A distributed optical fiber shuttle three-component sensor and a monitoring method thereof

Abstract

The application discloses a distributed optical fiber shuttle three-component sensor and a monitoring method thereof. The sensor comprises a shell, a filling medium filled in the shell, a sensing package embedded in the shell and wrapped by the filling medium, and a scattering-enhanced weak-grid optical fiber wound on the surface of the sensing package. The sensing package has a first plane, a second plane and a third plane projected on a Cartesian coordinate system. The scattering-enhanced weak-grid optical fiber with equal length is wound on the first plane, the second plane and the third plane respectively to monitor the vibration from the X-axis direction, the Y-axis direction and the Z-axis direction respectively, and realize three-component monitoring of microseismic signals. The application solves the problem that the traditional distributed optical fiber measurement can only measure a single component and cannot quantitatively measure the vibration signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of elastic wave monitoring, and particularly relates to a distributed optical fiber shuttle-shaped three-component sensor and a monitoring method thereof. BACKGROUND

[0002] Distributed optical fiber has the advantages of high time sampling rate, high spatial sampling rate and high space-time resolution, and is therefore widely used in many fields, such as earthquake monitoring, structural health monitoring, oil and gas pipeline monitoring and environmental monitoring. The high time sampling rate enables it to capture rapidly changing events, the high spatial sampling rate enables it to describe the spatial characteristics of the monitored object in detail, and the high space-time resolution ensures that it can provide fine monitoring data while taking into account both time and space.

[0003] However, despite the many advantages of distributed optical fiber technology, there are still some problems to be solved. First, due to the packaging method of the optical cable and the coupling method of the optical cable monitoring, the signals of different monitoring points lack consistency, which means that the signals collected at different positions may be biased, affecting the accuracy and comparability of the data. In addition, the signals obtained by distributed optical fiber monitoring cannot be effectively calibrated at present, which leads to the inability to accurately quantify the measurement data. The lack of signal calibration limits the use of distributed optical fiber in applications that require accurate measurement and quantitative analysis. SUMMARY

[0004] To solve the above problems, the present application provides a distributed optical fiber shuttle-shaped three-component sensor and a monitoring method thereof, to solve the problems that the traditional distributed optical fiber measurement can only measure a single component, cannot quantitatively measure the vibration signal, and cannot be calibrated and lacks consistency. The technical solution is as follows:

[0005] The first aspect of the present application provides a distributed optical fiber shuttle-shaped three-component sensor, comprising a shell, a filling medium filled in the shell, a sensing package embedded in the shell and wrapped by the filling medium, and a scattering-enhanced weak grating optical fiber wound on the surface of the sensing package, wherein the sensing package has a first plane, a second plane and a third plane projected on a Cartesian coordinate system, and equal-length scattering-enhanced weak grating optical fibers are wound on the first plane, the second plane and the third plane respectively to monitor vibrations from the X-axis direction, the Y-axis direction and the Z-axis direction respectively, realizing three-component monitoring of microseismic signals.

[0006] For example, in one embodiment, the distributed fiber shutter three-component sensor provided by the scattering enhanced weak grating fiber includes a fiber body, a plurality of weak reflection gratings arranged at equal intervals on the fiber body, and connectors at both ends of the fiber body. The weak reflection gratings are used to enhance the scattering of light signals to enhance the vibration sensing capability of the sensing node. Adjacent two weak reflection gratings form equal length winding sections, and each winding section is wound on the first plane, the second plane and the third plane respectively. The connectors are connected with the fiber demodulator.

[0007] For example, in one embodiment, the distributed fiber shutter three-component sensor provided by the scattering enhanced weak grating fiber includes a plurality of fiber grooves engraved on the surface of the sensing package along the X-axis, Y-axis and Z-axis directions for winding the scattering enhanced weak grating fiber. The total length of the fiber grooves engraved on the first plane, the second plane and the third plane is equal.

