CN105157733B - A kind of improved generation carrier phase PGC demodulation methods - Google Patents
A kind of improved generation carrier phase PGC demodulation methods Download PDFInfo
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Abstract
Present invention design belongs to fibre optic interferometer fields of measurement, and in particular to a kind of improved generation carrier phase PGC demodulation methods.Improved generation carrier phase PGC demodulation methods, the first via fixed phase drift FPS signals and the second road FPS signals exported with 3 × 3 couplers of interferometer rear end carry out FPS algorithm phase demodulatings；First via PGC signals are demodulated using phase generated carrier algorithm, are finally rationally merged two kinds of algorithm demodulation results.Fixed phase drift method based on 3 × 3 couplers is combined by the present invention with PGC algorithms, low frequency small-signal is demodulated using PGC algorithms, the big signal of high frequency is exported using FPS algorithms, the phase resolution of system can be so improved in the case where keeping original sample rate, in the case that increase dynamic range finally realizes that holding sample rate is constant, increase phase resolution and dynamic range, eliminating association amplitude modulation influences.
Description
Technical field
Present invention design belongs to fibre optic interferometer fields of measurement, and in particular to a kind of improved generation carrier phase PGC
Demodulation method.
Background technology
Interferometric optical fiber sensor is to measure physical quantity, including vibrations, stress, position using the phase place change in light path
Move, speed etc., this method has the features such as high sensitivity, the linearity is high, and volume size is small, and dynamic range is big.Typical light
Fiber sensor, which is applied, includes fibre optic hydrophone, fiber optic seismic meter, fibre strain instrument etc..Fiber optic seismic meter can monitor earthquake, core
Significantly signal, Zumberge et al. points out its dynamic range in 180dB*1kHz or so to quick-fried grade；Fibre optic hydrophone is mainly used in
To underwater not visible target, the blind area that radar can not be found out is monitored, and Scale Fiber-Optic Hydrophone Array is compared to traditional hydrophone
With the features such as good directionality, bandwidth of operation is big.Fibre strain instrument can measure the physical process of ultralow frequency, such as tide, its work
Make the minimum reachable 0.001Hz of frequency range.Needed for the phase place change in light path by specific Algorithm for Solving, conventional phase solution
Algorithm is adjusted to be divided into：Active detection, passive detection, heterodyne detection, homodyne detection etc..Phase life in wherein active zero balancing
3 × 3 fixed phase drift methods into carrier wave algorithm (PGC) and passive homodyne method, have simple in construction, specific, the quilt of high resolution
It is widely used in the sensors such as fiber optic seismic meter, Scale Fiber-Optic Hydrophone Array (CN 200810117296.X).
PGC algorithm advantages are low noise and low frequency signal are responded, but because PGC algorithms are carried out to sampling bandwidth
Limitation, the demodulation ability to the big signal of high frequency can be weakened so as to inhibit with the amplitude and frequency of demodulated signal, reduced and be
The dynamic range of system.And PGC algorithms cause system to produce larger harmonic distortion easily by association amplitude modulation effects.
Tsing-Hua University Zhang Min et al. has made in-depth study in terms of noise reduction in the fibre optic hydrophone based on PGC principles to this, including only
Vertical hydrophone (CN 201110191719.4) and multiplexing hydrophone array (CN 201210143601.9).US Naval Research Laboratory
The hydrophone correction system (B2 of US 6594198) that proposes of Michael Amaral et al. how dc shift is suppressed to PGC
Analyze.But two people do not do to the demodulated signal dynamic range for how carrying PGC algorithms with association amplitude modulation harmonics restraint
Go out to describe in detail.3 × 3 coupler fixed phase drift algorithm advantages are to make full use of sampling bandwidth, by the signal in sample frequency
Computing is all participated in, can thus demodulate the signal with higher frequency by a larger margin, but the thing followed is exactly to be coupled into
More noises, deteriorate the phase resolution of system.And 3 × 3 coupler fixed phase drift algorithm require coupler ideal it is complete
Holohedral symmetry, the output of 3 tunnels has identical splitting ratio and 120 ° of fixed skew, when splitting ratio and phase difference change and all can
Cause the deterioration of demodulation result.A kind of brave et al. portable multifunctional optical fiber hydrophone signal solution of proposition is thanked to by the research institutes of Zhong Chuan 715
PGC demodulation methods and 3 × 3 fixed phase drift demodulation methods are cured in a device by tune method (CN 200910100835.3),
But the device can not run two kinds of algorithms simultaneously, dynamic range and phase resolution can not be expanded simultaneously, is completed to harmonic wave
Suppression.
The content of the invention
It is an object of the invention to provide a kind of improved generation carrier wave for suppressing association amplitude modulation effect, extended dynamic scope
Phase PGC demodulation methods.
