Gain differential measurement type high performance chaotic Brillouin sensing device and method

Abstract

The present invention relates to the field of distributed optical fiber sensing, and discloses a gain differential measurement type high-performance chaotic Brillouin sensing device and method. The output of a chaotic laser source in the device is divided into a first and a second chaotic laser. The first chaotic laser is sequentially divided into a detection light and a differential reference light after passing through a single-sideband modulator, an erbium-doped optical fiber amplifier, and a second beam splitter. The detection light is incident on one end of the sensing optical fiber and outputted from the other end through a first optical circulator to be detected by a first photodetector, and the differential reference light is detected by a second photodetector; the second chaotic laser is sequentially divided into a pump light and a cross-correlation reference light after passing through an optical delay line, a semiconductor optical amplifier, and a third beam splitter. The pump light is amplified and injected into the sensing optical fiber from the other end, and the cross-correlation reference light is detected by a third photodetector; the three-way detection signal is processed by a computer. The present invention can suppress the interference of chaotic intensity noise, improve the system signal-to-noise ratio, and broaden the sensing distance while ensuring high spatial resolution.

Description

Technical Field

[0001] The invention relates to the field of distributed optical fiber sensing, and in particular to a gain differential measurement type high-performance chaotic Brillouin sensing device and method. Background Art

[0002] Distributed fiber optic sensing technology is one of the high-tech technologies that has attracted much attention and is developing rapidly in the world today. It is an important support for the construction of a new type of infrastructure security network that is high-speed, ubiquitous, integrated, interconnected, safe and efficient in the national plan. Distributed fiber optic sensing technology has unique strategic value and huge economic benefits, and plays an irreplaceable role in the fields of submarine earthquake monitoring, oil and gas resource exploration, military border security, etc.

[0003] In the distributed fiber Brillouin sensing system, spatial resolution and sensing distance are important technical indicators. Spatial resolution reflects the minimum length of the fiber applied temperature and strain that the sensing system can distinguish, and sensing distance is the maximum distance that the system can achieve effective sensing. At present, the traditional time-domain gated chaotic Brillouin optical correlation domain analysis (BOCDA) technology uses traditional chaotic laser as the light source. In order to avoid nonlinear effects, the power of the pulsed light cannot be too high, and the energy loss of the pulsed light is serious as the sensing distance increases. The chaotic light intensity noise further causes the Brillouin gain signal at the end of the optical fiber to be extremely weak, which is easily submerged in the intensity noise of the chaos itself, making it difficult to achieve long-distance precise positioning.

[0004] Therefore, it is necessary to invent a high-performance chaotic Brillouin distributed fiber optic sensing technology to suppress the interference of chaotic intensity noise on gain information, improve the system signal-to-noise ratio, and meet the needs of long-distance and high spatial resolution. Summary of the invention

[0005] In order to solve the problem that the chaotic intensity noise interferes with the gain information and limits the expansion of the sensing distance in the existing chaotic BOCDA system, the present invention provides a gain differential measurement type chaotic Brillouin sensing device and method, which aims to improve the signal-to-noise ratio of the sensing system and expand the sensing distance while ensuring high spatial resolution.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a gain differential measurement type high-performance chaotic Brillouin sensing device, comprising: a chaotic laser source, the chaotic laser output by the chaotic laser source is divided into a first chaotic laser and a second chaotic laser by a first beam splitter, the first chaotic laser passes through a single-sideband modulator and an erbium-doped fiber amplifier in sequence, and is then divided into a detection light and a differential reference light by a second beam splitter, the detection light is incident on one end of the sensing fiber, and the differential reference light is detected by a second photodetector; the second chaotic laser passes through an optical delay line and a semiconductor optical amplifier in sequence, and is then divided into a pump light and a cross-correlation reference light by a third beam splitter, the pump light is optically amplified by a pulse optical amplifier, and is then injected from the other end of the sensing fiber by a first optical circulator, and the cross-correlation reference light is detected by a third photodetector; the transmission signal in the sensing fiber is output by the first optical circulator and detected by the first photodetector;

[0007] The single sideband modulator is used to modulate the first chaotic laser so that it produces a frequency downshift, and the downshift amount is equal to the Brillouin frequency shift amount in the sensing optical fiber; the erbium-doped fiber amplifier is used to amplify the first chaotic laser after the frequency downshift; the optical delay line is used to adjust the delay of the second chaotic laser, and the semiconductor optical amplifier is used to modulate the continuous second chaotic laser into a pulsed chaotic light;

[0008] The three-way detection signals are synchronously collected by the data acquisition unit and sent to the computer for data processing.

[0009] The specific method of computer data processing is:

[0010] Performing a cross-correlation operation on the transmission signal detected by the first photodetector and the differential reference signal detected by the second photodetector to obtain an optical path difference between the two signals;

[0011] Then, the transmission signal and the differential reference signal are matched with an optical path difference, and then a differential operation is performed on the transmission signal after the optical path difference matching and the differential reference signal to obtain chaotic Brillouin gain information;

[0012] The obtained chaotic Brillouin gain information is cross-correlated with the cross-correlation reference signal detected by the third photodetector to achieve the location of the correlation peak.

