brillouin acoustic wave field, it can break through the limitation of phonon lifetime and achieve spatial resolution of centimeters or even millimeters [J.Lightwave Technol., 37(15): 3706-3712, 2019; Opt. Express, 27(15): 36197-36205, 2019], becoming a research hotspot for precise monitoring of micro-scale disaster intervals.

[0004] However, the positioning accuracy of current millimeter-level spatial resolution sensing systems faces the following challenges: (1) The monitoring and positioning of sinusoidal frequency modulation and phase coding systems is achieved by adjusting the sinusoidal signal frequency or random sequence bit rate. Therefore, the scanning process is accompanied by the deterioration of spatial resolution and positioning accuracy, especially in long-distance systems, where the spatial resolution deteriorates severely and even monitoring blind spots occur. (2) In the chaotic laser system, an electrically controlled programmable optical delay line with a delay accuracy far less than the spatial resolution of the system is used to complete the positioning along the optical fiber, which can achieve full-fiber equal precision and blind-spot-free sensing measurement. However, this method requires advance calibration, distributed positioning is very time-consuming, and difficult to put into practical use; intensity correlation [ZL201610305960.8], multi-point parallel [ZL202010455193.5], time domain difference [ZL202010454169.X], multiple access correlation [CN202310671501.1] and other schemes have been proposed one after another. However, the high-peak intensity chaos, multi-order pulse modulation, and high-bandwidth time domain difference used in the above schemes result in poor system signal-to-noise ratio, making it difficult to achieve both millimeter-level spatial resolution and high-precision distributed positioning.

[0005] Therefore, it is necessary to invent a Brillouin distributed fiber optic sensing monitoring technology that combines high spatial resolution and high-precision distributed positioning to meet the needs of precise monitoring of micro-scale disaster areas in large-scale infrastructure settings. Summary of the Invention

[0006] In order to solve the problem of high-precision positioning of existing Brillouin distributed optical fiber sensing systems, the present invention provides a high-precision Brillouin sensing device and method based on chaotic frequency domain correlation demodulation, aiming to meet the current application needs of precise positioning and high-precision monitoring of micro-scale disaster intervals 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 high positioning accuracy Brillouin sensing device with chaotic frequency domain correlation demodulation, comprising: a phase-type chaotic laser source, the phase-type chaotic laser output by the phase-type chaotic laser source is divided into a first light beam and a second light beam by a first beam splitter, the first light beam is sequentially passed through a first single-sideband modulator, a first optical amplifier, and an optical polarization scrambler and then incident on one end of a sensing optical fiber as a detection light; the second light beam is divided into two beams after passing through a second single-sideband modulator, a second optical amplifier, and a second beam splitter, one beam is incident on the other end of the sensing optical fiber after passing through an optical circulator as pump light, and the other beam is incident on the first input end of a beam combiner as reference light; the detection light is output by the optical circulator at the other end of the sensing optical fiber, and then passed through a tunable optical filter and a third beam splitter and divided into two beams, one beam of light is incident on the second input end of the beam combiner, and the other beam of light is incident on a second photodetector to obtain a Brillouin gain and / or loss signal; the light output from the output end of the beam combiner is incident on the first photodetector to obtain a Brillouin beat frequency signal;

[0008] The first single sideband modulator is used to perform single sideband modulation on the first light beam, and the second single sideband modulator is used to perform single sideband chirp modulation on the second light beam;

[0009] The digital real-time oscilloscope is used to collect the Brillouin gain and / or loss signals and the Brillouin beat frequency signals output by the first photodetector and the second photodetector, and perform related demodulation processing to obtain sensing information along the sensing optical fiber.

[0010] The high-positioning-precision Brillouin sensing device with chaotic frequency-domain correlation demodulation also includes a microwave signal source, which is used to drive the first single-sideband modulator to perform spectral sideband modulation on the first light beam, and to drive the second single-sideband modulator to perform spectral sideband modulation and scanning on the second light beam, and is also used to synchronously trigger a digital real-time oscilloscope to perform data acquisition and correlation demodulation; the difference between the driving frequencies of the sideband modulation of the first single-sideband modulator and the second single-sideband modulator is equal to the Brillouin frequency.

