CN104422512A - Vibration detection method based on coherent optical time domain reflection - Google Patents
Vibration detection method based on coherent optical time domain reflection Download PDFInfo
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- CN104422512A CN104422512A CN201310392293.8A CN201310392293A CN104422512A CN 104422512 A CN104422512 A CN 104422512A CN 201310392293 A CN201310392293 A CN 201310392293A CN 104422512 A CN104422512 A CN 104422512A
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Abstract
The invention discloses a vibration detection method based on coherent optical time domain reflection, and belongs to the field of vibration detection. The method comprises the following steps: providing N paths of pulse laser of which the wavelengths are different, wherein the time interval of two continuous pulses in each path of pulse laser is larger than or equal T, the time interval between two continuous pules in different paths of pulse laser is less than T, T=2Ln/C, L is the length of a measurement optical fiber, C is a vacuum speed of light, n is the fiber core refractive index of the measurement optical fiber, and N is larger than or equal to 2; multiplexing N paths of pulse laser; inputting the multiplexed pulse laser into the measurement optical fiber; separating output backward Rayleigh scattered light; performing photoelectric conversion on the separated Rayleigh scattered light to obtain an electric signal; positioning the vibration by adopting the electric signal. By adopting the vibration detection method, the problem of low signal sampling frequency since only one pulse laser is allowed to exist in the measurement optical fiber in the prior art is solved, the sampling frequency of a vibration signal is increased, and the vibration signal obtained by sampling is more complete.
Description
Technical field
The present invention relates to vibration detection field, particularly a kind of method for detecting vibration based on coherent light time domain reflection.
Background technology
COTDR(Coherent Optical Time-Domain Reflectometry, coherent light time domain reflection) optical time domain reflection technology that is otherwise known as based on coherent rayleigh scattering, it is rear to Rayleigh scattering that this technology can utilize super-narrow line width laser pulse to occur in measuring optical fiber, detects the vibration that measuring optical fiber occurs along the line.
At present, the main process realizing this technology is: first, produces a pulse laser; Then, the pulse laser produced is passed through a port input measurement optical fiber of circulator, laser pulse is transmitted in measuring optical fiber, thus produces backward Rayleigh scattering light, this backward Rayleigh scattering light is exported by the another port of circulator; Finally, whether the backward Rayleigh scattering light determination measuring optical fiber exported according to circulator exists vibration along the line.
Realizing in process of the present invention, inventor finds that prior art at least exists following problem:
Mutual interference in measuring optical fiber between laser pulse, need to ensure in measuring optical fiber, to only have a laser pulse to exist all the time, this causes sample frequency low (number namely producing backward Rayleigh scattering light is within a certain period of time few), therefore according to sampling thheorem, possibly cannot be complete collect vibration signal, cause the result of vibration detection not accurate enough.
Summary of the invention
Only allowing only there is a laser pulse in measuring optical fiber to solve prior art, causing signal sampling frequency low, the problem that the frequency of vibration signal is low can be detected, embodiments providing a kind of method for detecting vibration based on COTDR.Described technical scheme is as follows:
The embodiment of the present invention additionally provides a kind of method for detecting vibration based on coherent light time domain reflection, and described method comprises:
The pulse laser that N road wavelength is different is provided, in pulse laser described in each road, the time interval of two continuous print pulses is all more than or equal to T, and the time interval between any two continuous print pulses not belonging to pulse laser described in same road is less than T, wherein, N >=2, T=2Ln/C, L are the length of described measuring optical fiber, C is vacuum light speed, and n is described measuring optical fiber fiber core refractive index;
Carry out multiplexing to pulse laser described in N road;
By the described pulse laser input measurement optical fiber after multiplexing, and export multiplexing after described pulse laser in described measuring optical fiber, transmit the rear to Rayleigh scattering light of generation;
Described backward Rayleigh scattering light is separated, produces the Rayleigh scattering light that N number of wavelength is different;
The Rayleigh scattering light different to isolated described N number of wavelength carries out opto-electronic conversion, obtains N number of electric signal;
Described electric signal is adopted to position vibration.
In a kind of implementation of the embodiment of the present invention, in pulse laser described in each road, the time interval of two continuous print pulses is equal to T, and the time interval between two the continuous print pulses not belonging to pulse laser described in same road is T/N.
In the another kind of implementation of the embodiment of the present invention, described in provide N road wavelength different pulse laser, comprising:
Multiple-wavelength laser is adopted to produce the different continuous laser of N road wavelength;
The continuous laser different to described N road wavelength is separated;
Continuous laser different for described N road wavelength after being separated is converted to the different described pulse laser of N road wavelength.
