CN105203136A - Distributed sensing system based on differential amplification technology - Google Patents
Distributed sensing system based on differential amplification technology Download PDFInfo
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- CN105203136A CN105203136A CN201510489467.1A CN201510489467A CN105203136A CN 105203136 A CN105203136 A CN 105203136A CN 201510489467 A CN201510489467 A CN 201510489467A CN 105203136 A CN105203136 A CN 105203136A
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Abstract
The invention discloses a distributed sensing system based on the differential amplification technology. The system is composed of an optical path detection part and a circuit demodulation part. In an optical path, two different frequencies of microwave signals are modulated to signal light, the frequency of one path of microwave signals is within the Brillouin frequency-shift frequency, and the frequency of the other path of microwave signals is slightly lower than the Brillouin frequency-shift frequency. and in a circuit, a power divider separates the two paths of signals, the separated two paths of signals are filtered and demodulated respectively, and the demodulated signals are amplified in the differential amplification manner. The signals collected by a data collection card are amplified within the specific amplitude interval by the differential amplification structure, and the problems that the range of the data collection card of a host in the distributed Brillouin time-domain analysis sensing system is limited and that the data collection precision cannot be satisfied and further the measurement accuracy of the system is reduced when the DC component is very large are solved. Devices in the system work stably, the point of temperature or stress change and the temperature or stress value can be accurately measured in multiple times of measurement.
Description
Technical field
What the present invention relates to is Distributed Optical Fiber Sensing Techniques---the demodulation techniques in distributed Brillouin's time-domain analysis sensor-based system, specifically be applied to, in a kind of distributed Brillouin's time-domain analysis sensor-based system, define a kind of distributed optical fiber sensing system based on differential amplification demodulation.
Background technology
Distributed Optical Fiber Sensing Techniques is in recent years, along with the high speed development of oil and gas pipes, high ferro, heavy construction etc., its safety is more and more subject to all circles and pays close attention to, and Distributed Optical Fiber Sensing Techniques is due to itself a large amount of advantage, under making it become long distance, rugged surroundings, carry out the gordian technique of external information perception.And Brillouin's time-domain analysis technology a member just in Distributed Optical Fiber Sensing Techniques big family, its major function is used to utilize the temperature of Brillouin shift (the optical frequency difference between Brillouin scattering and Rayleigh scattering light), strain linear susceptibility, can realize long distance, high-precision temperature and strain sensing according to the different mechanism of Brillouin scattering in optical fiber, brillouin distributed optical fiber sensing device is mainly divided into two classes: the Brillouin light domain reflectometer based on spontaneous brillouin scattering and the distributing optical fiber sensing instrument based on stimulated Brillouin scattering.Compare with spontaneous Brillouin reflectometer, in stimulated Brillouin scattering time-domain analysis system, the detection of signal is easier to, signal compared with strong, dynamic range is large, measuring accuracy is high, research worldwide drops into larger, and technology is also comparatively ripe.Brillouin's time-domain analysis system due to long distance needs to gather a large amount of data, Usage data collection card is needed to carry out data acquisition, very large DC component is had not to be removed in data, and the range of data collecting card is non-adjustable, when DC component is very large, create very large quantization error.
Summary of the invention
In view of the deficiency that data collecting card quantizing noise is larger, the signal that data collecting card collects by a kind of method that the object of this invention is to provide effective differential amplification, deducts DC component, amplifies in specific amplitude range, reduce quantizing noise, improve accuracy of measurement.