[0013] The chaotic laser source comprises a laser, a fiber ring oscillator and a feedback loop. The laser emitted by the laser is incident on the feedback loop via the fiber ring oscillator. The feedback loop is used to feed back the incident laser part to the fiber ring oscillator and the laser in sequence, so that the laser outputs chaotic laser. The chaotic laser output by the laser is output after passing through the fiber ring oscillator and the feedback loop. The fiber ring oscillator is used to raise the low-frequency energy in the chaotic laser output by the laser.

[0014] The feedback loop includes a second optical circulator, a fourth beam splitter, a polarization controller, and an attenuator; the chaotic laser source also includes a first optical isolator;

[0015] The laser emitted by the distributed feedback laser passes through the fiber ring oscillator and the second optical circulator, and is then divided into two beams by the fourth beam splitter, one of which returns to the second optical circulator after passing through an attenuator and a polarization controller, and then returns to the distributed feedback laser after passing through the second optical circulator and the fiber ring oscillator, so that it outputs a chaotic laser with raised low-frequency energy, and the chaotic laser is output after passing through the fiber ring oscillator, the fourth beam splitter and the first optical isolator.

[0016] The chaotic laser source also includes a fifth beam splitter and a power meter; the fifth beam splitter is arranged between the distributed feedback laser and the fiber ring oscillator, an input end of which is connected to the fiber ring oscillator, one output end is connected to the laser, and the other output end is connected to the power meter, and the power meter is used to monitor the light intensity returned to the distributed feedback laser.

[0017] The gain differential measurement type high-performance chaotic Brillouin sensing device also includes a light polarization scrambler and a second optical isolator, which are arranged between the erbium-doped fiber amplifier and the second beam splitter; the light polarization scrambler is used to reduce the polarization sensitivity of the first chaotic laser, and the second optical isolator is used to isolate the stray light output from one end of the sensing optical fiber.

[0018] The first beam splitter, the second beam splitter and the third beam splitter are × optical fiber couplers, the output end of the chaotic laser source is connected to the input end of the first beam splitter through a single-mode optical fiber jumper; the first output end of the first beam splitter is connected to the input end of the single-sideband modulator through a single-mode optical fiber jumper; the output end of the single-sideband modulator is connected to the input end of the erbium-doped fiber amplifier through a single-mode optical fiber jumper; the output end of the erbium-doped fiber amplifier is connected to the input end of the optical polarization scrambler through a single-mode optical fiber jumper; the output end of the optical polarization scrambler is connected to the input end of the second optical isolator through a single-mode optical fiber jumper; the output end of the second optical isolator is connected to the input end of the second beam splitter through a single-mode optical fiber jumper; the first output end of the second beam splitter is connected to one end of the sensing optical fiber; the second output end of the second beam splitter is connected to the input end of the second photodetector through a single-mode optical fiber jumper;

[0019] The second output end of the first beam splitter is connected to the input end of the optical delay line through a single-mode optical fiber jumper; the output end of the optical delay line is connected to the input end of the semiconductor optical amplifier through a single-mode optical fiber jumper; the output end of the semiconductor optical amplifier is connected to the input end of the third beam splitter through a single-mode optical fiber jumper; the first output end of the third beam splitter is connected to the input end of the pulse optical amplifier through a single-mode optical fiber jumper; the output end of the pulse optical amplifier is connected to the first port of the first optical circulator through a single-mode optical fiber jumper; the second port of the first optical circulator is connected to the other end of the sensing optical fiber, and the third port is connected to the input end of the first photodetector through a single-mode optical fiber jumper; the second output end of the third beam splitter is connected to the input end of the third photodetector through a single-mode optical fiber jumper.

[0020] The sensing optical fiber adopts G652 single-mode optical fiber or G655 single-mode optical fiber.

[0021] In addition, the present invention provides a gain differential measurement type high-performance chaotic Brillouin sensing method, which is implemented using the device and includes the following steps:

[0022] S1, causing the probe light and the pump light to undergo stimulated Brillouin amplification in the sensing optical fiber;

[0023] S2, cross-correlate the transmission signal detected by the first photodetector with the differential reference signal detected by the second photodetector to obtain the optical path difference of the two signals; then match the optical path difference of the transmission signal with the differential reference signal, and then perform differential operation on the transmission signal after the optical path difference matching and the differential reference signal to obtain chaotic Brillouin gain information; cross-correlate the obtained chaotic Brillouin gain information with the cross-correlation reference signal detected by the third photodetector to locate the correlation peak;

[0024] S3. Adjust the optical path of the pump light through the optical delay line so that the probe light and the pump light undergo stimulated Brillouin amplification at different positions of the sensing optical fiber, and repeat step S2 to obtain event information along the entire sensing optical fiber.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention uses gain differential measurement to extract chaotic Brillouin gain information and combines the cross-correlation algorithm to realize the location of the correlation peak. Specifically, the present invention uses the δ-linear autocorrelation characteristics of chaotic signals, and performs correlation operations on the transmission signal and the differential reference signal to obtain the time delay of the two signals, and accurately obtains the optical path difference of the two signals according to the sampling rate of the data acquisition unit, thereby achieving optical path matching of the two signals and performing differential processing to obtain chaotic Brillouin gain information, and then performing cross-correlation operations on the chaotic Brillouin gain information obtained by difference and the cross-correlation reference signal to realize the location of the correlation peak. Therefore, the present invention can eliminate the flooding of the gain information by the intensity noise of the chaos itself, improve the system signal-to-noise ratio, and expand the sensing distance while ensuring high spatial resolution.

