CN210833846U - Remote external modulation optical fiber interference vibration measuring device - Google Patents
Remote external modulation optical fiber interference vibration measuring device Download PDFInfo
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- CN210833846U CN210833846U CN201922220230.XU CN201922220230U CN210833846U CN 210833846 U CN210833846 U CN 210833846U CN 201922220230 U CN201922220230 U CN 201922220230U CN 210833846 U CN210833846 U CN 210833846U
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Abstract
The utility model discloses a remote external modulation optical fiber interference vibration measuring device, which comprises a laser emitting device, an optical fiber coupler, an optical fiber interferometer main body structure and a processing device, wherein optical fibers are used for connection between the laser emitting device and the optical fiber coupler, between the optical fiber interferometer main body structure and the optical fiber coupler and between the optical fiber coupler and the processing device; the optical fiber interferometer main body structure comprises a shell and a piezoelectric elastic sheet, wherein one end of the piezoelectric elastic sheet is fixed on the shell, the other end of the piezoelectric elastic sheet is suspended in the air, the shell is fixed on bedrock, and an optical fiber between the optical fiber interferometer main body structure and an optical fiber coupler is fixed on the piezoelectric elastic sheet; when the environmental vibration occurs, the shell drives the piezoelectric elastic sheet to vibrate to generate a modulation signal. The utility model discloses use passive outer modulation mode, realize the phase modulation of optical fiber interferometer major structure, can avoid the production of associated amplitude modulation.
Description
Technical Field
The utility model relates to an optical fiber interference vibration sensor field, it is specific, relate to a long-range external modulation optical fiber interference vibration measuring device.
Background
In order to realize physical quantity measurement in a severe environment and avoid the damage of the host of the sensing system caused by the severe environment, the host is placed in a safe place far away from a sensing probe, and the measurement method is called as remote measurement.
In the classical optical fiber interference technology, light waves need to be modulated, and the phase blanking phenomenon of interference light is eliminated. The optical wave modulation method comprises an inner modulation method and an outer modulation method. The internal modulation is that a single-frequency excitation signal is directly output to a laser as a light source, so that the laser outputs a light wave with wavelength (or frequency) modulation; the external modulation is to output the single-frequency excitation signal to a phase controller (such as a piezoelectric ceramic optical fiber stretcher or a lithium niobate phase modulator) in the reference arm of the fiber interferometer, so that the fiber length of the reference arm of the fiber interferometer follows the single-frequency excitation signal.
In the existing optical fiber interference vibration measurement device and method, in order to avoid the damage of the harsh environment of a vibration measurement site to a host, the advantages of small optical fiber attenuation and suitability for remote sensing are fully exerted, and a vibration probe and the host are often placed separately with a distance of dozens of kilometers. In general, the environment of a measurement field is severe and complex, and in order to exert the passive advantage of the optical fiber sensing probe, no power supply equipment is placed on the measurement field, and only an internal modulation mode can be adopted to realize the phase modulation of the optical fiber interferometer.
The inventor believes that when the wavelength or frequency modulation of the laser is achieved by internal modulation, additional amplitude modulation occurs, reducing the measurement accuracy of the system. In addition, the internal modulation causes the line width performance of the laser to be poor, the phase noise of the optical fiber interferometer is enhanced, and the measurement sensitivity of the system is reduced.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a long-range outer modulation optic fibre interference vibration measuring device and use the device carries out the method of measuring, and it uses outer modulation mode, realizes the phase modulation of optic fibre interferometer major structure, can avoid the production of associated amplitude modulation.
The utility model aims at providing a long-range external modulation optic fibre interference vibration measuring device.
