CN103674079A - Real-time measurement method based on fiber Bragg grating sensor measurement system - Google Patents
Real-time measurement method based on fiber Bragg grating sensor measurement system Download PDFInfo
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Abstract
The invention is a real-time measurement method based on a fiber Bragg grating sensor measurement system. The system comprises a tunable laser source, an optical splitter, an upper computer, an optical power meter and n fiber grating sensors. The real-time measurement method comprises the following steps: I, acquiring calibration parameters of a linear relational expression between the center wavelength of each fiber Bragg grating sensor and a calibrated to-be-measured physical quantity through experiment; II, generating reference data tables of the n fiber grating sensors; and III, measuring the physical parameter of a test point corresponding to each fiber grating sensor in real time. According to the method, the upper computer controls the laser source to carry out reference scanning on each FBG to obtain the reference data table of each FBG, the specific wavelength is output and the reflection optical power is measured sequentially according to the tables during real-time measurement, and the specific output wavelength is adjusted and the offset of the center wavelength of each FBG is calculated and demodulated according to the reference data tables. The measurement speed is improved greatly, real-time measurement is ensured, the measurement precision is high, and the physical quantity change corresponding to wavelength offset as low as 0.1pm can be detected.
Description
(1) technical field
The present invention relates to Photoelectric Detection field, be specially a kind of method for real-time measurement based on fiber Bragg grating sensor measuring system.
(2) background technology
The method for making of fiber grating maturation has greatly promoted the development of fiber grating application technology, makes fiber grating become one of the most rising passive device.Its typical application is fiber-optic grating sensor, there is electrical insulating property good, anti-electromagnetic interference (EMI) and anti-Radio frequency interference (RFI) (RFI) ability are strong, stable chemical performance, corrosion-resistant, the characteristics such as volume is little, lightweight, and loss is little, capacity is large, and version is flexible, sensitivity is high, therefore the optical fiber grating sensing network that the many reference amounts such as the stress of its formation, strain, temperature and vibration detect has outstanding advantage, replace traditional sensors just gradually and become the main force of sensor family.
Fiber Bragg Grating FBG (Fiber Bragg Grating, be abbreviated as FBG) be the light sensitive characteristic that utilizes fiber optic materials, with certain Writing Technology, in a segment limit of bare fibre, write the in-core body grating with periodic refractive index, its Essential Action is in fibre core, to form the narrow band optical filter centered by resonant wavelength, when wideband light source or tunable optical source output light process grating, narrow-band spectrum in spectrum centered by the Bragg of grating wavelength is reflected and demodulated at grating place, and other most of light will transmission occur and transmit along original direction.Fiber grating fibre core is under the effect of ambient temperature, stress and so on physical quantities, and refractive index will change, thereby causes the drift of optical grating reflection center wavelength of light.This characteristic is the principle of work of fiber Bragg grating sensor, can draw the variation of fiber-optic grating sensor environment measured physical quantity of living in by the variation of detection of reflected optical wavelength.
At present, Optical Fiber Sensor Measurement System light source adopts broad band laser light source or continuously adjustable LASER Light Source.The Optical Fiber Sensor Measurement System disadvantage that adopts broad band laser light source is that the optical power density of light source output is low, useful power is only below the per mille for its output general power, thereby the Fibre Optical Sensor of this system can only be used in short range, and measurement is counted less.Comply with Optical Fiber Sensor Measurement System towards the future development trend of wavelength-division multiplex and optical fiber sensor network, Optical Fiber Sensor Measurement System adopts tunable laser source, has improved power and resolution.But at present tunable laser source mainly adopts continuous sweep mode, the Partial Power that only has corresponding Fibre Optical Sensor to set wavelength (or frequency) is applied, so laser power utilizes insufficiently, and measuring speed is limited, and its resolution also has much room for improvement.
(2) summary of the invention
The object of this invention is to provide a kind of method for real-time measurement based on fiber Bragg grating sensor measuring system, in the Optical Fiber Sensor Measurement System of tunable laser source, adopt wavelength-division multiplex method, improved measuring speed and resolution.
