CN111912516A - Phase-synchronized optical fiber distributed vibration measurement device, driver and method - Google Patents
Phase-synchronized optical fiber distributed vibration measurement device, driver and method Download PDFInfo
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Abstract
The utility model provides a phase synchronization's optic fibre distributed vibration measuring device, driver and method, including: the device comprises a double-path clock source, a signal conditioner, a programmable gate array and an acousto-optic modulator driver which are sequentially connected, wherein the double-path clock source is also connected with one end of an amplifier, and the other end of the amplifier is connected with the acousto-optic modulator driver; the dual-path clock source transmits a modulation clock signal to the acousto-optic modulator driver through the amplifier, and transmits a pulse excitation signal to the acousto-optic modulator driver through the signal conditioner and the programmable gate array; the programmable gate array simultaneously outputs trigger signals synchronous with the pulse excitation signals; in each pulse period, the initial phase of the pulse modulation signal is fixed and unchanged, and slight jitter along a time axis does not exist, so that the vibration measurement precision and the spatial resolution can be improved.
Description
Technical Field
The disclosure relates to a phase-synchronized optical fiber distributed vibration measurement device, a phase-synchronized optical fiber distributed vibration measurement driver and a phase-synchronized optical fiber distributed vibration measurement method, which can be used for an optical fiber distributed vibration measurement system to realize high-precision measurement of external environment vibration.
Background
for-OTDR systems, the accuracy of the phase measurement can significantly affect the vibration measurement accuracy and spatial resolution of the system. On one hand, the existing system improves the stability of light wave frequency and reduces the phase noise of a light source by improving laser materials, keeping the environmental temperature and humidity and atmospheric pressure stable and the like; on the other hand, the adverse effects of the optical wave phase noise on the vibration measurement accuracy and spatial positioning are suppressed by an appropriate data processing method.
However, the existing system has little attention to the phase noise carried by the pulse light. In the process of generating pulse light by using the acousto-optic modulator with modulation, as the pulse excitation source and the modulation clock source are from different clocks and a phase asynchronism phenomenon exists, random noise exists in the initial phase of measurement data, and the vibration measurement precision and the spatial resolution are seriously restricted.
Specifically, the acousto-optic modulator adds a pulse modulation signal to an input optical signal under the combined action of a modulation clock signal and a pulse excitation signal, so that the frequency of the input optical signal is shifted, continuous light is converted into pulsed light, and the pulsed optical signal with modulation (frequency shift) is output. It should be added that the modulation clock signal can also be provided from the interior of the acousto-optic modulator, and only the external pulse excitation signal is needed to realize the modulation function.
fAOMTo modulate the frequency of the clock signal, in general, fAOMThe power is in dozens of MHz magnitude, and common specifications comprise 40MHz, 80MHz, 120MHz and the like; corresponding to a pulse excitation signal frequency of
T represents the period of the pulsed excitation signal, fPULSEOn the order of a few kHz to a few tens of kHz, taking as an example a sensing fiber with a length of 10km, fPULSEAnd may be chosen to be 5 kHz. To ensure as much as possible phase synchronization of the pulse excitation signal and the modulated clock signal, fPULSENeeds to be exactly fAOMBy integer multiples of (i.e. frequency division)
N is a positive integer.
However, in the existing system, the pulse excitation source and the modulation clock source are from different clocks, and a phase asynchronous phenomenon exists, so that fPULSEIs not exactly equal to
The slight frequency difference can cause random noise to exist in the pulse light initial phase of the band modulation pulse light signal output by the acousto-optic modulator in each pulse period, as shown in fig. 4, and the vibration measurement precision and the spatial resolution are severely restricted.
Inside the acousto-optic modulator, a pulse excitation source is used for cutting off the modulation clock source to obtain a pulse modulation signal. Although the pulse modulation signals with different pulse periods have the same frequency, the pulse modulation signals are all fAOMBut due to fPULSEIs not exactly equal to
So that the pulse modulation signals have difference in the initial phases of different pulse periods, resulting in slight jitter of the waveform in the time domain along the time axis. Furthermore, the frequency offsets of the modulated pulse light signals in different pulse periods are all fAOMHowever, noise exists in the initial phase, and the vibration measurement precision and the spatial resolution are severely limited.