In order to realize the purpose of the utility model, the utility model discloses a following technical scheme:
the utility model discloses a remote external modulation optical fiber interference vibration measuring device, which comprises,
the device comprises a laser emission device, an optical fiber coupler, an optical fiber interferometer main body structure and a processing device, wherein the laser emission device and the optical fiber coupler, the optical fiber interferometer main body structure and the optical fiber coupler, and the optical fiber coupler and the processing device are connected by optical fibers;
the optical fiber interferometer main body structure comprises a shell and a piezoelectric elastic sheet, wherein one end of the piezoelectric elastic sheet is fixed on the shell, the other end of the piezoelectric elastic sheet is suspended in the air, the shell is fixed on bedrock, and an optical fiber between the optical fiber interferometer main body structure and an optical fiber coupler is fixed on the piezoelectric elastic sheet; when the environmental vibration takes place, the casing drives the piezoelectric elastic piece to produce the vibration.
Further, the laser emitting device comprises a laser and an isolator, laser energy emitted by the laser can pass through the isolator, and the isolator is connected with the optical fiber coupler through an optical fiber.
Further, when the optical fiber coupler comprises one optical fiber coupler, the laser emission device, the optical fiber interferometer main body structure and the processing device are all connected to the same optical fiber coupler.
Further, the optical fiber coupler is provided with a first port, a second port, a third port and a fourth port, the first port of the optical fiber coupler is connected with the laser emission device through an optical fiber, and the second port of the optical fiber coupler is connected with the processing device through the optical fiber; the third port of the optical fiber coupler is connected with the sensing arm optical fiber, and the fourth port of the optical fiber coupler is connected with the reference arm optical fiber; the reference arm optical fiber is fixed on the piezoelectric elastic sheet.
Further, sensing arm optic fibre includes non-sensitive portion and sensitive portion, and non-sensitive portion optic fibre is used for the transmission medium of light signal, and sensitive portion optic fibre twines at the vibration probe, and the vibration probe is fixed in the basement rock in order to perceive the environmental vibration:
the reference arm optical fiber comprises a non-sensitive part and a sensitive part, the non-sensitive part optical fiber is used for a transmission medium of an optical signal, and the sensitive part optical fiber is fixed on the piezoelectric elastic sheet to realize the change of the length of the reference arm optical fiber.
Furthermore, the tail end of the sensing arm optical fiber is connected with a vibration probe, the tail end of the reference arm optical fiber and the tail end of the sensing arm optical fiber are provided with Faraday rotators, and light waves from the sensing arm optical fiber and the reference arm optical fiber can be reflected by the Faraday rotators.
Further, when the optical fiber coupler includes two optical fiber couplers, the optical fiber coupler includes a first optical fiber coupler and a second optical fiber coupler, the laser transmitter is connected with the first optical fiber coupler, the optical fiber interferometer main body structure is simultaneously connected with the first optical fiber coupler and the second optical fiber coupler, and the processing device is connected with the second optical fiber coupler.
Furthermore, the first optical fiber coupler is provided with a first port, a second port, a third port and a fourth port, the first port of the first optical fiber coupler is connected with the laser emission device through an optical fiber, the second port of the first optical fiber coupler is vacant, the third port of the first optical fiber coupler is connected with the sensing arm optical fiber, and the fourth port of the first optical fiber coupler is connected with the reference arm optical fiber;
the second optical fiber coupler is provided with a first port, a second port, a third port and a fourth port, the first port of the second optical fiber coupler is vacant, the second port of the second optical fiber coupler is connected with the processing device, the third port of the second optical fiber coupler is connected with the reference arm optical fiber, and the fourth port of the second optical fiber coupler is connected with the sensing arm optical fiber.
Furthermore, the processing device comprises a photoelectric detector, a narrow-band filter, a phase demodulation module, a frequency multiplier and a processor, wherein the photoelectric detector is electrically connected with the narrow-band filter and the phase demodulation module at the same time, the narrow-band filter is connected with the frequency multiplier and the phase demodulation module at the same time, the frequency multiplier is connected with the phase demodulation module, and the phase demodulation module is also connected with the processor.
