CN118551137B - Improved phase demodulation algorithm and device - Google Patents
Improved phase demodulation algorithm and device Download PDFInfo
- Publication number
- CN118551137B CN118551137B CN202410996011.3A CN202410996011A CN118551137B CN 118551137 B CN118551137 B CN 118551137B CN 202410996011 A CN202410996011 A CN 202410996011A CN 118551137 B CN118551137 B CN 118551137B
- Authority
- CN
- China
- Prior art keywords
- signal
- phase
- coupler
- phase delay
- algorithm
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000012545 processing Methods 0.000 claims description 19
- 238000001914 filtration Methods 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 14
- 238000005305 interferometry Methods 0.000 abstract description 2
- 230000003287 optical effect Effects 0.000 abstract description 2
- 239000000284 extract Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000013307 optical fiber Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000013480 data collection Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000004069 differentiation Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Abstract
The invention discloses an improved phase demodulation algorithm and device, and belongs to the technical field of optical interferometry. Extracting a phase delay term through the orthogonal signal, then eliminating the phase delay term in the orthogonal signal by using a divider, and eliminating the influence of light source power fluctuation, phase delay and modulation depth on the signal to be tested by combining a Bessel recursion formula; the demodulation algorithm does not introduce arctangent operation, and the demodulation result does not introduce nonlinear distortion; the demodulation result of the algorithm of the invention does not contain the light intensity B and the phase delaySignal distortion caused by light source power fluctuation and phase delay can be effectively restrained.
Description
Technical Field
The invention relates to the technical field of optical interferometry, in particular to an improved phase demodulation algorithm and an improved phase demodulation device.
Background
Interferometric sensors are fabricated using the principle that coherent light encounters while interfering. The phase generation carrier modulation and demodulation technology has the advantages of good linearity, large dynamic range and high accuracy of measuring phase, and is widely applied to optical fiber hydrophones, accelerometers, magnetometers and large-scale interference optical fiber sensor arrays. Taking a michelson fiber optic sensor as an example, when the length of the fiber or the refractive index of the core changes, a phase delay is introduced, resulting in a change in the phase detected by the interferometer.
The most classical phase-generating carrier-demodulation techniques are the differential cross-multiply algorithm (PGC-DCM) and the arctangent algorithm (PGC-Arctan). The PGC-DCM algorithm firstly extracts orthogonal signals from interference signals, and then demodulates the phase to be detected by utilizing the operations of a differentiator, a multiplier, an integrator and the like, and the basic principle is that the frequency of the interference signals is subjected to low-pass filtering, differentiation, cross multiplication, difference making, integration and high-pass filtering in sequence to demodulate the detected signals, and the power fluctuation of a light source, the carrier phase delay and the modulation depth all have influence on the demodulation precision; the PGC-Arctan algorithm also needs to obtain the quadrature signal first, and then uses the divider, arctangent operation, integrator, etc. to demodulate the signal to be measured, and the PGC-Arctan algorithm is not affected by the power fluctuation and modulation depth of the light source, but the carrier phase delay also affects the signal to be measured.
Comparison shows that the PGC-DCM operation result has a linear relation with the phase to be detected, but is easily affected by the fluctuation of the light source power, the phase delay and the modulation depth, and the demodulation precision is affected. The PGC-Arctan algorithm omits complex operations such as differential cross multiplication, subtraction, integration and the like, eliminates the influence of light source power fluctuation, is still influenced by phase delay and modulation depth, and the arctangent operation can introduce nonlinear errors.
In view of the above, aiming at the phase delay problem in PGC demodulation, the method extracts the phase delay term through the quadrature signal, eliminates the phase delay term in the quadrature signal by using the divider, and eliminates the influence of the power fluctuation of the light source, the phase delay and the modulation depth on the signal to be measured by combining the Bessel recurrence formula; the demodulation algorithm does not introduce arctangent operation, and the demodulation result does not introduce nonlinear distortion; the demodulation result of the algorithm of the invention does not contain the light intensity B and the phase delayThe method can effectively inhibit signal distortion caused by light source power fluctuation and phase delay, is more stable than a PGC-DCM algorithm and a PGC-Arctan algorithm, and has higher demodulation accuracy.
