CN109855719B - High-stability interference type optical fiber hydrophone signal demodulation method - Google Patents
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Abstract
The invention discloses a signal demodulation method for an interference type optical fiber hydrophone, which comprises the following steps: step S100: the laser applies sinusoidal frequency modulation, the laser inputs the output light wave into the unbalanced interference type optical fiber hydrophone, the optical fiber hydrophone applies a large-amplitude test acoustic signal, the optical fiber hydrophone inputs the output test interference signal into the signal demodulation system, and the test interference signal is processed to obtain a demodulation system parameter estimation value; step S200: the optical fiber hydrophone is placed in a measuring environment to measure the acoustic signal to be measured, outputs an actual interference signal to be input into a signal demodulation system, processes the actual interference signal and corrects the actual interference signal through the parameter estimation value of the demodulation system to obtain the acoustic signal to be measured. The high-stability signal detection of the interference type optical fiber hydrophone is realized.
Description
Technical Field
The invention relates to the technical field of signal demodulation of an optical fiber hydrophone, in particular to a high-stability interference type optical fiber hydrophone signal demodulation method.
Background
The optical fiber hydrophone is a novel underwater acoustic sensor, has the characteristics of high sensitivity, flexible structure, easiness in multiplexing to form a large-scale array and the like, and has important application in the fields of underwater target detection, seismic wave detection and the like. In various types of optical fiber hydrophones, an interference type optical fiber sensor is based on an optical fiber interferometer structure, and a detected signal is loaded in a sensor output signal in a phase mode through a high-sensitivity coherent detection technology, so that the optical fiber hydrophone has the excellent characteristics of high sensitivity, low noise and the like. However, because the interference type optical fiber hydrophone has a random phase fading phenomenon, the interference type optical fiber hydrophone needs to be modulated and demodulated to realize stable signal detection, and therefore, the signal demodulation method becomes a key technology in the application of the interference type optical fiber hydrophone.
Phase modulation carrier (PGC) modulation and demodulation technology, which is a passive homodyne demodulation technology, is one of the most commonly used demodulation technologies for interferometric fiber optic hydrophones. The internal modulation PGC mode applies sinusoidal frequency modulation to the laser, and converts the frequency modulation into phase modulation by adopting an unbalanced interferometer, thereby realizing phase modulation carrier. The method can realize full optical fiber of sensing elements and is suitable for large-scale optical fiber hydrophone array application.
However, in the conventional optical fiber hydrophone PGC demodulation scheme, non-ideal factors such as modulation depth stability and laser additional intensity modulation exist in an actual system, and these factors will cause PGC demodulation errors, so that the demodulation signal stability is reduced, and meanwhile, larger signal harmonic distortion is caused, and the performance of the demodulation system is seriously affected.
With the wide and deep application of the interference type optical fiber hydrophone, higher and higher requirements are provided for the signal detection stability of the optical fiber hydrophone. For example, in vector fiber hydrophone applications, estimation of a target azimuth can be achieved by comparing signal amplitudes of orthogonal hydrophone channels, and instability of demodulated signals directly causes target azimuth estimation errors; in the application of a large-scale optical fiber hydrophone array, the amplitude consistency among multichannel optical fiber hydrophone elements is influenced by the instability of signals, so that the gain level of the array is directly reduced, and the application performance of the array is seriously influenced.
Disclosure of Invention
The technical problem to be solved by the present invention is to overcome the above defects in the prior art, and provide a high-stability signal demodulation method for an interference optical fiber hydrophone, so as to realize high-stability signal detection of the interference optical fiber hydrophone.