[0027] 2. The present invention provides a gain differential measurement type high-performance chaotic Brillouin sensing device and method. Based on the characteristics of the chaotic laser's flat phase dynamic spectrum and high low-frequency energy, the optical fiber ring oscillator is used to generate a self-delay interference effect, which converts the phase dynamics of the chaotic signal into intensity fluctuations, greatly improving the low-frequency energy of the chaotic signal. A broadband chaotic laser with low-frequency energy boost is used as the light source, making the energy distribution of the chaotic signal more suitable for the low-frequency response characteristics of the electronic acquisition device and the low-frequency distribution characteristics of the chaotic Brillouin gain information, greatly improving the energy utilization efficiency of the chaotic signal and improving the sensing performance of the chaotic BOCDA system.

[0028] 3. Compared with the existing phase modulation differential scheme (Journal of Lightwave Technology, 2023, 41(1): 341-346), the present invention does not require the use of expensive phase modulators for phase modulation while ensuring long-distance high spatial resolution, greatly reducing the complexity and cost of the experiment. Compared with the existing detection path differential scheme (Optics Express, 2018, 26(6): 6916-6928), the sensing distance of the present invention is significantly improved and does not require the use of polarization-maintaining optical fiber, which has more superior practicality.

[0029] 4. Compared with the existing time-domain differential high-speed chaotic Brillouin optical coherence domain monitoring scheme (Chinese invention patent ZL202010454169.X), the present invention can effectively suppress the interference of chaotic intensity noise on gain information, improve the system signal-to-noise ratio, and broaden the sensing distance while ensuring high spatial resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the structure of a gain differential measurement type high-performance chaotic Brillouin sensor device provided in Embodiment 1 of the present invention;

[0031] Figure 2Schematic diagram of the structure of the chaotic laser source used in the first embodiment of the present invention;

[0032] Figure 3 The spectrum diagram and timing diagram of the low-frequency energy-boosted chaotic laser output by the chaotic laser source in the embodiment of the present invention are compared with the traditional single-feedback chaotic laser;

[0033] Figure 4 The chaotic Brillouin gain information obtained by differential analysis in the embodiment of the present invention and the correlation peak distribution obtained by cross-correlation operation between the chaotic Brillouin gain information and the pump pulse signal are shown in FIG.

[0034] Figure 5 A schematic diagram of the structure of a gain differential measurement type high-performance chaotic Brillouin sensor device provided in the second embodiment of the present invention;

[0035] In the figure: 1-chaotic laser source, 2-first beam splitter, 3-single sideband modulator, 4-erbium-doped fiber amplifier, 5-polarization scrambler, 6-second optical isolator, 7-second beam splitter, 8-broadband microwave signal source, 9-optical delay line, 10-semiconductor optical amplifier, 11-third beam splitter, 12-pulse optical amplifier, 13-first optical circulator, 14-sensing optical fiber, 15-first photodetector, 16-second photodetector, 17-third photodetector, 18-data acquisition unit, 19-computer; 20-laser, 21-fifth beam splitter, 22-fiber ring oscillator, 23-second optical circulator, 24-fourth beam splitter, 25-first optical isolator, 26-power meter, 27-polarization controller, 28-attenuator. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] Embodiment 1

[0038] like Figure 1As shown, the first embodiment of the present invention provides a gain differential measurement type high-performance chaotic Brillouin sensing device, comprising: a chaotic laser source 1, wherein the chaotic laser output by the chaotic laser source 1 is divided into a first chaotic laser and a second chaotic laser by a first beam splitter 2, the first chaotic laser passes through a single sideband modulator 3 and an erbium-doped fiber amplifier 4 in sequence, and then is divided into a detection light and a differential reference light by a second beam splitter 7, the detection light is incident on one end of a sensing optical fiber 14, and the differential reference light is detected by a second photodetector 16; the second chaotic laser After passing through the optical delay line 9 and the semiconductor optical amplifier 10 in sequence, the pump light is divided into a pump light and a cross-correlation reference light by the third beam splitter 11. After being optically amplified by the pulse optical amplifier 12, the pump light is injected from the other end of the sensing optical fiber 14 through the first optical circulator 13, and the cross-correlation reference light is detected by the third photodetector 17; the pump light and the detection light meet in the sensing optical fiber 14 to cause stimulated Brillouin amplification; the transmission signal in the sensing optical fiber 14 is output by the first optical circulator 13 and detected by the first photodetector 15.