The present invention has designed the method for real-time measurement based on fiber Bragg grating sensor measuring system, and what this method was used comprises tunable laser source, optical splitter, host computer, a light power meter and n fiber-optic grating sensor based on Bragg optical-fiber grating sensor measuring system.Described fiber-optic grating sensor is fiber Bragg grating sensor (Fiber Bragg Grating Sensor, FBG).Host computer connects controls tunable laser source and light power meter, tunable laser source connects a three-dB coupler, n the fiber-optic grating sensor that it closes road port serial connection, the integer that n is 1～120 are inputted, arrived to laser from a minute optical port of three-dB coupler.Another of three-dB coupler minute optical port is connected to light power meter, in order to catch this three-dB coupler, close the reflected optical power of n fiber-optic grating sensor of terminal series connection, and the synchronous triggering input port of power meter connects the synchronous triggering delivery outlet of tunable laser source, make power meter image data change and synchronize with optical source wavelength.
Each fiber-optic grating sensor has certain wavelength response range, and its reflectance spectrum is emergent power reflection at peak within the scope of this, the peak value P of power
maxcorresponding wavelength is called central wavelength lambda
c, being also this fiber grating sensor wavelength, the residing crest of power peak is main mould.Meanwhile, the peak power of adjacent with the main mould flash mould of definition is main mould bottom power P
min, the power P of main mould crest both sides spectral line
minlocate the bandwidth λ that the difference of corresponding wavelength is this fiber-optic grating sensor reflectance spectrum
bW.
When temperature, the stress and so on physical quantities of fiber-optic grating sensor ambient outside environment change, will make effective refractive index or the cycle of fibre core grating change thereupon, therefore reflectance spectrum is at certain scope bias internal, center sensor wavelength shift, by detecting the variation of each fiber-optic grating sensor reflectance spectrum, therefrom demodulation obtains the variation of extraneous specific physical quantity.The operating wavelength range of n fiber-optic grating sensor of series connection is without juxtaposition, and their reflectance spectrum deviation range is all not identical.According to extraneous test condition, delimit the operating wavelength range of n fiber-optic grating sensor, and the operating wavelength range of each fiber-optic grating sensor all belongs in the wavelength coverage that the tunable laser source of native system use covers.
Bandwidth λ when the reflectance spectrum of n fiber-optic grating sensor
bWequate, the dynamic range of its measure physical quantities also equates simultaneously, and reflectance spectrum offset Δ λ equates, is guaranteeing that, on the basis of each sensor reflectance spectrum waveform integrality, the quantity n of fiber-optic grating sensor meets:
n<(λ
ALL-λ
BW)/Δλ
Wherein, λ
aLLscanning wavelength total bandwidth for native system tunable laser source used.The center wavelength shift amount Δ λ of each fiber-optic grating sensor is larger, the dynamic range of the physical quantity of test is just larger, but multiplexing fiber-optic grating sensor quantity n will reduce, therefore should and measure dynamic range according to actual conditions reasonable distribution number of sensors.
Each fiber-optic grating sensor pair and cardiac wave appearance wherein with input reflection of light rate be 80～90%.
The job step based on fiber Bragg grating sensor measuring system method for real-time measurement of the present invention's design is as follows:
I, experiment obtain the calibrating parameters of the linear relation between each fiber Bragg grating sensor centre wavelength and the measured physical quantity of demarcation
The spectral shift amount of fiber-optic grating sensor is all considered as linear relation from different physical parameters, but slope in linear relation is different.The fiber-optic grating sensor that germanium fused quartz optical fiber makes as mixed is during for strain measurement, and the wave length shift of its fiber grating Prague sensor and the theoretical relationship between axial strain amount are expressed as:
Δλ=0.78λε
ε is axial strain amount, and in 1550nm window, its axial strain amount response is: 1.209pm/ μ ε.
And will mix fiber-optic grating sensor that germanium fused quartz optical fiber makes for temperature survey, the theoretical relationship of its wavelength shift and temperature variation is expressed as:
Δλ=8.85×10
-6λΔT
Δ T is temperature variation, and in 1550nm window, its temperature-responsive is about: 10pm/ ℃.
