Acoustic wave measurement device and method based on optical fiber differential

Abstract

The present invention belongs to the field of optical measurement technology, and specifically relates to an acoustic wave measurement device and method based on optical fiber differential, comprising a laser, an optical module, an optical path multiplexing module, a second polarization combiner, a receiving module, and a negative feedback module. By utilizing the reflection and transmission characteristics of the resonant cavity structure, the reflected laser and the transmitted laser are simultaneously output to form a differential pair, thereby eliminating external interference during the optical path transmission process, and the laser output optical power can be increased by the reflected laser, thereby increasing the acoustic wave detection sensitivity and improving the measurement accuracy; by adopting an optical fiber optical path, the anti-interference ability of the device can be improved; at the same time, by setting up an optical path multiplexing module, the round-trip multiplexing of two optical paths can be achieved simultaneously, thereby miniaturizing the device. By setting up a negative feedback module, the resonant cavity is compensated in real time, thereby making the resonant cavity constantly at the working point, maintaining the sensitivity unchanged, and avoiding the sensitivity drop caused by external environmental interference.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical measurement, and in particular relates to an acoustic wave measurement device and method based on optical fiber differential. Background Art

[0002] In the field of acoustic wave measurement, optical acoustic wave measurement devices occupy an important position due to their unique advantages. They are mainly divided into two categories: diaphragm type and air cavity type. Optical diaphragm acoustic wave measurement devices realize acoustic wave sensing based on the principle of light detection of diaphragm deformation. However, due to the limitation of the diaphragm's own resonant frequency, their operating frequency band is limited to the low frequency range. Air cavity acoustic wave measurement devices use light to measure changes in the refractive index of air to sense sound waves, breaking away from the limitation of the mechanical diaphragm resonant frequency and thus possessing high-frequency ultrasonic measurement capabilities. To improve the sensitivity of air cavity acoustic wave measurement devices, the method of making light resonate multiple times in the resonant cavity is usually adopted, combined with optical interferometry high-precision measurement technology, to achieve high-precision acoustic wave sensing.

[0003] Optical interferometry measurement technology covers various types, including intensity demodulation and phase demodulation. Among them, intensity demodulation has a much higher sensitivity than other demodulation technologies and is mostly suitable for measuring the refractive index of air in a resonant cavity. During the intensity demodulation process, when the central wavelength of the light is at the operating point of the resonant cavity, the demodulation sensitivity is maximum. However, in actual applications, the resonant cavity operating point is easily affected by external environmental interference and changes in real time, which in turn causes fluctuations in the system sensitivity. Although most current solutions use negative feedback to adjust the central wavelength of the laser to be consistent with the operating point, the mode and linewidth are prone to jitter during laser adjustment, and ultra-narrow linewidth frequency adjustment is difficult. In addition, laser phase noise will couple into the intensity, increasing system noise and affecting measurement accuracy. At the same time, light is easily interfered with by electromagnetic, vibration, temperature and other factors in the external environment during transmission, introducing additional noise, interfering with the original characteristics of the optical signal, causing subsequent demodulation analysis results to deviate from the true value, and reducing measurement reliability. In addition, using reflected light and transmitted light sensing each has its disadvantages. Reflected light is biased, which increases the detector's saturation light power requirement and increases design cost and difficulty. Transmitted light needs to be received on the other side of the resonant cavity, which increases the size of the device. At the same time, the sensitivity of the device is affected by both the fineness of the resonant cavity and the input light power. When the fineness is insufficient, increasing the input light power can improve the sensitivity, but it will aggravate the reflected light bias and easily cause the detector to saturate. Summary of the Invention

[0004] The present invention provides an acoustic wave measurement device and method based on optical fiber differential. By utilizing the reflection and transmission characteristics of a resonant cavity structure, a reflected laser and a transmitted laser are simultaneously output to form a differential pair, thereby eliminating external interference during optical transmission. The reflected laser can increase the output optical power of the laser, thereby increasing the acoustic wave detection sensitivity and improving the measurement accuracy. By adopting an optical fiber optical path, the anti-interference ability of the device can be improved. At the same time, by providing an optical path multiplexing module, the round-trip multiplexing of two optical paths can be achieved simultaneously, thereby achieving miniaturization of the device.