Use the utility model discloses measure, include following step:
1) the laser outputs continuous light;
2) continuous light passes through the main structure of the optical fiber interferometer, and forms an interference optical signal at the output port of the optical fiber coupler:
3) the interference optical signal passes through a photoelectric detector, a narrow-band filter and a frequency multiplier to obtain an interference electric signal, a frequency multiplication signal 1 and a frequency multiplication signal 2;
4) demodulating the frequency-doubled signal 1, the frequency-doubled signal 2 and the interference electric signal to obtain a phase signal capable of reflecting the environmental vibration;
5) and calculating measurement data such as speed, acceleration, displacement and the like of the environmental vibration according to the phase signal and the response characteristic of the phase signal relative to the environmental vibration.
Compared with the prior art, the utility model discloses following beneficial effect has been obtained:
1) the utility model discloses an outer modulation mode realizes the phase modulation of optical fiber interferometer, can avoid the production of associated amplitude modulation, keeps the phase noise of laser instrument to be in lower level all the time, improves system measurement accuracy and sensitivity.
2) The utility model discloses in, the vibration probe who places at the measurement site has passive characteristics for the assurance, does not adopt the power supply of extra equipment, will place one section sensitive optic fibre of optical fiber interferometer reference arm at the measurement site and fix on the shell fragment of piezoelectric material preparation, and when the vibration took place, the piezoelectric shell fragment produced the vibration of fixed frequency, arouses reference arm optic fibre length change, realizes optical fiber interferometer's outer modulation.
3) The utility model discloses in, fix the sensitive optic fibre of the reference arm of optical fiber interferometer on piezoelectric shell fragment, the one end of piezoelectric shell fragment is fixed on the casing, the other end is unsettled, the casing is fixed on the basement rock, when environmental vibration takes place, the casing drives piezoelectric shell fragment and produces the vibration, piezoelectric shell fragment's vibration frequency is decided by its self physical parameter, it is irrelevant with environmental vibration, consequently, make the frequency of referring to arm optic fibre length variation be the single frequency, the casing is except playing the effect of fixed piezoelectric shell fragment, still play the effect that makes the piezoelectric shell fragment amplitude keep invariable.
4) The utility model discloses in, surpass certain threshold value when the environmental vibration range, the free end of piezoelectricity shell fragment touches the top and the bottom of casing, and the vibration range keeps unchanged for the range that reference arm optic fibre length changed is constant, and consequently, when the environmental vibration takes place and surpasss certain threshold value, references arm optic fibre length and produces the change that frequency and range are all invariable, has realized the passive phase place external modulation of fiber optic interferometer.
Drawings
The accompanying drawings, which form a part of the specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention without unduly limiting the scope of the invention.
FIG. 1 is a schematic diagram of the system composition of example 1,
FIG. 2 is a schematic diagram of the system of example 2.
In the figure, 1, a laser, 2, an isolator, 3, a photoelectric detector, 4, a narrow-band filter, 5, a frequency multiplier, 6, a phase demodulation module, 7, a processor, 8, a fiber coupler, 81, a first fiber coupler, 82, a second fiber coupler, 10, a Faraday rotator mirror at the tail end of a reference arm fiber, 11, a shell, 12, a piezoelectric elastic sheet, 13, a sensing arm fiber, 14 and a reference arm fiber.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus are not to be construed as limiting the present invention, and furthermore, the terms "first", "second", "third", and the like are only used for descriptive purposes and are not intended to indicate or imply relative importance.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
Just as the background art said, to the not enough of current interior modulation method, the utility model aims at providing a long-range outer modulation optic fibre interference vibration measuring device and use the device carries out the method of measuring, and its outer modulation mode realizes the phase modulation of optic fibre interferometer, can avoid the production of associated amplitude modulation, and it is right now to combine drawing and detailed implementation mode the utility model discloses further explain.
