A multi-parameter integrated acquisition fiber optic sensor and its monitoring system

Abstract

This invention belongs to the field of sensor technology. To address the challenge of existing sensors simultaneously achieving high-precision monitoring of both static and dynamic signals, this invention proposes a multi-parameter integrated fiber optic sensor and its monitoring system. The sensing cavity is divided axially into a static signal sensing area and a dynamic signal sensing area. The static signal sensing area utilizes multi-core optical fibers, each etched with a fiber grating. Wavelength demodulation of the static signal is achieved by adjusting the center wavelength shift of the fiber gratings. The dynamic signal sensing area includes a dynamic signal sensing unit, which comprises an F-P air microcavity formed between the end faces of the multi-core optical fibers. Intensity demodulation of the dynamic signal is achieved by varying the length of the F-P air microcavity. This invention employs a composite demodulation mechanism combining wavelength modulation and intensity modulation, achieving decoupled acquisition of static strain, temperature, and dynamic vibration within a single sensor.

Description

Technical Field

[0001] This invention belongs to the field of sensor-related technology, and in particular relates to a multi-parameter integrated acquisition fiber optic sensor and its monitoring system. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In fields such as structural health monitoring, geological disaster early warning, and industrial equipment operation status monitoring, dynamic and static loads are often intertwined and superimposed. Achieving highly reliable acquisition and decoupled monitoring of dynamic and static signals is crucial to ensuring equipment safety and structural stability. Currently, traditional electrical signal sensors are large in size, have weak electromagnetic interference resistance, and limited dynamic measurement range, making it difficult to meet the high-precision measurement requirements of complex industrial environments. In contrast, fiber optic sensors, with their significant advantages such as electromagnetic interference resistance, corrosion resistance, and high sensitivity, have become a current research hotspot.

[0004] In static signal monitoring, existing technologies primarily convert changes in external physical quantities into strain in fiber optic gratings (FBGs), utilizing center wavelength drift to acquire signals. However, strain measurements are highly susceptible to interference from ambient temperature. Although current research attempts to introduce temperature-compensated gratings or utilize differential operations in multi-core fibers to counteract temperature effects, under complex real-world conditions, when the fiber twists, the path length and spatial position of the eccentric core shift. This twisting effect not only leads to inaccurate strain assessments but can even cause the torsional signal to be misread as periodic axial strain, severely impacting monitoring accuracy.

[0005] In dynamic signal monitoring, existing technologies mostly employ a scheme coupling mechanical vibration pickup structures with fiber optic arrays (FBGs). Limited by sensor size and structural damping, these sensors generally suffer from low sampling frequencies or sluggish dynamic response, making it difficult to capture transient vibration information within the structure. In recent years, two-photon 3D printing technology has provided a new approach for miniaturized monitoring, enabling the acquisition of high-frequency signals by integrating micro / nano vibration pickup structures at the fiber optic endface. However, most existing micro / nano sensors are uniaxial designs, exhibiting low sensitivity when dealing with non-axial vibration acquisition, easily leading to the loss of crucial multidimensional signals.

[0006] In summary, existing fiber optic sensing technologies suffer from limitations in joint monitoring of static and dynamic signals, including limited functionality and severe coupling interference. This makes it difficult to simultaneously achieve high-precision monitoring of both static signals (such as strain and temperature) and dynamic signals (such as multidimensional vibration and acceleration). Therefore, designing a self-decoupled integrated fiber optic sensor that effectively suppresses torsional interference, possesses temperature self-compensation capabilities, and can simultaneously acquire multi-angle, high-sensitivity static and dynamic signals is a pressing technical challenge in the field of structural health monitoring. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention provides a multi-parameter integrated acquisition fiber optic sensor and its monitoring system, which adopts a composite demodulation mechanism of wavelength modulation and intensity modulation in parallel, and realizes the decoupled acquisition of static temperature, strain and dynamic vibration signals in a single sensor.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a multi-parameter integrated acquisition fiber optic sensor, comprising: a sensor housing, a sensor base, and a sensing cavity formed by the sensor housing and the sensor base;

[0010] The sensing cavity is divided into a static signal sensing area and a dynamic signal sensing area along the axial direction.

[0011] The sensing element of the static signal sensing area adopts a multi-core optical fiber, and fiber gratings are respectively engraved on the multi-core optical fiber. The wavelength demodulation of the static signal is achieved by the center wavelength drift of the fiber gratings.

