CN111141318B - Brillouin optical time domain clash type distributed optical fiber sensor - Google Patents
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- G01D5/00—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
- G01D5/26—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
- G01D5/32—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
- G01D5/34—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
- 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
- G01D5/35338—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 using other arrangements than interferometer arrangements
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- G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
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Abstract
The invention discloses a Brillouin optical time domain clash type distributed optical fiber sensor, which comprises an upper branch and a lower branch, wherein the upper branch is connected with the lower branch through a fiber cable; the continuous light of the upper branch sequentially passes through a third polarization controller, a first Mach-Zehnder modulator, a second erbium-doped fiber amplifier, a second optical circulator, an optical isolator and a fourth polarization controller, and after passing through a second optical coupler, one branch of the continuous light enters a testing optical fiber to measure dynamic physical quantity after passing through a polarizer, and the other branch of the continuous light enters a receiving end to serve as a reference for logarithmic normalization; the continuous light of the lower branch enters the test optical fiber after sequentially passing through a first polarization controller, a second Mach-Zehnder modulator, a first erbium-doped optical fiber amplifier, a second polarization controller and a first optical circulator; at a receiving end, the other path of light in the upper branch enters an oscilloscope after passing through a variable optical attenuator and a first photoelectric detector; the invention has no restriction on the length of the optical fiber to the sampling rate of the dynamic physical quantity measurement, and has good robustness to various optical fiber nonlinearity and non-local effects.
Description
Technical Field
The invention relates to a distributed optical fiber sensing technology, in particular to a Brillouin optical time domain clash type distributed optical fiber sensor.
Background
In recent years, with the rapid development of high-speed rails, large-scale infrastructure buildings, and the like, security is becoming a focus of attention of all the world, and distributed dynamic sensors are receiving more and more attention. Due to the unique advantages of the distributed optical fiber sensing technology, the distributed optical fiber sensing technology can accurately sense external information in a long-distance and severe environment. As one of the distributed optical fiber dynamic sensors, a distributed dynamic optical fiber sensor based on stimulated brillouin scattering has received extensive attention and intensive research.
At present, the brillouin dynamic optical fiber sensor mainly makes progress in shortening the brillouin gain spectrum acquisition time, reducing the curve average time, acquiring the best polarization fading elimination effect with the least average times, and the like. Thereby improving the dynamic measurement sampling rate. However, currently the research on brillouin dynamic sensors is still done over short distances, since as the length of the optical fiber increases, the pulse repetition rate must decrease to avoid crosstalk of the sensing information. In addition, as the length of the optical fiber increases, non-local effects caused by increased pumping loss seriously affect the measurement accuracy. Although reducing the probe optical power may mitigate the non-local effects, the resulting reduction in signal-to-noise ratio will result in an increase in the number of averaging and a further reduction in the dynamic measurement sampling rate.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a Brillouin optical time domain clash type distributed optical fiber sensor which can break through the limitation of the length of an optical fiber and has the capability of resisting a non-local effect.
The technical scheme adopted by the invention is as follows: a distributed optical fiber sensor of a Brillouin optical time domain clash machine type comprises an upper branch circuit and a lower branch circuit, wherein the upper branch circuit is used for generating frequency hopping probe light, and the lower branch circuit is used for generating frequency hopping pump light; continuous light output by the tunable laser is divided into an upper branch and a lower branch after passing through the first optical coupler; the continuous light of an upper branch path is injected into a 80:20 second optical coupler and then divided into two paths after sequentially passing through a third polarization controller, a first Mach-Zehnder modulator, a second erbium-doped fiber amplifier, a second optical circulator, an optical isolator and a fourth polarization controller, wherein 80% of the path of light passes through the second optical coupler and then enters a testing optical fiber to measure dynamic physical quantity after passing through a polarizer, and 20% of the path of light enters a receiving end to be used as a reference for logarithmic normalization; the continuous light of the lower branch enters the test optical fiber after sequentially passing through the first polarization controller, the second Mach-Zehnder modulator, the first erbium-doped optical fiber amplifier, the second polarization controller and the first optical circulator.