Due to the manufacture craft of fiber Bragg grating sensor and the difference of encapsulating material, response parameter slope and intercept in the linear relation of each fiber Bragg grating sensor and identical measured physical quantity also can be different.Therefore, slope and intercept in the center wavelength shift amount of each fiber Bragg grating sensor and the linear relation of measured physical quantity need to be demarcated by experiment, just the variation of measurand can be obtained by the center wavelength shift demodulation of fiber Bragg grating sensor.
Use reference instrument to demarcate at least three different values of measured physical quantity, be recorded in the centre wavelength of each fiber Bragg grating sensor corresponding under each measured physical quantity effect of demarcating simultaneously, use linear fit method to calculate the linear relation of measured physical quantity and fiber Bragg grating sensor centre wavelength, and record response parameter slope and the values of intercept of this linear equation.
Making material, technique and the packaged type of a plurality of fiber Bragg grating sensors that use in measuring system are all identical, can demarcate the response parameter of one of them fiber Bragg grating sensor as the common response parameter of each fiber Bragg grating sensor of using in measuring system, the measuring accuracy of this kind of situation is not high.
The reference data table of II, n fiber-optic grating sensor of generation
Before real-time testing under original state, use tunable laser source to carry out length scanning to n fiber-optic grating sensor, by light power meter, measure the reflectance spectrum distribution situation of n cascaded fiber grating sensor, power unit is mw, and a crest represents a fiber-optic grating sensor.I the main mould peak power of fiber-optic grating sensor reflectance spectrum is P
imax, bottom power is P
imin, i is the sequence number of n fiber-optic grating sensor, i=0, and 1,2,3 ... n-1.In any side of i the main mould crest of fiber-optic grating sensor reflectance spectrum, choose and have one section of spectral line of monotonicity as the reference spectra of this fiber-optic grating sensor, main mould crest left side is monotone increasing, and right side is monotone decreasing.The upper extreme point corresponding wavelength of reference spectra is λ
iH, corresponding power is P
iH, its lower extreme point corresponding wavelength is λ
iL, corresponding power is P
iL.Be the performance number P of reference spectra upper extreme point
iHmaximum, preferred plan is for selecting to get P
iHbe main mould peak power P
imax90～95%, the value P of the power of the lower extreme point of reference spectra
iLminimum, preferred plan is for selecting to get P
iLbe main mould bottom power P
imin105～110%.Wavelength width corresponding to reference spectra is λ
iHand λ
iLthe absolute value of difference, mainly the making characteristic by fiber-optic grating sensor determines.For convenient, calculate, the reference spectra of each fiber-optic grating sensor of native system is all got main mould crest left side or is all got right side, thereby obtains take the reference data table that i is order, comprises the reflectance spectrum parameter lambda of each fiber-optic grating sensor under original state
iE, λ
i, P
iHand P
iL, λ wherein
ifor the middle wavelength of reference spectra, λ
iassignment is λ for the first time
i=0.5 (λ
iL+ λ
iH); λ
iE=0.5| λ
iH-λ
iL|.In addition also must record, the centre wavelength value λ of reflectance spectrum under this fiber-optic grating sensor original state
iC.
