CN111678584A - Optical fiber vibration measuring device with light source frequency shift calibration auxiliary channel and method - Google Patents
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Abstract
The invention provides an optical fiber vibration measurement device with a light source frequency shift calibration auxiliary channel and a method, which relate to the field of optical fiber distributed vibration measurement
The auxiliary channel of the measuring device is used for completely compensating the frequency drift of the light source and eliminating the phase noise of the laser, two mutually orthogonal interference optical signals are obtained based on an interferometer and a 90-degree optical mixer in a feedforward loop of a light source noise suppression feedforward structure and are respectively output to the photoelectric balance detector 1 and the photoelectric balance detector 2 and are converted into two interference electric signals; the influence of the random change of the initial phase of the optical frequency on the measurement result existing when the optical frequency drift amount is measured based on the single-path signal is avoided, and the measurement precision of the external vibration signal is improved.
Description
Technical Field
The disclosure relates to the field of optical fiber distributed vibration measurement, in particular to an optical fiber vibration measurement device with a light source frequency shift calibration auxiliary channel and a method.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The optical time domain reflection measurement technology is an essential technology in optical cable construction, maintenance and monitoring, and is based on the principle of backward scattering and Fresnel reverse of light, and utilizes the backward scattering light wave generated when pulse light wave propagates in an optical fiber to obtain the information of energy (amplitude) attenuation, so that the optical time domain reflection measurement technology can be used for measuring the optical fiber attenuation, joint loss, optical fiber fault point positioning, knowing the loss distribution condition of the optical fiber along the length and the like.
With the continuous improvement of measurement techniques, phase-sensitive optical time-domain reflectometry, for example, has emerged
The technology,
Vibration measurement technique and based on quadratic difference
A method of measurement;
the inventors found that
For the system, the phase noise of the laser can reduce the measurement accuracy of the system and the spatial resolution of the system. Therefore, it is important to improve the phase noise of the optical wave. On one hand, the stability of the optical wave frequency can be improved and the phase noise can be reduced by improving the laser material, keeping the environmental temperature and humidity and the atmospheric pressure stable and the like; however, on the basis of the existing laser manufacturing process and constant temperature, humidity and pressure treatment technology, the technology is not a technical method which is easy to realize in a short period of time; on the other hand, the adverse effects of the optical wave phase noise on the vibration measurement accuracy and spatial positioning can be suppressed by designing a new optical path structure and a data processing method, such as quadratic difference-based, for a digital signal processing method
The measurement method is limited by the valid bit (quantization noise) of the data acquisition card, and the digital signal processing method is only a method for processing the digital signal and does not fundamentally reduce the phase noise of the laser, so that the measurement precision of the external vibration signal is difficult to further improve.
Disclosure of Invention
The present disclosure is directed to a method and an apparatus for measuring fiber vibration with a frequency shift calibration auxiliary channel of a light source, which is added to a conventional phase-sensitive optical time domain reflectometry measuring apparatus to serve as a frequency shift calibration auxiliary channel
The auxiliary channel of the measuring device is used for completely compensating the frequency drift of the light source, eliminating the phase noise of the laser and improving the measuring precision of the external vibration signal.
The first purpose of this disclosure is to provide a take optic fibre vibration measuring device of light source frequency shift calibration auxiliary channel, adopt following technical scheme:
the measuring structure is used for acquiring a first path of continuous light and a second path of continuous light output by the branching unit, the first path of continuous light is processed and then input into the sensing optical fiber through the circulator, backward Rayleigh scattered light which is output by the circulator and carries vibration information is optically coupled with the second path of continuous light, and then the backward Rayleigh scattered light is output to the data acquisition card through the photoelectric detector;
the auxiliary channel is used for acquiring a third path of continuous light output by the splitter, processing the third path of continuous light after sequentially passing through the interferometer and the photoelectric balance detector, extracting phase information and inputting the phase information into the data acquisition card;
and the processor is used for acquiring and processing data in the data acquisition card to obtain the environmental vibration information along the sensing optical fiber.
Furthermore, the interferometer divides the acquired first path of continuous light into two orthogonal interference light signals, and the two interference light signals are respectively input into the first light balance detector and the second light balance detector to be converted into two paths of interference electric signals.
And further, carrying out operation processing on the two paths of interference electric signals, extracting phase information and inputting the phase information into a data acquisition card.