At a receiving end, 20% of light enters an oscilloscope after passing through a variable optical attenuator and a first photoelectric detector; the outlet 3 of the first optical circulator is connected with the second photoelectric detector and then is connected to the oscilloscope; the second Mach-Zehnder modulator is driven by an electric frequency hopping pulse signal generated by an arbitrary wave generator; the first Mach-Zehnder modulator is driven by a continuous high-frequency continuous electric signal generated by mixing a low-frequency-hopping continuous electric signal generated by an arbitrary wave generator and a high-frequency continuous electric signal generated by a microwave generator.
Further, the second optical circulator is connected with a fiber Bragg grating.
Further, a first low-noise electric amplifier is arranged between the arbitrary wave generator and the second mach-zehnder modulator.
Further, the low-frequency hopping continuous electric signal generated by any wave generator and the high-frequency continuous electric signal generated by the microwave generator are mixed by a mixer; a second low-noise electric amplifier is arranged between the frequency mixer and the arbitrary wave generator; and a third low-noise electric amplifier and a band-pass filter are sequentially arranged between the mixer and the first Mach-Zehnder modulator.
Further, the first mach-zehnder modulator and the second mach-zehnder modulator are operated in a carrier-suppressed double sideband modulation mode.
Based on a log normalization method of detection light bias tracking of a Brillouin optical time domain clash type distributed optical fiber sensor, the frequency modulation and hopping detection light of an upper branch is divided into two paths through a second optical coupler; one path enters a test optical fiber to acquire a dynamic temperature or strain signal and then enters a receiving end; the other path directly enters a receiving end to be used as a detection light bias reference; and dividing the two paths of signals and carrying out logarithmic normalization processing.
According to the digital feedback adjusting method based on the Brillouin optical time domain clash type distributed optical fiber sensor, the number led into the arbitrary waveform generator is reversely adjusted for multiple times according to the difference of the peak gain between frequency hopping pump optical pulses generated by the second Mach-Zehnder modulator at the previous time, and the difference of the peak gain between the optical pulses is eliminated.
The invention has the beneficial effects that:
(1) the stimulated Brillouin scattering is periodically and repeatedly generated at the specific position of the optical fiber by adopting frequency hopping detection and pumping light, and the dynamic measurement sampling rate can avoid the crosstalk of sensing information while breaking through the limitation of the length of the optical fiber;
(2) the invention can realize random adjustment of the measurement sampling rate of the dynamic physical quantity by adjusting the frequency hopping detection and the frequency hopping frequency quantity of the pumping light.
(3) The stimulated Brillouin scattering effect length is shortened, the non-local effect is effectively inhibited, and the detection light with higher power can be adopted to improve the signal-to-noise ratio and the dynamic measurement sampling rate.
(4) The sensing information can be acquired by direct detection and low-sampling-rate data acquisition equipment, so that the data volume is low and the potential real-time performance is good;
(5) the invention has good compatibility, most of the methods for improving the dynamic measurement sampling rate provided by other optical fiber sensors based on the stimulated Brillouin scattering effect can be combined with the distributed optical fiber sensor of the Brillouin optical time domain collider, thereby further improving the dynamic measurement sampling rate.
Drawings
FIG. 1 is a schematic view of the structure of the present invention.
Fig. 2 shows a result of a brillouin gain spectrum distribution test in an embodiment of the present invention; a, the logarithmic normalization method is used for Brillouin gain spectrum distribution of the existing Brillouin optical time domain analysis BOTDA sensor; b is a schematic diagram of comparison of the 100m Brillouin gain spectrum distribution of the logarithmic normalization method and the traditional logarithmic normalization method.
Fig. 3 shows the results of the brillouin gain spectrum distribution test according to the embodiment of the invention; a1 shows the Brillouin gain distribution of the 4-frequency Brillouin optical time domain collider distributed optical fiber sensor at the position of 0 to 245 m; a2 shows the Brillouin gain distribution of the 4-frequency Brillouin optical time domain collider distributed optical fiber sensor at the position of 95-350 m; a3 shows the Brillouin gain distribution of the 4-frequency Brillouin optical time domain collider distributed optical fiber sensor at 755m to 1000 m; b1 shows the Brillouin gain distribution of the 10-frequency Brillouin optical time domain collider distributed optical fiber sensor at the position of 0 to 92 m; b2 shows the Brillouin gain distribution of the 10-frequency Brillouin optical time domain collider distributed optical fiber sensor at the position of 92 to 194 m; b3 is the Brillouin gain distribution of the distributed optical fiber sensor of the 10-frequency Brillouin optical time domain collider at 908 to 1000 m.