The invention provides a signal demodulation method of an interference type optical fiber hydrophone, which comprises the following steps:
step S100: the laser applies sinusoidal frequency modulation, the laser inputs the output light wave into the unbalanced interference type optical fiber hydrophone, the optical fiber hydrophone applies a large-amplitude test acoustic signal, the optical fiber hydrophone inputs the output test interference signal into the signal demodulation system, and the test interference signal is processed to obtain a demodulation system parameter estimation value;
step S200: placing the optical fiber hydrophone in a measuring environment to measure a measured acoustic signal, outputting an actual interference signal by the optical fiber hydrophone, inputting the actual interference signal into a signal demodulation system, processing the actual interference signal, and correcting the parameter estimation value of the demodulation system to obtain the measured acoustic signal;
the step S100 is specifically:
step S101: the laser applies sinusoidal frequency modulation, the laser inputs the output light wave into the unbalanced interference type optical fiber hydrophone, the optical fiber hydrophone applies a large-amplitude test acoustic signal, and the optical fiber hydrophone inputs the output test interference signal into the signal demodulation system; test interference signal I output by optical fiber hydrophonec(t) is:
wherein, I0M is the intensity of the laser, ωcIs the frequency of the phase carrier circle and,
for intensity modulation initial phase, v for interference signal visibility, C for phase carrier modulation amplitude,
is a test acoustic signal;
step S102: the test interference signal is multiplied by the carrier frequency second and third frequency multiplication reference signals respectively and is subjected to low-pass filtering to obtain second and third frequency multiplication detection signals of the test interference signal; two, three frequency multiplication detection signal S for testing interference signalc2(t) and Sc3(t) are respectively:
wherein, X2(t) carrier frequency-doubled reference signal, X3(t) carrier frequency tripled frequency reference signal, hLPF(t) is the low pass filter response, a2And a3Is an error parameter;
step S103: constructing an elliptic curve by using second and third frequency multiplication detection signals of the test interference signal; the elliptic curve is:
wherein,
Sc2(t) and Sc3(t) is denoted by Sc2And Sc3；
Step S104: carrying out ellipse parameter fitting on the constructed elliptic curve to obtain a fitting value of each elliptic curve parameter;
step S105: and obtaining the estimated value of the demodulation system parameter according to the fitting value of the elliptic curve parameter.
Preferably, the step S200 specifically includes:
step S201: placing the optical fiber hydrophone in a measuring environment to measure a measured acoustic signal, and outputting an actual interference signal by the optical fiber hydrophone to input the actual interference signal into a signal demodulation system;
step S202: multiplying the actual interference signal by a carrier frequency second and third frequency multiplication reference signal respectively and obtaining a second and third frequency multiplication detection signal of the actual interference signal through low-pass filtering;
step S203: correcting second and third frequency multiplication detection signals of the actual interference signal by using the demodulation system parameter estimation value to obtain an orthogonal demodulation signal;
step S204: and performing orthogonal signal demodulation calculation by using the orthogonal demodulation signal to obtain the measured acoustic signal.
Preferably, in step S105, specifically: obtaining demodulation system parameters B according to fitting values of elliptic curve parameters a, B, c, d, e and f2,B3And δ estimate:
preferably, in step S203, specifically: using demodulation system parameter estimate B2,B3Second and third frequency-multiplication detection signal S of delta pair actual interference signalt2And St3Correction is performed to obtain quadrature demodulation signals SR and CR:
wherein,
Preferably, in step S204, specifically: orthogonal signal demodulation calculation is carried out by utilizing orthogonal demodulation signals SR and CR to obtain the tested acoustic signal
The method is divided into two steps, step S100 realizes the accurate acquisition of demodulation system parameters, and step S100 completes the demodulation calculation of high-stability signals. The method realizes stable signal demodulation under the condition of accurately measuring and calculating the parameters of the demodulation system, and eliminates the influence of phase carrier modulation amplitude error and additional intensity modulation effect. The performance of the demodulation system can be effectively improved without increasing the complexity and the cost of the demodulation system without increasing the overhead of extra hardware, and the high-stability signal detection of the interference type optical fiber hydrophone is realized.
Drawings
Fig. 1 is a flow chart of a signal demodulation method of a high-stability interferometric fiber optic hydrophone provided in a first embodiment;
fig. 2 is a flowchart of a signal demodulation method for a high-stability interferometric fiber optic hydrophone according to a second embodiment;
FIG. 3 is a system structure diagram for implementing a signal demodulation method of an interference type fiber optic hydrophone according to the present invention;
fig. 4 is a graph showing the results of a conventional PGC demodulation method and the experimental results of a high-stability interferometric fiber optic hydrophone signal demodulation method provided by the second embodiment.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings.
