CN111307054B - High-precision dynamic strain monitoring device and method based on time-delay-free chaotic laser - Google Patents
High-precision dynamic strain monitoring device and method based on time-delay-free chaotic laser Download PDFInfo
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Abstract
The invention relates to the field of distributed optical fiber sensing, and discloses a high-precision dynamic strain monitoring device and method based on non-time-delay chaotic laser. The chaotic Brillouin gain spectrum bimodal effect is eliminated by using the non-delay broadband chaotic laser, and the dynamic strain measurement range is widened; the dynamic strain measurement precision is improved by utilizing a double-slope auxiliary technology and chaotic backward Raman scattering compensation, and the distributed optical fiber dynamic strain monitoring system with long sensing distance and high measurement precision is realized.
Description
Technical Field
The invention relates to the field of distributed optical fiber sensing, in particular to a high-precision dynamic strain monitoring device and method based on time-delay-free chaotic laser.
Background
In recent years, with the rapid development of social economy, sensing monitoring technologies such as national major facility infrastructure safety guarantee, intelligent marine environment safety guarantee, rapid identification and risk prevention and control of major geological disasters, deep detection and environmental engineering and the like are met with unprecedented development opportunities and challenges. The distributed optical fiber sensing technology is favored because of being capable of realizing long-distance, high-precision and strong anti-interference measurement of multiple parameters such as temperature, strain and the like in severe environment, and the distributed optical fiber dynamic strain monitoring technology increasingly becomes a research hotspot at present in order to meet the real-time monitoring requirement of modern monitoring networks on dynamic change parameters.
At present, the Rayleigh scattering-based phase-sensitive optical time domain reflectometry (phi-OTDR) demodulates dynamic strain at any position along an optical fiber through phase change of pulsed light backward Rayleigh signals, has a simple principle and a convenient structure, and is widely researched and applied; however, the technology is easily affected by the external environment, so that the measurement precision is poor, and meanwhile, the phi-OTDR technology is mainly used for qualitative measurement of the vibration position of the optical fiber and is difficult to accurately demodulate the strain and the frequency. Therefore, the dynamic strain measurement technology based on brillouin scattering is rapidly developed, and mainly includes: brillouin optical time domain analysis techniques based on optical agile frequency/chirp chains (a. voskoboiik,et al., Opt. Express 19, B842, 2011; D. Zhou, et al.light sci. appl. 7, 32, 2018), brillouin optical coherence domain technique based on high speed voltage controlled oscillators (y. Mizuno,et al., Light Sci. Appl. 5, e16184, 2016; B. Wang, et al.opt, Express 26, 6916, 2018), which realizes fast demodulation of gain spectrum matched with strain variation by fast scanning of detection light frequency, and has higher system complexity, contradiction between dynamic strain magnitude and frequency and low measurement accuracy; a brillouin optical time domain analysis technique based on slope assistance (y. Peled,et al.opt, Express, 21, 10697, 2013) and a dynamic strain monitoring technology (ZL 201810408414.6) based on broadband chaotic laser, which converts dynamic strain into the change of detection optical power in real time, and has the advantages of simple device, low cost and strong adaptability, however, the detection optical power is easily influenced by factors such as pumping optical power fluctuation and optical fiber loss, the monitoring distance is short, and the measurement precision is low.
In summary, the brillouin distributed optical fiber sensing technology has a very high development potential in the field of dynamic strain measurement, and a long-distance and high-precision distributed optical fiber dynamic strain monitoring technology is urgently needed.
Disclosure of Invention
The invention provides a high-precision dynamic strain monitoring device and method based on time-delay-free chaotic laser, aiming at solving the difficulty that the existing dynamic strain measurement technology cannot realize large-range real-time monitoring with long monitoring distance and high measurement precision.
In order to solve the technical problems, the invention adopts the technical scheme that: the high-precision dynamic strain monitoring method based on the non-time-delay chaotic laser comprises the following steps of:
dividing non-time-delay broadband chaotic laser output by the same laser into two beams which are respectively used as detection light and pumping light;
locking the frequency difference between the probe light and the pump light in the linear region of the rising edge slope and the falling edge slope of the Brillouin gain spectrum through double-frequency chirp sideband modulation, and then inputting the probe light and the pump light into the sensing optical fiber from two beams of the sensing optical fiber;
collecting and processing the chaotic Raman Stokes light signals output from the sensing optical fiber, and simultaneously collecting the Stokes light in the chaotic detection light which is amplified by Brillouin;
intrinsic loss and dynamic strain tension loss distribution conditions of any position along the optical fiber are demodulated in real time by processing the chaotic Raman Stokes optical signals; obtaining dynamic strain information of a specific position in the optical fiber by processing the chaotic Brillouin Stokes light, and performing power compensation by using loss distribution obtained synchronously; the programmable optical delay generator adjusts the optical path of the detection light, so that the chaotic detection light and the pump light generate stimulated Brillouin amplification at different positions of the sensing optical fiber, and dynamic strain information of any position along the optical fiber is obtained.
