Demodulation device based on optical interference principle and static and dynamic sensor

Abstract

The invention discloses a demodulation device based on an optical interference principle and a static and dynamic sensor, and relates to the technical field of sensors, a light source signal modulation unit generates a modulation light signal, the modulation light signal is introduced into an interference cavity of a sensor body through an optical fiber circulator, and reflected light subjected to interference is led out; the photoelectric detector receives reflected light after interference and converts the reflected light into an electric signal; the signal processing unit processes the electric signal to obtain a measurement parameter; the measuring range from 100mm to m can be measured, high-speed acquisition and demodulation can be realized, and large-range and high-precision measurement of the sensor can be realized; based on a sensor formed by a vibration sensing structure, synchronous high-precision measurement of two parameters of statics and vibration is realized by utilizing a cavity length mean value and a fluctuation value of an optical interference cavity, the function of measuring the two parameters by one sensor is realized, the cost of an acquisition system is greatly reduced, meanwhile, manual inspection and maintenance can be greatly reduced, and the working efficiency is improved. And good economic benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, specifically to a demodulation device and a static-dynamic sensor based on the principle of optical interference. Background Technology

[0002] Vibration sensors are widely used in industrial production and engineering monitoring. Currently, commonly used vibration sensors are mainly based on electrical principles such as piezoelectric ceramics and diffused silicon. However, sensors based on electrical principles are susceptible to electromagnetic interference, and their application scenarios are limited in places with strong electromagnetic interference such as power grids. In addition, sensors based on electrical principles also have disadvantages such as long-term zero drift and temperature drift.

[0003] In the field of sensors, fiber optic sensors offer advantages such as resistance to electromagnetic interference and long lifespan. Existing fiber optic vibration sensors are all based on the principles of fiber optic gratings (FBGs) and distributed acoustic sensing (DAS) in distributed optical fibers. The working principle involves attaching the FBG or distributed optical fiber sensor to a cantilever beam. After vibration, the cantilever beam also vibrates, generating tensile or compressive strain on its upper and lower surfaces. The magnitude of this strain can be measured using the FBG and distributed optical fibers, thus reflecting the vibration and acceleration. However, the adhesive used to bond the optical fibers ages and deforms, leading to long-term creep and zero-drift issues in the FBGs. Furthermore, FBG sensors are susceptible to temperature variations, with temperature sensitivity as high as 0.5%FS / ℃, meaning that each degree Celsius change in the resonant wavelength is equivalent to 0.5% of the measurement range, significantly reducing sensor accuracy. Moreover, each sensor can only measure static or vibration parameters individually; a single sensor cannot simultaneously measure both static and dynamic parameters.

[0004] The fiber optic sensor adopts the fiber optic Fabry-Perot interferometry principle. Existing Fabry-Perot interferometry cavity length demodulation methods include intensity methods, but the cavity length can only vary on the order of 100 nm; full-spectrum fitting methods can only vary the cavity length on the order of mm, and the sampling frequency is below kHz, resulting in insufficient dynamic performance.

[0005] In summary, existing fiber optic sensor demodulation methods suffer from slow sampling speed and low cavity length demodulation accuracy. Summary of the Invention

[0006] To address the issues of slow sampling speed and low cavity length demodulation accuracy in existing fiber optic sensor demodulation methods.

[0007] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention proposes a demodulation device based on the principle of optical interference, comprising: an optical fiber circulator, a light source signal modulation unit and a photodetector electrically connected to the optical fiber circulator, and a signal processing unit electrically connected to the photodetector; The light source signal modulation unit generates a modulated optical signal; the fiber optic circulator introduces the modulated optical signal into the interference cavity of the sensor body and extracts the reflected light after interference. The photodetector receives the reflected light after interference and converts it into an electrical signal; the signal processing unit processes the electrical signal to obtain measurement parameters.

[0008] Preferably, the light source signal modulation unit includes: a DFB laser and a signal modulation unit electrically connected to the DFB laser; The DFB laser generates an optical signal, which is then modulated by the signal modulation unit using carrier modulation or frequency modulation to generate a modulated optical signal.

[0009] Preferably, the fiber optic circulator adopts a dual-coupler or three-port circulator structure.

[0010] Preferably, the signal processing unit includes: an analog I / Q demodulation circuit, an analog-to-digital converter, and a digital signal processor; The analog I / Q demodulation circuit is used to synchronously mix the electrical signal of the photodetector with the carrier wave to obtain analog I and Q signals; The analog-to-digital converter is used to perform high-speed sampling of analog I and Q signals respectively; The digital signal processor is used to sequentially perform phase extraction, phase unwrapping, error compensation, low-pass or band-pass filtering, and range conversion to obtain measurement parameters.

[0011] Secondly, the present invention proposes a demodulation method based on the principle of optical interference, implemented using a demodulation device based on the principle of optical interference as described in any one of the above claims, comprising: A modulated optical signal is generated by a light source signal modulation unit; The modulated optical signal is introduced into the interference cavity of the sensor body through an optical fiber circulator, and the reflected light after interference is extracted. The reflected light after interference is converted into an electrical signal using a photodetector; The electrical signal is processed by a signal processing unit to obtain the measurement parameters.

[0012] Preferably, the step of processing the electrical signal through the signal processing unit to obtain the measurement parameters includes: The interferometric photoelectric signal output from the photodetector is mixed with the carrier signal in phase and quadrature, bandpass filtered, and gain / DC corrected to obtain an analog signal. The analog signals are sampled to obtain digital signals; The instantaneous phase is calculated based on the digital signal using a phase extraction algorithm. The continuous phase is calculated based on the instantaneous phase using a phase unwrapping algorithm. Based on the continuous phase, elliptic fitting or amplitude-phase calibration method is used to calculate and correct I / Q amplitude mismatch and phase error, and output the compensated phase. The compensated phase is subjected to low-pass filtering to extract the slowly varying components; the compensated phase is subjected to band-pass filtering to extract the high-frequency residuals. The real-time displacement and vibration parameters are calculated based on the slow-varying component and the high-frequency component.

[0013] Furthermore, before calculating the continuous phase using the phase unwrapping algorithm based on the instantaneous phase, the method further includes: The instantaneous phase is subjected to median filtering or adaptive noise suppression for denoising.

[0014] Furthermore, based on the instantaneous phase, a phase unwrapping algorithm is used to calculate the continuous phase, including: Based on a one-dimensional least squares phase expansion algorithm, the phase transition points of the instantaneous phase are continuously tracked; Peak detection and historical phase prediction are performed on the phase transition points to eliminate 2π transitions and output continuous phase.

[0015] Furthermore, the calculation and correction of I / Q amplitude mismatch and phase error based on the continuous phase using elliptic fitting or amplitude-phase calibration methods, and the output of the compensated phase, includes: A discrete Lissajous image is constructed using the digital signals I(n) and Q(n) in the continuous phase as coordinate points; The ellipse parameters were fitted using the least squares method. Calculate the amplitude correction coefficient and phase error compensation value based on the major / minor axis and center offset of the ellipse parameters. The amplitude correction coefficient and the phase error compensation value are applied to the continuous phase to output the compensated phase.

