CN118258481A - Fiber distributed vibration sensing system anti-fading method based on coherent Rayleigh reflection - Google Patents
Fiber distributed vibration sensing system anti-fading method based on coherent Rayleigh reflection Download PDFInfo
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- CN118258481A CN118258481A CN202211671638.9A CN202211671638A CN118258481A CN 118258481 A CN118258481 A CN 118258481A CN 202211671638 A CN202211671638 A CN 202211671638A CN 118258481 A CN118258481 A CN 118258481A
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- 239000000835 fiber Substances 0.000 title claims abstract description 28
- 238000000034 method Methods 0.000 title claims abstract description 22
- 230000001427 coherent effect Effects 0.000 title claims abstract description 19
- 238000005562 fading Methods 0.000 title claims abstract description 19
- 239000013307 optical fiber Substances 0.000 claims abstract description 43
- 230000003287 optical effect Effects 0.000 claims abstract description 33
- 238000012545 processing Methods 0.000 claims abstract description 12
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 230000003321 amplification Effects 0.000 claims description 2
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 2
- 238000012360 testing method Methods 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 5
- 238000001069 Raman spectroscopy Methods 0.000 description 2
- 230000003712 anti-aging effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 229910052691 Erbium Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
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- 230000005693 optoelectronics Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
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- 230000011218 segmentation Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
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Abstract
Embodiments of the present disclosure provide an optical fiber distributed vibration sensing system anti-fading method based on coherent rayleigh reflection, comprising: ensuring that the line width of the laser wavelength emitted by the laser module is within a preset value and stable, and enabling the central wavelength to change within a threshold range according to a preset rule through external adjustment; dividing the laser output by the circulator into a plurality of light splitting parts; dividing the optical fiber to be measured into a plurality of optical sensing units; and selecting one or more acquisition units from each optical sensing unit as target acquisition units. The embodiment of the disclosure performs anti-fading of the optical fiber distributed vibration sensing system based on coherent Rayleigh reflection from a light source part, a light path part and a signal processing part respectively by three methods of adjusting the temperature of a laser module, setting a plurality of sensing fiber cores and dividing a plurality of acquisition units.
Description
Technical Field
The embodiment of the disclosure belongs to the field of optical fiber sensing, and particularly relates to an anti-fading method of an optical fiber distributed vibration sensing system based on coherent Rayleigh reflection.
Background
In recent years, distributed optical fiber vibration sensing technology based on coherent rayleigh reflection has been rapidly developed. In the oil gas pipeline third party construction monitoring field, the oil gas field seismic signal detection field and the logging field are all industrially applied. The sensor uses the optical cable as the sensor, and has the advantages of distributed detection, high sensitivity, electromagnetic interference resistance, natural explosion resistance and the like. Due to the randomness of the backward rayleigh reflected signal, interference cancellation, called fading, is difficult to avoid in the monitored fiber point. The failure of the attenuation point to normally sense the vibration signal becomes a difficulty of optical fiber vibration sensing, and is also a hidden danger of a sensing blind area existing in an actual application scene of optical fiber distributed vibration sensing.
Disclosure of Invention
Embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art, and provide an anti-fading method for an optical fiber distributed vibration sensing system based on coherent rayleigh reflection.
A fiber optic distributed vibration sensing system based on coherent rayleigh reflection comprising: the device comprises a laser module, a pulse light module, an optical amplifying module, a circulator and a photoelectric module which are connected in sequence by an optical path, wherein the electric signal processing module is electrically connected with the photoelectric module, and the circulator is also used for connecting an optical fiber to be tested.
An optical fiber distributed vibration sensing system anti-fading method based on coherent rayleigh reflection of an embodiment of the present disclosure includes:
Ensuring that the line width of the laser wavelength emitted by the laser module is within a preset value and stable, and enabling the central wavelength to change within a threshold range according to a preset rule through external adjustment;
And/or the number of the groups of groups,
Dividing the laser output by the circulator into a plurality of light splitting parts; each light splitting is respectively connected into a plurality of sensing fiber cores, and the physical route of each sensing fiber core is consistent with the characteristics of the optical fiber;
And/or the number of the groups of groups,
Dividing the optical fiber to be measured into a plurality of optical sensing units; wherein each optical sensing unit comprises a plurality of acquisition units;
And selecting a target vibration signal from the vibration signals acquired by the plurality of acquisition units as a vibration signal of the corresponding optical sensing unit.