In addition, the invention also provides a high-precision dynamic strain monitoring device based on the non-time-delay chaotic laser, which comprises a non-time-delay broadband chaotic laser source; the non-delay broadband chaotic laser output by the non-delay broadband chaotic laser source is divided into two beams after passing through the optical splitter, and one beam serving as detection light is incident to one end of the sensing optical fiber after sequentially passing through the electro-optical modulator, the programmable optical delay generator and the continuous optical amplifier; the other beam as pumping light is sequentially incident to the first port of the optical circulator after passing through the semiconductor optical amplifier and the pulse optical amplifier, and is incident to the other end of the sensing optical fiber after being emergent from the second port of the optical circulator;
the radio frequency input end of the semiconductor optical amplifier is connected with the first output end of the pulse signal generator and used for driving the semiconductor optical amplifier to modulate the pump light into pulse light; the second output end of the pulse signal generator is connected with an external trigger port of the microwave signal source, the output end of the microwave signal source is connected with the electro-optical modulator and used for driving the electro-optical modulator to perform sideband modulation of carrier suppression on the probe light, and the sideband frequency is a dual-frequency chirp chain taking the fiber Brillouin frequency shift as the center frequency; the third output end of the pulse signal generator is connected with the radio frequency control end of the high-speed data acquisition and analysis system;
the detection light and the pumping light which are transmitted in opposite directions meet each other in the sensing optical fiber, the generated chaotic spontaneous Raman scattering Stokes light and the detection light amplified under the stimulated Brillouin scattering effect are emitted from the other end of the sensing optical fiber, then are emitted to the second port of the incident optical circulator and are emitted through the third port of the optical circulator, after an emitted signal passes through the wavelength division multiplexer, the chaotic spontaneous Raman scattering Stokes light is converted into an electric domain signal through the first photoelectric detector and then is transmitted to the high-speed data acquisition and analysis system, and after the detection light amplified under the stimulated Brillouin scattering effect is filtered by the tunable optical filter, a reserved Stokes component is converted into an electric domain signal through the second photoelectric detector and then is transmitted to the high-speed data acquisition and analysis system.
The high-precision dynamic strain monitoring device based on the time-delay-free chaotic laser further comprises a polarization controller, an optical polarization scrambler and an optical isolator, wherein the detection light is incident to one end of the sensing optical fiber after sequentially passing through the polarization controller, the electro-optic modulator, the programmable optical delay generator, the continuous optical amplifier, the optical polarization scrambler and the optical isolator.
The optical splitter is a 1 x 2 optical fiber coupler, and the non-time-delay broadband chaotic laser source, the optical splitter, the polarization controller, the high-speed electro-optical modulator, the programmable optical delay generator, the continuous optical amplifier, the optical polarization scrambler, the optical isolator, the sensing optical fiber, the semiconductor optical amplifier, the pulse signal generator, the pulse optical amplifier, the optical circulator, the wavelength division multiplexer, the first photoelectric detector, the tunable optical filter and the second photoelectric detector are connected through a single-mode optical fiber jumper.
And the high-speed data acquisition and analysis system is used for calculating strain information in the sensing optical fiber according to the signals sent by the first photoelectric detector and the second photoelectric detector.
The-3 dB spectral line width of the non-delay broadband chaotic laser output by the non-delay broadband chaotic laser source is greater than 5GHz, the-3 dB power spectral bandwidth is greater than 10GHz, and a time sequence signal has no period.
The programmable optical delay generator is used for adjusting the optical path of the detection light and realizing the continuous distributed positioning of the sensing system.