Disclosure of Invention
In view of the above problems, an improved phase demodulation algorithm and apparatus are provided for extracting a phase delay term from a quadrature signalThen eliminating phase delay term in quadrature signal by dividerAnd then, the Bessel recursion formula is utilized, so that the influence of the power fluctuation of the light source, the phase delay and the modulation depth on the signal to be detected can be eliminated.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows.
An improved phase demodulation algorithm comprising the steps of:
Step 1: the current expression of the interference light signal output by the interferometer is
Wherein A is the direct current of the interference signal; b is the light intensity, where b=ka, (0 < k < 1), k is the interference fringe visibility; c is modulation depth, which is the amplitude of the phase carrier introduced by the interferometer; omega 0 is the frequency of the modulated signal; the phase delay is phi (t) and the phase to be detected is phi (t);
step 2: the current expression of step 1 is expanded by Bessel function, and the current expansion is obtained as follows
Wherein J n (C) is an n-order Bessel function;
Step 3, multiplying the current expansion of step 2 by sinw 0t、cosw0 t and sin2w 0t、cos2w0 t respectively, integrating and reducing the difference formula, and respectively filtering out all w 0 and frequency multiplication terms thereof by low-pass filtering to obtain
Step 4: squaring and adding X 11, X 12、Y11 and Y 12 in step 3
Step 5: for step 4AndAnd respectively taking absolute values after square opening to obtain:
Step 6: dividing X 12、Y12 in step 3 by X 21、Y21 in step 5 respectively
Step 7: step 6Respectively corresponding to and dividing the X 12、Y12 in the step 3 to obtain
Step 8: low-pass filtering the current expansion in the step 2 to remove all w 0 and its frequency multiplication term to obtain
Z＝BJ0(C)cosφ(t)
Step 9: and (3) respectively carrying out bias guide on Y in the step 7 and Z in the step 8 to obtain:
Y′＝BJ2(C)sinφ(t)φ′(t)
Z′＝-BJ0(C)sinφ(t)φ′(t)
Step 10: dividing Y 'and Z' in step 9 by X in step 7, respectively, to obtain
Step 11: step 10AndSubtracting to obtain
Step 12: the step 11 is performed by Bessel recursion formulaSimplifying to obtain
Step 13: and (3) sequentially integrating and high-pass filtering the phi' (t) in the step 12, and obtaining a demodulation result I out as follows:
wherein C is a constant value, then Is constant and the demodulation result I out does not contain the light intensity B and the phase delaySignal distortion caused by light source power fluctuation and phase delay can be effectively restrained.
Preferably, the Bessel function in the step 2 is that
Wherein J n (z) is an n-th order Bessel function.
Preferably, the integral sum and difference formula in the step 3 is as follows
cosαcosβ＝[cos(α+β)+cos(α-β)]/2
cosαsinβ＝[sin(α+β)-sin(α-β)]/2)
Wherein alpha and beta are angles, and have no physical meaning.
Preferably, the Bessel recurrence formula in the step 12 is as follows
Wherein J n (x) is an n-th order Bessel function.
The phase demodulation device comprises a laser, a circulator, a 1x2 coupler, an unbalanced interferometer, a photoelectric detector, a data acquisition card and a signal processing module; the laser generated by the laser sequentially passes through the circulator and the 1x2 coupler and then enters the unbalanced interferometer, the unbalanced interferometer detects an external vibration signal and then returns to the 1x2 coupler, an interference light signal is generated in the 1x2 coupler, the interference signal is collected by the data acquisition card after passing through the circulator and the photoelectric detector and is output to the data processing module, and the data processing module demodulates the external vibration signal.