Example 1
The embodiment discloses a remote external modulation optical fiber interference vibration measuring device, which comprises a laser emitting device, an optical fiber coupler 8, a shell 11, a piezoelectric elastic sheet 12, a vibration probe, a Faraday rotator mirror and a processing device, wherein the laser emitting device and the optical fiber coupler 8, the optical fiber interferometer and the optical fiber coupler 8 and the processing device are connected by optical fibers; the optical fiber interferometer in this embodiment is a michelson structure, that is, the optical fiber coupler 8, the housing 11, the piezoelectric elastic piece 12, the vibration probe, and the faraday rotator in this embodiment form a michelson structure optical fiber interferometer, for convenience of description, in this embodiment, the housing 11, the piezoelectric elastic piece 12, the vibration probe, and the faraday rotator are referred to as an optical fiber interferometer main structure, one end of the piezoelectric elastic piece 12 is fixed to the housing 11, the other end is suspended, and the housing 11 is fixed to bedrock; when environmental vibration occurs, the housing 11 drives the piezoelectric elastic sheet 12 to vibrate.
The laser emitting device comprises a laser 1 and an isolator 2, laser energy emitted by the laser 1 passes through the isolator 2, and the isolator 2 is connected with the optical fiber coupler 8 through an optical fiber.
In this embodiment, the optical fiber coupler 8 includes one, and the laser emitting device, the optical fiber interferometer main body structure and the processing device are all connected to the same optical fiber coupler 8.
More specifically, the optical fiber coupler 8 has a first port, a second port, a third port and a fourth port, the first port of the optical fiber coupler 8 is connected to the laser emitting device through an optical fiber, and the second port of the optical fiber coupler 8 is connected to the processing device through an optical fiber; the third port of the optical fiber coupler 8 is connected with a sensing arm optical fiber 13, and the fourth port of the optical fiber coupler 8 is connected with a reference arm optical fiber 14; the reference arm optical fiber 14 is fixed to the piezoelectric dome 12.
The sensing arm optical fiber 13 comprises a non-sensitive part and a sensitive part, the non-sensitive part optical fiber is used for transmitting a transmission medium of an optical signal, the sensitive part optical fiber is wound on the vibration probe, and the vibration probe is fixed on bedrock to sense environmental vibration;
the reference arm optical fiber 14 comprises a non-sensitive part and a sensitive part, the non-sensitive part optical fiber is used for a transmission medium of an optical signal, and the sensitive part optical fiber is fixed on the piezoelectric elastic sheet 12 to realize the length change of the reference arm optical fiber 14.
The tail end of the sensing arm optical fiber 13 is connected with a vibration probe, the tail ends of the reference arm optical fiber 14 and the sensing arm optical fiber 13 are provided with Faraday rotators, and light waves from the sensing arm optical fiber and the reference arm optical fiber can be reflected by the Faraday rotators.
The processing device comprises a photoelectric detector 3, a narrow-band filter 4, a phase demodulation module 6, a frequency multiplier 5 and a processor 7, wherein the photoelectric detector 3 is electrically connected with the narrow-band filter 4 and the phase demodulation module 6 at the same time, the narrow-band filter 4 is connected with the frequency multiplier 5 and the phase demodulation module at the same time, the frequency multiplier 5 is connected with the phase demodulation module 6, the phase demodulation module 6 is also connected with the processor 7, namely, the phase demodulation module 6 is connected with the frequency multiplier 5, the narrow-band filter 4 and the photoelectric detector 3 at the same time, and the phase demodulation module 6 is also connected with the processor 7. It is understood that the phase demodulation module 6 demodulates the phase signal capable of reflecting the environmental vibration by using the frequency-2 multiplied signal, the frequency-1 multiplied signal and the interference electric signal input by the frequency multiplier 5, the narrow band filter 4 and the photodetector 3, using a classical Differential Cross Multiplication (DCM) or an arc tangent demodulation method, and outputs the phase signal to the processor 7.
The output light of the isolator 2 is transmitted to a first port of the optical fiber coupler 8 through a long-distance optical fiber, so that the effect of isolating the laser 1 from a rear optical fiber link is achieved, and the reflected light of the first port of the optical fiber coupler 8 is prevented from influencing the stability of the laser 1; the third port of the optical fiber coupler 8 is connected with the sensing arm optical fiber 13, and the fourth port of the optical fiber coupler 8 is connected with the reference arm optical fiber 14.