[0005] An acoustic wave measuring device based on optical fiber differential, comprising:

[0006] a laser for emitting polarized laser light;

[0007] an optical module connected to the laser and configured to optically process the laser light emitted by the laser;

[0008] An optical path multiplexing module connected to an optical module; the optical path multiplexing module includes an optical circulator, a first polarization beam combiner, a polarization beam splitter, a collimator, a resonant cavity structure, a quarter-wave plate, and a total reflector arranged in sequence; the optical circulator, the first polarization beam combiner, the polarization beam splitter, the collimator, and the resonant cavity structure form a semi-multiplexed optical path for returning the reflected laser reflected by the resonant cavity structure to the optical circulator along the original path; the optical circulator, the first polarization beam combiner, the polarization beam splitter, the collimator, the resonant cavity structure, the quarter-wave plate, and the total reflector form a fully multiplexed optical path for changing the polarization state of the transmitted laser transmitted through the resonant cavity structure through the quarter-wave plate, and reflecting the laser back to the optical circulator through the total reflector;

[0009] a second polarization beam combiner, connected to the optical circulator, for receiving the reflected laser light passing through the semi-multiplexed optical path and the transmitted laser light passing through the fully-multiplexed optical path;

[0010] A receiving module comprising a first receiving branch and a second receiving branch; the first receiving branch receives the reflected laser coupled by the second polarization beam combiner; and the second receiving branch receives the transmitted laser coupled by the second polarization beam combiner;

[0011] The laser, the optical module, and the optical path multiplexing module are coaxially arranged horizontally; the optical circulator, the second polarization beam combiner, and the receiving module are coaxially arranged vertically.

[0012] By utilizing the reflection and transmission characteristics of the resonant cavity structure, the reflected laser and the transmitted laser are output simultaneously to form a differential pair, thereby eliminating external interference in the optical transmission process. The reflected laser can also increase the laser output optical power, thereby increasing the sensitivity of acoustic wave detection and improving measurement accuracy. By adopting an optical fiber optical path, the anti-interference ability of the device can be improved. At the same time, by setting up an optical path multiplexing module, the round-trip multiplexing of the two optical paths can be realized simultaneously, thereby realizing the miniaturization of the device.

[0013] Furthermore, the laser is a narrow-linewidth polarization-maintaining laser, which is used to emit linearly polarized laser light.

[0014] By using an ultra-narrow linewidth polarization-maintaining laser as the laser light source, the device noise can be significantly reduced, enabling high-precision acoustic wave measurement.

[0015] Furthermore, the optical module includes an optical amplifier, which is used to amplify the power of the laser emitted by the laser.

[0016] By setting up an optical amplifier, the power of the emitted laser can be amplified, thereby providing sufficient energy for the effective transmission and interaction of the optical signal in the resonant cavity structure.

[0017] Furthermore, the optical circulator includes a first port, a second port and a third port, and is configured to transmit the laser light received by the first port to the second port, and transmit the laser light received by the second port to the third port.

[0018] By setting different ports of the optical circulator, the unidirectional transmission and branching functions of the optical signal can be realized, avoiding crosstalk and reflection interference of the optical signal.

[0019] Furthermore, the first polarization beam combiner includes a fourth port, a fifth port, and a sixth port, and is configured to transmit the laser light received by the sixth port to the fourth port or the fifth port, and transmit the laser light from the fourth port and the fifth port to the sixth port;

[0020] The polarization beam splitter comprises a seventh port, an eighth port, and a ninth port, and is configured to transmit the laser light received by the seventh port and the eighth port to the ninth port, and transmit the laser light received by the ninth port to the seventh port or the eighth port;

[0021] The sixth port is connected to the second port of the optical circulator; the fifth port is connected to the seventh port; the sixth port is connected to the eighth port; and the ninth port is connected to the collimator.

[0022] Polarization beam combiners and polarization beam splitters are used to realize polarization splitting and coupling of lasers with different polarization states, thereby achieving efficient transmission and direction control of optical signals.

