CN116047485B - Sound signal demodulation method and device - Google Patents

Sound signal demodulation method and device Download PDF

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Publication number
CN116047485B
CN116047485B CN202310320021.0A CN202310320021A CN116047485B CN 116047485 B CN116047485 B CN 116047485B CN 202310320021 A CN202310320021 A CN 202310320021A CN 116047485 B CN116047485 B CN 116047485B
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signal
acoustic
optical
phase
frequency
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CN116047485A (en
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路阳
孟洲
王建飞
陈默
胡晓阳
陈伟
陈羽
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National University of Defense Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention provides a sound signal demodulation method and a sound signal demodulation device, which firstly generate H double-light pulses, and inject the generated H double-light pulses into a sound matrix at a repetition frequency; and then, H interference signal sequences returned by the acoustic array are obtained at the same repetition frequency, and an acoustic wave time domain signal detected at the position z of the acoustic array is obtained.

Description

Sound signal demodulation method and device
Technical Field
The invention mainly relates to the technical field of acoustic signal demodulation, in particular to an acoustic signal demodulation method and device.
Background
With the development of distributed acoustic wave sensing technology and optical fiber microstructure processing technology, an acoustic array is formed by adopting a single optical fiber, and the phase information of the interference signal is demodulated and extracted by detecting the interference signal output by the acoustic array, so that the complete information of the frequency, amplitude, phase and position of external acoustic waves can be obtained at the same time, and distributed acoustic wave detection is realized.
The acoustic signal demodulation method is a key for extracting acoustic signals in a distributed acoustic wave detection technology based on an acoustic array, and detection noise, a dynamic range and a frequency response range are core indexes of the acoustic signal demodulation method, so that detection distance, amplitude response range and frequency response range of the acoustic signals are determined.
The low-frequency heterodyne phase demodulation technique and the Phase Generating Carrier (PGC) phase demodulation technique are classical acoustic signal demodulation methods. The method is carried out by frequency
Figure SMS_1
Periodically injecting detection light pulse into the sensing array, and obtaining time-varying dry by introducing heterodyne frequency or phase modulationTo the signal and demodulating therefrom to obtain the acoustic signal. The dynamic range of the above method is determined by the heterodyne frequency or the phase modulation frequency. Because heterodyne frequency or phase modulation frequency is lower than pulse repetition frequency +.>
Figure SMS_2
The heterodyne frequency and the phase modulation frequency of the existing method are only of the kHz magnitude, and the dynamic range is severely limited. If the heterodyne frequency or the phase modulation frequency is increased to the MHz level, the dynamic range is increased linearly. At the same time, because the heterodyning frequency or the phase modulation frequency is lower than the pulse repetition frequency +.>
Figure SMS_3
The frequency of the intensity of the interference signal over time is lower than +.>
Figure SMS_4
. By collecting a series of interference pulse intensities to form a time-varying interference signal, and combining the phase demodulation technology, acoustic wave information contained in the phase of the interference signal can be obtained. For the two signal demodulation methods, the collection frequency of the interference signal intensity is the optical pulse frequency +.>
Figure SMS_5
. According to the requirements of the low-frequency heterodyne phase demodulation technique or the PGC phase demodulation algorithm, the sampling rate of the time-lapse interference signal is at least 8 times the phase modulation frequency or the heterodyne frequency, and therefore the upper limit of the phase modulation frequency and the heterodyne frequency is +.>
Figure SMS_6
. Considering the dynamic range of the acoustic wave signal detection, the common phase modulation frequency and heterodyne frequency are more than 8 times of the highest frequency of the acoustic wave signal to be detected. Therefore, the highest frequency of the acoustic wave signal to be measured is only +.>
Figure SMS_7
The frequency response range is severely limited.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides an acoustic signal demodulation method and device.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
in one aspect, the present invention provides an acoustic signal demodulation method, including:
generating H double light pulses at a repetition frequency
Figure SMS_8
Injecting the generated H double light pulses into an acoustic matrix, whereintThe optical frequency difference between two optical pulses in the time double optical pulse is +.>
Figure SMS_9
And phase difference->
Figure SMS_10
WhereinCFor modulating amplitude for phase>
Figure SMS_11
Is the phase modulation frequency;
at a repetition rate of
Figure SMS_14
Obtaining H interference signals returned by the acoustic array, wherein each interference signal has the same duration and is +.>
Figure SMS_18
Wherein, the method comprises the steps of, wherein,cthe speed of light in the vacuum is indicated,nfor the effective refractive index of the sensing fiber in the acoustic matrix,Llength of sensing optical fiber in acoustic matrix, the firsthThe alternating part of the interference signal is denoted +.>
Figure SMS_21
，/>
Figure SMS_15
First, thehThe interference signal comprises->
