CN104019760A - Sensitivity enhancement demodulation method and device of fiber optical Bragg grating strain sensor - Google Patents
Sensitivity enhancement demodulation method and device of fiber optical Bragg grating strain sensor Download PDFInfo
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Abstract
The invention relates to a sensitivity enhancement demodulation method and device of a fiber optical Bragg grating strain sensor and belongs to the technical field of optical detection devices. The method comprises the following steps: outputting original laser which is as the same as resonant wavelength of FBG (Fiber Bragg Grating) and changes synchronously in real time by an optical fiber laser as pump light; after combining the pump light and signal laser at another wavelength, carrying out chirped amplification of frequency in a non-linear system to realize high order four-wave mixing; and finally, realizing high sensitivity detection of wavelength drift and corresponding strain of the original laser through wavelength analysis of idle light. According to the invention, sensor demodulation with high strain sensitivity can be obtained at wavelength near 1550nm, and high strain sensitivity which is higher than intrinsic sensitivity of FBG can be obtained in the demodulating process based on common FBG, so that the method and device provided by the invention are suitable for sense application of high strain sensitivity.
Description
Technical field
What the present invention relates to is a kind of device and method of optical detection apparatus technical field, specifically Sensitivity enhancement demodulation method and the device of a kind of bragg grating (FBG) strain transducer.
Background technology
In recent years, Fibre Optical Sensor is due to its radioresistance, anti-interference, anticorrosive, low-cost, microminiature, the advantage such as pollution-free, safe and reliable, in field widely, is applied.Especially, adopt the Fibre Optical Sensor of FBG can realize highly sensitive temperature, strain measurement, thereby can monitor, build for high temperature the deformation detection etc. of health monitoring, security against fire monitoring, dam bridge.
In general, the bragg grating of employing conventional single mode fiber can access the strain sensitivity [B.Lee of 1pm/ μ ε, " Review of the present status of optical fiber sensors, " Opt.Fiber Technol.9,57 ?79 (2003)].The strain-responsive of bragg grating comes from the change of grid cycle in the change of index modulation of grating and optical fiber, for strain, is mainly to change grid cycle.Therefore, by changing the material of optical fiber, or optical fiber structure, even fiber grating write method processed, can improve to a certain extent the strain sensitivity of fiber grating.Such as at document [F.Gu, H.Yu, W.Fang, and L.Tong. " Nanoimprinted polymer micro/nanofiber Bragg gratings for high ?sensitive strain sensing. " IEEE Photon.Technol.Lett.25,22 ?24 (2013)] in, the people such as F.Gu adopt the method for writing fiber grating processed on micro-nano fiber, can obtain the temperature control of 2pm/ μ ε left and right, than the strain sensitivity of general single mode fiber grating, increase.Notice, similar pretreated method need to adopt special optical fiber structure or material, or the special pre-service of carrying out that need to be to fiber grating, and tends to make reliability, the bad stability of sensor, and makes complicatedly, and cost also improves.So for obtaining highly sensitive strain sensing, we more wish to realize by aftertreatment, thereby without optical fiber head is carried out to pre-service.
Document [B.P. ?P.Kuo and Stojan Radic, " Fast wideband source tuning by extra ?cavity parametric process; " Opt.Express18,19930 ?19940 (2010)] in, the technology that the people such as B.KUO adopt full light signal to process has realized the amplification of frequency chirp, and the amplification by frequency chirp can contribute to improve the strain-responsive of the resonance wavelength drift of bragg grating.