[0008] For example, in one embodiment, the distributed fiber shutter three-component sensor provided by the scattering enhanced weak grating fiber includes a plurality of fiber grooves engraved on the surface of the sensing package along the X-axis, Y-axis and Z-axis directions for winding the scattering enhanced weak grating fiber. The total length of the fiber grooves engraved on the first plane, the second plane and the third plane is equal.

[0009] For example, in one embodiment, the distributed fiber shutter three-component sensor provided by the scattering enhanced weak grating fiber includes a plurality of fiber grooves engraved on the surface of the sensing package along the X-axis, Y-axis and Z-axis directions for winding the scattering enhanced weak grating fiber. The total length of the fiber grooves engraved on the first plane, the second plane and the third plane is equal.

[0010] For example, in one embodiment, the distributed fiber shutter three-component sensor provided by the scattering enhanced weak grating fiber includes a plurality of fiber grooves engraved on the surface of the sensing package along the X-axis, Y-axis and Z-axis directions for winding the scattering enhanced weak grating fiber. The total length of the fiber grooves engraved on the first plane, the second plane and the third plane is equal.

[0011] For example, in one embodiment, the distributed fiber shutter three-component sensor provided by the scattering enhanced weak grating fiber includes a plurality of fiber grooves engraved on the surface of the sensing package along the X-axis, Y-axis and Z-axis directions for winding the scattering enhanced weak grating fiber. The total length of the fiber grooves engraved on the first plane, the second plane and the third plane is equal.

[0012] The second aspect of the present application provides a monitoring method of a distributed fiber shutter three-component sensor. The above-mentioned distributed fiber shutter three-component sensor is used for monitoring. When the sensing package receives vibration from the X direction, the sensing package expands and contracts in the YZ plane, thereby causing the scattering enhanced weak grating fiber wound on the YZ plane to change. The fiber demodulator analyzes the vibration change in the X direction. When the vibration speed in the X direction is V X , the circumference change of the scattering enhanced weak grating fiber wound on the YZ plane is V X' .

[0013]

[0014] The length change speed V of the scattering-enhanced weak-grid optical fiber caused by the vibration X" is:

[0015]

[0016] Wherein, a, b, c are the lengths of the sensing package along the X-axis, Y-axis, and Z-axis in the Cartesian coordinate system respectively, and l is the length of the winding section.

[0017] For example, in the monitoring method of the distributed optical fiber shuttle-shaped three-component sensor provided in an embodiment, when the sensing package receives vibration from the Y direction, the sensing package expands and contracts in the XZ plane, thereby causing the scattering-enhanced weak-grid optical fiber wound in the XZ plane to change, and the vibration change in the Y direction is analyzed by the optical fiber demodulator. When the vibration speed in the Y direction is V Y , the circumference change V Y' of the scattering-enhanced weak-grid optical fiber wound in the XZ plane is caused. is:

[0018]

[0019] The length change speed V of the scattering-enhanced weak-grid optical fiber caused by the vibration Y" is:

[0020]

[0021] For example, in the monitoring method of the distributed optical fiber shuttle-shaped three-component sensor provided in an embodiment, when the sensing package receives vibration from the Z direction, the sensing package expands and contracts in the XY plane, thereby causing the scattering-enhanced weak-grid optical fiber wound in the XY plane to change, and the vibration change in the Z direction is analyzed by the optical fiber demodulator. When the vibration speed in the Z direction is V Z , the circumference change V Z' of the scattering-enhanced weak-grid optical fiber wound in the XY plane is caused. is:

[0022]

[0023] The length change speed V of the scattering-enhanced weak-grid optical fiber caused by the vibration Z" is:

[0024]

[0025] The distributed optical fiber shuttle three-component sensor and the monitoring method thereof provided by some embodiments of the present application have the beneficial effects that the present application solves the problem that the traditional distributed optical fiber measurement can only measure a single component and cannot quantitatively measure the vibration signal, can realize the quantitative measurement and three-component measurement of the vibration signal of the distributed optical fiber, solves the defects that the distributed optical fiber is only one-way sensing and the traditional distributed optical fiber cannot measure the vibration intensity, realizes the sensitization effect of the vibration signal, and can sensitively perceive the external vibration signal. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0027] Figure 1 The structure schematic diagram of the distributed optical fiber shuttle three-component sensor of the present application is shown in the figure.

