Linear array scanning bridge settlement monitoring sensor and monitoring method

Abstract

The invention relates to the technical field of bridge settlement detection, and particularly discloses a linear array scanning bridge settlement monitoring sensor and a monitoring method, and a carried light path system, a linear laser scanning structure and an FBG linear grating array form a sensing core with complementary advantages. The linear laser scanning structure guides laser to carry out large-range linear array or area array scanning on the surface of the bridge pier, continuous and dense macroscopic displacement data of a key area of the bridge pier can be obtained in a non-contact mode, the defect that a traditional single-point sensor is insufficient in coverage range is overcome, and full-section dynamic analysis of settlement distribution is achieved. And the FBG linear grating array is distributed along the critical path or region of the bridge pier to accurately sense the local microscopic strain and temperature change of the structure, so that the problem that the traditional bridge settlement detection method is difficult to comprehensively reflect the overall settlement form and uneven settlement distribution of the critical region is solved.

Description

Technical Field

[0001] The present application relates to the technical field of bridge settlement detection, and specifically discloses a linear array scanning bridge settlement monitoring sensor and a monitoring method. Background Art

[0002] Bridge settlement monitoring is crucial for ensuring bridge structural safety and maintaining normal operational functionality. Long-term, continuous observation of the vertical displacement of key load-bearing components, such as piers and abutments, effectively assesses the stability of bridge structures, identifies potential safety hazards, and provides a basis for decision-making regarding bridge maintenance and reinforcement. This is crucial for preventing catastrophic accidents and ensuring smooth transportation networks.

[0003] However, achieving real-time, accurate, and automated monitoring of the settlement of large bridges, especially those in complex environments, remains challenging. Existing monitoring technologies primarily include traditional geodetic methods such as precision leveling, total station trigonometric height measurement, point sensor-based measurements such as GPS / GNSS receivers, static levels, fiber Bragg grating sensors, and displacement sensors, as well as non-contact measurement technologies such as laser displacement sensors, photogrammetry, and terrestrial 3D laser scanning.

[0004] While the aforementioned methods enable automated, high-frequency data collection, and some sensors can achieve high measurement accuracy using static levels, they only capture settlement information at discrete points in space, making it difficult to fully reflect the overall settlement pattern and uneven settlement distribution in key areas, such as entire piers or abutment foundations.

[0005] The present invention provides a linear array scanning bridge settlement monitoring sensor and a monitoring method to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem that traditional bridge settlement detection methods are difficult to fully reflect the overall settlement morphology and uneven settlement distribution of key areas.

[0007] In order to achieve the above-mentioned purpose, the basic scheme of the present invention provides a linear array scanning bridge settlement monitoring sensor, including a linear laser scanning structure, an FBG linear grating array and a housing. The linear laser scanning structure is integrated with several optical components, and the several optical components and the FBG linear grating array structure form an optical path system for scanning the bridge through the linear array.

[0008] Furthermore, the optical path system includes the following structure: A beam splitter 1 integrated in the linear laser scanning structure is used to receive laser light and split it into two optical paths, and a single-mode optical fiber is connected between the beam splitter 1 and the light source; A dual fiber Bragg grating sensor subsystem comprising an FBG linear grating array is used to connect one of the optical paths. The fiber Bragg grating sensor subsystem includes a second beam splitter, multiple linear array optical fibers, a wavelength division multiplexer, a circulator, a PIN photodiode, and an FPGA field programmable gate array demodulation unit, which are sequentially connected to the optical paths. Each of the multiple linear array optical fibers is provided with an FBG grating array. A Mach-Zehnder interferometry subsystem and a photodetector integrated into a linear laser scanning structure. The Mach-Zehnder interferometry subsystem is used to connect one of the optical paths and further divide it into a reference beam and a measurement beam. The Mach-Zehnder interferometry subsystem includes a reference arm for receiving and returning the reference beam, a sensor arm for receiving the measurement beam directed toward and reflected from the bridge target surface, and an asymmetric MZ interferometer module for receiving light returned from the sensor arm and light returned from the reference arm and causing interference between the two. The photodetector is connected to the asymmetric MZ interference module and the FPGA field programmable gate array demodulation unit, and is used to receive the interfered optical signal and output the phase change information caused by the bridge displacement to the FPGA field programmable gate array demodulation unit for high-precision phase demodulation.

[0009] Furthermore, an electro-optical phase modulator is integrated in the reference arm for active phase compensation.

[0010] Furthermore, the reference arm includes a reference optical fiber, a delay optical fiber and a Faraday rotation mirror that are connected in sequence.

[0011] Furthermore, the sensing arm includes a sensing optical fiber, an optical collimator and a MEMS galvanometer that are connected in sequence.

[0012] The basic solution of the present invention further provides a linear array scanning bridge settlement monitoring method according to the linear array scanning bridge settlement monitoring sensor described above, comprising the following steps: Step A1: The high-coherence laser light emitted by the laser source is received by the beam splitter 1 and split into two optical paths, which are respectively fed into the fiber Bragg grating sensing subsystem and the Mach-Zehnder interferometry subsystem; Step A2: The optical path entering the Mach-Zehnder interferometry subsystem is split into a measurement beam and a reference beam. The measurement beam enters the sensor arm and is guided to the MEMS galvanometer. The measurement beam is controlled according to a preset path to perform high-speed point-by-point scanning of the bridge surface. The MEMS galvanometer receives the portion of light reflected back when the measurement beam hits a scanning point on the bridge surface. The reference beam enters the reference arm and then returns. Step A3: The asymmetric MZ interferometer module receives the light returned from the sensing arm and the light returned from the reference arm and causes interference between the two, thereby generating a phase change proportional to the displacement; Step A4: The photodetector receives the interfered optical signal and outputs the phase change information caused by the bridge displacement to the FPGA demodulation unit for high-precision phase demodulation. Step A5: The dual FBG sensing module accurately measures the local strain of the bridge structure and performs self-compensation for temperature effects, accurately extracts the net wavelength shift caused by the structural strain, and calculates the strain data.

[0013] Furthermore, in step A3, active phase compensation can be performed based on the electro-optical phase modulator to eliminate common-mode phase noise caused by environmental vibration and atmospheric disturbance. The specific process of active phase compensation is as follows: Active closed-loop feedback control to adjust the phase of the reference beam in real time To dynamically compensate for ambient vibrations and atmospheric disturbances The common-mode phase noise caused by is expressed as follows: .

[0014] Furthermore, in step A4, dual-wavelength differential interference technology is also used, and the dual-wavelength differential interference technology extracts purer displacement information by comparing the phase difference generated by two lasers with different wavelengths.

[0015] Furthermore, the dual-wavelength differential interference technique uses two different wavelengths: and The high coherence laser is used to extract the displacement signal through the following steps: Ambient noise common mode rejection : ; Where, The wavelength is The phase effect of the laser, The wavelength is The phase effect of the laser; Displacement signal calculation: phase change caused by displacement Wavelength difference Inversely proportional, = - The bridge displacement can be obtained by the following formula: : ; Where, and are two different wavelength values of high coherence laser.

[0016] The principle and effect of this solution are: The optical path system, linear laser scanning structure, and FBG linear grating array carried by the present invention form a sensing core with complementary advantages. The linear laser scanning structure uses a high-speed galvanometer to guide the laser to perform a large-scale linear or planar array scan on the surface of the bridge pier. It can obtain continuous and dense macro-displacement data of the key areas of the bridge pier in a non-contact manner, overcoming the shortcomings of the insufficient coverage of traditional single-point sensors and realizing a "full-section" dynamic analysis of the settlement distribution. The FBG linear grating array is distributed along the key paths or areas of the bridge pier, accurately sensing the local microscopic strain and temperature changes of the structure, solving the problem that traditional bridge settlement detection methods are difficult to fully reflect the overall settlement morphology and uneven settlement distribution in key areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram of a linear array scanning bridge settlement monitoring sensor proposed in an embodiment of the present application is shown; Figure 2 A schematic diagram of an optical path system of a linear array scanning bridge settlement monitoring sensor proposed in an embodiment of the present application is shown; Figure 3 A flow chart of a linear array scanning bridge settlement monitoring method proposed in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0019] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0020] The figure marks in the drawings of the specification include: light source 1, single-mode optical fiber 2, beam splitter 3, FBG grating array 4, linear array optical fiber 5, wavelength division multiplexer 6, circulator 7, photodiode 8, reference optical fiber 9, delay optical fiber 10, Faraday rotator 11, optical collimator 12, MEMS galvanometer 13, sensing optical fiber 14, photodetector 15, FPGA field programmable gate array demodulation unit 16, housing 17, linear laser scanning structure 18, FBG linear grating array 19, and bridge pier 20.

[0021] A linear array scanning bridge settlement monitoring sensor, for example Figure 1 and Figure 2 As shown: It includes a linear laser scanning structure 18, an FBG linear grating array 19 and a housing 17. Several optical components are integrated in the linear laser scanning structure 18. The several optical components and the FBG linear grating array 19 structure form an optical path system for scanning a bridge through a linear array.

[0022] The housing 17 provides a stable and well-protected operating environment for the optical components of the linear laser scanning structure 18 and the demodulation interface of the FBG linear grating array 19. It has dustproof, waterproof, and corrosion-resistant properties and is made of high-strength, lightweight materials to adapt to the complex and changeable outdoor environment of the bridge monitoring site.

[0023] The optical path system includes the following structure: The beam splitter 3- integrated in the linear laser scanning structure 18 is used to receive the laser light and split it into two optical paths. The beam splitter 3- is connected to the light source 1 via a single-mode optical fiber 2; A dual fiber Bragg grating sensor subsystem comprising an FBG linear grating array 19 is used to connect one of the optical paths. The fiber Bragg grating sensor subsystem includes a beam splitter 32, multiple linear array optical fibers 5, a wavelength division multiplexer 6, a circulator 7, a PIN photodiode 8, and an FPGA field programmable gate array demodulation unit 16, which are sequentially connected to the optical paths. Each of the multiple linear array optical fibers 5 is provided with an FBG grating array 4. A Mach-Zehnder interferometry subsystem and a photodetector 15 integrated into a linear laser scanning structure 18, wherein the Mach-Zehnder interferometry subsystem is used to connect one of the optical paths and further divide it into a reference beam and a measurement beam. The Mach-Zehnder interferometry subsystem is provided with a reference arm for receiving and returning the reference beam, a sensor arm for receiving the measurement beam directed toward and returned from the bridge target surface, and an asymmetric MZ interferometer module for receiving light returned from the sensor arm and light returned from the reference arm and causing interference between the two. The photodetector 15 is connected to the asymmetric MZ interference module and the FPGA field programmable gate array demodulation unit 16, and is used to receive the interfered optical signal and output the phase change information caused by the bridge displacement to the FPGA field programmable gate array demodulation unit 16 for high-precision phase demodulation.

[0024] like Figure 1 As shown, the reference arm includes a reference fiber 9, a delay fiber 10, and a Faraday rotator 11, which are connected in sequence. The reference fiber 9 receives the reference beam and the Faraday rotator 11 returns the reference beam. The reference arm also integrates an electro-optical phase modulator for active phase compensation.

[0025] The sensing arm consists of a connected sensing fiber 14, an optical collimator 12, and a MEMS galvanometer 13. The MEMS galvanometer 13, based on control signals, guides a laser beam to perform a high-speed linear scan of the bridge's target surface. The sensing light, reflected from a specific scanning point on the bridge surface, passes through the MEMS galvanometer 13 and optical collimator 12 again before returning along the sensing fiber 14.

[0026] According to the above-mentioned linear array scanning bridge settlement monitoring sensor, the present invention provides a linear array scanning bridge settlement monitoring method, comprising the following steps: Step A1: A laser source 1 emits a high-coherence laser with dual-wavelength output, which is received by a beam splitter 3 and split into two optical paths, which are respectively fed into a fiber Bragg grating sensing subsystem and a Mach-Zehnder interferometry subsystem; The laser source 1 includes two independent common single-wavelength lasers and an external fiber combiner. The external fiber combiner combines the beams of the two independent common single-wavelength lasers into a dual-wavelength output with high coherence. Furthermore, the two common single-wavelength lasers are a 1310nm DFB laser and a 1550nm DFB laser, respectively.

[0027] Step A2: The optical path entering the Mach-Zehnder interferometry subsystem is split into a measuring beam and a reference beam. The measuring beam enters the sensor arm and is guided to the MEMS galvanometer 13. The measuring beam is controlled according to a preset path to perform high-speed point-by-point scanning of the bridge surface. The MEMS galvanometer 13 receives the portion of light reflected back when the measuring beam strikes a scanning point on the bridge surface. The reference beam enters the reference arm and then returns. The MEMS galvanometer 13 is a high-speed scanning galvanometer. The MEMS galvanometer 13 precisely controls the measuring beam according to a preset path to perform high-speed point-by-point scanning of the bridge surface. When the measuring beam irradiates a certain scanning point on the bridge surface, part of the light is reflected back to the MEMS galvanometer 13 .

[0028] Step A3: The asymmetric MZ interferometer module receives the light returned from the sensing arm and the light returned from the reference arm and causes interference between the two, thereby generating a phase change proportional to the displacement; Any slight subsidence of the bridge scanning point will directly change the actual propagation path of the measurement beam, thus causing a phase change proportional to the displacement when it returns and interferes with the reference beam again. .

[0029] In this embodiment, active phase compensation can also be performed based on the electro-optical phase modulator to eliminate common-mode phase noise caused by environmental vibration and atmospheric disturbance; Specifically, the specific process of active phase compensation is as follows: Active closed-loop feedback control to adjust the phase of the reference beam in real time To dynamically compensate for ambient vibrations and atmospheric disturbances The common-mode phase noise caused by is expressed as follows: .

[0030] Step A4: The photodetector 15 receives the interfered optical signal and outputs the phase change information caused by the bridge displacement to the FPGA demodulation unit 16 for high-precision phase demodulation; Specifically, the interference light signal I converted by the photodetector 15 can be expressed as: ; Where, is the average light intensity, and V is the visibility of the interference fringes.

[0031] ; Where n is the refractive index of air, λ is the laser wavelength, Indicates the displacement of the bridge caused by slight settlement.

[0032] Furthermore, in this embodiment, in order to eliminate the influence of environmental factors such as fluctuations in the refractive index of air on the measurement accuracy, it is also equipped with dual-wavelength differential interference technology. By comparing the phase difference produced by two lasers of different wavelengths, purer displacement information is extracted to achieve nanometer-level resolution measurement of the displacement of each point on the scanning path.

[0033] Dual-wavelength differential interferometry technology: Using two different wavelengths ( : 1310nm and : 1550nm) high coherence laser and extract the displacement signal through the following steps: Ambient noise common mode rejection: The effect of environmental noise on the phase of two wavelength values ( and ) is highly correlated, where environmental noise includes fluctuations in the air refractive index and temperature drift. Common-mode noise can be eliminated by calculating the differential phase: ; Displacement signal calculation: phase change caused by displacement Wavelength difference Inversely proportional, = - The bridge displacement can be obtained by the following formula: : ; Where, and are two different wavelength values of high coherence laser, =1310nm, =1550nm.

[0034] Closed-loop feedback control: The reference arm phase is adjusted in real time through an electro-optical phase modulator to lock the asymmetric MZ interferometer module at the orthogonal operating point (highest sensitivity), further suppressing residual noise.

[0035] Step A5: Accurately measure the local strain of the bridge structure using the dual FBG sensing module ( ) and self-compensate for temperature effects, accurately extract the net wavelength shift caused by structural strain, and calculate strain data at the με level. The dual FBG sensing module is composed of two asymmetric optical fibers engraved with FBG gratings.

[0036] Light from source 1 enters a distributed FBG sensing network along the bridge structure. This network consists of a measurement FBG (FBG1) tightly coupled to the deforming region of the bridge structure and a reference FBG (FBG2) strategically placed in an adjacent strain-free or strain-isolated region.

[0037] Reflection center wavelength shift of a single FBG Responding to strain and temperature changes : ; Where, and are the strain and temperature sensitivity coefficients, respectively.

[0038] The central wavelength changes of FBG1 and FBG2 are monitored in real time by an external high-precision fiber Bragg grating interrogator. and , and apply the dual grating temperature self-compensation algorithm. If the two gratings have similar temperature response characteristics: ; Then the difference in their wavelength shifts can effectively eliminate the common temperature effect: .

[0039] This allows for precise extraction of the net wavelength shift caused by structural strain, calculating strain data at the με level. The precise temperature change information sensed by the FBG system can also be used as feedback to further optimize the displacement measurement accuracy of the asymmetric MZ interferometer module. Through a built-in high-performance data processing unit and a fusion algorithm, the high-density, high-precision displacement data along the bridge's critical path, acquired by the linear scanning asymmetric MZ interferometer module, is dynamically correlated and analyzed with the precise strain and temperature data acquired by the distributed FBG network.

[0040] This collaborative measurement of dual physical quantities not only enables cross-verification of data, improving the overall reliability and accuracy of monitoring results, effectively discerning true structural deformation from environmental interference, but also enables the construction of a comprehensive assessment model for bridge structural health. The system outputs real-time, high-precision, full-section monitoring data on the settlement and deformation of key bridge sections, providing critical technical support for safety early warning, condition assessment, and maintenance decision-making for large-scale infrastructure.

[0041] In summary, in this embodiment, after the optical path is connected and enters the fiber Bragg grating sensing subsystem, the FBG grating array 4 reflects the signal light of a specific wavelength according to the strain and temperature changes at a specific position of the bridge structure. After the reflected multi-path FBG signal light is collected, it passes through the wavelength division multiplexer 6 for combining or selecting signal lights of different wavelengths, and then passes through the circulator 7 to guide the PIN photodiode 8 for photoelectric conversion to output an electrical signal.

[0042] The electrical signal output by the PIN photodiode 8 is sent to the FPGA field programmable gate array demodulation unit 16 for high-speed real-time calculation. By analyzing the center wavelength offset of each FBG reflection spectrum, in this embodiment, the FPGA field programmable gate array demodulation unit 16 is equipped with a dual-grating temperature self-compensation algorithm. Through the dual-grating temperature self-compensation algorithm, the strain information and temperature information of each monitoring point on the bridge structure are accurately extracted.

[0043] In the Mach-Zehnder interferometry subsystem, light returning from the sensing arm interferes with light returning from the reference arm at the core of the asymmetric Mach-Zehnder interferometer module. The resulting interference signal is directed to a photodetector 15 for photoelectric conversion. The output from the photodetector 15, containing information about phase changes caused by bridge displacement, is fed into an FPGA (Field Programmable Gate Array) demodulation unit 16 for high-precision phase demodulation.

[0044] By analyzing the phase changes of the optical signal after interference and combining it with active phase compensation technology to eliminate the influence of environmental noise, the system can accurately calculate the tiny displacement of each scanning point of the bridge. The FPGA field programmable gate array demodulation unit 16 synchronously processes and fuses the displacement data from the Mach-Zehnder interferometry subsystem and the strain and temperature data from the fiber Bragg grating sensing subsystem. The temperature information obtained from the fiber Bragg grating sensing subsystem can be used to further correct the measurement accuracy of the asymmetric MZ interferometer module. Through the fusion algorithm, the system can ultimately output high-precision, high-temporal and high-spatial resolution settlement displacement field and strain distribution maps of the bridge structure, providing comprehensive data support for health monitoring and safety assessment of bridge settlement.

[0045] In this embodiment, through the optical path system, the linear laser scanning structure 18 and the FBG linear grating array 19 form a sensing core with complementary advantages. The linear laser scanning structure 18 uses the MEMS galvanometer 13 to guide the laser to perform a large-scale linear or planar scan of the surface of the pier 20. This enables non-contact acquisition of continuous and dense macroscopic displacement data from key areas of the pier 20. This overcomes the limited coverage of traditional single-point sensors, enabling "full-section" dynamic analysis of settlement distribution with submillimeter resolution. The FBG linear grating array 19 is distributed along key paths or areas of the pier 20 to accurately sense local microscopic strain and temperature changes.

[0046] The application of the dual-grating temperature self-compensation algorithm enables the FBG module to effectively remove the influence of temperature on its own strain measurement, and to feed back accurate temperature information to the linear laser scanning structure 18 to further improve the accuracy of displacement measurement.

[0047] This structural design, which deeply integrates and collaborates the linear laser scanning structure 18 with the FBG linear grating array 19, significantly improves the monitoring dimension and data quality. Through a fusion algorithm, the system can accurately correlate and analyze the high-density displacement field data obtained by laser scanning with the distributed strain field data obtained by the FBG array. This collaborative measurement and dynamic feedback mechanism of dual physical quantities (displacement and strain) not only enables cross-verification of monitoring data, thereby improving the overall reliability and accuracy of the assessment of the settlement status of the bridge pier 20, but also more effectively distinguishes between the actual structural deformation and the apparent changes caused by environmental factors (such as temperature effects and vibration interference).

[0048] The sensor structure boasts a high degree of integration and automation, supporting remote control and real-time data transmission. Both the linear laser scanning structure and the FBG linear grating array 19 enable automated data acquisition and processing, significantly reducing the need and cost of manual on-site work and increasing monitoring frequency and response speed.

[0049] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A linear array scanning bridge settlement monitoring sensor, characterized in that: The invention comprises a linear laser scanning structure, an FBG linear grating array and a shell. The linear laser scanning structure is integrated with a plurality of optical components. The plurality of optical components and the FBG linear grating array structure form an optical path system for scanning a bridge through a linear array.