Through the retrieval of prior art is found, Chinese patent literature CN103759855A open (bulletin) day 2014.04.30, disclose a kind of temperature-sensing system with Fiber Bragg Grating FBG, it comprises: light source, optical fiber circulator, one or more optical fiber FBG sensor, coupling mechanism, optical fiber, collimation lens, photorefractive hologram grating, focal imaging lens, imaging device, processor.This technology is introduced temperature survey field by fiber Bragg grating sensor, based on light signal, carry out transmission information, there is anti-electromagnetic interference (EMI), anticorrosive, high temperature resistant, high pressure resistant long service life, and good stability, highly sensitive, resolution is high, and can obtain from all spectrum on same passage simultaneously.But this sensing system adopts traditional FBG reflection demodulation method, on the one hand its spectral width, low precision; On the other hand, its detection be temperature sensing, and the sensitivity of its sensor is to have FBG intrinsic properties to determine, the existing industry of more difficult adaptation needs.
Chinese patent literature CN102589439A open (bulletin) day 2012.07.18, discloses the noninductive three-dimensional detection sensor of a kind of contact temperature based on Fiber Bragg Grating FBG and has belonged to exact instrument manufacture and precision measurement field of measuring techniques, this sensor comprises by pump laser, WDM coupling mechanism, the wide frequency light source system that Er-doped fiber and beam splitter form, by EDFA, the first circulator, conduit, temperature-compensated system with reference to FBG and optical fiber obstructing instrument composition, probe and by spectroanalysis instrument, the receiving system assembling that fiber coupler and index-matching fluid form forms, the reference FBG of temperature-compensated system is placed in probe space length 30cm, this technology has realized three-dimensional sensing, increased substantially the adaptive faculty of sensor to environment, have simple in structure, real-time is good, be easy to the feature of practical application, small inner cavity size is being implemented fast, in ultraprecise testing and calibration, there is significant advantage.But the temperature control sensing characteristics that its intrinsic of this technology is limited, with and the low precision that causes of the wide range of traditional demodulation structure.The sensing system of describing based on the document, its sensitivity is still to be determined by FBG intrinsic properties, and it is a temperature-sensing system, but not strain sensing system.
Summary of the invention
The present invention is directed to the deficiency of the limited sensitivity of existing bragg grating strain transducer, a kind of Sensitivity enhancement demodulation method and device of bragg grating strain transducer are proposed, by adopting full light signal, process the efficient amplification that realizes frequency chirp, realization is at the high sensitivity strain sensing demodulation of common single mode bragg grating, the strain sensitivity beening significantly enhanced on the basis of ordinary optic fibre grating.And the present invention is by the transmission-type FBG Optical Maser System of circulator structure, can obtain the FBG laser of arrowband, this device can obtain the sensing and demodulating of high strain sensitivity near 1550nm wavelength, can be on the basis of common FBG, by the process of demodulation, significantly improve the strain sensing sensitivity of system, thereby be applicable to the Application in Sensing of high strain sensitivity.
The present invention is achieved by the following technical solutions:
The present invention relates to a kind of Sensitivity enhancement demodulation method of bragg grating strain transducer, the original laser of exporting the identical and synchronous real-time change of resonance wavelength with FBG wherein by fiber laser is as pump light; After the signal laser of this pump light and another wavelength is merged, in nonlinear system, carry out frequency chirp amplification, realize high-order four-wave mixing; Finally by the analysis of ideler frequency light wavelength, realize the wave length shift of original laser and the high-sensitivity detection of corresponding strain.
Described bragg grating is for the narrow-band filtering of fiber laser.
Described merging refers to: pump light and signal laser are amplified to be input to through high power and in nonlinear optical fiber, carry out frequency chirp amplification.
Described catoptron can encircle mirror, circulator ring mirror or faraday rotation mirror for 3dB;
The wavelength of described FBG is positioned at 1550 ± 1nm, and reflectivity is not higher than 70%;
Described pump laser output wavelength 980nm or 1480nm, the laser output power that obtains FBG laser instrument is not less than 10mW;
Described high-order four-wave mixing realizes by nonlinear optical fiber, this nonlinear optical fiber can adopt but be not limited to soft glass optical fiber or the chalcogenide fiber of the doping of Ge-doped highly nonlinear optical fiber, bismuth, fiber lengths is not less than 200m, and nonlinear factor is not less than 10/W/km.