In fig. 4, when the solid line, the dotted line, and the dash-dot line represent different pulse periods, respectively, a pulse-modulated signal is obtained by cutting off the modulation clock source by using a pulse excitation source inside the acousto-optic modulator. Although the pulse modulation signals with different pulse periods have the same frequency, the pulse modulation signals are all fAOMBut due to fPULSEIs not exactly equal to
So that the pulse modulation signals have difference in the initial phases of different pulse periods, resulting in slight jitter of the waveform in the time domain along the time axis. Furthermore, the frequency offsets of the modulated pulse light signals in different pulse periods are all fAOMHowever, noise exists in the initial phase, and the vibration measurement precision and the spatial resolution are severely limited.
Disclosure of Invention
In order to solve the technical problem, the present disclosure provides a phase-synchronized optical fiber distributed vibration measurement apparatus, a driver and a method.
In a first aspect, the present disclosure provides a phase synchronization driver for fiber optic distributed vibration measurement, comprising: the device comprises a double-path clock source, a signal conditioner, a programmable gate array and an acousto-optic modulator driver which are sequentially connected, wherein the double-path clock source is also connected with one end of an amplifier, and the other end of the amplifier is connected with the acousto-optic modulator driver;
the dual-path clock source transmits a modulation clock signal to the acousto-optic modulator driver through the amplifier, and transmits a pulse excitation signal to the acousto-optic modulator driver through the signal conditioner and the programmable gate array; the programmable gate array simultaneously outputs a trigger signal synchronized with the pulse excitation signal.
In a second aspect, the present disclosure also provides a phase-synchronized optical fiber distributed vibration measurement apparatus, including: the phase synchronization driver according to the first aspect, which comprises a laser, a splitter, an acousto-optic modulator, an optical amplifier, a circulator, an optical balance detector, a data acquisition card and a processor, which are connected in sequence; the phase synchronization driver is connected with the acousto-optic modulator and the data acquisition card; an acousto-optic modulator driver of the phase synchronization driver generates a pulse modulation signal and transmits the pulse modulation signal to the acousto-optic modulator; the programmable gate array transmits a trigger signal to the data acquisition card so that the phases are synchronized.
In a third aspect, the present disclosure also provides a method of using the optical fiber distributed vibration measurement apparatus according to the second aspect, including:
the laser outputs continuous light to the splitter; an acousto-optic modulator driver of the phase synchronization driver generates a pulse modulation signal and transmits the pulse modulation signal to the acousto-optic modulator;
the splitter divides the continuous light into two paths, wherein one path of continuous light is transmitted to the acousto-optic modulator, the acousto-optic modulator converts the continuous light into pulse light by receiving a pulse modulation signal of the phase synchronization driver, the pulse light enters the optical fiber after passing through the amplifier and the circulator, and backward Rayleigh scattered light generated in the optical fiber enters the light balance detector after passing through the circulator again; the other path of continuous light is used as reference light to be transmitted to the light balance detector;
the optical balance detector generates an electric eliminating coherent signal through the reference light and the backward Rayleigh scattering light and transmits the electric eliminating coherent signal to the data acquisition card;
the data acquisition card generates a digital signal by receiving a trigger signal and a static elimination coherent signal of the phase synchronization driver and transmits the digital signal to the processor;
the processor performs data processing on the digital signal to acquire environmental vibration information along the optical fiber.
Compared with the prior art, this disclosure possesses following beneficial effect:
1. the modulation clock signal and the pulse excitation signal of the acousto-optic modulator driver are both from a double-channel clock source and originate from the same clock, so that the modulation clock signal and the pulse excitation signal have complete phase synchronization characteristics, the problems that random noise exists in the initial phase of measured data due to the existence of phase asynchronism and the vibration measurement precision and the spatial resolution are seriously restricted are solved, the initial phase of the pulse modulation signal is fixed and unchanged in each pulse period, slight jitter along a time axis does not exist, and the vibration measurement precision and the spatial resolution can be improved.
