A sedimentation sensor and measurement system and method based on optical fiber Fabry-Perot interferometry

Abstract

This invention relates to the field of settlement sensor technology, specifically to a settlement sensor, measurement system, and method based on fiber optic Fabry-Perot interferometry. The settlement sensor includes a housing, an L-shaped cantilever beam structure, and a Fabry-Perot interferometry cavity. The housing contains the L-shaped cantilever beam and the Fabry-Perot interferometry cavity. One end of the fiber optic cable and the cantilever beam are fixed to the housing. When the settlement changes, the liquid level inside the sensor changes, causing changes in the length submerged by the float and the buoyancy. The cantilever beam bends under stress, causing a fixed reflector above the cantilever beam to move. The movement distance of the reflector is measured by the Fabry-Perot interferometry cavity, thereby determining the change in liquid level and the settlement amount. This invention has advantages such as high measurement accuracy, good fatigue resistance, long lifespan, and immunity to electromagnetic interference. It is suitable for settlement monitoring of power infrastructure, including uneven settlement of structures such as pipe corridors and hydropower stations.

Description

Technical Field

[0001] This invention relates to the field of settlement monitoring sensor technology, specifically to a settlement sensor, measurement system, and method based on fiber optic Fabry-Perot interferometry. Background Technology

[0002] Settlement is an important indicator for monitoring urban utility tunnels. For example, uneven settlement of power transmission tunnels can crack the lining concrete, allowing pore water from the soil to enter the tunnel, soaking the power facilities, causing safety issues, and shortening their service life.

[0003] Currently, settlement monitoring of urban integrated utility tunnels typically uses methods such as hydrostatic leveling. However, traditional hydrostatic levels based on electrical principles suffer from weak resistance to electromagnetic interference, while hydrostatic levels based on fiber optic gratings suffer from low accuracy and insufficient long-term stability.

[0004] Therefore, it is essential to develop a settlement measurement device with advantages such as good long-term stability and strong resistance to electromagnetic interference. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a settlement sensor, measurement system, and method based on fiber optic Fabry-Perot interferometry. This sensor offers high measurement accuracy, long lifespan, and immunity to electromagnetic interference. It is suitable for settlement monitoring of power infrastructure, including uneven settlement of pipe corridors and earth-rock dams with significant settlement.

[0006] The present invention adopts the following technical solution.

[0007] The first aspect of the present invention discloses a sedimentation sensor based on fiber optic Fabry-Perot interferometry, comprising: a sedimentation sensor housing, an L-shaped cantilever beam, and a Fabry-Perot interferometry cavity. The L-shaped cantilever beam is fixed inside the sedimentation sensor housing. The L-shaped cantilever beam includes a cantilever beam crossbeam and a float. The upper surface of the cantilever beam crossbeam is a second reflection point. One end of the cantilever beam crossbeam is rigidly connected to the inner wall of the sensor housing, and the other end is fixed with a vertical float. The float is inserted into the liquid, and the liquid generates buoyancy on the float.

[0008] An optical fiber is installed inside the housing of the sedimentation sensor. The end face of the optical fiber is the first reflection point, and the first reflection point and the second reflection point form a Fabry-Perot interferometer cavity.

[0009] When the sedimentation is measured, the cantilever beam can be bent and changes with the position of the liquid in the sedimentation sensor. The distance between the first reflection point and the second reflection point changes accordingly, and the length of the Fabry-Perot cavity changes, thereby determining the liquid level change and sedimentation.

[0010] Preferably, the optical fiber is fixed to the sensor housing by a horizontal beam, the horizontal beam is perpendicular to the housing, the optical fiber is in the vertical direction and perpendicular to the horizontal beam, and the axis of the fixed optical fiber coincides with the axis of the second reflection point.

[0011] Preferably, one end of the optical fiber is the first reflection point, and the other end is connected to a spectrometer for emitting light waves and collecting Fabry-Perot interference spectra.

[0012] Preferably, the second reflection point is a reflector located on the crossbeam of the cantilever beam near the transmission optical fiber, with a reflectivity between 0% and 100%, and the normal of the reflector is perpendicular to and intersects the axis of the L-shaped cantilever beam.