[0016] Furthermore, the compensated phase is low-pass filtered to extract slowly varying components; the compensated phase is band-pass filtered to extract high-frequency residuals, including... A fourth-order IIR Butterworth low-pass filter is applied to the compensated phase, with the cutoff frequency set by the displacement bandwidth, and the output is a slowly varying component. A bandpass filter with center frequency f_vib and bandwidth Δf_vib is applied to the compensated phase to extract high-frequency components.

[0017] Furthermore, the calculation of real-time displacement and vibration parameters based on the slowly varying component and the high-frequency component includes: The displacement is calculated based on the slowly varying components. Perform a fast Fourier transform on the high-frequency components, select the frequency point with the maximum amplitude to obtain the vibration frequency of the vibration parameters, and calculate the vibration amplitude based on the phase amplitude to obtain the vibration parameters.

[0018] Thirdly, the present invention proposes a static dynamic sensor, comprising: a demodulation device based on the principle of optical interference as described in any of the above, an optical fiber transmission unit connected to the demodulation device, and a vibration sensing structure; One end of the optical fiber transmission unit forms a first reflection point, and one end of the vibration sensing structure forms a second reflection point. A preset gap between the first reflection point and the second reflection point constitutes an interference cavity. The demodulation device generates an optical signal, which interferes when it passes through the interference cavity, forming reflected light after interference; the demodulation device analyzes the reflected light after interference to obtain measurement parameters.

[0019] Preferably, the vibration-sensing structure includes a support base and a planar hollow structure; The edge of the planar hollow structure is fixedly connected to the support base, and the elastic structure in the middle of the planar hollow structure remains suspended and vibrates under the action of external force. The optical fiber axis of the optical fiber transmission unit is perpendicular to the planar hollow structure, and the side of the planar hollow structure closest to the optical fiber is a mirror structure, forming a second reflection point.

[0020] Furthermore, the planar hollow structure is one of the following: cantilever beam structure, composite broken-line cantilever beam structure, porous structure, or composite simply supported beam structure.

[0021] Preferably, the optical fiber transmission unit includes a transmission optical fiber protection tube and a transmission optical fiber sleeved inside the transmission optical fiber protection tube. One end of the transmission optical fiber forms a first reflection point, and the other end of the transmission optical fiber is connected to a demodulation device.

[0022] Preferably, it further includes: a housing with a cavity structure, a tail plug and a sealing plug respectively fixed at both ends of the housing, and a probe passing through the sealing plug; The optical fiber transmission unit extends into the interior of the housing through the tail plug, the vibration sensing structure is fixed to one end of the probe, and the probe is slidably connected to the sealing plug in a sealed manner; The probe moves the vibration sensing structure, changing the distance between the first reflection point and the second reflection point, thus forming a displacement vibration sensor.

[0023] Preferably, it further includes: a first flange and a second flange fixedly connected to the first flange; The optical fiber transmission unit extends into the interior through the first flange, and the vibration sensing structure is fixed to the second flange by a connector. The distance between the first flange and the second flange is a strain sensor. When the object to be monitored deforms, the first flange and the second flange move relative to each other, causing a change in the distance between the optical fiber and the end reflector of the vibration sensing structure, thus forming a strain vibration sensor.

[0024] Preferably, it further includes: a pressure sensor housing with an opening on one side, and a diaphragm fixed to the opening of the pressure sensor housing; The optical fiber transmission unit extends into the interior through the end of the pressure sensor housing away from the opening, and the vibration sensing structure is fixed at the center of the diaphragm; When the pressure changes, the diaphragm deforms, the midpoint deflection changes, and the vibration sensing structure moves, causing the distance between the first reflection point on the fiber end face and the end mirror of the vibration sensing structure to change, thus forming a pressure vibration sensor.

[0025] Preferably, the expressions for the acceleration and the change in cavity length caused by vibration in the vibration-sensing structure are as follows:

[0026] in, The acceleration of the vibration-inducing structure, β a Sensitivity coefficient, where m is the mass of the mirror. Δd is the elastic coefficient of the vibration-inducing structure; a This represents the change in cavity length.

[0027] Fourthly, the present invention proposes a measurement method for a static dynamic sensor, implemented based on any one of the static dynamic sensors described above, comprising: When external displacement changes and vibration occurs, the vibration-sensing structure vibrates, causing the second reflection point to reciprocate. The demodulation device generates a modulated optical signal; the modulated optical signal interferes with the interference cavity between the first reflection point on the optical fiber transmission unit and the second reflection point on the vibration sensing structure, forming reflected light after interference. By analyzing the corresponding spectrum using the demodulation device, the relationship between cavity length and time is obtained, and the measurement parameters are determined.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a demodulation device and method based on the principle of optical interference. A modulated optical signal is generated by a light source signal modulation unit, and then introduced into the interference cavity of the sensor body through an optical fiber circulator. The reflected light after interference is extracted. A photodetector receives the reflected light and converts it into an electrical signal. A signal processing unit processes the electrical signal to obtain measurement parameters. High-speed hardware sampling achieves real-time acquisition at the MHz level, while ensuring high precision with a high sampling bit depth. The signal demodulation accuracy mainly relies on the phase extraction and unwrapping, I / Q elliptic error compensation, and adaptive denoising algorithm of the signal processing unit to suppress orthogonal mismatch, bias, and 2π jump errors, thereby achieving high-precision displacement / vibration demodulation over a large range of 100 mm to meters. This invention provides a device capable of measuring ranges from 100 mm to meters and enabling high-speed acquisition and demodulation (MHz level), achieving large-range, high-precision measurement of sensors. Based on this device, a series of multifunctional, high-precision, large-range sensors can be developed.

[0029] This invention provides a static-dynamic sensor and method. By employing a vibration-sensing structure based on the principle of optical interference, light waves interfere with each other when passing through an interference cavity between a first reflection point and a second reflection point on the vibration-sensing structure, forming an interference spectrum. When external displacement changes or vibrations occur, the corresponding spectrum is analyzed using a demodulation device to obtain the relationship between cavity length and time, and to measure the vibration frequency and amplitude. The vibration-sensing structure is then installed on a sensing structure for measuring displacement, strain, and pressure. Utilizing the mean and fluctuation values ​​of the optical interference cavity length, simultaneous high-precision measurement of both static and vibration parameters is achieved, enabling a single sensor to measure two parameters. This significantly reduces the cost of the acquisition system and also greatly reduces manual inspection and maintenance, resulting in good economic benefits. Furthermore, the sensor contains no easily aging adhesives or elastic bodies with large maximum principal strains; all components are in a low-stress state, effectively solving the fatigue deformation and zero-drift problems that exist in vibration-sensing structures based on fiber gratings and distributed optical fibers during long-term use. Attached Figure Description Figure 1 This is a schematic diagram of the optical interference principle in the vibration-sensing structure based on the optical interference principle in Embodiment 1 of the present invention; Figure 2 This is a diagram of the demodulation device based on the principle of optical interference provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the vibration sensing structure composed of optical fiber and hollow vibration sensing structure in Embodiment 3 of the present invention; Figure 4 This is a schematic diagram of the four hollow vibration sensing structures in Embodiment 3 of the present invention; Figure 5 This is a schematic diagram of the displacement vibration sensor structure based on the hollow vibration sensing structure in Embodiment 3 of the present invention; Figure 6 This is a three-dimensional structural diagram of the displacement vibration sensor based on the hollow vibration sensing structure in Embodiment 3 of the present invention; Figure 7 This is a schematic diagram of the strain vibration sensor structure based on the hollow vibration sensing structure in Embodiment 3 of the present invention; Figure 8 This is a three-dimensional structural diagram of the strain vibration sensor based on the hollow vibration sensing structure in Embodiment 3 of the present invention; Figure 9 This is a schematic diagram of the pressure vibration sensor structure based on the hollowed-out vibration sensing structure in Embodiment 3 of the present invention; Figure 10 This is a three-dimensional structural diagram of the pressure vibration sensor based on the hollowed-out vibration sensing structure in Embodiment 3 of the present invention; Figure 11 This is the spectrum measured by the demodulation device in Embodiment 3 of the present invention; Figure 12 This is a linear relationship graph between the change in interference cavity length measured by the vibration-sensing structure and the actual displacement in Embodiment 3 of the present invention; Figure 13 This is a graph showing the relationship between the change in interference cavity length measured by the vibration sensing module and time in Embodiment 3 of the present invention. Figure 14 This is a block diagram of the signal demodulation method based on the optical interference principle demodulation device provided in Embodiment 2 of the present invention.