[0023] Furthermore, the second polarization combiner includes a tenth port, an eleventh port, and a twelfth port; the twelfth port is connected to the third port of the optical circulator; the tenth port is connected to the first receiving branch; and the eleventh port is connected to the second receiving branch.

[0024] Furthermore, the optical path of the semi-multiplexed optical path includes: the optical circulator transmits the laser light with the first polarization state received at its first port to its second port, sequentially transmits the laser light to its fourth port through the sixth port of the first polarization beam combiner, transmits the laser light to its ninth port through the seventh port of the polarization beam splitter, collimates the laser light and then enters the resonant cavity structure, the resonant cavity structure reflects the input laser light with the first polarization state and then returns the laser light to the optical circulator along the original path;

[0025] The optical path of the fully multiplexed optical path includes: the optical circulator transmits the laser light with the first polarization state received by its first port to its second port, transmits it to its fourth port through the sixth port of the first polarization beam combiner, transmits it to its ninth port through the seventh port of the polarization beam splitter, and enters the resonant cavity structure after collimation by the collimator. The resonant cavity structure transmits the input laser light with the first polarization state, changes the polarization state through a 1 / 4 wave plate, and returns to the polarization beam splitter along the original path after reflection through a total reflection mirror. It is transmitted to the eighth port through the ninth port of the polarization beam splitter, and transmitted to the sixth port through the fifth port of the first polarization beam combiner, and then returns the transmitted laser light with the second polarization state to the optical circulator.

[0026] The optical path of the semi-multiplexed optical path is used to realize the optical path backtracking of the laser reflected by the resonant cavity; the polarization state change and optical path transmission of the laser transmitted by the resonant cavity are realized through the optical path of the fully multiplexed optical path.

[0027] Furthermore, the resonant cavity structure includes two partial reflection mirrors for reflecting and transmitting the input laser.

[0028] Furthermore, a negative feedback module is also included; the negative feedback module includes:

[0029] a photoelectric detector connected to the receiving module and configured to convert the reflected laser and transmitted laser signals fed back by the receiving module into voltage signals;

[0030] a displacement adjustment structure connected to the resonant cavity structure;

[0031] A negative feedback system is connected to the photoelectric detector and the displacement adjustment structure, and is used to drive the displacement adjustment structure compensation resonant cavity through the voltage signal converted by the photoelectric detector.

[0032] By setting up a negative feedback module, the resonant cavity is compensated in real time, so that the resonant cavity is constantly at the working point, maintaining the sensitivity unchanged, and avoiding the decrease in sensitivity caused by external environmental interference.

[0033] A method for an acoustic wave measuring device based on optical fiber differential, comprising:

[0034] The laser emits laser light having a first polarization state;

[0035] The first receiving branch of the receiving module receives the reflected laser light having a first polarization state, and feeds the reflected laser light back to the photodetector to convert the reflected laser light into a first voltage signal; the second receiving branch of the receiving module receives the transmitted laser light having a second polarization state, and feeds the reflected laser light back to the photodetector to convert the reflected laser light into a second voltage signal;

[0036] The negative feedback system drives the displacement adjustment structure to compensate the resonant cavity in real time according to the differential pair formed by the first voltage signal and the second voltage signal.

[0037] The beneficial effects of the present invention are:

[0038] The present invention utilizes the reflection and transmission properties of the resonant cavity structure to simultaneously output reflected laser light and transmitted laser light to form a differential pair, thereby eliminating external interference during optical transmission. The reflected laser light can also increase the laser output optical power, thereby increasing acoustic wave detection sensitivity and improving measurement accuracy. The use of fiber optic optical paths can improve the device's anti-interference capability. Simultaneously, by providing an optical path multiplexing module, two optical paths can be simultaneously multiplexed, thereby miniaturizing the device. A negative feedback module is provided to compensate the resonant cavity in real time, thereby maintaining the resonant cavity at a constant operating point, maintaining sensitivity, and avoiding sensitivity drops caused by external environmental interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural schematic diagram of the present invention;

[0040] Figure 2 Schematic diagram of the transmission and reflection spectra of the resonant cavity;

[0041] Figure 3 Flowchart of the negative feedback module operation.

