CN103837165A - Brillouin time-domain analysis system based on Brillouin laser and automatic heterodyne detection - Google Patents
Brillouin time-domain analysis system based on Brillouin laser and automatic heterodyne detection Download PDFInfo
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- CN103837165A CN103837165A CN201210526238.9A CN201210526238A CN103837165A CN 103837165 A CN103837165 A CN 103837165A CN 201210526238 A CN201210526238 A CN 201210526238A CN 103837165 A CN103837165 A CN 103837165A
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Abstract
The invention discloses a Brillouin time-domain analysis system based on a Brillouin laser and automatic heterodyne detection and belongs to the technical field of optical fiber sensors. The Brillouin time-domain analysis system comprises a laser, an isolator, a coupler, a first Er-doped fiber amplifier, the Brillouin laser, a signal generator, a phase modulator, sensing optical fiber, a circulator, a second Er-doped fiber amplifier, a pulse generator, a scrambler, a photovoltaic conversion module, and a digital signal processing module. The Brillouin time-domain analysis system is characterized in that the Brillouin laser is used for realizing broadband frequency shift for incoming laser, the phase modulator is used for modulating laser after frequency downward shift so as to generate double-sideband signals, the signals and pulse pump light generated by the pulse generator generate stimulated Brillouin scattering effect in the sensing optical fiber, and optical signals after action conducts automatic heterodyne detection through the photovoltaic conversion module. The Brillouin time-domain analysis system is weakened in phase noise, improves the signal to noise ratio of detection signal, ensures the temperature/strain measurement accuracy of a whole section of the sensing optical fiber, and is made to be more compact.
Description
Technical field
The present invention relates to optical fiber Brillouin time-domain analysis system, belong to fiber optic sensor technology field.
Background technology
Distributed Optical Fiber Sensing Techniques based on Brillouin scattering effect is the focus sensing technology of Recent study, it can perception whole piece Fibre Optical Sensor link on space distribution and the time dependent information of temperature, strain, in the healthy and safe monitoring of the great structures such as oil country tubular good, bridge dam, have important application prospect.In Brillouin's distribution optical fiber sensor, the utilization of Brillouin's time-domain analysis instrument be stimulated Brillouin scattering effect, strengthened detectable signal, distance sensing is far away.
At present, improving Brillouin's time-domain analysis system detection signal signal to noise ratio (S/N ratio) is Technology Difficulties, and detection method can be taked direct Detection Method and conventional coherent detection method.In direct Detection Method, after continuous probe light and pulse pump light Brillouin effect, directly inject photodetector through circulator and convert electric signal to; The detection signal signal to noise ratio (S/N ratio) of the method is directly proportional to detection of optical power, but detection of optical power is subject to the restriction of optical fiber modulational instability and pumping drain effect, has therefore limited the raising of system signal signal to noise ratio (S/N ratio).In conventional coherent detection method, a kind of method is that directly to convert the continuous probe light after Brillouin effect and incident light to frequency with broadband photoelectric detector after relevant beat frequency be the electric signal about 11GHz, also need, by microwave signal beat frequency close with frequency this electric signal, to make signal be down to hundreds of order of megahertz for convenience of data collection and analysis; Another method is that incident light is carried out to microwave electrooptical modulation, makes it to produce frequency and moves down also as relevant local oscillator light, directly collection analysis and demodulates information of the relevant difference frequency signal of continuous probe light and local oscillator light.But in above-mentioned two kinds of coherence detection, exist following problem: wideband detector relative signal-to-noise ratio is low; Continuous probe light is different from local oscillator light transmission path, has introduced additive phase noise, reduces detection signal signal to noise ratio (S/N ratio); High-frequency microwave volume source is large, does not cause system compact etc.
Summary of the invention
The invention provides a kind of Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection, with the phase noise of attenuation systems, improve system signal noise ratio, ensure temperature/strain measurement precision of whole section of sensor fibre, make system compacter simultaneously.
The technical solution adopted in the present invention is: a kind of Brillouin's time-domain analysis measuring method and system based on Brillouin laser and self-heterodyne detection technique is provided.In Brillouin's time-domain analysis system architecture, comprise laser instrument (1), isolator (2), coupling mechanism (3), the first Erbium-Doped Fiber Amplifier (EDFA) (4), Brillouin laser (5), signal generator (6), phase-modulator (7), sensor fibre (8), circulator (9), the second Erbium-Doped Fiber Amplifier (EDFA) (10), pulse producer (11), scrambler (12), photoelectric conversion module (13), digital signal processing module (14).