[0030] In the diagram: 1 is the first reflection point; 2 is the second reflection point; 3 is the transmission optical fiber; 4 is the vibration sensing structure; 5 is the transmission optical fiber protection tube; 6 is the planar hollow structure; 7 is the outer shell; 8 is the tail plug; 9 is the probe rod; 10 is the sealing plug; 11 is the demodulation device; 12 is the support base; 13 is the strain sensor base connector; 21 is the first flange; 22 is the second flange; 23 is the diaphragm; 24 is the pressure sensor shell; 101 is the DFB laser; 102 is the signal modulation unit; 103 is the fiber optic circulator; 104 is the photodetector; 105 is the signal processing unit; 106 is the sensor body. Detailed Implementation

[0031] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0034] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0036] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0037] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0038] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0039] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0040] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0041] Example 1: This invention provides a demodulation device based on the principle of optical interference, comprising: an optical fiber circulator 103, a light source signal modulation unit and a photodetector 104 electrically connected to the optical fiber circulator 103, and a signal processing unit 105 electrically connected to the photodetector 104.

[0042] The light source signal modulation unit generates a modulated optical signal; the fiber optic circulator 103 introduces the modulated optical signal into the interference cavity of the sensor body 106 and extracts the reflected light after interference.

[0043] The photodetector 104 receives the reflected light after interference and converts it into an electrical signal; the signal processing unit 105 processes the electrical signal to obtain measurement parameters.

[0044] Specifically, such as Figure 1As shown, there are two reflection points in the interference optical path, including a first reflection point 1 and a second reflection point 2. The first reflection point 1 on the sensor has both reflection and transmission functions, meaning its reflectivity is between 0 and 1, forming partial reflection W1. The optical device constituting the first reflection point 1 has three structural forms: the first is a cleaved fiber end face, which has reflection function but is not total reflection, allowing some light to pass through and illuminate the second reflection point 2; the second is a single-mode fiber with a quarter-pitch gradient refractive index fiber fused at the end, the end face of which is also a partial reflection point; the third is a fiber collimator with a reflection point, meaning the collimator has a reflection end face on the fiber end face or lens, which is also a partial reflection point. The second reflection point 2 is a reflector with a high reflectivity, typically above 50%, forming reflected light W2. The reflected light from the two reflection points interferes, forming an interference signal, which is transmitted through fiber 3 to... Figure 2 The acquisition and demodulation system shown.

[0045] Specifically, such as Figure 2 As shown, the sensing system device for acquiring and demodulating signal 11 in this embodiment of the invention mainly includes: The light source signal modulation unit is used to generate optical signals that have been modulated by phase generation carrier or frequency modulation.

[0046] The fiber optic circulator 103 connects the light source signal modulation unit and the sensor, and is used to introduce modulated light into the sensor and extract reflected light.

[0047] The sensor body 106 includes an optical fiber transmission unit and a vibration sensing structure 4 that are optically connected to the optical fiber circulator 103. One end of the optical fiber transmission unit forms a first reflection point 1, and one end of the vibration sensing structure 4 forms a second reflection point 2. A preset gap between the first reflection point 1 and the second reflection point 2 forms an interference cavity.

[0048] The photodetector 104 is connected to the fiber optic circulator 103 and is used to receive the reflected light after interference and convert it into an electrical signal.

[0049] The signal processing unit 105 is electrically connected to the photodetector 104 and is used to perform I / Q demodulation, phase extraction, phase unwrapping and filtering separation on the electrical signal, and output displacement and vibration parameters respectively.

[0050] The light source signal modulation unit includes a DFB laser 101 (Distributed Feedback Laser) and a phase generation carrier modulation circuit electrically connected to the DFB laser 101. The DFB laser 101 continuously outputs a constant power optical signal at a center wavelength of approximately 1550 nm; it is driven by a constant current source and equipped with a temperature control unit to ensure wavelength stability.

[0051] The signal modulation unit 102 is electrically connected to the driving end of the DFB laser 101; it superimposes the phase generation carrier or high-frequency sinusoidal carrier onto the laser injection current to achieve optical frequency or phase modulation.

[0052] The fiber optic circulator 103 adopts a 3dB dual-path coupler or three-port circulator structure; one path introduces the modulated light unidirectionally into the sensor body 106, and the other path directs the interference light returned from the sensor body 106 to the photodetector 104; this design ensures unidirectional flow of the optical path and avoids power fluctuations and mode competition caused by laser back reflection.

[0053] The signal processing unit 105 includes: an analog-to-digital converter (ADC); a digital signal processor (DSP) or a field-programmable gate array (FPGA), wherein the DSP / FPGA integrates a phase unwrapping algorithm, a Lissajous error compensation algorithm, and a digital filter.

[0054] The sensor body 106, with its optical fiber end face optically connected to the circulator 103, forms a first reflection point 1 after being treated with a metal film or dielectric film; the built-in vibration sensing structure 4 and a reflector form a second reflection point 2, and the external Fabry-Perot interference cavity between the two is thus constructed; the sensor body 106 itself has a mechanical structure and Figure 3 The sensor remains consistent with the design and can withstand axial displacement and vibration. The sensor body 106 can be a displacement-based sensor or an optical rangefinder.

[0055] The photodetector 104 receives the interference light signal returned by the circulator 103 and converts it into an analog voltage signal; it is equipped with a back-illuminated InGaAs detector with a bandwidth of up to hundreds of megahertz, low noise and fast response.

[0056] The signal processing unit 105 is electrically connected to the output terminal of the photodetector 104.

[0057] The system comprises a DFB laser 101, a signal modulation unit 102, an optical fiber circulator 103, a photodetector 104, a signal processing unit 105, and a sensor body 106. These modules are sequentially connected optically or electrically via optical fibers and cables, forming a complete measurement link from the light source to the measurement output.

[0058] It should be further explained that the internal integration of the signal processing unit 105 includes: The analog I / Q demodulation circuit synchronously mixes the analog signal output by the detector with the carrier wave to obtain two low-frequency analog signals, I and Q.

[0059] An analog-to-digital converter (ADC) performs high-speed sampling of the I and Q signals respectively.

[0060] Digital signal processor (DSP / FPGA): sequentially performs phase extraction, phase unwrapping, Lissajous error compensation, low-pass / band-pass filtering, and range conversion.