[0042] Reference numerals:

[0043] 1. Laser; 2. Optical amplifier; 3. Optical circulator; 31. First port; 32. Second port; 33. Third port; 4. First polarization beam combiner; 41. Fourth port; 42. Fifth port; 43. Sixth port; 5. Second polarization beam combiner; 51. Tenth port; 52. Eleventh port; 53. Twelfth port; 6. Polarization beam splitter; 61. Seventh port; 62. Eighth port; 63. Ninth port; 7. Collimator; 8. Resonant cavity structure; 9. Quarter-wave plate; 10. Totally reflective mirror; 11. Receiving module; 111. First receiving branch; 112. Second receiving branch; 12. Displacement adjustment structure; 13. Negative feedback system. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement an apparatus and / or practice a method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this apparatus and / or practice this method.

[0046] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood in specific situations.

[0047] Example 1

[0048] Figure 1The device is a fiber-optic differential-based acoustic wave measurement device, comprising a laser 1, an optical module, an optical path multiplexing module, a second polarization combiner 5, a receiving module 11, and a negative feedback module. By utilizing the reflection and transmission characteristics of the resonant cavity structure 8, reflected laser light and transmitted laser light are simultaneously output to form a differential pair, thereby eliminating external interference during optical transmission. The reflected laser light can also increase the laser output optical power, thereby increasing acoustic wave detection sensitivity and improving measurement accuracy. The use of an optical fiber optical path improves the device's anti-interference capability. Simultaneously, by providing an optical path multiplexing module, two optical paths can be multiplexed simultaneously, thereby miniaturizing the device. By providing a negative feedback module, the resonant cavity is compensated in real time, thereby maintaining a constant operating point, maintaining sensitivity, and avoiding sensitivity degradation caused by external environmental interference.

[0049] Specifically, a laser 1 is used to emit polarization state laser light.

[0050] In this embodiment, the laser 1 is a narrow-linewidth polarization-maintaining laser, which is used to emit linearly polarized laser light. By using an ultra-narrow-linewidth polarization-maintaining laser as the laser light source, the device noise can be significantly reduced, achieving high-precision acoustic wave measurement.

[0051] Specifically, the optical module is connected to the laser 1 and is used to optically process the laser emitted by the laser 1 .

[0052] In this embodiment, the optical module includes an optical amplifier 2, which is used to amplify the power of the laser light emitted by the laser. By providing the optical amplifier 2, the power of the emitted laser light can be amplified, thereby providing sufficient energy for the effective transmission and interaction of the optical signal in the resonant cavity structure 8.

[0053] Specifically, the optical path multiplexing module is connected to the optical module; the optical path multiplexing module includes an optical circulator 3, a first polarization combiner 4, a polarization beam splitter 6, a collimator 7, a resonant cavity structure 8, a 1 / 4 wave plate 9, and a total reflective mirror 10 arranged in sequence.

[0054] The optical circulator (OC) 3 includes a first port 31, a second port 32, and a third port 33. It is used to transmit laser light received at the first port 31 to the second port 32, and transmit laser light received at the second port 32 to the third port 33. By configuring the different ports of the optical circulator 3, unidirectional transmission and branching of optical signals can be achieved, avoiding crosstalk and reflection interference of the optical signals.

[0055] The first polarization beam combiner (PBC1) 4 includes a fourth port 41, a fifth port 42, and a sixth port 43, and is configured to transmit the laser light received by the sixth port 43 to the fourth port 41 or the fifth port 42, and transmit the laser light from the fourth port 41 and the fifth port 42 to the sixth port 43;

[0056] The polarization beam splitter (PBS) 6 includes a seventh port 61, an eighth port 62, and a ninth port 63, and is configured to transmit the laser light received by the seventh port 61 and the eighth port 62 to the ninth port 63, and transmit the laser light received by the ninth port 63 to the seventh port 61 or the eighth port 62;

[0057] In this embodiment, the sixth port 43 is connected to the second port 32 of the optical circulator 3; the fifth port 42 is connected to the seventh port 61; the sixth port 43 is connected to the eighth port 62; and the ninth port 63 is connected to the collimator 7. The first polarization beam combiner 4 and the polarization beam splitter 6 achieve polarization splitting and coupling of laser beams of different polarization states, thereby achieving efficient transmission and directional control of optical signals.