[0013] Preferably, a vertically placed float is fixed to the end of the cantilever beam. The float and the cantilever beam are an integral part. The float is always inserted into the liquid. When the sedimentation changes, the length of the float submerged in the liquid is different, which makes the buoyancy of the float different. This causes the cantilever beam to bend, which causes the second reflection point to move and changes the distance between the two reflection points.

[0014] Preferably, the float can be tilted, with its axis forming a set angle with the vertical direction.

[0015] The second aspect of the present invention discloses a sedimentation measurement system based on fiber optic Fabry-Perot interferometry, including the aforementioned sedimentation sensor, liquid passage pipe and water tank. The water tank is set at a reference point where no sedimentation occurs. The liquid regions of multiple sedimentation sensors are connected through the liquid passage pipe, and the liquid region of one of the sedimentation sensors is connected to the water tank through the liquid passage pipe.

[0016] A third aspect of the present invention discloses a settlement measurement method based on the aforementioned fiber optic Fabry-Perot interferometry-based settlement sensor system, comprising the following steps:

[0017] Multiple settlement sensors are connected in series and installed at the same elevation as the measurement site;

[0018] A water tank is set up at a reference point where no settlement occurs, and the liquid area of ​​the water tank is connected to the liquid areas of multiple settlement sensors.

[0019] Another sedimentation sensor is inserted into the reference point tank as the liquid level calibration of the reference point, and the sedimentation sensor is used to measure the liquid change in the reference point tank.

[0020] The liquid level change inside each sedimentation sensor in the sedimentation measurement system is measured separately.

[0021] The actual settlement at the test point is obtained by subtracting the liquid level change in the reference tank from the liquid level change measured by each settlement sensor in the settlement measurement system.

[0022] Preferably, the plurality of settlement sensors are installed at equal intervals at the same height.

[0023] Preferably, the method for measuring the liquid level change using the sedimentation sensor is as follows:

[0024] Plot a graph showing the relationship between the length of the Fabry-Perot interferometer cavity and the amount of settlement.

[0025] Linear fitting was performed on the calibration curve to ensure a linear relationship between the settlement and the length of the Fabry-Perot interferometer cavity;

[0026] A linear relationship between the Fabry-Perot interferometer cavity length and the amount of sedimentation was obtained. Compared with the prior art, the beneficial effects of the present invention include at least:

[0027] The settlement sensor provided by this invention is based on the fiber optic Fabry-Perot interferometry principle. It obtains the change in the Fabry-Perot interferometry cavity length through the deflection change of a cantilever beam. Based on the calibration formula between the Fabry-Perot interferometry cavity length and the settlement amount (liquid level change), the settlement amount (liquid level change) can be measured. Since the components of the Fabry-Perot interferometer are non-contact, it avoids fatigue and low accuracy problems caused by object deformation, and also eliminates electromagnetic interference issues. The settlement sensor provided by this invention has advantages such as high accuracy, long lifespan, resistance to electromagnetic interference, and zero drift. It can be used to measure settlement in tunnels, pipe galleries, buildings, hydraulic engineering, and geological engineering, including uneven settlement of pipe galleries and earth-rock dams with large settlement. It can measure not only the settlement of each dam section but also the relative settlement between two objects. Attached Figure Description

[0028] Figure 1 The principle and optical path diagram of the fiber optic Fabry-Perot interferometer provided in the embodiments of the present invention;

[0029] Figure 2 A schematic diagram of a settlement sensor structure based on fiber optic Fabry-Perot interferometry provided in an embodiment of the present invention;

[0030] Figure 3 Interference spectra of sedimentation sensors under different sedimentation amounts / liquid levels provided in embodiments of the present invention;

[0031] Figure 4 A graph showing the relationship between the length of the Fabry-Perot interferometer cavity and the amount of sedimentation / liquid level change provided in an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the structure when the float is placed at an angle in an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the settlement sensor system provided in an embodiment of the present invention.

[0034] Explanation of reference numerals in the attached diagram: 1. First reflection point; 2. Second reflection point; 3. Transmission optical fiber; 4. Cantilever beam; 5. Float; 6. Horizontal beam for fixing optical fiber; 7. Optical fiber sealing connector; 8. Liquid; 9. Sedimentation sensor housing; 10. Spectral demodulator; 11. Liquid passage pipe; 12. Water tank. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0036] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] Embodiment 1 of the present invention provides a settlement sensor based on the fiber optic Fabry-Perot interferometry principle, comprising: a settlement sensor housing 9, an L-shaped cantilever beam, and a Fabry-Perot interferometry cavity.