Described laser instrument (1) is by isolator (2) butt coupling device (3), the light beam that described coupling mechanism (3) produces laser instrument (1) is divided into two-way: first via laser is for generation of Brillouin's detectable signal light, be connected with the input end of the first Erbium-Doped Fiber Amplifier (EDFA) (4), the output terminal of described the first Erbium-Doped Fiber Amplifier (EDFA) (4) is connected with Brillouin laser (5) input end, described Brillouin laser (5) output terminal is connected with the first input end of phase-modulator (7), the second input end of described phase-modulator (7) is connected with signal generator (6), the output terminal of described phase-modulator (7) is connected with sensor fibre (8), the output terminal of described sensor fibre (8) is connected with second port (92) of circulator (9),
The second road laser is for generation of Brillouin's pulse pump light, after the second Erbium-Doped Fiber Amplifier (EDFA) (10) amplifies, be connected with the input end of pulse producer (11), described pulse producer (11) output terminal is connected with first port (91) of circulator (9) through scrambler (12);
The 3rd port (93) of described circulator (9) connects photoelectric conversion module (13) and digital signal processing module (14) successively, by with the effect of Brillouin's pulse pump light generation stimulated Brillouin scattering after detectable signal light carry out respectively self-heterodyne receive and digital signal processing demodulation, obtain the temperature/Strain Distribution along the line at sensor fibre.
According to the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection provided by the present invention, it is characterized in that laser instrument (1) is that spectral width is less than 1MHz, output power is greater than 20mW, the high stable fiber laser that centre wavelength is 1550nm.
According to the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection provided by the present invention, it is characterized in that described Brillouin laser (5) produces broadband frequency displacement for completing the laser signal that laser instrument (1) is injected, is ring cavity structure fiber laser: be made up of circulator, isolator, output coupler and highly nonlinear optical fiber; Described highly nonlinear optical fiber Brillouin shift is than the low 360MHz of described sensor fibre (8) Brillouin shift.
According to the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection provided by the present invention, it is characterized in that described signal generator (6) frequency range is 250kHz～1GHz.
According to the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection provided by the present invention, it is characterized in that described phase-modulator (7) is for generation of double-sideband signal, for electro-optic phase modulator, service band is 1550nm, bandwidth≤1GHz.
According to the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection provided by the present invention, it is characterized in that the frequency response bandwidth of described photoelectric conversion module (13) is 1GHz.
Beneficial effect: incident laser is realized to broadband frequency displacement because the present invention utilizes Brillouin laser, and the laser after frequency displacement is carried out to phase-modulation generation sideband signals, take laser carrier as local oscillator light wave, the lower sideband signal producing take phase-modulation is as surveying light wave and with pulse pump light, stimulated Brillouin scattering effect occurring in sensor fibre, both realize self-heterodyne beat frequency through photoelectric conversion module and detect, because having identical traffic path, local oscillator light and flashlight weaken Electronics noice and phase of light wave noise that system is introduced, improve system signal noise ratio, ensure temperature/strain measurement precision of whole section of sensor fibre, also make system compacter.
Accompanying drawing explanation
Fig. 1 is the structural representation of the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection provided by the present invention.
Fig. 2 is laser frequency, Brillouin's pumping wave frequency and probing wave frequency diagram.V in figure
0for the frequency of laser instrument (1); v
1for the frequency of light wave of laser instrument (1) after Brillouin laser (5) broadband frequency displacement, the local oscillator light wave detecting as self-heterodyne of the present invention; (v
0-v
2), g (v) represents respectively Brillouin shift and the gain spectral of sensor fibre (8); v
mrepresent the modulating frequency of signal generator (6), (frequency is v to the lower sideband light signal that phase-modulator (7) produces
1-v
m) survey light wave as the Brillouin of self-heterodyne detection of the present invention.
Embodiment
Below in conjunction with accompanying drawing, the present invention is further described.