[0058] The resonant cavity structure 8 includes two partial reflection mirrors for reflecting and transmitting the input laser light.

[0059] In this embodiment, the expression for the intensity of the laser light reflected from the resonant cavity is:

[0060] ;

[0061] Where, Indicates the intensity of laser light reflected from the resonant cavity; represents the reflectivity of the two partial reflective mirror surfaces in the resonant cavity structure 8; represents the optical path difference in the resonant cavity, and its expression is: , represents the wavelength of light in a vacuum, represents the optical path difference, represents the thickness of the FP interferometer, represents the refractive index inside the interferometer, represents the refraction angle of light in the thin plate; represents the incident light intensity in the resonant cavity structure 8;

[0062] The expression of the laser intensity transmitted by the resonant cavity is:

[0063] ;

[0064] Where, It represents the intensity of laser light transmitted through the resonant cavity;

[0065] Figure 2The figure shows the transmission spectrum and reflection spectrum of the resonant cavity. It can be seen that the slopes of the transmission spectrum and the reflection spectrum of the resonant cavity are opposite. The intersection of the transmission spectrum curve and the reflection spectrum curve is set as the working point. When the wavelength changes due to the sound wave, the phase of the transmitted light and the reflected light in the resonant cavity will be differential signal.

[0066] In this embodiment, the optical circulator 3, the first polarization beam combiner 4, the polarization beam splitter 6, the collimator 7, and the resonant cavity structure 8 form a semi-multiplexed optical path for returning the reflected laser light from the resonant cavity structure 8 back to the optical circulator 3 along its original path. The optical path of the semi-multiplexed optical path includes: the optical circulator 3 transmits the laser light with a first polarization state received at its first port 31 to its second port 32, which then passes through the sixth port 43 of the first polarization beam combiner 4 to its fourth port 41, and then through the seventh port 61 of the polarization beam splitter 6 to its ninth port 63. After collimation by the collimator 7, the laser light enters the resonant cavity structure 8. The resonant cavity structure 8 reflects the input laser light with the first polarization state and then returns it to the optical circulator 3 along its original path. Through the semi-multiplexed optical path, the optical path of the laser light reflected from the resonant cavity is traced back.

[0067] In this embodiment, the optical circulator 3, the first polarization combiner 4, the polarization beam splitter 6, the collimator 7, the resonant cavity structure 8, the 1 / 4 wave plate 9, and the total reflection mirror 10 form a fully multiplexed optical path, which is used to change the polarization state of the transmitted laser transmitted through the resonant cavity structure 8 through the 1 / 4 wave plate 9 and reflect it back to the optical circulator 3 through the total reflection mirror 10. The optical path of the fully multiplexed optical path includes: the optical circulator 3 transmits the laser light with a first polarization state received at its first port 31 to its second port 32, which is then transmitted to its fourth port 41 through the sixth port 43 of the first polarization beam combiner 4, and to its ninth port 63 through the seventh port 61 of the polarization beam splitter 6. After being collimated by the collimator 7, the laser light enters the resonant cavity structure 8. The resonant cavity structure 8 transmits the input laser light with the first polarization state, changes its polarization state through the quarter-wave plate 9, and is reflected by the total reflection mirror 10 before returning to the polarization beam splitter 6 along the original path. The laser light is then transmitted to the eighth port 62 through the ninth port 63 of the polarization beam splitter 6, and to the sixth port 43 through the fifth port 42 of the first polarization beam combiner 4, and then returns the transmitted laser light with a second polarization state to the optical circulator 3. Through the optical path of the fully multiplexed optical path, the polarization state change of the laser light transmitted through the resonant cavity and the optical path transmission are achieved.