One end of the piezoelectric elastic sheet 12 is fixed on the shell 11, the other end of the piezoelectric elastic sheet is suspended, and the shell 11 is fixed on the bedrock; when environmental vibration occurs, the shell 11 drives the piezoelectric elastic sheet 12 to vibrate; the vibration frequency of the piezoelectric dome 12 is determined by its own physical parameters, and is independent of the environmental vibration, so that the frequency of the length change of the reference arm optical fiber 14 is a single frequency.
The shell 11 plays a role in fixing the piezoelectric elastic sheet 12 and also plays a role in keeping the amplitude of the piezoelectric elastic sheet 12 constant; when the environmental vibration amplitude exceeds a certain threshold value, the suspended end of the piezoelectric elastic sheet 12 touches the top and the bottom of the shell 11, and the vibration amplitude is kept unchanged, so that the amplitude of the length change of the reference arm optical fiber 14 is constant. Therefore, when the environmental vibration occurs and exceeds a certain threshold value, the length of the reference arm optical fiber 14 generates constant frequency and amplitude changes, namely, the out-of-phase modulation of the main structure of the optical fiber interferometer is realized.
The faraday rotator mirror at the end of the sensing arm fiber 13 is placed inside the vibrating probe and reflects the optical signal back to the fiber coupler 8.
The third port and the fourth port of the fiber coupler 8 receive the optical signals returned by the sensing arm and the reference arm, and form interference light at the second port, and output the interference light to the photodetector 3.
The laser 1 selected in this embodiment has a narrow linewidth characteristic, generates a narrow linewidth continuous light, and outputs the narrow linewidth continuous light to the isolator 2.
The photodetector 3 converts the interference optical signal into an interference electrical signal, and transmits the interference electrical signal to the narrow-band filter 4 and the phase demodulation module 6. The filter passband range of the narrow-band filter 4 is the vibration frequency of the piezoelectric elastic sheet 12, and can extract 1 frequency doubling signal modulated outside the phase from the interference electric signal and transmit the signal to the frequency multiplier 5 and the phase demodulation module 6. The frequency multiplier 5 multiplies the frequency of the frequency-multiplied signal 1 to obtain a frequency-multiplied signal 2 modulated outside the phase, and transmits the frequency-multiplied signal 2 to the phase demodulation module 6. The phase demodulation module 6 demodulates the input frequency-1 multiplied signal, frequency-2 multiplied signal and interference electric signal to obtain a phase signal capable of reflecting the environmental vibration by using a classical Differential Cross Multiplication (DCM) or arc tangent demodulation method, and outputs the phase signal to the processor 7. The processor 7 calculates and records the measurement data of the speed, acceleration, displacement and the like of the environmental vibration according to the input phase signal and the response characteristic of the phase signal relative to the environmental vibration.
It is understood that the laser 1, the isolator 2, the fiber coupler 8, the vibration probe, the piezoelectric dome 12, the housing 11, the faraday rotator, the photodetector 3, the narrow-band filter 4, the frequency multiplier 5, the phase demodulation module 6, and the processor 7 used in the present embodiment are all conventional components.
It can be understood that the laser 1, the isolator 2, the photodetector 3, the narrow-band filter 4, the frequency multiplier 5, the phase demodulation module 6 and the processor 7 in the present embodiment are all connected to a power supply.
Example 2
Example 2 differs from example 1 in that, in example 2, referring to fig. 2, the optical fiber interferometer is changed from a michelson structure to a mach-zehnder structure, that is, the optical fiber coupler 8, the vibration probe, the piezoelectric elastic piece 12, the housing 11, and the optical fiber coupler 8 constitute the mach-zehnder optical fiber interferometer, instead of the michelson optical fiber interferometer composed of the optical fiber coupler 8, the vibration probe, the piezoelectric elastic piece 12, the housing 11, and the faraday rotator in embodiment 1, that is, the optical fiber interferometer in this example does not include the faraday rotator in its main structure.