FIG. 4 is a graph of the results of a 4-frequency and 10-frequency Brillouin optical time domain collider prestressing test at the tail end of an optical fiber according to a conventional Brillouin optical time domain analysis; a is the overall brillouin gain spectrum, and b is a partial brillouin gain spectrum enlarged view.
FIG. 5 is a diagram showing the results of dynamic strain measurements using a conventional Brillouin optical time domain analysis and 4-frequency and 10-frequency Brillouin optical time domain colliders proposed by the present invention; a is a comparative plot of the dynamic strain measured by the three methods, and b is an enlarged plot in the range of 10 to 30 μ s.
Fig. 6 is a frequency spectrum diagram corresponding to dynamic strain measured by a 4-frequency and 10-frequency brillouin optical time domain collider according to the conventional brillouin optical time domain analysis.
In the figure: 1-tunable laser, 2-first optical coupler, 3-third polarization controller, 4-first Mach-Zehnder modulator, 5-second erbium-doped fiber amplifier, 6-connection fiber Bragg grating, 7-second optical circulator, 8-optical isolator, 9-fourth polarization controller, 10-arbitrary wave generator, 11-microwave generator, 12-mixer, 13-third low-noise electrical amplifier, 14-band-pass filter, 15-second low-noise electrical amplifier, 16-first low-noise electrical amplifier, 17-second Mach-Zehnder modulator, 18-first erbium-doped fiber amplifier, 19-second polarization controller, 20-first optical circulator, 21-test fiber, 22-polarizer, 23-a second optical coupler, 24-a variable optical attenuator, 25-a first photodetector, 26-a second photodetector, 27-an oscilloscope, 28-a first polarization controller.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments.
As shown in fig. 1, a brillouin optical time domain collisional model distributed optical fiber sensor includes an upper branch for generating frequency hopping probe light and a lower branch for generating frequency hopping pump light; continuous light output by the tunable laser 1 is divided into an upper branch and a lower branch after passing through the first optical coupler 2; the continuous light of the upper branch passes through a third polarization controller 3, a first Mach-Zehnder modulator 4, a second erbium-doped fiber amplifier 5, a second optical circulator 7, an optical isolator 8 and a fourth polarization controller 9 in sequence, one branch of the continuous light passes through a polarizer 22 after passing through a second optical coupler 23 and then enters a test fiber 22 to measure dynamic physical quantity, and the other branch of the continuous light enters a receiving end to be used as a reference for logarithmic normalization; the continuous light of the lower branch enters the test optical fiber 21 after passing through a first polarization controller 28, a second Mach-Zehnder modulator 17, a first erbium-doped optical fiber amplifier 18, a second polarization controller 19 and a first optical circulator 20 in sequence; at the receiving end, the other path of light in the upper branch enters an oscilloscope 27 after passing through an adjustable optical attenuator 24 and a first photoelectric detector 25; the 3 outlet of the first optical circulator 20 is connected with a second photoelectric detector 26 and then connected to an oscilloscope 27; the second mach-zehnder modulator 17 is driven by an electrical frequency hopping pulse signal generated by the arbitrary wave generator 10; the first mach-zehnder modulator 4 is driven by a continuous high-frequency electric pulse signal generated by mixing a low-frequency hopping electric pulse generated by an arbitrary wave generator 10 and a high-frequency continuous electric signal generated by a microwave generator 11.
The second optical circulator 7 is connected to the fiber bragg grating 6.
A first low noise electrical amplifier 16 is also provided between the arbitrary wave generator 10 and the second mach-zehnder modulator 17.
The low-frequency hopping electric pulse generated by the arbitrary wave generator 10 and the high-frequency continuous electric signal generated by the microwave generator 11 are mixed by the mixer 12; a second low-noise electric amplifier 15 is arranged between the mixer 12 and the arbitrary wave generator 10; a third low-noise electric amplifier 13 and a band-pass filter 14 are provided in this order between the mixer 12 and the first mach-zehnder modulator 4.
The coupling ratio of the first optical coupler 2 is 50: 50.
The coupling ratio of the second optical coupler 23 is 80: 20.