[0068] Specifically, the second polarization beam combiner (PBC2) 5 is connected to the optical circulator 3; the second polarization beam combiner 5 includes a tenth port 51, an eleventh port 52, and a twelfth port 53; the twelfth port 53 is connected to the third port 33 of the optical circulator 3; the tenth port 51 is connected to the first receiving branch 111; the eleventh port 52 is connected to the second receiving branch 112, and is used to receive the reflected laser light through the semi-multiplexed optical path and the transmitted laser light through the fully multiplexed optical path.

[0069] Specifically, the receiving module 11 includes a first receiving branch (PIN1) 111 and a second receiving branch (PIN2) 112; the first receiving branch 111 receives the reflected laser coupled by the second polarization beam combiner 5; the second receiving branch 112 receives the transmitted laser coupled by the second polarization beam combiner 5;

[0070] In this embodiment, the laser 1 , the optical module, and the optical path multiplexing module are coaxially arranged horizontally; the optical circulator 3 , the second polarization beam combiner 5 , and the receiving module 11 are coaxially arranged vertically.

[0071] Specifically, the negative feedback module includes:

[0072] A photodetector connected to the receiving module 11 and configured to convert the reflected laser and transmitted laser signals fed back by the receiving module 11 into voltage signals;

[0073] The displacement adjustment structure 12 is connected to the resonant cavity structure 8; the displacement adjustment structure 12 includes piezoelectric ceramics and PET.

[0074] The negative feedback system 13 is connected to the photodetector and the displacement adjustment structure 12 and is used to drive the displacement adjustment structure 12 to compensate the resonant cavity through the voltage signal converted by the photodetector.

[0075] In this embodiment, if Figure 3 As shown, when the resonant cavity working point changes due to interference from the external environment, the first voltage signal converted by the reflected laser and the second voltage signal converted by the transmitted laser obtained by the photodetector change, and the negative feedback system 13 calculates the light polarization voltage signal deviation value, and based on the relationship between the light polarization voltage signal deviation value and the resonant cavity working point, drives the displacement adjustment structure 12 to compensate the resonant cavity, so that the resonant cavity working point is continuously at the working point position, ensuring that the light polarization voltage signal deviation value is a constant value.

[0076] The relationship between the optical polarization voltage signal deviation value and the wavelength drift is:

[0077] ;

[0078] Where, Indicates the wavelength drift; represents the first proportionality coefficient, which depends on the slope of the resonant cavity transmission spectrum at the operating point; Indicates the optical polarization voltage signal deviation value;

[0079] The relationship between the change in the driving voltage of the displacement adjustment structure 12 and the change in the length of the resonant cavity is:

[0080] ;

[0081] Where, Indicates the change in driving voltage of the displacement adjustment structure 12; represents a second proportionality factor, which depends on the characteristics of the drive device;

[0082] The relationship between the resonant cavity optical path difference and the wavelength change is:

[0083] ;

[0084] Where, represents the third proportionality factor, which depends on the refractive index of air and the cavity length.

[0085] It should be noted that in actual application, the first proportional coefficient , the second proportional coefficient , the third proportional coefficient It can be obtained through experimental calibration.

[0086] Example 2

[0087] In this embodiment, a method for an acoustic wave measuring device based on optical fiber differential is provided, comprising:

[0088] Laser 1 emits laser light having a first polarization state;

[0089] The first receiving branch 111 of the receiving module 11 receives the reflected laser light having a first polarization state, and feeds it back to the photodetector to convert it into a first voltage signal. The second receiving branch 112 of the receiving module 11 receives the transmitted laser light having a second polarization state, and feeds it back to the photodetector to convert it into a second voltage signal.

[0090] The negative feedback system 13 drives the displacement adjustment structure 12 to compensate the resonant cavity in real time according to the differential pair formed by the first voltage signal and the second voltage signal.

