CN104776870A - Device for increasing temperature resolution of remote BOTDR (Brillouin optical time domain reflectometer) system by utilizing distributed raman amplification and EDFA (erbium-doped optical fiber amplifier) technologies - Google Patents
Device for increasing temperature resolution of remote BOTDR (Brillouin optical time domain reflectometer) system by utilizing distributed raman amplification and EDFA (erbium-doped optical fiber amplifier) technologies Download PDFInfo
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- CN104776870A CN104776870A CN201410826140.4A CN201410826140A CN104776870A CN 104776870 A CN104776870 A CN 104776870A CN 201410826140 A CN201410826140 A CN 201410826140A CN 104776870 A CN104776870 A CN 104776870A
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Abstract
The invention discloses a device for increasing the temperature resolution of a remote BOTDR (Brillouin optical time domain reflectometer) system by utilizing distributed Raman amplification and EDFA (erbium-doped optical fiber amplifier) technologies. The device comprises an optical fiber sensing system device, related experimental data obtained by measurement performed by utilizing the built BOTDR system, and a temperature resolution comparison chart obtained with a method and a conventional method. The device can be used for increasing the temperature resolution of the remote BOTDR system.
Description
Technical field
The present invention relates to a kind of device utilizing distributed raman amplification and EDFA technology to improve remote BOTDR system temperature resolution.
Background technology
In recent years, Distributed Optical Fiber Sensing Techniques based on spontaneous brillouin scattering has caused the extensive concern of people, it has huge market potential, this technology needs to carry out the monitoring growing distance in fields such as pipeline, cable, bridge, railways, but, the power of spontaneous brillouin scattering signal is but very weak, along with the increase of distance sensing, the consumption of pumping can make the power of brillouin scattering signal can be more weak, the signal to noise ratio (S/N ratio) of system will become worse and worse, and the temperature resolution of system also can become more and more lower.Therefore, the temperature resolution how improving remote BOTDR system becomes a study hotspot of Distributed Optical Fiber Sensing Techniques.
In order to improve distance sensing and the temperature resolution of BOTDR system, distributed raman amplification technology can be adopted, but the peak power of continuous Raman pumping laser but has a definite limitation, distance sensing can not be far, along with the increase of distance sensing, at the end of sensor fibre, temperature resolution can be very low.At present, adopt coding techniques and system averaging method can improve the signal to noise ratio (S/N ratio) of system, and then raising distance sensing, but, coding techniques must within certain code length scope to the improvement of system signal noise ratio, after the length exceeding optimum coding, along with the increase of code length, adopt coding techniques can not continue the signal to noise ratio (S/N ratio) of raising system again, temperature resolution can not improve again, and when carrying out demodulation to the system responses of coded signal, it is more complicated that hardware implements; Employing system averaging method, while raising system sensing distance, but considerably increases the Measuring Time of system.
Summary of the invention
The object of the present invention is to provide a kind of device utilizing distributed raman amplification and EDFA technology to improve remote BOTDR system temperature resolution, this device has compensating signal decay, improves the advantage of long range systems temperature resolution.
In order to realize above-mentioned technical purpose, technical scheme of the present invention is:
Utilize distributed raman amplification and EDFA technology to improve a device for remote BOTDR system temperature resolution, comprise Raman fiber generating device of laser, direct impulse light generating device, wavelength division multiplexer, optical circulator, first fiber grating, second fiber grating, 3rd fiber grating, coupling mechanism, photodetector, first sensor fibre, second sensor fibre, first coupling mechanism, second coupling mechanism, one EDFA, electrooptic modulator, mixing filter, spectrum analyzer, AD data acquisition unit and display device, above-mentioned detection light generating device rear end adds optoisolator, and prevent reflected light from disturbing light source and damaging, the combination then entering optical attenuator and EDFA can amplify light intensity, meticulous regulating optical power, eventually passes Polarization Controller, acousto-optic modulator, optical signal modulation can be become low noise with the combination of matched FBG by circulator, the pulsed light that polarization direction is consistent, the output terminal of direct impulse light generating device connects the first port of the first optical circulator, second port of the first optical circulator is connected wavelength division multiplexer respectively with the output terminal of first sound-optic modulator, 3rd port of the first optical circulator connects the first port of the second optical circulator by the first fiber grating, second port of the second optical circulator connects the second fiber grating, 3rd port of the second optical circulator connects an input end of the second coupling mechanism by the 3rd fiber grating, wavelength division multiplexer connects the first coupling mechanism and separates a road light by an output terminal and is incorporated in electrooptic modulator, by the frequency of 11GHz, it is modulated, for generation of this flash of light preceding an earthquake after frequency displacement, and output to another input end of the second coupling mechanism, another output terminal of first coupling mechanism connects EDFA by the first sensor fibre, EDFA connects the second sensor fibre, after the output terminal connection photodetector of the second coupling mechanism, successively through mixing filter, spectrum analyzer, display device is connected after AD data acquisition unit.