Further, the first continuous light is converted into pulse light with a set width and period through the acousto-optic modulator with a frequency shift, and then enters the sensing optical fiber through the optical amplifier and the circulator.
And further, the second path of continuous light is used as local reference light, couples with Rayleigh scattering light to output interference signals to enter a photoelectric detector, performs frequency reduction processing on the interference signals by taking the frequency offset of the acousto-optic modulator as reference, extracts phase information in the interference signals and outputs the phase information to a data acquisition card.
A second object of the present disclosure is to provide a method for measuring fiber vibration with an auxiliary channel for calibrating frequency shift of a light source, comprising the following steps:
the first path of continuous light output by the branching unit is input into the sensing optical fiber through a circulator after being subjected to acousto-optic modulation and light amplification, and the circulator outputs backward Rayleigh scattering light with environmental vibration information generated in the sensing optical fiber;
after the Rayleigh scattered light is optically coupled with the second path of continuous light output by the branching unit, the Rayleigh scattered light is input into a data acquisition card through a photoelectric detector;
taking the third path of continuous light output by the splitter as calibration light, entering an auxiliary channel for frequency shift calibration, extracting phase information and inputting the phase information into a data acquisition card;
and processing the data in the data acquisition card to acquire the environmental vibration information along the sensing optical fiber.
Further, the Rayleigh scattering light and the second path of continuous light are coupled to generate an interference signal, the frequency offset of the acousto-optic modulator is used as a reference, the interference signal is subjected to frequency reduction processing, and then phase information in the interference signal is extracted by using Hilbert transform and an inverse tangent method.
Further, the processing process of the third continuous light in the auxiliary channel specifically includes:
obtaining an I path interference signal and a Q path interference signal which are orthogonal with each other through an interferometer;
the I path interference signal is multiplied by the I path original signal after being subjected to time averaging, the Q path interference signal is multiplied by the Q path original signal after being subjected to time averaging, and the obtained two paths of signals are added by an adder;
the signal output from the adder is subjected to hilbert transform and arc tangent operation, and phase information is extracted.
Further, the backward rayleigh scattering light carries the environmental vibration information received by the sensing optical fiber and exits through the port of the circulator.
Further, the laser outputs continuous light, and the continuous light is divided into three paths by the splitter and processed respectively.
Compared with the prior art, the utility model has the advantages and positive effects that:
(1) using frequency-shifted calibration auxiliary channels as
The auxiliary channel of the measuring device is used for completely compensating the frequency drift of the light source, eliminating the phase noise of the laser and further improving the measuring precision of the external vibration signal;
(2) in a feedforward loop of a light source noise suppression feedforward structure, two mutually orthogonal interference optical signals are obtained based on an interferometer and a 90-degree optical mixer and are respectively output to a photoelectric balance detector 1 and a photoelectric balance detector 2 to be converted into two interference electrical signals; the influence of the random change of the initial phase of the optical frequency on the measurement result when the optical frequency drift amount is measured based on the single-path signal is avoided, and the measurement precision of the optical frequency drift is improved, so that the suppression of the phase noise of the light source is facilitated, and the measurement precision of the external vibration signal is improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
Fig. 1 is a schematic diagram of a structure and a flow of optical fiber vibration measurement in embodiments 1 and 2 of the present disclosure;
fig. 2 is a structural diagram of an auxiliary channel in embodiments 1 and 2 of the present disclosure.
Detailed Description
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 disclosure 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 disclosure. As used herein, the singular forms "a", "an", and/or "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;
for convenience of description, the words "up", "down", "left" and "right" in this disclosure, if any, merely indicate that the directions of movement of the device or element in question are in accordance with the directions of movement of the device or element in the drawings themselves, and are not structural limitations, but merely facilitate the description of the invention and simplify the description, rather than indicate or imply that the device or element in question must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the disclosure.
As described in the background, the prior art is twice differenced
The measuring method is a digital signal processing method, is restricted by the effective bit (quantization noise) of a data acquisition card, does not reduce the phase noise of a laser at all, and is difficult to further improve the measuring precision of an external vibration signal; in order to solve the problems, the disclosure provides an optical fiber vibration measurement device with a light source frequency shift calibration auxiliary channel and a method thereof.
Light source noise: the linewidth of the laser cannot be infinitely narrow and there is always some phase noise (otherwise known as "frequency drift"). When pulsed light is transmitted in an optical fiber, the intensity of a backward Rayleigh scattering signal is affected by phase noise of the detected light to generate jitter, so that the signal-to-noise ratio of a measurement signal is reduced, and positioning and measurement errors of a measured vibration signal even fail.