Optionally, the external adjustment is used to change the central wavelength within a threshold according to a preset rule, including:
The temperature of the laser module is regulated to change according to a sine wave rule, so that the wavelength of laser emitted by the laser module is periodically changed.
Optionally, the frequency range of the sine wave is 0.1 Hz-0.3 Hz.
Preferably, the frequency of the sine wave is 0.1Hz.
Optionally, the preset value is 100kHz, and the threshold value is ±50GHz.
Optionally, dividing the laser output by the circulator into a plurality of light splits, including:
and the output end of the circulator is used for equally dividing the laser output by the circulator into a plurality of light splitters through a coupler.
Optionally, the plurality of sensing fiber cores are included in one of the optical fibers to be tested.
Optionally, the selecting the target vibration signal from the vibration signals acquired by the plurality of acquisition units includes:
And taking the maximum value of the vibration signals acquired by the plurality of acquisition units as the target vibration signal.
Optionally, the selecting the target vibration signal from the vibration signals acquired by the plurality of acquisition units includes:
And taking the average value of the vibration signals acquired by the plurality of acquisition units as the target vibration signal.
Optionally, the selecting the target vibration signal from the vibration signals acquired by the plurality of acquisition units includes:
and taking the weighted average value of the vibration signals acquired by the plurality of acquisition units as the target vibration signal.
The embodiment of the disclosure performs anti-fading of the optical fiber distributed vibration sensing system based on coherent Rayleigh reflection from a light source part, a light path part and a signal processing part respectively by three methods of adjusting the temperature of a laser module, setting a plurality of sensing fiber cores and dividing a plurality of acquisition units.
Drawings
FIG. 1 is a schematic diagram of a prior art optical fiber distributed vibration sensing system based on coherent Rayleigh reflection;
FIG. 2 is a flow chart of an anti-aging method for a fiber optic distributed vibration sensing system based on coherent Rayleigh reflection in accordance with an embodiment of the present disclosure;
FIG. 3 is a schematic diagram of a laser frequency adjustment range according to another embodiment of the present disclosure;
fig. 4 is a schematic diagram of temperature controlled laser frequency adjustment according to another embodiment of the present disclosure.
FIG. 5 is a schematic diagram of a fiber optic distributed vibration sensing system based on coherent Rayleigh reflection according to another embodiment of the present disclosure;
fig. 6 is a schematic diagram of optical fiber under test according to another embodiment of the disclosure.
Detailed Description
In order that those skilled in the art will better understand the technical solutions of the present disclosure, the present disclosure will be described in further detail with reference to the accompanying drawings and detailed description.
As shown in fig. 1, a conventional optical fiber distributed vibration sensing system based on coherent rayleigh reflection includes a laser module 1, a pulse optical module 2, an optical amplifying module 3, a circulator 4, an optoelectronic module 5, an electrical signal processing module 6 and an optical fiber 7 to be tested. The laser module 1, the pulse light module 2, the light amplifying module 3, the circulator 4 and the photoelectric module 5 are sequentially connected through light paths, the photoelectric module 5 is electrically connected with the electric signal processing module 6, and the optical fiber 7 to be tested is connected to the circulator 4.
The laser module 1 is a continuous laser source, and the line width of the source is smaller than 100kHz. The pulsed light module 2 converts continuous light into pulsed light, and the conversion part may be an electro-optical modulator (EOM), an acousto-optic modulator (AOM), or a Semiconductor Optical Amplifier (SOA). The optical amplification module 3 may be one or more of an Erbium Doped Fiber Amplifier (EDFA), a first order raman amplifier (center wavelength 1450 nm) and a second order raman amplifier (center wavelength 1350 nm), and is connected to the input end of the circulator 4. The photoelectric module 5 is connected to the output end of the circulator 4 and is used for converting the optical signal into an electric signal. The electric signal processing module 6 is connected to the photoelectric module 5 through a circuit, and can perform signal segmentation, vibration signal demodulation, signal processing, alarm and the like.
As shown in fig. 2, a fiber optic distributed vibration sensing system anti-aging method according to an embodiment of the present disclosure includes three parts:
And P1, ensuring that the line width of the laser wavelength emitted by the laser module is within a preset value and stable, and enabling the central wavelength to change within a threshold range according to a preset rule through external adjustment.
