CN205898164U - Fiber Bragg Grating Sensing System for Simultaneous Measurement of Temperature and Strain - Google Patents
Fiber Bragg Grating Sensing System for Simultaneous Measurement of Temperature and Strain Download PDFInfo
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- CN205898164U CN205898164U CN201620661245.3U CN201620661245U CN205898164U CN 205898164 U CN205898164 U CN 205898164U CN 201620661245 U CN201620661245 U CN 201620661245U CN 205898164 U CN205898164 U CN 205898164U
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Abstract
A fiber grating-based sensing system for simultaneous measurement of temperature and strain, comprising: the device comprises a detection light branch, a feedback detection branch, a polarization-maintaining optical coupler, a modulation circuit and a calculation circuit, wherein: the output end of the detection light branch is connected with the sensing grating, the reflection end of the sensing grating is sequentially connected with the polarization-maintaining optical coupler and the feedback detection branch, the output end of the modulation circuit is connected with the detection light branch, and the input end of the calculation circuit is connected with the feedback detection branch; the utility model discloses can show the measurement resolution who improves sampling rate and temperature, meet an emergency, realize higher demodulation precision.
Description
Technical field
The utility model relates to a kind of technology of sensory field of optic fibre, specifically one kind are for temperature with strain simultaneously
The fiber Bragg grating type sensor-based system of measurement.
Background technology
Phase shift optical fiber Bragg grating (ps fbg) is the mutation of traditional fiber Bragg grating (fbg).Due in refraction
The grating of rate periodic distribution introduces phase shift point, leads to certain certain wave strong point in its stopband to produce extremely narrow transmission window.
The centre wavelength of this transmission window is simultaneously sensitive with strain to temperature, and its sensitivity with the Bragg grating being not introduced into phase shift
Unanimously.
Polarization maintaining optical fibre introduces a birefringent type optical fiber by force as during design, and its fast axle has different refractions from slow axis
Rate.Both differences of refractive index and frequency-splitting corresponding thereto are equally linearly sensitive with strain to temperature, therefore, protect polarisation
Birefringence effect in fibre also apply be applicable to temperature or the strain sensing scene of correlation.
In high precision optical fiber grating sensory field, the paper (optics that d.gatti, g.galzerano etc. deliver
Express, vol.16, no.3, pp.1945 1950,2008) in propose high accuracy based on phase shift optical fiber Bragg grating
Strain transducer, but due to use only this group physical quantity of phase-shifted grating transmission window centre wavelength in this scheme, therefore no
Method eliminates grating itself and temperature strain is reported to the leadship after accomplishing a task the sensitive measure error being led to.And survey quantifier elimination neck in temperature strain simultaneously
In domain, the physical quantity different to two groups need to measure, really treated testing temperature and strain by solving two element equations.
M.sudo, m.nakai etc. are in its paper (12thinternational conference on optical
Fiber sensors, osa technical digest series, vol.16,170/owc7 1,1997) in propose and will protect
The scheme that simultaneously measures for temperature strain of traditional fiber grating on polarisation fibre, but result in because its demodulation accuracy is relatively low right
The measurement result precision of birefringence effect is poor, thus the resolution ratio better than 1 DEG C/10 μ ε cannot be realized.
Utility model content
The utility model is difficult to meet the defects such as requirement for prior art resolution ratio, proposes one kind and is used for temperature and strain
The fiber Bragg grating type sensor-based system simultaneously measuring, by the fast and slow axis transmissive window of the phase shift optical fiber Bragg grating on polarization maintaining optical fibre
The different center frequency of mouth, carries out high-precision demodulation, realizes temperature and measures with strain simultaneously.
The utility model is achieved through the following technical solutions:
The utility model is related to a kind of fiber Bragg grating type sensor-based system simultaneously measuring for temperature with strain, comprising: visit
Light-metering branch road, feedback detection branch, guarantor's polarisation coupler, modulation circuit and counting circuit, wherein: sensing grating one end is with guarantor partially
Photo-coupler is connected, and through going Fresnel reflection to process, the output end detecting light branch road is connected the other end with sensing grating, sense light
The reflection end of grid is sequentially connected guarantor's polarisation coupler and feedback detection branch, the output end of modulation circuit and detection light branch road phase
Even, the input of counting circuit is connected with feedback detection branch.
Described detection light branch road includes: the tunable laser that is sequentially connected, photo-coupler, optical phase modulator, light
Intensity modulator and the polarization maintaining optical fibre of 45 ° of spin weldings.
The optical signal that described tunable laser sends is divided into two bundles, a branch of entrance light phase modulation through photo-coupler
Device, a branch of entrance optical wavelengthmeter carries out wavelength readings.