As shown in Figure 1: Brillouin's time-domain analysis system of the present invention, comprises laser instrument (1), isolator (2), coupling mechanism (3), the first Erbium-Doped Fiber Amplifier (EDFA) (4), Brillouin laser (5), signal generator (6), phase-modulator (7), sensor fibre (8), circulator (9), the second Erbium-Doped Fiber Amplifier (EDFA) (10), pulse producer (11), scrambler (12), photoelectric conversion module (13), digital signal processing module (14).Wherein, described laser instrument (1) is for generation of Brillouin's pumping wave and probing wave, it is characterized in that: spectral width is less than 1MHz, output power is greater than 20mW, centre wavelength is 1550nm, isolator (2) is connected with laser instrument (1), for the damage of avoiding reflected light to cause laser instrument, coupling mechanism (3) is connected with described isolator (2), be divided into two bundles for the light beam that laser instrument (1) is produced, Erbium-Doped Fiber Amplifier (EDFA) (4 and 10) is connected with coupling mechanism (3), be respectively used to the amplification to two-beam: first via light beam amplifies through described the first Erbium-Doped Fiber Amplifier (EDFA) (4), survey light wave and local oscillator light wave for generation of Brillouin, the second road light beam amplifies through described the second Erbium-Doped Fiber Amplifier (EDFA) (10), for generation of Brillouin's pulse pump light.In the first light path, Brillouin laser (5) is connected with described the first Erbium-Doped Fiber Amplifier (EDFA) (4) output terminal, making light beam produce frequency moves down, its frequency displacement size is than the low 360MHz of sensor fibre (8) Brillouin shift, described Brillouin laser (5) is characterised in that as ring cavity structure fiber laser: be made up of circulator, isolator, output coupler and highly nonlinear optical fiber, described sensor fibre (8) is standard single mode telecommunication optical fiber, and Brillouin shift is 11GHz; By signal generator (6), the laser that injects phase-modulator (7) after frequency displacement is carried out to phase-modulation, for generation of sideband signals, as shown in Figure 2, its medium frequency is v
1-v
mlower sideband signal survey light wave as Brillouin, after Brillouin laser (5) frequency displacement, inject phase-modulator (7), frequency is v
1laser signal as self-heterodyne detect local oscillator light wave; Brillouin surveys light wave and local oscillator light wave injects sensor fibre (8) simultaneously, and Brillouin surveys light wave and will stimulated Brillouin scattering effect occur in optical fiber with the pulse pump light of the second light path generation.In the second light path, pulse producer (11) is connected with described the second Erbium-Doped Fiber Amplifier (EDFA) (10) output terminal, is v by the frequency of input
0laser Modulation become Brillouin's pulse pump light, its pulse repetition rate is less than 1kHz, pulsewidth is less than 1 μ s; Scrambler (12) is connected with pulse producer (11) output terminal, for suppressing the polarization correlated of brillouin gain, disturb inclined to one side speed and be greater than 1kHz, output polarization degree is less than 5%, disturb Brillouin's pulse pump light to the rear and be coupled into sensor fibre (8) through circulator (9), the Brillouin who produces with the first light path surveys light wave effect.Local oscillator light wave is surveyed light wave and is carried out self-heterodyne detection through described circulator (9) the 3rd port transmission to photoelectric conversion module (13) again with obtaining Brillouin that excited Brillouin gain amplifies, converts supplied with digital signal processing module (14) after electric signal to.For obtaining the Brillouin shift of sensor fibre (8), Brillouin's pulse pump light and Brillouin survey frequency sweep between light wave by signal generator (6) the modulating frequency v described in adjusting the first light path
mcomplete.Finally, by digital signal processing module (14) data acquisition, process and demodulate sensor fibre (8) temperature/Strain Distribution along the line.
In the present invention, signal generator (6) frequency range is 250kHz～1GHz.
In the present invention, phase-modulator (7), for generation of double-sideband signal, is electro-optic phase modulator, and service band is 1550nm, bandwidth≤1GHz.
In the present invention, the frequency response bandwidth of photoelectric conversion module (13) is 1GHz.