[0061] The processing results (displacement, vibration frequency, and amplitude) are output to the host computer or field PLC via the onboard bus or standard industrial interface (such as RS-485, Ethernet, CAN).

[0062] In this embodiment of the invention, each module can be physically integrated into a single chassis and interconnected via standard optical fibers and cables. Through the above structure and process, the system achieves end-to-end, integrated, high-precision measurement from light source modulation, interferometric acquisition, signal demodulation to data output, making it suitable for long-term online monitoring in industrial settings.

[0063] This invention discloses an integrated demodulation device based on the principle of optical interference. The device includes a DFB laser and a carrier modulation unit, an optical fiber circulator, the aforementioned sensing head, a photodetector, and a signal processing unit. It can realize end-to-end integrated measurement from light source modulation and interference signal acquisition to I / Q demodulation, phase extraction, phase unwrapping, Lissajous error compensation and digital filtering separation, and then to real-time output of displacement and vibration parameters. It is equipped with a high-precision, real-time online signal demodulation method, which achieves synchronous, high-resolution, and high-speed measurement of the interference cavity length through steps such as simulated I / Q mixing, bandpass filtering, ADC sampling, phase unwrapping, amplitude and phase compensation, and filtering separation.

[0064] Based on this, the vibration sensing structure of this invention, based on the principle of optical interference, causes interference when light waves pass through the transmission optical fiber and through the interference cavity between the first reflection point 1 and the second reflection point 2 on the vibration sensing structure, forming an interference spectrum. When external displacement changes and vibration occurs, the corresponding spectrum is analyzed by a demodulation device to obtain the relationship between the cavity length and time, and the vibration frequency and amplitude are measured. Then, the vibration sensing structure is installed on a sensing structure for measuring displacement, strain, and pressure. By utilizing the mean and fluctuation values ​​of the cavity length of the optical interference cavity, simultaneous high-precision measurement of two parameters, statics and vibration, is achieved, realizing the function of measuring two parameters with a single sensor. The sensor does not contain glue that is prone to aging or elastic bodies with large maximum principal strain. All parts are in a low-stress state, which can effectively solve the problems of fatigue deformation and zero drift that exist in vibration sensing structures based on fiber gratings and distributed optical fibers during long-term use. The sensor of this invention can be used to measure statics and vibration in transmission towers, pipe corridors, buildings, water conservancy projects, and geological engineering. Since the interference components are non-contact, the sensor has advantages such as high linearity, high accuracy, long life, resistance to electromagnetic interference, and no zero drift. A single channel can simultaneously measure both static and dynamic parameters, significantly reducing the cost of the data acquisition system and greatly minimizing manual inspections and maintenance, resulting in excellent economic benefits.

[0065] Example 2: Based on the same inventive concept, the present invention also provides a demodulation method, including: A modulated optical signal is generated by a light source signal modulation unit; The modulated optical signal is introduced into the interference cavity of the sensor body 106 through the fiber optic circulator 103, and the reflected light after interference is extracted. The interferometric reflected light is converted into an electrical signal by the photodetector 104; The electrical signal is processed by the signal processing unit 105 to obtain the measurement parameters.

[0066] Specifically, the step of processing the electrical signal through the signal processing unit 105 to obtain the measurement parameters includes the following steps: Step M1: The interference photoelectric signal output by the photodetector (104) and the carrier signal are mixed in phase and quadrature, bandpass filtered and gain / DC corrected respectively to obtain the analog signal.

[0067] Step M2: Sample the analog signals to obtain digital signals.

[0068] Step M3: Calculate the instantaneous phase based on the digital signal using a phase extraction algorithm.

[0069] Step M4: Calculate the continuous phase based on the instantaneous phase using a phase unwrapping algorithm.

[0070] Step M5: Based on the continuous phase, use elliptic fitting or amplitude-phase calibration method to calculate and correct I / Q amplitude mismatch and phase error, and output the compensated phase.

[0071] Step M6: Perform low-pass filtering on the compensated phase to extract the slowly varying components; perform band-pass filtering on the compensated phase to extract the high-frequency residuals.

[0072] Step M7: Calculate the real-time displacement and vibration parameters based on the slow-varying component and the high-frequency component.

[0073] Further explanation is needed: in step M1, the interference photoelectric signal output by the photodetector (104) and the carrier signal are mixed in phase and quadrature, bandpass filtered and gain / DC corrected respectively to obtain the analog signal; that is, analog I / Q demodulation: the interference photoelectric signal output by the photodetector 104 and the carrier signal are mixed in phase (I) and quadrature (Q), bandpass filtered and gain / DC corrected respectively to obtain the analog I and Q signals.

[0074] It should be further explained that in step M2, the analog signals are sampled to obtain digital signals; that is, analog-to-digital conversion: the analog I and Q signals are sampled to obtain digital signals I(n) and Q(n).

[0075] It needs to be further explained that in step M3, the instantaneous phase is calculated based on the digital signal using a phase extraction algorithm; that is, phase extraction: the instantaneous phase φ_raw(n) = arctan[Q(n) / I(n)] is calculated based on I(n) and Q(n).

[0076] Further explanation is needed: in step M4, a phase unwrapping algorithm is used to calculate the continuous phase based on the instantaneous phase; that is, phase unwrapping: based on a one-dimensional least squares phase expansion algorithm, the phase transition points of the instantaneous phase are continuously tracked; peak detection and historical phase prediction are performed on the phase transition points to eliminate 2π transitions and output the continuous phase. Specifically, the phase unwrapping algorithm is applied to the instantaneous phase φ_raw(n) to eliminate 2π transitions and obtain the continuous phase φ_unwrapped(n).

[0077] Further explanation is needed: In step M5, based on the continuous phase, elliptic fitting or amplitude-phase calibration methods are used to calculate and correct I / Q amplitude mismatch and phase error, outputting the compensated phase; that is, I / Q error compensation: a discrete Lissajous image is constructed using the digital signals I(n) and Q(n) in the continuous phase as coordinate points; the ellipse parameters are fitted using the least squares method; based on the major / minor axis and center offset of the ellipse parameters, amplitude correction coefficients and phase error compensation values ​​are calculated; the amplitude correction coefficients and phase error compensation values ​​are applied to the continuous phase, outputting the compensated phase. Specifically: based on Lissajous elliptic fitting or amplitude-phase calibration methods, I / Q amplitude mismatch and phase error are calculated and corrected, outputting the compensated phase φ_corr(n).

[0078] It should be further explained that in step M6, the compensated phase is low-pass filtered to extract the slowly varying component; the compensated phase is band-pass filtered to extract the high-frequency residue; that is, component separation: φ_corr(n) is low-pass filtered to extract the slowly varying component φ_disp(n); φ_corr(n) is band-pass filtered to extract the high-frequency residue φ_vib(n).

[0079] Further explanation is needed regarding step M7, where the real-time displacement and vibration parameters are calculated based on the slowly varying component and the high-frequency component; specifically, range conversion: a 4th-order IIR Butterworth low-pass filter is applied to the compensated phase, with the cutoff frequency set by the displacement bandwidth, outputting the slowly varying component; a band-pass filter with a center frequency f_vib and bandwidth Δf_vib is applied to the compensated phase to extract the high-frequency component. Specifically, based on the slowly varying component φ_disp(n) and the high-frequency residual φ_vib(n), the real-time displacement and vibration parameters are calculated using x(n) = λ·φ_disp(n) / (4πn) and the vibration amplitude and frequency formulas, respectively.

