Settlement sensor based on optical fiber Fabry-Perot interference and measuring system and method

Abstract

The invention relates to the technical field of settlement sensors, in particular to a settlement sensor based on optical fiber Fabry-Perot interference and a measuring system and method.The settlement sensor comprises a settlement sensor shell, an L-shaped cantilever beam structure and a Fabry-Perot interference cavity, and an L-shaped cantilever beam and the Fabry-Perot interference cavity are arranged in the settlement sensor shell; one end of the optical fiber and one end of the cantilever beam are fixed on a shell of the settlement sensor; when the settlement amount is changed, the liquid level in the settlement sensor is changed, so that the length and the buoyancy which submerge the floater are changed, the cantilever beam is stressed and bent to cause the reflector fixed above the cantilever beam to move, and the displacement distance of the reflector is measured through the Fabry-Perot interference cavity, so that the liquid level change amount and the settlement amount are determined. The device has the advantages of being high in measurement precision, good in anti-fatigue performance, long in service life, free of electromagnetic interference and the like, and is suitable for settlement monitoring of electric power infrastructures, including differential settlement of structures such as pipe galleries and hydropower stations.

Description

Technical Field

[0001] The present invention relates to the technical field of subsidence monitoring sensors, and in particular to a subsidence sensor based on optical fiber Fabry-Perot interferometry and a measuring system and method. Background Art

[0002] Settlement is an important indicator for monitoring urban integrated pipelines. For example, uneven settlement of a transmission pipeline will crack the lining concrete, allowing pore water in the soil to enter the pipeline and soak the power facilities, causing safety problems and shortening their service life.

[0003] At present, the settlement monitoring of urban integrated pipe corridors usually uses static leveling and other methods. However, the traditional static level based on electrical principles has problems such as weak anti-electromagnetic interference ability, while the static level of fiber Bragg grating has problems such as low accuracy and insufficient long-term stability.

[0004] Therefore, it is very necessary to develop a settlement measurement device with advantages such as good long-term stability and strong anti-electromagnetic interference ability. Summary of the invention

[0005] In order to solve the deficiencies in the prior art, the present invention provides a settlement sensor and a measurement system and method based on optical fiber Fabry-Perot interferometry, which have high measurement accuracy, long service life, are not affected by electromagnetic interference, and can be applied to settlement monitoring of power infrastructure, including uneven settlement of pipeline corridors and earth-rock dams with large settlement.

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

[0007] The first aspect of the present invention discloses a sedimentation sensor based on optical fiber Fabry-Perot interference, comprising: a sedimentation sensor housing, an L-shaped cantilever beam and a Fabry-Perot interference cavity, wherein an L-shaped cantilever beam is fixed inside the sedimentation sensor housing, and the L-shaped cantilever beam comprises 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 a float in a vertical direction is fixed to the other end thereof, the float is inserted into a liquid, and the liquid generates buoyancy on the float;

[0008] An optical fiber is arranged in the housing of the sedimentation sensor, the end face of the optical fiber is a first reflection point, and a Fabry-Perot interference cavity is formed between the first reflection point and the second reflection point;

[0009] When measuring the sedimentation, the cantilever beam can bend and change 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 Fabry-Perot cavity length changes, thereby determining the liquid level change and sedimentation.

[0010] Preferably, the optical fiber is fixed to the sensor housing by a horizontal beam for fixing the optical fiber, the horizontal beam is perpendicular to the housing, the optical fiber is in a 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 spectrum demodulator for emitting light waves and collecting Fabry-Perot interference spectra.

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

[0013] Preferably, a float placed in a vertical direction is fixed to the end of the cantilever beam cross beam, the float and the cantilever beam cross beam are an integral part, the float is always inserted in the liquid, when the sedimentation amount changes, the length of the float immersed in the liquid is different, so that the buoyancy of the float is different, thereby causing the cantilever beam cross beam to bend, driving the second reflection point to move, and changing the distance between the two reflection points.

[0014] Preferably, the float can be arranged 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 Fabry-Perot interferometry, including the sedimentation sensor, a liquid pipe and a water tank. The water tank is set at a reference point where no sedimentation occurs, and the liquid areas of multiple sedimentation sensors are connected by the liquid pipe. The liquid area of ​​one of the sedimentation sensors is connected to the water tank through the liquid pipe.