The optical fiber coupler 8 in the present embodiment includes two optical fiber couplers, the optical fiber coupler 8 includes a first optical fiber coupler 81 and a second optical fiber coupler 82, the laser transmitter is connected to the first optical fiber coupler 81, the optical fiber interferometer is connected to both the first optical fiber coupler 81 and the second optical fiber coupler 82, and the processing device is connected to the second optical fiber coupler 82.
The first optical fiber coupler 81 is provided with a first port, a second port, a third port and a fourth port, the first port of the first optical fiber coupler 81 is connected with the laser emitting device through an optical fiber, the second port of the first optical fiber coupler 81 is vacant, the third port of the first optical fiber coupler 81 is connected with the sensing arm optical fiber 13, and the fourth port of the first optical fiber coupler 81 is connected with the reference arm optical fiber 14;
the second optical fiber coupler 82 is provided with a first port, a second port, a third port and a fourth port, the first port of the second optical fiber coupler 82 is vacant, the second port of the second optical fiber coupler 82 is connected with a processing device, the third port of the second optical fiber coupler 82 is connected with the reference arm optical fiber 14, and the fourth port of the second optical fiber coupler 82 is connected with the sensing arm optical fiber 13.
Example 3
in step 1, the laser 1 outputs continuous light with a wavelength of 1550nm or 1330nm suitable for optical fiber transmission.
Wherein E isL(t) electric field intensity of continuous light output from the laser 1, ECMagnitude value, v, representing electric field strengthCWhich is representative of the frequency of the light,
representing the laser 1 phase noise randomly varying with time, and t represents time.
And 2, passing the continuous light through an optical fiber interferometer comprising a sensing arm and a reference arm, and forming an interference light signal at an output port of the optical fiber coupler 8:
wherein, Iinter(t) represents interference light, KctAnd KccRespectively representing the through coefficient and the coupling coefficient, K, of the fiber coupler 8MDenotes the reflection coefficient of the Faraday rotator mirror in the vibrating probe and in the reference arm, n denotes the refractive index of the optical fiber, LAAnd LBIndicating the initial lengths, L, of the sensing arm and reference arm optical fibers 14, respectivelyra(t) shows the change in length of the sensing arm fiber 13 due to environmental vibrations through the vibrating probe, Lrb(t) shows the change in length of the reference arm optical fiber 14 caused by the environmental vibration through the piezoelectric dome 12, t1Represents the time delay, t, of the return of the light wave in the optical fiber 13 of the sensing arm2Indicating the time delay of the return of the optical wave in the reference arm fiber 14. KbRepresenting the amplitude of the change in length, ω, of the reference arm fiber 14CIndicating the frequency of change of the length of the reference arm fiber 14,
indicating the initial phase of the change in length of the reference arm fiber 14.
And step 3, the interference light passes through a photoelectric detector 3, a narrow-band filter 4 and a frequency multiplier 5 to obtain an interference electric signal, a frequency multiplication signal 1 and a frequency multiplication signal 2.
And step 4, demodulating the frequency-1 multiplied signal, the frequency-2 multiplied signal and the interference electric signal by using a classical Differential Cross Multiplication (DCM) or an arc tangent demodulation method to obtain a phase signal capable of reflecting the environmental vibration.
And 5, calculating to obtain measurement data of the speed, the acceleration, the displacement and the like of the environmental vibration according to the phase signal and the response characteristic of the phase signal relative to the environmental vibration.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A remote external modulation optical fiber interference vibration measuring device is characterized by comprising a laser emitting device, an optical fiber coupler, an optical fiber interferometer main body structure and a processing device, wherein the laser emitting device and the optical fiber coupler, the optical fiber interferometer main body structure and the optical fiber coupler and the processing device are connected by optical fibers;
the optical fiber interferometer main body structure comprises a shell and a piezoelectric elastic sheet, wherein one end of the piezoelectric elastic sheet is fixed on the shell, the other end of the piezoelectric elastic sheet is suspended in the air, the shell is fixed on bedrock, and an optical fiber between the optical fiber interferometer main body structure and an optical fiber coupler is fixed on the piezoelectric elastic sheet; when the environmental vibration takes place, the casing drives the piezoelectric elastic piece to produce the vibration.