[0028] Figure 2 The structure schematic diagram of the scattering enhanced weak grid optical fiber of the present application is shown in the figure.

[0029] Figure 3 The front and back three views of the sensing package of the present application are shown in the figure.

[0030] Figure 4 The microseismic signal monitored by the distributed optical fiber shuttle three-component sensor of the present application is shown in the figure. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0033] The first aspect of this application provides a distributed fiber optic shuttle-shaped three-component sensor, such as... Figure 1 As shown, the device includes a housing 1, a filling medium 2 filled within the housing 1, a sensing envelope 3 embedded within the housing 1 and wrapped by the filling medium 2, and a scattering-enhancing weak grating optical fiber 5 wound around the surface of the sensing envelope 3. A sensor base 4 is provided at the bottom of the housing 1. The sensing envelope 3 has a first plane, a second plane, and a third plane projected orthogonally in the Cartesian coordinate system, namely the YZ plane, the XZ plane, and the XY plane. The scattering-enhancing weak grating optical fiber 5 of equal length is wound on the first plane, the second plane, and the third plane respectively to monitor vibrations from the X-axis direction, the Y-axis direction, and the Z-axis direction, thereby realizing three-component monitoring of micro-vibration signals.

[0034] The housing 1 encapsulates the sensing envelope 3 and the scattering-enhanced weak grating fiber 5. The housing 1 can couple with external rock or soil to achieve accurate sensing of elastic waves. The filling medium 2 transmits the vibration sensed by the housing 1 to the sensing envelope 3. The filling medium 2 has a Young's modulus very close to that of the optical fiber and has the same tensile coefficient as the optical fiber. The sensing envelope 3 senses the vibration and transmits it to the scattering-enhanced weak grating fiber 5. The sensing envelope can sense the vibration sensed by the sensing node housing 1 through the coupling of the filling medium 2, which is composed of glass fiber and epoxy resin, and transmit this vibration to the scattering-enhanced weak grating fiber 5, causing a change in the optical signal in the optical fiber. The scattering-enhanced weak grating fiber 5 senses the vibration and transmits the vibration signal to the optical fiber demodulator, which demodulates the optical signal monitored by the sensor.

[0035] For example, in one embodiment of the distributed fiber optic shuttle-shaped three-component sensor, such as Figure 2As shown, the scattering-enhanced weak grating optical fiber 5 comprises an optical fiber body 5-1, a plurality of weak reflection gratings 5-2 arranged at equal intervals on the optical fiber body 5-1, and connectors 5-3 located at both ends of the optical fiber body 5-1. The scattering-enhanced weak grating optical fiber 5 realizes scattering enhancement of the optical signal through the weak reflection gratings 5-2, so as to enhance the vibration sensing capability of the sensing node. Adjacent two weak reflection gratings 5-2 form an equal-length winding section, and each winding section is wound on the first plane, the second plane and the third plane, respectively. The connectors 5-3 are connected to the optical fiber demodulator.

[0036] Specifically, four weak reflection gratings 5-2 are arranged at equal intervals on the scattering-enhanced weak grating optical fiber 5, forming three equal-length winding sections, and the three winding sections are wound on the first plane, the second plane and the third plane, respectively. Since the optical fiber gauge length for demodulating the vibration signal by the distributed optical fiber demodulator is uniform, that is, the distance between two scattering nodes is uniform, the interval of the weak reflection gratings 5-2 must be equal, and thus the length of the optical fiber wound on each plane must be the same.

[0037] The reflectivity of the weak reflection grating 5-2 is 1 / 1000, and the connectors 5-3 at both ends of the optical fiber body 5-1 are FA / APC connectors, which can be conveniently connected to external optical fibers.