Referring to fig. 1, fig. 1 is a flowchart of a method for demodulating a high-stability interferometric fiber optic hydrophone signal according to a first embodiment.
The invention provides a signal demodulation method of an interference type optical fiber hydrophone, which comprises the following steps:
step S100: the laser applies sinusoidal frequency modulation, the laser inputs the output light wave into the unbalanced interference type optical fiber hydrophone, the optical fiber hydrophone applies a large-amplitude test acoustic signal, the optical fiber hydrophone inputs the output test interference signal into the signal demodulation system, and the test interference signal is processed to obtain a demodulation system parameter estimation value;
step S200: the optical fiber hydrophone is placed in a measuring environment to measure the acoustic signal to be measured, outputs an actual interference signal to be input into a signal demodulation system, processes the actual interference signal and corrects the actual interference signal through the parameter estimation value of the demodulation system to obtain the acoustic signal to be measured.
The embodiment provides a high-stability interference type optical fiber hydrophone signal demodulation method which is divided into two steps, wherein the step S100 is used for accurately obtaining demodulation system parameters, and the step S200 is used for completing high-stability signal demodulation calculation. And the stable demodulation of signals is realized under the condition of accurately measuring and calculating system parameters, and the influence of phase carrier modulation amplitude error and additional intensity modulation effect is eliminated. The performance of the demodulation system can be effectively improved without increasing the complexity and the cost of the demodulation system without increasing the overhead of extra hardware, and the high-stability signal detection of the interference type optical fiber hydrophone is realized.
Referring to fig. 2, fig. 2 is a flowchart of a method for demodulating a high-stability interferometric fiber optic hydrophone signal according to a second embodiment.
In the PGC modem method, ideally, the output interference light intensity i (t) of the fiber optic hydrophone can be expressed as:
wherein, I0Is the light intensity direct current quantity, v is the interference signal visibility, C is the phase carrier modulation amplitude, omegacIs the frequency of the phase carrier circle and,
sensing phase signals for fiber optic hydrophones
And initial phase of interferometer
And (4) summing.
Considering the existence of the additional intensity effect in the phase carrier modulation, the output interference light intensity of the fiber optic hydrophone can be expressed as follows:
where m is the intensity modulation amplitude of the laser,
the initial phase is intensity modulated.
Using the trigonometric function bezier expansion formula, equation (2) can be expanded as:
where k is the order of the expansion of the Bessel trigonometric function.
The carrier frequency one, two and three frequency multiplication reference signals are as follows:
interference signals I (t) shown in formula (3) are respectively mixed with carrier frequency first, second and third frequency multiplication reference signals X1(t)、X2(t) and X3(t) multiplying and low-pass filtering to obtain the first, second and third frequency-multiplication detection signal S1(t)、S2(t) and S3(t) the following:
wherein h isLPF(t) is the low pass filter response.
To simplify the representation of equations (5), (6) and (7), error parameters are defined:
the first, second and third frequency multiplication detection signal S1(t)、S2(t) and S3(t) may be represented by S1、S2And S3：
In the equations (9), (10) and (11), the first term on the right of the equation is the amplitude of each harmonic in an ideal case, the second term and the third term on the right of the equation are error terms introduced by the additional intensity modulation, and the magnitude of the error terms is related to the amplitude of the carrier modulation, the additional intensity modulation parameter and the initial phase of the interferometer.
In a conventional PGC demodulation method, a quadrature signal is constructed using a first and second frequency-doubled detection signal, and quadrature phase solution is performed by using an inverse-quadrature method or a differential cross multiplication method.
