CN102620761A - Long-distance optical fiber Bragg grating sensing method and device based on self-heterodyne detection - Google Patents
Long-distance optical fiber Bragg grating sensing method and device based on self-heterodyne detection Download PDFInfo
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- CN102620761A CN102620761A CN2012100986026A CN201210098602A CN102620761A CN 102620761 A CN102620761 A CN 102620761A CN 2012100986026 A CN2012100986026 A CN 2012100986026A CN 201210098602 A CN201210098602 A CN 201210098602A CN 102620761 A CN102620761 A CN 102620761A
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Abstract
The invention relates to a long-distance optical fiber Bragg grating sensing method and device based on self-heterodyne detection. A single frequency light beam sent from a wavelength adjustable narrow line width laser is split into two parts of light beam with the same intensity after passing through a triport optical fiber coupler, one part of the light beam passes through a scrambler and is used as an intrinsic light, and the other part of the light beam passes through a light pulse modulation module and is modulated into a pulse detection light; and the detection pulse light passes through an optical isolator, enters a segment of a long-distance transmission optical fiber, and then enters a sensing optical fiber grating array through a far-end light circulator; and the signal reflected from the optical fiber grating shifts frequency of the returned reflection sensing signal through a frequency shift module and then enters a four-port optical coupler together with the intrinsic light, and the generated coherent light signal enters a balance photoelectric detector through the other two ports of the optical coupler and is converted to an electrical signal. The electrical signal received and converted by a signal collection analysis and control module is collected and analyzed to obtain the time domain track of the sensing signal, and the peak power is the power of the coherent signal.
Description
Technical field
The invention belongs to field of sensing technologies; Related to and a kind ofly improved detection sensitivity and combine adjustable wavelength laser and eliminate the method for the remote recording of Rayleigh scattering structure dorsad, promptly remote optical fiber Bragg grating sensing method and the equipment of realizing this method based on the self-heterodyne Detection Techniques.
Background technology
Fiber Bragg Grating FBG (FBG) has advantages such as high sensitivity, anti-electromagnetic interference (EMI), simple in structure and high resolving power, has caused that in the application of sensory field people pay attention to greatly.In practical application, the fiber bragg grating sensing device of long distance can be widely used in various fields such as oil pipeline, transformer station.Because the influence of the factors such as loss of Rayleigh scattering and optical fiber when carrying out the research of fiber bragg grating sensing device with wideband light source, can only be transmitted 25km farthest.Therefore, the distance sensing that how to improve FBG has become to press for the problem of solution.In in the past several years, scientists has proposed a lot of methods and has improved distance sensing, but the image intensifer that these methods are generally used.Along with the further increase of distance sensing, the pump power of amplifier just needs further to improve, and when pump power surpasses certain threshold value, will produce and be excited effect.And the increase of input optical power also can cause the increase of Rayleigh scattering dorsad, influences signal to noise ratio (S/N ratio).In order to address these problems, sensing device just needs extra increase device, makes complexity further strengthen.This will limit the practical ranges of sensing device.
Except improving input optical power, improving detection efficiency is the another kind of effective ways that increase distance sensing.The heterodyne detection technology can improve detection sensitivity greatly, thereby improves detection efficiency.With the direct detection compared with techniques, the heterodyne detection technology can reach the limit that light quantum is surveyed.Use heterodyne detection technology and combination and eliminate the special construction of Rayleigh scattering light dorsad, can effectively reduce the sensing device complexity, improve signal to noise ratio (S/N ratio), increase distance sensing.
Summary of the invention
The object of the invention is exactly the deficiency to prior art; Propose a kind of based on the self-heterodyne Detection Techniques and combine the wavelength tunable laser source with eliminate the remote optical fiber Bragg grating sensing method of Rayleigh scattering structure dorsad, the equipment of realizing this method is provided simultaneously.
Its technical solution is: the narrow linewidth laser that adopts a wavelength-tunable is as light source, and with its emitted light beams separated into two parts, a part is as local reference light, and another part is modulated into pulse detection light; The optical fiber that uses two segment length identical (or similar) is surveyed the passage of light and reflection sense flashlight respectively as transmission, and the reflection sense flashlight that returns is carried out shift frequency; Reflection sense flashlight behind the shift frequency and local reference light are carried out the self-heterodyne detection, just can draw the peak power of coherent signal; Change the output light wavelength of tunable laser, just can obtain the pairing signal power of each wavelength, thereby draw out the reflectance spectrum of sensor fibre grating array; Because the bragg wavelength of sensor fibre grating array changes with sensing quantitative changeizations such as temperature, stress, the therefore variation that just can draw the sensing amount with the relation of wavelength change of variation and the sensing amount through bragg wavelength.