III, survey the physical parameter of the corresponding test point of each fiber-optic grating sensor
According to the wavelength X of n fiber-optic grating sensor in step II gained reference data table
iset successively the output wavelength of tunable laser source, use light power meter to measure in real time the reflected optical power of each fiber-optic grating sensor, record each λ
ithe corresponding current reflected optical power of fiber-optic grating sensor, and calculate each fiber-optic grating sensor center wavelength shift amount Δ λ
i.Because the operating wavelength range of each sensor is different, according to the output wavelength of LASER Light Source and reflected optical power, can judge corresponding fiber-optic grating sensor sequence number, and then utilize method of interpolation by current reflected optical power and reference table, to be calculated the skew of each fiber-optic grating sensor reflectance spectrum.According to each fiber Bragg grating sensor centre wavelength of step I gained, can demodulation obtain measured physical quantity corresponding to each sensor place test point with the linear relation of measured physical quantity, during continuous coverage, can obtain the gradual situation of this measured physical quantity.Concrete steps are as follows:
I, i=0 is set;
II, the output wavelength that tunable laser source is set are λ
i;
III, by light power meter, measure i fiber-optic grating sensor reflected optical power value P
iand judge according to i fiber-optic grating sensor corresponding power value of step I gained reference data table:
III-1, work as P
iL< P
i< P
iH, execution step IV;
III-2, work as P
i≤ P
iL, the output wavelength of adjustment tunable laser source,
When reference spectra arranges λ in main mould crest left side
i=λ
i+ λ
iE,
When reference spectra arranges λ in main mould crest right side
i=λ
i-λ
iE,
Return to afterwards execution step II;
III-3, work as P
i>=P
iH, the output wavelength of adjustment tunable laser source,
When reference spectra arranges λ in main mould crest left side
i=λ
i-λ
iE,
When reference spectra arranges λ in main mould crest right side
i=λ
i+ λ
iE,
Return to afterwards execution step II;
IV, calculating reflectance spectrum side-play amount, Real-time demodulation measured physical quantity; In step II gained reference data table, utilize method of interpolation to draw this fiber-optic grating sensor current power value P
icorresponding wavelength value λ
i', by λ
i' with the output wavelength λ of current tunable laser source
icompare, calculate thus the offset Δ λ of its reflectance spectrum centre wavelength
i=λ
i-λ
i', i the fiber-optic grating sensor emission spectrum original state central wavelength lambda obtaining according to Step II
iCthe emission spectrum centre wavelength of calculating current i fiber-optic grating sensor is: λ '
iC=λ
iC+ Δ λ
i, and then demodulation obtains the data of temperature or the physical parameter to be measured such as pressure or stress.
V, work as i=n-1, do not receive in the situation of ceasing and desisting order and skip to step I, the end of run of ceasing and desisting order if receive; As i ≠ n-1, i=i+1 is set, skip to step II.
IV, lasting Real-time demodulation measured physical quantity
Constantly circulation execution step III, continues circulation to the data of n fiber-optic grating sensor and measures and measured physical quantity is continued to demodulation, and the measured physical quantity that real-time follow-up is gradual, ceases and desist order until receive, and operation stops.
The advantage that the present invention is based on the method for real-time measurement of fiber Bragg grating sensor measuring system is: 1, PC control tunable laser source first carries out reference scan to each fiber-optic grating sensor, obtain the reference data table of each fiber-optic grating sensor, only need be according to wavelength X in the middle of the reference spectra of upper each fiber-optic grating sensor of this table during actual measurement
iset successively tunable laser source output specific wavelength, measure the side-play amount of each fiber-optic grating sensor centre wavelength and carry out demodulation, each skew of measuring certain fiber-optic grating sensor reflectance spectrum, without tunable laser source, in whole tuning range, scan, thereby measuring speed is improved greatly, guarantee the real-time of measuring; 2, measuring accuracy is high, can detect and be low to moderate physical quantity variation corresponding to 0.1pm wavelength shift.
(4) accompanying drawing explanation
Fig. 1 is this method for real-time measurement embodiment certain fiber Bragg grating sensor reflected light spectrogram used based on fiber Bragg grating sensor measuring system;
Fig. 2 is that this method for real-time measurement embodiment based on fiber Bragg grating sensor measuring system is used based on fiber Bragg grating sensor measuring system structural representation;
Fig. 3 is the process flow diagram of this method for real-time measurement embodiment based on fiber Bragg grating sensor measuring system;
Fig. 4 is the part reflected light spectrogram of these method for real-time measurement embodiment 3 fiber Bragg grating sensor original states used based on fiber Bragg grating sensor measuring system.