Taking the anti-tangential method as an example, in an ideal situation, no additional intensity modulation error exists, and the error parameter b1,a1,a2,a3Both are zero, and as can be seen from equations (9) and (10), the quadrature detection signal is:
calculated as follows:
performing arc tangent calculation on the formula (14), and obtaining the measured phase information as follows:
however, in practical modulation systems, there are many factors that cause phase demodulation errors, resulting in unstable signal detection, and the following two major factors are:
(1) additional intensity modulation effect
As can be seen from equations (9) and (10), the quadrature phase detection signal has an error term due to the additional intensity modulation effect in the phase carrier process, and if the calculation is performed according to equation (15), the calculation result is:
it can be seen that the result is calculated due to the presence of the error term
Actual phase of ratio
A large deviation will occur and this deviation is related to the initial phase of the interferometer. In practical application of the fiber optic hydrophone system, the initial phase of the hydrophone can slowly drift along with the change of the environment, so that the signal detection is unstable, and the performance of a demodulation system is seriously influenced.
(2) Phase carrier modulation amplitude error
When the formula (15) is used for calculation, J needs to be introduced according to the amplitude C value of the phase carrier of the system1(C) And J2(C) Will generallyC value is set to 2.63rad, at which time J1(C)＝J2(C) The influence of the C value can be eliminated. However, in the practical fiber-optic hydrophone system, especially in the application of the multi-channel fiber-optic hydrophone array, due to the inconsistency of the arm difference length of the unbalanced interferometer of each hydrophone element, the phase carrier amplitudes of different fiber-optic hydrophones will be different and deviate from 2.63rad, and at this time, the modulation amplitude of each hydrophone element needs to be measured and calculated, and then J is calculated2(C)/J1(C) The calculation was performed in place of equation (15).
The general modulation amplitude measuring and calculating method is to calculate J by using each frequency multiplication detection signal1(C)/J3(C) Or J2(C)/J4(C) And estimating the C value by a table look-up method and other methods. However, when the additional intensity modulation effect exists, each frequency-doubled detection signal has an error, which also causes an error in calculating the C value, and the error in calculating the C value also directly causes the fluctuation of the signal detection amplitude.
The interference type optical fiber hydrophone signal demodulation method provided by the second embodiment of the invention comprises the following steps:
step S101: the laser applies sine frequency modulation, the laser inputs the output light wave into the unbalanced interference type optical fiber hydrophone, the optical fiber hydrophone applies large-amplitude test acoustic signal, and the optical fiber hydrophone outputs test interference signal Ic(t) input signal demodulation system.
Laser applied frequency of omegacAfter the sine frequency modulation, the output light wave is input into the unbalanced interference type optical fiber hydrophone, and the light wave frequency modulation is converted into interferometer phase modulation, so that phase modulation carrier waves are realized. The frequency modulation of the laser inevitably has additional intensity modulation effect, when the output interference signal I of the optical fiber hydrophonec(t) can be expressed as:
the fiber optic hydrophone applies a large amplitude test acoustic signal, in this case a sinusoidal test signal, when
Can be expressed as:
wherein, ω issFor the applied test acoustic signal circular frequency, D for the test acoustic signal amplitude,
the initial phase of the interferometer. For measuring and calculating system parameters, acoustic signals are tested
The amplitude should be greater than pi and in order not to cause signal distortion, the test acoustic signal amplitude D should be within the system dynamic range.
Step S102: testing interference signals Ic(t) is respectively related to carrier frequency second and third frequency multiplication reference signal X2(t) and X3(t) multiplying and low-pass filtering to obtain second and third frequency-multiplication detection signal S of test interference signalc2(t) and Sc3(t)。
Mixing X2(t) and X3(t) separately from the test interference signal Ic(t) multiplying, filtering carrier information by a low-pass filter to obtain a second and third frequency multiplication detection signal S of the test interference signalc2(t) and Sc3(t) the following:
step S103: second and third frequency detection signal S using test interference signalc2(t) and Sc3(t) constructing an elliptic curve;
according to formulae (19) and (20), Sc2(t) and Sc3(t) may be represented by Sc2And Sc3：
Wherein, the parameter B2,B3,θ2,θ3,
δ is represented by the following formula:
thus, using Sc2And Sc3The values as (x, y) coordinates may be constructed as an elliptic curve as follows:
compared with the conventional PGC demodulation method which adopts the first frequency detection signal and the second frequency detection signal, the method adopts the second frequency detection signal and the third frequency detection signal to construct an elliptic curve and carry out quadrature phase demodulation. As can be seen from the expressions (9), (10) and (11), compared with the first frequency doubling detection signal, the second and third frequency doubling detection signals do not contain a direct current error term related to additional intensity modulation, the constructed elliptic curve parameters are reduced, the influence of system parameter measurement errors can be reduced to a certain extent, and the signal demodulation performance is improved.