Preferably, the unbalanced interferometer comprises a sensing arm, a reference arm, a Faraday rotary mirror I and a Faraday rotary mirror II; the arm lengths of the sensing arm and the reference arm are different.
Preferably, the laser generated by the laser device is split into measuring light and reference light after passing through the circulator and the 1x2 coupler in sequence, the measuring light is output to the 1x2 coupler after passing through the sensing arm and the Faraday rotating mirror I and reflected by the sensing arm, the reference light is output to the 1x2 coupler after passing through the reference arm and the Faraday rotating mirror II and reflected by the reference arm, the reflected measuring light and the reference light interfere at the 1x2 coupler and generate interference light signals, and the interference light signals enter the signal processing module after passing through the circulator, the photoelectric detector and the data acquisition card in sequence, and external vibration signals are demodulated by the signal processing module.
By adopting the technical scheme, the invention has the following beneficial effects.
(1) The invention extracts the phase delay term through the quadrature signalThen eliminating phase delay term in quadrature signal by dividerAnd then, the Bessel recursion formula is utilized, so that the influence of the power fluctuation of the light source, the phase delay and the modulation depth on the signal to be detected can be eliminated.
(2) The invention demodulates the external vibration signal through the improved phase demodulation algorithm, and the demodulation result does not contain the light intensity B and the phase delayThe method can effectively inhibit signal distortion caused by light source power fluctuation and phase delay, and has higher stability than the PGC-DCM algorithm and the PGC-Arctan algorithm.
(3) Compared with the PGC-DCM algorithm and the PGC-Arctan algorithm, the demodulation result of the inventionC is a fixed value, namely 2/C is a fixed coefficient, the demodulation result does not contain light intensity B, and the influence of light source power fluctuation on demodulation precision can be eliminated; the algorithm does not introduce arctangent operation, and the demodulation result does not introduce nonlinear distortion; at the same time, the invention eliminates the phase delay in the quadrature signal by the dividerSignal distortion caused by phase delay can be effectively restrained, and demodulation accuracy and stability are higher.
(4) The invention utilizes the characteristic that orthogonal signals can be mutually independent to extract the phase delay term from interference signalsProviding a basis for eliminating the influence of phase delay subsequently; the phase delay term in the orthogonal signal is eliminated through division operation, so that the influence of the phase delay on a demodulation result is reduced, and the accuracy and stability of a demodulation algorithm are improved; the invention utilizes the property of Bessel function to process signals through a recursive formula, eliminates the influence of light source power fluctuation, phase delay and modulation depth, further eliminates nonlinear distortion and can obviously improve the stability and accuracy of demodulation algorithm. And is widely applied to the fields of industrial detection, environmental monitoring, medical equipment, communication systems, navigation systems, remote sensing technology and the like.
Drawings
The making and using of the preferred embodiments of the present invention are discussed in detail below. It should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are provided to illustrate the manner of making and using the invention and are not intended to limit the scope of the invention, as other figures can be made from these figures by one of ordinary skill in the art without undue burden.
Fig. 1 is a schematic flow chart of the phase demodulation algorithm of the present invention.
Fig. 2 is a schematic flow chart of the device of the present invention.
FIG. 3 is a graph comparing the demodulated time domain signals of the present invention with PGC-DCM and PGC-Arctan.
FIG. 4 is a graph comparing the frequency domain signals of the demodulation of the present invention with the PGC-DCM and PGC-Arctan.
Wherein, 1-laser; 2-a circulator; a 3-1x2 coupler; 4-Faraday rotation mirror one; 5-Faraday rotating mirror II; 6-a photodetector; 7-a data acquisition card; 8-a data processing module.
Detailed Description
The making and using of the preferred embodiments of the present invention are discussed in detail below. It should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.
An improved phase demodulation algorithm comprising the following steps.
Step 1: the current expression of the interference light signal output by the interferometer is
Wherein A is the direct current of the interference signal; b is the light intensity, where b=ka, (0 < k < 1), k is the interference fringe visibility; c is modulation depth, which is the amplitude of the phase carrier introduced by the interferometer; omega 0 is the frequency of the modulated signal; The phase delay, phi (t), is the phase to be measured.