[0038] For example, in an embodiment of the distributed optical fiber shuttle-shaped three-component sensor, as shown in Figure 3 As shown, a plurality of optical fiber grooves 3-1 for winding the scattering-enhanced weak grating optical fiber 5 are engraved on the surface of the sensing package 3 along the X-axis, Y-axis and Z-axis directions, respectively, and the total length of the optical fiber grooves 3-1 engraved on the first plane, the second plane and the third plane is equal.

[0039] For example, in an embodiment of the distributed optical fiber shuttle-shaped three-component sensor, the sensing package 3 is an aluminum hollow ellipsoidal body.

[0040] Specifically, the sensing package 3 is mainly made of 7075 aluminum material and is hollow. This material has good elasticity and rigidity and has good sensitivity to external vibration signals.

[0041] For example, in an embodiment of the distributed optical fiber shuttle-shaped three-component sensor, the filling medium 2 is mixed and cast with epoxy resin and glass silk and is coagulated, and has the same tensile coefficient as the optical fiber.

[0042] According to the above embodiment, the filling medium 2 is mainly mixed and cast with epoxy resin and glass silk and is coagulated. It not only has the same tensile coefficient as the optical fiber, but also can avoid reflection wave loss when the external vibration signal is transmitted from the filling medium 2 to the scattering-enhanced weak grating optical fiber 5. In addition, the filling medium 2 has high strength and can better fix the sensing package 3.

[0043] The distributed optical fiber shuttle three-component sensor of the application is coupled with the rock mass through cement during measurement, and the sensor is arranged in XYZ direction, the optical fiber joint 5-3 of the sensor is connected with the external transmission optical fiber, the external transmission optical fiber is connected with the distributed optical fiber acoustic sensing system, that is, the optical fiber demodulator, the light signal monitored by the sensing node is demodulated through the distributed optical fiber acoustic sensing system, and the actual measured vibration signal is converted through a calculation formula.

[0044] The measurement effect of a certain hammer signal is as shown in Figure 4 It can be seen that the vibration signals in the X axis, Y axis and Z axis directions have good consistency, and the PS wave can be clearly separated.

[0045] The application can realize quantitative measurement and three-component measurement of the vibration signal of the distributed optical fiber, solve the defects that the distributed optical fiber is only one-way sensing and the traditional distributed optical fiber cannot measure the vibration intensity, realize the sensitization effect of the vibration signal, and can sensitively perceive the external vibration signal.

[0046] The second aspect of the application provides a monitoring method of a distributed optical fiber shuttle three-component sensor, which uses the above-mentioned distributed optical fiber shuttle three-component sensor for monitoring. When the sensing package 3 receives vibration from the X direction, the sensing package 3 expands and shrinks in the YZ plane, thereby causing the change of the scattering-enhanced weak grating optical fiber 5 wound in the YZ plane. The vibration change in the X direction is analyzed through the optical fiber demodulator. When the vibration speed in the X direction is V X , the length change speed V X' of the scattering-enhanced weak grating optical fiber 5 wound in the YZ plane is:

[0047]

[0048] The length change speed V X" of the scattering-enhanced weak grating optical fiber 5 is:

[0049]

[0050] Wherein, a, b and c are the lengths of the sensing package 3 projected on the X axis, Y axis and Z axis of the Cartesian coordinate system respectively, and l is the length of the winding section.

[0051] For example, in the monitoring method of the distributed optical fiber shuttle three-component sensor provided in an embodiment, when the sensing package 3 receives vibration from the Y direction, the sensing package 3 expands and shrinks in the XZ plane, thereby causing the change of the scattering-enhanced weak grating optical fiber 5 wound in the XZ plane. The vibration change in the Y direction is analyzed through the optical fiber demodulator. When the vibration speed in the Y direction is V Ythe length change speed V of the scattering-enhanced weak grating fiber 5 in the XZ plane is Y' is:

[0052]

[0053] the length change speed V of the scattering-enhanced weak grating fiber 5 in the XZ plane is Y" is:

[0054]