(5) embodiment
As shown in Figure 1, its reflectance spectrum has main mould and Bian Mo to this method for real-time measurement embodiment i fiber Bragg grating sensor reflected light spectrogram used based on fiber Bragg grating sensor measuring system.Main mould crest peak power is P
imax, its corresponding wavelength is called the central wavelength lambda of this fiber Bragg grating sensor
iC, be also this fiber grating sensor wavelength.Meanwhile, the peak power of adjacent with the main mould flash mould of definition is main mould bottom power P
imin, the power P of main mould crest both sides spectral line
iminlocate the bandwidth λ that the difference of corresponding wavelength is this fiber-optic grating sensor reflectance spectrum
iBW.
This method for real-time measurement embodiment based on fiber Bragg grating sensor measuring system used based on fiber Bragg grating sensor measuring system block diagram as shown in Figure 2, comprise tunable laser source, optical splitter, host computer, a light power meter and n fiber-optic grating sensor, in figure, dotted line represents light path.Described fiber-optic grating sensor is fiber Bragg grating sensor (FBG), and this example adopts mixes germanium fused quartz optical fiber and make, and for encapsulating, do not add the naked fine Bragg grating sensor of protection tube.Host computer connects controls tunable laser source and light power meter, and tunable laser source connects a three-dB coupler, and laser inputs, arrives from a minute optical port of three-dB coupler n the fiber-optic grating sensor that it closes road port serial connection.Another of three-dB coupler minute optical port is connected to light power meter, and synchronizing cable connects the synchronous triggering input port of power meter and the synchronous triggering delivery outlet of tunable laser source.
Each fiber-optic grating sensor pair and cardiac wave appearance wherein with input reflection of light rate be 80～90%.This example is the method for the strain measurement of steel disc.
The tuning range of this routine tunable laser source is 1524～1610nm, total bandwidth λ
aLLfor 86nm, suppose that dependent variable scope to be measured is for ± 400 μ ε, so the skew λ of each fiber-optic grating sensor reflectance spectrum
dbe about ± 0.49nm of scope, the centre wavelength interval of each sensor reflectance spectrum must >0.98nm, supposes the maximum λ of each sensor
bWfor 0.53nm, so, the number of sensors of series connection must meet n< (λ
aLL-λ
bW)/λ
dtherefore n maximal value is 87.This example is got n=3.
Originally based on fiber Bragg grating sensor measuring system method for real-time measurement embodiment process flow diagram as shown in Figure 3, specific works step is as follows:
I, experiment obtain the calibrating parameters of the linear relation between each fiber Bragg grating sensor centre wavelength and the measured physical quantity of demarcation
In this example, by the parallel middle part that is pasted on steel disc of 3 Fiber Bragg Grating FBGs (FBG) sensor, one end of steel disc is fixed, steel disc is level, the steel disc other end connects spring clip one end, at the spring clip other end, hang counterweight, counterweight varies in weight, and spring clip hangs that one end of counterweight is up and down, spring clip produces tension to steel disc.The state that counterweight is not hung in the setting of this example is original state, and the strain of steel disc is 0.Near on the steel disc of FBG sensor, pasting straingauge, straingauge connects static resistance strainmeter, can record the electrostrictive strain resistance of steel disc, and obtain thus the dependent variable of steel disc.This example changes the counterweight weight that spring clip hangs, and demarcates three different steel disc strain values, is recorded in the centre wavelength of each fiber Bragg grating sensor corresponding under each dependent variable effect of demarcating simultaneously, and the data obtained is as shown in table 1.The sequence number of 3 fiber Bragg grating sensors of this example is i=0,1,2.