[0039] The single sideband modulator 3 is used to modulate the first chaotic laser so that it produces a frequency downshift, and the downshift amount is equal to the Brillouin frequency shift amount in the sensing optical fiber 14; the erbium-doped fiber amplifier 4 is used to amplify the first chaotic laser after the frequency downshift; the optical delay line 9 is used to adjust the delay of the second chaotic laser, and the semiconductor optical amplifier 10 is used to modulate the continuous second chaotic laser into a pulsed chaotic light;

[0040] Specifically, the three detection signals are synchronously collected by the data collection unit 18 and sent to the computer 19 for data processing.

[0041] Specifically, in this embodiment, the specific method for computer 19 to perform data processing is:

[0042] Perform a cross-correlation operation on the transmission signal detected by the first photodetector 15 and the differential reference signal detected by the second photodetector 16 to obtain the optical path difference of the two signals;

[0043] Then, after matching the optical path difference of the transmission signal and the differential reference signal, performing a differential operation on the transmission signal after the optical path difference matching and the differential reference signal to obtain chaotic Brillouin gain information;

[0044] The obtained chaotic Brillouin gain information is cross-correlated with the cross-correlation reference signal detected by the third photodetector 17 to achieve the location of the correlation peak.

[0045] Specifically, in this embodiment, the first beam splitter 2, the second beam splitter 7 and the third beam splitter 11 are 1×2 fiber couplers, the output end of the chaotic laser source 1 is connected to the input end of the first beam splitter 2 through a single-mode fiber jumper; the first output end of the first beam splitter 2 is connected to the input end of the single-sideband modulator 3 through a single-mode fiber jumper; the output end of the single-sideband modulator 3 is connected to the input end of the erbium-doped fiber amplifier 4 through a single-mode fiber jumper; the output end of the erbium-doped fiber amplifier 4 is connected to the input end of the second beam splitter 7 through a single-mode fiber jumper; the first output end of the second beam splitter 7 is connected to one end of the sensing fiber 14; the second output end of the second beam splitter 7 is connected to the input end of the second photodetector 16 through a single-mode fiber jumper;

[0046] The second output end of the first beam splitter 2 is connected to the input end of the optical delay line 9 through a single-mode fiber jumper; the output end of the optical delay line 9 is connected to the input end of the semiconductor optical amplifier 10 through a single-mode fiber jumper; the output end of the semiconductor optical amplifier 10 is connected to the input end of the third beam splitter 11 through a single-mode fiber jumper; the first output end of the third beam splitter 11 is connected to the input end of the pulse optical amplifier 12 through a single-mode fiber jumper; the output end of the pulse optical amplifier 12 is connected to the first port of the first optical circulator 13 through a single-mode fiber jumper; the second port of the first optical circulator 13 is connected to the other end of the sensing optical fiber 14, and the third port is connected to the input end of the first photodetector 15 through a single-mode fiber jumper; the second output end of the third beam splitter 11 is connected to the input end of the third photodetector 17 through a single-mode fiber jumper. In the first optical circulator 13, the light input to the first port is output from the second port, and the light input to the second port is output from the third port.

[0047] Furthermore, in this embodiment, the chaotic laser source 1 is preferably a chaotic laser source after low-frequency energy boosting, such as Figure 2 As shown, the chaotic laser source 1 includes a laser 20, a fiber ring oscillator 22 and a feedback loop. The laser emitted by the laser 20 is incident to the feedback loop through the fiber ring oscillator 22. The feedback loop is used to feed back the incident laser part to the fiber ring oscillator 22 and the laser 20 in sequence, so that the laser 20 outputs chaotic laser; the chaotic laser output by the laser 20 is output after passing through the fiber ring oscillator 22 and the feedback loop; the fiber ring oscillator 22 is used to raise the low-frequency energy in the chaotic laser output by the laser 20. Specifically, the laser 20 is a distributed feedback laser.

[0048] In this embodiment, based on the characteristics of the chaotic laser's flat phase dynamic spectrum and high low-frequency energy, the fiber ring oscillator 22 is used to generate a self-delay interference effect, and the phase dynamics of the chaotic signal is converted into intensity fluctuations, which greatly improves the low-frequency energy of the chaotic signal. The broadband chaotic laser with low-frequency energy raised is used as a light source, so that the energy distribution of the chaotic signal is more suitable for the low-frequency response characteristics of the electronic acquisition device and the low-frequency distribution characteristics of the chaotic Brillouin gain information, which greatly improves the energy utilization efficiency of the chaotic signal and improves the sensing performance of the chaotic BOCDA system.

[0049] Furthermore, if Figure 2 As shown, the feedback loop includes a second optical circulator 23, a fourth beam splitter 24, a polarization controller 27, and an attenuator 28; the chaotic laser source 1 also includes a first optical isolator 25; the laser emitted by the distributed feedback laser 20 passes through the fiber ring oscillator 22 and the second optical circulator 23, and is divided into two beams by the fourth beam splitter 24, one of which is used as feedback light and returns to the second optical circulator 23 after passing through the attenuator 28 and the polarization controller 27, and then returns to the distributed feedback laser 20 after passing through the second optical circulator 23 and the fiber ring oscillator 22, so that it outputs a chaotic laser with raised low-frequency energy, and the chaotic laser is output after passing through the fiber ring oscillator 22, the fourth beam splitter 24 and the first optical isolator 25. The polarization controller 27 and the attenuator 28 can control the intensity and polarization of the feedback light, so that the laser 20 outputs a chaotic laser.