To pair
For a system, the phase noise of the laser may reduce the measurement accuracy of the system and the spatial resolution of the system. Therefore, it is important to improve the phase noise of the optical wave. On one hand, the stability of the optical wave frequency can be improved and the phase noise can be reduced by improving the laser material, keeping the environmental temperature and humidity and the atmospheric pressure stable and the like; on the other hand, the adverse effects of the optical wave phase noise on the vibration measurement precision and the space positioning can be inhibited by designing a new optical path structure and a new data processing method.
For the former, on the basis of the existing laser manufacturing process and constant temperature, humidity and pressure treatment technology, the technology is not a technical method which is easy to realize in a short period; for the latter, a more general method is to use a quadratic difference method, which is an improved method of pure digital signal processing.
Based on quadratic difference
The detailed working principle of the measuring method is as follows:
in the classic
On the basis of the system structure, continuous light emitted by a narrow linewidth laser is divided into two paths through a coupler with a specific power ratio, wherein one path of continuous light is converted into pulse light with a specific width and period through an acousto-Optic Modulator (AOM) with a frequency shift function, the pulse light enters a port of a circulator 1 after being subjected to power compensation through an Optical amplifier (generally, an Erbium Doped Fiber Amplifier (EDFA)), and then enters a sensing Optical fiber through the port of the circulator 3 to obtain vibration measurement information along the Optical fiber, and backward scattered light which carries environmental vibration information and is generated in the sensing Optical fiber passes through the port of the circulator 3 again and exits from the port of the circulator 2.
The other path of continuous light which is branched after the continuous light emitted by the light source passes through the coupler with the specific power ratio is used as local reference light. The local reference light and the backward Rayleigh scattered light emitted from the port of the circulator 2 generate coherent signals through a coupler with the ratio of 50: 50, the coherent signals are converted into electric signals through a photoelectric detector and enter a data acquisition card, the digital signals are obtained, data processing is carried out on the electric signals, and the environmental vibration information along the optical fiber is obtained.
However, based on quadratic differences
The measuring method is a digital signal processing method, does not reduce the phase noise of the laser at all, and does not consider the feasible scheme of improving and suppressing the phase noise of the measurement by the optical path structure.
Example 1
In an exemplary embodiment of the present disclosure, as shown in fig. 1-2, an optical fiber vibration measurement device with an auxiliary channel for calibrating frequency shift of a light source is provided.
The device comprises: the device comprises a laser, a splitter, an acousto-optic modulator, an optical amplifier, a circulator, a sensing optical fiber, a coupler 1, a photoelectric detector 1, a frequency shift calibration auxiliary channel, a photoelectric detector 2, a data acquisition card and a processor.
The laser emits narrow-linewidth continuous light, the narrow-linewidth continuous light is divided into 3 paths through a branching unit, wherein the 1 path of continuous light is converted into pulse light with specific width and period through an acousto-optic modulator with a frequency shift function, the pulse light enters a port 1 of a circulator after being subjected to power compensation through an optical amplifier, the pulse light enters a sensing optical fiber through the exit of the port 3 of the circulator, vibration measurement information along the optical fiber is obtained, backward Rayleigh scattered light carrying environmental vibration information and generated in the sensing optical fiber passes through the port 3 of the circulator again and is emitted from the port 2 of the circulator.
And the 2 nd path of continuous light split after the continuous light emitted by the light source passes through the splitter is used as local reference light. The backward Rayleigh scattered light emitted from the port of the local reference light and the circulator 2 passes through a 50: 50 coupler 1 to generate a coherent signal, the coherent signal is converted into an electric signal through a photoelectric detector and enters a data acquisition card, the electric signal is converted into a digital signal and then is sent to a processor for data processing, and environmental vibration information along the optical fiber is acquired.
And the 3 rd path of continuous light which is divided after the continuous light emitted by the light source passes through the splitter is used as calibration light, enters a frequency shift calibration auxiliary channel to obtain a light source frequency shift electric signal, and is transmitted to the data acquisition card.
The frequency shift calibration auxiliary channel comprises: the optical fiber delay line comprises a coupler 2, a delay optical fiber, a 90-degree optical mixer, a photoelectric balance detector 1, a photoelectric balance detector 2, an averager 1, an averager 2, a multiplier 1, a multiplier 2 and an adder.