The device of realizing such scheme comprises narrow linewidth laser, three port 3dB photo-couplers, scrambler, light pulse modulation module, the optoisolator of wavelength-tunable, long-distance optical fiber, optical circulator, sensor fibre bragg grating array, shift frequency module, four port 3dB photo-couplers, balance photodetector, signal processing and analysis and the control module of two segment length identical (or similar).The light output end of tunable laser is connected with the port of the single port end of three port three-dB couplers; The port of the dual-port end of three port three-dB couplers and the input port of scrambler are connected, and another port is connected with the input port of light pulse modulation module; The output port of light pulse modulation module is connected with the input port of optoisolator; The output port of optoisolator is connected through the incident port one of a long distance Transmission Fibers and optical circulator; The transmission port 2 of circulator is connected with the sensor fibre grating array, and reflector port 3 is connected through the input port of another long distance optical fiber and shift frequency module; Two input port homonymies of four port 3dB photo-couplers are connected with the output port of shift frequency module, the output port of scrambler respectively; Two output port homonymies of four port 3dB photo-couplers are connected with the input port of balance photodetector, and the output port of detector is connected with the input port of signal processing and analysis and control module; The GPIO mouth of the control port of signal processing and analysis and control module and adjustable wavelength laser is connected.
The present invention utilizes the self-heterodyne Detection Techniques to realize the detection of faint transducing signal; Improved detection efficiency, the distance sensing of increase, and combine the wavelength tunable laser source; Method through the scanning output light wavelength; Draw out sensor fibre grating reflection spectrum, the bragg wavelength that has obtained fiber grating accurately changes, and then obtains the variation of sensing amount.In addition, the present invention adopts special construction, has eliminated dorsad Rayleigh scattering to the influence of transducing signal.The inventive method can realize the optical fiber grating sensing of longer distance under identical input optical power; It is strong to have antijamming capability; Simple in structure; Control advantages such as convenient, and can realize the detection of a plurality of fiber gratings and different sensing amounts simultaneously, be highly suitable for detecting rugged surroundings such as earthquake, tsunami, transformer station and oil pipeline.
Description of drawings
Fig. 1 is a structural representation of the present invention.
Embodiment
As shown in Figure 1, a kind of remote optical fiber Bragg grating sensing device based on the self-heterodyne Detection Techniques comprises long-distance optical fiber 6 and 9, optical circulator 7, sensor fibre Bragg grating 8, shift frequency module 10, four port three-dB couplers 11, balance photodetector 12, signal processing and analysis and the control module 13 of adjustable wavelength laser 1, three port 3dB photo-couplers 2, scrambler 3, light pulse modulation module 4, optoisolator 5, two segment length identical (or similar) of narrow linewidth.The output port of adjustable wavelength laser 1 is connected with the port of the single port end of three port 3dB photo-couplers 2; The port of the dual-port end of three port 3dB photo-couplers 2 and the input port of scrambler 3 are connected, and another port of the dual-port end of coupling mechanism 2 is connected with the input port of light pulse modulation module 4; The output port of light pulse modulation module 4 is connected with the input port of optoisolator 5; The output port of long-distance optical fiber 6 one ends and optoisolator 5 is connected, and the incident port of the other end and optical circulator 7 is connected; The transmission port of optical circulator 7 is connected with sensor fibre grating array 8; One end of another long distance optical fiber 9 is connected with the reflector port of optical circulator 7, and the other end is connected with the input port of shift frequency module 10; Two input port homonymies of four port 3dB photo-couplers 11 are connected with the output port of shift frequency module 10, the output port of scrambler 3 respectively; Two output port homonymies of four port 3dB photo-couplers 11 are connected with two light input end mouths of balance photodetector 12 respectively; The input port of signal processing and analysis and control module 13 is connected with the electric output port of balance photodetector 12, and the GPIO mouth of the control port of signal processing and analysis and control module 13 and the narrow linewidth laser 1 of wavelength-tunable is connected.
Concrete remote optical fiber grating sensing method may further comprise the steps:
The single-frequency light beam that the narrow linewidth laser of step (1) wavelength-tunable sends is divided into two parts light beam that intensity equates after through three port 3dB fiber couplers, and a part is through scrambler, the intrinsic light of surveying as self-heterodyne; Another part light beam is modulated into pulse detection light through the light pulse modulation module.Wherein scrambler is in order to eliminate the influence of polarization state to measurement result.