[0016] The third aspect of the present invention discloses a method for measuring sedimentation, based on the sedimentation sensor system based on optical fiber Fabry-Perot interferometry, comprising the following steps:

[0017] Install multiple settlement sensors in series at equal heights of the measurement site;

[0018] A water tank is arranged at a reference point where no sedimentation occurs, and a liquid area of ​​the water tank is connected to liquid areas of a plurality of sedimentation sensors;

[0019] Insert another sedimentation sensor into the reference point water tank as the reference point liquid level calibration, and use the sedimentation sensor to measure the liquid change in the reference point water tank;

[0020] Use each sedimentation sensor in the sedimentation measurement system to measure the level change of the liquid in the sedimentation sensor respectively;

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

[0022] Preferably, the plurality of sedimentation sensors are installed at the same height with equal spacing.

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

[0024] Draw a curve diagram of the relationship between the Fabry-Perot interferometer cavity length and the sedimentation amount;

[0025] A linear fit is performed on the calibration curve to ensure that the sedimentation amount and the Fabry-Perot interferometer cavity length satisfy a linear relationship.

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

[0027] The settlement sensor provided by the present invention is based on the principle of optical fiber Fabry-Perot interference. The change of the Fabry-Perot interference cavity length is obtained by the change of the deflection of the cantilever beam. According to the calibration formula between the Fabry-Perot interference cavity length and the settlement (liquid level change), the settlement (liquid level change) can be measured. Since the components of the Fabry-Perot interference are non-contact, there will be no problems of fatigue and low precision due to the deformation of the object, and there is no problem of electromagnetic interference. The settlement sensor provided by the present invention has the beneficial effects of high precision, long life, anti-electromagnetic interference and no zero drift. It can be used to measure the settlement in tunnels, pipe corridors, buildings, water conservancy projects and geological projects, including uneven settlement of pipe corridors and earth-rock dams with large settlement. It can not only measure the settlement of each dam section, but also measure the relative settlement between two objects. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

[0032] Figure 5 It is a structural schematic diagram of a float placed obliquely in an embodiment of the present invention;

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

[0034] Explanation of the reference numerals: 1. first reflection point; 2. second reflection point; 3. transmission optical fiber; 4. cantilever beam; 5. float; 6. horizontal beam for fixing the optical fiber; 7. optical fiber sealing joint; 8. liquid; 9. sedimentation sensor housing; 10. spectrum demodulator; 11. liquid pipe; 12. water tank. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0036] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] In addition, 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 sedimentation sensor based on the principle of optical fiber Fabry-Perot interference, including: a sedimentation sensor housing 9, an L-shaped cantilever beam, and a Fabry-Perot interference cavity.

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

[0041] The material of the cantilever beam 4 is not limited, and it can be metal, ceramic, etc., as long as it is an elastic body, and the bending is not limited, as long as it can only undergo elastic deformation without plastic deformation.

[0042] The optical fiber 3 is fixed to the sensor housing 9 through a 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, and a Fabry-Perot interference cavity is formed between the two reflection points.

[0043] The end of the cantilever beam crossbeam 4 is fixedly connected to the sensor housing 9. A reflector, namely the second reflection point 2, is fixed on the top surface of the crossbeam 4. The position of the reflector can be at any point on the crossbeam. The farther from the sensor housing 9, the higher the sensitivity of the sensor. Because the farther from the housing, the longer the arm, the greater the deflection, and the more sensitive. Generally, the deflection is proportional to the Nth power of the distance from the reflector to the fixed end. This N is related to the load type. For example, N is different for uniformly distributed load and concentrated load, but N≥1.

[0044] The normal line of 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 through a horizontal beam 6 for fixing the optical fiber. The horizontal beam 6 is perpendicular to the housing 9. The transmission optical fiber 3 is in a 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 device of the optical path diagram of the sedimentation sensor in this embodiment is composed of a transmission optical fiber 3, a first reflection point 1, a cantilever beam 4 and a second reflection point 2.

