CN116839641A - High-speed chaotic Brillouin sensing device and method based on correlation method multiple access positioning - Google Patents
High-speed chaotic Brillouin sensing device and method based on correlation method multiple access positioning Download PDFInfo
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- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
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Abstract
The invention relates to the field of distributed optical fiber sensing, and discloses a high-speed chaotic Brillouin sensing device and method based on correlation method multiple access positioning, which are characterized in that a strong periodic broadband chaotic laser is divided into two beams by a first beam splitter, and one beam is used as detection light to be sequentially transmitted to a sensing optical fiber after passing through a single sideband modulator and an erbium-doped optical fiber amplifier; the other beam is divided into pumping light and reference light by an optical delay line, an erbium-doped optical fiber amplifier and a second beam splitter in sequence, and the pumping light and the detection light generate stimulated Brillouin amplification at different positions in the sensing optical fiber after passing through the optical circulator; after the signals in the sensing optical fiber are output by the optical circulator, stokes light is filtered out by the tunable optical filter and detected by the first photoelectric detector, reference light is detected by the second photoelectric detector, and the data acquisition unit acquires two paths of signals and sends the signals to the computer for data processing; the invention improves the signal-to-noise ratio of the system, widens the sensing distance and realizes the high-speed accurate positioning of a plurality of sensing points.
Description
Technical Field
The invention relates to the field of distributed optical fiber sensing, in particular to a high-speed chaotic Brillouin sensing device and method based on correlation method multiple access positioning.
Background
At present, the distributed optical fiber sensing technology has become a new generation sensor for the competitive development of various countries because of the large measurement range, electromagnetic interference resistance, multi-parameter detection and the like, and is widely applied to the field of large infrastructure safety monitoring, and has huge social benefit and national strategic value.
Distributed optical fiber sensing technology based on brillouin scattering is favored because of the realization of dual-parameter measurement of temperature and strain. The effective sensing point number, namely the ratio of the sensing distance to the spatial resolution, is a key parameter for evaluating the performance of the distributed optical fiber sensor. The spatial resolution of the brillouin optical time domain technology is limited by the difficulty in breaking through the meter scale of phonon lifetime, although researchers have proposed light source modulation techniques based on differential pulse pairs, pre-pumping pulses and the like, deconvolution, rising edge demodulation and other schemes, such as Optics Letters,2020,45 (15): 4152-4155; optics Letters 2021,46 (14): 3440-3443 to optimize spatial resolution to sub-meter levels, but still have difficulty meeting millimeter or even sub-millimeter level spatial resolution requirements prescribed in the field of transportation infrastructure and the like, with effective sensor points up to only millions [ Optics Letters 2017,42 (10): 1903-1906]. The Brillouin optical correlation domain technology excites a Brillouin acoustic wave field based on a narrow-band correlation peak, so that the limitation of phonon service life can be broken through, and the spatial resolution can reach the centimeter or even millimeter level, for example, light is shown in Science and Applications,2016,5 (2): 123-130; journal of Lightwave Technology,2019,37 (15): 3706-3712, are the focus of research for accurate positioning over long distances. To increase the number of effective sensing points, researchers have proposed techniques such as time-domain gating, double modulation schemes, differential measurement, first-order raman amplification, etc., for example Journal of Lightwave Technology,2023,41 (1): 341-346, with effective sensing points up to 200 tens of thousands. However, the increase of the effective sensing points inevitably limits the measurement speed of the system, so that real-time monitoring becomes a difficulty.
In addition, the Chinese patent application ZL202010455193.5 proposes a multi-point parallel high-speed chaotic Brillouin dynamic strain monitoring device and method, wherein a plurality of correlation peaks are measured in an optical fiber at the same time, and the sensing position is determined through pulse flight time, so that multi-point parallel monitoring is finally realized. However, the method needs to modulate continuous light into pulse light by using a high-priced pulse modulator, so that the power of the pulse light cannot be too high to avoid nonlinear effect, certain loss exists when the pulse light is transmitted in the optical fiber, the loss of the pulse light energy is serious along with the increase of the sensing distance, and the intensity noise of chaotic light further causes the Brillouin gain signal at the tail end of the optical fiber to be extremely weak and difficult to identify. Even if identifiable, the gain signal is too weak, the signal to noise ratio is extremely low, accurate positioning cannot be realized, the sensing distance is further limited, and the improvement of the effective sensing point number is restricted. Meanwhile, after the continuous light is modulated into pulse light, only a high level part of the pulse acts on the detection path. In order to improve the intensity of the two paths of light effects, the pulse width cannot be too small, so that only one relevant peak exists in the range of the pulse width, and therefore, the rest positions in the range and the positions corresponding to the low level of the pulse still need to be subjected to distributed measurement by adjusting the light delay line, and the scanning speed is still limited.