The first mach-zehnder modulator 4 and the second mach-zehnder modulator 17 each operate in a carrier-suppressed double sideband modulation mode.
When in use, continuous light output by the tunable laser 1 is divided into two paths after passing through the first optical coupler 2 at a ratio of 50: 50; in the lower branch, the continuous light enters the second mach-zehnder modulator 17 after the polarization state of the light is adjusted by the first polarization controller 28. The mach-zehnder modulator 17, via the channel 1, enters the first low-noise electric amplifier 16 to amplify and drive the electric frequency hopping pulse signal generated by the arbitrary wave generator 10. The continuous light is then passed through a first erbium doped fiber amplifier 18 to compensate for the loss of optical power, and then through a second polarization controller 19 to adjust the polarization state of the light, which is injected into a test fiber 21 through a first optical circulator 20.
In the upper branch, the continuous light enters the first mach-zehnder modulator 4 to generate frequency-hopping probe light after the polarization state of the continuous light is adjusted by the third polarization controller 3. The continuous high-frequency electric pulse signal is generated by mixing a low-frequency hopping electric pulse generated by an arbitrary wave generator 10 and a high-frequency continuous electric signal generated by a microwave generator 11. The low-frequency hopping electric pulse generated by the arbitrary wave generator 10 enters the second low-noise electric amplifier 15 through the channel 2 and then is injected into the mixer 12; meanwhile, a high-frequency continuous electric signal generated by the microwave generator 11 is injected into the mixer 12 to be mixed with an electric signal generated by the arbitrary wave generator 10, and then the mixed signal is filtered by the third low-noise electric amplifier 13 and the band-pass filter 14 and enters the first mach-zehnder modulator 4. And then the frequency hopping detection light enters a second erbium-doped fiber amplifier 5 to compensate loss, and then enters a second optical circulator 7 and a fiber Bragg grating 6 to filter spontaneous emission noise and a frequency hopping detection light high-frequency sideband. Then, the single-sideband frequency hopping probe light is injected into a second optical coupler 23 of 80:20 after passing through an optical isolator 8 and a fourth polarization controller 9 in sequence and then is divided into two paths. Of which 80% is injected into the test fiber 21 after passing through the polarizer 22 and then into the receiving end through the first optical circulator 20. And 20% of the way goes directly to the receiving end. The frequency hopping detection light passes through the fourth polarization controller 9 and the polarizer 22, so that the polarization state of the light is aligned with a certain main shaft of the polarization maintaining fiber, and the dynamic strain measurement error caused by polarization mode interference is restrained.
At the receiving end, 20% of the light enters the first photodetector 25 after passing through the optical adjustable attenuator 24, and 80% of the light enters the second photodetector 26 through the first optical circulator 20. Both lights then enter oscilloscope 27 for analog-to-digital conversion. And finally, realizing light offset tracking log normalization by using the two received signals to eliminate Brillouin gain spectrum deformation caused by light polarization.
The continuous frequency hopping detection light and the frequency hopping pumping light pulse are transmitted oppositely, and a stimulated Brillouin scattering effect occurs in a certain area of the optical fiber. The principle analysis is as follows:
n pieces of different frequency hopping frequencies (f) in the range of optical fiber round-trip flight time (T is 2nL/c, wherein N, L and c are effective refractive index, sensing optical fiber length and light speed in vacuum respectively)1,f2,…fN) Are generated and injected into the fiber sequentially and at equal time intervals. Here, the frequency interval between any two hopping frequencies is much larger than the frequency range corresponding to the dynamic measurement range. At the same time, N have different hopping frequencies (f) within the round-trip flight time range of the optical fiber1-fs,f2-fs,…fN-fs) Is generated sequentially and at equal time intervals and injected into the optical fiber from the other end thereof. From this it can be seen that when fsIncrease in BrillouinWhen near the benefit spectrum, f1The pumping pulse will be equal to f1-fsThe detection light part generates a stimulated Brillouin scattering process in the middle of the optical fiber. At the same time, other detection light parts (i.e. frequency hopping frequency f)2-fs,…fN-fsPart of the probe light) and f1Stimulated brillouin scattering will not occur with a frequency difference between the pump pulses much larger than the brillouin gain spectral range. Likewise, f2The pump pulse will only be equal to f2-fsThe detection light part generates a stimulated Brillouin scattering process. Without partially reacting with other detected light. Therefore, as the pump pulse and the probe light are continuously transmitted, the stimulated brillouin scattering process continuously occurs in the middle region of the optical fiber. At this time, the system dynamic measurement sampling period (i.e. pulse period) can be smaller than the round-trip flight time of the optical fiber without the problem of aliasing of the sensing information between pulses. At this time, the system dynamic measurement sampling rate is no longer limited by the length of the optical fiber and is improved by N times. Meanwhile, because stimulated brillouin scattering occurs only with the corresponding probe light portion (the frequency difference between the two is in the brillouin gain spectrum range) in any pump pulse, the action length of stimulated brillouin scattering is shortened. This will effectively attenuate the pump pulse losses (losses other than the fiber's inherent losses, which accumulate as the length of the fiber increases), thereby mitigating non-local effects. Suppression of non-local effects allows higher power probe light to be employed to improve the signal-to-noise ratio and further improve the dynamic measurement sampling rate.