The object of the present invention is achieved like this：
Improved generation carrier phase PGC demodulation methods, the first via exported with 3 × 3 couplers of interferometer rear end are consolidated
Determine phase shift FPS signals and the second road FPS signals carry out FPS algorithm phase demodulatings；First via PGC signals use phase generated carrier
Algorithm is demodulated, and is finally rationally merged two kinds of algorithm demodulation results；Increase the correction of PGC ellipse fittings in PGC algorithms
Module, increase FPS ellipse fittings correction module realizes the suppression to association amplitude modulation effect respectively in FPS algorithms；Simultaneously with tested
Decision condition of the amplitude and frequency product of phase as algorithms selection, completes the fusion of PGC algorithms and FPS algorithms, and demodulation is calculated
Method includes carrier wave setting module, PGC lock phase modules, PGC ellipse fitting correction modules, PGC numeral ArcTan blocks, FPS data
Interception module, FPS ellipse fitting correction modules, FPS numeral ArcTan blocks, data fusion module composition：
(1) it is 20kHz~2MHz's that system operating carrier setting module first, wherein carrier wave output sub-module, which produce frequency,
To light modulator, modulation amplitude is arranged between pi/2 rad to π rad and maintains interference fringe sinusoidal signal according to light source state
Stable, the light after modulation is injected into interferometer；The amplifying circuit of interferometer rear end is connected to data-acquisition submodule, adopts
Sample rate is set as 100kbps~10Mbps according to frequency of carrier signal, obtains first via PGC signals, first via FPS signals and
Two road FPS signals；
(2) PGC is locked in phase module, and locally generated fundamental frequency signal and frequency-doubled signal and first via PGC signals are same respectively
When by the first lock phase submodule, the second lock phase submodule, eliminate the carrier component in interference signal, extract measured signal
Nonlinear phase shift caused by sinusoidal component, cosine component, compensated optical fiber, circuit and light source, additional phase error, according to system shape
It is 100~100000 points of each cycle that state is chosen lock and mutually counted with carrier frequency；
(3) PGC ellipse fittings correction module is used for the sinusoidal component for correcting PGC lock phase module outputs, cosine component, correction
Whether parameter updates the temporal amplitude of the output result, i.e. measured signal depending on low pass filter；
(4) PGC ellipse fittings correction module output result obtains PGC demodulation results by PGC numeral ArcTan blocks, number
Word arc tangent precision chooses 4096~12864 points according to actual conditions within 2 π cycles, and PGC demodulation results are sent into PGC data
In caching；
(5) FPS data cutouts module is used for first via FPS signals and the second road FPS signal subsections, according to system mode
Difference, the time-domain signal comprising 1~10 carrier cycle is chosen as a packet, is sent into FPS ellipse fitting correction modules
Eliminate association amplitude modulation；
(6) FPS ellipse fittings correction module is by the first via FPS signals of data packet form and the second road FPS signal corrections
For normal orthogonal signal；
(7) FPS ellipse fittings correction module is exported to FPS numeral ArcTan blocks, is solved measured signal and is exported extremely
In FPS data buffer storages, signal includes two compositions, and modulated light source signal using piezoelectric ceramic actuator and piezoelectric ceramic ring with being added
The demarcation signal of load；
(8) data fusion module chooses PGC demodulation output according to the amplitude and frequency product size of tested phase or FPS is solved
Output is adjusted to be used as demodulation result；
Described PGC ellipse fitting correction modules, correct nonlinear phase shift, and PGC ellipse fitting correcting algorithms need to meet
Signal phase change is more than π rad, PGC ellipse fitting correcting algorithm decision condition and provided by FPS numerals ArcTan block, if low
When bandpass filter output result phase place change is more than π rad, starts PGC ellipse fitting correction modules, use sinusoidal component, cosine
Component construction PGC ellipse matrixes, and PGC Data corrections are used for by PGC ellipse Matrix Solving PGC elliptic parameters, the parameter；If
Low pass filter output result phase place change is then updated less than π rad without elliptic parameter, and PGC numbers are carried out using parameter before
According to correction；
Described FPS data cutout modules, choose time-domain signal and handled, ensure the phase for including π rad in data segment
Change, 1~10 modulating wave periodic signal is chosen according to system mode；
Described FPS ellipse fitting correction module input signals phase place change is more than π rad, according to carrier wave output sub-module
Modulation amplitude is pi/2 rad to π rad, constructs FPS ellipse matrixes using the output result of FPS data cutout modules, utilizes matrix
FPS elliptic parameters are solved, FPS Data corrections are carried out using FPS elliptic parameters；
Described data fusion module is chosen PGC algorithms according to the amplitude and frequency product size of tested phase and calculated with FPS
Final result of the optimal output result of method as system, FPS numeral ArcTan blocks output result separate by low pass filter
Modulation of source carrier signal and demarcation signal, wherein low pass filter parameter select according to carrier signal parameter, including wave filter
Band connection frequency between 10kHz~1MHz, the rate of decay is at least 60dB~120dB, and FPS demodulation results are put into FPS data
In caching；PGC numeral ArcTan block results are put into PGC data buffer storages, and result judgement submodule reads the two caching numbers
According to；
The output result decision sub-module, by data read module, frequency spectrum computing module, output selecting module composition：
PGC cachings are read out in data read module, FPS cachings is read, obtains PGC data and FPS data；
PGC data obtain PGC frequency data by Fourier transformation submodule, and PGC amplitude datas and PGC frequency data are same
When input multiplier；
Selecting module is exported according to PGC amplitude datas and PGC frequency data product sizes, frequency of carrier signal, which is made, to be sentenced
Disconnected, system carrier 10MHz, when product value is less than 1rad*10MHz, using PGC data as demodulation result, product value is more than
During 1rad*10MHz, demodulation result is used as using FPS data.