Described feedback detection branch includes: two output ends of signal generator, polarization beam apparatus and polarization beam apparatus
The corresponding fast axle detection branch being connected and slow axis detection branch.
The input of described polarization beam apparatus is connected with the input protecting polarisation coupler, and two of polarization beam apparatus defeated
Go out end and correspond to the fast axle of sensing grating and the reflected signal of slow axis respectively.
Described fast axle detection branch is identical with slow axis detection branch structure, and the photodetector for series connection and locking are amplified
Device.
Described signal generator synchronously drives optical phase modulator and lock-in amplifier.
Described modulation circuit is radio-frequency signal generator.
Described radio-frequency signal generator drives light intensity modulator.
Described counting circuit is controlled to radio-frequency signal generator and reading by controlling bus.
Described computer is acquired to the data of lock-in amplifier, and the centre frequency to tunable laser and penetrating
The signal frequency of frequency signal generator is modified.
Described data is to detect two sidebands of light and the fast axle of corresponding sensing grating and slow axis transmission peak center
Two frequency discrimination signal.
Described sensing grating one end is connected with protecting polarisation coupler, and the other end is processed through removing Fresnel reflection.
Described sensing grating is the phase shift optical fiber Bragg grating on polarization maintaining optical fibre.
Technique effect
Compared with prior art, the utility model eliminates grating to temperature and strain based on the intrinsic physical effect of grating
The problem of cross sensitivity, is carried out the demodulation of double-side band detection, possesses higher than traditional optical using the closed loop configuration of frequency locker fixed pattern
The control accuracy of rf modulated signal frequency of mode and accuracy of reading, realize quickly measuring while temperature and strain, reach
10‐3DEG C temperature resolution and 10‐2The strain resolution of μ ε.
Brief description
Fig. 1 is optical fiber sensing system schematic diagram；
Fig. 2 is optical fiber sensing system principle schematic；
Fig. 3 is the spectrum schematic diagram of sensing grating；
In figure: (a) is fast axle, (b) is slow axis；
Fig. 4 is the emergent property curve that grating Bragg frequency and birefringence cause difference on the frequency；
Fig. 5 is the temperature characteristics that grating Bragg frequency and birefringence cause difference on the frequency；
Fig. 6 is the experimental result of embodiment；
In figure: (a) is the graph of a relation of the grating Bragg frequency and birefringence cause difference on the frequency recording, and (b) is to treat testing temperature
With strain stress relation figure；
In figure: 1 is tunable laser, 2 is photo-coupler, 3 is optical wavelengthmeter, 4 is radio-frequency signal generator, 5 is light
Phase-modulator, 6 be light intensity modulator, 7 be 45 ° of spin weldings polarization maintaining optical fibre, 8 be polarization beam apparatus, 9 be sense light
Grid, 10 be photodetector, 11 be lock-in amplifier, 12 be signal generator, 13 be counting circuit, 14 be protect polarisation coupling
Device.
Specific embodiment
Below embodiment of the present utility model is elaborated, the present embodiment is being front with technical solutions of the utility model
Put and implemented, give detailed embodiment and specific operating process, but protection domain of the present utility model does not limit
In following embodiments.
Embodiment 1
As shown in figure 1, the present embodiment includes: detect light branch road, feedback detection branch, protect polarisation coupler 14, modulation electricity
Road and counting circuit, wherein: the detection light detecting the double-side band intensity modulated of light branch road output passes through to input sensing grating 9, right
Transmission peak center in the fast axle and slow axis of sensing grating 9 is detected, and the reflected signal of sensing grating 9 passes through to protect polarisation coupling
Device 14 input feedback detection branch；The output end of modulation circuit is connected with detecting light branch road, counting circuit collection feedback detection
The data on road is modified to the frequency parameter of modulation circuit, forms two closed feedback loop, will detect two sidebands of light
It is locked in the corresponding transmission peaks of sensing grating 9, is calculated temperature and strain, show and store result.
Described detection light branch road includes: the tunable laser 1 that is sequentially connected, photo-coupler 2, optical phase modulator 5,
Light intensity modulator 6 and the polarization maintaining optical fibre 7 of 45 ° of spin weldings.
The optical signal that described tunable laser 1 sends is divided into two bundles through photo-coupler 2, and a branch of entrance light phase is adjusted
Device 5 processed, a branch of entrance optical wavelengthmeter 3 carries out wavelength readings.
It is defeated with two of polarization beam apparatus 8 that described feedback detection branch includes signal generator 12, polarization beam apparatus 8
Go out the corresponding fast axle detection branch being connected in end and slow axis detection branch, wherein: signal generator 12 regulation and control fast axle detection branch and
Slow axis detection branch.