When the optical fiber is used, the frequency hopping frequency interval of any two adjacent frequency hopping probe lights and frequency hopping pump lights is far larger than the frequency range corresponding to the dynamic measurement range. Stimulated Brillouin scattering between the frequency hopping pump light and the frequency hopping probe light occurs continuously and periodically only in a certain specific region of the optical fiber. The frequency hopping electric signal generated by any wave generator 10 can be used for measuring the dynamic physical quantity by adopting a method of scanning or fixing the frequency hopping frequency. For frequency-sweep frequency-hopping signals, the frequency sweep needs to be larger than the dynamic measurement range. For a fixed frequency hopping signal, the frequency should be fixed in the middle of the brillouin gain spectral interval. The second mach-zehnder modulator 17 of the lower arm is driven by the frequency hopping electric signal generated by the arbitrary wave generator 10 to generate a frequency hopping pump light pulse.
The log normalization method of light offset tracking based on Brillouin light time domain clash type distributed optical fiber sensor is characterized in that frequency hopping probe light of an upper branch is divided into two paths through a second optical coupler 23; one path enters the test optical fiber 21 to acquire a dynamic temperature or strain signal and then enters a receiving end; the other path directly enters a receiving end to be used as a detection light bias reference; the two paths of signals are divided and subjected to logarithmic normalization processing, so that the Brillouin gain spectrum distortion and measurement errors caused by offset jitter of the detection light can be eliminated.
According to the digital feedback adjusting method based on the Brillouin optical time domain clash type distributed optical fiber sensor, the digital signal led into the arbitrary waveform generator 16 is reversely adjusted for multiple times according to the difference of the gains of the peak values among the frequency hopping pump optical pulses generated by the second Mach-Zehnder modulator 17 at the previous time, and the difference of the gains of the peak values among the optical pulses is supplemented. Through multiple adjustments, peak gain differences among the optical pulses are eliminated to the maximum extent, and the maximum Brillouin gain flatness is achieved.
The effects of the present invention are illustrated by the following tests.
Because the traditional Brillouin optical time domain analysis BOTDA sensor can adopt a traditional logarithmic normalization method. Therefore, the detection light offset tracking logarithm normalization method provided by the invention is used in the BOTDA to eliminate the detection light offset jitter, and the obtained brillouin gain spectrum is shown in fig. 2. It can be seen from fig. 2a that the offset jitter has been effectively eliminated. It can be seen later by comparing the brillouin gain spectra obtained by the conventional logarithmic normalization method, that the brillouin gain spectra obtained by the two methods almost coincide, as shown in fig. 2 b. Further illustrating the effectiveness of the detection light bias tracking logarithm normalization method provided by the present invention.