Therefore, a brillouin distributed optical fiber sensing monitoring technology for demodulating mass sensing points at high speed is required to meet the requirement of real-time monitoring.
Disclosure of Invention
The invention provides a high-speed chaotic Brillouin sensing device and method based on correlation method multiple access positioning, which aims to meet the current application requirement of realizing rapid real-time monitoring of mass sensing points of distributed optical fiber sensing.
In order to solve the technical problems, the invention adopts the following technical scheme: a high-speed chaotic brillouin sensing device based on correlation method multiple access positioning, comprising: the high-correlation time domain self-synchronization chaotic laser source is used for outputting strong-period broadband chaotic laser, the strong-period broadband chaotic laser is divided into two beams by the first optical splitter, one beam is used as detection light and sequentially subjected to optical frequency downshifting by the single-sideband modulator, and the first erbium-doped optical fiber amplifier is used for amplifying light and then is incident to one end of the sensing optical fiber; the other beam sequentially passes through an optical delay line and a second erbium-doped optical fiber amplifier, is divided into pumping light and reference light by a second light splitter, and enters from the other end of the sensing optical fiber after passing through an optical circulator to meet the detection light at different positions in the sensing optical fiber and generate stimulated Brillouin amplification; after the signals in the sensing optical fiber are output by the optical circulator, stokes light is filtered out by the tunable optical filter and detected by the first photoelectric detector, the reference light is detected by the second photoelectric detector, and two paths of detection signals are simultaneously collected by the data collection unit and sent to the computer for data processing;
the single sideband modulator is used for carrying out single sideband modulation on the detection light so that the frequency difference between the detection light and the pumping light is the Brillouin frequency shift quantity; the optical delay line is used for adjusting the optical path length of the pump light so that the probe light and the pump light meet at different positions in the sensing optical fiber.
Preferably, the strong periodic broadband chaotic laser is a strong periodic broadband chaotic laser with a correlation coefficient greater than 0.9.
Preferably, the high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning further comprises an optical scrambler and an optical isolator, wherein the optical scrambler and the optical isolator are arranged between the first erbium-doped optical fiber amplifier and one end of the sensing optical fiber; the optical disturbance polarizer is used for reducing the polarization sensitivity of the detection light, and the optical isolator is used for isolating stray light output by one end of the sensing optical fiber.
Preferably, the first optical splitter and the second optical splitter are 1×2 optical fiber couplers, and the output end of the high-correlation time domain self-synchronizing chaotic laser source is connected with the input end of the first optical splitter through a single-mode optical fiber jumper; the first output end of the first optical splitter is connected with 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 with the input end of the first erbium-doped optical fiber amplifier through a single mode optical fiber jumper; the output end of the first erbium-doped fiber amplifier is connected with the input end of the optical scrambler through a single-mode fiber jumper; the output end of the optical scrambler is connected with the input end of the optical isolator through a single-mode fiber jumper; the output end of the optical isolator is connected with one end of the sensing optical fiber;
the second output end of the first optical splitter is connected with 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 with the input end of the second erbium-doped optical fiber amplifier through a single-mode optical fiber jumper; the output end of the second erbium-doped fiber amplifier is connected with the input end of the second optical splitter through a single-mode fiber jumper; the first output end of the second optical splitter is connected with the first port end of the optical circulator through a single-mode fiber jumper; the second port of the optical circulator is connected with the other end of the sensing optical fiber, and the third port is connected with the input end of the tunable optical filter through a single-mode optical fiber jumper; the output end of the tunable optical filter is connected with the input end of the photoelectric detector through a single-mode optical fiber jumper, and the second output end of the second optical splitter is connected with the input end of the photoelectric detector through the single-mode optical fiber jumper.
Preferably, the high-speed chaotic brillouin sensing device based on correlation method multiple access positioning further comprises a broadband microwave signal source, wherein the broadband microwave signal source is used for driving the single sideband modulator, and the broadband microwave signal source is connected with the data acquisition unit.
Preferably, the high-correlation time domain self-synchronizing chaotic laser source is used for outputting strong periodic broadband chaotic laser with the spectral bandwidth of-3 dB being larger than 5GHz and the power bandwidth of-3 dB being larger than 10 GHz.
Preferably, the sensing optical fiber adopts a G652 single mode optical fiber or a G655 single mode optical fiber.
Preferably, the specific method for the computer to process the data is as follows: and carrying out cross-correlation operation on the sensing signal detected by the first photoelectric detector and the reference signal detected by the second photoelectric detector to obtain time delay values corresponding to each correlation peak in a cross-correlation curve, and realizing multiple access positioning and demodulation through each time delay value and each correlation peak and peak value.