[0050] In addition, in this embodiment, the feedback loop can also be a feedback loop of other chaotic laser generating devices in the field. For example, the second optical circulator 23 can also be replaced by a reflector arranged on the outside of the polarization controller 27. The light of the branch where the attenuator 28 and the polarization controller 27 are located can also be returned to the laser 20 through the reflector, so that it outputs chaotic laser.

[0051] Furthermore, in this embodiment, the chaotic laser source 1 also includes a fifth beam splitter 21 and a power meter 26; the fifth beam splitter 21 is arranged between the distributed feedback laser 20 and the fiber ring oscillator 22, an input end of which is connected to the fiber ring oscillator 22, one output end is connected to the laser 20, and the other output end is connected to the power meter 26, and the power meter 26 is used to monitor the light intensity returned to the distributed feedback laser 20.

[0052] Specifically, in this embodiment, the sensing optical fiber 14 adopts G652 single-mode optical fiber or G655 single-mode optical fiber. The semiconductor optical amplifier 10 is an OAM-SOA-PL type high extinction ratio semiconductor optical amplifier, and the data acquisition unit 18 is an oscilloscope. Specifically, in this embodiment, a broadband microwave signal source 8 is also included, and the broadband microwave signal source 8 is used to drive the single-sideband modulator 3. The optical delay line 9 is a high-precision optical delay line. The optical delay line used in this embodiment has a delay range of 168mm, a delay accuracy of 0.3μm, and a delay step of 0.001mm.

[0053] Specifically, the working principle of a gain differential measurement type high-performance chaotic Brillouin sensor device of this embodiment is as follows:

[0054] 1. Chaotic laser source 1 outputs a broadband chaotic laser with a wavelength of 1550nm, a center frequency of ν0, and a significant increase in low-frequency energy. Figure 3 The output signal of the light source is divided into the first chaotic laser and the second chaotic laser by the first beam splitter 2 formed by a 10:90 1×2 fiber coupler.

[0055] 2. The first chaotic laser (90%) is modulated by the single sideband modulator 3 to shift the frequency of the original signal downward, and the output signal frequency is v0-v B , where v B is the Brillouin frequency shift, and its value is 11 GHz for ordinary quartz single-mode optical fiber. The single-sideband modulator 3 is driven by a broadband microwave signal source 8, which can output a sinusoidal signal with a frequency range of 9 kHz to 13 GHz and an amplitude range of -20 to 2 dBm. The modulated optical signal is amplified by an erbium-doped fiber amplifier 4 to compensate for the optical power loss caused by the modulation. The amplified optical signal is divided into two paths by the second beam splitter 7 formed by a 20:80 1×2 optical fiber coupler, and the output of the first output end (80%) is incident on the sensing optical fiber 14 as the detection light, and the output of the second output end (20%) of the second beam splitter 7 is converted into an electrical signal by the second photodetector 16 as the differential reference light and input into the data acquisition unit 18 by a high-frequency coaxial cable for real-time signal acquisition.

[0056] 3. The second chaotic laser (10%) of the other path is pulse modulated by the OAM-SOA-PL type high extinction ratio semiconductor optical amplifier 10 after passing through the high-precision optical delay line 9. The purpose of the modulation is to prevent non-peak amplification outside the central correlation peak and noise accumulation along the optical fiber, thereby improving the sensing distance of the system. Then, the third beam splitter 11 formed by the 10:90 1×2 optical fiber coupler is divided into two beams. The beam output from the first output end (90%) is used as the pump light. After the pump light is optically amplified by the pulse optical amplifier 12, it is incident into the sensing optical fiber 14 by the first optical circulator 13 and meets the detection light in the sensing optical fiber 14 and undergoes stimulated Brillouin scattering. The beam output from the second output end (10%) is converted into an electrical signal by the third photodetector 17 as a cross-correlation reference light and input into the data acquisition unit 18 by a high-frequency coaxial cable for real-time signal acquisition.

[0057] 4. The detection light and the pump light transmitted in opposite directions meet at a certain position in the sensing optical fiber 14 to generate a correlation peak, and the stimulated Brillouin amplification effect is confined within the correlation peak. The transmission signal output from the third port of the first optical circulator 13 is converted into an electrical signal by the first photodetector 15 and input into the data acquisition unit 18 through a high-frequency coaxial cable for real-time signal acquisition.

[0058] 5. By performing correlation operation on the transmission signal and the differential reference signal, the time delay of the two signals is obtained, and the optical path difference of the two signals can be accurately obtained according to the sampling rate of the data acquisition unit 18.