The described input of polarization beam apparatus 8 is connected with the input protecting polarisation coupler 14, and the two of polarization beam apparatus 8
Individual output end corresponds to the fast axle of sensing grating 9 and the reflected signal of slow axis respectively.
Described fast axle detection branch is identical with slow axis detection branch structure, and photodetector 10 and locking for series connection are put
Big device 11.
Described signal generator 12 drives optical phase modulator 5 and lock-in amplifier 11.
Described modulation circuit is radio-frequency signal generator 4.
Described radio-frequency signal generator 4 drives light intensity modulator 6.
Described counting circuit is controlled and reading to radio-frequency signal generator 4 by controlling bus.
Described counting circuit is computer 13.
Described computer 13 is acquired to the data of lock-in amplifier 11, and the centre frequency of tunable laser 1
It is modified with the signal frequency of radio-frequency signal generator 4.
Described data is to detect two sidebands of light and the fast axle of corresponding sensing grating 9 and slow axis transmission peak center
Two frequency discrimination signal.
Described sensing grating 9 one end is connected with protecting polarisation coupler 14, and the other end is processed through removing Fresnel reflection.
As shown in Fig. 2 described locking principle is: the center of two intensity modulated sidebands that light intensity modulator 6 produces
Frequency is located near two resonance peaks respectively.Can be obtained respectively based on the synchronous demodulation of optical phase modulator 5 and lock-in amplifier 11
Frequency discrimination signal on fast and slow axis, can be learnt the frequency departure δ f of the sideband and resonance peak detecting light by this frequency discrimination signalfastWith
δfslow, wherein: δ ffastRepresent the frequency deviation that sideband and resonance peak are detected on fast axle, δ fslowRepresent the side that light is detected on slow axis
Band and the frequency deviation of resonance peak.Individually the centre wavelength of tuning tunable laser 1 can make two sidebands move to equidirectional；And
Individually the signal frequency of tuned radio frequency signal generator 4 can make two sidebands move round about.For making two detection sideband essences
Really be aligned two resonance centers, then the tuning amount that tunable laser 1 exports should be set toThe tune of radiofrequency signal
Harmonic quantity is set toDue to corresponding frequency discrimination signal η of resonance peak on slow axisslowAnd resonance peak is corresponding in fast axle
Frequency discrimination signal ηfastRespectively with frequency departure δ fslow、δffastIt is directly proportional, therefore the tuning amount of laser instrument output frequencyWith η1=ηslow+ηfastIt is directly proportional, and the tuning amount of radiofrequency signalWith η2=
ηfast-ηslowIt is directly proportional.Therefore, we select common mode component (the i.e. η of two frequency discrimination signal1) and differential-mode component (i.e. η2) as two
Individual feedback variable, respectively to laser instrument output frequency flaserWith radio frequency signal frequency fsidebandConstantly revised, you can realize
Two sidebands are aligned to while two resonance peaks.Now, the Bragg frequency of probe (π phase shift Bragg grating) is laser instrument
Output frequency flaser, and birefringence cause difference on the frequency is twice radio frequency signal frequency 2 × fsideband.
Described polarization maintaining optical fibre is high birefringence type polarization maintaining optical fibre.
Described sensing grating 9 is π phase shift optical fiber Bragg grating on panda type polarization-preserving fiber, and operating central wavelength is
1550nm, phase-shifted grating resonance peak width is 0.25pm (respective frequencies are 31mhz), and fast and slow axis birefringence causes the model of difference on the frequency
Enclose for 46.5～47.0ghz.
As shown in figure 3, described π phase shift optical fiber Bragg grating has ultra-narrow transmission window, the light in fast axle and slow axis
Fine transmission window has different centre wavelengths, and both of which is to temperature and strain sensitive, its sensitivity be not introduced into phase shift
Bragg grating consistent.The centre wavelength difference of the optical fiber transmission window in fast axle and slow axis is by the birefringence system of polarization maintaining optical fibre
Number determines, and also to temperature and strain sensitive.In above-mentioned two physical effect, the centre frequency of optical fiber transmission window is to temperature
Sensitivity with strain, the corresponding change of centre wavelength difference is on the occasion of centre wavelength difference is negative value to the sensitivity of temperature.
The output linewidth of described tunable laser 1 is the continuous light of 1khz.
