CN111928938A - Long-distance distributed optical fiber vibration detection system - Google Patents
Long-distance distributed optical fiber vibration detection system Download PDFInfo
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- CN111928938A CN111928938A CN202010946123.XA CN202010946123A CN111928938A CN 111928938 A CN111928938 A CN 111928938A CN 202010946123 A CN202010946123 A CN 202010946123A CN 111928938 A CN111928938 A CN 111928938A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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Abstract
The invention discloses a method for realizing a long-distance distributed optical fiber vibration system, which adopts two EDFAs to amplify signals in a light path, wherein the first amplification is to amplify a detection light pulse signal to improve the energy of light entering the optical fiber so that the detection light pulse can be transmitted in the optical fiber farther, and the other EDFA is to amplify the returned Rayleigh scattering light to improve the energy value of the scattering light. Continuous light emitted by laser passes through the 1 x2 coupler and then respectively passes through the two branches, one path of light is modulated into frequency-shifted optical pulses through the AOM, the frequency-shifted optical pulses are amplified by the EDFA, the spontaneous emission (ASE) of the EDFA is reduced through the optical filter, and then the frequency-shifted optical pulses are coupled into the sensing optical fiber through the circulator. Rayleigh scattered light in the measuring optical fiber passes through the circulator, is amplified by the EDFA, is filtered and is then coherent with the other path of local oscillator reference light in the 2X2 coupler, and finally, coherent signals are input into the balance detector to realize photoelectric conversion.
Description
Technical Field
The invention relates to the technical field of optical fiber vibration detection, in particular to a long-distance distributed optical fiber vibration detection system.
Background
With the progress of the technology, the distributed optical fiber vibration detection technology is more and more widely applied to pipeline leakage detection, pipeline excavation prevention and various perimeter security. Due to the long distance between pipelines, there is a strong need for a distributed optical fiber vibration detection technique that can test ultra-long distances without reducing spatial resolution to reduce cost.
Disclosure of Invention
The invention aims to solve the technical problems that a long-distance optical fiber vibration detection system is high in cost and low in spatial resolution.
In order to solve the technical problems, the invention adopts the technical scheme that: long distance distribution type optic fibre vibration detecting system, its characterized in that: the device comprises a laser generator, a 1 x2 optical fiber coupler, a 2x2 optical fiber coupler, an acoustic-optical modulator, two erbium-doped amplifiers, two optical narrow band filters, a circulator, a detection optical cable, a balance detector, a pulse generator, an electric signal amplifier, a high-speed acquisition card and an upper computer; the 1 x2 optical fiber coupler divides a laser light source into two paths according to a proportion, wherein one path is used as local oscillator light, and the other path is used as signal light; the signal light enters the detection optical cable through the acousto-optic modulator, the erbium-doped amplifier, the optical narrow-band filter and the circulator, and the Rayleigh scattering light is coherent with the local oscillator light after being coupled through the circulator, the erbium-doped amplifier, the optical narrow-band filter and the 2x2 optical fiber; the balance detector detects the coherent optical signal and is connected with an electric signal amplifier, and the high-speed acquisition card is connected with the electric signal amplifier; the pulse generator is connected with the acousto-optic modulator to modulate the signal light; the high-speed acquisition card is connected with the upper computer and starts to acquire data after receiving the trigger signal.
Further, the splitting ratio of the 1 x2 fiber coupler is 80: 20, 20% of the output optical power of the laser generator is used as local oscillator light, and 80% of the output optical power is used as signal light.
Further, the optical narrow-band filter has a center wavelength of 1550.12 nm and a bandwidth of 0.2 nm, and is used for filtering out a part of the spontaneous radiation of the erbium-doped fiber amplifier.
Furthermore, the high-speed data acquisition card performs over-sampling acquisition on the signals, and accumulates the acquired data in space, so that the signal-to-noise ratio of the system is improved.
Furthermore, when the pulse width sent by the pulse generator is t and the frequency adopted by the data acquisition card is f, accumulating t f continuous data in each group.