[0059] Since the chaotic Brillouin gain information is weak, its influence on matching the optical path difference is ignored. Assuming that the transmission signal x1(t) can be expressed as x1(t)=s(t), the differential reference signal x2(t) can be expressed as x2(t)=s(t+D c ), where D c is the time delay of the two signals, then the mutual correlation coefficient between the transmission signal x1(t) and the differential reference signal x2(t) is:

[0060] R x1x2 =E[s(t)s(t+D c +τ1)]=R ss (τ1+D c ); (1)

[0061] Among them, R x1x2 represents the cross-correlation coefficient between the transmission signal and the differential reference signal, E represents the cross-correlation operation, R ss (τ1+D c ) represents the first cross-correlation function, τ1 represents the cross-correlation independent variable; when the cross-correlation function of the transmission signal x1(t) and the differential reference signal x2(t) reaches the maximum value, R ss (τ1+Dc ) also reaches its maximum value, and because R ss (τ1+D c )≤R ss (0), so the cross-correlation independent variable τ1 when the cross-correlation function reaches its maximum value is the time delay D c The time delay information is obtained through cross-correlation, and the optical path difference of the two signals can be accurately obtained according to the sampling rate of the data acquisition unit.

[0062] By using the obtained time delay information, the chaotic light information emitted by the light source at the same time can be matched in two sets of time series, and then differential processing can be performed, which is equivalent to eliminating the optical path difference between the two paths.

[0063] 6. Perform differential processing on the transmission signal and the differential reference signal, such as Figure 4 As shown in (a), the delay D is obtained by c The result of differentiating the transmission signal and the differential reference signal effectively suppresses the interference of chaotic intensity noise on the gain information and obtains chaotic Brillouin gain information.

[0064] P(t)=P probe (t)+P gain (t); (2)

[0065] Where P(t) represents the power of the transmitted signal, P probe (t) represents the transmission power of the detection light, P gain (t) represents the power of chaotic Brillouin gain information. Through differential processing, weak chaotic Brillouin gain information is obtained.

[0066] 7. Perform correlation operation through chaotic Brillouin gain information and cross-correlation reference signal, such as Figure 4 As shown in (b), it is the result of cross-correlation between chaotic Brillouin gain information and cross-correlation reference signal. The correlation peak can be located according to the cross-correlation result.

[0067] Assuming that the Brillouin gain signal x3(t) can be expressed as x3(t)=h(t), the cross-correlation reference signal x4(t) can be expressed as x4(t)=h(t+D x ), where D x is the delay of the two signals, then the mutual correlation coefficient between the transmission signal x3(t) and the differential reference signal x4(t) is:

[0068] R x3x4 =E[h(t)h(t+D x +τ2)]=R hh (τ2+D x ); (3)

[0069] Among them, Rx3x4 represents the mutual correlation coefficient of two signals, E represents the cross-correlation operation, R hh (τ2+D x ) represents the second cross-correlation function, τ2 represents the autocorrelation variable, when the cross-correlation function of the chaotic Brillouin gain signal x3(t) and the cross-correlation reference signal x4(t) reaches the maximum value, R hh (τ2+D x ) also reaches its maximum value, and because R hh (τ2+D x )≤R hh (0), so the second cross-correlation function R hh (τ2+D x )The time τ2 when the maximum value is obtained is the delay D x Therefore, by performing cross-correlation operation on the two signals, the time delay D corresponding to the correlation peak of the cross-correlation function is determined. x The value of can achieve accurate positioning of the correlation peak.

[0070] Embodiment 2

[0071] like Figure 5 As shown, the second embodiment of the present invention provides a gain differential measurement type high-performance chaotic Brillouin sensing device. Similar to the first embodiment, it includes: a chaotic laser source 1, a first beam splitter 2, a single sideband modulator 3, an erbium-doped fiber amplifier 4, a second beam splitter 7, an optical delay line 9, a semiconductor optical amplifier 10, a third beam splitter 11, a pulse optical amplifier 12, a first optical circulator 13, the sensing fiber 14, a first photodetector 15, a second photodetector 16, a third photodetector 17, a data acquisition unit 18 and a computer 19. Different from the first embodiment, this embodiment also includes an optical polarization scrambler 5 and a second optical isolator 6, and the optical polarization scrambler 5 and the second optical isolator 6 are arranged between the erbium-doped fiber amplifier 4 and one end of the second beam splitter 7; the optical polarization scrambler 5 is used to reduce the polarization sensitivity of the first chaotic laser and suppress the gain fluctuation caused by polarization, and the second optical isolator 6 is used to isolate the stray light output from one end of the sensing fiber 14 to prevent it from returning to the erbium-doped fiber amplifier 4.

[0072] In this embodiment, the chaotic laser output by the chaotic laser source 1 is divided into a first chaotic laser and a second chaotic laser by the first beam splitter 2. The first chaotic laser passes through the single-sideband modulator 3, the erbium-doped fiber amplifier 4, the optical scrambler 5 and the second optical isolator 6 in sequence, and is then divided into a detection light and a differential reference light by the second beam splitter 7. The detection light is incident on one end of the sensing optical fiber 14, and the differential reference light is detected by the second photodetector 16; the second chaotic laser passes through the optical delay line 9 and the semiconductor optical amplifier 10 in sequence, and is then divided into a pump light and a cross-correlation reference light by the third beam splitter 11. After the pump light is optically amplified by the pulse optical amplifier 12, it is injected from the other end of the sensing optical fiber 14 through the first optical circulator 13, and the cross-correlation reference light is detected by the third photodetector 17; the transmission signal in the sensing optical fiber 14 is output by the first optical circulator 13 and then detected by the first photodetector 15. Among them, the single-sideband modulator 3 is used to modulate the first chaotic laser to make it produce a frequency downshift, and the downshift amount is equal to the Brillouin frequency shift in the sensing optical fiber 14; the erbium-doped fiber amplifier 4 is used to amplify the first chaotic laser after the frequency downshift; the optical delay line 9 is used to adjust the delay of the second chaotic laser, and the semiconductor optical amplifier 10 is used to modulate the continuous second chaotic laser into pulsed chaotic light.