Step 2: the current expression of step 1 is expanded by Bessel function, and the current expansion is obtained as follows
Wherein J n (C) is an n-th order Bessel function.
The Bessel function in the step 2 is that
Wherein J n (z) is an n-th order Bessel function.
Step 3, multiplying the current expansion of step 2 by sinw 0t、cosw0 t and sin2w 0t、cos2w0 t respectively, integrating and reducing the difference formula, and respectively filtering out all w 0 and frequency multiplication terms thereof by low-pass filtering to obtain
The integral sum and difference formula in the step 3 is as follows:
cosαcosβ＝[cos(α+β)+cos(α-β)]/2
cosαsinβ＝[sin(α+β)-sin(α-β)]/2)
wherein alpha and beta are angles, and have no physical meaning.
Step 4: squaring and adding X 11, X 12、Y11 and Y 12 in step 3
Step 5: for step 4AndAnd respectively taking absolute values after square opening to obtain:
Step 6: dividing X 12、Y12 in step 3 by X 21、Y21 in step 5 respectively
Step 7: step 6Respectively corresponding to and dividing the X 12、Y12 in the step 3 to obtain
Step 8: low-pass filtering the current expansion in the step 2 to remove all w 0 and its frequency multiplication term to obtain
Z＝BJ0(C)cosφ(t)
Step 9: and (3) respectively carrying out bias guide on Y in the step 7 and Z in the step 8 to obtain:
Y′＝BJ2(C))sinφ(t)φ′(t)
Z′＝-BJ0(C)sinφ(t)φ′(t)
Step 10: dividing Y 'and Z' in step 9 by X in step 7, respectively, to obtain
Step 11: step 10AndSubtracting to obtain
Step 12: the step 11 is performed by Bessel recursion formulaSimplifying to obtain
The Bessel recurrence formula in the step 12 is as follows
Wherein J n (x) is an n-th order Bessel function.
Step 13: and (3) sequentially integrating and high-pass filtering the phi' (t) in the step 12, and obtaining a demodulation result I out as follows:
Wherein C is a fixed value when the system works, then Is constant and the demodulation result I out does not contain the light intensity B and the phase delaySignal distortion caused by light source power fluctuation and phase delay can be effectively restrained.
The phase demodulation device comprises a laser 1, a circulator 2, a 1x2 coupler 3, an unbalanced interferometer, a photoelectric detector 6, a data acquisition card 7 and a signal processing module; the laser generated by the laser 1 sequentially passes through the circulator 2 and the 1x2 coupler 3 and then enters an unbalanced interferometer, an external vibration signal is detected by the unbalanced interferometer and then returns to the 1x2 coupler 3, an interference light signal is generated in the 1x2 coupler 3, and the interference signal is collected by the data collection card 7 after passing through the circulator 2 and the photoelectric detector 6 and is output to the data processing module 8, and the external vibration signal is demodulated by the data processing module 8. The unbalanced interferometer comprises a sensing arm, a reference arm, a Faraday rotating mirror I4 and a Faraday rotating mirror II 5; the arm lengths of the sensing arm and the reference arm are different.
The laser generated by the laser 1 is split into measuring light and reference light after passing through the circulator 2 and the 1x2 coupler 3 in sequence, the measuring light is output to the 1x2 coupler 3 after being reflected by the sensing arm and the Faraday rotating mirror I4, the reference light is output to the 1x2 coupler 3 after being reflected by the reference arm and the Faraday rotating mirror II 5, the reflected measuring light and the reference light interfere at the 1x2 coupler 3 and generate interference light signals, and the interference light signals enter the signal processing module after passing through the circulator 2, the photoelectric detector 6 and the data acquisition card 7 in sequence, and external vibration signals are demodulated by the signal processing module.
Details are described below in conjunction with fig. 1-2.