Compared with the prior art, the invention has the following beneficial effects:
compared with the existing distributed optical fiber dynamic strain measurement system, the high-precision dynamic strain monitoring device and method based on the non-delay chaotic laser have the advantages and positive effects that:
the invention relates to a high-precision dynamic strain monitoring device and method based on time-delay-free chaotic laser, which utilize time-delay-free broadband chaotic laser with-3 dB spectral line width larger than 5GHz and no period of time sequence signals as a light source, and have the main effects that: 1. the spectrum of the chaotic laser conforms to Gaussian distributionS（f) Can be represented by the formula (1) whereinf 0 Is the center frequency of the spectrum, A is the corresponding integral of the spectral area, DeltafThe spectral line width is-3 dB, and the formula shows that the optical frequencies of the chaotic probe light and the pump light are in continuous Gaussian distribution;
2. in the chaotic Brillouin optical coherence domain analysis technology, a Brillouin gain spectrum measured by the system can be represented by formula (2), whereinωIs a pump-probe light beat frequency range and has a continuous Gaussian distribution of a broadband,ρ b (ω)is the power spectral density of the beat frequency,A p in order to pump the optical power of the light,g B is the Brillouin gain center factor, Δv=v-v B For detecting the amount of optical frequency detuning, Δv B Is the intrinsic brillouin gain spectral line width, which is about 30 MHz in magnitude. The actually measured Brillouin gain spectrum represented by the formula (2) is the convolution of the intrinsic Brillouin gain of the optical fiber and a detection-pumping beat spectrum, and the broadband continuous Gaussian beat spectrum enables the chaotic Brillouin optical coherent domain analysis system to obtain an intrinsically broadened Brillouin Gain Spectrum (BGS) with the line width larger than 50 MHz;
3. the invention utilizes the long cavity feedback structure to generate broadband chaotic laser without time delay in the length of the optical fiber to be measured, and can obtain the chaotic Brillouin gain spectrum which is related to the power of the pumping light and has intrinsic broadening; meanwhile, the Brillouin gain spectrum double-peak effect in a large strain state is eliminated without time delay characteristics, the linear region of the rising edge slope and the falling edge slope of the chaotic Brillouin gain spectrum is fully utilized, and real-time monitoring of large-range dynamic strain is realized by using a slope auxiliary technology.
Secondly, a time sequence signal of the traditional chaotic laser has a weak period, namely a time delay sidelobe peak exists in an autocorrelation signal, so that a corresponding position of delay time in an optical fiber is excited to generate periodic intrinsic Brillouin gain, the gain is convoluted with a detection-pumping beat frequency spectrum to generate a Brillouin gain spectrum which is inconsistent with the frequency shift at the position of a central peak, so that the Brillouin gain spectrum measured by a system generates a double-peak effect under large strain, a linear region at a rising edge and a falling edge is damaged, and a slope auxiliary technology is greatly limited. According to the inventionA high-precision dynamic strain monitoring device and method based on non-time-delay chaotic laser are disclosed, wherein the frequency difference between probe light and pump light is locked in the ascending edge and descending edge regions of a Brillouin gain spectrum by using double-frequency chirp sideband modulation, and real-time Brillouin gain acquisition and analysis are carried out by using a photoelectric detector, which can be represented by formula (3), wherein the formula isδv= ν h -ν l ，ν l In order for the rising edge to lock onto the frequency,ν h in order for the falling edge to lock onto the frequency,G(v)is frequency ofvThe measured brillouin gain value; using the gain ratio under the double frequency chirp sidebands according to equation (3)R(δv)The influence of the power fluctuation of the pumping light on the Brillouin gain can be eliminated, and the double-slope auxiliary technology based on the influence can enable the change of the dynamic strain to be equivalent to the change of the dynamic strainR B (δv)=10 logR(δv)The linear change in the range eliminates the influence of the power fluctuation of the pump light on the measurement precision of the dynamic strain.
Thirdly, the dynamic strain is demodulated in real time by collecting the detection light power amplified by the stimulated Brillouin, however, the double-slope auxiliary technology cannot solve the detection light power fluctuation caused by the loss along the optical fiber; the method simultaneously collects and processes the chaotic Raman Stokes optical signals, reflects and collects the optical fiber loss caused by the dynamic strain position in real time, compensates the loss of the detection optical power and eliminates the dynamic strain measurement error caused by the optical fiber loss of the strain stretching area; in addition, the chaotic Raman optical time domain reflection technology formed by pulse modulated chaotic pumping light through backward Raman scattering can realize the rapid positioning of any point along the optical fiber, and the chaotic Raman optical time domain reflection technology is combined with a programmable optical delay generator to realize the rapid detection and the accurate positioning along the sensing optical fiber.