The 3 rd path of continuous light output by the coupler 1 entering the frequency shift calibration auxiliary channel is divided into two paths by the coupler 2 with the ratio of 50: 50, wherein one path of continuous light directly enters the 90-degree optical mixer, and the other path of continuous light enters the 90-degree optical mixer through the delay optical fiber. The coupler 2, the transmission optical fiber without the delay optical fiber, the transmission optical fiber with the delay optical fiber, and the 90-degree optical mixer constitute a classical mach-zehnder fiber optic interferometer, and the difference in the length of the interference arms is determined by the delay optical fiber. Based on the Mach-Zehnder optical fiber interferometer, the 90-degree optical mixer obtains two mutually orthogonal interference optical signals, and the two mutually orthogonal interference optical signals are respectively output to the photoelectric balance detector 1(I path) and the photoelectric balance detector 2(Q path) and converted into two interference electric signals. The I path interference electric signal and the Q path interference electric signal respectively pass through the averager 1 and the averager 2, and simultaneously enter the multiplier 1 and the multiplier 2 together with the I path original signal and the Q path original signal, the two multipliers are output to the adder, and the two paths of signals are added and then transmitted to the data acquisition card.
The data acquisition card converts the two paths of input electric signals into digital signals and transmits the digital signals to the processor. The processor performs Hilbert transform on the Rayleigh scattering coherent signal containing the vibration information along the optical fiber environment, and extracts phase information; and one point is selected before and after the vibration point for single phase difference, so that phase noise caused by different initial phases of Rayleigh scattering light and local reference light is eliminated, and the influence of frequency drift of a light source on a measurement signal is reduced.
According to the frequency shift calibration auxiliary signal, further light source frequency drift compensation is carried out on the measurement signal, the influence of the light source frequency drift on the measurement signal is completely eliminated, and the measurement precision of the external vibration signal is improved.
Example 2
In another exemplary embodiment of the present disclosure, as shown in fig. 1-2, a method for measuring fiber vibration with an auxiliary channel for frequency shift calibration of a light source is provided.
The method comprises the following steps:
the laser outputs continuous light at a frequency v0+Δv0(t)，v0Represents the ideal value of the optical wave frequency, is constant, but the optical wave frequency contains a frequency drift component Deltav due to the inevitable noise of the laser0(t), t represents time;
the continuous light of the laser is divided into 3 paths by a splitter, wherein the 1 st path of continuous light is converted into pulse light with specific width and period by an acousto-optic modulator with a frequency shift function, and then enters a sensing optical fiber by an optical amplifier and a circulator to obtain Rayleigh scattering light wave Er(zi，t)，ziIndicating the position of the sensing optical fiber where Rayleigh scattering occurs;
the 2 nd path continuous light is used as local reference light Eref(zref，t)，zrefRepresents a reference pathThe length of the optical fiber of (a);
the Rayleigh scattered light and the local reference light enter the photoelectric detector after interfering in the coupler, and the signal is represented as I (z)i，t)；
Frequency reduction processing is carried out on the interference signal by taking the frequency offset of the acousto-optic modulator as reference, and then phase information in the interference signal is extracted by using a Hilbert transform and anti-tangent method
Step 4, selecting the position z behind the vibration pointAAnd z is the front position of the vibration pointBThe phase difference between the A, B points is obtained to obtain the single difference phase
Wherein D isABIndicating A, B the spacing between the two points,
representing the phase change introduced by the external vibration signal;
phase noise caused by different initial phases of Rayleigh scattering light and local reference light is eliminated;
and, the single differential phase shifts the influence of the light source frequency drift on the measurement signal, from
Reduced to
Continuous light emitted by a light source is divided into a 3 rd path of continuous light serving as calibration light after passing through a splitter, enters a frequency shift calibration auxiliary channel, and is subjected to a classical Mach-Zehnder interferometer to obtain two paths (an I path and a Q path) of orthogonal interference signals;
the I path interference signal is multiplied by the I path original signal after being subjected to time averaging, and the Q path interference signal is multiplied by the Q path original signal after being subjected to time averaging;
then adding the two obtained signals by using an adder;
performing Hilbert transform and arc tangent operation on the signal output by the adder to extract phase information
Wherein the content of the first and second substances,
representing the length difference of an interference arm of a Mach-Zehnder interferometer in the frequency shift calibration auxiliary channel;
a, B according to the distance D between two points in single differenceABAnd the difference D in the lengths of the arms of the Mach-Zehnder interferometer in the sum-frequency-shift calibration auxiliary channelDIFProportional relationship therebetween, determining frequency drift correction coefficient
The frequency drift calibration is carried out on the single differential phase to obtain the external vibration signal measured value with higher precision
Specifically, in this embodiment, the measurement method includes the following steps:
step 1, the laser outputs continuous light with the wavelength of 1550nm or 1330 nm:
E(t)＝A cos(2π(v0+Δv0(t))t) (1)
wherein A represents the amplitude of light waves, v0Representing the ideal value of the optical frequency, is a constant of 193.5THz (corresponding to 1550nm wavelength) or 229.0THz (corresponding to 1310nm wavelength), but because of the inevitable noise of the laser, the optical frequency contains a frequency shift component Δ v0(t), t represents time.