Figure SMS_17
Beat frequency signals with different frequencies, beat frequency is +.>
Figure SMS_20
，
Figure SMS_23
Represent the firsthThe beat frequency in the interference signal is +.>
Figure SMS_12
Amplitude, phase of interference signal of (2)>
Figure SMS_16
Is the same-frequency phase signal caused by the acoustic signal to be measured, the amplitude is in direct proportion to the acoustic signal, +.>
Figure SMS_19
In order for the fading noise to be a fading noise,pto meet the requirements of
Figure SMS_22
Is a positive integer of (a) and (b),kis an integer and satisfies->
Figure SMS_13
；
Will be
Figure SMS_24
Respectively and->
Figure SMS_25
And->
Figure SMS_26
Multiplying, and respectively low-pass filtering to obtain +.>
Figure SMS_27
Zero frequency quadrature signal->
Figure SMS_28
And->
Figure SMS_29
；
By means of
Figure SMS_30
Zero frequency quadrature signal->
Figure SMS_31
And->
Figure SMS_32
Construction->
Figure SMS_33
Plural->
Figure SMS_34
；
By means of
Figure SMS_35
Plural->
Figure SMS_36
Construction of fusion Complex->
Figure SMS_37
；
Figure SMS_38
；
Wherein:
Figure SMS_39
for the complex number constructed from the first interference signal, its modulus is +.>
Figure SMS_40
The symbols are conjugate symbols, ++>
Figure SMS_41
The phase of the signal carried by the first interference signal is constant, and the obtained fusion complex number +.>
Figure SMS_42
Is of the phase of
Figure SMS_43
No longer contains fading noise->
Figure SMS_44
；
By means of
Figure SMS_45
Real part of->
Figure SMS_46
And imaginary part->
Figure SMS_47
Obtaining phase information by an arctangent function
Figure SMS_48
；
By means of
Figure SMS_49
Will->
Figure SMS_50
Conversion to->
Figure SMS_51
Represents the firsthWhen a double light pulse is injected into the acoustic array, the phase at the position z of the acoustic array is also representative of the amplitude of the acoustic signal detected at the position z of the acoustic array, where +.>
Figure SMS_52
The winding ratio of the sensing optical fiber wound on the sensitization elastomer is represented;
will be H phases
Figure SMS_53
Arranged according to the access sequence to obtain time-varying phase signals
Figure SMS_54
The time-varying phase signal represents an acoustic time-domain signal detected at acoustic array position z.
As a preferred embodiment, the present invention uses
Figure SMS_55
Zero frequency quadrature signal->
Figure SMS_56
And
Figure SMS_57
construction->
Figure SMS_58
Plural->
Figure SMS_59
The method comprises the following steps:
Figure SMS_60
；
the maximum response frequency of the acoustic signal demodulation method of the invention is
Figure SMS_61
。/>
In another aspect, the present invention provides an acoustic signal demodulation apparatus, comprising:
a double light pulse generating component for generating H double light pulses at a repetition frequency
Figure SMS_62
Injecting the generated H double light pulses into an acoustic matrix, whereintThe optical frequency difference between two optical pulses in the time double optical pulse is +.>
Figure SMS_63
And phase difference->
Figure SMS_64
WhereinCFor modulating amplitude for phase>
Figure SMS_65
Is the phase modulation frequency;
data acquisition and preprocessing component for repeating at a repetition rate
Figure SMS_67
Obtaining H interference signals returned by the acoustic array, wherein each interference signal has the same duration and is +.>
Figure SMS_70
Wherein, the method comprises the steps of, wherein,cthe speed of light in the vacuum is indicated,nfor the effective refractive index of the sensing fiber in the acoustic matrix,Llength of sensing optical fiber in acoustic matrix, the firsthThe alternating part of the interference signal is expressed as
Figure SMS_73
，/>
Figure SMS_68
First, thehThe interference signal comprises->
Figure SMS_71
Beat frequency signals with different frequencies, beat frequency is +.>
Figure SMS_74
，/>
Figure SMS_76
Represent the firsthThe beat frequency in the interference signal is +.>
Figure SMS_69
Amplitude, phase of interference signal of (2)>
Figure SMS_72
Is the same-frequency phase signal caused by the acoustic signal to be measured, the amplitude is in direct proportion to the acoustic signal, +.>
Figure SMS_75
In order for the fading noise to be a fading noise,pto meet->
Figure SMS_77
Is a positive integer of (a) and (b),kis an integer and satisfies->
Figure SMS_66
；
The signal processor is used for acquiring the sound wave time domain signal detected at the sound matrix position z, and the signal processing process comprises the following steps:
will be
Figure SMS_78
Respectively and->
Figure SMS_79
And->
Figure SMS_80
Multiplying, and respectively low-pass filtering to obtain
Figure SMS_81
Zero frequency quadrature signal->
Figure SMS_82
And->
Figure SMS_83
；
Using 2p+1 pair zero frequency quadrature signals
Figure SMS_84
And->
Figure SMS_85
Construction->
Figure SMS_86
Plural->
Figure SMS_87
；
By means of
Figure SMS_88
Plural->
Figure SMS_89
Construction of fusion Complex->
Figure SMS_90
；
By means of
Figure SMS_91
Real part of->
Figure SMS_92
And imaginary part->
Figure SMS_93
Obtaining phase information by an arctangent function
Figure SMS_94
；
By means of
Figure SMS_95
Will->
Figure SMS_96
Conversion to->
Figure SMS_97
Represents the firsthWhen a double light pulse is injected into the acoustic array, the phase at the position z of the acoustic array is also representative of the amplitude of the acoustic signal detected at the position z of the acoustic array, where +.>
Figure SMS_98
The winding ratio of the sensing optical fiber wound on the sensitization elastomer is represented;
will be H phases
Figure SMS_99
Arranged according to the access sequence to obtain time-varying phase signals
Figure SMS_100
，/>
Figure SMS_101
The signal phase carried for the first interference signal is constant and the time-varying phase signal represents the acoustic time-domain signal detected at the acoustic array position z.