Example 1
A schematic flow chart of the algorithm of the present invention is shown in fig. 1. Wherein I is an interference signal, LPF is a low-pass filter, SQUARE is SQUARE, SQRT & ABS is SQUARE root, absolute value is obtained, DIFF is partial derivative, HPF is high-pass filter, I out is a demodulation result demodulated by the algorithm,In the form of an adder which is provided with a first input,In the form of a subtracter,In the form of a multiplier which is a set of multipliers,Is a divider, and ∈ is an integrator, the algorithm based on the above. The Laser in fig. 2 is a Laser. The ordinate Amplitude in fig. 3 represents the Amplitude. The ordinate Amplitude Power Spectrum in fig. 4 represents the amplitude frequency spectrum.
The interferometer is an unbalanced interferometer, and the current expression of an interference light signal output by the unbalanced interferometer is as follows:
Wherein A is the direct current of the interference signal; b is the light intensity, where b=ka, (0<k < 1), κ is the fringe visibility; c is modulation depth, which is the amplitude of the phase carrier introduced by the interferometer; omega 0 is the frequency of the modulated signal; The phase delay, phi (t), is the phase to be measured.
The current expansion of the above current expression I is performed by the bessel function, and the current expansion is obtained as follows:
wherein J n (C) is an n-th order Bessel function. The Bessel function is:
Wherein J n (z) is an n-th order Bessel function.
Multiplying the current expansion I by sinw 0t、cosw0 t and sin2w 0t、cos2w0 t respectively, and filtering all w 0 and frequency multiplication items thereof respectively through low-pass filtering after integrating and reducing the difference formula to obtain the three-dimensional current:
and the sum and difference formula is:
cosαcosβ＝[cos(α+β)+cos(α-β)]/2
cosαsinβ＝[sin(α+β)-sin(α-β)]/2)
wherein alpha and beta are angles, and have no physical meaning.
The square and addition of the above X 11 and X 12、Y11 and Y 12, respectively, yields:
And then the above-mentioned materials are added AndAnd respectively taking absolute values after square opening to obtain:
Dividing the X 12、Y12 with X 21、Y21 to obtain
And then the saidRespectively corresponding to and dividing the X 12、Y12 in the step 3 to obtain
And performing low-pass filtering on the current expansion to filter all w 0 and frequency multiplication items thereof, obtaining Z=BJ 0 (C) cos phi (t), and obtaining Y 'and Z' by respectively carrying out bias conduction on the Y and the Z as follows:
Y′＝BJ2(C)sinφ(t)φ′(t)
Z′＝-BJ0(C)sinφ(t)φ′(t)
Dividing the above Y 'and Z' by the above X to obtain
Then willAndSubtracting to obtain
Then the Bessel recursion formula is used for the methodSimplifying to obtain
And the Bessel recurrence formula is
Wherein J n (x) is an n-th order Bessel function.
Finally, after sequentially integrating and high-pass filtering phi' (t), the obtained demodulation result I out is:
Wherein C is modulation depth, and is a fixed value when the system collects, transmits and demodulates external vibration signals Is constant and the demodulation result I out does not contain the light intensity B and the phase delaySignal distortion caused by light source power fluctuation and phase delay can be effectively restrained.
The invention utilizes the quadrature signal to extract the phase delay termCancellation of phase delay terms in quadrature signals by a dividerSignal distortion caused by phase delay can be effectively restrained; the influence of light source power fluctuation, modulation depth and phase delay on the signal to be detected is eliminated through a Bessel recursion formula, and the demodulation precision and stability are higher; the algorithm does not introduce arctangent operation per se, and the demodulation result does not introduce nonlinear distortion; in addition, the demodulation result of the present invention does not contain the light intensity B and the phase delayThe method can effectively inhibit signal distortion caused by light source power fluctuation and phase delay, and has higher stability than the PGC-DCM algorithm and the PGC-Arctan algorithm.