In addition, the invention also provides a high-speed chaotic Brillouin sensing method based on the correlation method multiple access positioning, which is realized by adopting the device and comprises the following steps:
s1, enabling the detection light and the pumping light to generate stimulated Brillouin amplification in a sensor optical fiber;
s2, synchronously acquiring a chaotic Stokes optical signal and a reference signal which are output in a sensing optical fiber, performing correlation processing on the acquired chaotic Stokes optical signal and the reference path signal, and demodulating to obtain Brillouin gain signals at a plurality of positions;
s3, adjusting the optical path of the pump light through the delay line, enabling the detection light and the pump light to generate stimulated Brillouin amplification effect at different positions of the sensing optical fiber, repeating the step S2, and realizing scanning of multiple correlation peaks along the sensing optical fiber, so that event information along the whole sensing optical fiber is obtained.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a high-speed chaotic Brillouin sensing device and method based on correlation method multiple access positioning, which adopts strong periodic broadband chaotic laser with high correlation time domain self-synchronization characteristic as a light source, so that the strong periodic broadband chaotic laser is excited at highly correlated positions in optical fibers to generate a plurality of correlation peaks, the intensity noise characteristic of the chaotic laser is fully utilized, chaotic reference light and detection light with Brillouin gain are subjected to correlation processing, and the positions of all sensing points are determined according to correlated time delay information; the high-speed distributed measurement can be realized by adjusting the high-precision delay line to sweep the correlation peak through the interval between adjacent correlation peaks, and the measurement speed of the system is greatly improved. In addition, the autocorrelation curve of the strong periodic chaotic laser has extremely high peak side lobe ratio, and the larger the oscillation amplitude of the chaotic signal is, the higher the peak side lobe ratio is, so that the signal detection with high signal-to-noise ratio can be realized. Therefore, the invention not only can simultaneously identify a plurality of related peaks in the optical fiber, but also can accurately identify weak Brillouin gain signals in a long-distance microscale event zone, thereby realizing distributed sensing with long distance and high speed measurement.
2. The invention adopts the strong periodic broadband chaotic laser as a light source, has the characteristic of high correlation time domain self-synchronization, and is excited in the optical fiber to generate a plurality of correlation peaks, and the interval of the correlation peaks is determined by the period of the light source. The positions of the correlation peaks are moved for multiple times to realize full-distributed measurement, and the scanning times are determined by the intervals of the correlation peaks and are irrelevant to the length of the optical fiber, so that the invention can meet the application requirements of long-distance high-speed real-time monitoring.
3. Compared with the brillouin optical correlation domain analysis technology based on sinusoidal modulation and time domain data processing, the method has the advantages that the interval of correlation peaks is determined by the period of a light source, the movement of the correlation peaks is realized by adjusting a high-precision delay line, the offset of the positions of the correlation peaks is always constant, and the linear uniform full-coverage distributed measurement can be realized. Meanwhile, the spatial resolution of the system is only determined by the line width of the light source, no operation is applied to the light source in the whole measuring process, and the line width of the light source is unchanged all the time, so that the spatial resolution of the system is a constant value, and the high-speed accurate positioning of multiple sensing points can be realized.
4. Compared with a multi-point parallel high-speed chaotic Brillouin dynamic strain monitoring device and method (Chinese patent application ZL 202010455193.5), the invention does not need to additionally modulate optical pulse for positioning, but fully utilizes the intensity noise characteristic of chaotic laser, performs multi-point positioning according to time delay information after correlation operation, and the larger the intensity fluctuation is, the higher the signal-to-noise ratio of a signal obtained after correlation processing is. Therefore, weak gain at the tail end of the long-distance optical fiber can be accurately identified by performing cross-correlation processing on the strong-period broadband chaotic laser and the detection light with the Brillouin gain, and the signal-to-noise ratio of the system is improved. Meanwhile, in the multi-point parallel high-speed chaotic Brillouin dynamic strain monitoring device and method, continuous light is modulated into pulse light, and the correlation between the pulse pumping light and continuous detection light is inevitably reduced, so that stimulated Brillouin gain is weakened. The invention does not adopt a pulse light modulator, ensures strong correlation of two paths of optical signals, has larger strength of the excited acoustic wave field, can obtain stronger gain signals, improves the signal-to-noise ratio of the system, widens the sensing distance and further improves the effective sensing point number.
5. Compared with a Brillouin distributed optical fiber sensing device and a Brillouin distributed optical fiber sensing method which are positioned by a chaos correlation method (Chinese patent application ZL 201610305960.8), detection light with Brillouin gain is obtained, rayleigh scattered light and Stokes light frequency sidebands of the detection light are filtered out respectively through two filters, a position signal of the optical fiber temperature or strain is determined by calculating a correlation function between a pumping light backward Rayleigh scattered signal and a reference signal, and meanwhile, the Brillouin gain spectrum of the optical fiber is determined by calculating the relation between the power of the detection light sideband signal and the modulation frequency, so that the temperature or strain value at any position of the optical fiber is obtained. According to the method, two filters are not required to be used for filtering respectively, the obtained detection light with the Brillouin gain is directly subjected to cross-correlation processing with the chaotic reference signal, and the positions of a plurality of correlation peaks can be determined according to different delays of different positions. If a certain correlation peak has temperature or stress variation, the magnitude of the correlation peak is fluctuated compared with the correlation peaks of other non-event areas; and by extracting the frequency information of the Brillouin gain spectrum, the accurate temperature or strain value can be obtained, the cost is saved, the data acquisition process is simplified, and the measurement speed is improved.