And 2, dividing the laser continuous light into 3 paths through a splitter, wherein the 1 st path of continuous light is converted into pulse light with specific width and period through an acousto-optic modulator with a frequency shift function, and then enters a sensing optical fiber through an optical amplifier and a circulator to obtain Rayleigh scattering light waves:
wherein B represents the Rayleigh scattered light wave amplitude, ziIndicating the position of the sensing fiber where rayleigh scattering occurs,
representing the number of light waves, k can be regarded as consisting of v only, since the frequency shift component of the light waves of the light source is small compared to the speed of light c0Determining, n represents the refractive index of the optical fiber, c represents the speed of light, fplusRepresenting the pulse frequency, fAOMIndicates the frequency offset of the acousto-optic modulator,
representing a phase change, theta, introduced by an external vibration signalrIndicating the initial phase of the rayleigh scattered light.
And the 2 nd path of continuous light is used as local reference light:
Eref(zref，t)＝B cos(kzref-2π(v0+Δv0(t))t+θref) (3)
wherein B represents the amplitude of the reference light wave, the amplitude of the reference light wave is equal to that of the Rayleigh scattering light wave by adjusting the splitting ratio of the splitter, and z isrefThe length of the optical fiber, theta, representing the reference pathrefIndicating the initial phase of the local reference light.
The rayleigh scattered light and the local reference light enter the photodetector after interfering in the coupler, and the signal can be expressed as:
and 3, performing frequency reduction processing on the interference signal by taking the frequency offset of the acousto-optic modulator as a reference, and extracting phase information in the interference signal by using a Hilbert transform and an anti-tangent method:
step 4, selecting the position z behind the vibration pointAAnd z is the front position of the vibration pointBAnd (4) subtracting the phases of the A, B points to obtain a single differential phase:
wherein D isABIndicating A, B the separation of the two points. Compared with the step 3, the step 4 eliminates phase noise caused by the difference of the initial phases of Rayleigh scattering light and local reference light.
Due to the fact that
The device only focuses on the measurement of the alternating current vibration signal, and can ignore the direct current component v of the light wave frequency0Induced phase constants, retaining only the AC component Δ v0(t) induced phase noise. And, the single differential phase shifts the influence of the light source frequency drift on the measurement signal, from
To a small extent
And 5, taking the 3 rd path of continuous light which is split after the continuous light emitted by the light source passes through the splitter as calibration light, entering a frequency shift calibration auxiliary channel, and obtaining two paths (I path and Q path) of orthogonal interference signals by using a classical Mach-Zehnder interferometer:
I(t)＝C cos(2π(v0+Δv0(t))τ) (7)
Q(t)＝C sin(2π(v0+Δv0(t))τ) (8)
where C represents the amplitude of the interference signal and τ represents the time delay caused by the interferometer arm length of the mach-zehnder interferometer.