The technical scheme shows that the invention has the following advantages: two EDFAs are adopted to amplify signals in a light path, the first EDFA amplification is used for amplifying a detection light pulse signal to improve the energy of light entering an optical fiber, so that the detection light pulse can be transmitted in the optical fiber farther, and the other EDFA (erbium-doped fiber amplifier) is used for amplifying the returned Rayleigh scattering light to improve the energy value of the scattering light; after a narrow-band filter is additionally arranged, most of spontaneous radiation can be filtered out, and Rayleigh scattering signals can pass through without damage, so that the signal-to-noise ratio is improved, and the signal-to-noise ratio of a system is improved by adopting oversampling without influencing the spatial resolution.
Drawings
FIG. 1 is a functional block diagram of the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
As shown in fig. 1, the long-distance distributed optical fiber vibration detection system of the present invention includes a laser generator, a 1 × 2 optical fiber coupler, a 2 × 2 optical fiber coupler, an acousto-optic modulator, two erbium-doped amplifiers, two optical narrow-band filters, a circulator, a detection optical cable, a balance detector, a pulse generator, an electrical signal amplifier, a high-speed acquisition card, and an upper computer.
The 1 x2 optical fiber coupler divides a laser light source into two paths according to a proportion, wherein one path is used as local oscillator light, the other path is used as signal light, and the light splitting ratio of the 1 x2 optical fiber coupler is selected to be 80 according to the saturated input optical power of the balance detector and the output optical power of the narrow linewidth laser: 20 (20% of the output optical power of the laser is used as the local oscillator light, and 80% of the output optical power is used as the signal light), so that the power of the optical signal after the local oscillator light and the rayleigh scattered light are coherent can reach the optimal output effect of the signal after being input into the balanced detector.
The signal light enters the detection optical cable through the acousto-optic modulator, the erbium-doped amplifier, the optical narrow-band filter and the circulator, the erbium-doped optical fiber amplifier amplifies the detection light pulse, and the energy of the detection light pulse can be transmitted farther. The erbium-doped fiber amplifier is followed by a filter with the center wavelength of 1550.12 nm and the bandwidth of 0.2 nm, and part of the spontaneous emission (ASE) of the EDFA is filtered out.
The Rayleigh scattered light is coherent with the local oscillator light after being coupled by the circulator, the erbium-doped amplifier, the optical narrow-band filter and the 2x2 optical fiber. The erbium-doped fiber amplifier amplifies the returned Rayleigh scattering light and improves the energy value of the Rayleigh scattering light, so that beat frequency energy of local oscillation light and scattering light is increased, and a better signal-to-noise ratio is obtained during photoelectric conversion. The erbium-doped fiber amplifier is followed by a filter with a central wavelength of 1550.12 nm and a bandwidth of 0.2 nm. Because the rayleigh scattered back signal is very small, the influence of spontaneous emission (ASE) noise of an EDFA (erbium-doped fiber amplifier) on the scattered signal is large, most of the spontaneous emission (ASE) is filtered out after a narrow-band filter is additionally arranged, and the rayleigh scattered signal can pass through without damage, so that the signal-to-noise ratio is improved.
The balance detector detects the coherent optical signal and is connected with an electric signal amplifier, and the high-speed acquisition card is connected with the electric signal amplifier; the pulse generator is connected with the acousto-optic modulator to modulate the signal light; the high-speed acquisition card is connected with the upper computer and starts to acquire data after receiving the trigger signal.
The high-speed data acquisition card is adopted to carry out oversampling acquisition on signals, and the acquired data are accumulated in space, so that the signal-to-noise ratio of the system is improved. The distance of the detection optical cable is 50 kilometers, the pulse width sent by the pulse generator is 100 nanoseconds, the period is 500 microseconds periodic signals, the sampling frequency of the data acquisition card is 250M/S, 2000 groups of data are acquired by the data acquisition card within one second (the number of groups acquired per second is determined by the period of the signals sent by the pulse generator), and the number of sampling points of each group of data is 125000 points. Because the pulse width of the system is 100 nanoseconds, in order to improve the signal-to-noise ratio of the system without influencing the spatial resolution, each group of continuous 25 data is accumulated, and 125000 point data is converted into 5000 point data.