The object of the invention is to analyze and scheme proposes and realization based on following:
Based on a distributed optical fiber sensing system for differential amplification technology, be made up of light path detection and circuit demodulates two parts; Light path adopts the microwave signal of two kinds of different frequencies be modulated on flashlight: the frequency of a road microwave signal in Brillouin shift frequency (10.4-10.8GHz), the frequency comparatively Brillouin shift frequency slightly low (10GHz) of another road microwave signal; Circuit then adopts power splitter separated by two paths of signals and distinguish filtering, demodulation, then the signal after demodulation amplifies by the mode of carrying out differential amplification, realize deducting DC component, the object of lower quantization noise, its concrete structure is:
The continuous light that adjustable distributed feedback laser 1 exports is divided into two-way after photo-coupler 2, and a route acousto-optic modulator 3 enters into Erbium-Doped Fiber Amplifier (EDFA) 4 after modulating and amplifies, and enters optical circulator 11 through optical filter 5 filtering; Another Lu Guangjing Polarization Controller 6 enters after electrooptic modulator 7 and enters polarization scrambler 8, optoisolator 9, then as detection light enter sensor fibre 10 laggard enter optical circulator 11; By optical circulator 11, pump light meets in sensor fibre with detection light, produce after excited Brillouin amplifies and enter receiving end by circulator, namely, after Erbium-Doped Fiber Amplifier (EDFA) 12, optical filter 13, by photodetector 14 (bandwidth 10GHz), light signal is converted to electric signal; Local oscillation signal (9.8GHz) mixing produced with piezoelectric oscillator 19 in frequency mixer 18 more afterwards, realize frequency reducing, two paths of signals is divided into after entering power splitter 21 by amplifier 20 amplification, respectively by the bandpass filter (22 and 23) of two different passbands and two logarithmic detectors (24 and 25), by signal, demodulation is out respectively, two paths of signals enters differential amplifier 26 more simultaneously, realize differential amplification, deduct DC component, gather with data collecting card 27 afterwards and use host computer 28 to process; Described power splitter 17 receives the microwave modulation signal of two microwave sources (15 and 16) mixing generation modulation electrooptic modulator 7.
Adopt structure of the present invention, the signal that data collecting card can be collected amplifies in specific amplitude interval, solves data collecting card and limits due to self range, when DC component is very large, can not adjust the problem of amplifying gear.In distributed Brillouin's time-domain analysis sensor-based system, the data collecting card range that host computer is installed is limited, can not meet the demand of data acquisition to degree of accuracy, reduce the accuracy of the measurement of system.The present invention solves the problem that this system accuracies is limited by data collecting card range well.This device working stability, can measure position and temperature value (or stress value) that temperature (or stress) changes more accurately in repetitive measurement.
In apparatus of the present invention, owing to having modulated the microwave signal of two kinds of frequencies on electrooptic modulator 7: a kind of is 10GHz, not within the scope of brillouin gain; Another kind is swept-frequency signal, frequency between 10.4GHz to 10.8GHz, within the scope of brillouin gain.After light path, at receiving end, by the electric bandpass filter filtering respectively of different passband, then through differential amplifier, have passed through Brillouin amplification owing to only having a road signal, can with the signal subtraction of another road without Brillouin amplification, thus obtain needs, the signal of subsidiary heat transfer agent, and this signal amplifies through differential amplifier, has deducted DC component, thus improve signal to noise ratio (S/N ratio), reduce quantization error.This device working stability, can measure position and temperature value (or stress value) that temperature (or stress) changes more accurately in repetitive measurement.
Accompanying drawing illustrates:
Fig. 1 is system construction drawing of the present invention;
Fig. 2 is the time-domain curve figure of the end of 40Km optical fiber when adding the temperature of 80 DEG C, and wherein (a) figure is the time-domain curve not using the demodulation of differential amplification mode, and (b) figure is the time-domain curve using the demodulation of differential amplification mode.
Fig. 3 is the frequency curve figure of the end of 40Km optical fiber when adding the temperature of 80 DEG C, and wherein (a) figure is the overall frequency curve not using the demodulation of differential amplification mode, and (b) figure is the overall frequency curve using the demodulation of differential amplification mode.
Fig. 4 is the distance-thetagram of the end of 40Km optical fiber when adding the temperature of 80 DEG C, and wherein (a) figure is the integrated curved not using the demodulation of differential amplification mode, and (b) figure is the integrated curved using the demodulation of differential amplification mode.
Embodiment
Below in conjunction with accompanying drawing, the invention will be further described.