The I path interference signal is multiplied by the I path original signal after being subjected to time averaging, and the Q path interference signal is multiplied by the Q path original signal after being subjected to time averaging to obtain:
where T represents the length of time for averaging. The phase noise caused by the frequency drift of the light source is a bounded zero mean value random process, and is zero after time averaging, so that the following results are obtained:
adding the two paths of signals obtained in the previous step to obtain:
performing Hilbert transform and arc tangent operation on the signal output by the adder, and extracting phase information:
A, B according to the distance D between two points in single differenceABMach-Zehnder in sum frequency shift calibration auxiliary channelLength difference of interference arm of interferometer DDIFProportional relationship therebetween, determining frequency drift correction coefficient
And (3) carrying out frequency drift calibration on the single differential phase to obtain an external vibration signal measured value with higher precision:
the above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Claims (10)
1. An optical fiber vibration measuring device with a light source frequency shift calibration auxiliary channel is characterized by comprising:
the measuring structure is used for acquiring a first path of continuous light and a second path of continuous light output by the branching unit, the first path of continuous light is processed and then input into the sensing optical fiber through the circulator, backward Rayleigh scattered light which is output by the circulator and carries vibration information is optically coupled with the second path of continuous light, and then the backward Rayleigh scattered light is output to the data acquisition card through the photoelectric detector;
the auxiliary channel is used for acquiring a third path of continuous light output by the splitter, processing the third path of continuous light after sequentially passing through the interferometer and the photoelectric balance detector, extracting phase information and inputting the phase information into the data acquisition card;
and the processor is used for acquiring and processing data in the data acquisition card to obtain the environmental vibration information along the sensing optical fiber.
2. The apparatus according to claim 1, wherein the interferometer divides the first continuous light into two orthogonal interference optical signals, and inputs the two interference optical signals to the first optical balance detector and the second optical balance detector respectively.
3. The optical fiber vibration measuring device with the auxiliary channel for frequency shift calibration of light source according to claim 2, wherein the two interference electrical signals are processed to extract phase information and input the phase information to the data acquisition card.
4. The fiber optic vibration measuring device with the auxiliary channel for frequency shift calibration of light source according to claim 1, wherein the first continuous light is converted into pulsed light with a set width and period by the acousto-optic modulator with frequency shift, and then enters the sensing fiber by the optical amplifier and the circulator.
5. The optical fiber vibration measuring device with the auxiliary channel for frequency shift calibration of the light source as claimed in claim 4, wherein the second path of continuous light is used as local reference light, couples with Rayleigh scattering light to output interference signals, enters the photoelectric detector, performs frequency reduction processing on the interference signals by taking the frequency offset of the acousto-optic modulator as reference, extracts phase information in the interference signals, and outputs the phase information to the data acquisition card.
6. An optical fiber vibration measurement method with a light source frequency shift calibration auxiliary channel is characterized by comprising the following steps:
the first path of continuous light output by the branching unit is input into the sensing optical fiber through a circulator after being subjected to acousto-optic modulation and light amplification, and the circulator outputs backward Rayleigh scattering light with environmental vibration information generated in the sensing optical fiber;
after the Rayleigh scattered light is optically coupled with the second path of continuous light output by the branching unit, the Rayleigh scattered light is input into a data acquisition card through a photoelectric detector;
taking the third path of continuous light output by the splitter as calibration light, entering an auxiliary channel for frequency shift calibration, extracting phase information and inputting the phase information into a data acquisition card;
and processing the data in the data acquisition card to acquire the environmental vibration information along the sensing optical fiber.
7. The method as claimed in claim 6, wherein the rayleigh scattered light is coupled with the second continuous light to generate an interference signal, the frequency offset of the acousto-optic modulator is used as a reference to down-convert the interference signal, and then the hilbert transform and the anti-tangent method are used to extract the phase information in the interference signal.
8. The fiber optic vibration measurement device with an auxiliary channel for frequency shift calibration of a light source of claim 6, wherein the processing of the third continuous light in the auxiliary channel is specifically as follows:
obtaining an I path interference signal and a Q path interference signal which are orthogonal with each other through an interferometer;
the I path interference signal is multiplied by the I path original signal after being subjected to time averaging, the Q path interference signal is multiplied by the Q path original signal after being subjected to time averaging, and the obtained two paths of signals are added by an adder;
the signal output from the adder is subjected to hilbert transform and arc tangent operation, and phase information is extracted.
9. The apparatus of claim 6, wherein the backward Rayleigh scattering light carries environmental vibration information received by the sensing fiber and exits through the port of the circulator.
10. The apparatus of claim 6, wherein the laser outputs a continuous beam, which is split into three paths by the splitter and processed separately.
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| CN113721287A (en) * | 2021-07-16 | 2021-11-30 | 西北大学 | Monitoring method and device based on sensing optical fiber |
| WO2023123968A1 (en) * | 2021-12-30 | 2023-07-06 | 中国石油天然气集团有限公司 | Quadrature demodulation imbalance correction method and system for distributed fiber acoustic sensing data |
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