As a preferable scheme, the double-light pulse generating component comprises a narrow linewidth laser, a first acousto-optic modulator, an unbalanced interferometer and a circulator, wherein the narrow linewidth laser, the first acousto-optic modulator and the unbalanced interferometer are sequentially connected; the narrow linewidth laser is used for generating high-coherence continuous laser; the first acousto-optic modulator generates optical pulse according to the set pulse modulation signal period, and the optical pulse repetition frequency
Figure SMS_102
Pulse width->
Figure SMS_103
The method comprises the steps of carrying out a first treatment on the surface of the The unbalanced interferometer is used for generating signals with a time delay +.>
Figure SMS_104
Optical frequency difference->
Figure SMS_105
And phase difference->
Figure SMS_106
Is a double light pulse of (2); the double optical pulse is injected into the acoustic array from the second port of the circulator, and the return optical signal returned by the acoustic array is received by the second port of the circulator, and is output from the third port of the circulator.
As a preferred scheme, the unbalanced interferometer comprises a first optical fiber coupler, a second optical modulator, a phase modulator and a second optical fiber coupler, wherein the input end of the first optical fiber coupler is connected with the output end of the first optical fiber modulator, the two output ends of the first optical fiber coupler are respectively connected with the input end of the second optical modulator and the input end of the phase modulator, the output end of the second optical modulator and the output end of the phase modulator are respectively connected with the two input ends of the second optical fiber coupler, and the output end of the second optical fiber coupler serves as the output end of the unbalanced interferometer and is used for outputting double light pulses; the second acoustic optical modulator is used for adjusting the frequency
Figure SMS_107
Is subjected to an optical frequency shift of the optical pulse by an amount of +.>
Figure SMS_108
The phase modulator is used for carrying out sinusoidal optical phase modulation on the optical pulse according to the second sinusoidal modulation signal, and modulating the phase +.>
Figure SMS_109
。
The double-light pulse generating assembly also comprises a first light amplifier and a first light filter, wherein the output end of the unbalanced interferometer is connected with the first light amplifier and the first light filter, and the double-light pulse output by the unbalanced interferometer is amplified and filtered and then is injected into the acoustic array from the second port of the circulator.
As a preferable scheme, the data acquisition and preprocessing component comprises a photoelectric detector and a data acquisition card;
the photoelectric detector is used for acquiring a return optical signal returned by the acoustic array and converting the return optical signal into an electric signal;
the data acquisition card is used for acquiring the electric signals output by the photoelectric detector according to the trigger signals and the clock signals and providing the electric signals for the signal processor.
Preferably, the data acquisition and preprocessing component further comprises a second optical amplifier and a second optical filter, and the return optical signal output from the third port of the circulator is amplified and filtered by the second optical amplifier and the second optical filter and then input into the photoelectric detector.
The invention also comprises a signal generator, which is used for generating the pulse modulation signal of the first acousto-optic modulator, generating the second sinusoidal modulation signal of the phase modulator, generating the first sinusoidal modulation signal of the second acousto-optic modulator, and generating the trigger signal and the clock signal of the data acquisition card.
Compared with the prior art, the invention has the technical effects that:
the invention adopts a direct detection scheme to reduce light source noise, adopts phase modulation to realize frequency diversity, constructs complex numbers, inhibits fading noise, reduces detection noise of a sonar system, expands detection distance, adopts a high-frequency heterodyne technology, improves dynamic range of acoustic signal demodulation, and expands frequency response range of acoustic signals.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of an acoustic signal demodulation apparatus according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an acoustic signal demodulation apparatus according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an acoustic signal demodulation apparatus according to an embodiment of the present invention;
fig. 4 is a schematic structural view of an acoustic array according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, descriptions such as those referred to as "first," "second," and the like, are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying an order of magnitude of the indicated technical features in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless specifically stated and limited otherwise, the terms "connected," "affixed," and the like are to be construed broadly, and for example, "affixed" may be a fixed connection, a removable connection, or an integral body; the device can be mechanically connected, electrically connected, physically connected or wirelessly connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In addition, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the technical solutions, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered as not existing, and not falling within the scope of protection claimed by the present invention.