Fig. 1 is a kind of distributed optical fiber sensing system structural drawing based on differential amplification mode of the present invention, and as shown in the figure, system is made up of light path and circuit two parts.The continuous light that adjustable distributed feedback laser 1 exports is divided into two-way after photo-coupler 2, enter into Erbium-Doped Fiber Amplifier (EDFA) 4 after one route acousto-optic modulator 3 (in acousto-optic modulator injected pulse signal) modulation to amplify, afterwards by optical filter 5 filtering, then enter optical fiber; Another route light enters polarization scrambler 8 and optoisolator 9 enter electrooptic modulator 7 after Polarization Controller 6 after, then enters sensor fibre 10 as detection light.By circulator 11, pump light meets in sensor fibre with detection light, generation excited Brillouin amplifies, receiving end is entered afterwards by circulator, after Erbium-Doped Fiber Amplifier (EDFA) 12 and optical filter 13, by photodetector 14 (bandwidth 10GHz), light signal is converted to electric signal, again with local oscillation signal (9.8GHz) mixing having piezoelectric oscillator 18 to produce, realize frequency reducing, be amplified into power splitter 21 by amplifier 20 and be divided into two paths of signals, respectively by two bandpass filter (22 and 23) of different frequency, enter two logarithmic detectors (24 and 25) again by signal receiving out, two paths of signals enters differential amplifier 26 more simultaneously, realize differential amplification, deduct DC component, gather with data collecting card 27 afterwards and use host computer 28 to process.Described power splitter 17 receives the microwave modulation signal of two microwave sources (15 and 16) mixing generation modulation electrooptic modulator 7.
During enforcement, the output power of two microwave sources (15 and 16) is identical, and the output frequency of microwave source 15 is adjusted to 10GHz, and microwave source 16 carries out frequency sweep, and swept frequency range is 10.4GHz to 10.8GHz.At receiving end, the passband of two electric bandpass filter is respectively 500-3000MHz (bandpass filter 22), 150-250MHz (bandpass filter 23), to ensure that two different frequency compositions can be separated.
Fig. 2 is the time-domain curve figure of the end of 40Km optical fiber when adding the temperature of 80 DEG C, and wherein (a) figure is the time-domain curve not using the demodulation of differential amplification mode, and (b) figure is the time-domain curve using the demodulation of differential amplification mode.
Fig. 3 is the frequency curve figure of the end of 40Km optical fiber when adding the temperature of 80 DEG C, and wherein (a) figure is the frequency curve not using the demodulation of differential amplification mode, and (b) figure is the frequency curve using the demodulation of differential amplification mode.
Fig. 4 is the terminal temperature curve map of the end of 40Km optical fiber when adding the temperature of 80 DEG C, and wherein (a) figure is the terminal curve not using the demodulation of differential amplification mode, and (b) figure is the terminal curve using the demodulation of differential amplification mode.
Can see from test result above, adopt the demodulation mode of differential amplification effectively can reduce the quantization error of curve, and in final measurement result, thermometric error can be reduced.
The invention has the beneficial effects as follows:
1. this device is applicable to adopt distributed optical fiber sensing system.Adopt the mode of differential amplification, advantage is: effectively can deduct DC component, and lower quantization error makes measurement result more accurate.This device working stability, can measure position and temperature value (or stress value) that temperature (or stress) changes more accurately in repetitive measurement.