[0080] Specifically, such as Figure 14 As shown, the signal demodulation method for an optical interferometric displacement / vibration sensing system of the present invention will be described in detail below. This method is implemented within the signal processing unit 105 (DSP / FPGA) and includes steps M1-M6.

[0081] Step M1: Analog I / Q demodulation; generation of the mixing local oscillator signal, which is synchronously provided by the carrier generator used in the signal modulation unit with a 5 kHz–100 kHz sinusoidal carrier signal; one path is directly used as LO_I, and after being amplified by low phase noise, it is input into the analog in-phase mixer; the other path is delayed by 90° and used as LO_Q, and input into the quadrature mixer.

[0082] Quadrature mixing, analog signal V output by interferometric photodetector 104 PD(t) is multiplied by LO_I and LO_Q respectively in two multipliers to obtain the baseband component: I raw (t)=V PD (t)·cos(ω LO t), Q raw (t)=V PD (t)·sin(ω LO t), where V PD (t) represents the analog voltage signal output by the photodetector, LO_I = cos(ω LO t) and LO_Q = sin(ω) LO t) represent the in-phase and quadrature local oscillator signals, respectively, and I raw (t) and Q raw (t) corresponds to the two product signals output by the analog multiplier.

[0083] The local oscillator generator outputs two mutually orthogonal reference carriers LO_I = cos(ω). LO t) and LO_Q = sin(ω) LO t), photodetector signal V PD (t) is multiplied by the two local oscillators in two analog multipliers (mixers) respectively, to obtain the two-way product I. raw (t)=V PD (t)·cos(ω LO t) and Q raw (t)=V PD (t) ·sin(ω LO t), multiplication will increase V PD (t) is the nearest ω LO The information is down-converted to baseband (while generating 2ω) LO Therefore, a low-pass filter is needed to retain the baseband components and remove the high-frequency terms to obtain orthogonal signals. The instantaneous phase can then be correctly recovered using the arctangent operation of the orthogonal signals, which is precisely cos(ω). LO t) and sin(ω LO t) and the relationship and role of the two multipliers in the system.

[0084] Bandpass filtering and DC amplitude correction, Iraw and Qraw respectively pass through the center frequency ω LO The second-order active bandpass filter suppresses baseband noise and higher-order harmonics; then, through automatic gain control (AGC) circuitry and high-precision DC bias correction circuitry, gain inconsistency and DC bias are eliminated.

[0085] Step M2: Analog-to-digital conversion; ADC sampling, using a two-channel 16-bit, 10 MS / s successive approximation ADC; I and Q signals are sampled at a sampling rate of 5MHz respectively to obtain discrete digital sequences I(n) and Q(n).

[0086] Digital preprocessing involves first performing median filtering on the I and Q sequences to suppress occasional impulse noise; then performing point linear interpolation to meet the bandwidth requirements of the DSP algorithm.

[0087] Step M3: Instantaneous phase extraction; In the DSP core, calculate the original phase φ for each sampling point. raw (n) = atan2(Q(n), I(n)), where I(n) and Q(n) are discrete sequences obtained by sampling, atan2 is the arctangent operator, and φ raw (n) represents the calculated original instantaneous phase. atan2 is used to avoid quadrant errors, and a small bias is added to the zero-value input to prevent division by zero.

[0088] Step M4: Phase unwrapping; Step M4 uses a one-dimensional least squares phase expansion algorithm, combined with historical phase prediction and peak detection, to achieve real-time online unwrapping.

[0089] One-dimensional least squares expansion, for φ raw The (n) sequence is continuously tracked for phase transition points using a one-dimensional least squares phase expansion algorithm; the phase prediction φ from the previous time step is introduced. pred (n) and slope constraints enable rapid positioning of ±2π jumps.

[0090] Peak detection assistance is added to address short-term jumps caused by non-ideal filtering in high-noise environments: if |φ raw (n)- φ unwrap If (n-1)|>π, then it is considered a jump and corrected, where φ raw (n) represents the original instantaneous phase, φ unwrap (n-1) represents the continuous phase after phase unwinding.

[0091] Step M5: I / Q error compensation; construct a discrete Lissajous image using I(n) and Q(n) as coordinate points.

[0092] The ellipse parameters were fitted using the least squares method.

[0093] Calculate the amplitude correction coefficient and phase error compensation value based on the major / minor axis and center offset of the fitted ellipse.

[0094] The Lissajous ellipse construction plots discrete points on a plane corresponding to the unwrapped phases I(n) and Q(n), forming an approximate elliptical image.

[0095] Least square fitting: In DSP or FPGA, the least squares method is used to quickly solve the general equation of an ellipse.

[0096] Amplitude / phase correction coefficients are calculated based on the fitting results, determining the major / minor axis lengths a and b, and the center offset (x0, y0); amplitude correction, k I =k ref / a,k Q =k ref / b; Phase correction, Δθ=atan2(y0 / x0), combine Δθ and k I， k Q Applied to φ unwrap (n), output corrected phase φ corr (n).

[0097] In the above expression, a and b are the major and minor semi-axes of the constructed Lissajous ellipse; (x0, y0) are the coordinates of the ellipse center offset in the orthogonal plane; k ref As a reference amplitude used to scale the ellipse proportionally to the radius of the target circle, k can generally be set... ref =1; k I and k Q The amplitude correction coefficient is used to normalize the half-axis of the orthogonal signals to the same reference radius; Δθ is the phase zero offset, which is the pointing angle from the center of the ellipse to the origin obtained by the arctangent operation of atan2(y0 / x0); φ unwrap (n) represents phase unwinding, while φ corr (n) represents the corrected phase output.

[0098] Step M6: Filtering and separation; In step M6, the cutoff frequency of the low-pass filter is set to be less than twice the target displacement bandwidth; the passband center frequency and bandwidth of the band-pass filter are preset or adaptively adjusted according to the range of vibration frequencies to be measured.

[0099] Low-pass filtering, for φ corr (n) A 4th-order IIR Butterworth low-pass filter is applied, with the cutoff frequency set by the displacement bandwidth; the output slowly varying component φ disp (n).

[0100] Bandpass filtering, while also targeting φ corr (n) Using a bandpass filter (FIR or IIR) with a center frequency f_vib and bandwidth Δf_vib, extract the high-frequency component φ. vib (n).

[0101] Obtain phase information φ vib (n) After that, according to the relationship between the sensor phase and the cavity length change d, d=2πnφ vib (n) / λ, where n is the refractive index of the interference cavity and λ is the laser operating wavelength of the sensor, thus the length of the interference cavity of the sensor can be obtained.

[0102] In the range conversion step M7, the frequency of the vibration parameter is obtained by performing a fast Fourier transform (FFT) on φ_vib(n) and selecting the frequency point with the maximum amplitude. The vibration amplitude is calculated from the phase amplitude corresponding to that frequency point.

[0103] The process includes a denoising step after step M3 and before step M4, where median filtering or adaptive noise suppression is performed on φ_raw(n) to improve the stability of phase unwrapping.

[0104] The bandpass filter bandwidth in the analog I / Q demodulation step M1 is ±10 kHz of the carrier frequency to suppress baseband noise and high-frequency interference.