In summary, the invention adopts the chaos correlation method to replace the pulse flight method to realize the synchronous positioning of any plurality of sensing points in the optical fiber, makes full use of the intensity noise characteristic of the chaos laser, carries out multi-point positioning according to time delay information after correlation operation, and the higher the intensity fluctuation is, the higher the signal-to-noise ratio of the signal obtained after correlation processing is, can accurately identify the weak Brillouin gain signal at the tail end of the optical fiber, improves the signal-to-noise ratio of the system, further widens the sensing distance, and realizes the high-speed accurate positioning of a plurality of sensing points.
Drawings
Fig. 1 is a schematic structural diagram of a high-speed chaotic brillouin sensing device based on correlation method multiple access positioning according to a first embodiment of the present invention;
FIG. 2 is a timing chart (a) of a strong periodic chaotic laser output by a medium-high correlation time domain self-synchronizing chaotic laser source and a correlation curve (b) thereof according to an embodiment of the present invention;
FIG. 3 is a signal-to-noise ratio of a strong periodic chaotic laser signal with different peak-to-peak oscillation amplitudes after correlation operation, wherein (a) is a timing chart of the strong periodic chaotic laser signal with a peak-to-peak value of 12mV, (b) is a correlation curve corresponding to (a), (c) is a timing chart of the strong periodic chaotic laser signal with a peak-to-peak value of 60mV, and (d) is a correlation curve corresponding to (c);
fig. 4 is a schematic structural diagram of a high-speed chaotic brillouin sensing device based on correlation method multiple access positioning according to a second embodiment of the present invention;
in the figure: the high correlation time domain self-synchronizing chaotic laser source comprises a 1-high correlation time domain self-synchronizing chaotic laser source, a 2-first optical splitter, a 3-single sideband modulator, a 4-first erbium-doped optical fiber amplifier, a 5-optical scrambler, a 6-optical isolator, a 7-broadband microwave signal source, an 8-optical delay line, a 9-second erbium-doped optical fiber amplifier, a 10-second optical splitter, a 11-optical circulator, a 12-sensing optical fiber, a 13-tunable optical filter, a 14-first photoelectric detector, a 15-second photoelectric detector, a 16-data acquisition unit and a 17-computer.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
As shown in fig. 1, a first embodiment of the present invention provides a high-speed chaotic brillouin sensing device based on correlation method multiple access positioning, which includes: the high-correlation time domain self-synchronization chaotic laser source 1 is used for outputting strong-period broadband chaotic laser, the strong-period broadband chaotic laser is divided into two beams by the first optical splitter 2, one beam is used as detection light and sequentially subjected to optical frequency downshifting by the single-sideband modulator 3, and the first erbium-doped optical fiber amplifier 4 is used for amplifying light and then is incident to one end of the sensing optical fiber 12; the other beam sequentially passes through an optical delay line 8 and a second erbium-doped optical fiber amplifier 9, is divided into pumping light and reference light by a second optical splitter 10, and the pumping light enters from the other end of the sensing optical fiber 12 after passing through an optical circulator 11 and meets the detection light at different positions in the sensing optical fiber to generate stimulated Brillouin amplification; after the signals in the sensing optical fiber 12 are output by the optical circulator 11, stokes light is filtered out by the tunable optical filter 13 and detected by the first photoelectric detector 14, reference light is detected by the second photoelectric detector 15, and two paths of detection signals are simultaneously collected by the data collection unit 16 and then sent to the computer 17 for data processing; the single sideband modulator 3 is configured to perform single sideband modulation on the probe light, so that a frequency difference between the single sideband modulator and the pump light is a brillouin frequency shift amount; the optical delay line 8 is used for adjusting the optical path of the pump light. The optical delay line 8 is a high-precision optical delay line. The optical delay line used in this embodiment has a delay range of 169mm, a delay accuracy of 0.3um, and a delay step of 0.001mm.
Further, the strong periodic broadband chaotic laser is broadband chaotic laser with a correlation coefficient larger than 0.9, and the time sequence signal is periodic rectangular pulse. Specifically, when the output chaotic laser is a periodic light source, the output chaotic laser appears as periodic rectangular light pulses in time sequence, and the cross correlation coefficient is greater than 0.9, the laser source can be regarded as a high-correlation time domain self-synchronizing chaotic laser source.