[0012] The dynamic signal sensing area is provided with a dynamic signal sensing unit, which includes an FP air microcavity formed between each fiber core end face of the multi-core optical fiber. The intensity demodulation of the dynamic signal is achieved by changing the cavity length of the FP air microcavity.

[0013] In one embodiment, the multi-core optical fiber includes a central core and peripheral sensing cores. The peripheral sensing cores are arranged in a square symmetrical manner with the central core as the center. A strain-sensitive material is filled between the inner wall of the sensor housing and the multi-core optical fiber.

[0014] In one implementation, the dynamic signal sensing unit is fabricated in situ using two-photon polymerization 3D printing technology. The dynamic signal sensing unit includes a central cylindrical support column and orthogonally symmetrical main-auxiliary cantilever beams. The main-auxiliary cantilever beams located on the same axial line sense horizontal signals in the same dimension. The main-auxiliary cantilever beams modulate the cavity length of the corresponding fiber core end face FP air microcavity through coordinated vibration in different directions.

[0015] In one embodiment, the main-auxiliary symmetrical cantilever beam includes a main cantilever beam and an auxiliary cantilever beam. The main cantilever beam adopts a T-shaped structure, and the auxiliary cantilever beam adopts a Π-shaped structure. When there is vertical vibration, all the main-auxiliary symmetrical cantilever beams vibrate synchronously in the vertical direction. When there is horizontal vibration, the auxiliary cantilever beams of the main-auxiliary symmetrical cantilever beams on the same axial line swing in the horizontal direction and drive the corresponding main cantilever beams to vibrate.

[0016] In one embodiment, the main cantilever beam includes a first elastic cantilever beam and an end mass block, the first elastic cantilever beam having a hollow structure; one end of the first elastic cantilever beam is connected to the central cylindrical support, and the other end of the first elastic cantilever beam is connected to the end mass block;

[0017] The auxiliary cantilever beam includes a second elastic cantilever beam and an auxiliary mass block. One end of the second elastic cantilever beam is connected to the end mass block, and the other end of the second elastic cantilever beam is connected to the auxiliary mass block.

[0018] In one implementation, the end mass block is located directly above the corresponding optical fiber, and the cross-sectional area of ​​the end mass block covers the effective light-transmitting area of ​​the fiber core; under the action of a vertical dynamic signal, the end mass block drives the elastic cantilever beam to vibrate up and down, modulating the cavity length of the FP air microcavity.

[0019] In one implementation, under the action of a dynamic signal in the horizontal direction, the auxiliary mass block vibrates in the horizontal plane. The horizontal displacement of the auxiliary mass block generates alternating inertial force and torque at the end of the main cantilever beam, which is then converted into the vertical displacement of the end mass block.

[0020] As one implementation, it further includes: a temperature-sensitive sealed cavity disposed at the end face of the central fiber core, the temperature-sensitive sealed cavity being filled with a thermosensitive liquid, and when the refractive index and volume of the thermosensitive liquid change, the temperature signal is independently monitored and decoupled in real time through the change in the reflection intensity of the central fiber core.

[0021] Secondly, the present invention provides a monitoring system based on the above-mentioned multi-parameter integrated acquisition fiber optic sensor, comprising: a pulse light generator, an optical circulator, a fan-in and fan-out device, a multi-parameter integrated acquisition fiber optic sensor, an optical splitter, a high-speed demodulator, a photodetector, a signal acquisition device, and a main control unit;

[0022] The output of the pulsed light generator is connected to the first port of the optical circulator, the second port of the optical circulator is connected to the multi-parameter integrated acquisition fiber optic sensor through the fan-in and fan-out device, and the third port of the optical circulator is connected to the input of the optical splitter.

[0023] When external dynamic and / or static signals act on the multi-parameter integrated acquisition fiber optic sensor, the optical splitter is used to split the reflected light returned by the multi-parameter integrated acquisition fiber optic sensor into two paths. One path enters the high-speed demodulator, which captures the offset of the center wavelength of the fiber optic grating in real time. The other path enters the photodetector for photoelectric conversion, and the converted electrical signal is recorded by the signal acquisition device.