Example 2
Fig. 2 shows a phase demodulation device according to the present invention. The device comprises a laser 1, a circulator 2, a 1x2 coupler 3, a sensing arm, a reference arm, a first Faraday rotating mirror 4, a second Faraday rotating mirror 5, a photoelectric detector 6, a data acquisition card 7 and a signal processing module; the arm lengths of the sensing arm and the reference arm are different. The laser generated by the laser 1 sequentially passes through the circulator 2 and the 1x2 coupler 3 and is split into measuring light and reference light, the measuring light sequentially passes through the sensing arm and the Faraday rotating mirror I4 and is output to the 1x2 coupler 3 along the sensing arm, the reference light sequentially passes through the reference arm and the Faraday rotating mirror II 5 and is output to the 1x2 coupler 3 along the reference arm, the reflected measuring light and the reference light interfere at the 1x2 coupler 3 and generate interference light signals, and the interference light signals sequentially pass through the circulator 2, the photoelectric detector 6 and the data acquisition card 7 and then enter the signal processing module, and the signal processing module demodulates the external vibration signals according to the phase demodulation algorithm of the invention.
In the embodiment, a comparison experiment of the algorithm and demodulation results of the PGC-DCM algorithm and the PGC-Arctan algorithm is set. The same unbalanced interferometer is adopted in the embodiment, and for interference light signals collected by the unbalanced interferometer, different algorithms and parameters set by the unbalanced interferometer are as follows: setting sampling frequency 200kHz, carrier frequency 20kHz, signal amplitude to be measured 1rad, frequency 600Hz, light source power 1mW, carrier phase delay 0 degree, and modulation depth 1.5rad. At this time, a comparison chart of the PGC-DCM algorithm, the PGC-Arctan algorithm and the demodulation time domain signal of the Improved algorithm of the invention is shown in figure 3, the demodulation time domain signal of the three demodulation algorithms can be obtained, and compared with the demodulation results of the PGC-DCM algorithm and the PGC-Arctan algorithm, the waveform is not distorted; the noise and the interference waveform burrs of the time domain signal are less, the waveform overlap is lower, and the waveform is smooth and clear. Compared with the PGC-DCM algorithm, the signal demodulated by the algorithm can well maintain the characteristics of the original signal to be detected, and has the advantages of no distortion, small distortion and good algorithm performance.
By adopting the same parameter setting, a comparison chart of PGC-DCM algorithm, PGC-Arctan algorithm and the Improved algorithm PGC-Improved demodulation frequency domain signal of the invention is shown in figure 4, and compared with the PGC-DCM demodulation result, the PGC-Improved demodulation result has no side peak, the algorithm can accurately separate and identify the frequency component of the signal to be detected, and the algorithm has stronger resolution capability on the frequency component of the signal to be detected and higher accuracy of the demodulation result; meanwhile, compared with the PGC-Arctan demodulation result, the algorithm of the invention can not generate frequency multiplication signals and has higher signal stability.
According to the invention, a phase delay term is extracted through the orthogonal signal, then the phase delay term in the orthogonal signal is eliminated by using a divider, and the influence of light source power fluctuation, phase delay and modulation depth on a signal to be detected is eliminated by combining a Bessel recursion formula; the demodulation algorithm does not introduce arctangent operation, and the demodulation result does not introduce nonlinear distortion; the demodulation result of the algorithm of the invention does not contain the light intensity B and the phase delayThe method can effectively inhibit signal distortion caused by light source power fluctuation and phase delay, is more stable than a PGC-DCM algorithm and a PGC-Arctan algorithm, and has higher demodulation accuracy.