Table 1 is demarcated the centre wavelength of each FBG sensor under steel disc dependent variable
| ε=0 | ε=100με | ε=200με | ε=300με | |
| The centre wavelength of FBG 0 (nm) | 1540.820 | 1540.939 | 1541.055 | 1541.176 |
| The centre wavelength of FBG 1 (nm) | 1546.840 | 1546.960 | 1547.077 | 1547.199 |
| The centre wavelength of FBG2 (nm) | 1552.880 | 1552.977 | 1553.118 | 1553.236 |
According to table 1 the data obtained, slope (k) and the intercept (b) of the linear relation of use linear fit method calculating steel disc dependent variable and fiber Bragg grating sensor centre wavelength are as follows:
The reference data table of II, 3 fiber-optic grating sensors of generation
Under state in steel disc one end without suspension counterweight, 3 fiber-optic grating sensors are carried out to reference scan.Use tunable laser source to carry out length scanning to fiber-optic grating sensor, measure the reflectance spectrum distribution situation of 3 cascaded fiber grating sensors by light power meter, power unit is mw, and a crest represents a fiber-optic grating sensor, as shown in Figure 4.This example is chosen the one section of spectral line with monotonicity as with reference to spectrum in the reflectance spectrum crest left side of each FBG sensor, reference spectra upper end performance number P
iHbe 95% of main mould peak power, i.e. P
iH=0.95P
imax, corresponding wavelength is λ
iH; Reference spectra lower end performance number P
iLbe 105% of main mould waveform bottom power, i.e. P
iL=1.05P
imin, corresponding wavelength λ
iL.Obtain thus the reference data table of 3 fiber-optic grating sensors shown in table 2, comprise the reflectance spectrum parameter lambda of each fiber-optic grating sensor under original state
iC, λ
iE, λ
i, P
iHand P
iL, λ wherein
iE=0.5| λ
iH-λ
iL|, λ
i=0.5 (λ
iH+ λ
iL).
The reference data table of table 2 fiber-optic grating sensor
Counterweight is hung on to the free end of spring clip that steel disc connects, change counterweight quantity or manual stress application, measure in real time the dependent variable of the steel disc of each FBG sensor present position.
According to the wavelength X of 3 fiber-optic grating sensors in step II gained reference data table
iset successively the output wavelength of tunable laser source, use light power meter to measure in real time the reflected optical power of each fiber-optic grating sensor, to each λ
ithe corresponding current reflected optical power of fiber-optic grating sensor is carried out record.Because the bandwidth of operation of each FBG sensor is different, according to the output wavelength of LASER Light Source and reflected optical power, can judge corresponding fiber-optic grating sensor sequence number, and then use method of interpolation by current reflected optical power and reference data table, to be calculated the side-play amount of this fiber-optic grating sensor centre wavelength, be the side-play amount of its reflectance spectrum, thereby demodulate the current dependent variable of its place test point steel disc in conjunction with the strain measurement coefficient of demarcating before.
I, i=0 is set;
II, the output wavelength that tunable laser source is set are λ
i;
III, by light power meter, measure corresponding fiber-optic grating sensor reflected optical power value P
iand carry out power judgement according to the data of step I gained reference table:
III-1, work as P
iL< P
i< P
iH,, execution step IV.
III-2, work as P
i≤ P
iL, the output wavelength of adjustment light source, arranges λ
i=λ
i+ λ
iE, return to execution step II.
III-3, work as P
i>=P
iH, the output wavelength of adjustment light source, arranges λ
i=λ
i-λ
iE, return to execution step II.
IV, calculating reflectance spectrum side-play amount, Real-time demodulation steel disc strain value.In step II gained reference data table, utilize method of interpolation to draw this fiber-optic grating sensor current power value P
icorresponding wavelength value λ
i', by λ
i' with the output wavelength λ of current tunable laser source
icompare, calculate thus the offset Δ λ of its reflectance spectrum centre wavelength
i=λ
i-λ '
i, i the fiber-optic grating sensor emission spectrum original state central wavelength lambda obtaining according to Step II
iCcalculate the current central wavelength lambda of emission spectrum of i fiber-optic grating sensor '
iC=λ
iC+ Δ λ
i, and then demodulation obtains steel disc strain value.
V, work as i=2, skip to step I, the end of run of ceasing and desisting order if receive confiscating cease and desist order in the situation that; When i ≠ 2, i=i+1 is set, skip to step II.
IV, lasting Real-time demodulation steel disc strain value change
Constantly circulation execution step III, the data of 3 fiber-optic grating sensors are continued to circulation to be measured and the dependent variable of steel disc each point is continued to carry out demodulation, the dependent variable of each fiber-optic grating sensor present position steel disc of real-time follow-up, ceases and desist order until receive, and operation stops.