Step (2) direct impulse light enters into a long distance Transmission Fibers after through optoisolator, and incident port one and the transmission port 2 through the far-end optical circulator enters into the sensor fibre grating array then.The signal that fiber grating reflects gets into another long distance Transmission Fibers through the transmission port 2 of distal annular rim device with reflector port 3.Wherein the effect of optoisolator is the influence that protection light pulse modulation module is avoided the Rayleigh scattering light dorsad in the Transmission Fibers.Use two sections optical fiber to transmit the direct impulse signal respectively and the reflection sense signal is that in the practical application, the length of two sections Transmission Fibers will be consistent for fear of Rayleigh scattering light is to the influence of transducing signal dorsad.
Step (3) shift frequency module is carried out shift frequency to the reflection sense signal that returns, and gets into four port 3dB photo-couplers together with intrinsic light then, and the coherent light signal of generation converts electric signal to through two other port entering balance photodetector of coupling mechanism.Receive electrical signal converted by signal processing and analysis and control module; The centre frequency of signal processing and analysis and control module is arranged to the frequency shift amount of reflection sense signal; Just can draw the time domain track of transducing signal, the peak power of track is exactly the power of coherent signal; What the transverse axis of track was represented is the spontaneous mistiming that is mapped to reception of light signal, can be used for calculating the distance of fiber grating.
Step (4) is regulated the output light wavelength of laser instrument through signal processing and analysis and control module; Just can obtain the pairing signal power of each wavelength; Thereby draw out the reflectance spectrum of sensor fibre grating array, obtain the bragg wavelength of each fiber grating of optical fibre optical grating sensing array this moment.Because the bragg wavelength of sensor fibre grating array changes with sensing quantitative changeizations such as temperature, stress, the therefore variation that just can draw the sensing amount with the relation of wavelength change of variation and the sensing amount through bragg wavelength.Signal processing and analysis and control module not only can gather and analyze the variation of transducing signal and sensing amount but also can control the output light wavelength of tunable laser, had realized the automation mechanized operation of package unit, had improved operational efficiency.
Claims (3)
1. remote optical fiber Bragg grating sensing method of surveying based on self-heterodyne is characterized in that may further comprise the steps:
Be divided into two parts light beam that intensity equates behind the 3dB fiber coupler of single-frequency light beam through three ports that the narrow linewidth laser of step (1) wavelength-tunable sends, a part is through scrambler, as the intrinsic light of self-heterodyne detection; Another part light beam is modulated into pulse detection light through the light pulse modulation module;
Step (2) direct impulse light enters into a long distance Transmission Fibers after through optoisolator, and incident port one and the transmission port 2 through the far-end optical circulator enters into the sensor fibre grating array then; The signal that fiber grating reflects gets into another long distance Transmission Fibers through the transmission port 2 of distal annular rim device with reflector port 3, realizes separating of incoming signal and reflection sense signal;
Step (3) shift frequency module is carried out shift frequency to the reflection sense signal that returns, and gets into four port 3dB photo-couplers together with intrinsic light then, and the coherent light signal of generation converts electric signal to through two other port entering balance photodetector of photo-coupler; Receive electrical signal converted by signal processing and analysis and control module; The centre frequency of signal processing and analysis and control module is arranged to the frequency shift amount of reflection sense signal; Just can see the time domain track of transducing signal, the peak power of track is exactly the power of coherent signal; What the transverse axis of track was represented is the spontaneous mistiming that is mapped to reception of light signal, can be used for calculating the distance of fiber grating; Step (4) is regulated the output light wavelength of laser instrument through signal processing and analysis and control module; Just can obtain the pairing signal power of each wavelength; Thereby draw out the reflectance spectrum of sensor fibre grating array, obtain the bragg wavelength of each fiber grating of sensor fibre grating array this moment; The bragg wavelength of sensor fibre grating array changes with temperature, stress sensing quantitative changeization, the therefore variation that just can draw the sensing amount with the relation of wavelength change of variation and the sensing amount through bragg wavelength; Signal processing and analysis and control module had not only been gathered and had been analyzed the variation of transducing signal and sensing amount but also controlled the output light wavelength of tunable laser.
2. the remote optical fiber Bragg grating sensing method of surveying based on self-heterodyne as claimed in claim 1 is characterized in that the length of two sections Transmission Fibers will be consistent.