[0091] In this embodiment, the working principle of the present invention is:

[0092] The laser 1 emits a laser with a first polarization state, and the optical amplifier 2 amplifies the power of the incident laser and transmits it to the first port 31 of the optical circulator 3;

[0093] The optical circulator 3 transmits the laser light with the first polarization state received at its first port 31 to its second port 32, and then transmits the laser light to its fourth port 41 through the sixth port 43 of the first polarization beam combiner 4, and to its ninth port 63 through the seventh port 61 of the polarization beam splitter 6. After being collimated by the collimator 7, the laser light enters the resonant cavity structure 8. The resonant cavity structure 8 reflects the input laser light with the first polarization state and returns the reflected laser light to the second port 32 of the optical circulator 3 along the original path. The reflected laser light is then transmitted to the twelfth port 53 of the second polarization beam combiner 5 through the third port 33 of the optical circulator 3, and then transmitted to the first receiving branch 111 of the receiving module 11 through the tenth port 51, thereby obtaining the reflected laser light with the first polarization state. The reflected laser light is then fed back to the photodetector to obtain a corresponding first voltage signal.

[0094] The optical circulator 3 transmits the laser light with the first polarization state received by its first port 31 to its second port 32, and then transmits it to its fourth port 41 through the sixth port 43 of the first polarization beam combiner 4, transmits it to its ninth port 63 through the seventh port 61 of the polarization beam splitter 6, and enters the resonant cavity structure 8 after collimation by the collimator 7. The resonant cavity structure 8 transmits the input laser light with the first polarization state, changes the polarization state through the 1 / 4 wave plate 9, and reflects it through the total reflective mirror 10 and returns to the polarization beam splitter 6 along the original path, and then passes through the polarization beam splitter 6 in sequence. After being transmitted from the ninth port 63 of the polarization beam splitter 6 to the eighth port 62 and from the fifth port 42 of the first polarization beam combiner 4 to the sixth port 43, the transmitted laser light with the second polarization state is returned to the second port 32 of the optical circulator 3, and is sequentially transmitted through the third port 33 of the optical circulator 3 to the twelfth port 53 of the second polarization beam combiner 5, and then transmitted through the eleventh port 52 to the second receiving branch 112 of the receiving module 11, thereby obtaining the transmitted laser light with the second polarization state, and feeding it back to the photodetector to obtain a corresponding second voltage signal;

[0095] The negative feedback system 13 drives the displacement adjustment structure 12 to compensate the resonant cavity in real time according to the differential pair formed by the first voltage signal and the second voltage signal, so that the working point of the resonant cavity is continuously at the working point position, ensuring that the deviation value of the light polarization voltage signal is constant.

[0096] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0097] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. An acoustic wave measuring device based on optical fiber differential, characterized in that: include: a laser for emitting polarized laser light; an optical module connected to the laser and configured to optically process the laser light emitted by the laser; An optical path multiplexing module connected to an optical module; the optical path multiplexing module includes an optical circulator, a first polarization beam combiner, a polarization beam splitter, a collimator, a resonant cavity structure, a quarter-wave plate, and a total reflector arranged in sequence; the optical circulator, the first polarization beam combiner, the polarization beam splitter, the collimator, and the resonant cavity structure form a semi-multiplexed optical path for returning the reflected laser reflected by the resonant cavity structure to the optical circulator along the original path; the optical circulator, the first polarization beam combiner, the polarization beam splitter, the collimator, the resonant cavity structure, the quarter-wave plate, and the total reflector form a fully multiplexed optical path for changing the polarization state of the transmitted laser transmitted through the resonant cavity structure through the quarter-wave plate, and reflecting the laser back to the optical circulator through the total reflector; a second polarization beam combiner, connected to the optical circulator, for receiving the reflected laser light passing through the semi-multiplexed optical path and the transmitted laser light passing through the fully-multiplexed optical path; A receiving module comprising a first receiving branch and a second receiving branch; the first receiving branch receives the reflected laser coupled by the second polarization beam combiner; and the second receiving branch receives the transmitted laser coupled by the second polarization beam combiner; The laser, the optical module, and the optical path multiplexing module are coaxially arranged horizontally; the optical circulator, the second polarization beam combiner, and the receiving module are coaxially arranged vertically.

2. The acoustic wave measuring device based on optical fiber differential according to claim 1, characterized in that: The laser is a narrow-linewidth polarization-maintaining laser, and is used for emitting linearly polarized laser light.