The spatial resolution of the traditional pulse type optical time domain system is limited, and the accurate positioning of a strain area is difficult to realize; the frequency agility technology, the multi-frequency modulation continuous detection light technology and the like need a plurality of high-speed electro-optical modulation modules and arbitrary waveform generators, so that the system cost is high and the modulation width is limited; the Brillouin gain spectral region of the traditional slope auxiliary method is limited in nature, the coherent detection technology is complex in structure, difficult to implement and greatly influenced by the external environment; the sensing length of the Brillouin optical time domain system is in contradiction with the sampling rate of the system, namely the dynamic strain frequency is in contradiction with the sensing distance. For example, a dynamic distributed brillouin optical fiber sensing device and method adopting a frequency agile technology (chinese patent invention, ZL 2013102334483), a long-distance distributed large-measurement-range fast response optical fiber dynamic strain sensing device adopting a multi-frequency modulation detection optical technology (chinese patent invention, ZL 2014101334620), a dynamic distributed brillouin optical fiber sensing device and method adopting a combination of slope assistance and coherent detection technology (chinese patent invention, ZL 2015101224127), and a large-dynamic-range brillouin fast measurement system adopting multi-slope assistance (chinese patent invention, 201cn910006107. x). The high-precision dynamic strain monitoring device based on the time-delay-free chaotic laser belongs to an optical coherent domain system, the spatial resolution can be improved by 2-3 orders of magnitude, and the broadband chaotic laser with-3 dB power spectrum bandwidth larger than 10GHz can realize ultrahigh spatial resolution below 4 mm; the sampling rate and the sensing distance of the chaotic Brillouin optical coherence domain system can be considered, the chaotic Brillouin gain spectrum is intrinsically widened, a complex modulation means is not needed, the system structure is simplified, the cost is reduced, and the real-time measurement of long-distance, high-spatial resolution, large range and high-frequency dynamic strain is realized.
Compared with the distributed optical fiber dynamic strain sensing device and method (ZL 201810408414.6) adopting the broadband chaotic laser in the prior art, the-3 dB spectral line width used by the invention is larger than 5GHz, the time sequence signal is not periodic, and the time delay-free broadband chaotic laser can eliminate the limitation of a Brillouin gain spectrum sub-peak to a slope linear region, continuously broaden the dynamic strain measurement range, improve the dynamic strain measurement precision by utilizing a double slope auxiliary technology and chaotic backward Raman scattering compensation, and finally realize the large-range dynamic strain real-time monitoring with both long monitoring distance and high measurement precision.
Drawings
FIG. 1 shows a schematic structural view of the apparatus of the present invention;
in the figure: the system comprises a 1-time delay-free broadband chaotic laser source, a 2-optical fiber coupler, a 3-polarization controller, a 4-electro-optical modulator, a 5-microwave signal source, a 6-programmable optical delay generator, a 7-continuous optical amplifier, an 8-optical scrambler, a 9-optical isolator, a 10-sensing optical fiber, an 11-semiconductor optical amplifier, a 12-pulse signal generator, a 13-pulse optical amplifier, a 14-optical circulator, a 15-wavelength division multiplexer, a 16-first photoelectric detector, a 17-tunable optical filter, an 18-second photoelectric detector and a 19-high-speed data acquisition and analysis system.
Fig. 2 is a schematic diagram illustrating a principle of actually measuring a brillouin gain spectrum in a chaotic brillouin optical coherence domain system, where: (a) the non-time-delay broadband chaotic laser is used as a broadened chaotic Brillouin gain spectrum measured by a light source; (b) the method is a chaos Brillouin gain spectrum bimodal effect caused by a time delay sidelobe peak.
Fig. 3 shows a schematic diagram of the dual ramp assist technique, in which: the left graph shows the lock frequency of the chirped chain-type probe light, which comprisesν l In order for the rising edge to ramp-lock the frequency,ν h for locking the frequency for the falling edge slope, the relationship is satisfiedδv= ν h -ν l (ii) a The right diagram is an example of a linear region that can be used to monitor dynamic strain under the dual ramp assist technique.
Detailed Description
In order to make the objects, 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, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, an embodiment of the present invention provides a high-precision dynamic strain monitoring device based on a non-delay chaotic laser, including a non-delay broadband chaotic laser source 1, an optical fiber coupler 2, a polarization controller 3, an electro-optical modulator 4, a microwave signal source 5, a programmable optical delay generator 6, a continuous optical amplifier 7, an optical deflector 8, an optical isolator 9, a sensing optical fiber 10, a semiconductor optical amplifier 11, a pulse signal generator 12, a pulse optical amplifier 13, an optical circulator 14, a wavelength division multiplexer 15, a first photodetector 16, a tunable optical filter 17, a second photodetector 18, and a high-speed data acquisition and analysis system 19.