The beneficial effects of the present invention are：
The present invention discloses a kind of Larger Dynamic scope interference phase demodulation method suppressed with association amplitude modulation, will be based on 3 × 3
The fixed phase drift method of coupler is combined with PGC algorithms, and low frequency small-signal is demodulated using PGC algorithms, is exported using FPS algorithms high
Frequently big signal, the phase resolution of system can be so improved in the case where keeping original sample rate, increases dynamic range；
Because for whole process easily by because of association amplitude modulation effects caused by modulated light source, the inside adds ellipse fitting correction
Algorithm is used to suppress because of association amplitude modulation and the undesirable caused phase of 3 × 3 couplers, demodulation result caused by light intensity asymmetry
Harmonic wave increases problem.In the case that final realization keeps sample rate constant, increase phase resolution and dynamic range, eliminate association
Amplitude modulation influences.
Brief description of the drawings
Fig. 1 is a kind of Larger Dynamic scope interference phase demodulation method flow diagram suppressed with association amplitude modulation；
Fig. 2 is interferometer modulation /demodulation detection light path device figure；
Fig. 3 is that ellipse fitting correcting algorithm eliminates association amplitude modulation effect drafting lee sajous graphics；
Fig. 4 is that PGC is combined expansion dynamic range with FPS algorithms；
Fig. 5 is harmonic distortion inhibition of the ellipse fitting correcting algorithm to final demodulation result；
Fig. 6 is output result determination module workflow diagram.
Embodiment
To clearly demonstrate a kind of Larger Dynamic scope interference phase demodulation method suppressed with association amplitude modulation, with reference to implementation
The invention will be further described with accompanying drawing for example, but should not be limited the scope of the invention with this.
The present invention provides a kind of suppression association amplitude modulation effect, the interference phase demodulation method of extended dynamic scope, its feature
Be in fibre optic interferometer 3 × 3 couplers export the interference signal with fixed phase difference, two-by-two difference, remove removing DC bias after,
Using fixed phase drift (FPS) algorithm demodulation phase signal；Remaining interference signal is carried out using phase generated carrier (PGC) algorithm
Demodulation；Decision condition of the amplitude and frequency product of tested phase as algorithms selection, completes the organic of PGC and FPS algorithms and melts
Close, realize the extension of dynamic range；The ellipse fitting correcting algorithm each added in PGC and FPS algorithms, eliminate frequency
The association amplitude modulation effect of rate modulation, while suppress the non-ideal caused phase demodulating harmonic distortion of FPS algorithm parameters.This method
The dynamic range of interference phase demodulation system can be effectively increased, signal measurement precision is improved, suppresses the harmonic distortion of signal, can be wide
It is general to be used for the fields such as high-precision optical fiber measurement and Fibre Optical Sensor.
Compared with prior art, the advantage of the invention is that：
(1) phase resolution and dynamic range of interference signal demodulation method are improved, is not changing hardware spending and phase
On the premise of bit resolution, dynamic range is set to improve more than 10dB；
(2) effectively suppress that association amplitude modulation effect produces caused by modulation of source and 3 × 3 couplers are non-ideal causes light intensity
Do not wait, influence of the phase asymmetry to signal demodulation accuracy, effectively inhibit harmonic wave, improve the signal to noise ratio of demodulated signal.
(3) size is small, low in energy consumption, and the change of software program is carried out on the basis of original hardware spending, does not increase extra
Cost, it is good with existing system compatibility.
1. a kind of improved generation carrier phase (PGC) demodulation method, it is characterized in that, utilize the 3 × 3 of the rear end of interferometer 21
The first via fixed phase drift FPS signals 171 and the second road FPS signals 172 that coupler 221 exports carry out FPS algorithm phase demodulatings；
First via PGC signals 111 are demodulated using phase generated carrier (PGC) algorithm, finally carry out two kinds of algorithm demodulation results
Rationally fusion；Increase PGC ellipse fittings correction module 12 in PGC algorithms, increase FPS ellipse fitting correction modules in FPS algorithms
16 realize the suppression to association amplitude modulation effect respectively；Simultaneously using amplitude and frequency product the sentencing as algorithms selection of tested phase
Fixed condition, the fusion of PGC algorithms and FPS algorithms is completed, realizes the extension of dynamic range.Demodulating algorithm includes carrier wave setting mould
Block 10, PGC lock phase modules 11, PGC ellipse fittings correction module 12, PGC numerals ArcTan block 13, FPS data cutout modules
17, FPS ellipse fitting correction modules 16, FPS numerals ArcTan block 15, data fusion module 14 forms.Comprise the following steps that：
1) system operating carrier setting module 10 first, wherein carrier wave output sub-module 104 produce frequency be 20kHz~
2MHz sinusoidal signal is arranged between pi/2 rad to π rad simultaneously to light modulator 252, modulation amplitude according to the state of light source 201
Maintain interference fringe stable, the light after modulation is injected into interferometer 21；The amplifying circuit 24 of the rear end of interferometer 21 connects
To data-acquisition submodule 103, sample rate is set as 100kbps~10Mbps according to frequency of carrier signal, obtains first via PGC
Signal 111, first via FPS signals 171 and the second road FPS signals 172.
2) PGC is locked in phase module 11, locally generated fundamental frequency signal 112 and frequency-doubled signal 115 and first via PGC signals
111 respectively simultaneously by first, second lock phase submodule 113,114, and submodule effect is the carrier wave in elimination interference signal
Composition, extracts the sinusoidal component 116 of measured signal, cosine component 117, compensated optical fiber, non-thread caused by circuit and light source
Property phase shift, additional phase error, choosing lock according to system mode and carrier frequency, mutually points are 100~100000 points of each cycle.