The detection light bias tracking logarithmic normalization method is used in the BOTDC distributed optical fiber sensor of the Brillouin optical time domain collider provided by the invention; first, experimental verification was performed for 4-frequency BOTDC. The arbitrary wave generator 10 emits 4 electrical frequency hopping pulses of different frequencies in succession every 10.2 mus. Setting the frequency coding rule and the time delay of the electric frequency hopping pulse to be 1) [1.8,2.2,1,1.4] GHz and 0 mu s respectively; 2) the collision area is 1)0 to 245m after [2.2,1,1.4,1.8] GHz, 1.5 μ s, 3) [1.4,1.8,2.2,1] GHz and 0 μ s, respectively; 2)95m to 350 m; 3)755m to 1000 m. As shown in fig. 3a1, 3a2, and 3a 3. As can be seen from the figure, the difference between the brillouin gains of peaks corresponding to 1) and different hopping frequencies is less than 0.1%, which shows that the proposed digital feedback adjustment method can effectively solve the problem of uneven brillouin gain. 2) And the sensing information corresponding to each area periodically and repeatedly appears 4 times in the range of the pulse round-trip flight time (10 mu s), which shows that the dynamic measurement sampling rate of the sensor is improved by 4 times.
The 10-frequency BOTDC is then experimentally verified, with any of the wave generators 10 sequentially emitting 10 electrical frequency-hopping pulses of different frequencies every 10.2 μ s. The frequency coding rules by setting the electrical frequency hopping pulse are respectively as follows: 1) [2.25,2.5,2.75,3,3.25,1,1.25,1.5,1.75,2] GHz; 2) [2.5,2.75,3,3.25,1,1.25,1.5,1.75,2,2.25] GHz; 3) [2,2.25,2.5,2.75,3,3.25,1,1.25,1.5,1.75] GHz (no delay). The collision areas are respectively 1)0 to 92 m; 2)92 to 194 m; 3)908 to 1000 m. As shown in fig. 3b1, 3b2, and 3b 3. As can be seen from the figure, the difference of the brillouin gains of the peaks corresponding to 1) and different hopping frequencies is about 0.1%, which shows that the proposed digital feedback adjustment method can effectively eliminate the difference of the brillouin gains. 2) And the sensing information corresponding to each area periodically and repeatedly appears 10 times in the range of the pulse round-trip flight time (10 mu s), which shows that the dynamic measurement sampling rate of the sensor is improved by 10 times. By further increasing the number of hopping frequencies, the dynamic measurement sampling rate can be further increased.
FIG. 4 is a graph showing the results of pre-stress testing at the end of the fiber using conventional BOTDA, 4-frequency and 10-frequency BOTDCs proposed by the present invention. As can be seen from fig. 4a, the brillouin gain spectra are almost identical for the three cases, illustrating that the proposed 4-frequency and 10-frequency BOTDCs have the same response as the conventional BOTDA, subject to the same strain. Fig. 4b is an enlarged view of the brillouin gain spectrum.
FIG. 5 is a graph of the results of dynamic strain measurements using conventional BOTDA, the 4-frequency and 10-frequency BOTDC of the present invention. It can be seen from the figure that by using 4-and 10-frequency BOTDC, the number of sampling points is increased by 4 and 10 times in the time range of 10.2 μ s, respectively. Compared with the dynamic measurement sampling rate of the traditional BOTDA, 4-and 10-frequency BOTDC, the dynamic measurement sampling rate is respectively improved by 4 times and 10 times.
FIG. 6 is a graph of the spectrum of dynamic strain measured using conventional BOTDA, 4-frequency and 10-frequency BOTDC as proposed by the present invention. As can be seen from the figure, the dynamic strain produced by the eccentric contains a fundamental frequency of 19.75Hz and a harmonic frequency of 39.49 Hz.
The measuring sampling rate of the sensor to the dynamic physical quantity is not limited by the length of the optical fiber any more. The random adjustment of the dynamic measurement sampling rate can be realized by adjusting the frequency hopping detection and the frequency hopping frequency quantity of the pump light. The method has good robustness to various optical fiber nonlinear and non-local effects, so that the signal-to-noise ratio can be improved by adopting strong detection light, and the dynamic measurement sampling rate can be further improved. Because the sensing information can be acquired through direct detection and low sampling rate acquisition equipment, the data volume is low, and the potential real-time performance is good. The method has good compatibility, and most of schemes for improving the dynamic measurement sampling rate provided in other optical fiber sensors based on the stimulated Brillouin scattering effect can be combined with the Brillouin optical time domain collider optical fiber distributed sensor in the invention, so that the dynamic measurement sampling rate is further improved.