Referring to fig. 1, in one embodiment of the present invention, there is provided an acoustic signal demodulation method including:
generating H double light pulses at a repetition frequency
Figure SMS_110
Injecting the generated H double light pulses into an acoustic matrix, whereintThe optical frequency difference between two optical pulses in the time double optical pulse is +.>
Figure SMS_111
And phase difference->
Figure SMS_112
WhereinCFor modulating amplitude for phase>
Figure SMS_113
Is the phase modulation frequency;
at a repetition rate of
Figure SMS_114
Obtaining H interference signals returned by the acoustic array, wherein each interference signal has the same duration and is +.>
Figure SMS_118
Wherein, the method comprises the steps of, wherein,cthe speed of light in the vacuum is indicated,nfor the effective refractive index of the sensing fiber in the acoustic matrix,Llength of sensing optical fiber in acoustic matrix, the firsthThe alternating part of the interference signal is denoted +.>
Figure SMS_121
，
Figure SMS_115
First, thehThe interference signal comprises->
Figure SMS_119
Beat frequency signals with different frequencies, beat frequency is +.>
Figure SMS_122
，
Figure SMS_124
Represent the firsthThe beat frequency in the interference signal is +.>
Figure SMS_117
Amplitude, phase of interference signal of (2)>
Figure SMS_120
Is the same-frequency phase signal caused by the acoustic signal to be measured, the amplitude is in direct proportion to the acoustic signal, +.>
Figure SMS_123
In order for the fading noise to be a fading noise,pto meet the requirements of
Figure SMS_125
Is a positive integer of (a) and (b),kis an integer and satisfies->
Figure SMS_116
；
Will be
Figure SMS_126
Respectively and->
Figure SMS_127
And->
Figure SMS_128
Multiplying, and respectively low-pass filtering to obtain +.>
Figure SMS_129
Zero frequency quadrature signal->
Figure SMS_130
And->
Figure SMS_131
；
By means of
Figure SMS_132
Zero frequency quadrature signal->
Figure SMS_133
And->
Figure SMS_134
Construction->
Figure SMS_135
Plural->
Figure SMS_136
；/>
Figure SMS_137
By->
Figure SMS_138
Plural number of
Figure SMS_139
Construction of fusion Complex->
Figure SMS_140
；
Figure SMS_141
；
Wherein:
Figure SMS_142
for the complex number constructed from the first interference signal, its modulus is +.>
Figure SMS_143
The symbols are the conjugate symbols,
Figure SMS_144
the phase of the signal carried by the first interference signal is constant, and the obtained fusion complex number +.>
Figure SMS_145
Is of the phase of
Figure SMS_146
No longer contains fading noise->
Figure SMS_147
；
By means of
Figure SMS_148
Real part of->
Figure SMS_149
And imaginary part->
Figure SMS_150
Obtaining phase information by an arctangent function
Figure SMS_151
；
By means of
Figure SMS_152
Will->
Figure SMS_153
Conversion to->
Figure SMS_154
Represents the firsthWhen the double light pulses are injected into the acoustic array, the phase at the position z of the acoustic array is represented as well as the detection at the position z of the acoustic arrayAmplitude of the acoustic signal measured, wherein +.>
Figure SMS_155
The winding ratio of the sensing optical fiber wound on the sensitization elastomer is represented;
will be H phases
Figure SMS_156
Arranged according to the access sequence to obtain time-varying phase signals
Figure SMS_157
The time-varying phase signal represents an acoustic time-domain signal detected at acoustic array position z.
The acquisition frequency of the acoustic signals in the above embodiment of the invention is the repetition frequency of the optical pulse
Figure SMS_158
The maximum response frequency of the acoustic signal demodulation method is +.>
Figure SMS_159
。
Referring to fig. 1, in one embodiment of the present invention, there is provided an acoustic signal demodulation apparatus including:
a double light pulse generating assembly 100 for generating H double light pulses and passing through the circulator 200 at a repetition frequency
Figure SMS_160
The generated H double light pulses are injected into acoustic matrix 300, whereintThe optical frequency difference between two optical pulses in the time double optical pulse is +.>
Figure SMS_161
And phase difference->
Figure SMS_162
WhereinCFor modulating amplitude for phase>
Figure SMS_163
Is the phase modulation frequency; meanwhile, the circulator 200 receives a return light signal returned by the acoustic array 300;
a data acquisition and preprocessing module 400 for use in a repetition rate
Figure SMS_165
Obtaining H interference signals returned by the acoustic array, wherein each interference signal has the same duration and is +.>
Figure SMS_168
Wherein, the method comprises the steps of, wherein,cthe speed of light in the vacuum is indicated,nfor the effective refractive index of the sensing fiber in the acoustic matrix,Llength of sensing optical fiber in acoustic matrix, the firsthThe alternating part of the interference signal is expressed as
Figure SMS_171
，/>
Figure SMS_166
First, thehThe interference signal comprises->
Figure SMS_169
Beat frequency signals with different frequencies, beat frequency is +.>
Figure SMS_172
，/>
Figure SMS_174
Represent the firsthThe beat frequency in the interference signal is +.>
Figure SMS_167
Amplitude, phase of interference signal of (2)>
Figure SMS_170
Is the same-frequency phase signal caused by the acoustic signal to be measured, the amplitude is in direct proportion to the acoustic signal, +.>
Figure SMS_173
In order for the fading noise to be a fading noise,pto meet->
Figure SMS_175
Is a positive integer of (a) and (b),kis an integer and satisfies->
Figure SMS_164
；
A signal processor 500 for acquiring an acoustic time domain signal detected at acoustic array position z.