3) PGC ellipse fittings correction module 12 is used to correct the sinusoidal component 116 that PGC lock phase modules 11 export, cosine point
Whether amount 117, correction parameter update the temporal amplitude of the output result, i.e. measured signal depending on low pass filter 144.
4) output result of PGC ellipse fittings correction module 12 obtains PGC demodulation knots by PGC numerals ArcTan block 13
Fruit, digital arc tangent precision choose 4096~12864 points according to actual conditions within 2 π cycles, and PGC demodulation results are sent into PGC
In data buffer storage 141.
5) FPS data cutouts module 17 is used to first via FPS signals 171 and the second road FPS signals 172 being segmented, according to
System mode is different, chooses the time-domain signal comprising 1~10 carrier cycle as a packet, is sent into FPS ellipse fittings
Correction module 16, this operation purpose is to eliminate association amplitude modulation.
6) FPS ellipse fittings correction module 16 is by the first via FPS signals 171 of data packet form and the second road FPS signals
172 are corrected to normal orthogonal signal.
7) FPS ellipse fittings correction module 16 is exported to FPS numerals ArcTan block 15, is solved measured signal and is exported
Into FPS data buffer storages 143.The signal includes two compositions, and modulated light source signal is with utilizing piezoelectric ceramic actuator 251 and pressure
The demarcation signal that electroceramics ring 213 loads.
8) data fusion module 14 chooses PGC demodulation output or FPS according to the amplitude and frequency product size of tested phase
Demodulation output is used as demodulation result.
PGC ellipse fittings correction module 12 described in 2., it is characterised in that amendment association amplitude modulation and device is undesirable makes
Into nonlinear phase shift.PGC ellipse fitting correcting algorithms need to meet that signal phase change is more than π rad and could used, and PGC is ellipse
Circle fitting correction algorithm decision condition 121 is provided by FPS numerals ArcTan block 15, if the output result phase of low pass filter 144
When position change is more than π rad, start PGC ellipse fittings correction module 12, using sinusoidal component 116, cosine component 117 constructs PGC
Oval matrix 122, and PGC elliptic parameters 123 are solved by PGC ellipses matrix 122, the parameter is used for PGC Data corrections 124；
Update without elliptic parameter if the output result phase place change of low pass filter 144 is less than π rad, carried out using parameter before
PGC Data corrections 124.
FPS data cutouts module 17 described in 3., it is characterised in that at the time-domain signal for choosing certain data length
Manage, selection principle is to ensure that the phase place change comprising π rad in data segment and can not spend the multicycle comprising association amplitude modulation, root
1~10 modulating wave periodic signal is chosen according to system mode.
FPS ellipse fittings correction module 16 described in 4., it is characterised in that eliminate the association amplitude modulation effect and 3 in light path
The device asymmetry of × 3 couplers.FPS ellipse fittings correction module 16 needs to meet that input signal phase place change is more than π rad
Ability normal work, is pi/2 rad to π rad according to the modulation amplitude of carrier wave output sub-module 104, now system can carry out PGC
Resolve, and can makes FPS ellipse fittings correction module 16 meet entry condition.Use the output result of FPS data cutouts module 17
FPS ellipses matrix 163 is constructed, using Matrix Solving FPS elliptic parameters 162, finally carries out FPS using FPS elliptic parameters 162
Data correction 161.
Data fusion module 14 described in 5., it is characterised in that chosen according to the amplitude of tested phase and frequency product size
PGC algorithms and final result of the optimal output result of FPS algorithms as system.The output result of FPS numerals ArcTan block 15 passes through
Cross the separation modulation of source carrier signal of low pass filter 144 and demarcation signal, the wherein parameter of low pass filter 144 are believed according to carrier wave
The selection of number parameter, including wave filter band connection frequency between 10kHz~1MHz, the rate of decay be at least 60dB~120dB or
Higher, FPS demodulation results are put into FPS data buffer storages 143 afterwards；Likewise, the result of PGC numerals ArcTan block 13 is put into
In PGC data buffer storages 141.It is data cached that result judgement submodule 142 reads the two.
6. the output result decision sub-module 142, it is characterised in that by data read module 60, frequency spectrum computing module
61, output selecting module 62 forms.Detailed process is as follows：
1) PGC cachings 601 are read out in data read module 60, the operation of FPS cachings 602 is read, obtains PGC data
603 with FPS data 604.
2) PGC data 603 obtain PGC frequency data 612, PGC amplitude datas 614 by Fourier transformation submodule 611
Multiplier 613 is inputted with PGC frequency data 612 simultaneously.
3) selecting module 62 is exported according to PGC amplitude datas 614 and the product size of PGC frequency data 612, carrier signal frequency
Rate judges.System carrier is 10MHz, when product value is less than 1rad*10MHz, using PGC data 603 as demodulation result,
When product value is more than 1rad*10MHz, demodulation result is used as using FPS data 604.
7. in PGC numerals ArcTan block 13 described in, it is anti-that the output data of PGC ellipse fittings correction module 12 carries out PGC
Tangent 131 is handled, and obtains result and carry out PGC tabling look-up 132 operations.
8. in FPS numerals ArcTan block 15 described in, it is anti-that the output data of FPS ellipse fittings correction module 16 carries out FPS
Tangent 152 is handled, and obtains result and carry out FPS tabling look-up 151 operations.