In the another kind of implementation of the embodiment of the present invention, described the different continuous laser of described N road wavelength after being separated is converted to the different described pulse laser of N road wavelength, comprises:
Adopt clock signal to control N number of acousto-optic modulator, thus continuous laser described in N road is converted to pulse laser described in N road, described in described N number of acousto-optic modulator and described N road, continuous laser one_to_one corresponding is arranged.
In the another kind of implementation of the embodiment of the present invention, described in provide N road wavelength different pulse laser, comprising:
N number of laser instrument is adopted to produce the different continuous laser of N road wavelength;
Continuous laser different for described N road wavelength is converted to the different pulse laser of N road wavelength.
In the another kind of implementation of the embodiment of the present invention, described in provide N road wavelength different pulse laser, comprising:
N number of pulsed laser is adopted to produce the different described pulse laser of N road wavelength.
In the another kind of implementation of the embodiment of the present invention, the described electric signal of described employing positions vibration, comprising:
The voltage of described N number of electric signal is averaged, obtains average electrical signal;
Detect in described average electrical signal and whether there is sign mutation;
When there is sign mutation in described average electrical signal, determining to there is vibration around described measuring optical fiber, and described vibration is positioned.
In the another kind of implementation of the embodiment of the present invention, described by the pulse laser input measurement optical fiber after multiplexing before, described method also comprises:
Energy amplification is carried out to described pulse laser.
The beneficial effect that the technical scheme that the embodiment of the present invention provides is brought is:
By producing the different pulse laser of N road wavelength, continuous two pulses interval greater than equaling T in each road pulse laser, and the time interval between any two continuous print pulses not belonging to same road pulse laser is less than T, due to N >=2, T=2Ln/C, L is the length of measuring optical fiber, C is vacuum light speed, n is measuring optical fiber fiber core refractive index, therefore the burst transmissions of at least 2 different wave lengths in section T at any time can be ensured in measuring optical fiber, because the pulse of different wave length is transmitted in measuring optical fiber simultaneously, the phenomenons such as interference can not be produced, therefore avoid prior art and only allow the pulse laser of the interior only existence of section T at any time in measuring optical fiber, cause the problem that signal sampling frequency is low, improve vibration signal sample frequency, the vibration signal that making samples obtains is more complete.
Accompanying drawing explanation
In order to be illustrated more clearly in the technical scheme in the embodiment of the present invention, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is the method for detecting vibration process flow diagram based on COTDR that the embodiment of the present invention one provides;
Fig. 2 is the method for detecting vibration process flow diagram based on COTDR that the embodiment of the present invention two provides;
Fig. 3 is pulse laser sequential chart in the measuring optical fiber that provides of the embodiment of the present invention two.
Embodiment
For making the object, technical solutions and advantages of the present invention clearly, below in conjunction with accompanying drawing, embodiment of the present invention is described further in detail.
Embodiment one
Embodiments provide a kind of method for detecting vibration based on COTDR, see Fig. 1, the method comprises:
Step 101: the pulse laser that N road wavelength is different is provided, and in each road pulse laser two continuous print pulses interval greater than equaling T, and the time interval between any two continuous print pulses not belonging to same road pulse laser is less than T, wherein, T=2Ln/C, L are the length of measuring optical fiber, and C is vacuum light speed, n is measuring optical fiber fiber core refractive index, N >=2.
Step 102: carry out multiplexing to N road pulse laser.
Step 103: by the pulse laser input measurement optical fiber after multiplexing, and export multiplexing after pulse laser in measuring optical fiber, transmit the rear to Rayleigh scattering light of generation.
Step 104: be separated backward Rayleigh scattering light, produces the Rayleigh scattering light that N number of wavelength is different.
Step 105: the Rayleigh scattering light different to isolated N number of wavelength carries out opto-electronic conversion, obtains N number of electric signal.
Step 106: adopt electric signal to position vibration.
The embodiment of the present invention is by producing the different pulse laser of N road wavelength, continuous two pulses interval greater than equaling T in each road pulse laser, and the time interval between any two continuous print pulses not belonging to same road pulse laser is less than T, due to N >=2, T=2Ln/C, L is the length of measuring optical fiber, C is vacuum light speed, n is measuring optical fiber fiber core refractive index, therefore the burst transmissions of at least 2 different wave lengths in section T at any time can be ensured in measuring optical fiber, because the pulse of different wave length is transmitted in measuring optical fiber simultaneously, the phenomenons such as interference can not be produced, therefore avoid prior art and only allow the pulse laser of the interior only existence of section T at any time in measuring optical fiber, cause the problem that signal sampling frequency is low, improve vibration signal sample frequency, the vibration signal that making samples obtains is more complete.