Described high-order four-wave mixing is the cascade high-order four-wave mixing of single-stage or multistage high-order four-wave mixing or round structure or the cascade high-order four-wave mixing of multistage round structure.
Described wavelength analysis adopts wavemeter, spectrometer or other optical wavelength determination and analysis instruments to realize.
The multiplying power that described frequency chirp amplifies is not less than 5 times, and strain sensitivity is not less than 5pm/ μ ε.
The present invention relates to realize the device of said method, comprise: the circulator being connected in series successively, Er-doped fiber, wavelength division multiplexer and the single-frequency laser being connected in series successively, Polarization Controller, coupling mechanism and at least Erbium-Doped Fiber Amplifier (EDFA) and the nonlinear optical fiber thereof of one-level, wherein: the output terminal of wavelength division multiplexer is connected with the two ends of bragg grating with the second port as the first port of this device respectively with the input end of coupling mechanism, the input end of wavelength division multiplexer is provided with the pump laser of 980nm, and the output terminal of nonlinear optical fiber is provided with spectroanalysis instrument
When adopting the Erbium-Doped Fiber Amplifier (EDFA) of multistage at least one-level and nonlinear optical fiber thereof, the input end at rear class Erbium-Doped Fiber Amplifier (EDFA) is provided with array waveguide grating.
Between described Erbium-Doped Fiber Amplifier (EDFA) and nonlinear optical fiber, be provided with optical filter.
Technique effect
Compared with prior art, technique effect of the present invention comprises:
1) adopt the non-linear full light signal amplifying based on frequency chirp to process and can in the sensor demodulating process of output terminal, to transducing signal, carry out aftertreatment, do not relate to sensing head, in realization, be more prone to, and stable, the safe operation that can keep sensing head, actual effect is the upgrading of sensor performance;
2) based on enhanced fiber grating strain sensing and demodulating technology of the present invention, can on the basis of ordinary optic fibre grating, not carry out any optical fiber head change, obtain being not less than 5pm/ μ ε strain sensitivity;
3) based on demodulation method of the present invention, can realize the demodulation that strain sensitivity effectively strengthens to polytype fiber grating, based on more high performance frequency chirp, amplify and light signal processing, can access the Sensitivity enhancement of larger double amplitude;
4) based on demodulation method of the present invention when strengthening strain sensitivity, can improve the strain resolution of system, the limited demodulation accuracy for specific wavelength analyser, can obtain more high-precision strain measurement.
Accompanying drawing explanation
Fig. 1 is structural representation of the present invention;
Fig. 2 is the system construction drawing of the FBG strain transducer Sensitivity enhancement demodulation method in embodiment;
Fig. 3 is the system construction drawing of the FBG strain transducer Sensitivity enhancement demodulation method in embodiment;
In figure: EDF: Er-doped fiber, EDFA: Erbium-Doped Fiber Amplifier (EDFA), CIR: circulator, WDM: wavelength division multiplexer, PUMP:980nm pump laser, PC: Polarization Controller, OC: coupling mechanism, BPF: optical filter, LD: single-frequency laser, HNLF: highly nonlinear optical fiber, OSA: spectroanalysis instrument, AWG: array waveguide grating, FBG bragg grating.
Embodiment
Below embodiments of the invention are elaborated, the present embodiment is implemented take technical solution of the present invention under prerequisite, provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.
Embodiment 1
As illustrated in fig. 1 and 2, for the Fibre Optical Sensor demodulating system described in the present embodiment comprises: the circulator CIR being connected in series successively, Er-doped fiber EDF, wavelength division multiplexer WDM and the single-frequency laser LD being connected in series successively, Polarization Controller PC, the erbium-doped optical fiber amplifier EDFA of coupling mechanism OC and at least one-level and nonlinear optical fiber HNLF thereof, wherein: the input end of the output terminal of wavelength division multiplexer WDM and coupling mechanism OC is connected with the two ends of bragg grating FBG with the second port as the first port of this device respectively, the input end of wavelength division multiplexer WDM is provided with 980nm pump laser PUMP, the output terminal of nonlinear optical fiber HNLF is provided with spectroanalysis instrument OSA
Between described erbium-doped optical fiber amplifier EDFA and nonlinear optical fiber HNLF, be provided with optical filter BPF.