This algorithm is used for the phase demodulating for solving interferometer, and interferometer basic structure is as shown in Fig. 2 work as software systems 253
When producing carrier (boc) modulated signals modulated light source 201 by light modulator 252, the optical signal modulated passes through the note of isolator 202
Enter into interferometer 21.The reference arm of interferometer is made up of fiber optic loop 212, and signal arm is harassed and disturbed to piezoelectric ceramic ring 213, light
The optical signal that source output module 20 is sent interferes in 3 × 3 couplers 221 of interferometer end, produces 3 groups of light intensity magnitudes
Interference signal identical, that phase difference is fixed.This group of signal passes through the 21 × 2nd coupler 223, and the 31 × 2nd coupler 224 is with declining
5 tunnel light intensity magnitude identical interference signals are obtained after subtracting device 222, can be expressed as：
Wherein PijAny 3 tunnel output of output and two 1 × 2 couplers for attenuator, PPGCTo be remaining defeated all the way
Go out.M is association amplitude modulation coefficient, ω0For carrier (boc) modulated signals frequency, Ai, BiThe respectively DC magnitude and AC-amplitudes of light intensity,
A, B are similarly the DC magnitude and AC-amplitudes of light intensity, and C is modulation depth,For the demarcation signal on piezoelectric ceramic ring.
Here we assume that the splitting ratio of coupler is identical, i.e. 5 tunnel output signals except keeping identical simultaneously with fixed phase difference
Light intensity.Choose two groups of differential signals expressed in formula 1 and enter the difference photoelectricity of the first difference photodetector 231 second
In detector 232, remaining signal all the way is input in a single-ended detector 233.Differential signal is in the first operational amplifier
235 and second carry out calculus of differences in operational amplifier 234, obtain removing the exchange interference signal of DC quantity, can be by following public
Formula represents：
Wherein P1P2For differential detector output signal,For the fixed skew of two paths of signals.
To the signal P in the cycle after interception1With P2It is sent into ellipse fitting correction module 16.The use of ellipse fitting correction
Condition is that two groups of curves for being fitted correction include phase place change more than π rad, and now we set modulation depth C>π/
2, can now ellipse fitting correcting algorithm be used to data.Ellipse fitting correction detailed process is to use a periodic sampling number
According to PGC ellipses matrix 163 is constructed, the design parameter 162 of fitted ellipse can be solved by the oval matrix operation, by ellipse
Parameter is substituted into elliptic equation：
Wherein δ is P1With P2Fixed skew.By least square method, the data in a cycle are fitted, obtain the party
The coefficient of journey, and the equation is turned into standard equation of a circle, you can obtain normal orthogonal signal：
Wherein PIWith PQFor normal orthogonal signal, p and q is the range error brought in fit procedure, after Δ δ is correction, partially
Phase from 90 °, fitting correction process accompanying drawing 3 illustrate.Correct to obtain normal orthogonal curve P by ellipse fittingIWith PQ(error
Very little) using arc tangent program 152 sine value of tested phase signal is obtained, then obtained using arc tangent inquiring arithmetic 151
Measured signal.Measured signal herein includes 2 amounts, modulated signal Ccos ω0T and measured signalPass through low pass filter
144 can obtain measured signalIt is sent into by FPS data buffer storages 143 in output result determination module 142.
Single-ended detector output signal passes through acquisition module 254, obtains the interference signal such as institute of formula 2 for including carrier wave
Show, many harmonic components are included inside interference signal, extracted respectively by the first lock lock phase module 113 of phase module 112, second humorous
Wave component calculates as rear end, and in the ideal case, fundamental frequency should be sinusoidal point with the harmonic component obtained after frequency multiplication lock phase
Amount 116 and cosine component 117, but due to the influence of modulation of source signal, association amplitude modulation effect can be produced, in sinusoidal component
On the basis of be superimposed a DC component, be by two components mutually obtaining of lock now：
Wherein C is modulation depth, and D is signal amplitude, Jk(C) it is Bessel function coefficient, the signal is because be not standard
Orthogonal signalling, so directly can not be solved using digital arc tangent program, it is necessary to by fitting correction algorithm by direct current
Biasing eliminates.
The use condition of ellipse fitting correction is that the phase that two groups of curves for being fitted correction include more than π rad becomes
Change, so now first to judge signal according to the output result of 3 × 3 couplersChange size, whenChange is super
It when crossing π rad, can now start ellipse fitting algorithm, elliptic parameter calculating is carried out to data again, works as signalChange
During not less than π rad, according to being corrected, its detailed process is the fitted ellipse parameter logistic before can using：JudgeLetter
Number change size, confirmation signal change exceed π rad, using the oval matrix of sampled data construction, obtained by oval Matrix Calculating oval
Parameter, parameter are included ellipse diameter, origin position, two signal phase differences, input data are corrected using above parameter, obtained
To normal orthogonal signal.