[0047] Among them, 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 one side of the cantilever beam 4 close to the transmission optical fiber 3, and its reflectivity is between 0% and 100%, and the normal of the reflector is perpendicular to and intersects with the axis of the cantilever beam, and the reflector is the second reflection point 2.

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

[0049] The multiple reflected lights between the first reflection point 1 and the second reflection point 2 interfere with each other to form 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 Fabry-Perot interference spectra. The interference spectrum is usually a sine curve, such as Figure 3 shown.

[0050] When the amount of sedimentation changes, the liquid level in the sedimentation sensor changes, causing the length of the float 5 and the buoyancy to change. The buoyancy acts on the end of the cantilever beam 4, causing the cantilever beam 4 to bend, resulting in the movement of the second reflection point 2 fixed above the cantilever beam 4, changing the distance between the first reflection point 1 and the second reflection point 2, that is, the Fabry-Perot cavity length changes. By measuring the calibration formula and the change in the Fabry-Perot cavity length, the liquid level change and the amount of sedimentation can be determined.

[0051] Figure 3 The reflection spectrum of the sedimentation / liquid level sensor measured by the spectrum demodulator 10 when the sedimentation amount is 0, 60, 140, and 200 mm, namely, the Fabry-Perot interference spectrum. The interference cavity length under different sedimentation amounts is calculated by demodulation, and the linear relationship between the change of the interference cavity length y and the sedimentation amount x is calibrated, y = -1.0336x, such as Figure 4 shown.

[0052] like Figure 5 As shown, the axis of the float 5 may not be placed in the vertical direction. For example, the float 5 may be placed obliquely, and the axis has an angle with the vertical direction, which does not affect the linearity between the sedimentation amount and the cavity length change.

[0053] Embodiment 2 of the present invention provides a sedimentation measurement system based on optical fiber Fabry-Perot interferometry, including the sedimentation sensor, the liquid pipe 11 and the water tank 12, as shown in FIG. Figure 6 As shown, a water tank is arranged at the reference point, the liquid areas of a plurality of sedimentation sensors are connected by a liquid through pipe, and the liquid area of ​​one of the sedimentation sensors is connected to the water tank through the liquid through pipe.

[0054] Further preferably, the reference point is a position where no settlement occurs.

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

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

[0057] Step 2: a water tank is set at a reference point where no settlement occurs, the liquid area of ​​the water tank is connected to the liquid area of ​​the settlement sensor, and the liquid areas of all the settlement sensors are connected;

[0058] Step 3, insert another sedimentation sensor into the reference point water tank as the reference point liquid level calibration, and use the sedimentation sensor to measure the liquid change in the reference point water tank;

[0059] Step 4, using a series of sedimentation sensors connected in series to measure the level change of the liquid in the sedimentation sensors respectively;

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

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

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

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

[0064] Draw a curve diagram of the relationship between the Fabry-Perot interferometer cavity length and the sedimentation amount;

[0065] Fitting the relationship curve graph makes the sedimentation amount (liquid level change) and the Fabry-Perot interferometer cavity length satisfy a linear relationship;

[0066] The relationship between the Fabry-Perot interference cavity length and the sedimentation amount is obtained.

[0067] like Figure 4 As shown, a preferred but non-limiting sedimentation calculation formula in the present invention is as follows:

[0068] y=-1.0336x

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

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

[0071] The settlement sensor provided by the present invention is based on the principle of optical fiber Fabry-Perot interference. The deflection of the L-shaped cantilever beam is driven to change by the buoyancy of the float, so that the length of the Fabry-Perot interference cavity changes. According to the calibration formula between the length of the Fabry-Perot interference cavity and the settlement (liquid level change), the settlement (liquid level change) can be measured. Since the components of the Fabry-Perot interference are non-contact, there will be no problems of fatigue and low precision due to object deformation, and there is no problem of electromagnetic interference. The settlement sensor provided by the present invention has the beneficial effects of high precision, long life, anti-electromagnetic interference and no zero drift. It can be used to measure the settlement in tunnels, pipe corridors, buildings, water conservancy projects and geological projects, including uneven settlement of pipe corridors and earth-rock dams with large settlement. It can not only measure the settlement of each dam section, but also measure 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 rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A sedimentation sensor based on optical fiber Fabry-Perot interferometry, comprising: The sedimentation sensor housing (9), the L-shaped cantilever beam and the Fabry-Perot interference cavity are characterized by: An L-shaped cantilever beam is fixed inside the housing (9) of the sedimentation sensor, and the L-shaped cantilever beam comprises a cantilever beam cross beam (4) and a float (5); the upper surface of the cantilever beam cross beam (4) is a second reflection point (2), one end of the cantilever beam cross beam (4) is rigidly connected to the inner wall of the sensor housing (9), and a float (5) is fixed to the other end thereof in a vertical direction, and the float (5) is inserted into the liquid (8), and the liquid (8) generates buoyancy on the float (5); An optical fiber (3) is arranged in the housing (9) of the sedimentation sensor, the end face of the optical fiber (3) is a first reflection point (1), and a Fabry-Perot interference cavity is formed between the first reflection point (1) and the second reflection point (2); When in the sedimentation measurement state, the cantilever beam can bend and change with the position of the liquid (8) in the sedimentation sensor, and the distance between the first reflection point (1) and the second reflection point (2) changes accordingly, and the Fabry-Perot cavity length changes, thereby determining the liquid level change and the sedimentation amount.

2. The optical fiber Fabry-Perot interferometer-based sedimentation sensor according to claim 1, characterized in that: The optical fiber (3) is fixed to the sensor housing (9) via 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 a vertical direction and perpendicular to the horizontal beam (6), and the axis of the fixed optical fiber (3) coincides with the axis of the second reflection point (2).

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

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

5. The sedimentation sensor based on optical fiber Fabry-Perot interferometry according to claim 1 is characterized in that: A float (5) placed in a vertical direction is fixed to the end of the cantilever beam (4); the float (5) and the cantilever beam (4) are an integral part; the float (5) is always inserted into the liquid (8); when the amount of sedimentation changes, the length of the float (5) immersed in the liquid (8) is different, so that the buoyancy of the float (5) is different, thereby causing the cantilever beam (4) to bend, driving the second reflection point (2) to move, and changing the distance between the two reflection points.

6. The sedimentation sensor based on optical fiber Fabry-Perot interferometry according to claim 5 is characterized in that: The float (5) can be arranged tilted, with its axis forming a set angle with the vertical direction.

7. A sedimentation measurement system based on fiber Fabry-Perot interferometry, characterized in that: It comprises a sedimentation sensor, a liquid passing pipe (11) and a water tank (12) as described in any one of claims 1 to 6, wherein the water tank (12) is arranged at a reference point where no sedimentation occurs, the liquid areas of a plurality of sedimentation sensors are connected via the liquid passing pipe (11), and the liquid area of ​​one of the sedimentation sensors is connected to the water tank (12) via the liquid passing pipe (11).

8. A sedimentation measurement method, based on a sedimentation sensor system based on fiber Fabry-Perot interferometry as claimed in claim 7, characterized in that: The following steps are involved: Install multiple settlement sensors in series at equal heights of the measurement site; A water tank is arranged at a reference point where no sedimentation occurs, and a liquid area of ​​the water tank is connected to liquid areas of a plurality of sedimentation sensors; Insert another sedimentation sensor into the reference point water tank as the reference point liquid level calibration, and use the sedimentation sensor to measure the liquid change in the reference point water tank; Use each sedimentation sensor in the sedimentation measurement system to measure the level change of the liquid in the sedimentation sensor respectively; The actual settlement of the measured point is obtained by subtracting the liquid level change in the reference point water tank from the liquid level change measured by each settlement sensor in the settlement measurement system.

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

10. A sedimentation measurement method according to claim 8, characterized in that: The method for measuring the liquid level change of the sedimentation sensor is as follows: Draw a curve diagram of the relationship between the Fabry-Perot interferometer cavity length and the sedimentation amount; A linear fit is performed on the calibration curve to ensure that the sedimentation amount and the Fabry-Perot interferometer cavity length satisfy a linear relationship. The linear relationship between the Fabry-Perot interference cavity length and the sedimentation amount is obtained.

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