3. The acoustic wave measuring device based on optical fiber differential according to claim 1, characterized in that: The optical module includes an optical amplifier, which is used to amplify the power of the laser emitted by the laser.

4. The acoustic wave measuring device based on optical fiber differential according to claim 1, characterized in that: The optical circulator comprises a first port, a second port and a third port, and is used to transmit the laser light received by the first port to the second port, and transmit the laser light received by the second port to the third port.

5. The acoustic wave measuring device based on optical fiber differential according to claim 4, characterized in that: The first polarization beam combiner comprises a fourth port, a fifth port, and a sixth port, and is configured to transmit the laser light received by the sixth port to the fourth port or the fifth port, and transmit the laser light from the fourth port and the fifth port to the sixth port; The polarization beam splitter comprises a seventh port, an eighth port, and a ninth port, and is configured to transmit the laser light received by the seventh port and the eighth port to the ninth port, and transmit the laser light received by the ninth port to the seventh port or the eighth port; The sixth port is connected to the second port of the optical circulator; the fifth port is connected to the seventh port; the sixth port is connected to the eighth port; and the ninth port is connected to the collimator.

6. The acoustic wave measuring device based on optical fiber differential according to claim 5, characterized in that: The second polarization beam combiner comprises a tenth port, an eleventh port, and a twelfth port; The twelfth port is connected to the third port of the optical circulator; the tenth port is connected to the first receiving branch; The eleventh port is connected to the second receiving branch.

7. The acoustic wave measuring device based on optical fiber differential according to claim 6, characterized in that: The optical path of the semi-multiplexed optical path includes: the optical circulator transmits the laser light with the first polarization state received at its first port to its second port, sequentially transmits the laser light to its fourth port through the sixth port of the first polarization beam combiner, transmits the laser light to its ninth port through the seventh port of the polarization beam splitter, collimates the laser light and then enters the resonant cavity structure, the resonant cavity structure reflects the input laser light with the first polarization state and then returns the laser light to the optical circulator along the original path; The optical path of the fully multiplexed optical path includes: the optical circulator transmits the laser light with the first polarization state received by its first port to its second port, transmits it to its fourth port through the sixth port of the first polarization beam combiner, transmits it to its ninth port through the seventh port of the polarization beam splitter, and enters the resonant cavity structure after collimation by the collimator. The resonant cavity structure transmits the input laser light with the first polarization state, changes the polarization state through a 1 / 4 wave plate, and returns to the polarization beam splitter along the original path after reflection through a total reflection mirror. It is transmitted to the eighth port through the ninth port of the polarization beam splitter, and transmitted to the sixth port through the fifth port of the first polarization beam combiner, and then returns the transmitted laser light with the second polarization state to the optical circulator.

8. The acoustic wave measuring device based on optical fiber differential according to claim 1, characterized in that: The resonant cavity structure includes two partial reflection mirrors and is used to reflect and transmit input laser light.

9. The acoustic wave measuring device based on optical fiber differential according to claim 1, characterized in that: Also includes a negative feedback module; the negative feedback module includes: a photoelectric detector connected to the receiving module and configured to convert the reflected laser and transmitted laser signals fed back by the receiving module into voltage signals; a displacement adjustment structure connected to the resonant cavity structure; A negative feedback system is connected to the photoelectric detector and the displacement adjustment structure, and is used to drive the displacement adjustment structure compensation resonant cavity through the voltage signal converted by the photoelectric detector.

10. A method for the acoustic wave measuring device based on optical fiber differential according to claim 9, characterized in that: include: The laser emits laser light having a first polarization state; The first receiving branch of the receiving module receives the reflected laser light having a first polarization state, and feeds the reflected laser light back to the photodetector to convert the reflected laser light into a first voltage signal; the second receiving branch of the receiving module receives the transmitted laser light having a second polarization state, and feeds the reflected laser light back to the photodetector to convert the reflected laser light into a second voltage signal; The negative feedback system drives the displacement adjustment structure to compensate the resonant cavity in real time according to the differential pair formed by the first voltage signal and the second voltage signal.

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