[0024] The main control unit is used to calculate the offset of the center wavelength of the fiber optic grating captured by the high-speed demodulator, so as to monitor the external static signals; it is also used to decouple the electrical signals recorded by the signal acquisition device and extract the changes of the external dynamic signals.

[0025] In one implementation, the main controller is used to perform correlation analysis on the strain data of the relative fiber cores using a cosine similarity algorithm, to identify and calibrate the misalignment of sensing points generated during the installation of the multi-core optical fiber based on the correlation analysis results, and to eliminate the interference of torsional effect on static load measurement through a vector decoupling algorithm.

[0026] The above one or more technical solutions have the following beneficial effects:

[0027] In this invention, the sensing cavity is divided into a static signal sensing area and a dynamic signal sensing area along the axial direction. The sensing element in the static signal sensing area uses a multi-core optical fiber, with fiber gratings etched on each core. Wavelength demodulation of the static signal is achieved by adjusting the center wavelength shift of the fiber gratings. The dynamic signal sensing area is equipped with a dynamic signal sensing unit, which includes an FP air microcavity formed between the end faces of each core of the multi-core optical fiber. Intensity demodulation of the dynamic signal is achieved by varying the cavity length of the FP air microcavity. By employing a composite demodulation mechanism that combines wavelength modulation and intensity modulation, decoupled acquisition of static and dynamic signals is achieved within a single sensor.

[0028] In this invention, the multi-core optical fiber includes a central core and peripheral sensing cores. The peripheral sensing cores are arranged in a square symmetrical manner. This layout ensures that when the optical fiber bends under external load, the peripheral sensing cores follow a symmetrical or antisymmetrical strain distribution law.

[0029] In this invention, the main-auxiliary symmetrical cantilever beam includes a main cantilever beam and an auxiliary cantilever beam. The main cantilever beam adopts a T-shaped structure, and the auxiliary cantilever beam adopts a Π-shaped structure. When vertical vibration occurs, all main-auxiliary symmetrical cantilever beams vibrate synchronously along the vertical direction. When horizontal vibration occurs, the auxiliary cantilever beams of the main-auxiliary symmetrical cantilever beams on the same axial line swing horizontally, driving the corresponding main cantilever beams to vibrate. The main-auxiliary symmetrical cantilever beam of this invention can achieve triaxial acquisition, thereby significantly improving the acquisition sensitivity of non-axial signals and effectively preventing the loss of key feature signals.

[0030] In this invention, a hollow structure is provided on the first elastic cantilever beam to improve the response sensitivity to weak vibrations by reducing its equivalent stiffness.

[0031] In this invention, to eliminate temperature cross-interference, a temperature-sensitive sealed cavity is provided at the end face of the central fiber core in the dynamic signal sensing area. When temperature changes cause changes in the refractive index and volume of the thermosensitive liquid, the independent monitoring and real-time decoupling of the temperature signal is achieved by monitoring the change in the reflection intensity of the central fiber core.

[0032] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0034] Figure 1 This is a schematic diagram of the multi-parameter integrated acquisition fiber optic sensor structure provided in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the static signal sensing structure of the multi-parameter integrated acquisition fiber optic sensor provided in an embodiment of the present invention; wherein, (a) and (c) are schematic diagrams of the cross-sectional structure of the multi-core fiber in the static signal sensing area; (b) is the initial state of the grating in the static signal sensing area when it is not subjected to external force; (d) is a schematic diagram of the deformation state of gratings No. 2 and No. 4 in the static signal sensing area under the action of external force.

[0036] Figure 3 This is a schematic diagram of the dynamic signal sensing structure of the multi-parameter integrated acquisition fiber optic sensor provided in an embodiment of the present invention; wherein, (a) is the front view and (b) is the top view;

[0037] Figure 4 This is a schematic diagram of the main cantilever beam structure of the dynamic signal sensing structure provided in an embodiment of the present invention; wherein, (a) is the front view, (b) is the left view, and (c) is the top view;

[0038] Figure 5 This is a schematic diagram of the auxiliary cantilever beam structure of the dynamic signal sensing structure provided in the embodiment of the present invention; wherein, (a) is the front view, (b) is the left view, and (c) is the top view;

[0039] Figure 6 This is a block diagram of a monitoring system based on a multi-parameter integrated acquisition fiber optic sensor provided in an embodiment of the present invention;