The dynamic range of embodiment 1 --- phase demodulating system is expanded
Interferometer is as shown in Fig. 2 the device selection of interfering meter measuring device is as follows with parameter：
(1) the centre wavelength 1550nm of light source 201, half spectral width are more than 45nm, and fiber power is 1mW~10mW；
(2) the operation wavelength 1550nm ± 5nm of fibre optic isolater 222, insertion loss≤1.0dB (during 23 DEG C of operating temperatures),
Return loss >=55dB；
(3) the one 1 × 2nd couplers 211, the 21 × 2nd coupler 223, the 31 × 2nd coupler 224, operation wavelength
1550nm＆1310nm, splitting ratio 50.5%/49.5%, two-way insertion loss are respectively 3.03dB, 3.12dB；
(4) the piezoelectric ceramics size for being used to load demarcation signal is 24mm, electric capacity 22nF, pressure-resistant 0~120V of amplitude；
The operation wavelength 1550nm of (5) 3 × 3 coupler 221, inputted using 1 port and 3 ports of 3 × 3 couplers, 1 port
The corresponding 3 tunnels output splitting ratio of input is (34.9%, 33.6%, 31.5%), and input corresponding 3 tunnels output splitting ratio in 3 ports is
(31.8%, 35.7%, 32.5%)；
(6) fibre optic attenuator 222 operation wavelength 1550nm＆1310nm, joint categories FC/PC, pad value is adjustable 1~
30dB；
(7) photodetector 233 is InGaAs type photodetectors, and connection mode belongs to tail-fiber type FC/PC, operation wavelength
For 1100nm~1650nm, Intensity response degree R=0.85A/W, electric capacity 0.35pF；
(8) differential detector 235 is ADI companies low voltage difference track to track operational amplifier A DA4610-2, operating voltage ±
4.5V~± 15V, quiescent bias current 5pA, low noise 7.3nV/ √ Hz*1kHz；
(9) amplifier 24 is used to amplify the photoelectric signal after conversion, bandwidth of operation 200kHz, and the course of work includes making
Signal amplitude is gathered with MSP430 single-chip microcomputers, Regulate signal gain, ensures that signal amplitude can't saturation；
(10) acquisition module 254 is NI-6366 capture cards, sample rate 2Mbps, 3 road synchronous acquisitions, input voltage amplitude
± 10V, sampling clock are capture card internal clocking, and three tunnel synchronous errors are less than 10ns, input resistance 20k Ω；
(11) light modulator 252 is power amplifier, uses the AD8040 track to track power amplifiers of AD companies, work
Voltage 2.7V~12V, bandwidth of operation 125MHz, maximum output current 200mA, load capacitance 15pF；
System phase demodulation idiographic flow is as shown in Figure 1：
(1) light modulator produces carrier wave, sample rate 2Mbps, carrier frequency 20kHz, and piezoelectric ceramics produces demarcation
Signal, frequency 10Hz, as modulation voltage increases, produce light path phase place change 10-5Rad~105rad；
(2) as shown in Equation 2, signal peak-to-peak value is 8V to difference photodetector collection signal；
(3) processing data of FPS ellipse fittings correction module 16 points are 100, i.e. a cycle letter of 20kHz carrier datas
Number, elliptic parameter is solved with the data point, obtaining result is：Oval axial length a=0.95, b=1.08, oval home position h=
0.139, k=-0.11, phase difference δ=2.14 °；
(4) use above parameter carries out ellipse fitting correction, obtains the orthogonal letter with certain error described by formula 4
Number, using digital arc tangent program solution signal, tangent is tabled look-up to carry out 4096 subdivisions in the range of 0~π/4, and precision of tabling look-up is
12bit；
(5) FPS numerals ArcTan block 15 tries to achieve signal and includes carrier wave and demarcation signal, and setting filter module 144 is
FIR equiripple filters, parameter are passband 10kHz, cut stopband 12kHz, decay -120dB, passband ripple 0.01dB, exponent number
For 764 ranks, data obtain demarcation signal after device after filtering, and it is ellipse with PGC that demarcation signal is sent into output result decision sub-module 142
In circle fitting correction judging module 121；
(6) PGC gathers signal as shown in Equation 6, obtains the interference signal for including direct current biasing, signal peak-to-peak value is
4V, direct current biasing are 2V or so；
(7) phase locking operation is carried out to interference signal, obtains the sinusoidal component and cosine component of test signal, but due to companion
The influence of raw amplitude modulation, resulting signal is as shown in Equation 7；
(8) judged whether to use ellipse fitting correcting algorithm to PGC signals according to FPS algorithm demodulated signal amplitudes, if
The condition of satisfaction can use ellipse fitting correcting algorithm renewal elliptic parameter, correct association amplitude modulation error；
(9) data after ellipse fitting correction calculate actual phase by digital ArcTan block 13；
(10) final system output result is exported by signal amplitude and frequency more than a certain range signal by FPS algorithms, width
Degree and frequency are exported less than a certain range signal by PGC algorithms；Measured signal frequency is 10Hz, carrier frequency 20kHz, is such as schemed
Shown in 6, when 10Hz signal amplitudes are 20rad and below 20rad, i.e., when amplitude-frequency product size is less than 200 (rad Hz),
System is exported using PGC algorithms, and when the signal amplitude is more than 20rad, system is exported using FPS algorithms demodulation result.