[0055] For example, in the monitoring method of the distributed optical fiber shuttle three-component sensor provided in an embodiment, when the sensing package 3 receives a vibration from the Z direction, the sensing package 3 expands and contracts in the XY plane, thereby causing the scattering-enhanced weak grating fiber 5 wound in the XY plane to change, and the Z-direction vibration change is analyzed by a fiber demodulator, when the Z-direction vibration speed is V Z , the length change speed V of the scattering-enhanced weak grating fiber 5 in the XY plane is Z' is:

[0056]

[0057] the length change speed V of the scattering-enhanced weak grating fiber 5 in the XZ plane is Z" is:

[0058]

[0059] Application Case

[0060] As Figures 2-3 shown, the ellipsoidal sensing package 3 is orthogonally projected on three planes in the Cartesian coordinate system, which are the XY, YZ, and XZ planes, corresponding to the Z-axis, X-axis, and Y-axis directions. The lengths a, b, and c of the ellipsoidal sensing package 3 along the X-axis, Y-axis, and Z-axis in the Cartesian coordinate system are 40.00 mm, 40.00 mm, and 65.00 mm, respectively. The lengths of the scattering-enhanced weak grating fibers 5 in the three planes, i.e., the lengths l of the winding sections, are all 3 m. The scattering-enhanced weak grating fibers 5 wound in each plane have weak reflection gratings 5-2 at both ends. The vibration sensing in the three directions is divided into the following three cases:

[0061] (1) When the hollow sensing package 3 receives a vibration from the X direction, the aluminum ellipsoidal sensing package 3 expands and contracts in the YZ plane, thereby causing the scattering-enhanced weak grating fiber 5 in the YZ plane to change. The X-direction vibration change is analyzed by a demodulator, when the X-direction vibration speed is v, the length change speed V of the scattering-enhanced weak grating fiber 5 in the YZ plane is The length change speed of the scattering enhanced weak grating fiber 5 caused is 1.625v*3m / (π*0.04m+4*(0.0325-0.02))=27.7519v;

[0062] (2) When the hollow sensing package 3 receives vibration from the Y direction, the aluminum ellipsoid-shaped sensing package 3 will expand and contract in the XZ plane, thereby causing the change of the scattering enhanced weak grating fiber 5 in the XZ plane, and the vibration change in the Y direction is analyzed by the demodulator, when the vibration speed in the Y direction is v, the length change speed of the scattering enhanced weak grating fiber 5 caused in the XZ plane is

[0063] The length change speed of the scattering enhanced weak grating fiber 5 caused is 1.625v*3m / (π*0.04m+4*(0.0325-0.02))=27.7519v.

[0064] (3) When the hollow sensing package 3 receives vibration from the Z direction, the aluminum ellipsoid-shaped sensing package 3 will expand and contract in the XY plane, thereby causing the change of the fiber in the XY plane, and the vibration change in the Z direction is analyzed by the demodulator, when the vibration speed in the Z direction is v, the length change speed of the scattering enhanced weak grating fiber 5 caused in the XY plane is The length change speed of the scattering enhanced weak grating fiber 5 caused is 0.615v*3m / (π*0.04m)=14.682v.

[0065] It can be known from the above conversion formula that the distributed optical fiber shuttle-shaped three-component sensor provided by the application sensitizes the signals measured in the XYZ three directions, and the distributed optical fiber shuttle-shaped three-component sensor and the monitoring method thereof solve the problems that the traditional distributed optical fiber measurement can only measure a single component and cannot quantitatively measure vibration signals.