The output end of the non-time-delay broadband chaotic laser source 1 is connected with the input end of the optical fiber coupler 2; the first output end of the optical fiber coupler 2 is connected with the input end of the polarization controller 3; the output end of the polarization controller 3 is connected with the optical fiber input end of the electro-optical modulator 4; the radio frequency output end of the microwave signal source 5 is connected with the radio frequency input end of the electro-optical modulator 4 through a high-frequency coaxial cable; the optical fiber output end of the electro-optical modulator 4 is connected with the input end of the programmable optical delay generator 6 through a single-mode optical fiber jumper; the output end of the programmable optical delay generator 6 is connected with the input end of the continuous optical amplifier 7 through a single-mode optical fiber jumper; the output end of the continuous optical amplifier 7 is connected with the input end of the optical polarization scrambler 8 through a single-mode optical fiber jumper; the output end of the optical polarization scrambler 8 is connected with the input end of the optical isolator 9 through a single-mode optical fiber jumper; the output end of the optical isolator 9 is connected with one end of a sensing optical fiber 10; the other end of the sensing optical fiber 10 is connected with the reflection end of the optical circulator 14; the second output end of the 1 × 2 optical fiber coupler 2 is connected with the input end of the semiconductor optical amplifier 11 through a single-mode optical fiber jumper; the radio frequency output end I of the pulse signal generator 12 is connected with the radio frequency input end of the semiconductor optical amplifier 11 through a high-frequency coaxial cable; the output end of the semiconductor optical amplifier 11 is connected with the input end of the pulse optical amplifier 13 through a single-mode optical fiber jumper: the output end of the pulse optical amplifier 13 is connected with the input end of the optical circulator 14 through a single-mode optical fiber jumper; the output end of the optical circulator 14 is connected with the input end of the 1 × 2 wavelength division multiplexer 15; a first output end of the 1 × 2 wavelength division multiplexer 15 is connected with the first photodetector 16 through a single-mode optical fiber jumper, and a second output end of the 1 × 2 wavelength division multiplexer 15 is connected with an input end of the tunable filter 17 through a single-mode optical fiber jumper; the output end of the first photoelectric detector 16 is connected with a data acquisition port I of a high-speed data acquisition and analysis system 19 through a high-frequency coaxial cable; the output end of the tunable filter 17 is connected with the input end of the second photoelectric detector 18 through a single-mode optical fiber jumper, and the output end of the second photoelectric detector 18 is connected with a data acquisition port II of the high-speed data acquisition and analysis system 19 through a high-frequency coaxial cable; the radio frequency output end II of the pulse signal generator 12 is connected with the radio frequency control port of the high-speed data acquisition and analysis system 19 through a high-frequency coaxial cable, and the radio frequency output end III of the pulse signal generator 12 is connected with the external trigger port of the microwave signal source 5 through the high-frequency coaxial cable.
Specifically, the optical fiber coupler 2 is a 1 × 2 optical fiber coupler, and is configured to divide output light of the non-time-delay broadband chaotic laser source 1 into two beams, which are respectively used as probe light and pump light. In addition, the non-delay broadband chaotic laser source 1 can be a broadband chaotic laser with a long cavity feedback structure, and the broadband chaotic laser can generate the non-delay broadband chaotic laser in the length of the optical fiber to be detected through the long cavity feedback structure, so that an intrinsically-broadened chaotic Brillouin gain spectrum related to the power of the pump light is obtained. The radio frequency output end of the pulse signal generator 12 is connected with the microwave signal source 5 and the high-speed data acquisition and analysis system 19, and synchronous trigger signal acquisition of pulse signals can be realized.
In specific implementation, the non-delay broadband chaotic laser source 1 outputs chaotic laser with the center wavelength of 1550nm, the-3 dB spectral line width of more than 5GHz, the-3 dB power spectral bandwidth of more than 10GHz and no cycle of time sequence signals. The electro-optical modulator 4 adopts a typical lithium niobate electro-optical intensity modulator with a bandwidth more than or equal to 12 GHz and a high extinction ratio. The programmable optical delay generator 5 adopts an ODG-101 high-precision long-distance programmable optical delay line. The sensing fiber 10 adopts a G652 single-mode fiber or a G655 single-mode fiber. The semiconductor optical amplifier 11 employs a gain switching series amplifier. The first photodetector 16 and the second photodetector 18 are gain type low bandwidth high speed detectors with the same performance. The tunable optical filter 17 is an XTM-50 ultra-fine bandwidth wavelength tunable filter. The high-speed data acquisition and analysis system employs a high-bandwidth, high-sampling-rate lock-in amplifier in combination with a high-performance computer.