Specifically, the wavelength of the laser light emitted by the laser light source of the laser module 1 is unchanged for a long time, which may cause fading of the sensing signal. On the premise of ensuring that the linewidth of the laser wavelength is within 100kHz and stable, the temperature of the laser module 1 is regulated by external regulation, and the laser wavelength is changed periodically according to the sine wave law of 0.1 Hz-0.3 Hz. The center wavelength of the laser light varies in a range of about 50GHz at the maximum.
As shown in fig. 3, f1 is the center frequency of the laser, and the typical center frequency is 193.4THz (corresponding to a wavelength of 1550.12 nm). L1 represents the linewidth of the laser, and the linewidth is not higher than 100kHz. L2 is the laser adjusting frequency range and the length is 100Ghz. The corresponding lower limit frequency f0 is 193.35THz (corresponding to the wavelength of 1549.72 nm), and the upper limit frequency f2 is 193.45THz (corresponding to the wavelength of 1550.52 nm).
As shown in fig. 4, the output frequency of the laser source is further changed by changing the cavity length of the laser source resonant cavity by changing the temperature inside the laser source. When the temperature is T1, the corresponding laser frequency is f1, the temperature is changed between T0 and T2 according to the law of sine waves, and the corresponding laser frequency is changed between f1_min and f1_max. Where f1_min needs to be greater than f0 and f1_max needs to be less than f2.
According to the embodiment of the disclosure, the temperature of the laser module is adjusted to periodically change, so that the periodic change of the laser wavelength emitted by the laser module is caused, and the vibration signal fading caused by long-time invariance of the laser wavelength of the traditional optical fiber distributed vibration sensing system based on coherent Rayleigh reflection is effectively reduced from the light source part.
P2, dividing the laser output by the circulator into a plurality of light splitting parts; each beam splitter is respectively connected with a plurality of sensing fiber cores, and the physical route of each sensing fiber core is consistent with the characteristics of the optical fiber.
Specifically, as shown in fig. 5, the embodiment of the disclosure is based on the existing optical fiber distributed vibration sensing system based on coherent rayleigh reflection as shown in fig. 1, a coupler 8 is additionally connected to the output end of the circulator 4, and the coupler 8 is used to divide laser light into two or more parts in equal proportion, and two or more sensing fiber cores are respectively connected. When the physical route and the optical fiber characteristics of each sensing fiber core are consistent, if the vibration signal on one sensing fiber core is faded, and the vibration signals of the other sensing fiber cores are normal, the vibration signals obtained by the photoelectric conversion module 5 are the average result of all the sensing fiber cores because all the sensing fiber cores act simultaneously, so that the total fading degree of the vibration signals can be reduced. In order to achieve the consistency of the physical routing and the optical fiber characteristics of the sensing fiber cores, the sensing fiber cores can be included in the same optical fiber 7 to be tested, so that the point on the same optical fiber skin length senses the vibration on the same physical point.
For example, coupler 8 divides the laser equally into 50%: two parts of 50% are respectively connected into two sensing fiber cores 71 and 72, and the two sensing fiber cores 71 and 72 are both included in the optical fiber 7 to be tested, so that the physical route and the optical fiber characteristics of the sensing fiber cores 71 and 72 are consistent.
According to the embodiment of the disclosure, the laser in the optical fiber to be measured is equally divided into the plurality of light splitting, so that under the condition that the total laser amount is kept unchanged, when a certain light splitting signal is faded, the signal only has limited influence on the total signal, and the anti-fading of the optical fiber distributed vibration sensing system based on coherent Rayleigh reflection is realized in the light path part.
P3, dividing the optical fiber to be measured into a plurality of optical sensing units; wherein each optical sensing unit comprises a plurality of acquisition units;
And selecting a target vibration signal from the vibration signals acquired by the plurality of acquisition units as a vibration signal of the corresponding optical sensing unit.
Specifically, as shown in fig. 6, the electrical signal processing module 6 divides the optical fiber 7 to be measured into a plurality of relatively independent sensor segments (200 ns pulse width corresponds to 20 meters) with the pulse width as a scale, which is called an optical sensing unit 73; the signal acquisition may continue with the subdivision of the optical sensor unit 73 into acquisition units 731. That is, the optical fiber 7 to be measured includes a plurality of optical sensing units 73, and each optical sensing unit 73 includes a plurality of collecting units 731.