(11) as shown in figure 4, PGC algorithms are good to small-signal response, minimum test point is 5 × 10-5Rad, full test point
For 20rad, its effective dynamic range is 150.59dB；FPS algorithms have more preferable dynamic range, minimum test point to big signal
For 2 × 10-3Rad, full test point are 5000rad, and its dynamic range is 168.86dB；Signal amplitude is 10-2Rad~20rad
Interior two kinds of algorithm demodulation results are consistent, exported so we choose small-signal using PGC algorithms, and big signal is defeated using FPS algorithms
Go out, now dynamic range can be expanded to 181.7dB；
Embodiment 2 --- PGC algorithm association amplitude modulation effect suppresses
The device selection that PGC algorithm association amplitude modulation effect suppresses measurement apparatus is as follows with parameter：
(1) the centre wavelength 1550nm of light source 201, half spectral width are more than 45nm, and fiber power is 1mW~10mW；
(2) the operation wavelength 1550nm ± 5nm of fibre optic isolater 222, insertion loss≤1.0dB (during 23 DEG C of operating temperatures),
Return loss >=55dB；
(3) the one 1 × 2nd couplers 211, the 21 × 2nd coupler 223, the 31 × 2nd coupler 224, operation wavelength
1550nm＆1310nm, splitting ratio 50.5%/49.5%, two-way insertion loss are respectively 3.03dB, 3.12dB；
(4) the piezoelectric ceramics size for being used to load demarcation signal is 24mm, electric capacity 22nF, pressure-resistant 0~120V of amplitude；
The operation wavelength 1550nm of (5) 3 × 3 coupler 221, inputted using 1 port and 3 ports of 3 × 3 couplers, 1 port
The corresponding 3 tunnels output splitting ratio of input is (34.9%, 33.6%, 31.5%), and input corresponding 3 tunnels output splitting ratio in 3 ports is
(31.8%, 35.7%, 32.5%)；
(6) fibre optic attenuator 222 operation wavelength 1550nm＆1310nm, joint categories FC/PC, pad value is adjustable 1~
30dB；
(7) photodetector 231 is InGaAs type photodetectors, and connection mode belongs to tail-fiber type FC/PC, operation wavelength
For 1100nm~1650nm, Intensity response degree R=0.85A/W, electric capacity 0.35pF；
(8) differential detector 235 is ADI companies low voltage difference track to track operational amplifier A DA4610-2, operating voltage ±
4.5V~± 15V, quiescent bias current 5pA, low noise 7.3nV/ √ Hz*1kHz；
(9) amplifier 24 is used to amplify the photoelectric signal after conversion, bandwidth of operation 200kHz, and the course of work includes making
Signal amplitude is gathered with MSP430 single-chip microcomputers, Regulate signal gain, ensures that signal amplitude can't saturation；
(10) acquisition module 254 is NI-6366 capture cards, sample rate 2Mbps, 3 road synchronous acquisitions, input voltage amplitude
± 10V, sampling clock are capture card internal clocking, and three tunnel synchronous errors are less than 10ns, input resistance 20k Ω；
(11) light modulator 252 is power amplifier, uses the AD8040 track to track power amplifiers of AD companies, work
Voltage 2.7V~12V, bandwidth of operation 125MHz, maximum output current 200mA, load capacitance 15pF；
PGC algorithm association amplitude modulation effect suppresses test detailed process：
(1) piezoelectric ceramics produces demarcation signal amplitude and should be greater than π rad, now loads the phase place change of 8rad sizes, signal
Frequency is 97Hz, can carry out ellipse fitting correction；
(2) light modulator produces carrier signal, and it is peak-to-peak value that can now measure association amplitude modulation and produce ripple size
0.8V, interference signal peak-to-peak value size are 4V, it is possible to calculate association amplitude modulation coefficient m=0.2；
(3) PGC gathers signal as shown in Equation 6, obtains the interference signal for including direct current biasing, signal peak-to-peak value is
4V, direct current biasing are 2V or so；
(4) ellipse fitting correction is done using first via FPS signals 171 and the second road FPS signals 172, tries to achieve elliptic parameter
For：
Oval axial length a=2.04b=2.01 ellipses home position h=-0.007, k=0.06 elliptical phase difference δ=1.4 °
Use above parameter does fitting correction to input signal, obtains orthogonal curvilinear, and with digital arc tangent program solution
Phase；
(5) as shown in figure 5, significantly reducing harmonic amplitude using the demodulation result after ellipse fitting correcting algorithm, its
Middle even-order harmonic suppresses obvious；Harmonic distortion rate is 3.9% before being corrected using ellipse fitting, harmonic wave after being corrected using ellipse fitting
Distortion is suppressed to 0.04%.