2. The linear array scanning bridge settlement monitoring sensor according to claim 1, characterized in that: The optical path system includes the following structure: A beam splitter 1 integrated in the linear laser scanning structure is used to receive laser light and split it into two optical paths, and a single-mode optical fiber is connected between the beam splitter 1 and the light source; A dual fiber Bragg grating sensor subsystem comprising an FBG linear grating array is used to connect one of the optical paths. The fiber Bragg grating sensor subsystem includes a second beam splitter, multiple linear array optical fibers, a wavelength division multiplexer, a circulator, a PIN photodiode, and an FPGA field programmable gate array demodulation unit, which are sequentially connected to the optical paths. Each of the multiple linear array optical fibers is provided with an FBG grating array. A Mach-Zehnder interferometry subsystem and a photodetector integrated into a linear laser scanning structure. The Mach-Zehnder interferometry subsystem is used to connect one of the optical paths and further divide it into a reference beam and a measurement beam. The Mach-Zehnder interferometry subsystem includes a reference arm for receiving and returning the reference beam, a sensor arm for receiving the measurement beam directed toward and reflected from the bridge target surface, and an asymmetric MZ interferometer module for receiving light returned from the sensor arm and light returned from the reference arm and causing interference between the two. The photodetector is connected to the asymmetric MZ interference module and the FPGA field programmable gate array demodulation unit, and is used to receive the interfered optical signal and output the phase change information caused by the bridge displacement to the FPGA field programmable gate array demodulation unit for high-precision phase demodulation.

3. The linear array scanning bridge settlement monitoring sensor according to claim 2, characterized in that: An electro-optical phase modulator is integrated in the reference arm for active phase compensation.

4. A linear array scanning bridge settlement monitoring sensor according to claim 2 or 3, characterized in that: The reference arm includes a reference optical fiber, a delay optical fiber and a Faraday rotation mirror which are connected in sequence.

5. The linear array scanning bridge settlement monitoring sensor according to claim 2, characterized in that: The sensing arm comprises a sensing optical fiber, an optical collimator and a MEMS galvanometer which are connected in sequence.

6. A linear array scanning bridge settlement monitoring method using a linear array scanning bridge settlement monitoring sensor according to claim 3, characterized in that: The steps include: Step A1: A laser source emits a high-coherence laser with dual-wavelength output, which is received by a beam splitter 1 and splits into two optical paths, which are respectively fed into a fiber Bragg grating sensing subsystem and a Mach-Zehnder interferometry subsystem; Step A2: The optical path entering the Mach-Zehnder interferometry subsystem is split into a measurement beam and a reference beam. The measurement beam enters the sensor arm and is guided to the MEMS galvanometer. The measurement beam is controlled according to a preset path to perform high-speed point-by-point scanning of the bridge surface. The MEMS galvanometer receives the portion of light reflected back when the measurement beam hits a scanning point on the bridge surface. The reference beam enters the reference arm and then returns. Step A3: The asymmetric MZ interferometer module receives the light returned from the sensing arm and the light returned from the reference arm and causes interference between the two, thereby generating a phase change proportional to the displacement; Step A4: The photodetector receives the interfered optical signal and outputs the phase change information caused by the bridge displacement to the FPGA demodulation unit for high-precision phase demodulation. Step A5: The dual FBG sensing module accurately measures the local strain of the bridge structure and performs self-compensation for temperature effects, accurately extracts the net wavelength shift caused by the structural strain, and calculates the strain data.

7. The linear array scanning bridge settlement monitoring method according to claim 6, characterized in that: In step A3, active phase compensation can also be performed based on the electro-optical phase modulator to eliminate common-mode phase noise caused by environmental vibration and atmospheric disturbance. The specific process of active phase compensation is as follows: Active closed-loop feedback control to adjust the phase of the reference beam in real time To dynamically compensate for ambient vibrations and atmospheric disturbances The common-mode phase noise caused by is expressed as follows: 。 8. The linear array scanning bridge settlement monitoring method according to claim 6, characterized in that: In step A4, dual-wavelength differential interferometry technology is also used. The dual-wavelength differential interferometry technology extracts purer displacement information by comparing the phase difference generated by two lasers with different wavelengths.

9. The linear array scanning bridge settlement monitoring method according to claim 8, characterized in that: The dual-wavelength differential interferometry technique uses two different wavelengths: and The high coherence laser is used to extract the displacement signal through the following steps: Ambient noise common mode rejection : ； Where, The wavelength is The phase effect of the laser, The wavelength is The phase effect of the laser; Displacement signal calculation: phase change caused by displacement Wavelength difference Inversely proportional, = - The bridge displacement can be obtained by the following formula: : ； Where, and are two different wavelength values of high coherence laser.

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