[0040] like Figure 2As shown, an L-shaped cantilever beam is fixed inside the sedimentation sensor housing 9. The L-shaped cantilever beam consists of a cantilever beam crossbeam 4 and a float 5. A point above the cantilever beam crossbeam 4 is the second reflection point 2. One end of the cantilever beam crossbeam 4 is rigidly connected to the inner wall of the sensor housing 9, and the other end of the cantilever beam crossbeam 4 is fixed with a vertical float 5. A part of the float 5 is inserted into the liquid 8. The liquid 8 generates buoyancy on the float 5, causing the cantilever beam crossbeam 4 to bend, thereby causing the second reflection point 2 to move vertically.

[0041] The material of the cantilever beam 4 is not limited; it can be metal, ceramic, etc., as long as it is an elastic body. There are no restrictions on bending, as long as it can only undergo elastic deformation and not plastic deformation.

[0042] The optical fiber 3 is fixed to the sensor housing 9 by the horizontal beam 6 for fixing the optical fiber. The axis of the optical fiber 3 is perpendicular to the plane where the second reflection point 2 is located. The end face of the optical fiber 3 is the first reflection point 1. The two reflection points form a Fabry-Perot interference cavity.

[0043] The end of the cantilever beam 4 is fixedly connected to the sensor housing 9. A reflector, i.e., the second reflection point 2, is fixed on the top surface of the beam 4. The reflector can be positioned at any point on the beam. The farther away from the sensor housing 9, the higher the sensitivity of the sensor. This is because the farther away from the housing, the greater the arm length, the greater the deflection, and thus the more sensitive the sensor. Generally, the deflection is proportional to the Nth power of the distance between the reflector and the fixed end. This N is related to the type of load; for example, N is different for uniformly distributed loads and concentrated loads, but N≥1.

[0044] The normal to the reflector is perpendicular to the cantilever beam 4, and is in the vertical direction.

[0045] The transmission optical fiber 3 is fixed to the sensor housing 9 by a horizontal beam 6 for fixing optical fibers. The horizontal beam 6 is perpendicular to the housing 9, and the transmission optical fiber 3 is in the vertical direction and perpendicular to the horizontal beam 6. The axis of the fixed optical fiber 3 coincides with the axis of the second reflection point 2.

[0046] like Figure 1 As shown, the optical components of the settlement sensor optical path diagram in this embodiment consist of a transmission optical fiber 3, a first reflection point 1, a cantilever beam 4, and a second reflection point 2.

[0047] The first reflection point 1 is the lower end face of the transmission optical fiber 3, which is perpendicular to the axis of the transmission optical fiber 3; a reflector is provided on the side of the cantilever beam 4 near the transmission optical fiber 3, and its reflectivity is between 0% and 100%. The normal of the reflector is perpendicular to and intersects the axis of the cantilever beam. The reflector is the second reflection point 2.

[0048] It is worth noting that a reflector can be fixed separately above the cantilever beam 4, or the top of the beam can be polished to serve as a reflector.

[0049] The multiple reflected light between the first reflection point 1 and the second reflection point 2 interferes with each other, forming a Fabry-Perot interference cavity; the other end of the transmission optical fiber 3 is connected to a spectrum demodulator 10, which can emit light waves and collect the Fabry-Perot interference spectrum. The interference spectrum is usually a sine curve, such as... Figure 3 As shown.

[0050] When the sedimentation changes, the liquid level inside the sedimentation sensor changes, causing a change in the length submerged by float 5 and the buoyancy. This buoyancy acts on the end of the cantilever beam 4, causing it to bend. This results in the second reflection point 2, fixed above the cantilever beam 4, moving and changing the distance between the first reflection point 1 and the second reflection point 2, i.e., a change in the Fabry-Perot cavity length. By measuring the calibration formula and the change in the Fabry-Perot cavity length, the change in liquid level and the sedimentation can be determined.

[0051] Figure 3 The reflection spectra (Fabry-Perot interferometry spectra) of the sedimentation / level sensor were measured using a spectrometer 10 at sedimentation amounts of 0, 60, 140, and 200 mm. The interferometric cavity lengths under different sedimentation amounts were calculated through demodulation, and a linear relationship was established between the change in interferometric cavity length y and the sedimentation amount x: y = -1.0336x. Figure 4 As shown.

[0052] like Figure 5 As shown, the axis of float 5 does not have to be placed vertically. For example, float 5 can be placed at an angle, with its axis at an angle to the vertical direction, without affecting the linearity between the amount of sedimentation and the change in cavity length.

[0053] Embodiment 2 of the present invention provides a sedimentation measurement system based on fiber optic Fabry-Perot interferometry, including the aforementioned sedimentation sensor, liquid inlet pipe 11, and water tank 12, as shown below. Figure 6 As shown, a water tank is set at the reference point, and the liquid areas of multiple sedimentation sensors are connected by a liquid passage pipe. The liquid area of ​​one of the sedimentation sensors is connected to the water tank through the liquid passage pipe.

[0054] More preferably, the reference point is a location where no settlement occurs.

[0055] Embodiment 3 of the present invention provides a settlement measurement method, comprising the following steps:

[0056] Step 1: Connect multiple settlement sensors in series at the same elevation as the measurement site;

[0057] Step 2: Set up a water tank at a reference point where no settlement occurs, connect the liquid area of ​​the water tank with the liquid area of ​​the settlement sensor, and connect the liquid areas of all settlement sensors.

[0058] Step 3: Insert another sedimentation sensor into the reference point tank as the liquid level calibration of the reference point, and use the sedimentation sensor to measure the liquid change in the reference point tank.

[0059] Step 4: Use a series of sedimentation sensors connected in series to measure the liquid level changes inside the sedimentation sensors respectively;

[0060] Step 5: Subtract the liquid level change in the reference tank from the liquid level change measured by each sedimentation sensor to obtain the actual sedimentation at the test point.

[0061] In a preferred but non-limiting embodiment of the present invention, the settlement sensor in step 1 is one or more settlement sensors, and the multiple settlement sensors are installed at equal intervals at the same height to form a settlement sensor system.

[0062] The liquid area of ​​the reference point tank is connected to the sedimentation sensor closest to the tank in the sedimentation sensor system.

[0063] More preferably, in step 4, the method for measuring the liquid level change using the sedimentation sensor is as follows:

[0064] Plot a graph showing the relationship between the length of the Fabry-Perot interferometer cavity and the amount of settlement.

[0065] The relationship curve was fitted to ensure that the sedimentation amount (liquid level change) and the length of the Fabry-Perot interferometer cavity satisfy a linear relationship.

[0066] The relationship between the length of the Fabry-Perot interferometer cavity and the amount of sedimentation was obtained.

[0067] like Figure 4 As shown, a preferred but non-limiting formula for calculating settlement in this invention is as follows:

[0068] y = -1.0336x

[0069] Where: y represents the sedimentation amount (liquid level change), in mm; x represents the change in the length of the Fabry-Perot interference cavity, in μm.

[0070] Compared with the prior art, the beneficial effects of the present invention include at least:

[0071] The settlement sensor provided by this invention is based on the fiber optic Fabry-Perot interferometry principle. The buoyancy of a float causes a change in the deflection of an L-shaped cantilever beam, thus changing the length of the Fabry-Perot interferometry cavity. Based on the calibration formula between the Fabry-Perot interferometry cavity length and the settlement (liquid level change), the settlement (liquid level change) can be measured. Because the components of the Fabry-Perot interferometer are non-contact, fatigue and low accuracy issues caused by object deformation are avoided, and electromagnetic interference is also eliminated. The settlement sensor provided by this invention offers advantages such as high accuracy, long lifespan, resistance to electromagnetic interference, and zero drift. It can be used to measure settlement in tunnels, pipe galleries, buildings, hydraulic engineering projects, and geological engineering projects, including uneven settlement of pipe galleries and earth-rock dams with large settlement. It can measure not only the settlement of each dam section but also the relative settlement between two objects.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A sedimentation sensor based on fiber optic Fabry-Perot interferometry, comprising: The sedimentation sensor housing (9), the L-shaped cantilever beam, and the Fabry-Perot interferometer cavity are characterized by: An L-shaped cantilever beam is fixed inside the housing (9) of the sedimentation sensor. The L-shaped cantilever beam includes a cantilever beam crossbeam (4) and a float (5). The upper surface of the cantilever beam crossbeam (4) is the second reflection point (2). One end of the cantilever beam crossbeam (4) is rigidly connected to the inner wall of the sensor housing (9), and the other end is fixed with a vertical float (5). The float (5) is inserted into the liquid (8), and the liquid (8) generates buoyancy on the float (5). An optical fiber (3) is provided inside the housing (9) of the sedimentation sensor. The end face of the optical fiber (3) is the first reflection point (1). The first reflection point (1) and the second reflection point (2) form a Fabry-Perot interference cavity. The optical fiber (3) is fixed to the sensor housing (9) by a horizontal beam (6) for fixing the optical fiber. The horizontal beam (6) is perpendicular to the housing (9). The optical fiber (3) is in the vertical direction and perpendicular to the horizontal beam (6). The axis of the fixed optical fiber (3) coincides with the axis of the second reflection point (2). When the sedimentation measurement is in progress, the cantilever beam can be bent and changes with the position of the liquid (8) in the sedimentation sensor. The distance between the first reflection point (1) and the second reflection point (2) changes accordingly, and the length of the Fabry cavity changes, thereby determining the liquid level change and sedimentation.