[0066] Although the embodiments of the application have been disclosed as above, they are not limited to the application listed in the specification and the embodiments, and can be fully applied to various fields suitable for the application, and other modifications can be easily realized by those skilled in the art, therefore the application is not limited to specific details and the figures shown and described herein, without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A distributed fiber optic shuttle-shaped three-component sensor, characterized in that, The device includes a housing, a filling medium filled within the housing, a sensing envelope embedded within the housing and enclosed by the filling medium, and a scattering-enhancing weak grating optical fiber wound around the surface of the sensing envelope. The sensing envelope has a first plane, a second plane, and a third plane projected orthogonally into a Cartesian coordinate system. Equal-length scattering-enhancing weak grating optical fibers are wound around the first, second, and third planes respectively to monitor vibrations from the X-axis, Y-axis, and Z-axis directions, achieving three-component monitoring of micro-vibration signals. The scattering-enhancing weak grating optical fiber includes an optical fiber body and optical fibers evenly spaced on the optical fiber. Several weak reflection gratings on the main body and connectors located at both ends of the optical fiber body enhance the scattering of light signals through the weak reflection gratings, thereby enhancing the vibration sensing capability of the sensing node. An equal-length winding segment is formed between two adjacent weak reflection gratings, and each winding segment is wound on the first plane, the second plane, and the third plane respectively. The connector is externally connected to an optical fiber demodulator. Several optical fiber grooves for winding the scattering enhancement weak grating optical fiber are respectively engraved along the X-axis, Y-axis, and Z-axis directions on the surface of the sensing envelope, and the total length of the optical fiber grooves engraved on the first plane, the second plane, and the third plane is equal.

2. The distributed fiber optic shuttle-shaped three-component sensor according to claim 1, characterized in that, The shell couples with the external rock or soil to sense vibrations, and transmits the sensed vibrations to the scattering-enhancing weak grating optical fiber through the coupling of the filling medium and the sensing envelope, causing changes in the optical signal in the optical fiber, which is then transmitted to the optical fiber demodulator, where the optical fiber demodulator demodulates the optical signal monitored by the sensor.

3. The distributed fiber optic shuttle-shaped three-component sensor according to claim 2, characterized in that, The sensing envelope is a hollow aluminum ellipsoid.

4. The distributed fiber optic shuttle-shaped three-component sensor according to claim 3, characterized in that, The filling medium is a mixture of epoxy resin and glass fiber, cast and solidified, and has the same tensile coefficient as optical fiber.

5. The distributed fiber optic shuttle-shaped three-component sensor according to claim 4, characterized in that, The connector has four weak reflection gratings evenly spaced on the scattering-enhancing weak grating fiber, forming three equally long winding segments, and the connectors at both ends of the fiber body are FA / APC connectors.

6. The distributed fiber optic shuttle-shaped three-component sensor according to claim 5, characterized in that, When the sensing element receives vibration from the X direction, it expands and contracts in the YZ plane, causing a change in the scattering-enhancing weak grating fiber wound in the YZ plane. The vibration change in the X direction is analyzed using a fiber optic demodulator. When the vibration velocity in the X direction is V... X At this time, it causes a change in the perimeter V of the scattering-enhancing weak grating fiber wound in the YZ plane. X' for: The rate of change of the length V of the scatter-enhanced weak grating fiber X" for: Where a, b, and c are the lengths of the sensing package projected onto the Cartesian coordinate system along the X-axis, Y-axis, and Z-axis, respectively. The length of the winding segment.

7. The distributed fiber optic shuttle-shaped three-component sensor according to claim 6, characterized in that, When the sensing element receives vibration from the Y direction, it expands and contracts in the XZ plane, causing changes in the scattering-enhancing weak grating fiber wound in the XZ plane. The vibration change in the Y direction is analyzed using a fiber optic demodulator. When the vibration velocity in the Y direction is V... Y At this time, it causes a change in the perimeter V of the scattering-enhancing weak grating fiber wound in the XZ plane. Y' for: The rate of change of the length V of the scatter-enhanced weak grating fiber Y" for:

8. The distributed fiber optic shuttle-shaped three-component sensor according to claim 7, characterized in that, When the sensing element receives vibration from the Z direction, it expands and contracts in the XY plane, causing changes in the scattering-enhancing weak grating fiber wound in the XY plane. The vibration change in the Z direction is analyzed using a fiber optic demodulator. When the vibration velocity in the Z direction is V... Z At this time, it causes a change in the perimeter V of the scattering-enhancing weak grating fiber wound in the XY plane. Z' for: The rate of change of the length V of the scatter-enhanced weak grating fiber Z" for:

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