Although the specification has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims. Furthermore, the particular embodiments described are not intended to limit the scope of the invention, as one of ordinary skill in the art will readily appreciate from the disclosure that processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, may perform substantially the same function or achieve substantially the same result as the embodiments of the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
Claims (6)
1. An improved phase demodulation algorithm, characterized by: the method comprises the following steps:
Step 1: the current expression of the interference light signal output by the interferometer is
Wherein A is the direct current of the interference signal; b is the light intensity, where b=ka, (0 < k < 1), k is the interference fringe visibility; c is modulation depth, which is the amplitude of the phase carrier introduced by the interferometer; omega 0 is the frequency of the modulated signal; the phase delay is phi (t) and the phase to be detected is phi (t);
step 2: the current expression of step 1 is expanded by Bessel function, and the current expansion is obtained as follows
Wherein J n (C) is an n-order Bessel function;
Step 3, multiplying the current expansion of step 2 by sinw 0t、cosw0 t and sin2w 0t、cos2w0 t respectively, integrating and reducing the difference formula, and respectively filtering out all w 0 and frequency multiplication terms thereof by low-pass filtering to obtain
Step 4: squaring and adding X 11, X 12、Y11 and Y 12 in step 3
Step 5: for step 4AndAnd respectively taking absolute values after square opening to obtain:
Step 6: dividing X 12、Y12 in step 3 by X 21、Y21 in step 5 respectively
Step 7: step 6Respectively corresponding to and dividing the X 12、Y12 in the step 3 to obtain
Step 8: low-pass filtering the current expansion in the step 2 to remove all w 0 and its frequency multiplication term to obtain
Z＝BJ0(C)cosφ(t)
Wherein phi (t) is the phase to be measured;
step 9: and (3) respectively carrying out bias guide on Y in the step 7 and Z in the step 8 to obtain:
Y′＝BJ2(C)sinφ(t)φ′(t)
Z′＝-BJ0(C)sinφ(t)φ′(t)
Step 10: dividing Y 'and Z' in step 9 by X in step 7, respectively, to obtain
Step 11: step 10AndSubtracting to obtain
Step 12: the step 11 is performed by Bessel recursion formulaSimplifying, wherein the Bessel recurrence formula is as follows:
Wherein J n (x) is the n-order Bessel function, then The method can be simplified as follows:
step 13: and (3) sequentially integrating and high-pass filtering the phi' (t) in the step 12, and obtaining a demodulation result I out as follows:
wherein C is a constant value, then Is constant and the demodulation result Iout does not contain light intensity B and phase delaySignal distortion caused by light source power fluctuation and phase delay can be effectively restrained.
2. An improved phase demodulation algorithm as claimed in claim 1 wherein: the Bessel function in the step 2 is that
Wherein J n (z) is an n-th order Bessel function.
3. An improved phase demodulation algorithm as claimed in claim 1 wherein: the integral sum and difference formula in the step 3 is as follows
cosαcosβ＝[cos(α+β)+cos(α-β)]/2
cosαsinβ＝[sin(α+β)-sin(α-β)]/2)
Wherein alpha and beta are angles, and have no physical meaning.
4. A phase demodulation apparatus of an improved phase demodulation algorithm as claimed in any one of claims 1 to 3, characterised in that: the device comprises a laser, a circulator, a 1x2 coupler, an unbalanced interferometer, a photoelectric detector, a data acquisition card and a signal processing module; the laser generated by the laser sequentially passes through the circulator and the 1x2 coupler and then enters the unbalanced interferometer, the unbalanced interferometer detects an external vibration signal and then returns to the 1x2 coupler, an interference light signal is generated in the 1x2 coupler, the interference signal is collected by the data acquisition card after passing through the circulator and the photoelectric detector and is output to the data processing module, and the data processing module demodulates the external vibration signal.
5. The phase demodulating apparatus according to claim 4, wherein: the unbalanced interferometer comprises a sensing arm, a reference arm, a Faraday rotating mirror I and a Faraday rotating mirror II; the arm lengths of the sensing arm and the reference arm are different.