When the signal processing module 6 performs signal processing, first, the vibration signal of each collecting unit 731 is obtained, where the vibration signal may use the vibration amplitude as a quantization standard, and one of the vibration signals in one optical sensing unit 73 with the largest vibration amplitude is selected as the target vibration signal of the optical sensing unit 73. The average value of the vibration amplitudes of all the vibration signals in one optical sensing unit 73 may be taken as the target vibration signal of the optical sensing unit 73, and may be a weighted average value.
Through the above three selection manners (maximum value, average value and weighted average value), it is ensured that the fading units in each collecting unit 731 are not selected or have smaller weight, so as to reduce the influence of the vibration signal fading on each optical sensing unit 73, and further reduce the signal fading of the optical fiber 7 to be tested. Alternatively, a target vibration signal representative may be selected from the target vibration signals of the plurality of optical sensor units.
According to the embodiment of the disclosure, the optical fiber to be measured is divided into the plurality of optical sensing units, each optical sensing unit is subdivided into the plurality of acquisition units, signals acquired by the acquisition units with signal fading are removed, or the influence of the signals is neutralized, so that the anti-fading effect of the optical fiber distributed vibration sensing system based on coherent Rayleigh reflection is realized in a signal processing part.
It should be noted that the three methods P1, P2, and P3 described in the embodiments of the disclosure may be used alone or in any combination.
It is to be understood that the above embodiments are merely exemplary embodiments employed to illustrate the principles of the present disclosure, however, the present disclosure is not limited thereto. Various modifications and improvements may be made by those skilled in the art without departing from the spirit and substance of the disclosure, and are also considered to be within the scope of the disclosure.
Claims (10)
1. An optical fiber distributed vibration sensing system anti-fading method based on coherent rayleigh reflection, the optical fiber distributed vibration sensing system comprising: the device comprises a laser module, a pulse light module, an optical amplification module, a circulator and a photoelectric module which are connected in sequence by an optical path, wherein the electrical signal processing module is electrically connected with the photoelectric module, and the circulator is further used for connecting an optical fiber to be tested, and is characterized in that the method comprises the following steps:
Ensuring that the line width of the laser wavelength emitted by the laser module is within a preset value and stable, and enabling the central wavelength to change within a threshold range according to a preset rule through external adjustment;
And/or the number of the groups of groups,
Dividing the laser output by the circulator into a plurality of light splitting parts; each light splitting is respectively connected into a plurality of sensing fiber cores, and the physical route of each sensing fiber core is consistent with the characteristics of the optical fiber;
And/or the number of the groups of groups,
Dividing the optical fiber to be measured into a plurality of optical sensing units; wherein each optical sensing unit comprises a plurality of acquisition units;
And selecting a target vibration signal from the vibration signals acquired by the plurality of acquisition units as a vibration signal of the corresponding optical sensing unit.
2. The method according to claim 1, wherein the central wavelength is varied within a threshold by a preset law by external adjustment, comprising:
The temperature of the laser module is regulated to change according to a sine wave rule, so that the wavelength of laser emitted by the laser module is periodically changed.
3. The method of claim 2, wherein the sine wave has a frequency in the range of 0.1Hz to 0.3Hz.
4. A method according to claim 3, wherein the sine wave has a frequency of 0.1Hz.
5. The method of claim 1, wherein the preset value is 100kHz and the threshold value is ±50GHz.
6. The method of claim 1, wherein equally dividing the laser light output by the circulator into a plurality of splits comprises:
and the output end of the circulator is used for equally dividing the laser output by the circulator into a plurality of light splitters through a coupler.
7. The method of claim 1, wherein the plurality of sensing cores are included in one of the optical fibers under test.
8. The method of claim 1, wherein selecting the target vibration signal from the vibration signals acquired by the plurality of acquisition units comprises:
And taking the maximum value of the vibration signals acquired by the plurality of acquisition units as the target vibration signal.
9. The method of claim 1, wherein selecting the target vibration signal from the vibration signals acquired by the plurality of acquisition units comprises:
And taking the average value of the vibration signals acquired by the plurality of acquisition units as the target vibration signal.
10. The method of claim 9, wherein selecting the target vibration signal from the vibration signals acquired by the plurality of acquisition units comprises:
and taking the weighted average value of the vibration signals acquired by the plurality of acquisition units as the target vibration signal.
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