2. The remote external modulation fiber optic interferometric vibration measuring device of claim 1, wherein the laser emitting device comprises a laser and an isolator, laser energy emitted by the laser passes through the isolator, and the isolator and the fiber optic coupler are connected by an optical fiber.
3. The remote external-modulation fiber-optic interferometric vibration measuring device of claim 1, wherein when a fiber-optic coupler comprises one, the laser emitting device, the fiber-optic interferometer body structure, and the processing device are all connected to the same fiber-optic coupler.
4. The remote external modulation fiber-optic interferometric vibration measuring device of claim 3, wherein the fiber-optic coupler has a first port, a second port, a third port and a fourth port, the first port of the fiber-optic coupler is connected to the laser emitting device through an optical fiber, and the second port of the fiber-optic coupler is connected to the processing device through an optical fiber; the third port of the optical fiber coupler is connected with the sensing arm optical fiber, and the fourth port of the optical fiber coupler is connected with the reference arm optical fiber; the reference arm optical fiber is fixed on the piezoelectric elastic sheet.
5. The remote external modulation optical fiber interferometric vibration measuring device according to claim 4, wherein the sensing arm optical fiber comprises a non-sensitive part and a sensitive part, the non-sensitive part optical fiber is used for a transmission medium of optical signals, the sensitive part optical fiber is wound around the vibration probe, and the vibration probe is fixed on bedrock to sense environmental vibration;
the reference arm optical fiber comprises a non-sensitive part and a sensitive part, the non-sensitive part optical fiber is used for a transmission medium of an optical signal, and the sensitive part optical fiber is fixed on the piezoelectric elastic sheet to realize the change of the length of the reference arm optical fiber.
6. The remote external modulation optical fiber interferometric vibration measuring device of claim 4, wherein the end of the sensing arm optical fiber is connected to a vibration probe, the end of the reference arm optical fiber and the end of the sensing arm optical fiber are provided with Faraday rotators, and light waves from the sensing arm optical fiber and the reference arm optical fiber can be reflected by the Faraday rotators.
7. The remote external modulation fiber optic interferometric vibration measuring device of claim 1, wherein when the fiber couplers include two, the fiber couplers include a first fiber coupler and a second fiber coupler, the laser transmitter is connected to the first fiber coupler, the fiber optic interferometer body structure is connected to both the first fiber coupler and the second fiber coupler, and the processing device is connected to the second fiber coupler.
8. The remote external modulation fiber-optic interferometric vibration measuring device of claim 7, wherein the first fiber-optic coupler has a first port, a second port, a third port and a fourth port, the first port of the first fiber-optic coupler is connected to the laser emitting device through an optical fiber, the second port of the first fiber-optic coupler is left empty, the third port of the first fiber-optic coupler is connected to the sensing arm optical fiber, and the fourth port of the first fiber-optic coupler is connected to the reference arm optical fiber;
the second optical fiber coupler is provided with a first port, a second port, a third port and a fourth port, the first port of the second optical fiber coupler is vacant, the second port of the second optical fiber coupler is connected with the processing device, the third port of the second optical fiber coupler is connected with the reference arm optical fiber, and the fourth port of the second optical fiber coupler is connected with the sensing arm optical fiber.
9. The remote external modulation optical fiber interferometric vibration measuring device according to claim 1, wherein the processing device comprises a photodetector, a narrow band filter, a phase demodulation module, a frequency multiplier and a processor, the photodetector is electrically connected to the narrow band filter and the phase demodulation module at the same time, the narrow band filter is connected to the frequency multiplier and the phase demodulation module at the same time, the frequency multiplier is connected to the phase demodulation module, and the phase demodulation module is further connected to the processor.
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