6. The phase demodulating apparatus according to claim 5, wherein: the laser generated by the laser device is split into measuring light and reference light after passing through the circulator and the 1x2 coupler in sequence, the measuring light is output to the 1x2 coupler through the sensing arm and the Faraday rotating mirror I reflection trailing edge sensing arm in sequence, the reference light is output to the 1x2 coupler through the reference arm and the Faraday rotating mirror II reflection trailing edge reference arm in sequence, the reflected measuring light and the reference light interfere at the 1x2 coupler and generate interference light signals, and the interference light signals enter the signal processing module after passing through the circulator, the photoelectric detector and the data acquisition card in sequence, and external vibration signals are demodulated by the signal processing module.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410996011.3A CN118551137B (en) | 2024-07-24 | Improved phase demodulation algorithm and device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410996011.3A CN118551137B (en) | 2024-07-24 | Improved phase demodulation algorithm and device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN118551137A CN118551137A (en) | 2024-08-27 |
| CN118551137B true CN118551137B (en) | 2024-11-15 |
Family
ID=
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110411486A (en) * | 2019-07-26 | 2019-11-05 | 浙江理工大学 | The PGC-DCDM demodulation method insensitive to phase delay and modulation depth |
| CN115022140A (en) * | 2022-05-30 | 2022-09-06 | 西安石油大学 | Method and apparatus for eliminating phase delay of phase demodulation carrier and compensating modulation depth |
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110411486A (en) * | 2019-07-26 | 2019-11-05 | 浙江理工大学 | The PGC-DCDM demodulation method insensitive to phase delay and modulation depth |
| CN115022140A (en) * | 2022-05-30 | 2022-09-06 | 西安石油大学 | Method and apparatus for eliminating phase delay of phase demodulation carrier and compensating modulation depth |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN112097813B (en) | 3X 3 coupler photoelectric detection method and device based on optical frequency modulation | |
| CN110411486B (en) | PGC-DCDM demodulation method insensitive to phase delay and modulation depth | |
| CN110864714B (en) | Distributed sensing system based on Michelson-Sagnac fiber optic interferometer | |
| CN108007550B (en) | Improved PGC modulation-demodulation detection method | |
| Hou et al. | Large dynamic range and high sensitivity PGC demodulation technique for tri-component fiber optic seismometer | |
| CN105067017A (en) | Modified phase generated carrier (PGC) demodulation method | |
| CN105486225A (en) | Phase demodulation device and demodulation method capable of suppressing light-intensity fluctuation noise | |
| CN105486331B (en) | One kind has high-precision optical signalling phase demodulating system and demodulation method | |
| CN113091782B (en) | PGC-based phase-sensitive optical time domain reflection system and phase demodulation method | |
| CN109141490A (en) | A kind of fibre-optical sensing device and demodulation method of disturbance waveform and position measurement simultaneously | |
| CN104330104A (en) | Measuring device for interferential sensor arm length difference | |
| CN113852416A (en) | Phase demodulation method and device with fading noise identification and elimination function | |
| CN101799610B (en) | Orthogonal demodulation device for heterodyne phase interference fiber sensor | |
| CN113124994B (en) | Distributed vibration sensing demodulation method based on weak signal-to-noise ratio signal | |
| CN102435186A (en) | Digital signal processing method and device of optic fiber gyroscope as well as optic fiber gyroscope | |
| CN111811549B (en) | Demodulation method and positioning device of asymmetric double Mach-Zehnder sensing system | |
| CN118551137B (en) | Improved phase demodulation algorithm and device | |
| CN111609791B (en) | Method for extracting and compensating modulation depth in PGC phase demodulation method | |
| CN112880711B (en) | Distributed optical fiber sensing method and system based on double pulse modulation | |
| CN106247930A (en) | The residual compensation method of phase carrier formula laser interferometer closed loop demodulating algorithm | |
| CN111366179A (en) | Self-differential phase division phase generation carrier demodulation method | |
| CN118551137A (en) | Improved phase demodulation algorithm and device | |
| CN111157098B (en) | Demodulation device for simultaneously obtaining amplitude and phase of vibration signal | |
| CN111337061A (en) | Phase generation carrier demodulation method for eliminating disturbance | |
| CN104266739B (en) | A kind of target vibration measurement system and method, demodulating equipment and demodulation method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant |