CN112747816B - Acoustic wave measuring device based on Y-shaped cavity orthogonal polarization laser - Google Patents
Acoustic wave measuring device based on Y-shaped cavity orthogonal polarization laser Download PDFInfo
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- CN112747816B CN112747816B CN202110036605.6A CN202110036605A CN112747816B CN 112747816 B CN112747816 B CN 112747816B CN 202110036605 A CN202110036605 A CN 202110036605A CN 112747816 B CN112747816 B CN 112747816B
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- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
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Abstract
The invention relates to an acoustic wave measuring device based on a Y-cavity orthogonal polarization laser, which consists of a Y-cavity orthogonal polarization laser, a gas bellows, a gas conduit, sensing gas and a signal acquisition and processing unit. When an external acoustic signal to be measured propagates to the gas bellows, the diaphragm of the gas bellows vibrates, so that the refractive indexes of sensing gas in the cavities of the gas bellows, the gas conduit and the P subsections are changed, the P light frequency of the Y-cavity orthogonal polarization laser is changed, and the S light frequency is kept unchanged. Therefore, the frequency spectrum and intensity information of the sound wave signal can be obtained by measuring the frequency difference variation of the S light and the P light of the Y-cavity orthogonal polarization laser. The invention has the advantages of simple structure, wide spectrum measuring range, high sensitivity, strong practicability and the like. In addition, the invention is not limited to the type and pressure of the sensing gas, the sensing sensitivity can be changed along with the environmental requirement, and the application occasion and the application range are wide.
Description
Technical Field
The invention belongs to the technical fields of optical engineering and acoustic wave detection, and relates to an acoustic wave measuring device based on a Y-shaped cavity orthogonal polarization laser.
Background
Common sound wave detection generally uses pressure type microphones, pressure differential microphones, multichannel interference microphones and other sensors to receive sound pressure in a sound field. The former two are to use the sound wave to be incident on the diaphragm to cause the voltage change to realize the measurement of sound pressure, and the difference is the exposure degree of the diaphragm in the sound field. The multichannel interference microphone is characterized in that the microphone is made into a long tube with a plurality of sound inlets, the tube opening is covered with a vibrating diaphragm, sound waves interfere in different sound inlets, and long-distance sound wave signals can be extracted in a strong noise environment. The three can effectively extract the sound wave signals with medium and high frequency and medium intensity, but the front part of the sound wave signals with low frequency and low intensity is proved to be the front part of the elbow. While in the fields of petroleum and natural gas exploration, underwater communication, seismic monitoring, land, air and water monitoring and the like, a sensor capable of simultaneously realizing weak and medium-high intensity acoustic wave detection is urgently needed (Wonuk Jo,Onur Kilic,and Michel J.F.Digonnet.Highly Sensitive Phase-Front-Modulation Fiber Acoustic Sensor[J].Journal ofLightwave Technology 0733-8724(c)).
The current sensors capable of realizing weak acoustic wave detection mainly comprise: a fiber optic acoustic sensor (Balthasar fischer. Optical microphone hears ultrasound [ J ]. NATURE PHOTONICS,2016,10,356-358) for phase sensitive measurements based on a micro fabry-perot (F-P) interferometer. The interferometer consists of a reflective stop and a reflective tip of a single mode fiber tens of microns away from it. The vibration of the diaphragm adjusts the length of the F-P cavity, thereby adjusting the frequency of cavity resonance. To measure this frequency modulation, the laser light is sent through an optical fiber to the F-P cavity, reflected by the F-P cavity and detected. The frequency modulation is then converted into optical power modulation of the reflected laser signal at the vibration frequency, and the optical power signal is detected by the light intensity detector, thereby realizing weak acoustic wave detection. The method has high sensitivity, low noise and small volume, and can effectively detect the frequency of 600-10kHzThe sound wave of the pressure is detected. Meanwhile, the measurement sensitivity has higher dependence on wavelength, the frequency spectrum range is smaller, and complex circuit design is needed, so that the wide application and maintenance are not facilitated.
Disclosure of Invention
The invention aims to solve the technical problems that: the acoustic wave measuring device based on the Y-shaped cavity orthogonal polarization laser has the advantages of being simple in structure, wide in spectrum measuring range, high in sensitivity, strong in practicability, wide in application range and the like.
The principle of the invention is as follows: the gas guide pipe is used to connect the gas bellows and the cavity (capillary) of the P sub-section of the Y-cavity cross polarization laser to form a closed cavity, and the sensing gas is placed in the closed cavity. When an external acoustic signal to be measured propagates to the gas bellows, the diaphragm of the gas bellows vibrates, so that the refractive indexes of sensing gas in the cavities of the gas bellows, the gas conduit and the P subsections are changed, the P light frequency of the Y-cavity orthogonal polarization laser is changed, and the S light frequency is kept unchanged. Therefore, the frequency spectrum and intensity information of the sound wave signal can be obtained by measuring the frequency difference variation of the S light and the P light of the Y-cavity orthogonal polarization laser.
The technical scheme adopted by the invention is as follows: an acoustic wave measuring device based on a Y-cavity orthogonal polarization laser comprises a Y-cavity orthogonal polarization laser 100, a gas bellows 200, a gas conduit 300, a sensing gas 400 and a signal acquisition and processing unit 500; the Y-cavity orthogonal polarization laser 100 comprises a laser cavity, a polarization beam splitter 104, a first reflecting mirror 105, a second reflecting mirror 106 and a third reflecting mirror 107; the laser cavity comprises a shared section 101, an S sub-section 102 and a P sub-section 103, wherein the shared section 101 and the S sub-section 102 are integrally processed by adopting microcrystalline glass and a drilling process and share one end face; the polarization beam splitter 104 is fixedly arranged on the shared end face; the first end face of the P sub-section 103 is fixedly connected with the shared end face of the shared section 101 and the shared end face of the S sub-section 102 after the polarization beam splitter is arranged in a sealing manner; the center of the P subsection 103 is provided with a closed cavity 108 along the light path direction, and the cavity 108 is provided with a first vent hole 109; the first reflecting mirror 105 is fixedly arranged on the first end face of the common section 101, the second reflecting mirror 106 is fixedly arranged on the first end face of the S sub-section 102, and the third reflecting mirror 107 is fixedly arranged on the second end face of the P sub-section 103; the gas capsule 200 comprises a diaphragm 201 and a capsule cavity 202, wherein the capsule cavity 202 is a semi-closed cavity with an opening end face, a second vent hole 203 is arranged, and the diaphragm 201 is fixed on the opening end face of the capsule cavity 202 in a sealing way; the gas conduit 300 has stable physical properties, two ends of the gas conduit are respectively connected with the first vent hole 109 and the second vent hole 203 in a sealing way, and are communicated with the cavity 108 of the P subsection 103 and the gas bellows 200 to form a closed cavity, and the sensing gas 400 has stable chemical properties and is placed in the closed cavity; the signal collection and processing unit 500 is configured to collect and process the frequency difference signal output by the first reflecting mirror 105, and obtain a frequency spectrum and an intensity signal of the acoustic wave to be measured.
Further, the gas conduit 300 employs a hollow core optical fiber.
Further, the membrane 201 is an ultrathin quartz membrane, and the thickness of the ultrathin quartz membrane is less than 0.1mm.
Further, the bellows cavity 202 is a cylindrical cavity, the top surface is open, and a second vent hole 203 is disposed at the center of the bottom surface.
Still further, the signal collecting and processing unit 500 includes a 1/4 wave plate 501, a photodiode 502, a spectrometer 503 and a computer 504, the laser light of two frequencies output by the Y-cavity orthogonal polarization laser 100 through the first mirror 105 is vertically incident to the 1/4 wave plate 501, the laser light passing through the 1/4 wave plate 501 is received by the photodiode 502, the signal output by the photodiode 502 is received by the spectrometer 503, and the computer 504 reads and processes the output signal of the spectrometer 503.
The beneficial effects of the invention are as follows:
1. The output signal of the first reflecting mirror is the frequency difference signal of the S light and the P light, can be directly read out by a frequency counter and a frequency spectrograph, is convenient for later data processing, and can be used for real-time monitoring of sound waves.
2. The invention will change the laser frequency by 574MHz when the refractive index of the gas is changed by 1 x 10 -6. Therefore, the frequency difference variation deltav of the S light and the P light can be measured in real time, the frequency spectrum and the intensity signal of the sound wave can be sensitively detected, and the scale factor is large.
3. The invention can effectively detect the sound wave signal by utilizing the sensitive sound wave sensing capability of the ultrathin quartz membrane and the amplification effect of the laser frequency on the gas refractive index, and has the advantages of simple structure, strong environmental adaptability, wide detection range, high sensitivity and the like.
In addition, the invention is not limited to the types and the air pressures of the sensing gases, and the sensing gases of different types and air pressures can be replaced according to actual conditions so as to change the measurement sensitivity; the type of the gas conduit is not limited, and the hollow adapter connecting the gas conduit and the gas bellows is stable in physical performance and does not influence the change of the refractive index of the gas; nor is it limited by the diameter and type of membrane, and the application and application range are very wide.
Drawings
FIG. 1 is a schematic diagram of the overall structure of the present invention;
FIG. 2 is a schematic diagram of a Y-cavity orthogonal polarization laser according to the present invention;
Fig. 3 is a cross-sectional view of a gas capsule according to the present invention.
Detailed Description
An embodiment of the present invention will be described in detail with reference to the accompanying drawings, but the scope of the present invention should not be limited thereto.
As shown in fig. 1, an acoustic wave measuring device based on a Y-cavity orthogonal polarization laser comprises a Y-cavity orthogonal polarization laser 100, a gas bellows 200, a gas conduit 300, a sensing gas 400 and a signal acquisition and processing unit 500; as shown in fig. 2, the Y-cavity orthogonal polarization laser 100 includes a laser cavity, a polarization splitter 104, a first mirror 105, a second mirror 106, and a third mirror 107; the laser cavity comprises a shared section 101, an S sub-section 102 and a P sub-section 103, wherein the shared section 101 and the S sub-section 102 are integrally processed by adopting microcrystalline glass and a drilling process and share one end face; the polarization beam splitter 104 is fixedly arranged on the shared end face; the first end face of the P sub-section 103 is fixedly connected with the shared end face of the shared section 101 and the shared end face of the S sub-section 102 after the polarization beam splitter is arranged in a sealing manner; the center of the P subsection 103 is provided with a closed cavity 108 along the light path direction, and the cavity 108 is provided with a first vent hole 109; the first reflecting mirror 105 is fixedly arranged on the first end face of the common section 101, the second reflecting mirror 106 is fixedly arranged on the first end face of the S sub-section 102, and the third reflecting mirror 107 is fixedly arranged on the second end face of the P sub-section 103; as shown in fig. 3, the gas bellows 200 includes a diaphragm 201 and a bellows cavity 202, where the bellows cavity 202 is a semi-closed cavity with an open end surface, and is provided with a second vent hole 203, and the diaphragm 201 is fixed on the open end surface of the bellows cavity 202 in a sealing manner; the gas conduit 300 has stable physical properties, two ends of the gas conduit are respectively connected with the first vent hole 109 and the second vent hole 203 in a sealing way, and are communicated with the cavity 108 of the P subsection 103 and the gas bellows 200 to form a closed cavity, and the sensing gas 400 has stable chemical properties and is placed in the closed cavity; the signal collection and processing unit 500 is configured to collect and process the frequency difference signal output by the first reflecting mirror 105, and obtain a frequency spectrum and an intensity signal of the acoustic wave to be measured.
Preferably, as shown in fig. 1, the gas conduit 300 employs a hollow fiber, and the membrane 201 employs an ultra-thin quartz membrane having a thickness of 0.07mm; the diaphragm box cavity 202 is a cylindrical cavity and is formed by integrally cutting microcrystalline glass, the top surface of the diaphragm box cavity is open, a second vent hole 203 is formed in the center of the bottom surface of the diaphragm box cavity, and the ultrathin quartz diaphragm, the diaphragm box cavity and the hollow optical fiber are connected in an optical cement and adhesion mode; the signal collection and processing unit 500 includes a 1/4 wave plate 501, a photodiode 502, a spectrometer 503 and a computer 504, the laser light with two frequencies output by the Y-cavity orthogonal polarization laser 100 through the first mirror 105 is vertically incident to the 1/4 wave plate 501, the laser light passing through the 1/4 wave plate 501 is received by the photodiode 502, the signal output by the photodiode 502 is received by the spectrometer 503, and the computer 504 reads and processes the output signal of the spectrometer 503.
The Y-cavity orthogonal polarization laser 100 generates two different frequencies of S-light and P-light, the frequencies of which are respectively
Wherein v S、vP is the laser frequency of S light and P light respectively, q is a positive integer, and is determined by the laser itself, c is the speed of light, n S、nP is the refractive index of the gas in the S light and P light resonant cavities respectively, and L S、LP is the cavity length of the S light and P light resonant cavities respectively.
Therefore, the frequency difference between the S light and the P light
Δv＝vS-vP (3)
As can be seen from the above formula, when the refractive index of the gas in the cavity of the P sub-segment is changed by 1× -6, the laser frequency is changed by 574MHz, and in the existing measuring circuit, the frequency above 0.01Hz can be measured, so that the frequency difference change amount Deltav of the S light and the P light can be measured in real time to sensitively detect the sound wave signal.
Further, if the refractive index of the gas in the P sub-section cavity, the gas capsule and the hollow fiber is changed, this corresponds to changing the sensitivity of the acoustic detection. The higher the refractive index of the gas is, the higher the sensitivity of sound wave detection is, and the method is suitable for weak sound wave measurement scenes such as petroleum and natural gas exploration, underwater communication, seismic monitoring and the like; the lower the refractive index of the gas is, the lower the vibration of the ultrathin quartz membrane is, so that the ultrathin quartz membrane can not only effectively detect the acoustic wave signal in the high-intensity acoustic wave detection, but also avoid damaging the sensing device.