[0011] The high-positioning-precision Brillouin sensing device with chaotic frequency-domain correlation demodulation further includes an optical isolator, which is arranged between the optical polarization scrambler and the sensing optical fiber; the sensing optical fiber adopts G652 single-mode optical fiber or G655 single-mode optical fiber; the first optical amplifier and the second optical amplifier are erbium-doped fiber amplifiers, and the first beam splitter, the second beam splitter, the third beam splitter, and the combiner are all 1×2 optical fiber couplers.

[0012] The central wavelength of the phase-mode chaotic laser output by the phase-mode chaotic laser source is 1550nm, the -3dB spectrum line width is 6.7-10.5GHz, and the spectrum shape presents a symmetrical Gaussian distribution.

[0013] The high positioning accuracy Brillouin sensing device with chaotic frequency domain correlation demodulation also includes a programmable optical delay generator, which is arranged in the optical path of the pump light or the detection light and is used to adjust the optical path difference between the pump light and the detection light.

[0014] The specific method for the digital real-time oscilloscope to perform the correlation demodulation process is:

[0015] Accurately locate the event area according to the beat frequency signal output by the first photodetector;

[0016] Temperature and strain information are obtained by demodulating the Brillouin gain and / or loss signal output by the second photodetector.

[0017] In addition, the present invention also provides a high positioning accuracy Brillouin sensing method based on chaotic frequency domain correlation demodulation, which is implemented based on the above device and includes the following steps:

[0018] S1, starting device;

[0019] S2. synchronously collecting the Brillouin beat signal detected by the first photodetector and the Brillouin gain and / or loss signal detected by the second photodetector, and synchronously triggering the collection according to the low-frequency chirp signal output by the microwave signal source;

[0020] S3. Perform frequency domain correlation demodulation on the Brillouin gain signal, the Brillouin loss signal, or the Brillouin gain loss signal and the chirp signal driving the second single-sideband modulator to obtain the temperature and strain magnitude of the event area; perform frequency domain correlation demodulation on the Brillouin beat signal and the chirp signal of the second single-sideband modulator to locate the correlation peak and obtain the corresponding temperature and strain position information.

[0021] The high positioning accuracy Brillouin sensing method using chaotic frequency domain correlation demodulation further includes the following steps:

[0022] S4. Adjust the optical path difference between the probe light and the pump light through a programmable optical delay generator so that the probe light and the pump light undergo stimulated Brillouin scattering at different positions of the sensing fiber. Repeat steps S2 to S3 to achieve distributed scanning along the entire sensing fiber and measurement and positioning of sensing information.

[0023] In step S2, the Brillouin gain signal is collected by: causing the first single sideband modulator to output a low-frequency sideband of the first light beam, and the second single sideband modulator to output a high-frequency sideband of the second light beam;

[0024] The Brillouin loss signal is collected by: causing a first single-sideband modulator to output a high-frequency sideband of a first light beam, and a second single-sideband modulator to output a low-frequency sideband of a second light beam;

[0025] In step S3, the Brillouin gain loss signal is a difference signal between the Brillouin gain signal and the Brillouin loss signal.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention proposes a high-precision Brillouin sensing device and method using chaotic frequency-domain correlation demodulation. This device uses a low-power, phase-mode chaotic laser as the sensing signal, leveraging the Gaussian broadband characteristics of the chaotic laser spectrum to generate a millimeter-scale stimulated Brillouin acoustic wave field at highly correlated locations in the optical fiber. The chaotic probe light and the frequency-chirped chaotic reference light undergo coherent beat processing and frequency-domain correlation demodulation, achieving millimeter-scale high-precision positioning along the optical fiber based on the frequency scanning accuracy and range. Simultaneously, the chaotic probe light and the frequency-chirped chaotic pump light undergo frequency-domain synchronization processing, enabling Brillouin gain intensity demodulation at a single point based on the frequency scanning time, enabling millimeter-scale spatial resolution temperature and strain measurement at specific locations in the optical fiber. Furthermore, by adjusting a high-precision programmable optical delay generator to sweep the millimeter-scale correlation peak across the optical fiber under test, measurements can be performed along the entire optical fiber. Therefore, the chaotic frequency-domain correlation demodulation method of the present invention ensures the positioning and measurement of correlation peaks at the same spatial scale, thereby achieving high-precision positioning and high-spatial resolution measurement along the entire optical fiber.