The present embodiment is related to the method based on said system, comprises the following steps:
The tunable laser that step 1, the signal frequency according to radio-frequency signal generator 4 after locking and optical wavelengthmeter 3 read
The output wavelength of device 1, obtain after conversion the transmission peaks of sensing grating 9 fast and slow axis center frequency difference (birefringence cause difference on the frequency) and
The mean value (grating Bragg frequency) of two centre of homology frequencies.
Described birefringence causes difference on the frequency δ fbiFor radio-frequency signal generator 4 signal frequency after locking 2 times.
Described grating Bragg frequency fbrFrequency form for the output wavelength of the tunable laser 1 after locking.
Step 2, according to birefringence cause difference on the frequency δ fbiWith grating Bragg frequency fbrSensitive with strain to temperature respectively
The corresponding relation of degree, solves temperature to be measured and strain.
Described corresponding relation is:Wherein:For grating Bragg frequency pair
The sensitivity of temperature,For grating Bragg frequency to the sensitivity straining,Cause the spirit to temperature for the difference on the frequency for birefringence
Sensitivity,Cause the sensitivity to strain for the difference on the frequency for birefringence, t is to treat testing temperature, ε is strain to be measured, t0And ε0For undetermined
Temperature and strain constant.
Described t0And ε0Can be determined by system calibration.
As shown in Figure 4 and Figure 5, in 1550nm wave band, the grating Bragg frequency f of the present embodimentbrCause frequency with birefringence
Difference δ fbiAll with treat that testing temperature t and strain stress to be measured are linear；The sensitivity to temperature for the grating Bragg frequency The sensitivity to strain for the grating Bragg frequencyBirefringence causes difference on the frequency to temperature
The sensitivity of degreeBirefringence causes the sensitivity to strain for the difference on the frequency
As shown in fig. 6, sensing grating 9 is in the environment having temperature drift, apply the sinusoidal strain of 1 μ ε, 0.02hz simultaneously
Signal, the grating Bragg frequency recording and birefringence cause difference on the frequency to show sinusoidal variations and slow drift, with optical fiber simultaneously
Grating is consistent with the cross sensitivity of strain to temperature.
As shown in Fig. 6 (b), strain data shows as clearly sinusoidal signal and no drifting about, and temperature data then shows as delaying
Slow drift and do not contain sinusoidal variations component.This result is consistent with actual conditions, it can thus be assumed that the present embodiment achieves grating
The measurement while temperature of upper cross sensitivity and strain.
The present embodiment is 0.0029 DEG C to the Measurement Resolution of temperature, and the Measurement Resolution to strain is 0.046 μ ε.
The temperature measurement range of the present embodiment is 50～200 DEG C, and strain measurement scope is up to 2000 μ ε.
The present embodiment, will be slow by the polarization maintaining optical fibre 7 of 45 ° of spin weldings using the closed loop demodulation being detected based on double-side band
Linearly polarized light on axle switchs to the equal detection light of intensity on fast and slow axis, the π phase shift optical fiber Bragg grating knot on polarization maintaining optical fibre
Structure is compact, and size is identical with the grating of common high reflectance, thus stronger to the adaptability of application scenarios；Manufacturing process becomes
Ripe, cost is relatively low, is easy to volume production.
Claims (7)
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| Application Number | Priority Date | Filing Date | Title |
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| CN201620661245.3U CN205898164U (en) | 2016-06-29 | 2016-06-29 | Fiber Bragg Grating Sensing System for Simultaneous Measurement of Temperature and Strain |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107894245A (en) * | 2017-12-11 | 2018-04-10 | 哈尔滨工程大学 | A kind of polarization maintaining optical fibre interferometer strained with temperature simultaneously measuring |
| CN108036733A (en) * | 2017-12-25 | 2018-05-15 | 北京信息科技大学 | Temperature and strain while measurement sensor under II type-IR type polarization-maintaining FBG hot environments |
| CN110631617A (en) * | 2019-09-23 | 2019-12-31 | 苏州光格设备有限公司 | Long-distance high-resolution Brillouin optical time domain analysis method |
-
2016
- 2016-06-29 CN CN201620661245.3U patent/CN205898164U/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107894245A (en) * | 2017-12-11 | 2018-04-10 | 哈尔滨工程大学 | A kind of polarization maintaining optical fibre interferometer strained with temperature simultaneously measuring |
| CN108036733A (en) * | 2017-12-25 | 2018-05-15 | 北京信息科技大学 | Temperature and strain while measurement sensor under II type-IR type polarization-maintaining FBG hot environments |
| CN110631617A (en) * | 2019-09-23 | 2019-12-31 | 苏州光格设备有限公司 | Long-distance high-resolution Brillouin optical time domain analysis method |
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| C14 | Grant of patent or utility model | ||
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| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20170118 Termination date: 20200629 |