Step S104: fitting the ellipse parameters of the constructed ellipse curve to obtain an ellipse equation ax2+bxy+cy2+ dx + ey + f is 0 for each of the values of a, b, c, d, e, f;
as shown in the formula (24), since the phase difference between the x and y signals is close to 90 degrees, if x and y are drawn on two coordinate axes perpendicular to each other, the trajectory can form a stable ellipse, and the ellipse equation can be expressed by an implicit equation:
L(a·u)＝ax2+bxy+cy2+dx+ey+f＝0 (25)
wherein a ═ a b c d e f]Is an elliptic coefficient vector, u ═ x2 xy y2 x y 1]. There are many methods for realizing the fitting of the elliptic curve, and a voting clustering method, an optimization method and the like can be adopted, so that fitting values of the elliptic parameters a, b, c, d, e and f are obtained.
Step S105: obtaining demodulation system parameters B according to fitting values of elliptic curve parameters a, B, c, d, e and f2,B3And delta estimate.
The expressions (24) and (25) are both expressions of elliptic curves, and the demodulation parameter B in the expression (24) can be obtained by performing expansion and elimination treatment on the expression (24) and comparing the formula (24) with the expression (25)2,B3δ and the elliptic curve parameters a, b, c, d, e, f in equation (25) are as follows:
according to the above formula, the demodulation system parameter B can be calculated by using the elliptic curve parameters a, B, c, d, e and f obtained in step S1042,B3And delta estimate.
Step S201: placing fiber optic hydrophone in measurement environment to measure acoustic signal to be measured
The optical fiber hydrophone outputs an actual interference signal and inputs the actual interference signal into a signal demodulation system;
step S202: the actual interference signal is multiplied by the carrier frequency second and third frequency multiplication reference signals respectively and is subjected to low-pass filtering to obtain second and third frequency multiplication detection signals S of the actual interference signalt2And St3；
Step S203: using demodulation system parameter estimate B2,B3Second and third frequency-multiplication detection signal S of delta pair actual interference signalt2And St3Correcting to obtain orthogonal demodulation signals SR and CR;
according to formula (24), St2And St3Can be expressed as follows:
wherein,
to St2And St3The correction is made as follows:
then the quadrature demodulation term can be obtained as follows:
step S204: orthogonal signal demodulation calculation is carried out by utilizing orthogonal demodulation signals SR and CR to obtain the tested acoustic signal
Performing arc tangent quadrature demodulation calculation by using SR and CR, wherein the calculation formula is as follows:
the above formula resolves to result
According to the formula (23), the phase position of the measured phase position is compared with the actual phase position
Compared with only the difference of theta2And theta2Value and C, m and
the phase-locked loop is independent of the initial phase of the interferometer, is a relatively stable small quantity, and does not influence the stability of the signal amplitude.
Compared with the conventional PGC demodulation method, the result solved by the method does not contain the light intensity I any more0Degree of interference v, phase modulation amplitude C, additional intensity modulation amplitude m and phase
The parameters are equal and are irrelevant to the initial phase of the interferometer, so that the influence of the intensity modulation effect and various parameter errors can be effectively eliminated, the signal demodulation stability is improved, and high-stability signal demodulation output is obtained.
Referring to fig. 3 and 4, fig. 3 is a system structure diagram for implementing a method for demodulating an interference optical fiber hydrophone signal according to the present invention, and fig. 4 is a diagram illustrating a result of a conventional PGC demodulation method and an experimental result of a method for demodulating a high-stability interference optical fiber hydrophone signal according to a second embodiment.