[0028] 2. The present invention adopts a phase-type chaotic laser, which has a very small peak-to-peak value of timing fluctuation, maintains chaotic random characteristics in phase, and presents a symmetrical Gaussian distribution in the spectrum. The spectral shape and spectral linewidth are both significantly tunable, which can ensure that the spatial resolution of the system reaches the millimeter level. The phase-type chaotic laser has a stable output power and a stable and adjustable spectral state, realizing distributed sensing that takes into account both high-precision positioning and high spatial resolution. In addition, the phase-type chaotic laser eliminates the signal-to-noise ratio deterioration introduced by the chaotic laser intensity fluctuation and suppresses the coherent noise introduced by the chaotic laser intensity correlation, which is more conducive to achieving the high-precision positioning and high-spatial resolution measurement described in the present invention.

[0029] 3. Compared with the Brillouin optical correlation domain analysis technology based on sinusoidal signal frequency modulation, random sequence phase coding system combined with time domain data processing, in the present invention, there is a unique Brillouin correlation peak with a spatial scale of millimeters in the optical fiber to be measured. The present invention uses the optical fiber frequency domain analysis method to achieve millimeter-level high-precision positioning of the position along the optical fiber. The positioning accuracy always remains consistent with the spatial resolution and does not change with the change of the sensing position; the movement of the correlation peak is achieved by adjusting the high-precision optical delay generator, and the correlation peak offset is always constant, which can achieve linear, uniform, and full-coverage distributed measurement; at the same time, the spatial resolution of the system of the present invention is only determined by the coherence length of the light source. The coherence length of the light source remains unchanged during the measurement process, and high-spatial resolution measurement independent of distance can be achieved.

[0030] 4. Compared with schemes such as chaotic intensity correlation [ZL201610305960.8], multi-point parallel [ZL202010455193.5], time domain difference [ZL202010454169.X], and multiple access correlation [CN202310671501.1], the present invention does not require additional modulation of intensity light pulses for positioning. Instead, it makes full use of the frequency domain distribution characteristics of the phase chaotic laser itself, and performs high-precision, distributed positioning after correlation operation. The smaller the intensity fluctuation, the higher the positioning accuracy obtained after correlation processing. At the same time, since it is difficult to achieve high-performance time domain pulse modulation with a picosecond pulse width, the above method can only achieve centimeter-level spatial resolution measurement, and cannot simultaneously achieve millimeter-level positioning and spatial resolution sensing. The present invention does not use time domain pulse modulation to ensure that the frequency domain characteristics of the chaotic laser maintain stability and correlation, and the generated stimulated Brillouin acoustic wave field intensity is greater, the system signal-to-noise ratio is improved, and it is more conducive to achieving high-precision positioning and high spatial resolution measurement.

[0031] 5. In the present invention, both the chaotic detection light and the chaotic pump light are optically frequency modulated by a single-sideband modulator controlled by a microwave signal source. When the chaotic detection light selects the low-frequency sideband and the chaotic pump light selects the high-frequency sideband, and the frequency shift difference between the two beams of light is approximately equal to the Brillouin frequency shift of the optical fiber to be measured, the present invention can realize a gain-type chaotic Brillouin sensing system; when the chaotic detection light selects the high-frequency sideband and the chaotic pump light selects the low-frequency sideband, and the frequency shift difference between the two beams of light is approximately equal to the Brillouin frequency shift of the optical fiber to be measured, the present invention can realize a loss-type chaotic Brillouin sensing system; the present invention can improve the Brillouin signal extraction efficiency by switching between gain-type and loss-type systems, reduce the bandwidth requirement of the microwave signal source, and save costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic structural diagram of a high-positioning-precision Brillouin sensing device using chaotic frequency-domain correlation demodulation provided by an embodiment of the present invention;