2. The phase synchronization driver outputs one path of trigger signal to the high-speed data acquisition card, so that the initial time of data acquisition is synchronous with the phase of pulse light, and the problem of f is solvedPULSEIs not exactly equal to
The method has the advantages that the initial phases of the pulse modulation signals in different pulse periods are different, so that the waveform has slight jitter along the time axis in the time domain, phase noise caused by the fact that the data acquisition card clock and the pulse light clock are asynchronous in the data acquisition process is eliminated, slight jitter along the time axis does not exist, and data acquisition precision is improved.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is a block diagram of an optical fiber distributed vibration measurement device of the present disclosure;
FIG. 2 is a block diagram of a phase locked drive of the present disclosure;
FIG. 3(a) is a graph of a continuous light waveform emitted by a laser of the present disclosure;
FIG. 3(b) is a waveform diagram of a pulse excitation signal input by the driver of the acousto-optic modulator according to the present disclosure;
FIG. 3(c) is a waveform diagram of a modulation clock signal input by the driver of the acousto-optic modulator of the present disclosure;
FIG. 3(d) is a waveform diagram of a pulse modulation signal output by the driver of the acousto-optic modulator of the present disclosure;
FIG. 3(e) is a diagram of the waveform of pulsed light output by the acousto-optic modulator of the present disclosure;
FIG. 4 is a waveform diagram of an acousto-optic modulator internal pulse modulation signal with different pulse periods in the prior art.
The specific implementation mode is as follows:
the present disclosure is further described with reference to the following drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. 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 application belongs.
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 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.
The noun explains:
optical fiber distributed vibration measurement:
the optical fiber distributed vibration measurement system is an optical instrument which takes optical fibers as sensing media to measure environmental vibration. The optical fiber distributed vibration measurement technology realizes the detection of environmental vibration and the transmission of a measured signal simultaneously by using a single optical fiber, integrates sensing and sensing, and comprehensively realizes the vibration measurement and the space positioning functions by using the backward Rayleigh scattering effect in the optical fiber and the optical time domain reflection measurement technology. The optical fiber distributed vibration measurement technology can continuously measure the vibration distribution condition along the optical fiber, and is particularly suitable for long-distance, large-range, high-precision and multipoint vibration real-time measurement.
The most common implementation means of optical fiber distributed vibration measurement is phase-sensitive optical time domain reflectometry (-OTDR), which is divided into two basic forms: direct detection and coherent detection.
In the direct detection structure, a narrow linewidth laser is adopted to generate strong coherent continuous light with stable central frequency, the strong coherent continuous light is modulated by an acousto-optic modulator to generate pulse light to enter a sensing optical fiber, returned Rayleigh scattering light is directly received by a photoelectric detector, and then the detection result is subjected to data processing such as accumulation average and the like to realize vibration detection. The direct detection structure does not demodulate and extract the phase of the Rayleigh scattering light, but performs vibration detection by using the variation of Rayleigh scattering light intensity caused by vibration, has large noise, needs to perform accumulated average or moving difference to perform denoising, and has a nonlinear relation between the variation of the intensity of the Rayleigh scattering light and the amplitude of external vibration, so that the distortion phenomenon can occur when the vibration trend is reduced by the variation of the intensity. The coherent detection method detects and reduces the vibration through the phase change of the rayleigh scattering light, and is more and more favored by people due to the advantages of high signal-to-noise ratio, linear relationship between the phase change and the vibration amplitude, and the like.
Optical Time Domain Reflectometry (OTDR) techniques:
according to the principle of backward scattering of light and Fresnel backward direction, the information of energy (amplitude) attenuation is obtained by utilizing the backward scattering light waves generated when the pulse light waves are transmitted in the optical fiber, the method can be used for measuring the optical fiber attenuation, the joint loss, the positioning of the fault point of the optical fiber, knowing the loss distribution condition of the optical fiber along the length and the like, and is an essential technology in the construction, maintenance and monitoring of the optical cable.
Phase sensitive optical time domain reflectometry (-OTDR) techniques:
the method is developed on the basis of OTDR technology, and comprises injecting light pulse into sensing fiber from one end of the fiber, and detecting backward Rayleigh scattered light generated when pulse light wave propagates in the fiber by using a detector. Since the injected light is strongly coherent (also known as "narrow linewidth", or "low phase noise"), the output of the detector is an interference signal of the coherence of the rayleigh scattered light reflected back within the pulse width region. When vibration events occur on the optical fiber along the line, the refractive index of the optical fiber at the corresponding position is changed, and the intensity and the phase of Rayleigh scattering light at the position are changed due to the elasto-optical effect.
The modulation clock signal of the acousto-optic modulator can be expressed as:
xm(t)＝Amcos(2πfAOMt+φ0) (1)
wherein A ismFor modulating the amplitude of the clock signal, fAOMFor modulating the frequency of the clock signal, phi0To modulate the initial phase of the clock signal, t represents time.
The pulsed excitation signal of the acousto-optic modulator can be expressed as:
wherein A ispRepresenting the high level amplitude of the pulsed excitation signal, T representing the period of the pulsed excitation signal, corresponding to a pulsed excitation signal frequency of
T1Denotes the duration of the high level of the pulse excitation signal, k is 0, and 1,2,3,4,5, … denote integers.
Example 1
As shown in fig. 2, the present disclosure provides a phase-synchronized driver for fiber-optic distributed vibration measurement, comprising: the two-way clock source, the signal conditioner, the Field Programmable Gate Array (FPGA) and the acousto-optic modulator driver are sequentially connected, the two-way clock source is also connected with one end of the amplifier, and the other end of the amplifier is connected with the acousto-optic modulator driver; the dual-path clock source transmits a modulation clock signal to the acousto-optic modulator driver through the amplifier, and transmits a pulse excitation signal to the acousto-optic modulator driver through the signal conditioner and the programmable gate array; the programmable gate array simultaneously outputs a trigger signal synchronized with the pulse excitation signal.
Furthermore, the two-way clock source generates two-way clock signals, wherein one way of clock signals is transmitted to the amplifier, and after power amplification, the clock signals are output to a clock port of the acousto-optic modulator driver as modulation clock signals; the other path of clock signal is transmitted to a signal conditioner, and is transmitted to a programmable gate array after level and amplitude adjustment is carried out; under the action of clock signal, the programmable gate array generates pulse excitation signal with adjustable duty ratio and frequency, and transmits the pulse excitation signal to the pulse modulation port of the acousto-optic modulator driver. The acousto-optic modulator driver generates a dot frequency excitation signal with pulse modulation according to the modulation clock signal and the pulse excitation signal, and the dot frequency excitation signal is used for driving the acousto-optic modulator.
Specifically, the two-way clock source generates the frequency fAOMOne of the two clock signals is transmitted to an amplifier, and after power amplification, the two clock signals are used as modulation clock signals and output to a clock port of a driver of the acousto-optic modulator, and the waveform is shown in fig. 3 (c); and the other path of the signal is output to a signal conditioner, and is output to the FPGA as a clock signal after level and amplitude adjustment is carried out.FPGA at frequency fAOMUnder the action of the clock, generating duty ratio and frequency (f)PULSE) The adjustable pulse excitation signal is output to the pulse modulation port of the acousto-optic modulator driver, and the waveform is shown in fig. 3 (b). The acousto-optic modulator driver generates a frequency f with pulse modulation under the action of a modulation clock signal and a pulse excitation signalAOMThe dot frequency excitation signal of (2) drives the acousto-optic modulator as a pulse modulation signal, and the waveform is shown in fig. 3 (d).
Because the modulation clock signal and the pulse excitation signal are both from a double-channel clock source and originate from the same clock, the modulation clock signal and the pulse excitation signal have complete phase synchronization characteristics, and the initial phase of the pulse modulation signal is fixed and unchanged in each pulse period without slight jitter along a time axis.
The FPGA simultaneously outputs a trigger signal synchronous with the pulse excitation signal, and the trigger signal is sent to the high-speed data acquisition card to be used as an acquisition data initial mark signal, so that the sampling time of the data acquisition card is synchronous with the pulse light initial time, and the acquisition precision is improved.
Example 2
As shown in fig. 1, the present disclosure provides a phase-synchronized fiber optic distributed vibration measurement device, comprising: the device comprises a laser, a branching unit, an acousto-optic modulator, an optical amplifier, a circulator, an optical balance detector, a data acquisition card and a processor which are connected in sequence; the data acquisition card is connected with one port of the phase synchronous driver, and the other port of the phase synchronous driver is connected with the acousto-optic modulator; the circulator is also connected with an optical fiber;
the phase synchronization driver generates a modulation clock signal, a pulse excitation signal and a trigger signal synchronous with the pulse excitation signal; generating a pulse modulation signal by modulating a clock signal and a pulse excitation signal and transmitting the pulse modulation signal to an acousto-optic modulator; and the trigger signal is transmitted to the data acquisition card, so that the sampling time of the data acquisition card is synchronous with the phase of the pulse light starting time.
Further, the splitter is also connected with the light balance detector; the laser emits continuous light, the splitter divides the continuous light into two paths, one path of continuous light is converted into pulse light through the acousto-optic modulator with the frequency shift function, the pulse light enters the first port 1 of the circulator after being subjected to power compensation through the optical amplifier, and the pulse light is emitted into the optical fiber through the third port 3 of the circulator; and the other path of continuous light is transmitted to the light balance detector as reference light.
The backward rayleigh scattered light generated in the optical fiber passes through the circulator third port 3 again and exits the circulator second port 2 into the light balance detector.
The optical balance detector generates an electric eliminating coherent signal through the reference light and the backward Rayleigh scattering light and transmits the electric eliminating coherent signal to the data acquisition card; the data acquisition card generates a digital signal through the trigger signal and the electricity eliminating coherent signal and transmits the digital signal to the processor; the processor performs data processing on the digital signal to acquire environmental vibration information along the optical fiber.
Specifically, the laser emits continuous light with narrow line width and light wave frequency v0The amplitude waveform is divided into two paths through a splitter with a specific power ratio as shown in fig. 3(a), wherein one path of continuous light passes through an acousto-optic modulator with a frequency shift function, and the modulation frequency is fAOMConverted into pulse light with specific width and period, and the light wave frequency is v0+fAOMThe pulse weight frequency is fPULSEAnd the amplitude waveform is as shown in fig. 3(e), enters the port of the circulator 1 after being subjected to power compensation through the optical amplifier, then exits through the port of the circulator 3 and enters the sensing optical fiber to obtain vibration measurement information along the optical fiber, and backward rayleigh scattered light which is generated in the sensing optical fiber and carries environmental vibration information passes through the port of the circulator 3 again and exits from the port of the circulator 2.
The other path of continuous light divided after the continuous light emitted by the light source passes through the splitter with a specific power ratio is used as local reference light, and the optical frequency is v0. The backward Rayleigh scattered light emitted from the local reference light and the port 2 of the circulator passes through the optical balance detector to generate light wave frequency v0Retaining only the modulation frequency fAOMThe electrical coherent signals enter a high-speed data acquisition card, and the obtained digital signals are subjected to data processing in a processor to obtain environmental vibration information along the optical fiber.
The phase synchronous driver consists of a double-path clock source, a signal conditioner, a Field Programmable Gate Array (FPGA), an amplifier and an acousto-optic modulator driver. Two-way clock source generating frequency fAOMOne of the two clock signals is transmitted to an amplifier, and after power amplification, the two clock signals are used as modulation clock signals and output to a clock port of a driver of the acousto-optic modulator, and the waveform is shown in fig. 3 (c); and the other path of the signal is output to a signal conditioner, and is output to the FPGA as a clock signal after level and amplitude adjustment is carried out. FPGA at frequency fAOMUnder the action of the clock, generating duty ratio and frequency (f)PULSE) The adjustable pulse excitation signal is output to the pulse modulation port of the acousto-optic modulator driver, and the waveform is shown in fig. 3 (b). The acousto-optic modulator driver generates a frequency f with pulse modulation under the action of a modulation clock signal and a pulse excitation signalAOMThe dot frequency excitation signal of (2) drives the acousto-optic modulator as a pulse modulation signal, and the waveform is shown in fig. 3 (d).
It should be noted that, since the modulation clock signal and the pulse excitation signal are both from a dual clock source and originate from the same clock, the modulation clock signal and the pulse excitation signal have a complete phase synchronization characteristic, and the initial phase of the pulse modulation signal is fixed and does not have slight jitter along the time axis in each pulse period.
The FPGA simultaneously outputs a trigger signal synchronous with the pulse excitation signal, and the trigger signal is sent to the high-speed data acquisition card to be used as an acquisition data initial mark signal, so that the sampling time of the data acquisition card is synchronous with the pulse light initial time, and the acquisition precision is improved.
Example 3
The present disclosure also provides a method for using the phase-synchronized optical fiber distributed vibration measurement apparatus according to the above embodiment, including:
the laser outputs continuous light to the splitter; an acousto-optic modulator driver of the phase synchronization driver generates a pulse modulation signal and transmits the pulse modulation signal to the acousto-optic modulator;
the splitter divides the continuous light into two paths, wherein one path of continuous light is transmitted to the acousto-optic modulator, the acousto-optic modulator converts the continuous light into pulse light by receiving a pulse modulation signal of the phase synchronization driver, and the pulse light enters the optical fiber after passing through the amplifier and the circulator; the other path of continuous light is used as reference light to be transmitted to the light balance detector;
backward Rayleigh scattered light generated in the optical fiber enters the light balance detector after passing through the circulator again;
the optical balance detector generates an electric eliminating coherent signal through the reference light and the backward Rayleigh scattering light and transmits the electric eliminating coherent signal to the data acquisition card;
the data acquisition card generates a digital signal by receiving a trigger signal and a static elimination coherent signal of the phase synchronization driver and transmits the digital signal to the processor;
the processor performs data processing on the digital signal to acquire environmental vibration information along the optical fiber.
Specifically, in step 1, the laser outputs continuous light with a wavelength of 1550nm or 1330 nm:
wherein A represents the optical wave amplitude v0Representing the frequency of the optical wave, is a constant 193.5THz (corresponding to a wavelength of 1550 nm) or 229.0THz (corresponding to a wavelength of 1310 nm), and t represents time.
The continuous light amplitude waveform emitted by the laser is shown in fig. 3 (a).
And 2, dividing the laser continuous light into two paths, wherein one path of continuous light is converted into pulse light with specific width and period through an acousto-optic modulator with a frequency shift function:
wherein the content of the first and second substances,
representing a rectangular function, T representing the pulse period, the corresponding pulse repetition frequency being
T1Denotes the duration of the pulse high level, k is 0,1,2,3,4,5, … denotes an integer, fAOMIndicating the modulation clock frequency, phi, of the acousto-optic modulator0Indicating the pulse light starting phase for each pulse repetition period.
The pulse light amplitude waveform output from the acousto-optic modulator is shown in fig. 3 (e).
In the traditional device, because the pulse excitation source and the modulation clock source are from different clocks, a phase asynchronism phenomenon exists, and phi is caused0The values at each pulse repetition period are different, random noise exists, and vibration measurement precision and spatial resolution are severely restricted. In the device, the modulation clock signal and the pulse excitation signal of the acousto-optic modulator driver are both from a double-channel clock source, and the phase asynchronism phenomenon does not exist, so that the initial phase phi of the output pulse modulation signal0The value of each pulse repetition period is fixed, so that the phase stability of pulsed light is improved, and the vibration measurement precision and the spatial resolution of the system are improved.
And 3, performing power compensation on the pulse light through an optical amplifier, enabling the pulse light to enter a port 1 of the circulator, enabling the pulse light to exit through a port 3 of the circulator and enter a sensing optical fiber, acquiring vibration measurement information along the optical fiber, and enabling backward Rayleigh scattering light carrying environmental vibration information generated in the sensing optical fiber to pass through a port 3 of the circulator again and exit from a port 2 of the circulator.
And 4, taking another path of continuous light which is split after the continuous light emitted by the light source passes through the splitter with the specific power ratio as local reference light. The backward Rayleigh scattered light emitted from the local reference light and the port 2 of the circulator passes through the optical balance detector to generate light wave frequency v0Retaining only the modulation frequency fAOMThe electrical coherent signals enter a high-speed data acquisition card.
And 5, the high-speed data acquisition card uses a trigger signal synchronous with the pulse excitation signal as an acquisition data initial mark signal to synchronize the sampling time with the pulse light initial time, improve the acquisition precision and send the digital signal to the processor.
And 6, eliminating the influence of the phase drift of the laser on the measurement result by the processor by using a secondary difference method to obtain the environmental vibration measurement data.
Specifically, when the detected environment vibrates, the sensing optical fibers behind the vibration point carry vibration information due to the influence of the vibration event, and the sensing optical fibers in front of the vibration point do not carry vibration information. Therefore, the points A and B with the distance of DAB can be selected, and the adverse effect on the measurement caused by the phase noise of the laser is eliminated primarily through phase difference, wherein the point A carries vibration information after the vibration point, and the point B does not carry vibration information before the vibration point. Further, a point C and a point D which are separated by DCD before the vibration point are selected, and phase difference is performed, so that C, D phase change information between the two points can be obtained. By calculating the proportional relation between the distances DAB and DCD, the influence of residual laser phase noise on the performance of a sensing system can be further eliminated, the measurement phase drift caused by frequency drift can be compensated in real time, and the measurement precision of the external vibration signal can be further improved.
Although the present disclosure has been described with reference to specific embodiments, it should be understood that the scope of the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present disclosure.
Claims (10)
1. A fiber optic distributed vibration measuring phase synchronous drive, comprising: the device comprises a double-path clock source, a signal conditioner, a programmable gate array and an acousto-optic modulator driver which are sequentially connected, wherein the double-path clock source is also connected with one end of an amplifier, and the other end of the amplifier is connected with the acousto-optic modulator driver;
the dual-path clock source transmits a modulation clock signal to the acousto-optic modulator driver through the amplifier, and transmits a pulse excitation signal to the acousto-optic modulator driver through the signal conditioner and the programmable gate array; the programmable gate array simultaneously outputs a trigger signal synchronized with the pulse excitation signal.
2. The phase locked driver of claim 1, wherein the dual clock source generates two clock signals, one of which is transmitted to the amplifier, power amplified, and output as a modulated clock signal to the clock port of the acousto-optic modulator driver.
3. The phase locked driver of claim 2 wherein the other clock signal is transmitted to the signal conditioner for level and amplitude adjustment and then to the programmable gate array.
4. The phase locked driver of claim 3 wherein the programmable gate array generates the pulse excitation signal with adjustable duty cycle and frequency for transmission to the pulse modulation port of the acousto-optic modulator driver under the influence of the clock signal.
5. The phase locked driver of claim 1, wherein the acousto-optic modulator driver generates a dot frequency excitation signal with pulse modulation for driving the acousto-optic modulator based on the modulation clock signal and the pulse excitation signal.
6. A phase synchronized fiber optic distributed vibration measuring device comprising: the phase synchronization driver as claimed in any one of claims 1 to 5, which comprises a laser, a splitter, an acousto-optic modulator, an optical amplifier, a circulator, an optical balance detector, a data acquisition card and a processor, which are connected in sequence; the phase synchronization driver is connected with the acousto-optic modulator and the data acquisition card; an acousto-optic modulator driver of the phase synchronization driver generates a pulse modulation signal and transmits the pulse modulation signal to the acousto-optic modulator; the programmable gate array transmits a trigger signal to the data acquisition card so that the phases are synchronized.
7. The fiber optic distributed vibration measurement device of claim 6 wherein said splitter is further connected to an optical balance detector; the laser emits continuous light, the splitter divides the continuous light into two paths, one path of continuous light is converted into pulse light through the acousto-optic modulator with the frequency shift function, the pulse light enters a first port of the circulator after being subjected to power compensation through the optical amplifier, and the pulse light is emitted into the optical fiber through a third port of the circulator; and the other path of continuous light is transmitted to the light balance detector as reference light.
8. The fiber optic distributed vibration measuring device of claim 7 wherein backward rayleigh scattered light generated in the optical fiber passes again through the circulator third port and exits the circulator second port into the optical balance detector.
9. The optical fiber distributed vibration measuring device according to claim 8, wherein the optical balance detector generates an electric eliminating coherent signal by the reference light and the backward rayleigh scattering light, and transmits the electric eliminating coherent signal to the data acquisition card; the data acquisition card generates a digital signal through the trigger signal and the electricity eliminating coherent signal and transmits the digital signal to the processor; the processor performs data processing on the digital signal to acquire environmental vibration information along the optical fiber.
10. A method of using a fibre optic distributed vibration measurement device according to any of claims 6 to 9, comprising:
the laser outputs continuous light to the splitter; an acousto-optic modulator driver of the phase synchronization driver generates a pulse modulation signal and transmits the pulse modulation signal to the acousto-optic modulator;
the splitter divides the continuous light into two paths, wherein one path of continuous light is transmitted to the acousto-optic modulator, the acousto-optic modulator converts the continuous light into pulse light by receiving a pulse modulation signal of the phase synchronization driver, the pulse light enters the optical fiber after passing through the amplifier and the circulator, and backward Rayleigh scattered light generated in the optical fiber enters the light balance detector after passing through the circulator again; the other path of continuous light is used as reference light to be transmitted to the light balance detector;
the optical balance detector generates an electric eliminating coherent signal through the reference light and the backward Rayleigh scattering light and transmits the electric eliminating coherent signal to the data acquisition card;
the data acquisition card generates a digital signal by receiving a trigger signal and a static elimination coherent signal of the phase synchronization driver and transmits the digital signal to the processor;
the processor performs data processing on the digital signal to acquire environmental vibration information along the optical fiber.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114356136A (en) * | 2021-12-27 | 2022-04-15 | 北京奕斯伟计算技术有限公司 | Method for synchronously detecting induction signals among chips, driving device and touch device |
| CN114719952A (en) * | 2022-03-23 | 2022-07-08 | 武汉理工大学 | Distributed optical fiber sound wave detection system and detection method |
| CN116699398A (en) * | 2023-05-29 | 2023-09-05 | 武汉莱创德技术有限公司 | Novel high-efficient toggle test platform |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114356136A (en) * | 2021-12-27 | 2022-04-15 | 北京奕斯伟计算技术有限公司 | Method for synchronously detecting induction signals among chips, driving device and touch device |
| CN114356136B (en) * | 2021-12-27 | 2024-01-26 | 北京奕斯伟计算技术股份有限公司 | Method for synchronously detecting sensing signals among chips, driving device and touch device |
| CN114719952A (en) * | 2022-03-23 | 2022-07-08 | 武汉理工大学 | Distributed optical fiber sound wave detection system and detection method |
| CN116699398A (en) * | 2023-05-29 | 2023-09-05 | 武汉莱创德技术有限公司 | Novel high-efficient toggle test platform |
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