Specifically, the wavelength division multiplexer 15 is a 1 × 2 wavelength division multiplexer, and is configured to separate the chaotic spontaneous raman scattering stokes optical signal output by the sensing optical fiber 10 through the optical circulator 14 from the chaotic probe light subjected to the laser brillouin amplification.
The working principle of the high-precision dynamic strain monitoring device based on the time-delay-free chaotic laser provided by the embodiment is as follows:
the non-delay broadband chaotic laser source 1 outputs non-delay broadband chaotic laser with-3 dB spectral line width larger than 5GHz, 3dB power spectral bandwidth larger than 10GHz and no time sequence signal periodicity, the non-delay broadband chaotic laser enters a 1 x 2 optical fiber coupler 2, and the non-delay broadband chaotic laser is divided into two paths through the 1 x 2 optical fiber coupler: one path is used as probe light, and the other path is used as pump light. As shown in fig. 2, the chaos probe light and the pump light transmitted in opposite directions meet at a certain position in the sensing fiber, and a stimulated brillouin amplification effect is generated, so as to generate a stimulated brillouin gain; the broadband characteristic of the chaotic laser realizes the ultrahigh spatial resolution of millimeter magnitude, and a naturally broadened chaotic Brillouin gain spectrum is obtained; due to the non-delay characteristic of the chaotic laser, the noise Brillouin acoustic wave field in the optical fiber is greatly inhibited, so that the sensing distance is greatly expanded, and the double-peak effect of the chaotic Brillouin gain spectrum under the condition of large strain is eliminated; finally, the chaotic Brillouin gain spectral region is greatly expanded by the broadband chaotic laser without time delay, and the large-range dynamic strain real-time monitoring with long distance and high resolution is realized by utilizing a slope auxiliary technology.
The chaotic probe light is incident to a high-speed electro-optical modulator 4 through a polarization controller 3, wherein the high-speed electro-optical modulator 4 is subjected to sideband modulation of carrier suppression by a sinusoidal signal output by a microwave signal source 5, and the sideband frequency is in optical fiber Brillouin frequency shift (C)ν B 11 GHz) as the center frequency, as shown in fig. 3, low frequencyν l High frequency ofν h Brillouin gain spectral linewidth Deltaν B ，δv=ν h -ν l ≥Δν B (ii) a Using gain ratio in double frequency chirp sidebandsR(δv)Elimination of Brillouin increase caused by pumping light power fluctuationBased on the beneficial effects of the proposed dual-slope auxiliary technique, the change of dynamic strain can be equivalent to the change of dynamic strainR B (δ v)=10 logR(δv)The linear change in the range eliminates the influence of the power fluctuation of the pump light on the system and improves the measurement precision of the dynamic strain.
The optical signal after frequency shift by the high-speed electro-optical modulator 4 is input to the programmable optical delay generator 6, and the optical path of the detection light is adjusted by the programmable optical delay generator 6; then the light enters a continuous light amplifier 7, the detection light is amplified by the continuous light amplifier 7, then the light enters a polarization scrambler 8, and the polarization scrambler 8 reduces the polarization sensitivity of Brillouin gain; the light enters the optical isolator 9 after passing through the optical deflector 8, and the detection light is injected into one end of the sensing optical fiber 10 after being output by the optical isolator 9. The chaotic pumping light directly enters the semiconductor optical amplifier 11, wherein the semiconductor optical amplifier 11 is modulated by a high-speed pulse signal output by the pulse signal generator 12, the chaotic optical signal after pulse modulation enters the pulse optical amplifier 13, is amplified by the pulse optical amplifier 13 and then is output to the input end of the optical circulator 14, and is input to the other end of the optical fiber 10 to be detected through the optical circulator 14.
Chaotic probe light and pump light transmitted in opposite directions meet at a certain position in the sensing optical fiber, except stimulated Brillouin scattering, the chaotic pump light after pulse modulation is excited to generate obvious backward spontaneous chaotic Raman scattering, and the Raman scattered light and the probe light amplified by the stimulated Brillouin are circulated by an optical circulator 14 and then enter a 1 multiplied by 2 wavelength division multiplexer 15; a first output end of the wavelength division multiplexer 15 outputs chaotic spontaneous Raman scattering Stokes light, the chaotic spontaneous Raman scattering Stokes light is accessed into a first photoelectric detector 16 and converted into an electric domain signal, and the electric domain signal is transmitted to a high-speed data acquisition and analysis system 19 through a high-frequency coaxial cable via a port I; the second output end of the wavelength division multiplexer 15 outputs the chaotic probe light subjected to the brillouin amplification, the amplified probe light enters the tunable optical filter 17, only stokes light components are reserved, the filtered optical signal is accessed to the second photoelectric detector 18 to be converted into an electrical domain signal, and the electrical domain signal is transmitted to the high-speed data acquisition and analysis system 19 through the high-frequency coaxial cable via the port II.