Claims (7)
1. A Brillouin optical time domain clash type distributed optical fiber sensor is characterized by comprising an upper branch circuit and a lower branch circuit, wherein the upper branch circuit is used for generating frequency hopping probe light, and the lower branch circuit is used for generating frequency hopping pump light; continuous light output by the tunable laser (1) is divided into an upper branch and a lower branch after passing through the first optical coupler (2); the continuous light of an upper branch path is injected into a second optical coupler (23) of 80:20 and then divided into two paths after sequentially passing through a third polarization controller (3), a first Mach-Zehnder modulator (4), a second erbium-doped fiber amplifier (5), a second optical circulator (7), an optical isolator (8) and a fourth polarization controller (9), 80% of the light enters a testing optical fiber (21) after passing through a polarizer (22), then enters a receiving end through the first optical circulator (20), dynamic physical quantity is measured, and 20% of the light enters the receiving end to serve as reference of logarithmic normalization; the continuous light of the lower branch enters a test optical fiber (21) after sequentially passing through a first polarization controller (28), a second Mach-Zehnder modulator (17), a first erbium-doped optical fiber amplifier (18), a second polarization controller (19) and a first optical circulator (20);
at a receiving end, 20% of light enters an oscilloscope (27) after passing through a variable optical attenuator (24) and a first photoelectric detector (25); the 3 outlet of the first optical circulator (20) is connected with the second photoelectric detector (26) and then is connected with an oscilloscope (27); the second Mach-Zehnder modulator (17) is driven by an electric frequency hopping pulse signal generated by an arbitrary wave generator (10); the first Mach-Zehnder modulator (4) is driven by a continuous high-frequency electric pulse signal generated by mixing a low-frequency-hopping electric pulse generated by an arbitrary wave generator (10) and a high-frequency continuous electric signal generated by a microwave generator (11).
2. A brillouin optical time domain collider type distributed optical fiber sensor according to claim 1, characterized in that said second optical circulator (7) is connected with a fiber bragg grating (6).
3. A brillouin optical time domain bump machine type distributed optical fibre sensor in accordance with claim 1, wherein a first low noise electrical amplifier (16) is further provided between the arbitrary wave generator (10) and the second mach-zehnder modulator (17).
4. A brillouin optical time domain bump machine type distributed optical fiber sensor according to claim 1, characterized in that a low frequency hopping electric pulse generated by an arbitrary wave generator (10) and a high frequency continuous electric signal generated by a microwave generator (11) are mixed by a mixer (12); a second low-noise electric amplifier (15) is arranged between the mixer (12) and the arbitrary wave generator (10); a third low-noise electric amplifier (13) and a band-pass filter (14) are sequentially arranged between the mixer (12) and the first Mach-Zehnder modulator (4).
5. A brillouin optical time domain bump machine type distributed optical fibre sensor in accordance with claim 1, wherein the first mach-zehnder modulator (4) and the second mach-zehnder modulator (17) each operate in a carrier-suppressed double sideband modulation mode.
6. The log normalization method for the detection light bias tracking of any Brillouin optical time domain collider type distributed optical fiber sensor based on the claims 1-5 is characterized in that the frequency hopping detection light of an upper branch is divided into two paths through a second optical coupler (23); one path enters a test optical fiber (21) to acquire a dynamic temperature or strain signal and then enters a receiving end; the other path directly enters a receiving end to be used as a detection light bias reference; and dividing the two paths of signals and carrying out logarithmic normalization processing.
7. The digital feedback adjustment method for the distributed optical fiber sensor based on any one of the Brillouin optical time domain clash machines as claimed in claims 1-5, characterized in that the digital signal introduced into the arbitrary waveform generator (10) is reversely adjusted for a plurality of times according to the difference of the gains of the peaks between the frequency hopping pump optical pulses generated by the second Mach-Zehnder modulator (17) at the previous time, so as to eliminate the difference of the gains of the peaks between the optical pulses.