2. The sedimentation sensor based on fiber optic Fabry-Perot interferometry according to claim 1, characterized in that: One end of the optical fiber (3) is the first reflection point (1), and the other end is connected to a spectrometer (10) for emitting light waves and collecting Fabry-Perot interference spectra.

3. The sedimentation sensor based on fiber optic Fabry-Perot interferometry according to claim 1, characterized in that: The second reflection point (2) is a reflector located on the cantilever beam (4) near the transmission optical fiber (3), with a reflectivity between 0% and 100%. The normal of the reflector is perpendicular to and intersects the axis of the L-shaped cantilever beam.

4. The sedimentation sensor based on fiber optic Fabry-Perot interferometry according to claim 1, characterized in that: The end of the cantilever beam (4) is fixed with a vertically placed float (5). The float (5) and the cantilever beam (4) are an integral part. The float (5) is always inserted into the liquid (8). When the sedimentation changes, the length of the float (5) submerged in the liquid (8) is different, which makes the buoyancy of the float (5) different, causing the cantilever beam (4) to bend, which causes the second reflection point (2) to move and change the distance between the two reflection points.

5. The sedimentation sensor based on fiber optic Fabry-Perot interferometry according to claim 4, characterized in that: The float (5) can be tilted, and its axis forms a set angle with the vertical direction.

6. A settlement measurement system based on fiber optic Fabry-Perot interferometry, characterized in that: Includes a sedimentation sensor, a liquid inlet pipe (11), and a water tank (12) as described in any one of claims 1-5. The water tank (12) is set at a reference point where sedimentation does not occur. The liquid areas of multiple sedimentation sensors are connected through the liquid inlet pipe (11). The liquid area of ​​one of the sedimentation sensors is connected to the water tank (12) through the liquid inlet pipe (11).

7. A settlement measurement method, based on the fiber optic Fabry-Perot interferometry-based settlement sensor system described in claim 6, characterized in that: Includes the following steps: Multiple settlement sensors are connected in series and installed at the same elevation as the measurement site; A water tank is set up at a reference point where no settlement occurs, and the liquid area of ​​the water tank is connected to the liquid areas of multiple settlement sensors. Another sedimentation sensor is inserted into the reference point tank as the liquid level calibration of the reference point, and the sedimentation sensor is used to measure the liquid change in the reference point tank. The liquid level change inside each sedimentation sensor in the sedimentation measurement system is measured separately. The actual settlement at the test point is obtained by subtracting the liquid level change in the reference tank from the liquid level change measured by each settlement sensor in the settlement measurement system.

8. A settlement measurement method according to claim 7, characterized in that: The multiple settlement sensors are installed at equal intervals at the same height.

9. A settlement measurement method according to claim 7, characterized in that: The method for measuring liquid level changes using the sedimentation sensor is as follows: Plot a graph showing the relationship between the length of the Fabry-Perot interferometer cavity and the amount of settlement. Linear fitting was performed on the calibration curve to ensure a linear relationship between the settlement and the length of the Fabry-Perot interferometer cavity; A linear relationship between the length of the Fabry-Perot interferometer cavity and the amount of sedimentation was obtained.

Images