The chaotic pumping light modulated by the pulse can form a chaotic Raman optical time domain reflectometer through backward Raman scattering, and meanwhile, chaotic Raman Stokes optical signals are collected and processed, so that loss information along the optical fiber can be demodulated in real time, the power of the detection light is compensated, and dynamic strain measurement errors caused by loss along the optical fiber are eliminated; in addition, the chaotic Raman optical time domain reflectometer can realize the quick positioning of any point along the optical fiber, and is combined with the programmable optical delay generator 6 to realize the quick detection and the accurate positioning along the sensing optical fiber.
In addition, the embodiment of the invention also provides a high-precision dynamic strain monitoring method based on the non-delay chaotic laser, which comprises the following steps:
dividing non-time-delay broadband chaotic laser output by the same laser into two beams which are respectively used as detection light and pumping light;
locking the frequency difference between the probe light and the pump light in the linear region of the rising edge slope and the falling edge slope of the Brillouin gain spectrum through double-frequency chirp sideband modulation, and then inputting the probe light and the pump light into the sensing optical fiber from two beams of the sensing optical fiber;
collecting and processing the chaotic Raman Stokes light signals output from the sensing optical fiber, and simultaneously collecting Brillouin Stokes light in the chaotic detection light which is output from the sensing optical fiber and amplified by Brillouin amplification;
intrinsic loss and dynamic strain tension loss distribution conditions of any position along the optical fiber are demodulated in real time by processing the chaotic Raman Stokes optical signals; obtaining dynamic strain information of a specific position in the optical fiber by processing the chaotic Brillouin Stokes light, and performing power compensation by using loss distribution obtained synchronously; the programmable optical delay generator adjusts the optical path of the detection light, so that the chaotic detection light and the pump light generate stimulated Brillouin amplification at different positions of the sensing optical fiber, and dynamic strain information of any position along the optical fiber is obtained.
In conclusion, the invention provides the high-precision dynamic strain monitoring method and device based on the non-delay chaotic laser, the non-delay broadband chaotic laser eliminates the double-peak effect of the chaotic Brillouin gain spectrum, the spectral region of the chaotic Brillouin gain is greatly expanded, and the real-time monitoring of the large-range dynamic strain with long distance and high resolution is realized. The double-slope auxiliary technology based on the double-frequency chirp sideband of the detection light can eliminate the influence of the power fluctuation of the pump light and improve the measurement precision of the dynamic strain. The chaotic Raman optical time domain reflection technology compensates loss information along the optical fiber in real time, eliminates dynamic strain measurement errors caused by loss along the optical fiber, and improves measurement precision of dynamic strain; and the sensor optical fiber is combined with a programmable optical delay generator to realize the rapid detection and the accurate positioning along the sensing optical fiber. Therefore, the method can eliminate the limit of the Brillouin gain spectrum secondary peak to the linear region, continuously broaden the dynamic strain measurement range, improve the dynamic strain measurement precision by utilizing the double-slope auxiliary technology and the chaotic backward Raman scattering compensation, and finally realize the large-range dynamic strain real-time monitoring with both long monitoring distance and high measurement precision.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (7)
1. The high-precision dynamic strain monitoring method based on the time-delay-free chaotic laser is characterized by comprising the following steps of:
dividing non-time-delay broadband chaotic laser output by the same laser into two beams which are respectively used as detection light and pumping light;
locking the frequency difference between the probe light and the pump light in the linear region of the rising edge slope and the falling edge slope of the Brillouin gain spectrum through double-frequency chirp sideband modulation, and then respectively inputting the probe light and the pump light into the sensing optical fiber from two ends of the sensing optical fiber;
collecting and processing the chaotic Raman Stokes light signals output from the sensing optical fiber, and collecting the Stokes light in the chaotic detection light output from the sensing optical fiber after Brillouin amplification;
intrinsic loss and dynamic strain tension loss distribution conditions of any position along the optical fiber are demodulated in real time by processing the chaotic Raman Stokes optical signals; obtaining dynamic strain information of a specific position in the optical fiber by processing the chaotic Brillouin Stokes light, and performing power compensation by using loss distribution obtained synchronously; the programmable optical delay generator adjusts the optical path of the detection light, so that the chaotic detection light and the pump light generate stimulated Brillouin amplification at different positions of the sensing optical fiber, and dynamic strain information of any position along the optical fiber is obtained.