3. remote according to claim 1 fiber bragg grating sensing device; Comprise the adjustable wavelength laser, three port 3dB photo-couplers, scrambler, light pulse generating module, optoisolator of narrow linewidth, long Distance Transmission optical fiber, optical circulator, sensor fibre grating array, shift frequency module, four port 3dB photo-couplers, balance photodetector, signal processing and analysis and the control module that two segment length are identical or close, it is characterized in that: the light output end of tunable laser is connected with the single port end of three port three-dB couplers; The port of the dual-port end of three port 3dB photo-couplers and the input port of scrambler are connected, and another port is connected with the input port of light pulse generating module; The output port of light pulse generating module is connected with the input port of optoisolator; The output port of optoisolator is connected through the incident port one of a long distance Transmission Fibers and optical circulator; The transmission port 2 of circulator is connected with the sensor fibre grating array, and reflector port 3 is connected through the input port of another long distance optical fiber and shift frequency module; Two input port homonymies of four port 3dB photo-couplers are connected with the output port of shift frequency module, the output port of scrambler respectively; Two output port homonymies of four port 3dB photo-couplers are connected with the input port of balance photodetector, and the output port of detector is connected with the input port of signal processing and analysis and control module; The GPIO mouth of the control port of signal processing and analysis and control module and adjustable wavelength laser is connected.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106500742A (en) * | 2016-12-30 | 2017-03-15 | 中国电子科技集团公司第三十四研究所 | A kind of phase sensitive optical time domain reflectometer phase demodulating system and phase demodulating method |
| CN106768268A (en) * | 2016-11-18 | 2017-05-31 | 电子科技大学 | The optical fiber vibration sensing system that a kind of low reflection oblique raster array is combined with Φ OTDR |
| CN110487308A (en) * | 2019-08-27 | 2019-11-22 | 南京大学 | A kind of high-performance coherent detection type Φ-OTDR realization system and method based on PGC demodulation |
| GB2550774B (en) * | 2015-03-06 | 2021-08-04 | Silixa Ltd | Method and apparatus for optical sensing |
| CN113447112A (en) * | 2021-06-18 | 2021-09-28 | 天津大学 | Reflected light-based high-frequency vibration sensing system and high-frequency signal demodulation method |
| CN113835381A (en) * | 2021-09-26 | 2021-12-24 | 杭州翔毅科技有限公司 | Autonomous intelligent accurate sensing and control device and system for unmanned system |
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| WO2005024349A1 (en) * | 2003-09-08 | 2005-03-17 | Donam Systems Inc. | Fiber bragg grating sensor system |
| CN100504309C (en) * | 2007-09-30 | 2009-06-24 | 南京大学 | Brillouin optical time domain reflection measuring method based on quick fourier transform |
| CN102168953A (en) * | 2011-01-12 | 2011-08-31 | 南京大学 | Full-distributed optical fiber strain and vibration sensor based on coherent heterodyne detection |
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2012
- 2012-04-06 CN CN2012100986026A patent/CN102620761A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005024349A1 (en) * | 2003-09-08 | 2005-03-17 | Donam Systems Inc. | Fiber bragg grating sensor system |
| CN100504309C (en) * | 2007-09-30 | 2009-06-24 | 南京大学 | Brillouin optical time domain reflection measuring method based on quick fourier transform |
| CN102168953A (en) * | 2011-01-12 | 2011-08-31 | 南京大学 | Full-distributed optical fiber strain and vibration sensor based on coherent heterodyne detection |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2550774B (en) * | 2015-03-06 | 2021-08-04 | Silixa Ltd | Method and apparatus for optical sensing |
| US11719560B2 (en) | 2015-03-06 | 2023-08-08 | Silixa Ltd. | Method and apparatus for optical sensing |
| CN106768268A (en) * | 2016-11-18 | 2017-05-31 | 电子科技大学 | The optical fiber vibration sensing system that a kind of low reflection oblique raster array is combined with Φ OTDR |
| CN106500742A (en) * | 2016-12-30 | 2017-03-15 | 中国电子科技集团公司第三十四研究所 | A kind of phase sensitive optical time domain reflectometer phase demodulating system and phase demodulating method |
| CN106500742B (en) * | 2016-12-30 | 2018-08-28 | 中国电子科技集团公司第三十四研究所 | A kind of phase sensitive optical time domain reflectometer phase demodulating system and phase demodulating method |
| CN110487308A (en) * | 2019-08-27 | 2019-11-22 | 南京大学 | A kind of high-performance coherent detection type Φ-OTDR realization system and method based on PGC demodulation |
| CN113447112A (en) * | 2021-06-18 | 2021-09-28 | 天津大学 | Reflected light-based high-frequency vibration sensing system and high-frequency signal demodulation method |
| CN113835381A (en) * | 2021-09-26 | 2021-12-24 | 杭州翔毅科技有限公司 | Autonomous intelligent accurate sensing and control device and system for unmanned system |
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Application publication date: 20120801 |