[0040] In the diagram, 1. Multi-core optical fiber; 2. Sensor base; 3. Fiber grating; 4. Annular partition plate; 5. Fiber optic fixing bracket; 6. Dynamic signal sensing unit; 7. Dynamic signal sensing area; 8. Static signal sensing area; 9. Sensor housing; 10. Sensor fixing bracket; 11. Fiber cladding; 12. Central cylindrical support; 13. FP air microcavity; 14. Temperature-sensitive sealed cavity; 15. First elastic cantilever beam; 16. End mass block; 17. Second elastic cantilever beam; 18. Auxiliary mass block; 19. Hollow structure. Detailed Implementation

[0041] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0043] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0044] Example 1

[0045] like Figure 1 As shown, this embodiment provides a multi-parameter integrated acquisition fiber optic sensor, which adopts a composite demodulation mechanism of wavelength modulation and intensity modulation in parallel. The multi-parameter integrated acquisition fiber optic sensor mainly consists of a sensor housing 9 and a sensor base 2. The sensor housing 9 and the sensor base 2 are connected by threads, forming a sealed sensing cavity inside. The sensing cavity is divided into a static signal sensing area 8 and a dynamic signal sensing area 7 along the axial direction. The static signal sensing area 8 realizes wavelength demodulation of static strain and temperature signals by monitoring the center wavelength drift of the fiber grating 3 written on each fiber core of the multi-core fiber 1. The dynamic signal sensing area 7 modulates the cavity length of the interference microcavity through the micro-nano sensitive structure on the end face of the multi-core fiber 1, and realizes intensity demodulation of dynamic vibration and acceleration signals by utilizing the change in reflected light intensity.

[0046] In this embodiment, the static signal sensing area 8 is located in the middle of the sensor housing 9, and its core sensing element is a multi-core optical fiber 1. In this embodiment, the multi-core optical fiber 1 is preferably a five-core optical fiber, and each fiber core is engraved with a fiber grating 3.

[0047] The static signal sensing area 8 adopts a tight-encapsulation structure design: a layer of highly elastic strain-sensitive material, such as polymer or special resin, is wrapped around the outer surface of the multi-core optical fiber 1. This strain-sensitive material fills the gap between the inner wall of the sensor housing 9 and the multi-core optical fiber to efficiently convert the external radial strain into the axial strain of the fiber grating 3.

[0048] The sensor base 2 and the sensor mounting bracket 10 adopt an integrated structure. The sensor mounting bracket 10 has an optical fiber through hole in the central axis for the multi-core optical fiber 1 to pass through, so as to alleviate the damage to the optical fiber caused by external mechanical pulling.

[0049] An annular partition plate 4 is provided at the end of the static signal sensing area 8. The periphery of the annular partition plate 4 is fixed to the inner wall of the sensor housing 9 by welding or interference fit, providing radial support for the internal structure and physically isolating the dynamic signal sensing area 7.

[0050] like Figure 2 The diagram shown illustrates the principle of static signal sensing in this embodiment. When an external static signal acts on the sensor, the center wavelength of the fiber grating 3 etched in different cores of the multi-core optical fiber 1 drifts. The offset of the center wavelength is acquired in real time by a high-speed fiber demodulator and logically calculated to achieve quantitative monitoring of environmental static signals.

[0051] The multi-core optical fiber 1 comprises five cores. The central core (core 1) is located on the central axis and its wavelength drift is extracted to achieve in-situ temperature compensation during static load measurement. Peripheral sensing cores (cores 2 through 5) are distributed on the outer layer in a symmetrical square layout. Specifically, the lines connecting peripheral sensing cores 2 and 4, and 3 and 5, are perpendicular to each other. The central core (core 1) eliminates temperature interference, while peripheral sensing cores 2 through 5 sense static signals. This layout ensures that when the optical fiber bends under external load, the outer cores follow a symmetrical or anti-symmetrical strain distribution pattern. That is, opposite sets of peripheral sensing cores (such as cores 2 and 4) are in tensile and compressive states respectively, with theoretical strain amplitudes equal but opposite signs.

[0052] When a multi-core optical fiber is bent by an external static signal, the FBG center wavelength shift of each fiber core can be expressed as follows, based on the FBG sensing characteristics:

[0053]

[0054]

[0055] in, The center wavelength of the fiber optic grating. The optical fiber elasto-optic effect coefficient, The distance between the outer sensing fiber core and the central fiber core. Let be the angle between the direction of external strain and the neutral plane. The angle between the peripheral sensing fiber core i and the neutral plane. The bending radius is the radius at which external signals cause changes in the fiber core.

[0056] Taking peripheral sensing fiber core No. 2 and peripheral sensing fiber core No. 4 as examples, their ideal strain relationship can be obtained as follows:

[0057]

[0058] in, The center wavelength shift of the FBG in the peripheral sensing fiber core No. 2; The center wavelength of the fiber grating on the outermost sensing fiber core of fiber 2; The distance between the outermost sensing fiber core and the central fiber core; The angle between the No. 2 peripheral sensing fiber core and the neutral plane; The center wavelength shift of the FBG in the peripheral sensing fiber core No. 4; The center wavelength of the fiber grating on the outermost sensing fiber core is 4. The distance between the outermost sensing fiber core (No. 4) and the central fiber core; The angle between the No. 4 peripheral sensing fiber core and the neutral plane.

[0059] To eliminate interference from torsional effects during sensor installation on strain measurements, this embodiment uses cosine similarity as a misalignment criterion, defined as:

[0060]

[0061] In the formula, For the number of data points, For the No. 2 peripheral sensing fiber core in the first Strain value at each sensing point For the No. 4 peripheral sensing fiber core in the first The CS value is the negative of the strain value at each sensing point. The closer the CS value is to 1, the closer the two strain curves are to an ideal antisymmetric relationship, i.e., the smaller the misalignment. By calculating the CS value, the system can evaluate the positional deviation of the actual sensing points in real time, and combine it with a decoupling algorithm to correct the direction vector of the static signal, thereby significantly improving the identification accuracy and robustness of the static signal.

[0062] In this embodiment, the dynamic signal sensing area 7 is located at the end of the sensor housing 9 and includes the dynamic signal sensing unit 6. The dynamic signal sensing unit 6 is fabricated in situ on the end face of the multi-core optical fiber 1 using two-photon 3D printing technology, forming an FP air microcavity 13 between itself and the end faces of each fiber core of the multi-core optical fiber 1. The dynamic signal sensing unit 6 incorporates a main-auxiliary symmetrical cantilever beam with an orthogonal layout and features a hollow structure 19 to adjust the frequency response characteristics.

[0063] The principle of dynamic signal sensing is as follows: when there is a dynamic signal in the outside world, the cantilever beam produces a small displacement, which causes the cavity length of the FP air microcavity 13 to be modulated. The intensity of reflected light interference changes with the cavity length. By demodulating the light intensity fluctuations transmitted back by each fiber core, the high-frequency vibration or acceleration signal can be captured in real time.

[0064] like Figures 3 to 5 As shown, the dynamic signal sensing unit 6 is cylindrical in shape, with an outer diameter equal to that of the fiber cladding 11 of the multi-core optical fiber 1. The dynamic signal sensing unit 6 is directly fabricated in situ on the end face of the multi-core optical fiber 1 using two-photon polymerization 3D printing technology, forming FP air microcavities 13 between each fiber core end face. Based on the FP cavity interference sensing principle, when an external dynamic load triggers structural vibration, the cavity length of the FP air microcavity 13 is modulated, causing fluctuations in the interference light intensity. Dynamic signals are sensed by demodulating these intensity changes.

[0065] The dynamic signal sensing area 7 consists of four symmetrically distributed vibration signal sensing units, namely main-auxiliary symmetrical cantilever beams, and a central cylindrical support 12. Each set of main-auxiliary symmetrical cantilever beams includes mutually coupled main cantilever beams and auxiliary cantilever beams. The main-auxiliary symmetrical cantilever beams modulate the cavity length of the FP air microcavity 13 at the corresponding fiber core end face through coordinated vibration in different directions. Specifically, the four sets of main cantilever beams and the outer fiber core of the multi-core optical fiber form the FP air microcavity 13; the auxiliary cantilever beams adjust the cavity length of the FP air microcavity 13 by driving the main cantilever beams.

[0066] The main cantilever beam adopts a T-shaped structure, consisting of a first elastic cantilever beam 15 and an end mass block 16. One end of the first elastic cantilever beam 15 is fixedly connected to the central cylindrical support column 12 via two-photon 3D printing, and the other end of the first elastic cantilever beam 15 is connected to the end mass block 16.

[0067] The first elastic cantilever beam 15 is provided with a hollow structure 19, which reduces its equivalent stiffness to improve the response sensitivity to weak vibrations.

[0068] The end mass block 16 is precisely positioned directly above the corresponding fiber core along its axis, and its cross-sectional area covers the effective light-transmitting area of ​​the fiber core.

[0069] Under the action of the dynamic signal in the vertical direction (Z-axis), the end mass block 16 drives the first elastic cantilever beam 15 to vibrate up and down through inertia, modulating the cavity length of the FP air microcavity 13.

[0070] The auxiliary cantilever beam adopts a Π-shaped structure, consisting of a second elastic cantilever beam 17 and an auxiliary mass block 18. One end of the second elastic cantilever beam 17 is fixed to the end mass block 16, and the other end of the second elastic cantilever beam 17 is connected to the auxiliary mass block 18. Under the action of a dynamic signal in the horizontal direction (X-axis / Y-axis), the auxiliary mass block 18 vibrates in the horizontal plane. Due to the asymmetric constraint of its Π-shaped structure, the horizontal displacement of the auxiliary mass block 18 will generate alternating inertial force and torque at the end of the main cantilever beam, which will then be converted into the vertical displacement of the end mass block 16.

[0071] It is understandable that the first elastic cantilever beam 15 and the second elastic cantilever beam 17 are vertically distributed. Ideally, the first elastic cantilever beam 15 will only vibrate up and down under the action of the Z-axis signal to adjust the cavity length of the FP air microcavity 13. The second elastic cantilever beam 17 mainly vibrates left and right under the action of the horizontal X / Y direction signal, thereby driving the first elastic cantilever beam 15 to vibrate up and down to adjust the cavity length of the FP air microcavity 13.

[0072] The principle of triaxial vibration sensing is as follows: Z-axis vibration causes the four main cantilever beams to generate vertical displacement synchronously; X-axis / Y-axis horizontal vibration causes the auxiliary cantilever beam of the Π-shaped structure to swing, generating torque through asymmetric constraints and converting it into the vertical displacement of the corresponding main cantilever beam; by comprehensively demodulating the interference signal intensity of the four orthogonally distributed main-auxiliary symmetrical cantilever beams, the triaxial acceleration components are extracted.

[0073] To enhance the contrast of optical signal interference, a gold reflective layer is deposited on the lower surface of the main cantilever beam. The lower surface of the main cantilever beam is the side facing the fiber core.

[0074] To eliminate temperature cross-interference, a sealed temperature-sensitive cavity 14 is printed at the central core of the multi-core optical fiber, which is encapsulated with a thermosensitive liquid. When temperature changes cause changes in the refractive index and volume of the thermosensitive liquid, the influence of ambient temperature fluctuations on the dynamic interference signal is independently isolated and compensated by monitoring the change in interference reflection intensity at the central core, thus achieving independent monitoring and real-time decoupling of the temperature signal.

[0075] Four sets of main-auxiliary symmetrical cantilever beams are spatially arranged in a cross shape. Two sets of main-auxiliary symmetrical cantilever beams located on the same axial line are responsible for sensing horizontal signals in the same dimension. When there is Z-axis vibration, the main cantilever beams of the four sets of main-auxiliary symmetrical cantilever beams vibrate synchronously along the Z-axis, and the Z-axis signal is extracted by comprehensively demodulating the four interference signals. When an X-axis signal is applied, the auxiliary cantilever beams of the main-auxiliary symmetrical cantilever beams on the same axial line swing along the X-axis, causing the corresponding main cantilever beams to vibrate. The X-axis component is demodulated from the interference signal of the corresponding fiber core. Similarly, the vertical unit of the current axial direction is responsible for acquiring the Y-axis signal.

[0076] Under the influence of external triaxial vibration signals, the system motion equation of the dynamic signal sensing unit can be expressed as:

[0077]

[0078] In the formula, , These refer to the masses of the main cantilever beam and the auxiliary cantilever beam, respectively. These are the stiffness coefficients of the main cantilever beam, the auxiliary cantilever beam, and the beam when both vibrate together. These are the damping coefficients for the main cantilever beam, the auxiliary cantilever beam, and the combined vibration of both. These represent the magnitudes of the external forces acting on the sensors. These represent the displacements of the main cantilever beam, the auxiliary cantilever beam, and the combined displacements of both beams.

[0079] Further calculations reveal that the system characteristic frequency of the dynamic signal sensing unit is:

[0080]

[0081]

[0082]

[0083] In the formula, A represents the degree of mutual coupling between the main cantilever beam and the auxiliary cantilever beam, B represents the damping when the main cantilever beam, the auxiliary cantilever beam, and both vibrate together, and i is the imaginary part.

[0084] Therefore, it can be seen that the sensor's natural vibration frequency is related to the system stiffness. Proportional to; and to the mass of the cantilever beam System damping Inversely proportional.

[0085] According to the principle of fiber optic interference, when the reflected beam and the refracted beam satisfy certain phase conditions, they will interfere with each other. The interference intensity of the reflected beam can be expressed as:

[0086]

[0087] In the formula, For the intensity of reflected light, The incident light intensity; and These are the reflectivities of the two reflecting surfaces, respectively. The length of the optical microcavity formed by the two reflecting surfaces; λ is the wavelength of light in a vacuum; ρ is the refractive index of light in air.

[0088] When the incident light intensity and the reflectivity of the reflecting surface remain constant, the reflected light intensity of the FP air microcavity is mainly affected by the change in cavity length. When an external vibration signal causes the main cantilever beam to vibrate, resulting in a change in the cavity length of the FP air microcavity, the interference spectrum also changes accordingly. By further demodulating the interference spectrum, the change in the cavity length of the FP air microcavity can be determined, thereby achieving effective acquisition and detection of external vibration signals.

[0089] Example 2

[0090] like Figure 6 As shown, this embodiment provides a monitoring system for a multi-parameter integrated acquisition fiber optic sensor, including: a pulse light generator, an optical circulator, a fan-in / fan-out device, a multi-parameter integrated acquisition fiber optic sensor, an optical splitter, a high-speed demodulator, a photodetector, a signal acquisition device, and a main control unit;

[0091] The output of the pulsed light generator is connected to the first port of the optical circulator. The second port of the optical circulator is connected to the multi-parameter integrated acquisition fiber optic sensor through a fan-in / fan-out device. The third port of the optical circulator is connected to the input of the optical splitter.

[0092] During system operation, the main controller sends control commands to the pulsed light generator, causing it to emit narrowband pulsed light with a center wavelength in the C-band. This pulsed light passes through an optical circulator and fan-in / fan-out devices before entering the multi-parameter integrated fiber optic sensor. When external dynamic or static signals are present, the grating sensing area of ​​the multi-parameter integrated fiber optic sensor experiences a center wavelength drift, and the cavity length of the FP air microcavity in the dynamic signal sensing unit changes, resulting in wavelength shift and intensity modulation signals in the reflection spectrum, respectively. The reflected light is split into two paths by an optical splitter: the first path enters a high-speed demodulator to capture the real-time shift of the fiber optic grating's center wavelength; the main controller performs logical calculations based on the acquired wavelength information to monitor static signals of the external environment (such as strain and temperature); the second path undergoes photoelectric conversion via a photodetector, converting it into an electrical signal and transmitting it to an oscilloscope or data acquisition card for display and recording. The main controller preprocesses the acquired signals using preset denoising and self-decoupling algorithms to extract the changing characteristics of external dynamic signals (such as triaxial vibration and acceleration).

[0093] Those skilled in the art will recognize that the units and algorithm steps described in conjunction with the embodiments herein can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0094] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A multi-parameter integrated acquisition fiber optic sensor, characterized in that, include: A sensor housing, a sensor base, and a sensing cavity formed by the sensor housing and the sensor base; The sensing cavity is divided into a static signal sensing area and a dynamic signal sensing area along the axial direction. The sensing element of the static signal sensing area adopts a multi-core optical fiber, which includes a central core and peripheral sensing cores. The peripheral sensing cores are arranged in a square symmetrical arrangement with the central core as the center. Strain-sensitive material is filled between the inner wall of the sensor housing and the multi-core optical fiber. Each of the multi-core optical fiber cores is engraved with a fiber grating, and the wavelength demodulation of the static signal is achieved by the center wavelength shift of the fiber grating. The dynamic signal sensing area is equipped with a dynamic signal sensing unit. The dynamic signal sensing unit constructs FP air microcavities at the end face of each fiber core of the multi-core optical fiber. The intensity demodulation of the dynamic signal is achieved by changing the cavity length of the FP air microcavities. The dynamic signal sensing unit is fabricated in situ using two-photon polymerization 3D printing technology, and includes a central cylindrical support column and a main-auxiliary symmetrical cantilever beam structure with orthogonal distribution; the main-auxiliary symmetrical cantilever beams located on the same axial line sense vibration signals in the same direction; the main-auxiliary symmetrical cantilever beams modulate the cavity length of the corresponding fiber core end face FP air microcavity through coordinated vibration in different directions; The main-auxiliary symmetrical cantilever beam includes a main cantilever beam and an auxiliary cantilever beam. The main cantilever beam adopts a T-shaped structure, and the auxiliary cantilever beam adopts a Π-shaped structure. When there is vertical vibration, all the main-auxiliary symmetrical cantilever beams vibrate synchronously in the vertical direction. When there is horizontal vibration, the auxiliary cantilever beams of the main-auxiliary symmetrical cantilever beams on the same axial line swing horizontally and drive the corresponding main cantilever beams to vibrate. The main cantilever beam includes a first elastic cantilever beam and an end mass block. The first elastic cantilever beam has a hollow structure. One end of the first elastic cantilever beam is connected to the central cylindrical support, and the other end of the first elastic cantilever beam is connected to the end mass block. The auxiliary cantilever beam includes a second elastic cantilever beam and an auxiliary mass block. One end of the second elastic cantilever beam is connected to the end mass block, and the other end of the second elastic cantilever beam is connected to the auxiliary mass block. Under the action of a dynamic signal in the horizontal direction, the auxiliary mass block vibrates in the horizontal plane. The horizontal displacement of the auxiliary mass block generates alternating inertial force and torque at the end of the main cantilever beam, which is then converted into the vertical displacement of the end mass block.

2. The multi-parameter integrated acquisition fiber optic sensor as described in claim 1, characterized in that, The end mass block is located directly above the corresponding optical fiber, and the cross-sectional area of ​​the end mass block covers the effective light-transmitting area of ​​the fiber core; under the action of a vertical dynamic signal, the end mass block drives the elastic cantilever beam to vibrate up and down, modulating the cavity length of the FP air microcavity.

3. The multi-parameter integrated acquisition fiber optic sensor as described in claim 1, characterized in that, Also includes: A temperature-sensitive sealed cavity is disposed at the end face of the central fiber core. The temperature-sensitive sealed cavity is filled with a thermosensitive liquid. When the refractive index and volume of the thermosensitive liquid change, the temperature signal is independently monitored and decoupled in real time through the change in the reflection intensity of the central fiber core.

4. A monitoring system based on a multi-parameter integrated acquisition fiber optic sensor according to any one of claims 1-3, characterized in that, include: Pulse light generator, optical circulator, fan-in and fan-out devices, multi-parameter integrated acquisition fiber optic sensor, optical splitter, high-speed demodulator, photodetector, signal acquisition equipment and main control computer; The output of the pulsed light generator is connected to the first port of the optical circulator, the second port of the optical circulator is connected to the multi-parameter integrated acquisition fiber optic sensor through the fan-in and fan-out device, and the third port of the optical circulator is connected to the input of the optical splitter. When external dynamic and / or static signals act on the multi-parameter integrated acquisition fiber optic sensor, the optical splitter is used to split the reflected light returned by the multi-parameter integrated acquisition fiber optic sensor into two paths. One path enters the high-speed demodulator, which captures the offset of the center wavelength of the fiber optic grating in real time. The other path enters the photodetector for photoelectric conversion, and the converted electrical signal is recorded by the signal acquisition device. The main control unit is used to calculate the offset of the center wavelength of the fiber optic grating captured by the high-speed demodulator, so as to monitor the external static signals; it is also used to decouple the electrical signals recorded by the signal acquisition device and extract the changes of the external dynamic signals.

5. The monitoring system of a multi-parameter integrated acquisition fiber optic sensor as described in claim 4, characterized in that, The main control unit is used to perform correlation analysis on the strain data of the relative fiber core using the cosine similarity algorithm, to identify and calibrate the misalignment of the sensing point position generated during the installation of the multi-core optical fiber based on the correlation analysis results, and to eliminate the interference of torsional effect on static load measurement through the vector decoupling algorithm.

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