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9721629D0 (en) * | 1996-10-31 | 1997-12-10 | Ando Electric | Optical fiber strain-measuring apparatus |
| CN102997949A (en) * | 2012-12-18 | 2013-03-27 | 华北电力大学（保定） | Method used for measuring temperature and strain simultaneously and based on brillouin scattering |
| CN203758532U (en) * | 2014-03-31 | 2014-08-06 | 广西师范大学 | Brillouin fiber-optic sensing system |
| CN104181521A (en) * | 2014-06-24 | 2014-12-03 | 合肥工业大学 | High range resolution radar capable of emitting multifrequency carrier wave |
| CN206627111U (en) * | 2017-03-17 | 2017-11-10 | 浙江星天海洋科学技术有限公司 | High speed multibeam sounding system based on Frequency Hopping Signal |
| CN109974760A (en) * | 2019-01-24 | 2019-07-05 | 西南交通大学 | A kind of Brillouin optical time domain analysis system based on Brillouin's phase shift demodulation |
| CN109981174A (en) * | 2019-04-09 | 2019-07-05 | 中国科学院半导体研究所 | Light frequency-hopping system and transmitter based on optical circulator |
| WO2019221534A1 (en) * | 2018-05-16 | 2019-11-21 | 한국표준과학연구원 | Optical fiber bocda sensor using phase code modulation of pump light and probe light which have time difference |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5440636A (en) * | 1987-02-27 | 1995-08-08 | Lockheed Sanders, Inc. | Apparatus and method for processing of frequency hopping communications |
| US5546429A (en) * | 1992-11-09 | 1996-08-13 | Motorola, Inc. | Frequency hopping code division multiple access radio communication unit |
| CN104567960B (en) * | 2015-01-04 | 2017-04-05 | 西南交通大学 | A kind of relevant Brillouin optical time domain analysis sensor-based system that light is detected based on phase-modulation |
| IL244710B (en) * | 2015-03-22 | 2021-01-31 | Univ Ramot | Method and system for an ultimately fast frequency-scanning brillouin optical time domain analyzer |
| CN104977030B (en) * | 2015-06-04 | 2017-10-03 | 哈尔滨工业大学 | The dynamic distributed Brillouin sensing device and method of optics frequency agility technology based on any ripple of low frequency |
| CN105675032B (en) * | 2016-02-19 | 2018-04-24 | 鞍山睿科光电技术有限公司 | Real-time dynamic distributed Brillouin light fiber sensing equipment and method |
| CN106533547B (en) * | 2016-10-19 | 2018-12-18 | 全球能源互联网研究院有限公司 | Power optical fiber communication line fault monitoring device |
-
2020
- 2020-01-17 CN CN202010052952.3A patent/CN111141318B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9721629D0 (en) * | 1996-10-31 | 1997-12-10 | Ando Electric | Optical fiber strain-measuring apparatus |
| CN102997949A (en) * | 2012-12-18 | 2013-03-27 | 华北电力大学（保定） | Method used for measuring temperature and strain simultaneously and based on brillouin scattering |
| CN203758532U (en) * | 2014-03-31 | 2014-08-06 | 广西师范大学 | Brillouin fiber-optic sensing system |
| CN104181521A (en) * | 2014-06-24 | 2014-12-03 | 合肥工业大学 | High range resolution radar capable of emitting multifrequency carrier wave |
| CN206627111U (en) * | 2017-03-17 | 2017-11-10 | 浙江星天海洋科学技术有限公司 | High speed multibeam sounding system based on Frequency Hopping Signal |
| WO2019221534A1 (en) * | 2018-05-16 | 2019-11-21 | 한국표준과학연구원 | Optical fiber bocda sensor using phase code modulation of pump light and probe light which have time difference |
| CN109974760A (en) * | 2019-01-24 | 2019-07-05 | 西南交通大学 | A kind of Brillouin optical time domain analysis system based on Brillouin's phase shift demodulation |
| CN109981174A (en) * | 2019-04-09 | 2019-07-05 | 中国科学院半导体研究所 | Light frequency-hopping system and transmitter based on optical circulator |
Non-Patent Citations (3)
| Title |
|---|
| Fiber Optic Sensing for Geomechanical Monitoring: (1)-Distributed Strain Measurements of Two Sandstones under Hydrostatic Confining and Pore Pressure Conditions;Xue Ziqiu 等;《Applied Sciences》;20181231;第1-18页 * |
| 基于Simplex码的BOTDR数字相干探测技术及算法研究;郝蕴琦 等;《Laser Journal》;20181231;第65-67页 * |
| 基于受激布里渊散射效应的微波光子下变频***;*** 等;《中国激光》;20191231;第46卷(第7期);第1-6页 * |
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