Further, the high-correlation time domain self-synchronizing chaotic laser source 1 is used for outputting strong periodic broadband chaotic laser with the spectral line width of-3 dB being larger than 5GHz and the power band width of-3 dB being larger than 10GHz, the duty ratio of the strong periodic broadband chaotic laser is larger than 85 percent, the cross correlation coefficient of the periodic oscillating chaotic laser is larger than 0.9, and the peak-to-peak value of the signal is larger than 100mV; the optical circulator 11 is a high peak power optical circulator compatible with pulse optical transmission, the first photoelectric detector 14 and the second photoelectric detector 15 are low-noise high-sensitivity detectors, and the sensing optical fiber 12 adopts a G652 single-mode optical fiber or a G655 single-mode optical fiber. In addition, in this embodiment, the timing signal of the chaotic laser output by the high correlation time domain self-synchronizing chaotic laser source 1 is a periodic rectangular pulse, the chaotic signal of the high level part of the pulse is randomly oscillated, and the self-correlation curve shows a strong periodicity, as shown in fig. 2.
Specifically, in this embodiment, the strong periodic broadband chaotic laser output by the high-correlation time domain self-synchronizing chaotic laser source 1 may be generated by modulating an electric chaotic signal, or may also regulate and control the feedback light intensity through an electric absorption modulator, so as to realize the switching between the chaotic laser and the steady-state laser, and further output multiple sections of high-correlation chaotic laser oscillation, so that the cross correlation coefficient is greater than 0.9.
Further, the first optical splitter 2 and the second optical splitter 11 are 1×2 optical fiber couplers, and the output end of the high-correlation time domain self-synchronizing chaotic laser source 1 is connected with the input end of the first optical splitter 2 through a single-mode optical fiber jumper; the first output end of the first optical splitter 2 is connected with the input end of the single-sideband modulator 3 through a single-mode optical fiber jumper; the output end of the single sideband modulator 3 is connected with the input end of the first erbium-doped optical fiber amplifier 4 through a single mode optical fiber jumper; the output end of the first erbium-doped fiber amplifier 4 is connected with the input end of the optical scrambler 5 through a single-mode fiber jumper; the output end of the optical scrambler 5 is connected with the input end of the optical isolator 6 through a single-mode fiber jumper; the output end of the optical isolator 6 is connected with one end of the sensing optical fiber 12;
the second output end of the first optical splitter 2 is connected with the input end of the optical delay line 8 through a single-mode optical fiber jumper; the output end of the optical delay line 8 is connected with the input end of the second erbium-doped optical fiber amplifier 9 through a single-mode optical fiber jumper; the output end of the second erbium-doped fiber amplifier 9 is connected with the input end of the second beam splitter 11 through a single-mode fiber jumper; the first output end of the second optical splitter 11 is connected with the first port end of the optical circulator 11 through a single-mode fiber jumper; the second port of the optical circulator 11 is connected with the other end of the sensing optical fiber 12, and the third port is connected with the input end of the tunable optical filter 13 through a single-mode optical fiber jumper; the output end of the tunable optical filter 13 is connected with the input end of the photoelectric detector 14 through a single-mode optical fiber jumper, and the second output end of the second optical splitter 11 is connected with the input end of the photoelectric detector 15 through a single-mode optical fiber jumper.
Specifically, in this embodiment, the specific method for performing data processing by the computer 17 is as follows:
and performing cross-correlation operation on the sensing signal detected by the first photoelectric detector 14 and the reference signal detected by the second photoelectric detector 15 to obtain delay values corresponding to each correlation peak in a cross-correlation curve, and realizing multiple access positioning and demodulation through each delay value and each correlation peak-to-peak value.
Further, the high-speed chaotic brillouin sensing device based on correlation method multiple access positioning is characterized by further comprising a broadband microwave signal source 7, wherein the broadband microwave signal source 7 is used for driving the single-sideband modulator 3, and the broadband microwave signal source 7 is connected with the data acquisition unit 16.
The working principle of the embodiment of the invention is as follows.
1. The output center wavelength of the high-correlation time domain self-synchronizing chaotic laser source 1 is 1550nm, the time sequence signal has strong periodic characteristics, the correlation coefficient is larger than 0.9, and the center frequency is v 0 -a broadband chaotic laser with a 3dB spectral bandwidth greater than 5GHz and a 3dB power spectral bandwidth greater than 10 GHz. The light output by the light source is represented by 10: the first optical splitter 2 formed by the 1×2 fiber coupler of 90 is split into two paths.