Described device, the length of the first described sensor fibre is not more than 50km.
Described device, the length of the second described sensor fibre is not more than 50km.
Described device, the first fiber grating is identical with the wavelength of detection light generating device with the centre wavelength of the 3rd fiber grating, and bandwidth is not more than 0.2nm.
Described device, the centre wavelength of the second fiber grating is identical with the wavelength of detection light generating device, and bandwidth is 1-2nm.
Described device, described direct impulse light generating device comprises the detection light generating device, optoisolator, optical attenuator, the 2nd EDFA, Polarization Controller and the first sound-optic modulator that connect successively, described Raman fiber generating device of laser comprises the Raman fiber lasers and second sound-optic modulator that connect successively, and first sound-optic modulator and second sound-optic modulator keep synchro switch state.
Technique effect of the present invention is, by adopting distributed raman amplification technology, the ad-hoc location of sensor fibre adds EDFA, and then connect sensor fibre, so from the head end of sensor fibre to tail end, the power of spontaneous brillouin scattering signal wherein can keep certain intensity, and the temperature resolution of sensor fibre far-end only can reduce a very little part along with the increase of distance sensing.Meanwhile, the backward Rayleigh scattering signal of filtering, reduce noise power, weaken its interference to backward Brillouin scattering signal extraction.
Below in conjunction with accompanying drawing, the invention will be further described.
Accompanying drawing explanation
Fig. 1 structural representation of the present invention;
Fig. 2 is the specific design method that the second sensor fibre verified the present invention connects;
Fig. 3 is the backward Brillouin scattering signal graph in the embodiment of the present invention near sensor fibre heating region;
Fig. 4 is classic method and the inventive method temperature resolution contrast schematic diagram along sensor fibre.
Embodiment
See Fig. 1, the present invention includes 1480nm Raman fiber lasers, 1535nm detects light generating device, WDM (wavelength division multiplexer), optical circulator, first fiber grating, second fiber grating, 3rd fiber grating, coupling mechanism, photodetector, optoisolator, VOA (optical attenuator), Polarization Controller (PS), acousto-optic modulator (AOM), electrooptic modulator (EOM), first sensor fibre, second sensor fibre, EDFA, heating arrangement, spectrum analyzer, above-mentioned detects light by 1535nm, the polarization direction that 1480nm Raman fiber lasers and some optical device produce is consistent, the pulsed light that luminous power is enough large separates a road light through coupling mechanism 1 and is incorporated in electrooptic modulator, modulates it by the frequency of 11GHz, and for generation of this flash of light preceding an earthquake after frequency displacement, another road light is through the sensor fibre of one section of 45km, after EDFA amplifies, enter in another part sensor fibre through heating arrangement again, when light is propagated along sensor fibre, backscatter signal is returned from 2 ports of circulator 1, 3 ports export, then enter in reflection grating, the combination of circulator and matched FBG can the ASE noise that produces of filtering EDFA and backward Rayleigh scattering signal, the backward Brillouin scattering light that sensor fibre reflects through coupling mechanism 2 by the pulsed optical signals after denoising and local frequency displacement light carry out the relevant detection of light, and be transformed into electric signal by photodetector, then mixing is carried out with microwave local oscillation, down-converted is carried out to this electric signal, after carrying out filtering to this signal, finally by by spectrum analyzer analyser, AD data acquisition, reflects frequency shift amount by spontaneous Brillouin and converts corresponding temperature and STRESS VARIATION amount to, display translation on graphic interface.Detect the process of output light