Claims (5)
1. An acoustic wave measuring device based on Y die cavity orthogonal polarization laser, which is characterized in that: the device comprises a Y-cavity orthogonal polarization laser (100), a gas bellows (200), a gas conduit (300), sensing gas (400) and a signal acquisition and processing unit (500);
the Y-cavity cross polarization laser (100) comprises a laser cavity, a polarization beam splitter (104), a first reflecting mirror (105), a second reflecting mirror (106) and a third reflecting mirror (107); the laser cavity comprises a shared section (101), an S sub-section (102) and a P sub-section (103), wherein the shared section (101) and the S sub-section (102) are integrally processed by adopting microcrystalline glass and a drilling process and share one end face; the polarization beam splitter (104) is fixedly arranged on the shared end face; the first end face of the P sub-section (103) is fixedly connected with the shared end face of the shared section (101) and the shared end face of the S sub-section (102) after the polarization beam splitter is arranged in a sealing mode; the center of the P subsection (103) is provided with a closed cavity (108) along the light path direction, and the cavity (108) is provided with a first vent hole (109); the first reflecting mirror (105) is fixedly arranged on the first end face of the common section (101), the second reflecting mirror (106) is fixedly arranged on the first end face of the S sub-section (102), and the third reflecting mirror (107) is fixedly arranged on the second end face of the P sub-section (103);
The gas capsule (200) comprises a diaphragm (201) and a capsule cavity (202), wherein the capsule cavity (202) is a semi-closed cavity with an opening at the end surface, a second ventilation hole (203) is arranged, and the diaphragm (201) is fixed on the opening end surface of the capsule cavity (202) in a sealing way;
the gas conduit (300) has stable physical performance, two ends of the gas conduit are respectively connected with the first vent hole (109) and the second vent hole (203) in a sealing way, the gas conduit is communicated with the cavity (108) of the P subsection (103) and the gas bellows (200) to form a closed cavity, and the sensing gas (400) has stable chemical performance and is placed in the closed cavity;
The signal acquisition and processing unit (500) is used for acquiring and processing the frequency difference signal output by the first reflecting mirror (105) to obtain the frequency spectrum and intensity signal of the sound wave to be detected.
2. The Y-cavity orthogonal polarization laser-based acoustic wave measurement device according to claim 1, wherein: the gas conduit (300) employs hollow core optical fibers.
3. The Y-cavity orthogonal polarization laser-based acoustic wave measurement device according to claim 1, wherein: the membrane (201) is an ultrathin quartz membrane, and the thickness of the ultrathin quartz membrane is smaller than 0.1mm.
4. A Y-cavity orthogonal polarized laser based acoustic wave measurement device according to any one of claims 1-3, wherein: the capsule cavity (202) is a cylindrical cavity, the top surface is open, and a second vent hole (203) is arranged in the center of the bottom surface.
5. The Y-cavity orthogonal polarization laser based acoustic wave measurement device according to claim 4, wherein: the signal acquisition and processing unit (500) comprises a 1/4 wave plate (501), a photoelectric avalanche diode (502), a frequency spectrograph (503) and a computer (504), wherein the Y-cavity orthogonal polarization laser (100) vertically irradiates the 1/4 wave plate (501) through two frequencies of lasers output by the first reflecting mirror (105), the lasers passing through the 1/4 wave plate (501) are received by the photoelectric avalanche diode (502), signals output by the photoelectric avalanche diode (502) are received by the frequency spectrograph (503), and the computer (504) reads and processes output signals of the frequency spectrograph (503).
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| EP1113250B1 (en) * | 2000-11-17 | 2003-02-05 | Agilent Technologies, Inc. (a Delaware corporation) | Method and apparatus for determining the polarisation mode dispersion of an optical device |
| AU2009356476C1 (en) * | 2009-12-11 | 2014-11-06 | Abb Power Grids Switzerland Ag | Fiber-optic current sensing using a sensor with exchangeable sub-modules |
| CN102507054A (en) * | 2011-11-02 | 2012-06-20 | 中国人民解放军国防科学技术大学 | Y-shaped cavity orthogonal polarization laser-based force and mass measurement method and device |
| CN102506728B (en) * | 2011-11-02 | 2013-09-25 | 中国人民解放军国防科学技术大学 | Device for measuring displacement based on Y-type cavity orthogonal polarization laser |
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| Frequency difference stabilization in Y-shaped cavity dual-frequency laser with the aid of precision passive control;xiaofei zeng，Guangzong Xiao;《optical Engineering》;20210318;全文 * |
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