This routine method of testing has high speed real-time, measures sensitivity and reaches 0.1 μ ε.
Above-described embodiment, is only the specific case that object of the present invention, technical scheme and beneficial effect are further described, and the present invention is not defined in this.All any modifications of making, be equal to replacement, improvement etc., within being all included in protection scope of the present invention within scope of disclosure of the present invention.
Claims (5)
1. the method for real-time measurement based on fiber Bragg grating sensor measuring system, what this method was used comprises tunable laser source, optical splitter, host computer, a light power meter and n fiber-optic grating sensor based on Bragg optical-fiber grating sensor measuring system; Described fiber-optic grating sensor is fiber Bragg grating sensor; Host computer connects controls tunable laser source and light power meter, tunable laser source connects a three-dB coupler, n the fiber-optic grating sensor that it closes road port serial connection, the integer that n is 1～120 are inputted, arrived to laser from a minute optical port of three-dB coupler; Another of three-dB coupler minute optical port is connected to light power meter; And the synchronous triggering input port of power meter connects the synchronous triggering delivery outlet of tunable laser source; Each fiber-optic grating sensor has certain wavelength response range, and its reflectance spectrum is emergent power reflection at peak within the scope of this, the peak value P of power
maxcorresponding wavelength is called central wavelength lambda
c, the peak power of the flash mould adjacent with main mould is main mould bottom power P
min, the power P of main mould crest both sides spectral line
minlocate the bandwidth λ that the difference of corresponding wavelength is this fiber-optic grating sensor reflectance spectrum
bW; Each fiber-optic grating sensor pair and cardiac wave appearance wherein with input reflection of light rate be 80～90%; The job step that it is characterized in that this method for real-time measurement is as follows:
I, experiment obtain the calibrating parameters of the linear relation between each fiber Bragg grating sensor centre wavelength and the measured physical quantity of demarcation
Use reference instrument to demarcate at least three different values of measured physical quantity, be recorded in the centre wavelength of each fiber Bragg grating sensor corresponding under each measured physical quantity effect of demarcating simultaneously, use linear fit method to calculate the linear relation of measured physical quantity and fiber Bragg grating sensor centre wavelength, and record response parameter slope and the values of intercept of this linear equation;
The reference data table of II, n fiber-optic grating sensor of generation
Before real-time testing under original state, use tunable laser source to carry out length scanning to n fiber-optic grating sensor, by light power meter, measure the reflectance spectrum distribution situation of n cascaded fiber grating sensor, power unit is mw, and a crest represents a fiber-optic grating sensor; I the main mould peak power of fiber-optic grating sensor reflectance spectrum is P
imax, bottom power is P
imin, i is the sequence number of n fiber-optic grating sensor, i=0, and 1,2,3 ... n-1; In any side of i the main mould crest of fiber-optic grating sensor reflectance spectrum, choose and there is one section of spectral line of monotonicity as the reference spectra of this fiber-optic grating sensor; The upper extreme point corresponding wavelength of reference spectra is λ
iH, corresponding power is P
iH, its lower extreme point corresponding wavelength is λ
iL, corresponding power is P
iL, the reference spectra of each fiber-optic grating sensor of native system is all got main mould crest left side or is all got right side, thereby obtains take the reference data table that i is order, comprises the reflectance spectrum parameter lambda of each fiber-optic grating sensor under original state
iE, λ
i, P
iHand P
iL, λ wherein
ifor the middle wavelength of reference spectra, λ
iassignment is λ for the first time
i=0.5 (λ
iL+ λ
iH); λ
iE=0.5| λ
iH-λ
iL|; Record the centre wavelength value λ of reflectance spectrum under this fiber-optic grating sensor original state simultaneously
iC;
III, survey the physical parameter of the corresponding test point of each fiber-optic grating sensor
According to the wavelength X of n fiber-optic grating sensor in step II gained reference data table
iset successively the output wavelength of tunable laser source, use light power meter to measure in real time the reflected optical power of each fiber-optic grating sensor, record each λ
ithe corresponding current reflected optical power of fiber-optic grating sensor, and calculate each fiber-optic grating sensor center wavelength shift amount Δ λ
i; According to the output wavelength of tunable laser source and reflected optical power, judge corresponding fiber-optic grating sensor sequence number, utilize method of interpolation by current reflected optical power and reference data table, to be calculated the skew of each fiber-optic grating sensor reflectance spectrum; According to each fiber Bragg grating sensor centre wavelength of step I gained and the linear relation demodulation of measured physical quantity, obtain measured physical quantity corresponding to each sensor place test point;
IV, lasting Real-time demodulation measured physical quantity
Constantly circulation execution step III, continues circulation to the data of n fiber-optic grating sensor and measures and measured physical quantity is continued to demodulation, and the measured physical quantity that real-time follow-up is gradual, ceases and desist order until receive, and operation stops.