[0105] Example 3 This invention provides a static dynamic sensor, comprising: a demodulation device, an optical fiber transmission unit connected to the demodulation device, and a vibration sensing structure 4.

[0106] One end of the optical fiber transmission unit forms a first reflection point 1, and one end of the vibration sensing structure 4 forms a second reflection point 2. A preset gap between the first reflection point 1 and the second reflection point 2 constitutes an interference cavity.

[0107] The demodulation device generates an optical signal, which interferes when it passes through the interference cavity, forming reflected light after interference; the demodulation device analyzes the reflected light after interference to obtain measurement parameters.

[0108] Among them, the vibration sensing structure 4 is selected from corrugated elastic elements, broken line elastic elements or spring elastic elements.

[0109] Specifically, in various embodiments of the present invention, the acceleration a of the vibration-sensing structure 4 and the change in cavity length Δd caused by the vibration are... a The relationship is as follows:

[0110] in, β v Here, m is the sensitivity coefficient, and m is the mass of mirror 14. Let be the elastic coefficient of the vibration-inducing structure 4. The amplitude can be obtained from the vibration acceleration, and thus the vibration intensity can also be obtained.

[0111] In the above embodiments, the sensitivity coefficient β v This is related to the mass and elastic modulus of the vibration-inducing structure 4. In practice, an acceleration can be given separately, and Δd can be measured. v β was obtained after calibration. v .

[0112] Specifically, in this embodiment of the invention, there is a demodulation device and an optical fiber transmission unit and a vibration sensing structure 4 arranged opposite to each other.

[0113] The demodulation device and the correspondingly arranged optical fiber transmission unit and vibration sensing structure 4; wherein, The optical fiber transmission unit is provided with an optical fiber for transmitting optical signals; the end of the optical fiber near the vibration sensing structure 4 serves as a first reflection point 1 for reflecting the optical signals. The vibration sensing structure 4 has a reflector at one end near the optical fiber transmission unit to form a second reflection point 2, which is used to reflect the optical signal from the optical fiber; A preset gap is formed between the first reflection point 1 and the second reflection point 2 to form an optical interference cavity, so that the light signal passing through the first reflection point 1 and the reflected light signal passing through the second reflection point 2 interfere with each other.

[0114] like Figure 3 As shown, the hollow structure 4 is a composite zigzag cantilever beam structure with the center point as the reflection point. The axis of the optical fiber 3 is perpendicular to and passes through the center of the hollow structure 4. The end face of the optical fiber 3 is cut flat, which is the first reflection point 1. A reflector is provided at one end of the vibration sensing structure 4 near the optical fiber transmission unit to form a second reflection point 2, which is used to reflect the light signal from the optical fiber 3. There is a preset gap between the first reflection point 1 and the second reflection point 2 to form an optical interference cavity, so that the light signal passing through the first reflection point 1 and the reflected light signal passing through the second reflection point 2 interfere.

[0115] Commonly used structures such as Figure 4 As shown, including but not limited to (a) cantilever beam structures, (b) composite polygonal cantilever beam structures, (c) porous structures, and (d) composite simply supported beam structures, the above structures can significantly reduce structural stiffness and increase vibration sensitivity. By adjusting the thickness of the hollow structure 4, Figure 4 In (a) and (b), the width of the beam and the total length of the polygonal beam are adjusted. Figure 4 In (c) and (d), the stiffness of the hollow structure is adjusted by adjusting the size and number of holes. The lower the total stiffness, the higher the sensitivity, the lower the natural frequency, and the smaller the range.

[0116] for Figure 4 The processing technology of the vibration sensing structure 4 is as follows: The vibration sensing structure 4 adopts a planar hollow structure, and the main processing technologies used to prepare this structure are CNC, picosecond, laser, and 3D printing.

[0117] like Figure 5As shown, the hollow structure 4 is fixed to the sensor element of the sensor and moves with the device under the action of external force; the edge of the hollow structure is connected and fixed to the sensor element by a ring 12, so that the elastic structure 4 in the middle does not contact the sensor element and remains suspended, allowing it to vibrate freely; the axis of the optical fiber 3 is perpendicular to the hollow structure 4 and intersects with the hollow structure 4. The side of the hollow structure 4 near the optical fiber 3 is a mirror structure, and a reflector 2 is prepared by coating technology, which serves as the second reflection point 2 of the sensor body. This coating is a high-reflection structure with a reflectivity usually higher than 20%.

[0118] The vibration sensing structure 4 is disposed inside the housing, and the optical fiber transmission unit is partially inserted through the first end of the housing. The probe 9 and the vibration sensing structure 4 can move relative to the housing. The vibration sensing structure 4 is sealed inside the housing, preventing moisture and dust from entering.

[0119] Specifically, in this embodiment of the invention, by combining a transmission structure for displacement, strain, and pressure with a vibration sensing structure 4 based on a hollow structure, a multifunctional sensor that can simultaneously measure static and dynamic parameters can be fabricated. The static parameters include mechanical parameters such as displacement, strain, and pressure.

[0120] like Figure 5 and Figure 6 As shown, the displacement vibration sensor based on the vibration sensing structure 4: the optical fiber 3 is fixed to the tail plug 8 through the protective sleeve 5, the outer ring of the vibration sensing structure 4 is fixed to the annular support base 12, and the base 12 is fixed to the displacement gauge probe 9. The probe is used to contact the object to be measured. When the object to be monitored undergoes a displacement change, the probe 9 drives the support base 12, the vibration sensing structure 4, and the reflector 2 to move, changing the distance between the two reflection points, that is, the length of the interference cavity changes. The displacement w is determined by the change in the length of the interference cavity Δd, where Δd = w.

[0121] When the object to be monitored vibrates, the center point 2 of the vibration sensing structure 4 vibrates along the axial direction, causing the length of the interference cavity to change back and forth. By the relationship between the length of the interference cavity and time, the vibration parameters (vibration frequency and amplitude) can be determined.

[0122] The demodulation device 11 is connected to the optical fiber transmission unit 3 and is used to receive the interference light signal and generate an interference spectrum. Based on the interference spectrum data, the device determines the change in the length of the interference cavity and then determines parameters such as displacement and amplitude frequency.

[0123] like Figure 7 and Figure 8As shown, in the strain vibration sensor based on the vibration sensing structure, the optical fiber 3 is fixed to the first flange 21 by the protective sleeve 5, and the vibration sensing structure 4 is fixed to the second flange 22 by the ring 12 and the connector 13. The distance between the two flanges is the gauge length L of the strain sensor. When the object to be monitored deforms, the two flanges move relative to each other, causing the distance between the optical fiber and the end reflector of the vibration sensing structure to change, that is, the interference cavity length changes by Δd, so as to determine the strain ε=Δd / L.

[0124] When the object to be monitored vibrates, the center point 2 of the vibration sensing structure 4 vibrates along the axial direction, causing the length of the interference cavity to change back and forth. By the relationship between the length of the interference cavity and time, the vibration parameters (vibration frequency and amplitude) can be determined.

[0125] The demodulation device 11 is connected to the optical fiber transmission unit 3 and is used to receive the interference light signal and generate an interference spectrum. Based on the interference spectrum data, the device determines the change in the length of the interference cavity and then determines parameters such as the strain and amplitude frequency.