In the above embodiment, the signal processing procedure of the signal processor includes:
will be
Figure SMS_176
Respectively and->
Figure SMS_177
And->
Figure SMS_178
Multiplying, and respectively low-pass filtering to obtain +.>
Figure SMS_179
Zero frequency quadrature signal->
Figure SMS_180
And->
Figure SMS_181
；
By means of
Figure SMS_182
Zero frequency quadrature signal->
Figure SMS_183
And->
Figure SMS_184
Construction->
Figure SMS_185
Plural->
Figure SMS_186
；
Figure SMS_187
By->
Figure SMS_188
Plural number of
Figure SMS_189
Construction of fusion Complex->
Figure SMS_190
；
Figure SMS_191
Wherein:
Figure SMS_192
to make sure that the first interference signalh=1) complex number constructed with a modulus of +.>
Figure SMS_193
The symbols are conjugate symbols, ++>
Figure SMS_194
The phase of the signal carried by the first interference signal is constant, and the phase of the complex number obtained by the above calculation is +.>
Figure SMS_195
No longer contains fading noise->
Figure SMS_196
。
By means of
Figure SMS_197
Real part of->
Figure SMS_198
And imaginary part->
Figure SMS_199
Obtaining phase information by an arctangent function
Figure SMS_200
；
By means of
Figure SMS_201
Will->
Figure SMS_202
Conversion to->
Figure SMS_203
Represents the firsthWhen a double light pulse is injected into the acoustic array, the phase at the position z of the acoustic array is also representative of the amplitude of the acoustic signal detected at the position z of the acoustic array, where +.>
Figure SMS_204
The winding ratio of the sensing optical fiber wound on the sensitization elastomer is represented;
will be H phases
Figure SMS_205
Arranged according to the access sequence to obtain time-varying phase signals
Figure SMS_206
Due to->
Figure SMS_207
Is constant and does not affect the amplitude, frequency and phase of the time-varying phase signal, so the resulting time-varying phase signal is representative of the acoustic time-domain signal detected at the acoustic array position z.
Referring to fig. 2, in an embodiment of the present invention, the dual optical pulse generating assembly 100 includes a narrow linewidth laser 101, a first acousto-optic modulator 102 and an unbalanced interferometer 103, where the narrow linewidth laser 101, the first acousto-optic modulator 102 and the unbalanced interferometer 103 are sequentially connected; the narrow linewidth laser 101 is used for generating high-coherence continuous laser; the first acousto-optic modulator 102 generates optical pulses according to a set pulse modulation signal period, and the repetition frequency of the optical pulses
Figure SMS_208
Pulse width->
Figure SMS_209
The method comprises the steps of carrying out a first treatment on the surface of the For the unbalanced interferometer 103Generating a clock signal with delay->
Figure SMS_210
Optical frequency difference->
Figure SMS_211
And phase difference->
Figure SMS_212
Is a double light pulse of (2); the double optical pulse is injected into the acoustic array 300 from the second port of the circulator 200, and the return optical signal returned from the acoustic array 300 is received by the second port of the circulator 200, and is output from the third port of the circulator 200.
Referring to fig. 2, in the present embodiment, the unbalanced interferometer 103 includes a first optical fiber coupler 1031, a second optical modulator 1033, a phase modulator 1032, and a second optical fiber coupler 1034, where an input end of the first optical fiber coupler 1031 is connected to an output end of the first optical fiber modulator 102, two output ends of the first optical fiber coupler 1031 are respectively connected to an input end of the second optical modulator 1033 and an input end of the phase modulator 1032, an output end of the second optical fiber modulator 1033 and an output end of the phase modulator 1032 are respectively connected to two input ends of the second optical fiber coupler 1034, and an output end of the second optical fiber coupler 1034 serves as an output end of the unbalanced interferometer 103 for outputting dual optical pulses; the second acoustic optical modulator 1033 is for use in accordance with the frequency
Figure SMS_213
Is subjected to an optical frequency shift of the optical pulse by an amount of +.>
Figure SMS_214
The phase modulator 1032 is used for performing sinusoidal optical phase modulation on the optical pulse according to the second sinusoidal modulation signal, and modulating the phase +.>
Figure SMS_215
。
Referring to fig. 2, in the present embodiment, the data acquisition and preprocessing module 400 includes a photodetector 401 and a data acquisition card 402; the photodetector 401 is configured to acquire a return optical signal returned by the acoustic array, and convert the return optical signal into an electrical signal; the data acquisition card 402 is used for acquiring the electrical signals output by the photoelectric detector according to the trigger signal and the clock signal, and providing the electrical signals to the signal processor.
Referring to fig. 2, in the present embodiment, the signal generator 600 generates the pulse modulation signal of the first acousto-optic modulator 102, generates the second sinusoidal modulation signal of the phase modulator 1032, generates the first sinusoidal modulation signal of the second acoustic optical modulator 1033, and generates the trigger signal and the clock signal of the data acquisition card 402.
Referring to fig. 3, in another embodiment of the present invention, the dual optical pulse generating assembly 100 includes a narrow linewidth laser 101, a first acousto-optic modulator 102, an unbalanced interferometer 103, a first optical amplifier 104 and a first optical filter 105, where the narrow linewidth laser 101, the first acousto-optic modulator 102 and the unbalanced interferometer 103 are sequentially connected; the narrow linewidth laser 101 is used for generating high-coherence continuous laser; the first acousto-optic modulator 102 generates optical pulses according to a set pulse modulation signal period, and the repetition frequency of the optical pulses
Figure SMS_216
Pulse width->
Figure SMS_217
The method comprises the steps of carrying out a first treatment on the surface of the Said unbalanced interferometer 103 is used for generating signals with a time delay +.>
Figure SMS_218
Optical frequency difference->
Figure SMS_219
And phase difference->
Figure SMS_220
Is a double light pulse of (2); the output end of the unbalanced interferometer 103 is connected with a first optical amplifier 104 and a first optical filter 105, and the double optical pulses output by the unbalanced interferometer 103 are amplified and filtered and then injected into the acoustic array 300 from the second port of the circulator 200, and the acoustic array 300 is received by the second port of the circulator 200A return optical signal is returned, which is again output from the third port of the circulator 200.