2. One path (90%) is used as detection light to be modulated by a single sideband modulator 3 to generate detection light with frequency of v 0 -ν B Wherein v B For the brillouin shift, the value is about 11GHz for a normal single mode fiber. The single sideband modulator 3 is driven by a broadband microwave signal source 7 which outputs a sinusoidal signal in the frequency range 9kHz to 13GHz and in the amplitude range-20 to 19 dBm. The modulated optical signal is amplified by using the first erbium-doped fiber amplifier 4, and the amplified optical signal is incident into the sensing fiber 12, where the sensing fiber 12 adopts a G652 single-mode fiber or a G655 single-mode fiber.
3. The other path (10%) is amplified to a proper level by a second erbium-doped fiber amplifier 9 after passing through a high-precision delay line 8 to excite the stimulated brillouin scattering effect. Then, via 1: 99% of the output of the second optical splitter 10 formed by the 1×2 fiber coupler of 99 is used as pump light, and the pump light is incident into the sensing optical fiber 12 through the optical circulator 11, meets the probe light in the sensing optical fiber 12, and generates stimulated brillouin scattering. The 1% portion output after the second beam splitter 10 is used as reference light.
4. The chaos detection light and the pumping light which are transmitted oppositely meet at a certain position in the sensing optical fiber to generate a correlation peak, multiple correlation peaks can be excited in the optical fiber due to strong periodicity of the chaos light source signal, and the stimulated Brillouin amplification effect is limited in each independent correlation peak. The detection light is filtered by an XTM-50 wavelength bandwidth adjustable filter 13, and the filtered stokes light signal is converted into an electric signal by a first photoelectric detector 14 and is input into a data acquisition unit 16 by a high-frequency coaxial cable for real-time signal acquisition. The data acquisition unit 16 acquires the stimulated brillouin amplified signal power obtained by fixing the frequency difference between the probe light and the pump light at the brillouin frequency shift by the broadband microwave source 7. The other path of light output by the second beam splitter 10 is used as a reference signal, is converted into an electric signal by the photoelectric detector 15 and is input into the data acquisition unit 16 by a high-frequency coaxial cable for real-time signal acquisition, and the filtered detection light signal is subjected to cross-correlation operation processing by the data processor 17, so that the event information along the optical fiber is accurately extracted.
5. And through correlation processing with the chaotic reference path signal, the positions of different correlation peaks are determined according to different delays, so that synchronous positioning of a plurality of correlation peaks is realized.
Set reference path signal x 1 (t) may be expressed as x 1 (t) =s (t), the filtered detection path signal x 2 (t) may be expressed as x 2 (t) =s (t-D), where D is the delay of two signals, reference is made to the signal x 1 (t) and detection path signal x 2 The cross-correlation function of (t) is:
R x1 x2 ＝E[s(t)s(t-D+τ)]＝Rss(τ-D)； (1)
wherein R is x1 x2 Representing the cross-correlation function of two signals, E representing the cross-correlation operation, when the reference signal x 1 (t) and detection path signal x 2 When the cross-correlation function of (t) takes the maximum value, rss (tau-D) also takes the maximum value, and because Rss (tau-D) is less than or equal to Rss (0), tau when the cross-correlation function takes the maximum value is time delay D. The corresponding position of the correlation peak can be positioned by performing cross-correlation operation on the two paths of signals and determining the value of the time delay D corresponding to the correlation peak of the cross-correlation function.
In this embodiment, since the timing signal is a strong periodic broadband chaotic laser with periodic rectangular pulses, the detection path signal includes a plurality of correlation peaks, so after the correlation operation processing, a plurality of delay peaks are generated, the distance between the correlation peaks can be determined according to the distance between the delay peaks, so as to realize synchronous positioning of the correlation peaks, and then, information sensing of a plurality of positioning addresses can be determined simultaneously according to the peak values of the correlation peaks.
Meanwhile, as shown in fig. 3, the greater the peak-to-peak oscillation of the chaotic laser timing sequence is, the higher the peak sidelobe noise ratio after the cross correlation processing is, and the higher the signal-to-noise ratio of the extracted signal is. Therefore, the invention can also inhibit the noise signal at the tail end of the optical fiber, extract the Brillouin gain signal of the microscale event zone at the tail end of the optical fiber, accurately identify the event point at the tail end of the optical fiber and improve the monitoring distance of distributed optical fiber sensing. Furthermore, in the invention, the scanning times of the correlation peaks are determined by the intervals of the correlation peaks, not the length of the optical fiber, and the scanning times are not increased due to the increase of the length of the sensing optical fiber, so that the system can realize real-time monitoring of long-distance high-speed sensing.
Example two
As shown in fig. 4, the embodiment of the present invention provides a high-speed chaotic brillouin sensing device based on correlation method multiple access positioning, which is the same as the first embodiment, and includes: the high correlation time domain self-synchronizing chaotic laser source 1, a first optical splitter 2, a single sideband modulator 3, a first erbium-doped fiber amplifier 4, an optical delay line 8, a second optical splitter 10 of a second erbium-doped fiber amplifier 9, an optical circulator 11, a sensing optical fiber 12, a tunable optical filter 13, a first photoelectric detector 14, a second photoelectric detector 15, a data acquisition unit 16 and a computer 17.