[0073] Embodiment 3

[0074] Embodiment 3 of the present invention provides a gain differential measurement type high-performance chaotic Brillouin sensing method, which is implemented by the device described in Embodiment 1 or 2 and includes the following steps:

[0075] S1, causing the probe light and the pump light to undergo stimulated Brillouin amplification in the sensing optical fiber;

[0076] S2, cross-correlate the transmission signal detected by the first photodetector 15 with the differential reference signal detected by the second photodetector 16 to obtain the optical path difference of the two signals; then match the optical path difference of the transmission signal with the differential reference signal, and then perform differential operation on the transmission signal after the optical path difference matching and the differential reference signal to obtain chaotic Brillouin gain information; cross-correlate the obtained chaotic Brillouin gain information with the cross-correlation reference signal detected by the third photodetector 17 to locate the correlation peak;

[0077] S3. Adjust the optical path of the pump light through the optical delay line 9 so that the probe light and the pump light undergo stimulated Brillouin amplification at different positions of the sensing optical fiber, and repeat step S2 to obtain event information along the entire sensing optical fiber.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gain differential measurement type high performance chaotic Brillouin sensor device, characterized in that: include: A chaotic laser source (1), wherein the chaotic laser output by the chaotic laser source (1) is divided into a first chaotic laser and a second chaotic laser through a first beam splitter (2); the first chaotic laser passes through a single-sideband modulator (3) and an erbium-doped fiber amplifier (4) in sequence, and is then divided into a detection light and a differential reference light through a second beam splitter (7); the detection light is incident on one end of a sensing fiber (14), and the differential reference light is detected by a second photodetector (16); the second chaotic laser passes through an optical delay line (9) and a semiconductor optical amplifier (10) in sequence, and is then divided into a pump light and a cross-correlation reference light through a third beam splitter (11); the pump light is optically amplified by a pulse optical amplifier (12), and is then injected from the other end of the sensing fiber (14) through a first optical circulator (13), and the cross-correlation reference light is detected by a third photodetector (17); the transmission signal in the sensing fiber (14) is output by the first optical circulator (13), and is then detected by the first photodetector (15); The single sideband modulator (3) is used to modulate the first chaotic laser so that it produces a frequency downshift, and the downshift amount is equal to the Brillouin frequency shift amount in the sensing optical fiber; the erbium-doped optical fiber amplifier (4) is used to amplify the first chaotic laser after the frequency downshift; the optical delay line (9) is used to adjust the delay of the second chaotic laser, and the semiconductor optical amplifier (10) is used to modulate the continuous second chaotic laser into pulsed chaotic light; The three detection signals are synchronously collected by a data collection unit (18) and sent to a computer (19) for data processing.

2. A gain differential measurement type high performance chaotic Brillouin sensor device according to claim 1, characterized in that: The specific method of data processing by computer (19) is: Performing a cross-correlation operation on the transmission signal detected by the first photodetector (15) and the differential reference signal detected by the second photodetector (16) to obtain an optical path difference between the two signals; Then, the transmission signal and the differential reference signal are matched with an optical path difference, and then a differential operation is performed on the transmission signal after the optical path difference matching and the differential reference signal to obtain chaotic Brillouin gain information; The obtained chaotic Brillouin gain information is cross-correlated with the cross-correlation reference signal detected by the third photodetector (17) to achieve the location of the correlation peak.

3. A gain differential measurement type high performance chaotic Brillouin sensor device according to claim 1, characterized in that: The chaotic laser source (1) comprises a laser (20), an optical fiber ring oscillator (22) and a feedback loop; the laser light emitted by the laser (20) is incident on the feedback loop via the optical fiber ring oscillator (22); the feedback loop is used to sequentially feed back the incident laser light portion to the optical fiber ring oscillator (22) and the laser (20), so that the laser (20) outputs chaotic laser light; the chaotic laser light output by the laser (20) is output after passing through the optical fiber ring oscillator (22) and the feedback loop; and the optical fiber ring oscillator (22) is used to raise the low-frequency energy in the chaotic laser light output by the laser (20).