Referring to fig. 3, in this embodiment, the unbalanced interferometer 103 includes a first optical fiber coupler 1031, a second optical modulator 1033, a phase modulator 1032, and a second optical fiber coupler 1034, where an input end of the first optical fiber coupler 1031 is connected to an output end of the first optical fiber modulator 102, two output ends of the first optical fiber coupler 1031 are respectively connected to an input end of the second optical modulator 1033 and an input end of the phase modulator 1032, an output end of the second optical fiber modulator 1033 and an output end of the phase modulator 1032 are respectively connected to two input ends of the second optical fiber coupler 1034, and an output end of the second optical fiber coupler 1034 serves as an output end of the unbalanced interferometer 103 for outputting dual light pulses; the second acoustic optical modulator 1033 is for use in accordance with the frequency
Figure SMS_221
Is subjected to an optical frequency shift of the optical pulse by an amount of +.>
Figure SMS_222
The phase modulator 1032 is used for performing sinusoidal optical phase modulation on the optical pulse according to the second sinusoidal modulation signal, and modulating the phase +.>
Figure SMS_223
。
Referring to fig. 3, in the present embodiment, the data acquisition and preprocessing module 400 includes a photodetector 401, a data acquisition card 402, a second optical amplifier 403, and a second optical filter 404; the return optical signal output from the third port of the circulator 200 is amplified and filtered by the second optical amplifier 403 and the second optical filter 404, and then is input to the photodetector 401, where the photodetector 401 is used to obtain the return optical signal returned by the acoustic array and convert the return optical signal into an electrical signal; the data acquisition card 402 is used for acquiring the electrical signals output by the photoelectric detector according to the trigger signal and the clock signal, and providing the electrical signals to the signal processor.
Referring to fig. 3, in the present embodiment, the signal generator 600 generates the pulse modulation signal of the first acousto-optic modulator 102, generates the second sinusoidal modulation signal of the phase modulator 1032, generates the first sinusoidal modulation signal of the second acoustic optical modulator 1033, and generates the trigger signal and the clock signal of the data acquisition card 402.
The dynamic range of the demodulation of the acoustic signal is determined by the heterodyne frequency (beat frequency), the higher the frequency, the greater the dynamic range. The low-frequency heterodyne phase demodulation technique and the Phase Generating Carrier (PGC) phase demodulation technique are classical acoustic signal demodulation methods. The above-mentioned prior demodulation method requires heterodyne frequency or phase modulation frequency to be lower than pulse repetition frequency, so heterodyne frequency and phase modulation frequency of the prior method are only of kHz magnitude, and dynamic range is severely limited. The heterodyne frequency of the acoustic signal demodulation method is not limited by the repetition frequency of the optical pulse, and can reach the order of 100MHz, so that the dynamic range is greatly improved.
The acquisition frequency of the acoustic signals in the embodiment of the invention is the repetition frequency of the optical pulse
Figure SMS_224
The maximum response frequency of the acoustic signal demodulation module is +.>
Figure SMS_225
. In one embodiment, the light pulse width +.>
Figure SMS_226
,/>
Figure SMS_227
，
Figure SMS_228
。
FIG. 4 is a schematic diagram of an acoustic array according to an embodiment of the present invention, where the acoustic array is composed of a continuous fiber hydrophone array 121, and the continuous fiber hydrophone array 121 is composed of sensing fibers 1211 and a sensitizer 1212, and has a length ofLIs provided with a sensing fiber 1211 of a winding ratio
Figure SMS_229
Is continuously wound around the sensitization body 1212,i.e. a constructional length of +.>
Figure SMS_230
For sensing external acoustic signals with high sensitivity.
The specific structure and model of the sensing optical fiber are not limited, and the sensing optical fiber commonly used in the prior art can be adopted. As a preferable scheme, the sensing optical fiber is optimally selected to be a bending-resistant optical fiber, and the bending loss of the bending-resistant optical fiber can be reduced through verification, so that the signal-to-noise ratio of an optical signal is improved, and the detection noise is reduced.
The core refractive index of the sensing fiber may be fixed. The applicant has long-term research and experimental demonstration that the optimization design modulation of the refractive index of the fiber core of the sensing optical fiber can effectively improve the signal-to-noise ratio of the optical signal and reduce the detection noise. More preferably, the refractive index of the core of the sensing fiber is spaced apart by the fiber distance
Figure SMS_231
The periodic variation can significantly improve the signal-to-noise ratio of the optical signal and reduce the detection noise, wherein,cthe speed of light in the vacuum is indicated,nis the effective refractive index of the optical fiber.
The invention is not a matter of the known technology.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.