Embodiment two
Embodiments provide a kind of method for detecting vibration based on COTDR, see Fig. 2, the method comprises:
Step 201: the pulse laser that N road wavelength is different is provided, and in each road pulse laser two continuous print pulses interval greater than equaling T, and the time interval between any two continuous print pulses not belonging to same road pulse laser is less than T, wherein, T=2Ln/C, L are the length of measuring optical fiber, and C is vacuum light speed, n is measuring optical fiber fiber core refractive index, N >=2.
Particularly, in a kind of implementation of the embodiment of the present invention, step 201 can realize in the following ways:
Step one, the continuous laser adopting multiple-wavelength laser generation N road wavelength different.
Step 2, the continuous laser different to this N road wavelength are separated.
Step 3, the different continuous laser of N road wavelength after being separated is converted to the different pulse laser of N road wavelength by devices such as acousto-optic modulators.
Particularly, can realize step three in the following ways: adopt clock signal to control N number of acousto-optic modulator, thus N road continuous laser is converted to N road pulse laser, described in N number of acousto-optic modulator and N road, continuous laser one_to_one corresponding is arranged.
In the another kind of implementation of the embodiment of the present invention, in a kind of implementation of the embodiment of the present invention, step 201 can also realize in the following ways:
Step one, the continuous laser adopting N number of laser instrument generation N road wavelength different.
Step 2, continuous laser different for N road wavelength is converted to the different pulse laser of N road wavelength by devices such as acousto-optic modulators.
In the another kind of implementation of the embodiment of the present invention, in a kind of implementation of the embodiment of the present invention, step 201 can also realize in the following ways:
N number of pulsed laser is adopted to produce the different pulse laser of N road wavelength.
Further, in above-mentioned three kinds of implementations, in order to ensure continuous two pulses in each road pulse laser interval greater than equaling T, and the time interval between any two continuous print pulses not belonging to same road pulse laser is less than T, need to adopt clock signal to control acousto-optic modulator or pulsed laser.
Preferably, in a kind of implementation of the embodiment of the present invention, in each road pulse laser, the time interval of two continuous print pulses is equal to T, and the time interval between two the continuous print pulses not belonging to same road pulse laser is T/N.Now, signal sampling frequency is N/T.
Such as, the time interval of continuous two pulses in each road pulse laser is equal to T, and the time interval between continuous two pulses of not going the same way in pulse laser is T/3, thus make multiplexing after pulse laser in pulse between space interval and the time interval average.See Fig. 3, in the pulse laser in t1 moment measuring optical fiber, pulse is followed successively by λ
1, λ
2, λ
3, in the pulse laser in t2 moment measuring optical fiber, pulse is followed successively by λ
2, λ
3, λ
1, in the pulse laser in t3 moment measuring optical fiber, pulse is followed successively by λ
3, λ
1, λ
2, in the pulse laser in t4 moment measuring optical fiber, pulse is followed successively by λ
1, λ
2, λ
3.
In embodiments of the present invention, the time interval of two continuous print pulses in each road pulse laser is all more than or equal to T, and the time interval between any two continuous print pulses not belonging to same road pulse laser is less than T, so both ensure that the pulse of often kind of wavelength in measuring optical fiber only can exist one simultaneously, in turn ensure that in measuring optical fiber to there is the different pulse of at least two wavelength simultaneously, make its sample frequency >=2/T, thus compared with prior art, improve sample frequency.
Further, may there is the situation of pulse overlap in above-mentioned pulse of not going the same way, and above-mentioned two the continuous print pulses not belonging to same road pulse laser do not comprise the situation of this pulse overlap.
Step 202: carry out multiplexing to N road pulse laser.
Step 203: energy amplification is carried out to the pulse laser after multiplexing.
When specific implementation, Erbium-Doped Fiber Amplifier (EDFA) can be adopted to carry out above-mentioned energy amplification.
Step 204: by the pulse laser input measurement optical fiber after multiplexing, and export multiplexing after pulse laser in measuring optical fiber, transmit the rear to Rayleigh scattering light of generation.
Step 205: be separated backward Rayleigh scattering light, produces the Rayleigh scattering light that N number of wavelength is different.
Step 206: the Rayleigh scattering light different to isolated N number of wavelength carries out opto-electronic conversion, obtains N number of electric signal.
Step 207: adopt electric signal to position vibration.
Particularly, step 207, comprising:
Step one, the voltage of N number of electric signal to be averaged, to obtain average electrical signal.
Whether sign mutation is there is in step 2, detection average electrical signal.
Wherein, sign mutation refers to the magnitude of voltage sudden change of average electrical signal, and namely the phase place of magnitude of voltage exceedes preset range.
Step 3, when there is sign mutation in average electrical signal, determining to there is vibration around measuring optical fiber, and vibration to be positioned.
Particularly, vibration is positioned, can in the following way:
Electric signal is sampled, in the time period T from the moment of pulses generation, a point of sampling;
Determine the position residing for jump signal point, such as catastrophe point is b, b≤a;
According to the position residing for jump signal point, can determine that this vibration source distance be in apart from measuring optical fiber incidence end is the position of measuring optical fiber length b/a.