[0033] In the figure: 1—phase-mode chaotic laser source, 2—first beam splitter, 3—first single-sideband modulator, 4—first erbium-doped fiber amplifier, 5—optical polarization scrambler, 6—optical isolator, 7—microwave signal source, 8—second single-sideband modulator, 9—second erbium-doped fiber amplifier, 10—second beam splitter, 11—programmable optical delay generator, 12—optical circulator, 13—sensing fiber, 14—beam combiner, 15—first photodetector, 16—tunable optical filter, 17—third beam splitter, 18—second photodetector, 19—digital real-time oscilloscope. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] like Figure 1 As shown, an embodiment of the present invention provides a high positioning precision Brillouin sensing device with chaotic frequency domain correlation demodulation, comprising: a phase-type chaotic laser source 1, wherein the phase-type chaotic laser output by the phase-type chaotic laser source 1 is divided into a first light beam and a second light beam by a first beam splitter 2, the first light beam is sequentially passed through a first single-sideband modulator 3, a first optical amplifier 4, and an optical polarization scrambler 5 and then incident on one end of a sensing optical fiber 13 as a detection light; the second light beam is passed through a second single-sideband modulator 8, a second optical amplifier 9, and a second beam splitter 10 and then split into two beams, one beam is used as a pump light and then incident on the other end of the sensing optical fiber 13 by an optical circulator 12, and the other beam is used as a pump light. The reference light is incident on the first input end of the beam combiner 14; the detection light output from the other end of the sensing optical fiber 13 is incident on the tunable optical filter 16 after passing through the optical circulator 12, and then is divided into two beams of light by the third beam splitter 17, one of which is incident on the second input end of the beam combiner 14, and the other is incident on the second photodetector 18 to obtain a Brillouin gain and / or loss signal; the light output from the output end of the beam combiner 14 is incident on the first photodetector 15 to obtain a Brillouin beat frequency signal; the first single-sideband modulator 3 is used to perform single-sideband modulation on the first light beam, and the second single-sideband modulator 8 is used to perform single-sideband chirp modulation on the second light beam.

[0037] The digital real-time oscilloscope 19 is used to collect the Brillouin gain and / or loss signals and the Brillouin beat frequency signals output by the first photodetector 15 and the second photodetector 18 , and perform related demodulation processing to obtain sensing information along the sensing optical fiber.

[0038] Furthermore, if Figure 1 As shown, a high positioning accuracy Brillouin sensing device with chaotic frequency domain correlation demodulation in this embodiment also includes a microwave signal source 7, which is used to drive the first single sideband modulator 3 to perform spectral sideband modulation on the first light beam, and drive the second single sideband modulator 8 to perform spectral sideband modulation and scanning on the second light beam, and is also used to synchronously trigger the digital real-time oscilloscope 19 to perform data acquisition and correlation demodulation; the difference between the driving frequencies of the sideband modulation of the first single sideband modulator 3 and the second single sideband modulator 8 is equal to the Brillouin frequency.

[0039] Furthermore, if Figure 1 As shown, the high-positioning-precision Brillouin sensing device using chaotic frequency-domain correlation demodulation in this embodiment also includes an optical isolator 6 disposed between the optical polarization scrambler 5 and the sensing fiber 13. The sensing fiber 13 utilizes G652 single-mode fiber or G655 single-mode fiber. The first optical amplifier 4 and the second optical amplifier 9 are erbium-doped fiber amplifiers. The first beam splitter 2, the second beam splitter 10, the third beam splitter 17, and the beam combiner 14 are all 1×2 fiber couplers with a 50:50 splitting ratio. The first photodetector 15 and the second photodetector 18 are low-noise, high-sensitivity detectors. The optical circulator 12 is a high-power optical circulator. The tunable optical filter 16 is used to filter out stray light from the detection light output from the sensing fiber.

[0040] Furthermore, in this embodiment, the central wavelength of the phase-mode chaotic laser output by the phase-mode chaotic laser source 1 is 1550 nm, the -3dB spectral linewidth is 6.7 to 10.5 GHz, and the spectral shape is a symmetrical Gaussian distribution.

[0041] Furthermore, if Figure 1 As shown, a high positioning accuracy Brillouin sensing device with chaotic frequency domain correlation demodulation in this embodiment also includes a programmable optical delay generator 11, which is arranged in the optical path of the pump light or the detection light to adjust the optical path difference between the pump light and the detection light.