Claims (10)

1. An acoustic signal demodulation method, comprising:
generating H double light pulses at a repetition frequencyf p Injecting the generated H double light pulses into an acoustic matrix, whereintThe optical frequency difference exists between two optical pulses in the time double optical pulses
Figure QLYQS_1
And phase difference->
Figure QLYQS_2
WhereinCFor the phase modulation of the amplitude,f m is the phase modulation frequency;
at a repetition rate off p Obtaining H interference signals returned by the acoustic array, wherein each interference signal has the same duration and is
Figure QLYQS_4
Wherein, the method comprises the steps of, wherein,cthe speed of light in the vacuum is indicated,nfor the effective refractive index of the sensing fiber in the acoustic matrix,Llength of sensing optical fiber in acoustic matrix, the firsthThe alternating part of the interference signal is expressed as
Figure QLYQS_6
，h=1, 2, …, H, thhThe interference signal comprises 2p+1 beat signals of different frequencies, beat frequency +.>
Figure QLYQS_9
，/>
Figure QLYQS_5
Represent the firsthThe beat frequency in the interference signal is +.>
Figure QLYQS_8
Amplitude, phase of interference signal of (2)>
Figure QLYQS_10
Is the same-frequency phase signal caused by the acoustic signal to be measured, the amplitude is in direct proportion to the acoustic signal, +.>
Figure QLYQS_11
In order for the fading noise to be a fading noise,pto meet->
Figure QLYQS_3
Is a positive integer of (a) and (b),kis an integer and satisfies->
Figure QLYQS_7
；
Will be
Figure QLYQS_12
Respectively and->
Figure QLYQS_13
And->
Figure QLYQS_14
Multiplying, and respectively performing low-pass filtering to obtain 2p+1 pair zero frequency orthogonal signals ∈>
Figure QLYQS_15
And->
Figure QLYQS_16
；
Using 2p+1 pair zero frequency quadrature signals
Figure QLYQS_17
And
Figure QLYQS_18
construction of 2p+1 plural->
Figure QLYQS_19
；
Using 2p+1 complex numbers
Figure QLYQS_20
Construction of fusion Complex->
Figure QLYQS_21
；
Figure QLYQS_22
，
Wherein:
Figure QLYQS_23
for the complex number constructed from the first interference signal, its modulus is +.>
Figure QLYQS_24
Sign->
Figure QLYQS_25
Is conjugate symbol->
Figure QLYQS_26
The phase of the signal carried by the first interference signal is constant, and the obtained fusion complex number +.>
Figure QLYQS_27
Is +.>
Figure QLYQS_28
No longer contains fading noise->
Figure QLYQS_29
；
By means of
Figure QLYQS_30
Real part of->
Figure QLYQS_31
And imaginary part->
Figure QLYQS_32
Obtaining phase information by an arctangent function
Figure QLYQS_33
；
By means of
Figure QLYQS_34
Will->
Figure QLYQS_35
Conversion to->
Figure QLYQS_36
Represents the firsthWhen a double light pulse is injected into the acoustic array, the phase at the position z of the acoustic array is also representative of the amplitude of the acoustic signal detected at the position z of the acoustic array, where +.>
Figure QLYQS_37
The winding ratio of the sensing optical fiber wound on the sensitization elastomer is represented;
will be H phases
Figure QLYQS_38
Arranged according to the access sequence to obtain time-varying phase signals
Figure QLYQS_39
The time-varying phase signal represents an acoustic time-domain signal detected at acoustic array position z.
2. The acoustic signal demodulation method of claim 1, wherein the maximum response frequency of the acoustic signal demodulation method isf p /2。
3. An acoustic signal demodulation apparatus, comprising:
a double light pulse generating component for generating H double light pulses at a repetition frequencyf p Injecting the generated H double light pulses into an acoustic matrix, whereintThe optical frequency difference exists between two optical pulses in the time double optical pulses
Figure QLYQS_40
And phase difference->
Figure QLYQS_41
WhereinCFor the phase modulation of the amplitude,f m is the phase modulation frequency;
data acquisition and preprocessing component for repeating at a repetition ratef p Obtaining H interference signals returned by the acoustic array, wherein each interference signal has the same duration and is
Figure QLYQS_44
Wherein, the method comprises the steps of, wherein,cthe speed of light in the vacuum is indicated,nfor the effective refractive index of the sensing fiber in the acoustic matrix,Llength of sensing optical fiber in acoustic matrix, the firsthThe alternating part of the interference signal is expressed as
Figure QLYQS_47
，h=1, 2, …, H, thhThe interference signal comprises 2p+1 beat signals of different frequencies, beat frequency +.>
Figure QLYQS_49
，/>
Figure QLYQS_43
Represent the firsthThe beat frequency in the interference signals is
Figure QLYQS_46
Amplitude, phase of interference signal of (2)>
Figure QLYQS_48
Is the same-frequency phase signal caused by the acoustic signal to be measured, the amplitude is in direct proportion to the acoustic signal, +.>
Figure QLYQS_50
In order for the fading noise to be a fading noise,pto meet->
Figure QLYQS_42
Is a positive integer of (a) and (b),kis an integer and satisfies
Figure QLYQS_45
；
The signal processor is used for acquiring the sound wave time domain signal detected at the sound matrix position z, and the signal processing process comprises the following steps:
will be
Figure QLYQS_51
Respectively and->
Figure QLYQS_52
And->
Figure QLYQS_53
Multiplying, and respectively performing low-pass filtering to obtain 2p+1 pair zero frequency orthogonal signals ∈>
Figure QLYQS_54
And->
Figure QLYQS_55
；
Using 2p+1 pair zero frequency quadrature signals
Figure QLYQS_56
And->
Figure QLYQS_57
Construction of 2p+1 plural->
Figure QLYQS_58
；
Using 2p+1 complex numbers
Figure QLYQS_59
Construction of fusion Complex->
Figure QLYQS_60
；
By means of
Figure QLYQS_61
The real part of (2)/>
Figure QLYQS_62
And imaginary part->
Figure QLYQS_63
Obtaining phase information by an arctangent function
Figure QLYQS_64
；
By means of
Figure QLYQS_65
Will->
Figure QLYQS_66
Conversion to->
Figure QLYQS_67
Represents the firsthWhen a double light pulse is injected into the acoustic array, the phase at the position z of the acoustic array is also representative of the amplitude of the acoustic signal detected at the position z of the acoustic array, where +.>
Figure QLYQS_68
The winding ratio of the sensing optical fiber wound on the sensitization elastomer is represented;
will be H phases
Figure QLYQS_69
Arranged according to the access sequence to obtain time-varying phase signals
Figure QLYQS_70
，/>
Figure QLYQS_71
The signal phase carried for the first interference signal is constant and the time-varying phase signal represents the acoustic time-domain signal detected at the acoustic array position z.