Claims (1)
1. a kind of improved generation carrier phase PGC demodulation methods, the first via exported with 3 × 3 couplers of interferometer rear end
Fixed phase drift FPS signals and the second road FPS signals carry out FPS algorithm phase demodulatings；First via PGC signals are carried using phase generation
Ripple algorithm is demodulated, and is finally rationally merged two kinds of algorithm demodulation results；Increase PGC ellipse fittings school in PGC algorithms
Positive module, increase FPS ellipse fittings correction module realizes the suppression to association amplitude modulation effect respectively in FPS algorithms；Simultaneously with quilt
The decision condition of the amplitude and frequency product of phase as algorithms selection is surveyed, completes the fusion of PGC algorithms and FPS algorithms, demodulation
Algorithm includes carrier wave setting module, PGC lock phase modules, PGC ellipse fitting correction modules, PGC numeral ArcTan blocks, FPS numbers
According to interception module, FPS ellipse fitting correction modules, FPS numeral ArcTan blocks, data fusion module composition：
(1) system operating carrier setting module first, wherein carrier wave output sub-module produce the sine that frequency is 20kHz~2MHz
To light modulator, modulation amplitude is arranged between pi/2 rad to π rad and maintains interference fringe stable signal according to light source state
, the light after modulation is injected into interferometer；The amplifying circuit of interferometer rear end is connected to data-acquisition submodule, sample rate
100kbps~10Mbps is set as according to frequency of carrier signal, obtains first via PGC signals, first via FPS signals and the second tunnel
FPS signals；
(2) PGC is locked in phase module, and locally generated fundamental frequency signal passes through simultaneously respectively with frequency-doubled signal and first via PGC signals
The first lock phase submodule, the second lock phase submodule are crossed, the carrier component in interference signal is eliminated, extracts the sine of measured signal
Nonlinear phase shift caused by component, cosine component, compensated optical fiber, circuit and light source, additional phase error, according to system mode with
Carrier frequency chooses lock, and mutually points are 100~100000 points of each cycle；
(3) PGC ellipse fittings correction module is used for the sinusoidal component for correcting PGC lock phase module outputs, cosine component, correction parameter
Whether update the temporal amplitude of the output result, i.e. measured signal depending on low pass filter；
(4) PGC ellipse fittings correction module output result obtains PGC demodulation results by PGC numeral ArcTan blocks, and numeral is anti-
Tangent precision chooses 4096~12864 points according to actual conditions within 2 π cycles, and PGC demodulation results are sent into PGC data buffer storages
In；
(5) FPS data cutouts module is used for first via FPS signals and the second road FPS signal subsections, according to system mode not
Together, the time-domain signal comprising 1~10 carrier cycle is chosen as a packet, is sent into FPS ellipse fitting correction modules and is disappeared
Except association amplitude modulation；
(6) first via FPS signals of data packet form and the second road FPS signal corrections are mark by FPS ellipse fittings correction module
Quasi- orthogonal signalling；
(7) FPS ellipse fittings correction module is exported to FPS numeral ArcTan blocks, is solved measured signal and is exported to FPS numbers
According in caching, signal includes two compositions, and modulated light source signal loads with utilization piezoelectric ceramic actuator and piezoelectric ceramic ring
Demarcation signal；
(8) data fusion module chooses PGC demodulation output according to the amplitude and frequency product size of tested phase or FPS demodulation is defeated
Go out as demodulation result；
Described PGC ellipse fitting correction modules, correct nonlinear phase shift, and PGC ellipse fitting correcting algorithms need to meet signal
Phase place change is more than π rad, PGC ellipse fitting correcting algorithm decision condition and provided by FPS numerals ArcTan block, if low pass filtered
When ripple device output result phase place change is more than π rad, starts PGC ellipse fitting correction modules, use sinusoidal component, cosine component
PGC ellipse matrixes are constructed, and PGC Data corrections are used for by PGC ellipse Matrix Solving PGC elliptic parameters, elliptic parameter；It is if low
Bandpass filter output result phase place change is then updated less than π rad without elliptic parameter, and PGC data are carried out using parameter before
Correction；
Described FPS data cutout modules, choose time-domain signal and handled, ensure that the phase comprising π rad becomes in data segment
Change, 1~10 modulating wave periodic signal is chosen according to system mode；
Described FPS ellipse fitting correction module input signals phase place change is more than π rad, is modulated according to carrier wave output sub-module
Amplitude is pi/2 rad to π rad, constructs FPS ellipse matrixes using the output result of FPS data cutout modules, utilizes Matrix Solving
FPS elliptic parameters, FPS Data corrections are carried out using FPS elliptic parameters；
Described data fusion module chooses PGC algorithms and FPS algorithms most according to the amplitude and frequency product size of tested phase
Final result of the excellent output result as system, FPS numeral ArcTan blocks output result is by low pass filter separation light source
Carrier signal and demarcation signal are modulated, wherein low pass filter parameter selects according to carrier signal parameter, including wave filter is logical
Band frequency is between 10kHz~1MHz, and the rate of decay is at least 60dB~120dB, and FPS demodulation results are put into FPS data buffer storages
In；PGC numeral ArcTan block results are put into PGC data buffer storages, and it is data cached that result judgement submodule reads the two；
The result judgement submodule, by data read module, frequency spectrum computing module, output selecting module composition：
PGC cachings are read out in data read module, FPS cachings is read, obtains PGC data and FPS data；
PGC data obtain PGC frequency data by Fourier transformation submodule, and PGC amplitude datas are simultaneously defeated with PGC frequency data
Enter multiplier；
Output selecting module judges according to PGC amplitude datas and PGC frequency data product sizes, frequency of carrier signal, is
System carrier wave is 10MHz, and when product value is less than 1rad*10MHz, using PGC data as demodulation result, product value is more than 1rad*
During 10MHz, demodulation result is used as using FPS data.
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| CN108007340B (en) * | 2017-10-24 | 2019-12-06 | 浙江理工大学 | real-time calculation method for nonlinear error in phase generation carrier arc tangent demodulation |
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| CN110411334B (en) * | 2019-07-01 | 2021-04-06 | 上海工程技术大学 | Improved phase carrier PGC demodulation method and system |
| CN110429987B (en) * | 2019-07-31 | 2020-08-04 | 中船海洋探测技术研究院有限公司 | Phase generation carrier demodulation system based on FPGA |
| CN111504351A (en) * | 2020-04-26 | 2020-08-07 | 武汉理工大学 | Device and method for online correcting phase demodulation error of 3 × 3 coupler |
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