through associated op-tics of light generating device, be transformed into the pulsed light that polarization state is consistent, be connected to the first port of the first optical circulator, second port of the first optical circulator and Raman fiber lasers are connected to wavelength division multiplexer respectively through the output terminal of AOM, 3rd port of the first optical circulator is connected to the first port of the second optical circulator by the first fiber grating, second port of the second optical circulator connects the second fiber grating, 3rd port of the second optical circulator is by the 3rd fiber grating, the Brillouin scattering reflected by sensor fibre through coupling mechanism and local frequency displacement light carry out the relevant detection of light, extract backward Brillouin scattering signal.In above device, wherein the length of the first sensor fibre is not more than 50km, and the length of the second sensor fibre is not more than 50km.First fiber grating is identical with the wavelength of detection light generating device with the centre wavelength of the 3rd fiber grating, and bandwidth is not more than 0.2nm.The centre wavelength of the second fiber grating is identical with the wavelength of detection light generating device, and bandwidth is 1-2nm.
See Fig. 2, in order to verify effect of the present invention, it is long that first sensor fibre gets 45km, it is long that second sensor fibre gets 43.2km, and heating arrangement is added in the second sensor fibre, heating arrangement is arranged on the 39.4-42.6km place of the second sensor fibre, amounts to 3.2km, and by heating temperatures to about 80 DEG C.The wavelength of Raman fiber lasers gets 1480nm, the wavelength of direct impulse module gets 1535nm, the light that Raman fiber lasers and direct impulse module send respectively is by being coupled into 45km sensor fibre after wavelength division multiplexer, can decay gradually along with the increase of distance sensing when light transmits in sensor fibre, at sensor fibre 45km place, the sensor fibre of rear end will be connected to after optical signal amplification by EDFA, after light signal after amplification continues transmission 39.4km in a fiber, by the sensor fibre of the 3.2km of heating devices heat rear end, light signal is by after this section of optical fiber, finally enter tail end the sensor fibre of 0.6km, to spontaneous brillouin scattering signal after all producing when light signal transmits in each section of optical fiber, 3 ports from circulator 1 export by this signal, when backscatter signal enters circulator 2, the centre wavelength of FBG1 and FBG3 is 1534.9nm, bandwidth is 0.2nm, these two FBG can Rayleigh scattering light in filtering backscatter signal, and spontaneous brillouin scattering light is passed through, the centre wavelength of FBG2 is 1534.96nm, bandwidth is 1nm, the spontaneous Raman noise of the amplification produced by Raman pump can by FBG2 filtering, after 3 FBG, spontaneous brillouin scattering signal will pass through heterodyne disposal route, extract brillouin scattering signal, experimental result of the present invention and analysis are to such as Fig. 3, shown in 4.
The backward Brillouin scattering signal amplitude near sensor fibre heating region that Fig. 3 obtains for adopting the present invention, on the position of sensor fibre 84.4km ~ 87.6km, clearly can observe the amplitude change of backward Brillouin scattering signal, near sensor fibre 87km, the temperature resolution of BOTDR system is about 5.7 DEG C.
Three curves in Fig. 4 represent the employing temperature resolution of BOTDR system that obtains of three kinds of methods as illustrated in the drawing respectively, the power keeping direct impulse light is 20mw or 100mv, when not adding light amplification obtain BOTDR system temperature resolution be all low-down, and along with the increase of sensor fibre distance, the temperature resolution of system declines quickly, and adopt the inventive method obtain the increase of temperature resolution along with distance sensing, decline slowly, be conducive to significantly strengthening system performance, improve the temperature resolution of remote BOTDR system.
