CN217877992U - Distributed optical fiber vibration monitoring equipment - Google Patents

Abstract

The utility model provides a distributing type optic fibre vibration monitoring facilities. The distributed optical fiber vibration monitoring equipment comprises a laser source, a first acousto-optic modulator, an erbium-doped optical fiber amplifier, a second acousto-optic modulator and a circulator which are sequentially connected in series, and further comprises a sensing optical fiber and a data acquisition card, wherein the circulator is provided with a first port, a second port and a third port, the output end of the second acousto-optic modulator is connected with the first port of the circulator, the second port of the circulator is connected with the sensing optical fiber, and the third port of the circulator is connected with the data acquisition card; the first acousto-optic modulator is used for modulating the light emitted by the laser source to generate a first optical pulse signal, and the second acousto-optic modulator is used for modulating the first optical pulse signal to generate a second optical pulse signal, wherein the carrier frequency of the second optical pulse signal is less than or equal to 10MHz. Through the technical scheme of the utility model the carrier frequency that can reduce original light path.

Description

Distributed optical fiber vibration monitoring equipment

Technical Field

The utility model relates to an optical fiber sensing technical field particularly, relates to a distributing type optic fibre vibration monitoring facilities.

Background

Distributed optical fiber vibration monitoring apparatus, utilizing

The OTDR (i.e. optical time domain reflectometer) technique principle monitors the pulsed light in the optical fiber. When the optical fiber is disturbed, the phase information of the optical pulse changes (forms an optical path difference). The intensity of the optical signal collected by coherent detection changes.

The pulsed light is typically modulated by an acousto-optic modulator (AOM), the carrier frequency of which is typically 200MHz, and the sampling rate of the photodetector is at least 2 times the frequency of the target signal, typically 1GHz in practice, for complete signal acquisition according to the nyquist sampling law. When the 2-channel 50km monitoring is realized, if the acquisition is carried out according to the 1GHz sampling rate and the 100Hz optical pulse refreshing frequency, the data throughput per second is 200MB.

The existing equipment has insufficient refresh frequency of light pulse due to large real-time acquisition data volume, so that the acquired vibration signals are mixed in a low-frequency space, and the conditions of missing report and false report with high probability are caused.

SUMMERY OF THE UTILITY MODEL

The utility model discloses a main aim at provides a distributing type optic fibre vibration monitoring facilities, can reduce the carrier frequency of original light path through distributing type optic fibre vibration monitoring facilities, promotes the refresh frequency of light pulse.

In order to achieve the above object, the utility model provides a distributed optical fiber vibration monitoring device, including laser source, first acousto-optic modulator, erbium-doped fiber amplifier, second acousto-optic modulator and circulator that set up in series in proper order, distributed optical fiber vibration monitoring device still includes sensing optical fiber and data acquisition card, wherein, the circulator has first port, second port and third port, and the output of second acousto-optic modulator is connected with the first port of circulator, and the second port of circulator is connected with sensing optical fiber, and the third port of circulator is connected with data acquisition card; the first acousto-optic modulator is used for modulating the light emitted by the laser source to generate a first optical pulse signal, and the second acousto-optic modulator is used for modulating the first optical pulse signal to generate a second optical pulse signal, wherein the carrier frequency of the second optical pulse signal is less than or equal to 10MHz.

Furthermore, the first acousto-optic modulator is in a positive frequency shift working state, and the second acousto-optic modulator is in a negative frequency shift working state; or the first acousto-optic modulator is in a negative frequency shift working state, and the second acousto-optic modulator is in a positive frequency shift working state.

Furthermore, the distributed optical fiber vibration monitoring device further comprises a first branch and two second branches, wherein the first end of the first branch is connected with the data acquisition card, the first ends of the two second branches are both connected with the second end of the first branch, the second end of one second branch is connected with the first acousto-optic modulator, and the second end of the other second branch is connected with the second acousto-optic modulator, so that optical signals output by the first acousto-optic modulator and the second acousto-optic modulator are respectively controlled through the data acquisition card.

Further, the distributed optical fiber vibration monitoring device further comprises: the DDS signal generator is arranged at the joint between the first branch and the second branch; the operational amplifier is arranged on the first branch; the data acquisition card is connected with the DDS signal generator through the operational amplifier.

Further, the distributed optical fiber vibration monitoring device further comprises a delay cable; a delay cable is arranged between the DDS signal generator and the first acousto-optic modulator; and/or a delay cable is arranged between the DDS signal generator and the second acousto-optic modulator.

Further, the distributed optical fiber vibration monitoring device further comprises: a first driving part arranged between the DDS signal generator and the first acousto-optic modulator; and a second driving part disposed between the DDS signal generator and the second acousto-optic modulator.

Further, the distributed optical fiber vibration monitoring equipment further comprises a first coupler and a second coupler; the laser source is connected with the input end of the first coupler, the first output end of the first coupler is connected with the first acousto-optic modulator, and the second output end of the first coupler is connected with the first input end of the second coupler; and a third port of the circulator is connected with a second input end of the second coupler, and an output end of the second coupler is connected with the data acquisition card.

Furthermore, the distributed optical fiber vibration monitoring device further comprises an electric signal amplifier, and the electric signal amplifier is arranged between the second coupler and the data acquisition card.

Further, the distributed optical fiber vibration monitoring device further comprises: a photodetector disposed between the second coupler and the electrical signal amplifier; and/or, a filter disposed between the electrical signal amplifier and the data acquisition card.

Further, the distributed optical fiber vibration monitoring device further comprises: a variable optical attenuator disposed between the first coupler and the second coupler; and/or an optical filter arranged between the third port of the circulator and the second coupler.

Use the technical scheme of the utility model, laser source is used for producing the light of certain wavelength and exports to first reputation modulator. The first acousto-optic modulator is used for modulating the light input by the laser source to generate a first optical pulse signal with a proper bandwidth and outputting the first optical pulse signal to the erbium-doped fiber amplifier. The erbium-doped fiber amplifier is used for amplifying the power of the first optical pulse signal and outputting the first optical pulse signal to the second acousto-optic modulator. The second acousto-optic modulator is used for modulating the first optical pulse signal after power amplification so as to generate a second optical pulse signal with a proper bandwidth and outputting the second optical pulse signal to the circulator. The circulator is used for transmitting a second optical pulse signal input by the second acousto-optic modulator to the sensing optical fiber and transmitting light scattered by the sensing optical fiber to the data acquisition card. The data acquisition card is used for performing photoelectric conversion, acquisition and signal processing on the optical signal input by the circulator and outputting the optical signal to the computer unit for algorithm processing. The embodiment of the utility model provides an in, through setting up two acousto-optic modulator (being first acousto-optic modulator and second acousto-optic modulator) of series connection, make the carrier frequency that passes through the second light pulse signal after first acousto-optic modulator and the modulation of second acousto-optic modulator in proper order be less than or equal to 10MHz, reduced the carrier frequency of original light path, promoted the refresh frequency of light pulse.

Drawings

The accompanying drawings, which form a part of the present application, 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 and not to limit the invention. In the drawings:

fig. 1 shows a circuit diagram of an embodiment of a distributed fiber optic vibration monitoring device according to the present invention.

Wherein the figures include the following reference numerals:

10. a laser source; 20. a first acousto-optic modulator; 30. a second acousto-optic modulator; 40. an erbium-doped fiber amplifier; 50. a circulator; 60. a sensing optical fiber; 70. a data acquisition card; 80. a first branch; 90. a second branch circuit; 100. a DDS signal generator; 110. an operational amplifier; 120. a delay cable; 130. a first driving section; 140. a second driving section; 150. a first coupler; 160. a second coupler; 170. an electrical signal amplifier; 180. a photodetector; 190. a filter; 200. a variable optical attenuator; 210. an optical filter; 220. a wavelength division multiplexer; 230. an optical isolator; 240. a Raman fiber amplifier; 250. a delay optical fiber; 260. a computer unit.

Detailed Description

It should be noted that, in the present application, the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

It is noted that, unless otherwise indicated, 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 application belongs.

In the present application, where the contrary is not intended, the use of directional terms such as "upper, lower, top, bottom" generally refer to the orientation as shown in the drawings, or to the component itself being oriented in a vertical, perpendicular, or gravitational direction; likewise, for ease of understanding and description, "inner and outer" refer to the inner and outer relative to the profile of the components themselves, but the above directional words are not intended to limit the invention.

The existing distributed optical fiber vibration monitoring equipment has insufficient refresh frequency of optical pulses due to large real-time acquisition data volume, so that the acquired vibration signals are subjected to aliasing in a low-frequency space, and the conditions of high probability of missing report and false report are caused.

Because the data amount (sampling rate of the acquisition card) multiplied by the monitoring distance (sampling point) multiplied by the refresh rate per second (vibration monitoring bandwidth) generated by real-time demodulation is a fixed value (an upper limit exists), the sampling rate required by the traditional scheme for the acquisition card is larger, and the latter two parameters, particularly the refresh rate per second, must be sacrificed at the moment. If the refresh rate per second is increased, the monitoring distance (i.e. sampling point) must be sacrificed, so that the DAS (i.e. distributed acoustic sensing system) is basically equivalent to the DVS (i.e. distributed vibration sensing system) device in application and cannot exert the phase resolving capability.

As shown in fig. 1, in an embodiment of the present invention, the distributed optical fiber vibration monitoring apparatus includes a laser source 10, a first acousto-optic modulator 20, an erbium-doped fiber amplifier 40, a second acousto-optic modulator 30, and a circulator 50, which are sequentially connected in series, and the distributed optical fiber vibration monitoring apparatus further includes a sensing fiber 60 and a data acquisition card 70, where the circulator has a first port, a second port, and a third port, an output end of the second acousto-optic modulator 30 is connected to the first port of the circulator 50, the second port of the circulator 50 is connected to the sensing fiber 60, and the third port of the circulator 50 is connected to the data acquisition card 70; the first acousto-optic modulator 20 is configured to modulate light emitted from the laser source 10 to generate a first optical pulse signal, and the second acousto-optic modulator 30 is configured to modulate the first optical pulse signal to generate a second optical pulse signal, wherein a carrier frequency of the second optical pulse signal is less than or equal to 10MHz.

In the embodiment of the present invention, the laser source 10 is used to generate light with a certain wavelength and output the light to the first acousto-optic modulator 20. The first acousto-optic modulator 20 is used for modulating the light input from the laser source 10 to generate a first optical pulse signal with a suitable bandwidth and outputting the first optical pulse signal to the erbium-doped fiber amplifier 40. The erbium-doped fiber amplifier 40 is configured to perform power amplification on the first optical pulse signal and output the first optical pulse signal to the second acousto-optic modulator 30. The second acousto-optic modulator 30 is used for modulating the first optical pulse signal after power amplification to generate a second optical pulse signal with a suitable bandwidth and outputting the second optical pulse signal to the circulator 50. The circulator 50 is configured to transmit the second optical pulse signal input by the second acousto-optic modulator 30 into the sensing fiber 60, and transmit the light scattered by the sensing fiber 60 to the data acquisition card 70. The data acquisition card 70 is used for performing photoelectric conversion, acquisition and signal processing on the optical signal input by the circulator 50 and outputting the optical signal to the computer unit 260 for algorithm processing.

The embodiment of the utility model provides an in, through setting up two acousto-optic modulator (being first acousto-optic modulator 20 and second acousto-optic modulator 30) of series connection, make the carrier frequency that passes through the second light pulse signal after first acousto-optic modulator 20 and the modulation of second acousto-optic modulator 30 in proper order be less than or equal to 10MHz, reduced the carrier frequency of original light path, promoted the refresh frequency of light pulse.

The embodiment of the utility model discloses a through improving the light path, reduced the carrier frequency of original light path, consequently can carry out data processing to the signal with 100 MHz's sampling rate, can guarantee under the unchangeable condition of every second data throughput 200MB like this, promote 1000Hz with the refresh rate of light pulse. Equivalently, the monitoring bandwidth of the vibration event is increased from 100Hz to 1000Hz within the range of 50km of 2 channels, compared with the traditional scheme, the refresh rate range per second is increased by one order of magnitude, and the data processing capability and the identification capability of the DAS equipment on real-time signal analysis are greatly improved. And in principle and the whole cost of the equipment can not be changed, so that the method is worthy of wide popularization. The embodiment of the utility model provides an in, distributed optical fiber vibration monitoring facilities is a low data volume, the real-time distributed optical fiber vibration analytic equipment of high refresh rate, and its carrier signal frequency is low, and the original data volume is the 10% of the original data volume of general scheme collection. Because the amount of the original data acquired at a time is low, the refresh rate under the same data density can be increased to 10 times of that of a common scheme, the time sampling frequency of the vibration signal is increased by 10 times, and parameters such as amplitude and phase of vibration can be better analyzed.

Low data volume: in order to obtain a pulse signal with high extinction ratio and stable output power, a 200MHz acousto-optic modulator (i.e. AOM) is adopted for signal modulation in a general scheme, so that a carrier signal is 200MHz, and according to the nyquist sampling law, at least 2-5 sampling multiples are required to perform aliasing-free sampling on the signal at the moment, and generally, 1GHz (i.e. 5 times) is selected for sampling; according to the technical scheme, 10MHz carrier signals are adopted, and sampling is carried out according to 100MHz, so that 10 times of sampling rate can be obtained.

High refresh rate: according to the sampling rate mode, in a general scheme 2, 100 ten thousand sampling points are required every 50km, each sampling point occupies 2 bytes, 100Hz is adopted for calculation according to 1 second, and the data volume per second is 200M Byte. In the technical scheme of the application, the data volume of 200M bytes per second can realize 1000Hz sampling. Since the data is transmitted, processed and displayed by the necessary calculation, there is a maximum processing data amount (in practice, the maximum data processing amount is 200M bytes/s) in order to ensure that the processed data is displayed within 1 second. Due to the limitation of the maximum data processing capacity, the refresh rate of the technical scheme can be increased by 10 times on the premise of ensuring that the equipment processes the vibration signals in real time.

The high-quality analysis of the vibration signal means that a general scheme transmits 100 optical pulses per second, and on the premise of the same data volume, the technical scheme of the application can realize 1000Hz optical pulse sampling. In the case of a 100Hz sampling rate, the frequency of the vibration signal subjected to FFT (i.e., fast fourier transform) processing is aliased in the range of 0 to 100Hz, and in the case of a 1000Hz sampling rate, the frequency of the vibration signal is aliased in the range of 0 to 1000Hz. Generally, after a vibration signal acquired by distributed optical fiber vibration is attenuated, the attenuation amplitude of a high-frequency component is larger, if the vibration signal is mixed with a low-frequency signal and then is processed by an algorithm, high-fidelity analysis is difficult to realize, and therefore the occurrence probability of false alarm and false alarm failure after DAS (distributed optical system) identification in the traditional scheme is higher. If the general scheme also adopts a refresh rate of 1000Hz for acquisition, the real-time signal processing cannot be realized on the premise of being limited by the maximum data processing amount. Therefore, the technical scheme of the application has higher original signal quality due to the advantage of high refresh rate on the premise of ensuring the time-sharing signal acquisition end.

It should be noted that, limited by the speed of light, the monitoring distance × refresh rate should be less than 10 kilometers, and the theoretical maximum refresh rate at 50 kilometers is 2000Hz, but considering the oscillation effect caused by fresnel reflection, the duty cycle of the optical pulse signal in the optical fiber should be less than 50%, so for a monitoring distance of 50km, 1000Hz is the maximum optical pulse refresh rate, and if the monitoring distance is 1km, the theoretical maximum optical pulse refresh rate of the system is 50kHz.

In the embodiment of the utility model, the optical pulse carrier frequency of distributed optical fiber vibration monitoring equipment is no longer than 10MHz, rather than the 200MHz of traditional scheme. Compared with the traditional scheme, the method and the device reduce the carrier frequency of the vibration signal, improve the refreshing frequency of the optical pulse and reduce the sampling rate of the acquisition card. Moreover, the two acousto-optic modulators (i.e. the first acousto-optic modulator 20 and the second acousto-optic modulator 30) are connected in series, so that the extinction ratio of the optical pulse can be improved, and the ASE noise interference can be reduced.

In the embodiment of the present invention, the first acousto-optic modulator 20 is in the positive frequency shift operating state, and the second acousto-optic modulator 30 is in the negative frequency shift operating state.

The embodiment of the utility model provides an in, distributed optical fiber vibration monitoring facilities is inside to have adopted positive and negative frequency shift acousto-optic modulator to join in marriage the group, rather than traditional single frequency shift acousto-optic modulator. The carrier frequency of the second optical pulse signal can be reduced to 10MHz by the set of acousto-optic modulators with a 200MHz positive shift frequency of the first acousto-optic modulator 20 and a-190 MHz negative shift frequency of the second acousto-optic modulator 30.

Of course, in alternative embodiments of the present application, the first acousto-optic modulator 20 may be in the negative frequency shift operating state, and the second acousto-optic modulator 30 may be in the positive frequency shift operating state according to actual needs.

As shown in fig. 1, in an embodiment of the present invention, the distributed optical fiber vibration monitoring apparatus further includes a first branch 80 and two second branches 90, a first end of the first branch 80 is connected to the data acquisition card 70, first ends of the two second branches 90 are both connected to a second end of the first branch 80, a second end of one of the second branches 90 is connected to the first acousto-optic modulator 20, and a second end of the other second branch 90 is connected to the second acousto-optic modulator 30, so as to respectively control optical signals output by the first acousto-optic modulator 20 and the second acousto-optic modulator 30 through the data acquisition card 70.

In the above arrangement, the first acousto-optic modulator 20 and the second acousto-optic modulator 30 can be respectively controlled to output optical signals with different pulse widths according to the parameter configuration of the data acquisition card 70.

As shown in fig. 1, in the embodiment of the present invention, the distributed fiber vibration monitoring device further includes a DDS signal generator 100 and an operational amplifier 110, the DDS signal generator 100 is disposed at the connection between the first branch 80 and the second branch 90; the operational amplifier 110 is disposed on the first branch 80; the data acquisition card 70 is connected to the DDS signal generator 100 through an operational amplifier 110.

In the above arrangement, the operational amplifier 110 can be used to correct the power of the control signal output from the data acquisition card 70. Initial phase synchronization of two paths of signals on the two second branches 90 is realized through the DDS signal generator 100, so that phase synchronization of the positive and negative frequency shift acousto-optic modulator groups is realized.

As shown in fig. 1, in an embodiment of the present invention, the distributed fiber optic vibration monitoring device further includes a delay cable 120; a delay cable 120 is provided between the DDS signal generator 100 and the first acousto-optic modulator 20.

By arranging the delay cable 120, the circuit and the optical path are delayed and synchronized, and the optical pulse synchronization is realized, so that the pulse synchronization of the positive and negative frequency shift acousto-optic modulator group is realized.

Of course, in an alternative embodiment of the present application, a delay cable 120 may be provided between the DDS signal generator 100 and the second acousto-optic modulator 30 according to actual needs.

As shown in fig. 1, in the embodiment of the present invention, the distributed optical fiber vibration monitoring apparatus further includes a first driving portion 130 and a second driving portion 140, the first driving portion 130 is disposed between the DDS signal generator 100 and the first acousto-optic modulator 20; the second driving part 140 is disposed between the DDS signal generator 100 and the second acousto-optic modulator 30.

In the above arrangement, the first driving unit 130 is used for driving the first acousto-optic modulator 20 to operate; the second driving unit 140 is used to drive the second acousto-optic modulator 30 to operate.

Preferably, the first driving part 130 is an AOM driver. The second driving part 140 is an AOM driver.

As shown in fig. 1, in the embodiment of the present invention, the DDS signal generator 100, the first driving unit 130, the delay cable 120, and the first acousto-optic modulator 20 are sequentially disposed.

As shown in fig. 1, in an embodiment of the present invention, the distributed fiber optic vibration monitoring device further includes a first coupler 150 and a second coupler 160; the laser source 10 is connected to the input end of the first coupler 150, the first output end of the first coupler 150 is connected to the first acousto-optic modulator 20, and the second output end of the first coupler 150 is connected to the first input end of the second coupler 160; the third port of the circulator 50 is connected to the second input terminal of the second coupler 160, and the output terminal of the second coupler 160 is connected to the data acquisition card 70.

In the above arrangement, the first output end of the first coupler 150 is connected to the first acousto-optic modulator 20, and is configured to transmit the initial detection light to the first acousto-optic modulator 20; a second output terminal of the first coupler 150 is connected to a first input terminal of the second coupler 160, and is configured to transmit local oscillator light to the second coupler 160; a third port of the circulator 50 is connected to a second input of the second coupler 160 for transmitting the scattered light received from the sensing fiber 60 to the second coupler 160; the output terminal of the second coupler 160 is connected to the data acquisition card 70, and the second coupler 160 is configured to mix the received local oscillator light and the scattered light to form a coherent light signal, and transmit the coherent light signal to the data acquisition card 70.

As shown in fig. 1, in an embodiment of the present invention, the distributed optical fiber vibration monitoring apparatus further includes an electrical signal amplifier 170, and the electrical signal amplifier 170 is disposed between the second coupler 160 and the data acquisition card 70.

The embodiment of the utility model provides an in, distributed optical fiber vibration monitoring facilities's signal receiving terminal has adopted real-time adjustable electric signal amplifier 170, can be according to receiving terminal signal characteristic, and the relation between adjustment signal and the data acquisition card input range improves equipment signal bit width utilization ratio as much as possible.

As shown in fig. 1, in an embodiment of the present invention, the distributed optical fiber vibration monitoring apparatus further includes a photodetector 180 and a filter 190, the photodetector 180 is disposed between the second coupler 160 and the electrical signal amplifier 170; the filter 190 is arranged between the electrical signal amplifier 170 and the data acquisition card 70.

In the above arrangement, the photodetector 180 is used to convert the optical signal into an electrical signal. The filter 190 can effectively filter a frequency point of a specific frequency in the power line or frequencies other than the frequency point to obtain a power signal of the specific frequency, or eliminate the power signal of the specific frequency.

Of course, in alternative embodiments of the present application, the distributed optical fiber vibration monitoring apparatus may further include the photodetector 180 or the filter 190 according to actual needs.

As shown in fig. 1, in an embodiment of the present invention, the distributed optical fiber vibration monitoring apparatus further includes a variable optical attenuator 200 and an optical filter 210, the variable optical attenuator 200 is disposed between the first coupler 150 and the second coupler 160; an optical filter 210 is arranged between the third port of the circulator 50 and the second coupler 160.

In the above arrangement, the variable optical attenuator 200 can implement real-time control of the signal by attenuating the transmitted optical power. The optical filter 210 can select a desired wavelength from a plurality of wavelengths, and light other than the wavelength is rejected; it can be used for wavelength selection, noise filtering of optical amplifiers, gain equalization, optical multiplexing/demultiplexing.

Of course, in alternative embodiments of the present application, the distributed optical fiber vibration monitoring apparatus may further include a variable optical attenuator 200 or an optical filter 210 according to actual needs.

Distributed optical fiber vibration monitoring equipment can be applied to the fields of perimeter security protection, military (border line monitoring), oil and gas pipelines, intelligent pipe galleries, wind power generation, environment monitoring (10 m level), power cables, submarine cable monitoring and the like.

As shown in fig. 1, in the embodiment of the present invention, a wavelength division multiplexer 220 is disposed on the sensing fiber 60, an optical isolator 230, a raman fiber amplifier 240 and a delay fiber 250, a second port of the circulator 50 is connected to a first port of the wavelength division multiplexer 220, a second port of the wavelength division multiplexer 220 is connected to the delay fiber 250, a third port of the wavelength division multiplexer 220 is connected to one end of the optical isolator 230, another end of the optical isolator 230 is connected to the raman fiber amplifier 240, wherein two or more optical wavelength signals can be transmitted separately through different optical channels in the same optical fiber by the wavelength division multiplexer 220. The optical isolator 230 can allow light to pass through in one direction and prevent the passive device that passes through to opposite direction, and the effect is to the direction of light restriction, makes light unidirectional transmission only, and the light that reflects through the optic fibre echo can be by the fine isolation of optical isolator, improves light wave transmission efficiency. The raman fiber amplifier 240 is used to amplify the optical signal. The delay fiber 250 is used to delay the optical signal.

It should be noted that the main improvement point of the technical solution of the present application is that two acousto-optic modulators (i.e. the first acousto-optic modulator 20 and the second acousto-optic modulator 30) are arranged in series, each component correspondingly connected to the two acousto-optic modulators, and the electrical signal amplifier 170, etc., the sensing optical fiber 60 may adopt a sensing optical fiber which is conventional in the art, and the components (such as the wavelength division multiplexer 220, the optical isolator 230, and the raman optical fiber amplifier 240) arranged on the sensing optical fiber 60 may also adopt a conventional technique in the art, and components arranged on the sensing optical fiber 60 may be added or reduced according to actual situations and actual needs, which are not described herein again.

As shown in fig. 1, in the embodiment of the present invention, the probe light emitted from the laser source 10 is divided into the signal light propagating toward the first acousto-optic modulator 20 and the intrinsic light propagating toward the variable optical attenuator 200 via the first coupler 150. The signal light is transmitted in sequence along the first acousto-optic modulator 20, the erbium-doped fiber amplifier 40, the second acousto-optic modulator 30 and the circulator 50, the signal light enters the circulator 50 through the first port of the circulator 50, is output through the second port of the circulator 50 and is transmitted to the wavelength division multiplexer 220; the raman pump light emitted from the raman fiber amplifier 240 passes through the optical isolator 230 and then propagates to the wavelength division multiplexer 220, the signal light and the raman pump light are combined at the wavelength division multiplexer 220, the combined optical signal passes through the delay fiber 250 and then propagates to the external test fiber, the external test fiber reflects the combined optical signal, so that the combined optical signal returns along the original path (in the following description, the combined optical signal returning along the original path is referred to as reflected light), the reflected light passes through the delay fiber 250 and the wavelength division multiplexer 220 in sequence, then enters the circulator 50 through the second port of the circulator 50 again, and is output to the optical filter 210 through the third port of the circulator 50, the reflected light passing through the optical filter 210 and the intrinsic light passing through the variable coupler 200 are merged at the second coupler 160, and form coherent light after interference of the second coupler 160, and the coherent light passes through the electrical signal amplifier 170, the filter 190, the data acquisition card 70 in sequence and then enters the computer unit 260.

The data acquisition card 70 sends out an electrical signal that drives the first acousto-optic modulator 20 and the second acousto-optic modulator 30, which is power corrected at the op-amp 110; then, the signals are transmitted to the DDS signal generator 100, and the phase synchronization of the positive and negative frequency shift acousto-optic modulator groups can be realized through the DDS signal generator 100; then, the electrical signals on the two second branches 90 respectively control the first driving portion 130 to drive the first acousto-optic modulator 20 to operate, and control the second driving portion 140 to drive the second acousto-optic modulator 30 to operate, wherein a delay cable 120 is arranged between the first driving portion 130 and the first acousto-optic modulator 20, and pulse synchronization of the positive and negative frequency shift acousto-optic modulator groups can be realized by arranging the delay cable 120.

From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: the laser source is used for generating light with a certain wavelength and outputting the light to the first acousto-optic modulator. The first acousto-optic modulator is used for modulating the light input by the laser source to generate a first optical pulse signal with a proper bandwidth and outputting the first optical pulse signal to the erbium-doped fiber amplifier. The erbium-doped fiber amplifier is used for carrying out power amplification on the first optical pulse signal and outputting the first optical pulse signal to the second acoustic optical modulator. And the second acoustic optical modulator is used for modulating the first optical pulse signal after power amplification to generate a second optical pulse signal with a proper bandwidth and outputting the second optical pulse signal to the circulator. The circulator is used for transmitting a second optical pulse signal input by the second acousto-optic modulator to the sensing optical fiber and transmitting light scattered by the sensing optical fiber to the data acquisition card. The data acquisition card is used for performing photoelectric conversion, acquisition and signal processing on the optical signal input by the circulator and outputting the optical signal to the computer unit for algorithm processing. The embodiment of the utility model provides an in, through setting up two acousto-optic modulator (being first acousto-optic modulator and second acousto-optic modulator) of series connection, make the carrier frequency that passes through the second light pulse signal after first acousto-optic modulator and the modulation of second acousto-optic modulator in proper order be less than or equal to 10MHz, reduced the carrier frequency of original light path, promoted the refresh frequency of light pulse.

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 according to the present application. As used herein, the singular is intended to include the plural unless the context clearly dictates otherwise, and it should be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of features, steps, operations, devices, components, and/or combinations thereof.

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 (10)

1. A distributed optical fiber vibration monitoring device is characterized by comprising a laser source (10), a first acousto-optic modulator (20), an erbium-doped optical fiber amplifier (40), a second acousto-optic modulator (30) and a circulator (50) which are sequentially connected in series, a sensing optical fiber (60) and a data acquisition card (70),

the circulator (50) is provided with a first port, a second port and a third port, the output end of the second acousto-optic modulator (30) is connected with the first port of the circulator (50), the second port of the circulator (50) is connected with the sensing optical fiber (60), and the third port of the circulator (50) is connected with the data acquisition card (70);

the first acousto-optic modulator (20) is used for modulating the light emitted by the laser source (10) to generate a first optical pulse signal, and the second acousto-optic modulator (30) is used for modulating the first optical pulse signal to generate a second optical pulse signal, and the carrier frequency of the second optical pulse signal is smaller than or equal to 10MHz.

2. The distributed fiber optic vibration monitoring apparatus of claim 1,

the first acousto-optic modulator (20) is in a positive frequency shift working state, and the second acousto-optic modulator (30) is in a negative frequency shift working state; alternatively, the first and second liquid crystal display panels may be,

the first acousto-optic modulator (20) is in a negative frequency shift operating state, and the second acousto-optic modulator (30) is in a positive frequency shift operating state.

3. The distributed fiber vibration monitoring apparatus according to claim 1 or 2, further comprising a first branch (80) and two second branches (90), wherein a first end of the first branch (80) is connected to the data acquisition card (70), first ends of the two second branches (90) are both connected to a second end of the first branch (80), a second end of one of the second branches (90) is connected to the first acousto-optic modulator (20), and a second end of the other second branch (90) is connected to the second acousto-optic modulator (30), so as to control the optical signals output by the first acousto-optic modulator (20) and the second acousto-optic modulator (30) through the data acquisition card (70).

4. The distributed fiber optic vibration monitoring device of claim 3, further comprising:

a DDS signal generator (100) disposed at a junction between the first branch (80) and the second branch (90);

an operational amplifier (110) disposed on the first branch (80); the data acquisition card (70) is connected with the DDS signal generator (100) through the operational amplifier (110).

5. The distributed fiber optic vibration monitoring device of claim 4, further comprising a delay cable (120);

the delay cable (120) is arranged between the DDS signal generator (100) and the first acousto-optic modulator (20); and/or the presence of a gas in the atmosphere,

the delay cable (120) is arranged between the DDS signal generator (100) and the second acousto-optic modulator (30).

6. The distributed fiber optic vibration monitoring device of claim 4, further comprising:

a first driving unit (130) provided between the DDS signal generator (100) and the first acousto-optic modulator (20);

and a second drive unit (140) provided between the DDS signal generator (100) and the second acousto-optic modulator (30).

7. A distributed fibre optic vibration monitoring apparatus as claimed in claim 1 or 2 further comprising a first coupler (150) and a second coupler (160);

the laser source (10) is connected to an input of the first coupler (150), a first output of the first coupler (150) is connected to the first acousto-optic modulator (20), and a second output of the first coupler (150) is connected to a first input of the second coupler (160);

and a third port of the circulator (50) is connected with a second input end of the second coupler (160), and an output end of the second coupler (160) is connected with the data acquisition card (70).

8. A distributed fibre optic vibration monitoring device according to claim 7, further comprising an electrical signal amplifier (170), the electrical signal amplifier (170) being disposed between the second coupler (160) and the data acquisition card (70).

9. The distributed fiber optic vibration monitoring device of claim 8, further comprising:

a photodetector (180) disposed between the second coupler (160) and the electrical signal amplifier (170); and/or the presence of a gas in the gas,

a filter (190) arranged between said electrical signal amplifier (170) and said data acquisition card (70).

10. The distributed fiber optic vibration monitoring device of claim 7, further comprising:

a variable optical attenuator (200) disposed between the first coupler (150) and the second coupler (160); and/or the presence of a gas in the gas,

an optical filter (210) disposed between the third port of the circulator (50) and the second coupler (160).

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