In order to verify the feasibility of the method, a practical experimental system is shown in fig. 3, and comprises a laser 1, an unbalanced fiber michelson interferometer 2, a photoelectric converter 3, an AD acquisition card 4 and a signal generator 5. The laser 1 emits light waves after being modulated by sine frequency and inputs the light waves into the unbalanced fiber interferometer 2, the unbalanced fiber interferometer 2 converts the frequency modulation of the laser 1 into phase modulation to realize phase carrier, the returned interference signals are converted into electric signals by the photoelectric converter 3, and after the digital sampling is finished by the AD acquisition card 4, the signal demodulation calculation is carried out.
The optical fiber interferometer in the experimental system adopts an unbalanced Michelson interferometer structure to simulate the response of the optical fiber hydrophone to the measured acoustic signal. Two arms of the interferometer are respectively provided with two PZT phase modulators, a signal generator respectively sends out 200Hz and 10mHz sinusoidal signals to drive the phase modulators PZT1 and PZT2, the 200Hz signal simulates an acoustic signal of the optical fiber hydrophone sensing 200Hz, and the 10mHz signal simulates slow drifting of the initial phase difference of the optical fiber interferometer along with environmental changes. Firstly, the amplitude of a 200Hz sine driving signal is controlled to generate phase modulation with larger amplitude (larger than pi), then a complete elliptic curve can be obtained, and demodulation system parameters are obtained through elliptic parameter fitting. Then reducing the amplitude of the 200Hz sinusoidal driving signal to enable the phase modulator PZT1 to generate 1rad sinusoidal phase modulation, simulating the sensing acoustic signal of the optical fiber hydrophone, respectively adopting a conventional PGC demodulation method and the high-stability demodulation method of the invention to perform signal demodulation calculation, and comparing the signal stability of the two methods.
The results of the experiment are shown in FIG. 4. FIG. 4(a) shows the variation of 200Hz signal amplitude with time obtained by conventional PGC demodulation method, where the unit of the upper graph signal amplitude is rad, and the unit of the lower graph signal amplitude is dB (ref: 1rad), it can be seen that the initial phase of the fiber interferometer generates periodic slow drift due to the low frequency phase modulation simulation applied by PZT2, the signal amplitude obtained by resolving also generates periodic fluctuation, and for 1rad signal, the signal amplitude fluctuation (the difference between the maximum value and the minimum value of the signal amplitude) reaches 20.3% and 1.76 dB. Fig. 4(b) is a calculation result by using the high-stability demodulation method of the present application, and it can be seen that the signal amplitude fluctuation is significantly reduced compared to fig. 4(a), and the validity of the present application is verified for 1rad signal amplitude fluctuations of 1.89% and 0.16 dB.
The signal demodulation method for the high-stability interference type optical fiber hydrophone provided by the invention is described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the core concepts of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (5)
1. A high-stability interference type optical fiber hydrophone signal demodulation method is characterized by comprising the following steps:
step S100: the laser applies sinusoidal frequency modulation, the laser inputs the output light wave into the unbalanced interference type optical fiber hydrophone, the optical fiber hydrophone applies a large-amplitude test acoustic signal, the optical fiber hydrophone inputs the output test interference signal into the signal demodulation system, and the test interference signal is processed to obtain a demodulation system parameter estimation value;
step S200: placing the optical fiber hydrophone in a measuring environment to measure a measured acoustic signal, outputting an actual interference signal by the optical fiber hydrophone, inputting the actual interference signal into a signal demodulation system, processing the actual interference signal, and correcting the parameter estimation value of the demodulation system to obtain the measured acoustic signal;
the step S100 is specifically:
step S101: the laser applies sinusoidal frequency modulation, the laser inputs the output light wave into the unbalanced interference type optical fiber hydrophone, the optical fiber hydrophone applies a large-amplitude test acoustic signal, and the optical fiber hydrophone inputs the output test interference signal into the signal demodulation system; test interference signal I output by optical fiber hydrophonec(t) is:
wherein, I0M is the intensity of the laser, ωcIs the frequency of the phase carrier circle and,
for intensity modulation initial phase, v for interference signal visibility, C for phase carrier modulation amplitude,
is a test acoustic signal;
step S102: the test interference signal is multiplied by the carrier frequency second and third frequency multiplication reference signals respectively and is subjected to low-pass filtering to obtain second and third frequency multiplication detection signals of the test interference signal; two, three frequency multiplication detection signal S for testing interference signalc2(t) and Sc3(t) are respectively:
wherein, X2(t) carrier frequency-doubled reference signal, X3(t) carrier frequency tripled frequency reference signal, hLPF(t) is the low pass filter response, a2And a3Is an error parameter;
step S103: constructing an elliptic curve by using second and third frequency multiplication detection signals of the test interference signal; the elliptic curve is:
wherein,
Sc2(t) and Sc3(t) is denoted by Sc2And Sc3；
Step S104: carrying out ellipse parameter fitting on the constructed elliptic curve to obtain a fitting value of each elliptic curve parameter;
step S105: and obtaining the estimated value of the demodulation system parameter according to the fitting value of the elliptic curve parameter.