According to the present embodiment: erbium-doped fiber is by 980nm laser pumping, spontaneous emission light one end of institute's radiation is reflected by the tore of reflection mirror of circulator structure, the other end connects FBG, FBG has 50% reflectivity, thereby in FBG resonance wavelength position, obtain a part of antireflection part transmission, the transmission end Output of laser of FBG.The optical maser wavelength of exporting is in full accord with the resonance wavelength of FBG.
The laser of the single-frequency laser output of Output of laser and another wavelength combines, and is coupled to Erbium-Doped Fiber Amplifier, by being input to highly nonlinear optical fiber after wave filter.The output power of Erbium-Doped Fiber Amplifier is 500mW, and the length of highly nonlinear optical fiber is 500m, and nonlinear factor is 11/W/km, and zero-dispersion wavelength is in 1550nm.
The wavelength of FBG laser instrument of take is pump light, and single-frequency laser is flashlight, through the high-order four-wave mixing of single-stage, produces the ideler frequency light of high-order, and ideler frequency light wavelength has the response of synchronizeing with the resonance wavelength of FBG, but response amplitude is amplified by double amplitude.Embodiment 2
As shown in Figure 3, structural drawing for the Fibre Optical Sensor demodulating system described in the present embodiment, when adopting the erbium-doped optical fiber amplifier EDFA of multistage at least one-level and nonlinear optical fiber HNLF thereof, the input end at rear class erbium-doped optical fiber amplifier EDFA is provided with array waveguide grating AWG.
According to the present embodiment: erbium-doped fiber is by 980nm laser pumping, spontaneous emission light one end of institute's radiation is reflected by the tore of reflection mirror of circulator structure, the other end connects FBG, FBG has 50% reflectivity, thereby in FBG resonance wavelength position, obtain a part of antireflection part transmission, the transmission end Output of laser of FBG.The optical maser wavelength of exporting is in full accord with the resonance wavelength of FBG.
The laser of the single-frequency laser output of Output of laser and another wavelength combines, and is coupled to Erbium-Doped Fiber Amplifier, by being input to highly nonlinear optical fiber after wave filter.Through after a four-wave mixing, pass through again AWG filtering, be then input to second highly nonlinear optical fiber.The output power of two Erbium-Doped Fiber Amplifier is as 500mW, and the length of highly nonlinear optical fiber is 500m, and nonlinear factor is 11/W/km, and zero-dispersion wavelength is in 1550nm.
In first order four-wave mixing process, the wavelength of FBG laser instrument of take is pump light, and single-frequency laser is flashlight, high-order four-wave mixing through single-stage, the ideler frequency light that produces high-order, ideler frequency light wavelength has the response of synchronizeing with the resonance wavelength of FBG, but response amplitude is amplified by double amplitude.Before the four-wave mixing of the second level, through AWG, leach a certain ideler frequency light of single-frequency laser wavelength or single-frequency laser wavelength one side, and the high-order ideler frequency light that leaches FBG optical maser wavelength one side, after amplifying through EDFA, enter second level four-wave mixing.Through the four-wave mixing of two-stage high-order, obtain larger frequency chirp and amplify double amplitude, obtain higher strain sensitivity.