Claims (6)
1. utilize distributed raman amplification and EDFA technology to improve a device for remote BOTDR system temperature resolution, it is characterized in that, comprise Raman fiber generating device of laser, direct impulse light generating device, wavelength division multiplexer, optical circulator, first fiber grating, second fiber grating, 3rd fiber grating, coupling mechanism, photodetector, first sensor fibre, second sensor fibre, first coupling mechanism, second coupling mechanism, one EDFA, electrooptic modulator, mixing filter, spectrum analyzer, AD data acquisition unit and display device, above-mentioned detection light generating device rear end adds optoisolator, and prevent reflected light from disturbing light source and damaging, the combination then entering optical attenuator and EDFA can amplify light intensity, meticulous regulating optical power, eventually passes Polarization Controller, acousto-optic modulator, optical signal modulation can be become low noise with the combination of matched FBG by circulator, the pulsed light that polarization direction is consistent, the output terminal of direct impulse light generating device connects the first port of the first optical circulator, second port of the first optical circulator is connected wavelength division multiplexer respectively with the output terminal of first sound-optic modulator, 3rd port of the first optical circulator connects the first port of the second optical circulator by the first fiber grating, second port of the second optical circulator connects the second fiber grating, 3rd port of the second optical circulator connects an input end of the second coupling mechanism by the 3rd fiber grating, wavelength division multiplexer connects the first coupling mechanism and separates a road light by an output terminal and is incorporated in electrooptic modulator, by the frequency of 11GHz, it is modulated, for generation of this flash of light preceding an earthquake after frequency displacement, and output to another input end of the second coupling mechanism, another output terminal of first coupling mechanism connects EDFA by the first sensor fibre, EDFA connects the second sensor fibre, after the output terminal connection photodetector of the second coupling mechanism, successively through mixing filter, spectrum analyzer, display device is connected after AD data acquisition unit.
2. device according to claim 1, is characterized in that, the length of the first described sensor fibre is not more than 50km.
3. device according to claim 1, is characterized in that, the length of the second described sensor fibre is not more than 50km.
4. device according to claim 1, is characterized in that, the first fiber grating is identical with the wavelength of detection light generating device with the centre wavelength of the 3rd fiber grating, and bandwidth is not more than 0.2nm.
5. device according to claim 1, is characterized in that, the centre wavelength of the second fiber grating is identical with the wavelength of detection light generating device, and bandwidth is 1-2nm.
6. device according to claim 1, it is characterized in that, described direct impulse light generating device comprises the detection light generating device, optoisolator, optical attenuator, the 2nd EDFA, Polarization Controller and the first sound-optic modulator that connect successively, described Raman fiber generating device of laser comprises the Raman fiber lasers and second sound-optic modulator that connect successively, and first sound-optic modulator and second sound-optic modulator keep synchro switch state.
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Address after: 410100 No. 39, Jian Shan Road, Changsha economic and Technological Development Zone, Hunan Co-patentee after: Changsha HCC HIDEN Technology Co., Ltd. Patentee after: GreatWall Information Industry Co., Ltd. Co-patentee after: Hunan the Great Wall Hai Dun Optical Fiber Technology Co., Ltd. Address before: 410100 No. 39, Jian Shan Road, Changsha economic and Technological Development Zone, Hunan Co-patentee before: Changsha HCC HIDEN Technology Co., Ltd. Patentee before: GreatWall Information Industry Co., Ltd. Co-patentee before: Hunan Haidun Optical Fiber Sensing Technology Engineering Laboratory Co., Ltd. |
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Effective date of registration: 20190814 Address after: 410205 A076, Headquarters Building of Zhongdian Software Park, 39 Jianshan Road, Changsha High-tech Development Zone, Changsha City, Hunan Province Patentee after: Hunan the Great Wall Hai Dun Optical Fiber Technology Co., Ltd. Address before: 410100 No. 39 Jianshan Road, Changsha Economic and Technological Development Zone, Hunan Province Co-patentee before: Changsha HCC HIDEN Technology Co., Ltd. Patentee before: GreatWall Information Industry Co., Ltd. Co-patentee before: Hunan the Great Wall Hai Dun Optical Fiber Technology Co., Ltd. |
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