Claims (6)
1. the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection, is characterized in that comprising laser instrument (1), isolator (2), coupling mechanism (3), the first Erbium-Doped Fiber Amplifier (EDFA) (4), Brillouin laser (5), signal generator (6), phase-modulator (7), sensor fibre (8), circulator (9), the second Erbium-Doped Fiber Amplifier (EDFA) (10), pulse producer (11), scrambler (12), photoelectric conversion module (13), digital signal processing module (14);
Described laser instrument (1) is by isolator (2) butt coupling device (3), the light beam that described coupling mechanism (3) produces laser instrument (1) is divided into two-way: first via laser is for generation of Brillouin's detectable signal light, be connected with the input end of the first Erbium-Doped Fiber Amplifier (EDFA) (4), the output terminal of described the first Erbium-Doped Fiber Amplifier (EDFA) (4) is connected with Brillouin laser (5) input end, described Brillouin laser (5) output terminal is connected with the first input end of phase-modulator (7), the second input end of described phase-modulator (7) is connected with signal generator (6), the output terminal of described phase-modulator (7) is connected with sensor fibre (8), the output terminal of described sensor fibre (8) is connected with second port (92) of circulator (9),
The second road laser is for generation of Brillouin's pulse pump light, after the second Erbium-Doped Fiber Amplifier (EDFA) (10) amplifies, be connected with the input end of pulse producer (11), described pulse producer (11) output terminal is connected with first port (91) of circulator (9) through scrambler (12);
The 3rd port (93) of described circulator (9) connects photoelectric conversion module (13) and digital signal processing module (14) successively, by with the effect of Brillouin's pulse pump light generation stimulated Brillouin scattering after detectable signal light carry out respectively self-heterodyne receive and digital signal processing demodulation, obtain the temperature/Strain Distribution along the line at sensor fibre.
2. the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection according to claim 1, it is characterized in that laser instrument (1) is that spectral width is less than 1MHz, output power is greater than 20mW, the high stable fiber laser that centre wavelength is 1550nm.
3. the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection according to claim 1, it is characterized in that described Brillouin laser (5) produces broadband frequency displacement for completing the laser signal that laser instrument (1) is injected, is ring cavity structure fiber laser: be made up of circulator, isolator, output coupler and highly nonlinear optical fiber; Described highly nonlinear optical fiber Brillouin shift is than the low 360MHz of described sensor fibre (8) Brillouin shift.
4. the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection according to claim 1, is characterized in that the frequency range of described signal generator (6) is 250kHz～1GHz.
5. the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection according to claim 1, it is characterized in that described phase-modulator (7) is for generation of double-sideband signal, for electro-optic phase modulator, service band is 1550nm, bandwidth≤1GHz.
6. the Brillouin's time-domain analysis system based on Brillouin laser and self-heterodyne detection according to claim 1, is characterized in that the frequency response bandwidth of described photoelectric conversion module (13) is 1GHz.
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| CN104019836A (en) * | 2014-06-23 | 2014-09-03 | 哈尔滨工业大学 | Brillouin optical-time-domain analyzer based on coherence dual-pulse pair sequence technology and method for restraining common-mode noise by utilizing same |
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| CN107179097B (en) * | 2016-03-10 | 2019-08-09 | 南京理工大学 | Optical fiber interference type sensing modulation-demo-demodulation method and device based on phase shift signal modulation |
| CN106785905A (en) * | 2017-01-19 | 2017-05-31 | 桂林电子科技大学 | A kind of electrooptic modulator based on Prague phase-shifted grating |
| CN107588926A (en) * | 2017-10-30 | 2018-01-16 | 中光华研电子科技有限公司 | A kind of fault monitoring system and method for overlength optical cable |
| CN110417477A (en) * | 2019-07-16 | 2019-11-05 | 桂林电子科技大学 | A kind of optical generation method and device of 40GHz millimeter-wave signal |
| CN110417477B (en) * | 2019-07-16 | 2022-07-05 | 桂林电子科技大学 | Optical generation device for 40GHz millimeter wave signal |
| CN112414584A (en) * | 2020-10-19 | 2021-02-26 | 太原理工大学 | Brillouin optical time domain analysis device and method based on pi-pulse Gray code coding |
| CN113670353A (en) * | 2021-08-17 | 2021-11-19 | 广西师范大学 | Brillouin optical time domain analyzer based on few-mode optical fiber mode multiplexing |
| CN113670353B (en) * | 2021-08-17 | 2023-04-25 | 广西师范大学 | Brillouin optical time domain analyzer based on few-mode optical fiber mode multiplexing |
| CN114608631A (en) * | 2022-01-30 | 2022-06-10 | 杭州光传科技有限公司 | Brillouin optical time domain reflection sensing device |
| CN114608631B (en) * | 2022-01-30 | 2024-04-26 | 杭州光传科技有限公司 | Brillouin optical time domain reflection sensing device |
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Application publication date: 20140604 |