2. the method for real-time measurement based on fiber Bragg grating sensor measuring system according to claim 1, is characterized in that the concrete steps of described step III are as follows:
I, i=0 is set;
II, the output wavelength that tunable laser source is set are λ
i;
III, by light power meter, measure i fiber-optic grating sensor reflected optical power value P
iand judge according to i fiber-optic grating sensor corresponding power value of step I gained reference data table:
III-1, work as P
iL< P
i< P
iH, execution step IV;
III-2, work as P
i≤ P
iL, the output wavelength of adjustment tunable laser source,
When reference spectra arranges λ in main mould crest left side
i=λ
i+ λ
iE,
When reference spectra arranges λ in main mould crest right side
i=λ
i-λ
iE,
Return to afterwards execution step II;
III-3, work as P
i>=P
iH, the output wavelength of adjustment tunable laser source,
When reference spectra arranges λ in main mould crest left side
i=λ
i-λ
iE,
When reference spectra arranges λ in main mould crest right side
i=λ
i+ λ
iE,
Return to afterwards execution step II;
IV, calculating reflectance spectrum side-play amount, Real-time demodulation measured physical quantity; In step II gained reference data table, utilize method of interpolation to draw this fiber-optic grating sensor current power value P
icorresponding wavelength value λ
i', by λ
i' with the output wavelength λ of current tunable laser source
icompare, calculate thus the offset Δ λ of its reflectance spectrum centre wavelength
i=λ
i-λ
i', i the fiber-optic grating sensor emission spectrum original state central wavelength lambda obtaining according to Step II
iCthe emission spectrum centre wavelength of calculating current i fiber-optic grating sensor is: λ '
iC=λ
iC+ Δ λ
i, and then demodulation obtains the data of temperature or the physical parameter to be measured such as pressure or stress;
V, work as i=n-1, do not receive in the situation of ceasing and desisting order and skip to step I, the end of run of ceasing and desisting order if receive; As i ≠ n-1, i=i+1 is set, skip to step II.
3. the method for real-time measurement based on fiber Bragg grating sensor measuring system according to claim 1, is characterized in that:
Making material, technique and the packaged type of a plurality of fiber Bragg grating sensors that use in measuring system are all identical, and described step I is demarcated the response parameter of one of them fiber Bragg grating sensor as the common response parameter of each fiber Bragg grating sensor of using in measuring system.
4. the method for real-time measurement based on fiber Bragg grating sensor measuring system according to claim 1, is characterized in that:
The performance number P of reference spectra upper extreme point in described step II
iHbe main mould peak power P
imax90～95%, the value P of the power of the lower extreme point of reference spectra
iLbe main mould bottom power P
imin105～110%.
5. the method for real-time measurement based on fiber Bragg grating sensor measuring system according to claim 1, is characterized in that:
The bandwidth λ of the reflectance spectrum of described n the fiber-optic grating sensor when measuring system
bWequate, the dynamic range of its measure physical quantities also equates simultaneously, and reflectance spectrum offset Δ λ equates, is guaranteeing that, on the basis of each sensor reflectance spectrum waveform integrality, the quantity n of fiber-optic grating sensor meets:
n<(λ
ALL-λ
BW)/Δλ
Wherein, λ
aLLscanning wavelength total bandwidth for native system tunable laser source used.
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