Claims (9)
1. a Sensitivity enhancement demodulation method for bragg grating strain transducer, is characterized in that, the original laser of exporting the identical and synchronous real-time change of resonance wavelength with FBG wherein by fiber laser is as pump light; After the signal laser of this pump light and another wavelength is merged, in nonlinear system, carry out frequency chirp amplification, realize high-order four-wave mixing; Finally by the analysis of ideler frequency light wavelength, realize the wave length shift of original laser and the high-sensitivity detection of corresponding strain;
Described bragg grating is for the narrow-band filtering of fiber laser;
Described merging refers to: pump light and signal laser are amplified to be input to through high power and in nonlinear optical fiber, carry out frequency chirp amplification; The multiplying power that described frequency chirp amplifies is not less than 5 times, and strain sensitivity is not less than 5pm/ μ ε.
2. method according to claim 1, is characterized in that, described catoptron is 3dB ring mirror, circulator ring mirror or faraday rotation mirror.
3. method according to claim 1, is characterized in that, the wavelength of described FBG is positioned at 1550 ± 1nm, and reflectivity is not higher than 70%.
4. method according to claim 1, is characterized in that, described pump laser output wavelength 980nm or 1480nm, and the laser output power that obtains FBG laser instrument is not less than 10mW.
5. method according to claim 1, is characterized in that, described high-order four-wave mixing realizes by nonlinear optical fiber,
This nonlinear optical fiber can adopt but be not limited to soft glass optical fiber or the chalcogenide fiber of the doping of Ge-doped highly nonlinear optical fiber, bismuth, and fiber lengths is not less than 200m, and nonlinear factor is not less than 10/W/km.
6. method according to claim 1, is characterized in that, described high-order four-wave mixing is the cascade high-order four-wave mixing of single-stage or multistage high-order four-wave mixing or round structure or the cascade high-order four-wave mixing of multistage round structure.
7. a device of realizing method described in above-mentioned arbitrary claim, it is characterized in that, comprise: the circulator being connected in series successively, Er-doped fiber, wavelength division multiplexer and the single-frequency laser being connected in series successively, Polarization Controller, the Erbium-Doped Fiber Amplifier (EDFA) of coupling mechanism and at least one-level and nonlinear optical fiber thereof, wherein: the output terminal of wavelength division multiplexer is connected with the two ends of bragg grating with the second port as the first port of this device respectively with the input end of coupling mechanism, the input end of wavelength division multiplexer is provided with the pump laser of 980nm, the output terminal of nonlinear optical fiber is provided with spectroanalysis instrument.
8. device according to claim 7, is characterized in that, when adopting the Erbium-Doped Fiber Amplifier (EDFA) of multistage at least one-level and nonlinear optical fiber thereof, the input end at rear class Erbium-Doped Fiber Amplifier (EDFA) is provided with array waveguide grating.
9. device according to claim 7, is characterized in that, between described Erbium-Doped Fiber Amplifier (EDFA) and nonlinear optical fiber, is provided with optical filter.
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Cited By (3)
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| CN105352446A (en) * | 2015-11-30 | 2016-02-24 | 上海交通大学 | Sub-nano strain level multi-point multiplexing fiber grating quasi static strain sensor system |
| CN110620331A (en) * | 2019-09-26 | 2019-12-27 | 哈尔滨工业大学 | DFB array high-speed large-range continuous tunable method |
| RU2771446C1 (en) * | 2021-07-06 | 2022-05-04 | Акционерное общество "Концерн "Центральный научно-исследовательский институт "Электроприбор" | Sensing element of a fiber-optic strain gauge for measuring longitudinal mechanical tension and a method for measuring the longitudinal mechanical tension of an object with a fiber-optic strain gauge |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105352446A (en) * | 2015-11-30 | 2016-02-24 | 上海交通大学 | Sub-nano strain level multi-point multiplexing fiber grating quasi static strain sensor system |
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| RU2771446C1 (en) * | 2021-07-06 | 2022-05-04 | Акционерное общество "Концерн "Центральный научно-исследовательский институт "Электроприбор" | Sensing element of a fiber-optic strain gauge for measuring longitudinal mechanical tension and a method for measuring the longitudinal mechanical tension of an object with a fiber-optic strain gauge |
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