4. An acoustic signal demodulation apparatus as claimed in claim 3,the double-light pulse generation assembly is characterized by comprising a narrow linewidth laser, a first acousto-optic modulator, an unbalanced interferometer and a circulator, wherein the narrow linewidth laser, the first acousto-optic modulator and the unbalanced interferometer are sequentially connected; the narrow linewidth laser is used for generating high-coherence continuous laser; the first acousto-optic modulator generates optical pulse according to the set pulse modulation signal period, and the optical pulse repetition frequencyf p Pulse widthWThe method comprises the steps of carrying out a first treatment on the surface of the The unbalanced interferometer is used for generating signals with time delay
Figure QLYQS_72
Optical frequency difference->
Figure QLYQS_73
And phase difference->
Figure QLYQS_74
Is a double light pulse of (2); the double optical pulse is injected into the acoustic array from the second port of the circulator, and the optical signal returned by the acoustic array is received by the second port of the circulator, and the returned optical signal is output from the third port of the circulator.
5. The acoustic signal demodulation apparatus of claim 4, wherein the unbalanced interferometer comprises a first optical fiber coupler, a second optical fiber modulator, a phase modulator, and a second optical fiber coupler, wherein an input end of the first optical fiber coupler is connected to an output end of the first optical fiber modulator, two output ends of the first optical fiber coupler are respectively connected to an input end of the second optical fiber modulator and an input end of the phase modulator, an output end of the second optical fiber modulator and an output end of the phase modulator are respectively connected to two input ends of the second optical fiber coupler, and an output end of the second optical fiber coupler serves as an output end of the unbalanced interferometer for outputting the double optical pulses; the second acoustic optical modulator is used for adjusting the frequency
Figure QLYQS_75
Is subjected to an optical frequency shift of the optical pulse by an amount of +.>
Figure QLYQS_76
The phase modulator is used for carrying out sinusoidal optical phase modulation on the optical pulse according to the second sinusoidal modulation signal, and modulating the phase +.>
Figure QLYQS_77
。
6. The device for demodulating an acoustic signal according to claim 5, wherein the double-optical pulse generating component further comprises a first optical amplifier and a first optical filter, the output end of the unbalanced interferometer is connected with the first optical amplifier and the first optical filter, and the double-optical pulse output by the unbalanced interferometer is amplified and filtered and then injected into the acoustic array from the second port of the circulator.
7. The acoustic signal demodulation apparatus of claims 4, 5 or 6, wherein the data acquisition and preprocessing component comprises a photodetector and a data acquisition card;
the photoelectric detector is used for acquiring a return optical signal returned by the acoustic array and converting the return optical signal into an electric signal;
the data acquisition card is used for acquiring the electric signals output by the photoelectric detector according to the trigger signals and the clock signals and providing the electric signals for the signal processor.
8. The acoustic signal demodulation apparatus of claim 7, wherein the data acquisition and pre-processing assembly further comprises a second optical amplifier and a second optical filter, and the return optical signal output from the third port of the circulator is amplified and filtered by the second optical amplifier and the second optical filter and then input to the photodetector.
9. The acoustic signal demodulation apparatus of claim 7, further comprising a signal generator configured to generate the pulse modulated signal of the first acousto-optic modulator, generate the second sinusoidal modulated signal of the phase modulator, generate the first sinusoidal modulated signal of the second acousto-optic modulator, and generate the trigger signal and the clock signal of the data acquisition card.
10. The acoustic signal demodulation apparatus of claim 4, wherein the acoustic array is comprised of a continuous fiber optic hydrophone array, wherein the continuous fiber optic hydrophone array is comprised of sensing fibers and a sensitizer, and has a length ofLIs a winding ratio of the sensing optical fiber of (2)
Figure QLYQS_78
Continuously wound on the sensitization body, i.e. with a length of +.>
Figure QLYQS_79
Is provided. />
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