2. The method for demodulating interference-type optical fiber hydrophone signals according to claim 1, wherein the step S200 is specifically as follows:
step S201: placing the optical fiber hydrophone in a measuring environment to measure a measured acoustic signal, and outputting an actual interference signal by the optical fiber hydrophone to input the actual interference signal into a signal demodulation system;
step S202: multiplying the actual interference signal by a carrier frequency second and third frequency multiplication reference signal respectively and obtaining a second and third frequency multiplication detection signal of the actual interference signal through low-pass filtering;
step S203: correcting second and third frequency multiplication detection signals of the actual interference signal by using the demodulation system parameter estimation value to obtain an orthogonal demodulation signal;
step S204: and performing orthogonal signal demodulation calculation by using the orthogonal demodulation signal to obtain the measured acoustic signal.
3. The method for demodulating interference-type optical fiber hydrophone signals according to claim 1, wherein the step S105 specifically comprises: obtaining demodulation system parameters B according to fitting values of elliptic curve parameters a, B, c, d, e and f2,B3And δ estimate:
4. the method for demodulating interference-type optical fiber hydrophone signals according to claim 1, wherein the step S203 specifically comprises: using demodulation system parameter estimate B2,B3Second and third frequency-multiplication detection signal S of delta pair actual interference signalt2And St3Correction is performed to obtain quadrature demodulation signals SR and CR:
wherein,
5. The method for demodulating interference-type optical fiber hydrophone signals according to claim 4, wherein the step S204 specifically comprises: orthogonal signal demodulation calculation is carried out by utilizing orthogonal demodulation signals SR and CR to obtain the tested acoustic signal
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| CN111579047A (en) * | 2020-05-09 | 2020-08-25 | 中国电子科技集团公司第七研究所 | Signal demodulation method of optical fiber vector hydrophone |
| CN111693133B (en) * | 2020-06-24 | 2022-04-15 | 中国电子产品可靠性与环境试验研究所（（工业和信息化部电子第五研究所）（中国赛宝实验室）） | Optical path difference testing device and method for optical fiber hydrophone and computer equipment |
| CN113375785B (en) * | 2021-06-08 | 2022-04-15 | 中国人民解放军国防科技大学 | Method for detecting full-sea-depth high-stability photoelectric signal of optical fiber hydrophone |
| CN114383635B (en) * | 2022-01-17 | 2022-11-04 | 中国人民解放军国防科技大学 | PGC signal detection additional phase noise suppression method based on initial phase zero setting |
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| CN101604957A (en) * | 2009-07-13 | 2009-12-16 | 中国船舶重工集团公司第七一五研究所 | A kind of PGC complex demodulation method for large-scale optical fiber hydrophone array |
| JP5652229B2 (en) * | 2011-01-26 | 2015-01-14 | 沖電気工業株式会社 | Interferometric optical fiber sensor system |
| CN102147552A (en) * | 2011-03-11 | 2011-08-10 | 大连理工大学 | Unbalanced interferometer based fiber bragg grating (FBG) demodulation system and method |
| CN106124029B (en) * | 2016-06-17 | 2020-12-29 | 中国人民解放军国防科学技术大学 | Optical fiber hydrophone system based on micro-nano optical fiber all-optical phase modulator |
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