[0042] Furthermore, the specific method of the digital real-time oscilloscope 19 performing the correlation demodulation process is:

[0043] The event zone is accurately located based on the beat signal output by the first photodetector 15. Specifically, in this embodiment, by performing frequency domain processing on the beat signal, position information of the sensing signal can be obtained, thereby achieving accurate location of the event zone.

[0044] Demodulate the Brillouin gain and / or loss signal output by the second photodetector 18 to obtain temperature and strain information;

[0045] The working principle of this embodiment is as follows.

[0046] 1. A phase-mode chaotic laser with a central wavelength of 1550nm, a central frequency of v0, a -3dB spectral linewidth of approximately 6.7 to 10.5GHz, and a symmetrical Gaussian spectral profile. Its theoretical spatial resolution is on the order of millimeters. The peak-to-peak fluctuations in the timing signal are very small, and the output optical power is stable. The light output from the light source is split by a first beam splitter 2 into a first beam and a second beam.

[0047] 2. The first single sideband modulator 3 and the second single sideband modulator 8 perform sideband modulation on the first light beam and the second light beam respectively. The driving frequencies of the first single sideband modulator 3 and the second single sideband modulator 8 are v1 and v2 respectively. Then the frequency of the light beam (probe light) output by the first single sideband modulator 3 is ν0±ν1, and the frequency of the light beam (pump light / reference light) output by the second single sideband modulator 8 is For ordinary single-mode optical fiber, ν1+ν2 is approximately 11 GHz. During the measurement process, the sideband modulation of the two single-sideband modulators can be switched in real time. When the first single-sideband modulator 3 selects low-frequency sideband modulation, the final measured signal is the Brillouin gain signal; when the first single-sideband modulator 3 selects high-frequency sideband modulation, the final measured signal is the Brillouin loss signal. This device can reduce the modulation signal bandwidth requirement, improve modulation stability and reduce device costs. It can also achieve dual gain and loss acquisition by switching the modulation sidebands, improving the system signal-to-noise ratio.

[0048] 3. The probe light and pump light transmitted in opposite directions produce a coherent beat effect at a specific position in the sensing fiber due to the phase correlation characteristics. The beat frequency field excites a stimulated Brillouin acoustic wave field. The width of the acoustic wave field is determined by the original linewidth Δf of the chaotic laser. Therefore, the phase-type chaotic light source of the present invention can shorten the width of the acoustic wave field to the millimeter level, thereby achieving millimeter-level spatial resolution.

[0049] 4. There is a frequency difference between the probe light and the pump light in the sensing fiber. By scanning the frequency difference Δν and collecting the probe light power change ΔI(z, Δν) at each frequency using the second photodetector 18, Brillouin gain intensity demodulation at a single point can be achieved. The expression for the probe light power change is:

[0050]

[0051] Among them, I S (z,v1),I P (z, v2) represents the power of the probe light with frequency v1 and the pump light with frequency v2 at position z of the optical fiber, g(z, Δv) is the Brillouin gain coefficient, and the spatial resolution of the system is V is the group velocity of light in the optical fiber. The present invention collects the power of the probe light at a single point by scanning the frequency difference between the pump light and the probe light, thereby achieving high-precision measurement of the Brillouin gain spectrum / loss spectrum with high spatial resolution.

[0052] 5. There is a frequency difference between the detection light and the reference light in the sensing fiber. The frequency difference between the two beams of light is scanned by a chirp signal, and the beat signal intensity of the detection light and the reference light at each frequency (i.e., the Brillouin beat signal) is collected. Based on the established baseband transfer function, frequency-domain correlation demodulation of the Brillouin frequency shift along the optical fiber is achieved.

[0053] The established baseband transfer function expression is:

[0054]

[0055] Among them, I R (z,Δv) is the power of the reference light, I S0 (L,v1),I S0 (z, v2) are the fiber L position and the probe light power at position z, respectively. Therefore, the present invention uses a chirped signal to scan the reference light frequency, collects the beat frequency signals between the probe light and the reference light in real time, calculates the baseband transfer function, and uses the baseband transfer function for demodulation. This achieves high-precision demodulation of the Brillouin frequency shift along the fiber, enabling high-precision and rapid positioning of the event zone with a positioning accuracy of Δz' = V / 2Δν. V represents the speed of light in the fiber, and Δν is the frequency difference between the probe light and the pump light.

[0056] 6. The programmable optical delay generator 11 can be used to further adjust the optical path difference between the detection light and the pump light, thereby achieving precise control of the correlation peak along the sensing optical fiber, realizing full distributed scanning without omission or duplication along the optical fiber, and ensuring high-resolution measurement of the entire event area.

[0057] Example 2

[0058] A second embodiment of the present invention provides a high-positioning-precision Brillouin sensing method using chaotic frequency-domain correlation demodulation, which is implemented based on the apparatus of the first embodiment and includes the following steps:

[0059] S1. Start the device.

[0060] S2. Synchronously collecting the Brillouin beat signal detected by the first photodetector and the Brillouin gain and / or loss signal detected by the second photodetector, and synchronously triggering the collection according to the low-frequency chirp signal output by the microwave signal source.

[0061] In step S2, the method for collecting the Brillouin gain signal is: making the first single-sideband modulator 3 output the low-frequency sideband of the first light beam, and the second single-sideband modulator 8 output the high-frequency sideband of the second light beam; the method for collecting the Brillouin loss signal is: making the first single-sideband modulator 3 output the high-frequency sideband of the first light beam, and the second single-sideband modulator 8 output the low-frequency sideband of the second light beam.

[0062] S3. Perform frequency domain correlation demodulation on the Brillouin gain signal, the Brillouin loss signal or the Brillouin gain loss signal and the chirp signal driving the second single-sideband modulator 8 to obtain the temperature and strain size of the event area; perform frequency domain correlation demodulation on the Brillouin beat signal and the chirp signal of the second single-sideband modulator 8 to locate the correlation peak and obtain the corresponding temperature and strain position information.

[0063] In step S3, the Brillouin gain loss signal is a difference signal between the Brillouin gain signal and the Brillouin loss signal.

[0064] Furthermore, this embodiment also includes the following steps:

[0065] S4. Adjust the optical path difference between the probe light and the pump light through the programmable optical delay generator 11 so that the probe light and the pump light undergo stimulated Brillouin scattering at different positions of the sensing optical fiber 13. Repeat steps S2 to S3 to achieve distributed scanning along the entire sensing optical fiber and measurement and positioning of sensing information.

[0066] 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 above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high positioning accuracy Brillouin sensing device with chaotic frequency domain correlation demodulation, characterized in that: include: A phase-type chaotic laser source (1) is provided. The phase-type chaotic laser outputted by the phase-type chaotic laser source (1) is split into two beams, namely a first beam and a second beam, by a first beam splitter (2). The first beam is sequentially passed through a first single-sideband modulator (3), a first optical amplifier (4), and an optical polarization scrambler (5) and then incident on one end of a sensing optical fiber (13) as a detection light. The second beam is passed through a second single-sideband modulator (8), a second optical amplifier (9), and a second beam splitter (10) and then split into two beams. One beam is passed through an optical circulator (12) and then incident on a sensing optical fiber ( 13), a beam of reference light is incident on the first input end of the beam combiner (14); the detection light is output by the optical circulator (12) at the other end of the sensing optical fiber (13), and is then divided into two beams of light after passing through the tunable optical filter (16) and the third beam splitter (17), one of which is incident on the second input end of the beam combiner (14), and the other is incident on the second photodetector (18) to obtain a Brillouin gain and / or loss signal; the light output from the output end of the beam combiner (14) is incident on the first photodetector (15) to obtain a Brillouin beat frequency signal; The first single sideband modulator (3) is used to perform single sideband modulation on the first light beam, and the second single sideband modulator (8) is used to perform single sideband chirp modulation on the second light beam; The digital real-time oscilloscope (19) is used to collect the Brillouin gain and / or loss signals and the Brillouin beat frequency signals output by the first photodetector (15) and the second photodetector (18), and perform related demodulation processing to obtain sensing information along the sensing optical fiber; The specific method of the digital real-time oscilloscope (19) performing the correlation demodulation process is: Performing frequency domain processing on the beat frequency signal output by the first photodetector (15) to obtain position information of the sensing signal and accurately locate the event area; Temperature and strain information are obtained by demodulating the Brillouin gain and / or loss signal output by the second photodetector (18).

2. The high positioning accuracy Brillouin sensing device with chaotic frequency domain correlation demodulation according to claim 1 is characterized in that: The invention also includes a microwave signal source (7), which is used to drive the first single-sideband modulator (3) to perform spectral sideband modulation on the first light beam, and drive the second single-sideband modulator (8) to perform spectral sideband modulation and scanning on the second light beam, and is also used to synchronously trigger a digital real-time oscilloscope (19) to perform data acquisition and correlation demodulation; the difference between the driving frequencies of the sideband modulation of the first single-sideband modulator (3) and the second single-sideband modulator (8) is equal to the Brillouin frequency.

3. The high positioning accuracy Brillouin sensing device with chaotic frequency domain correlation demodulation according to claim 1 is characterized in that: The optical isolator (6) is further included, and the optical isolator (6) is arranged between the optical polarization scrambler (5) and the sensing optical fiber (13); the sensing optical fiber (13) adopts G652 single-mode optical fiber or G655 single-mode optical fiber; the first optical amplifier (4) and the second optical amplifier (9) are erbium-doped optical fiber amplifiers, and the first beam splitter (2), the second beam splitter (10), the third beam splitter (17), and the beam combiner (14) are all 1×2 optical fiber couplers.

4. The high positioning accuracy Brillouin sensing device with chaotic frequency domain correlation demodulation according to claim 1, characterized in that: The phase-type chaotic laser source (1) outputs a phase-type chaotic laser with a central wavelength of 1550 nm, a -3dB spectrum linewidth of 6.7 to 10.5 GHz, and a symmetrical Gaussian distribution of the spectrum.

5. The high positioning accuracy Brillouin sensing device with chaotic frequency domain correlation demodulation according to claim 1 is characterized in that: It also includes a programmable optical delay generator (11), which is arranged on the optical path of the pump light or the detection light and is used to adjust the optical path difference between the pump light and the detection light.

6. A high positioning accuracy Brillouin sensing method based on chaotic frequency domain correlation demodulation, characterized in that: The device according to any one of claims 1 to 5 is implemented, comprising the following steps: S1, starting device; S2. synchronously collecting the Brillouin beat signal detected by the first photodetector and the Brillouin gain and / or loss signal detected by the second photodetector, and synchronously triggering the collection according to the low-frequency chirp signal output by the microwave signal source; S3, performing frequency domain correlation demodulation on the Brillouin gain signal, the Brillouin loss signal or the Brillouin gain loss signal and the chirp signal driving the second single-sideband modulator (8) to obtain the temperature and strain magnitude of the event area; performing frequency domain correlation demodulation on the Brillouin beat signal and the chirp signal of the second single-sideband modulator (8) to locate the correlation peak and obtain the corresponding temperature and strain position information.

7. The high positioning accuracy Brillouin sensing method of chaotic frequency domain correlation demodulation according to claim 6 is characterized in that: The following steps are also included: S4. The optical path difference between the detection light and the pump light is adjusted by the programmable optical delay generator (11), so that the detection light and the pump light undergo stimulated Brillouin scattering at different positions of the sensing optical fiber (13). Steps S2 to S3 are repeated to achieve distributed scanning along the entire sensing optical fiber and measurement and positioning of sensing information.

8. The high positioning accuracy Brillouin sensing method of chaotic frequency domain correlation demodulation according to claim 6 is characterized in that: In step S2, the Brillouin gain signal is collected by: causing the first single-sideband modulator (3) to output the low-frequency sideband of the first light beam, and the second single-sideband modulator (8) to output the high-frequency sideband of the second light beam; The Brillouin loss signal is collected by: causing the first single-sideband modulator (3) to output a high-frequency sideband of the first light beam, and the second single-sideband modulator (8) to output a low-frequency sideband of the second light beam; In step S3, the Brillouin gain loss signal is a difference signal between the Brillouin gain signal and the Brillouin loss signal.

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