Such as, when adopting 100 points, the 20th point is undergone mutation, then can determine that this vibration source distance be in apart from measuring optical fiber incidence end is the position of measuring optical fiber length 1/5.
Wherein, step 201, when the pulse laser providing N road wavelength different, adopts identical clock signal with step 207, thus can carry out the location of vibration source more accurately.
The embodiment of the present invention is by producing the different pulse laser of N road wavelength, continuous two pulses interval greater than equaling T in each road pulse laser, and the time interval between any two continuous print pulses not belonging to same road pulse laser is less than T, due to N >=2, T=2Ln/C, L is the length of measuring optical fiber, C is vacuum light speed, n is measuring optical fiber fiber core refractive index, therefore the burst transmissions of at least 2 different wave lengths in section T at any time can be ensured in measuring optical fiber, because the pulse of different wave length is transmitted in measuring optical fiber simultaneously, the phenomenons such as interference can not be produced, therefore avoid prior art and only allow the pulse laser of the interior only existence of section T at any time in measuring optical fiber, cause the problem that signal sampling frequency is low, improve vibration signal sample frequency, the vibration signal that making samples obtains is more complete.
The invention described above embodiment sequence number, just to describing, does not represent the quality of embodiment.
One of ordinary skill in the art will appreciate that all or part of step realizing above-described embodiment can have been come by hardware, the hardware that also can carry out instruction relevant by program completes, described program can be stored in a kind of computer-readable recording medium, the above-mentioned storage medium mentioned can be ROM (read-only memory), disk or CD etc.
The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (8)
1. based on a method for detecting vibration for coherent light time domain reflection, it is characterized in that, described method comprises:
The pulse laser that N road wavelength is different is provided, in pulse laser described in each road, the time interval of two continuous print pulses is all more than or equal to T, and the time interval between two the continuous print pulses not belonging to pulse laser described in same road is less than T, wherein, N >=2, T=2Ln/C, L are the length of described measuring optical fiber, C is vacuum light speed, and n is described measuring optical fiber fiber core refractive index;
Carry out multiplexing to pulse laser described in N road;
By the described pulse laser input measurement optical fiber after multiplexing, and export multiplexing after described pulse laser in described measuring optical fiber, transmit the rear to Rayleigh scattering light of generation;
Described backward Rayleigh scattering light is separated, produces the Rayleigh scattering light that N number of wavelength is different;
The Rayleigh scattering light different to isolated described N number of wavelength carries out opto-electronic conversion, obtains N number of electric signal;
Described electric signal is adopted to position vibration.
2. method according to claim 1, is characterized in that, in pulse laser described in each road, the time interval of two continuous print pulses is equal to T, and the time interval between two the continuous print pulses not belonging to pulse laser described in same road is T/N.
3. method according to claim 1, is characterized in that, described in provide N road wavelength different pulse laser, comprising:
Multiple-wavelength laser is adopted to produce the different continuous laser of N road wavelength;
The continuous laser different to described N road wavelength is separated;
Continuous laser different for described N road wavelength after being separated is converted to the different described pulse laser of N road wavelength.
4. method according to claim 3, is characterized in that, described the different continuous laser of described N road wavelength after being separated is converted to the different described pulse laser of N road wavelength, comprising:
Adopt clock signal to control N number of acousto-optic modulator, thus continuous laser described in N road is converted to pulse laser described in N road, described in described N number of acousto-optic modulator and described N road, continuous laser one_to_one corresponding is arranged.
5. method according to claim 1, is characterized in that, described in provide N road wavelength different pulse laser, comprising:
N number of laser instrument is adopted to produce the different continuous laser of N road wavelength;
Continuous laser different for described N road wavelength is converted to the different pulse laser of N road wavelength.
6. method according to claim 1, is characterized in that, described in provide N road wavelength different pulse laser, comprising:
N number of pulsed laser is adopted to produce the different pulse laser of N road wavelength.
7. method according to claim 1, is characterized in that, the described electric signal of described employing positions vibration, comprising:
The voltage of described N number of electric signal is averaged, obtains average electrical signal;
Detect in described average electrical signal and whether there is sign mutation;
When there is sign mutation in described average electrical signal, determining to there is vibration around described measuring optical fiber, and described vibration is positioned.
8. the method according to any one of claim 1-6, is characterized in that, described by the pulse laser input measurement optical fiber after multiplexing before, described method also comprises:
Energy amplification is carried out to described pulse laser.
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| CN109764814A (en) * | 2019-03-12 | 2019-05-17 | 长安大学 | A kind of ground fissure horizontal displacement monitors and monitoring method vertically |
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