Unlike the first embodiment, the optical fiber amplifier further comprises an optical scrambler 5 and an optical isolator 6, wherein the optical scrambler 5 and the optical isolator 6 are sequentially arranged between the first erbium-doped fiber amplifier 4 and one end of the sensing fiber 12; the optical scrambler 5 is used for reducing the polarization sensitivity of the detection light, and the optical isolator 6 is used for isolating stray light output by one end of the sensing optical fiber 12.
Example III
The third embodiment of the invention provides a high-speed chaotic Brillouin sensing method based on correlation method multiple access positioning, which is realized by adopting the device in the first or second embodiment, and comprises the following steps:
s1, stimulated Brillouin amplification of the detection light and the pumping light occurs in the sensor optical fiber.
In the sensing device, the first beam splitter 2 divides the strong periodic broadband chaotic laser output by the high correlation time domain self-synchronizing chaotic laser source 1 into two paths, wherein one path is used as detection light; the optical frequency of the detection path is shifted downwards by the single sideband modulator 3, so that the optical frequency difference between the detection light and the pumping light is Brillouin frequency shift; the other path is divided into two beams after passing through an optical delay line 8 and a second erbium-doped optical fiber amplifier 9, one beam is used as pumping light, the pumping pulse light and the detection light after frequency shift are respectively input into a sensing optical fiber 12 from two ends, stimulated Brillouin amplification is carried out in the sensing optical fiber, and the other beam is used as reference light.
S2, synchronously acquiring a chaotic Stokes optical signal and a reference signal which are output in a sensing optical fiber, performing correlation processing on the acquired chaotic Stokes optical signal and the reference path signal, and demodulating to obtain Brillouin gain signals at a plurality of positions;
s3, adjusting the optical path of the pump light through the optical delay line, so that stimulated Brillouin amplification of the probe light and the pump light occurs at different positions of the sensing optical fiber, repeating the step S2, and scanning multiple correlation peaks along the sensing optical fiber, thereby acquiring event information along the whole sensing optical fiber.
In this embodiment, the advantage of the noise-like characteristic of the chaotic laser that the peak side lobe ratio of the autocorrelation curve is high is fully utilized, the collected data is subjected to correlation operation, the brillouin gain information of a plurality of positions is synchronously extracted, and the sensing distance can be further improved due to the high signal-to-noise ratio.
In summary, the invention uses the high-correlation time domain self-synchronizing chaotic laser to excite a plurality of correlation peaks in the optical fiber, realizes the positioning of the correlation peaks by utilizing correlation operation, and realizes the full-distributed scanning measurement of the optical fiber by adjusting the length of the high-precision optical delay line. The simultaneous measurement of a plurality of correlation peaks greatly improves the measurement speed of the system, the adjustment range of the high-precision optical delay line is only the length of the adjacent correlation peak, and the adjustment range is irrelevant to the length of the optical fiber, so that the measurement distance of the system is further improved. The measured detection optical signal and the reference path signal are subjected to cross-correlation processing, so that the signal-to-noise ratio of the obtained Brillouin gain signal can be improved, the weak Brillouin gain signal of a microscale event zone at the tail end of the optical fiber can be accurately identified, and finally, high-speed chaotic Brillouin distributed optical fiber sensing measurement of mass sensing data points is realized.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (9)
1. The high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning is characterized by comprising the following components: the high-correlation time-domain self-synchronization chaotic laser source (1), wherein the high-correlation time-domain self-synchronization chaotic laser source (1) is used for outputting strong-period broadband chaotic laser, the strong-period broadband chaotic laser is divided into two beams by the first optical splitter (2), one beam is used as detection light to sequentially undergo optical frequency downward shift by the single-sideband modulator (3), and the first erbium-doped optical fiber amplifier (4) performs optical amplification and then enters one end of the sensing optical fiber (12); the other beam sequentially passes through an optical delay line (8) and a second erbium-doped optical fiber amplifier (9), is divided into pumping light and reference light by a second light splitter (10), and the pumping light enters from the other end of the sensing optical fiber (12) after passing through an optical circulator (11) and meets the detection light at different positions in the sensing optical fiber and generates stimulated Brillouin amplification; after signals in the sensing optical fiber (12) are output by the optical circulator (11), stokes light is filtered by the tunable optical filter (13) and detected by the first photoelectric detector (14), reference light is detected by the second photoelectric detector (15), and two paths of detection signals are simultaneously collected by the data collection unit (16) and sent to the computer (17) for data processing;
the single sideband modulator (3) is used for carrying out single sideband modulation on the detection light so that the frequency difference between the detection light and the pumping light is the Brillouin frequency shift; the optical delay line (8) is used for adjusting the optical path length of the pump light so that the probe light and the pump light meet at different positions in the sensing optical fiber.