4. A gain differential measurement type high performance chaotic Brillouin sensor device according to claim 3, characterized in that: The feedback loop comprises a second optical circulator (23), a fourth beam splitter (24), a polarization controller (27), and an attenuator (28); the chaotic laser source (1) also comprises a first optical isolator (25); The laser light emitted by the laser (20) passes through the optical fiber ring oscillator (22) and the second optical circulator (23), and is then split into two beams by the fourth beam splitter (24), one of which passes through an attenuator (28) and a polarization controller (27) and returns to the second optical circulator (23), and then passes through the second optical circulator (23) and the optical fiber ring oscillator (22) and returns to the laser (20), so that the laser outputs a chaotic laser whose low-frequency energy is raised, and the chaotic laser passes through the optical fiber ring oscillator (22), the fourth beam splitter (24) and the first optical isolator (25) and is then output.

5. A gain differential measurement type high performance chaotic Brillouin sensor device according to claim 4, characterized in that: The chaotic laser source (1) further comprises a fifth beam splitter (21) and a power meter (26); the fifth beam splitter (21) is arranged between the laser (20) and the optical fiber ring oscillator (22), an input end of which is connected to the optical fiber ring oscillator (22), one output end of which is connected to the laser (20), and another output end of which is connected to the power meter (26); the power meter (26) is used to monitor the light intensity returning to the laser (20).

6. A gain differential measurement type high performance chaotic Brillouin sensor device according to claim 1, characterized in that: It also includes a light polarization scrambler (5) and a second light isolator (6), wherein the light polarization scrambler (5) and the second light isolator (6) are arranged between the erbium-doped fiber amplifier (4) and the second beam splitter (7); the light polarization scrambler (5) is used to reduce the polarization sensitivity of the first chaotic laser, and the second light isolator (6) is used to isolate stray light output from one end of the sensing optical fiber (14).

7. The gain differential measurement type high performance chaotic Brillouin sensor device according to claim 1, characterized in that: The first beam splitter (2), the second beam splitter (7) and the third beam splitter (11) are 1×2 optical fiber couplers; the output end of the chaotic laser source (1) is connected to the input end of the first beam splitter (2) via a single-mode optical fiber jumper; the first output end of the first beam splitter (2) is connected to the input end of the single-sideband modulator (3) via a single-mode optical fiber jumper; the output end of the single-sideband modulator (3) is connected to the input end of the erbium-doped optical fiber amplifier (4) via a single-mode optical fiber jumper; the output end of the erbium-doped optical fiber amplifier (4) is connected to the input end of the erbium-doped optical fiber amplifier (4) via a single-mode optical fiber jumper; the output end of the erbium-doped optical fiber amplifier (4) is connected to the input end of the erbium-doped optical fiber amplifier (4) via a single-mode optical fiber jumper. The first end of the optical fiber (14) is connected to the input end of the optical scrambler (5) through a single-mode optical fiber jumper; the output end of the optical scrambler (5) is connected to the input end of the second optical isolator (6) through a single-mode optical fiber jumper; the output end of the second optical isolator (6) is connected to the input end of the second beam splitter (7) through a single-mode optical fiber jumper; the first output end of the second beam splitter (7) is connected to one end of the sensing optical fiber (14); the second output end of the second beam splitter (7) is connected to the input end of the second photoelectric detector (16) through a single-mode optical fiber jumper; The second output end of the first beam splitter (2) is connected to the input end of the optical delay line (9) through a single-mode optical fiber jumper; the output end of the optical delay line (9) is connected to the input end of the semiconductor optical amplifier (10) through a single-mode optical fiber jumper; the output end of the semiconductor optical amplifier (10) is connected to the input end of the third beam splitter (11) through a single-mode optical fiber jumper; the first output end of the third beam splitter (11) is connected to the input end of the pulse optical amplifier (12) through a single-mode optical fiber jumper; the output end of the pulse optical amplifier (12) is connected to the first port of the first optical circulator (13) through a single-mode optical fiber jumper; the second port of the first optical circulator (13) is connected to the other end of the sensing optical fiber (14), and the third port is connected to the input end of the first photoelectric detector (15) through a single-mode optical fiber jumper; the second output end of the third beam splitter (11) is connected to the input end of the third photoelectric detector (17) through a single-mode optical fiber jumper.

8. The gain differential measurement type high performance chaotic Brillouin sensor device according to claim 1, characterized in that: The sensing optical fiber (14) adopts G652 single-mode optical fiber or G655 single-mode optical fiber.

9. A gain differential measurement type high performance chaotic Brillouin sensing method, implemented by the device of claim 1, characterized in that: The following steps are involved: S1, causing the probe light and the pump light to undergo stimulated Brillouin amplification in the sensing optical fiber; S2, performing a cross-correlation operation on the transmission signal detected by the first photodetector (15) and the differential reference signal detected by the second photodetector (16) to obtain an optical path difference between the two signals; then performing optical path difference matching on the transmission signal and the differential reference signal, and then performing a differential operation on the transmission signal after the optical path difference matching and the differential reference signal to obtain chaotic Brillouin gain information; performing a cross-correlation operation on the obtained chaotic Brillouin gain information and the cross-correlation reference signal detected by the third photodetector (17) to locate the correlation peak; S3, adjusting the optical path of the pump light through the optical delay line (9) so that the probe light and the pump light undergo stimulated Brillouin amplification at different positions of the sensing optical fiber, and repeating step S2, thereby obtaining event information along the entire sensing optical fiber.

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