[0126] like Figure 9 and Figure 10 As shown, in the pressure vibration sensor based on the vibration sensing structure, the optical fiber 3 is fixed to the center of the left side of the sensor housing 24 through the optical fiber protection tube 5. The vibration sensing structure 4 is fixed to the center point of the diaphragm 23 on one side inside the sensor through the ring 12 and the connector. The right side of the diaphragm 23 is in contact with the outside and is sealed around the perimeter. When the pressure changes, the diaphragm 23 deforms, and the deflection at the midpoint changes, causing the vibration sensing structure 4 to move. This causes the distance between the first reflection point 1 at the end face of the optical fiber and the reflector 2 at the end of the vibration sensing structure 4 to change, that is, the interference cavity length changes. The magnitude of the pressure P can be determined by the change in the interference cavity length Δd and the sensitivity k of the diaphragm 23, where P = kΔd.

[0127] When the object to be monitored vibrates, the center point 2 of the vibration sensing structure 4 vibrates along the axial direction, causing the length of the interference cavity to change back and forth. By the relationship between the length of the interference cavity and time, the vibration frequency and amplitude can be determined.

[0128] The demodulation device 11 is connected to the optical fiber transmission unit 3 and is used to receive the interference light signal and generate an interference spectrum. Based on the interference spectrum data, the device determines the change in the length of the interference cavity and then determines parameters such as pressure and amplitude frequency.

[0129] In vibration monitoring, for the vibration parameters measured by the vibration-sensing structure on the above three types of sensors, the acceleration a of the vibration-sensing structure and the change in cavity length Δd caused by the vibration are... a The series is as follows:

[0130] in, β a Sensitivity coefficient, where m is the mass of the mirror. is the elastic coefficient of the vibration-inducing structure.

[0131] Further explanation is needed. Figure 11 The spectrum diagram measured by the demodulation device in this embodiment of the invention can be obtained by demodulating the spectrum. The relationship between the cavity length and time can be obtained by calculating the frequency at different times.

[0132] For further explanation, please refer to [link / reference]. Figure 12 By measuring the relationship between the change in cavity length Δd caused by the displacement change and the actual displacement W, the relationship between the cavity length change caused by the displacement change and the displacement itself can be determined. This yields a sensitivity coefficient β1≈1, indicating a linear relationship between the change in cavity length and the actual displacement. The expression for this linear relationship is as follows: Figure 12 As shown, y = 1.00025x, where y is the change in the length of the interference cavity along the vertical axis and x is the displacement; R-Square (fit similarity) = 0.9999.

[0133] therefore, ; Where W is the actual displacement; Δd is the change in the length of the interference cavity.

[0134] Regarding the vibration frequency, Figure 13 For example, assuming the vibration period is T, the vibration frequency f remains unchanged, always being f=1 / T.

[0135] Example 4 This invention provides a measurement method for a static dynamic sensor, comprising: When external displacement changes and vibration occurs, the vibration sensing structure 4 vibrates, causing the second reflection point 2 to move back and forth.

[0136] The demodulation device generates a phase-modulated optical signal; the optical signal interferes through the interference cavity between the first reflection point 1 on the optical fiber transmission unit and the second reflection point 2 on the vibration sensing structure 4, forming reflected light after interference.

[0137] By analyzing the corresponding spectrum using demodulation device 11, the relationship between cavity length and time is obtained, and vibration parameters are measured.

[0138] This invention provides a demodulation device based on the principle of optical interference and a static-dynamic sensor based on a vibration-sensing structure, comprising: a demodulation device and a displacement vibration sensing mechanism. This invention further provides an integrated demodulation device based on the principle of optical interference, which includes a DFB laser and a carrier modulation unit, an optical fiber circulator, the aforementioned sensor, a photodetector, and a signal processing unit 105. It can achieve end-to-end integrated measurement from light source modulation and interference signal acquisition to I / Q demodulation, phase extraction, phase unwrapping, Lissajous error compensation and digital filtering separation, and finally to real-time output of displacement and vibration parameters. It is equipped with a high-precision, real-time online signal demodulation method, which achieves synchronous, high-resolution, and high-speed measurement of the interference cavity length through steps such as simulated I / Q mixing, bandpass filtering, ADC sampling, phase unwrapping, amplitude and phase compensation, and filtering separation. Based on this, a displacement vibration sensor was developed. An optical interference cavity is located between the first reflection point 1 and the second reflection point 2. The light signals from the two reflection points interfere, and the length of the interference cavity is determined by the interference signal. When measuring static parameters such as displacement, strain, and pressure, one end of the vibration-sensing structure is connected to a probe, flange, and diaphragm to measure displacement, strain, and pressure. The other end of the vibration-sensing structure is a reflector. When changes in displacement, strain, and pressure occur, the vibration-sensing structure causes the reflector to move as a whole, changing the length of the interference cavity. When external vibration occurs, the vibration-sensing structure vibrates, causing the reflector to reciprocate. A demodulation device receives the interference light signal and determines the relationship between the change in the interference cavity length and time, thereby determining the displacement, strain, pressure, and vibration parameters. This invention utilizes a structure and demodulation device based on the principle of optical interference to achieve simultaneous high-precision measurement of static and dynamic parameters, realizing the function of measuring two parameters with a single sensor.

[0139] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A demodulation device based on the principle of optical interference, characterized in that, include: Fiber optic circulator (103), light source signal modulation unit and photodetector (104) electrically connected to the fiber optic circulator (103), and signal processing unit (105) electrically connected to the photodetector (104). The light source signal modulation unit generates a modulated optical signal; the fiber optic circulator (103) introduces the modulated optical signal into the interference cavity of the sensor body (106) and extracts the reflected light after interference. The photodetector (104) receives the reflected light after interference and converts it into an electrical signal; the signal processing unit (105) processes the electrical signal to obtain measurement parameters.

2. The demodulation device based on the principle of optical interference according to claim 1, characterized in that, The light source signal modulation unit includes: a DFB laser (101) and a signal modulation unit (102) electrically connected to the DFB laser (101). The DFB laser (101) generates an optical signal, which is then modulated by the signal modulation unit (102) using carrier modulation or frequency modulation to generate a modulated optical signal.

3. The demodulation device based on the principle of optical interference according to claim 1, characterized in that, The fiber optic circulator (103) adopts a dual-path coupler or a three-port circulator structure.

4. A demodulation device based on the principle of optical interference according to claim 1, characterized in that, The signal processing unit (105) includes: an analog I / Q demodulation circuit, an analog-to-digital converter, and a digital signal processor; The analog I / Q demodulation circuit is used to synchronously mix the electrical signal of the photodetector (104) with the carrier wave to obtain analog I and Q signals; The analog-to-digital converter is used to perform high-speed sampling of analog I and Q signals respectively; The digital signal processor is used to sequentially perform phase extraction, phase unwrapping, error compensation, low-pass or band-pass filtering, and range conversion to obtain measurement parameters.

5. A demodulation method based on the principle of optical interference, characterized in that, Based on the demodulation device based on the optical interference principle as described in any one of claims 1 to 4, it includes: A modulated optical signal is generated by a light source signal modulation unit; The modulated optical signal is introduced into the interference cavity of the sensor body (106) through an optical fiber circulator (103), and the reflected light after interference is extracted. The reflected light after interference is converted into an electrical signal by a photodetector (104); The electrical signal is processed by the signal processing unit (105) to obtain the measurement parameters.