Claims (5)
1. based on a distributed sensing system for differential amplification technology, it is characterized in that, be made up of light path detection and circuit demodulates two parts; Light path adopt the microwave signal of two kinds of different frequencies be modulated on flashlight: the frequency of a road microwave signal is in Brillouin shift frequency, and comparatively Brillouin shift frequency is slightly low for the frequency of another road microwave signal; Circuit then adopts power splitter separated by two paths of signals and distinguish filtering, demodulation, then the signal after demodulation amplifies by the mode of carrying out differential amplification, realize deducting DC component, the object of lower quantization noise, its concrete structure is:
The continuous light that adjustable distributed feedback laser (1) exports is divided into two-way after photo-coupler (2), enter into Erbium-Doped Fiber Amplifier (EDFA) (4) after one route acousto-optic modulator (3) modulation to amplify, enter optical circulator (11) through optical filter (5) filtering; Another Lu Guangjing Polarization Controller (6) enters after electrooptic modulator (7) and enters polarization scrambler (8), optoisolator (9), then as detection light enter sensor fibre (10) laggard enter optical circulator (11); By optical circulator (11), pump light meets in sensor fibre with detection light, produce after excited Brillouin amplifies and enter receiving end by circulator, namely, after Erbium-Doped Fiber Amplifier (EDFA) (12), optical filter (13), by photodetector (14), light signal is converted to electric signal; The 9.8GHz local oscillation signal mixing produced with piezoelectric oscillator (19) in frequency mixer (18) more afterwards, realize frequency reducing, two paths of signals is divided into after entering power splitter (21) by amplifier (20) amplification, respectively by the bandpass filter (22 and 23) of two different frequencies and two logarithmic detectors (24 and 25), by signal, demodulation is out respectively, two paths of signals enters differential amplifier (26) more simultaneously, realize differential amplification, deduct DC component, use data collecting card (27) to gather afterwards and use host computer (28) to process; Described power splitter (17) receives the microwave modulation signal of two microwave source (15,16) mixing generations modulation electrooptic modulator (7).
2. the distributed optical fiber sensing system based on differential amplification technology according to claim 1, is characterized in that, the frequency of microwave source (15) is between 10.4GHz to 10.8GHz, and the frequency of microwave source (16) is 10GHz.
3. the distributed optical fiber sensing system based on differential amplification technology according to claim 2, is characterized in that, the output power of microwave source (15) is identical with the output power of microwave source (16).
4. the distributed optical fiber sensing system based on differential amplification technology according to claim 1, is characterized in that, the enlargement factor of differential amplifier (26) is 10-20 times.
5. the distributed optical fiber sensing system based on differential amplification technology according to claim 1, is characterized in that, bandpass filter (22) passband is the passband of 500-3000MHz bandpass filter (23) is 150-250MHz.
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| CN106840370A (en) * | 2017-04-06 | 2017-06-13 | 吉林大学 | A kind of optical fiber interference type wave detector resonant frequency measuring device and measuring method |
| CN107014518A (en) * | 2017-03-30 | 2017-08-04 | 华中科技大学 | A kind of optical fiber temperature sensing device |
| CN109067460A (en) * | 2018-07-25 | 2018-12-21 | 北京大学 | A kind of optical fibre ring Propagation Simulation system based on distributed feedback laser |
| CN110530551A (en) * | 2019-08-27 | 2019-12-03 | 西南交通大学 | The temperature extraction method of BOTDA based on Support Vector Machines Optimized |
| CN110581714A (en) * | 2019-09-17 | 2019-12-17 | 上海航天计算机技术研究所 | satellite full-duplex VDES system radio frequency receiver |
| CN111901035A (en) * | 2020-07-29 | 2020-11-06 | 重庆邮电大学 | Instantaneous microwave frequency measuring device and method based on dispersion Fourier transform |
| CN112033568A (en) * | 2020-08-07 | 2020-12-04 | 太原理工大学 | Temperature and strain optical fiber sensing system adopting double-pulse modulation |
| CN112082676A (en) * | 2020-08-11 | 2020-12-15 | 潍坊科技学院 | Real-time monitoring device and method for ocean engineering cofferdam stress |
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| CN112033568A (en) * | 2020-08-07 | 2020-12-04 | 太原理工大学 | Temperature and strain optical fiber sensing system adopting double-pulse modulation |
| CN112033568B (en) * | 2020-08-07 | 2022-08-09 | 太原理工大学 | Temperature and strain optical fiber sensing system adopting double-pulse modulation |
| CN112082676A (en) * | 2020-08-11 | 2020-12-15 | 潍坊科技学院 | Real-time monitoring device and method for ocean engineering cofferdam stress |
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