2. The high-precision dynamic strain monitoring device based on the time-delay-free chaotic laser is characterized by comprising a time-delay-free broadband chaotic laser source (1); the time-delay-free broadband chaotic laser output by the time-delay-free broadband chaotic laser source (1) is divided into two beams after passing through a beam splitter, and one beam is used as detection light and is incident to one end of a sensing optical fiber (10) after sequentially passing through an electro-optical modulator (4), a programmable optical delay generator (6) and a continuous optical amplifier (7); the other beam as pumping light sequentially passes through the semiconductor optical amplifier (11) and the pulse optical amplifier (13) and then enters the first port of the optical circulator (14), and is emitted from the second port of the optical circulator (14) and then enters the other end of the sensing optical fiber (10);
the radio frequency input end of the semiconductor optical amplifier (11) is connected with the first output end of the pulse signal generator (12) and is used for driving the semiconductor optical amplifier (11) to modulate the pump light into pulse light; a second output end of the pulse signal generator (12) is connected with an external trigger port of a microwave signal source (5), an output end of the microwave signal source (5) is connected with the electro-optical modulator (4) and is used for driving the electro-optical modulator (4) to perform sideband modulation of carrier suppression on the probe light, and the sideband frequency is a dual-frequency chirp chain taking the fiber Brillouin frequency shift as a central frequency; the third output end of the pulse signal generator (12) is connected with the radio frequency control end of the high-speed data acquisition and analysis system (19);
the detection light and the pumping light which are transmitted in opposite directions meet in the sensing optical fiber (10), after the generated chaotic spontaneous Raman scattering Stokes light and the detection light amplified by the stimulated Brillouin scattering effect exit from the other end of the sensing optical fiber (10), the light enters the second port of the light circulator (14), is emitted out through the third port of the light circulator, and after an emitted signal passes through a wavelength division multiplexer (15), the chaotic spontaneous Raman scattering Stokes light is converted into an electric domain signal by a first photoelectric detector (16) and then transmitted to a high-speed data acquisition and analysis system (19), the detection light amplified under the action of stimulated Brillouin scattering is filtered by a tunable optical filter (17), the reserved Stokes component is converted into an electric domain signal by a second photoelectric detector (18) and then transmitted to a high-speed data acquisition and analysis system (19).
3. The high-precision dynamic strain monitoring device based on the time-delay-free chaotic laser is characterized by further comprising a polarization controller (3), an optical deflector (8) and an optical isolator (9), wherein the detection light enters one end of the sensing optical fiber (10) after sequentially passing through the polarization controller (3), the electro-optical modulator (4), the programmable optical delay generator (6), the continuous optical amplifier (7), the optical deflector (8) and the optical isolator (9).
4. The high-precision dynamic strain monitoring device based on the non-time-delay chaotic laser light is characterized in that the optical splitter is a 1 x 2 optical fiber coupler, and the non-time-delay broadband chaotic laser light source (1), the optical splitter, the polarization controller (3), the high-speed electro-optical modulator (4), the programmable optical delay generator (6), the continuous optical amplifier (7), the optical deflector (8), the optical isolator (9), the sensing optical fiber (10), the semiconductor optical amplifier (11), the pulse signal generator (12), the pulsed optical amplifier (13), the optical circulator (14), the wavelength division multiplexer (15), the first photoelectric detector (16), the tunable optical filter (17) and the second photoelectric detector (18) are connected through single-mode optical fiber jumpers.
5. The high-precision dynamic strain monitoring device based on the non-time-delay chaotic laser is characterized in that the high-speed data acquisition and analysis system (19) is used for calculating strain information in the sensing optical fiber (10) according to signals sent by the first photoelectric detector (16) and the second photoelectric detector (18).
6. The high-precision dynamic strain monitoring device based on the non-time-delay chaotic laser as claimed in claim 2, wherein the-3 dB spectral line width of the non-time-delay chaotic laser output by the non-time-delay broadband chaotic laser source (1) is greater than 5GHz, the-3 dB power spectral bandwidth is greater than 10GHz, and a time sequence signal has no period.
7. The time-delay-free chaotic laser-based high-precision dynamic strain monitoring device according to claim 2, wherein the programmable optical delay generator is used for adjusting the optical path of the probe light to realize continuous distributed positioning of the sensing system.
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