Claims (5)
1. Long distance distribution type optic fibre vibration detecting system, its characterized in that: the device comprises a laser generator, a 1 x2 optical fiber coupler, a 2x2 optical fiber coupler, an acoustic-optical modulator, two erbium-doped amplifiers, two optical narrow band filters, a circulator, a detection optical cable, a balance detector, a pulse generator, an electric signal amplifier, a high-speed acquisition card and an upper computer;
the 1 x2 optical fiber coupler divides a laser light source into two paths according to a proportion, wherein one path is used as local oscillator light, and the other path is used as signal light; the signal light enters the detection optical cable through the acousto-optic modulator, the erbium-doped amplifier, the optical narrow-band filter and the circulator, and the Rayleigh scattering light is coherent with the local oscillator light after being coupled through the circulator, the erbium-doped amplifier, the optical narrow-band filter and the 2x2 optical fiber;
the balance detector detects the coherent optical signal and is connected with an electric signal amplifier, and the high-speed acquisition card is connected with the electric signal amplifier;
the pulse generator is connected with the acousto-optic modulator to modulate the signal light; the high-speed acquisition card is connected with the upper computer and starts to acquire data after receiving the trigger signal.
2. The long distance distributed optical fiber vibration detection system of claim 1, wherein: the splitting ratio of the 1 x2 optical fiber coupler is 80: 20, 20% of the output optical power of the laser generator is used as local oscillator light, and 80% of the output optical power is used as signal light.
3. The long distance distributed optical fiber vibration detection system of claim 1, wherein: the optical narrow-band filter has a central wavelength of 1550.12 nm and a bandwidth of 0.2 nm, and is used for filtering out a part of spontaneous radiation of the erbium-doped fiber amplifier.
4. The long distance distributed optical fiber vibration detection system of claim 1, wherein: the high-speed data acquisition card is used for over-sampling and acquiring signals, and accumulating the acquired data in space, so that the signal-to-noise ratio of the system is improved.
5. The long distance distributed fiber optic vibration system of claim 4, wherein: and when the pulse width sent by the pulse generator is t and the frequency adopted by the data acquisition card is f, accumulating the t x f continuous data in each group.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112364836A (en) * | 2020-12-07 | 2021-02-12 | 无锡科晟光子科技有限公司 | Vibration optical fiber signal classification method based on full convolution neural network |
| CN114577324A (en) * | 2022-02-17 | 2022-06-03 | 一石数字技术成都有限公司 | Distributed optical fiber vibration monitoring system |
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| CN107643120A (en) * | 2017-11-10 | 2018-01-30 | 武汉理工光科股份有限公司 | The distributed fiber Rayleigh of polarization decay is avoided to scatter vibration sensing system and method |
| CN107664541A (en) * | 2017-09-18 | 2018-02-06 | 南京大学 | A kind of distributed optical fiber vibration and Temperature fusion sensor-based system and method |
| CN107907151A (en) * | 2017-12-15 | 2018-04-13 | 中国人民解放军国防科技大学 | Phi OTDR and sensing method based on optical frequency modulation and direct detection |
| GB2558922A (en) * | 2017-01-20 | 2018-07-25 | Focus Sensors Ltd | Distributed acoustic sensing |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| GB2558922A (en) * | 2017-01-20 | 2018-07-25 | Focus Sensors Ltd | Distributed acoustic sensing |
| CN107664541A (en) * | 2017-09-18 | 2018-02-06 | 南京大学 | A kind of distributed optical fiber vibration and Temperature fusion sensor-based system and method |
| CN107643120A (en) * | 2017-11-10 | 2018-01-30 | 武汉理工光科股份有限公司 | The distributed fiber Rayleigh of polarization decay is avoided to scatter vibration sensing system and method |
| CN107907151A (en) * | 2017-12-15 | 2018-04-13 | 中国人民解放军国防科技大学 | Phi OTDR and sensing method based on optical frequency modulation and direct detection |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112364836A (en) * | 2020-12-07 | 2021-02-12 | 无锡科晟光子科技有限公司 | Vibration optical fiber signal classification method based on full convolution neural network |
| CN114577324A (en) * | 2022-02-17 | 2022-06-03 | 一石数字技术成都有限公司 | Distributed optical fiber vibration monitoring system |
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Inventor after: Wang Yichuan Inventor before: Wang Yichuan Inventor before: Hu Xiaohui |
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Application publication date: 20201113 |