2. The high-speed chaotic brillouin sensing device based on correlation method multiple access positioning of claim 1, wherein the strong periodic broadband chaotic laser is a strong periodic broadband chaotic laser with a correlation coefficient larger than 0.9.
3. The high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning according to claim 1, further comprising an optical scrambler (5) and an optical isolator (6), wherein the optical scrambler (5) and the optical isolator (6) are arranged between the first erbium-doped fiber amplifier (4) and one end of the sensing optical fiber (12); the optical scrambler (5) is used for reducing the polarization sensitivity of the detection light, and the optical isolator (6) is used for isolating stray light output by one end of the sensing optical fiber (12).
4. The high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning according to claim 3, wherein the first optical splitter (2) and the second optical splitter (11) are 1×2 optical fiber couplers, and the output end of the high-correlation time domain self-synchronizing chaotic laser source (1) is connected with the input end of the first optical splitter (2) through a single-mode optical fiber jumper; the first output end of the first optical splitter (2) is connected with the input end of the single-sideband modulator (3) through a single-mode optical fiber jumper; the output end of the single sideband modulator (3) is connected with the input end of the first erbium-doped fiber amplifier (4) through a single mode fiber jumper; the output end of the first erbium-doped fiber amplifier (4) is connected with the input end of the optical scrambler (5) through a single-mode fiber jumper; the output end of the optical scrambler (5) is connected with the input end of the optical isolator (6) through a single-mode fiber jumper; the output end of the optical isolator (6) is connected with one end of the sensing optical fiber (12);
the second output end of the first optical splitter (2) is connected with the input end of the optical delay line (8) through a single-mode optical fiber jumper; the output end of the optical delay line (8) is connected with the input end of the second erbium-doped fiber amplifier (9) through a single-mode fiber jumper; the output end of the second erbium-doped fiber amplifier (9) is connected with the input end of the second optical splitter (11) through a single-mode fiber jumper; the first output end of the second optical splitter (11) is connected with the first port end of the optical circulator (11) through a single-mode optical fiber jumper; the second port of the optical circulator (11) is connected with the other end of the sensing optical fiber (12), and the third port is connected with the input end of the tunable optical filter (13) through a single-mode optical fiber jumper; the output end of the tunable optical filter (13) is connected with the input end of the photoelectric detector (14) through a single-mode optical fiber jumper, and the second output end of the second optical splitter (11) is connected with the input end of the photoelectric detector (15) through a single-mode optical fiber jumper.
5. A high-speed chaotic brillouin sensing device based on correlation method multiple access positioning according to claim 1, further comprising a broadband microwave signal source (7), wherein the broadband microwave signal source (7) is used for driving the single sideband modulator (3), and the broadband microwave signal source (7) is connected with the data acquisition unit (16).
6. The high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning of claim 1, wherein the high-correlation time domain self-synchronizing chaotic laser source (1) is used for outputting a strong periodic broadband chaotic laser with a 3dB spectral bandwidth being larger than 5GHz and a 3dB power spectral bandwidth being larger than 10 GHz.
7. The high-speed chaotic Brillouin sensing device based on correlation method multiple access positioning according to claim 1, wherein the sensing optical fiber (13) adopts a G652 single mode optical fiber or a G655 single mode optical fiber.
8. The high-speed chaotic brillouin sensing device based on correlation method multiple access positioning according to claim 1, wherein the specific method for data processing by the computer (17) is as follows:
and carrying out cross-correlation operation on the sensing signal detected by the first photoelectric detector (14) and the reference signal detected by the second photoelectric detector (15) to obtain delay values corresponding to each correlation peak in a cross-correlation curve, and realizing multiple access positioning and demodulation through each delay value and each correlation peak-to-peak value.
9. The high-speed chaotic Brillouin sensing method based on correlation method multiple access positioning is realized by adopting the device as claimed in claim 1, and is characterized by comprising the following steps:
s1, enabling the detection light and the pumping light to generate stimulated Brillouin amplification in a sensor optical fiber;
s2, synchronously acquiring a chaotic Stokes optical signal and a reference signal which are output in a sensing optical fiber, performing correlation processing on the acquired chaotic Stokes optical signal and the reference path signal, and demodulating to obtain Brillouin gain signals at a plurality of positions;
s3, adjusting the optical path of the pump light through the optical delay line, so that stimulated Brillouin amplification of the probe light and the pump light occurs at different positions of the sensing optical fiber, repeating the step S2, and scanning multiple correlation peaks along the sensing optical fiber, thereby acquiring event information along the whole sensing optical fiber.
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