6. The method according to claim 5, characterized in that, The process of processing the electrical signal through the signal processing unit (105) to obtain the measurement parameters includes: The interferometric photoelectric signal output by the photodetector (104) and the carrier signal are mixed in phase and quadrature, bandpass filtered and gain / DC corrected respectively to obtain the analog signal; The analog signals are sampled to obtain digital signals; The instantaneous phase is calculated based on the digital signal using a phase extraction algorithm. The continuous phase is calculated based on the instantaneous phase using a phase unwrapping algorithm. Based on the continuous phase, elliptic fitting or amplitude-phase calibration method is used to calculate and correct I / Q amplitude mismatch and phase error, and output the compensated phase. The compensated phase is subjected to low-pass filtering to extract the slowly varying components; the compensated phase is subjected to band-pass filtering to extract the high-frequency residuals. The real-time displacement and vibration parameters are calculated based on the slow-varying component and the high-frequency component.

7. The method according to claim 6, characterized in that, Before calculating the continuous phase using the phase unwrapping algorithm based on the instantaneous phase, the method further includes: The instantaneous phase is subjected to median filtering or adaptive noise suppression for denoising.

8. The method according to claim 6, characterized in that, The continuous phase is calculated based on the instantaneous phase using a phase unwrapping algorithm, including: Based on a one-dimensional least squares phase expansion algorithm, the phase transition points of the instantaneous phase are continuously tracked; Peak detection and historical phase prediction are performed on the phase transition points to eliminate 2π transitions and output continuous phase.

9. The method according to claim 6, characterized in that, The method of calculating and correcting I / Q amplitude mismatch and phase error based on the continuous phase using elliptic fitting or amplitude-phase calibration, and outputting the compensated phase, includes: A discrete Lissajous image is constructed using the digital signals I(n) and Q(n) in the continuous phase as coordinate points; The ellipse parameters were fitted using the least squares method. Calculate the amplitude correction coefficient and phase error compensation value based on the major / minor axis and center offset of the ellipse parameters. The amplitude correction coefficient and the phase error compensation value are applied to the continuous phase to output the compensated phase.

10. The method according to claim 6, characterized in that, The compensated phase is low-pass filtered to extract slowly varying components; the compensated phase is band-pass filtered to extract high-frequency residuals, including... A fourth-order IIR Butterworth low-pass filter is applied to the compensated phase, with the cutoff frequency set by the displacement bandwidth, and the output is a slowly varying component. A bandpass filter with center frequency f_vib and bandwidth Δf_vib is applied to the compensated phase to extract high-frequency components.

11. The method according to claim 6, characterized in that, The calculation of real-time displacement and vibration parameters based on the slowly varying component and the high-frequency component includes: The displacement is calculated based on the slowly varying components. Perform a fast Fourier transform on the high-frequency components, select the frequency point with the maximum amplitude to obtain the vibration frequency of the vibration parameters, and calculate the vibration amplitude based on the phase amplitude to obtain the vibration parameters.

12. A static dynamic sensor, characterized in that, include: A demodulation device based on the principle of optical interference as described in any one of claims 1 to 4, an optical fiber transmission unit connected to the demodulation device and a vibration sensing structure (4). One end of the optical fiber transmission unit forms a first reflection point (1), and one end of the vibration sensing structure (4) forms a second reflection point (2). A preset gap between the first reflection point (1) and the second reflection point (2) forms an interference cavity. The demodulation device generates an optical signal, which interferes when it passes through the interference cavity, forming reflected light after interference; the demodulation device analyzes the reflected light after interference to obtain measurement parameters.

13. A static dynamic sensor according to claim 12, characterized in that, The vibration sensing structure (4) includes a support base (12) and a planar hollow structure (6). The edge of the planar hollow structure (6) is fixedly connected to the support base (12), and the elastic structure in the middle of the planar hollow structure (6) remains suspended and vibrates under the action of external force; The optical fiber axis of the optical fiber transmission unit is perpendicular to the planar hollow structure (6). The side of the planar hollow structure (6) closest to the optical fiber is a mirror structure, forming a second reflection point (2).

14. A static dynamic sensor according to claim 13, characterized in that, The planar hollow structure (6) is one of the following: cantilever beam structure, composite broken line cantilever beam structure, porous structure or composite simply supported beam structure.

15. A static dynamic sensor according to claim 12, characterized in that, The optical fiber transmission unit includes a transmission optical fiber protection tube (5) and a transmission optical fiber (3) sleeved inside the transmission optical fiber protection tube (5). One end of the transmission optical fiber (3) forms a first reflection point (1), and the other end of the transmission optical fiber (3) is connected to a demodulation device (11).

16. A static dynamic sensor according to claim 12, characterized in that, Also includes: The outer shell (7) has a cavity structure, the tail plug (8) and the sealing plug (10) are fixed at both ends of the outer shell (7) respectively, and the probe (9) passes through the sealing plug (10). The optical fiber transmission unit extends through the tail plug (8) into the interior of the outer shell (7), the vibration sensing structure (4) is fixed at one end of the probe (9), and the probe (9) is in a sealed sliding connection with the sealing plug (10); The probe (9) drives the vibration sensing structure (4) to move, changing the distance between the first reflection point (1) and the second reflection point (2) to form a displacement vibration sensor.

17. A static dynamic sensor according to claim 12, characterized in that, Also includes: First flange (21), and second flange (22) fixedly connected to the first flange (21); The optical fiber transmission unit extends into the interior through the first flange (21), and the vibration sensing structure (4) is fixed to the second flange (22) by the connector (13); The distance between the first flange (21) and the second flange (22) is the strain sensor. When the object to be monitored deforms, the first flange (21) and the second flange (22) move relative to each other, causing the distance between the optical fiber and the end reflector of the vibration sensing structure to change, thus forming a strain vibration sensor.

18. A static dynamic sensor according to claim 12, characterized in that, Also includes: A pressure sensor housing (24) with an opening on one side, and a diaphragm (23) fixed on the opening of the pressure sensor housing (24). The optical fiber transmission unit extends into the interior through the end of the pressure sensor housing (24) away from the opening, and the vibration sensing structure (4) is fixed at the center of the diaphragm (23); When the pressure changes, the diaphragm (23) deforms, the midpoint deflection changes, and the vibration sensing structure (4) moves, causing the distance between the first reflection point (1) of the fiber end face and the end reflector (2) of the vibration sensing structure (4) to change, thus forming a pressure vibration sensor.

19. A static dynamic sensor according to claim 12, characterized in that, The expressions for the acceleration and the change in cavity length caused by vibration in the vibration-sensing structure (4) are as follows: in, The acceleration of the vibration-inducing structure; β a Sensitivity coefficient; m is the mass of the mirror; Δd is the elastic coefficient of the vibration-inducing structure; a This represents the change in cavity length.

20. A measurement method for a static dynamic sensor, characterized in that, Based on a static dynamic sensor according to any one of claims 12 to 19, comprising: When the external displacement changes and vibration occurs, the vibration sensing structure (4) vibrates, causing the second reflection point (2) to move back and forth. The demodulation device (11) generates a modulated optical signal; the modulated optical signal interferes through the interference cavity between the first reflection point (1) on the optical fiber transmission unit and the second reflection point (2) on the vibration sensing structure (4) to form the reflected light after interference; The demodulation device (11) analyzes the corresponding spectrum to obtain the relationship between cavity length and time, and measures the parameters.

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