A fiber-optic sensor, a monitoring device and a method for acoustic-vibration integrated monitoring

Abstract

The application discloses a kind of for sound vibration integrated monitoring optical fiber sensor, monitoring device and method, wherein optical fiber sensor includes: sensing skeleton, for detecting ultrasonic signal and vibration signal;The side of sensing skeleton is cylindrical surface, and the end face of both sides is formed into conical recess inward, and conical recess focuses ultrasonic signal by reflection on the side of sensing skeleton;Diaphragm is set to the side end of sensing skeleton, for converting vibration signal into sound wave;First sensing optical fiber is wound on the side of sensing skeleton, for converting ultrasonic signal into first optical signal;Second sensing optical fiber is set on diaphragm, for converting sound wave into second optical signal;Wherein, first optical signal and second optical signal are output to outside, and after signal processing, the ultrasonic signal and vibration signal detected are obtained.The application realizes the simultaneous monitoring of sound wave and vibration, and is suitable for various damage monitoring.

Description

Technical Field

[0001] This invention relates to the field of damage monitoring, and specifically to an optical fiber sensor, monitoring device, and method for integrated acoustic and vibration monitoring. Background Technology

[0002] Health monitoring of various industrial equipment and engineering structures in complex environments also faces the influence of environmental factors, noise, and characteristic frequencies, leading to diverse requirements for sensor parameters. A single type of sensor cannot meet the needs of different engineering projects or operating conditions. While traditional electrical ultrasonic sensors have wide measurement bandwidth and a large sensitivity range, their stability, durability, and anti-interference capabilities in complex environments such as electromagnetic interference and humidity are far from meeting the needs of long-term monitoring projects, and they are difficult to monitor acoustic and vibration signals simultaneously. In recent years, new technologies represented by fiber optic sensors have developed rapidly. They have strong anti-interference capabilities and can be used in harsh conditions such as high pressure and corrosion. However, current fiber optic sensors have fixed sensitivity, narrow response frequencies, limited functionality, and poor applicability, making it difficult to simultaneously meet the needs of different industrial or engineering applications. Summary of the Invention

[0003] The purpose of this invention is to provide an optical fiber sensor, monitoring device and method for integrated acoustic and vibration monitoring, which broadens the corresponding frequency range of the optical fiber sensor and realizes multifunctional integrated acoustic and vibration monitoring.

[0004] To address the aforementioned technical problems, this invention provides an optical fiber sensor for integrated acoustic and vibration monitoring, comprising:

[0005] The sensor frame is used to detect ultrasonic and vibration signals. The sides of the sensor frame are cylindrical, and the two end faces form conical depressions that reflect and focus the ultrasonic signals onto the sides of the sensor frame.

[0006] A diaphragm, located at one end of the sensing frame, is used to convert vibration signals into sound waves;

[0007] The first sensing fiber is wound around the side of the sensing frame and is used to convert the ultrasonic signal into a first optical signal.

[0008] The second sensing fiber is disposed on the diaphragm and is used to convert the sound wave into a second optical signal;

[0009] The first and second optical signals are output to the outside and, after signal processing, the detected ultrasonic and vibration signals are obtained.

[0010] According to the above scheme, the first sensing fiber is wound in an equidistant spiral shape on the side of the sensing frame.

[0011] According to the above scheme, the first sensing fiber is spirally wound around the side of the sensing frame, and the spiral pitch varies non-periodically along the axial direction of the sensing frame.

[0012] According to the above scheme, the first sensing fiber forms multiple parallel and equidistant fiber rings on the side of the sensing frame, and each fiber ring is provided with an FBG.

[0013] According to the above scheme, the middle part of the first sensing fiber and the second sensing fiber is the sensing area, and the two ends are the transmission ends. The sensing area is a large-core fiber, and the transmission ends are single-mode fibers. The large-core fiber and the multimode fiber are connected by fusion splicing. The fiber diameter of the large-core fiber is ≥50μm.

[0014] The present invention also provides an integrated acoustic and vibration damage monitoring device, comprising:

[0015] The fiber optic sensor used for integrated acoustic and vibration monitoring described above;

[0016] An excitation light source is used to output light to the first sensing fiber and the second sensing fiber.

[0017] A photodetector is used to receive a first optical signal and a second optical signal; the first optical signal and the second optical signal interfere at the input end of the photodetector, and the photodetector converts the interference light intensity into a current signal;

[0018] The signal processing module is used to convert the current signal generated by the photodetector into the detected ultrasonic and vibration signals.

[0019] The present invention also provides an integrated acoustic-vibration damage monitoring method, comprising:

[0020] S1. Convert the input current signal into the detected ultrasonic and vibration signals;

[0021] The current signal is obtained by converting the first optical signal and the second optical signal, which are acquired by the fiber optic sensor for integrated acoustic and vibration monitoring described above.

[0022] According to the above scheme, step S1 includes:

[0023] S101. Convert the current signal into a voltage signal;

[0024] S102. Convert the voltage signal from analog to digital to obtain a digital signal;

[0025] S103. Perform a Fast Fourier Transform on the digital signal to obtain the spectrum;

[0026] S104. Perform phase extraction on the spectrum to obtain the phase signal;

[0027] S105. Separate the detected ultrasonic signal and vibration signal from the phase signal.

[0028] According to the above scheme, step S105 includes: adding a sliding window to the separated ultrasonic signal and vibration signal, calculating the local spectrum within the sliding window, and obtaining the time spectrum diagram of the ultrasonic signal and vibration signal.

[0029] According to the above scheme, step S105 includes: performing sliding filtering on the separated ultrasonic signal and vibration signal.

[0030] Beneficial effects

[0031] This invention achieves ultrasonic signal monitoring by setting a specially shaped sensing frame and focusing the ultrasonic signal onto the sidewall of the sensing frame using the conical recess of the sensing frame, and then detecting the focused ultrasonic signal using a first sensing optical fiber wound around the side of the sensing frame; and by setting a diaphragm and a second sensing optical fiber at the end of the sensing frame, vibration signal monitoring is achieved. The fiber optic sensor of this invention can achieve synchronous detection of acoustic and vibration signals, has strong environmental adaptability, can meet the detection needs of different devices, and can be widely used in various damage monitoring applications. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of an embodiment of the fiber optic sensor structure of the present invention;

[0033] Figure 2 This is a schematic diagram of a sensor skeleton structure according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the structure of a damage monitoring device according to an embodiment of the present invention;

[0035] Figures 4-6 This is a schematic diagram of different winding methods of the first sensing optical fiber according to an embodiment of the present invention;

[0036] Figure 7 This is a simulation diagram of the sound-gathering structure of the sensing skeleton according to an embodiment of the present invention;

[0037] Figure 8 This is a simulation diagram of a diaphragm acoustic structure according to an embodiment of the present invention;

[0038] Figure 9 This is a schematic diagram of fiber optic sensor calibration according to an embodiment of the present invention.

[0039] In the figure: 1-sensor frame, 2-first sensing fiber, 3-diaphragm, 4-second sensing fiber, 5-conical recess. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0041] See Figure 1 , Figure 2 This embodiment discloses an optical fiber sensor for integrated acoustic and vibration monitoring, comprising:

[0042] The sensing frame 1 is used to detect ultrasonic signals and vibration signals. The side surface of the sensing frame 1 is cylindrical, and the two end surfaces form conical recesses 5 inward. The conical recesses 5 focus the ultrasonic signals onto the side surface of the sensing frame 1 through reflection. In other embodiments of the present invention, the sensing frame 1 may also adopt other shapes. The sensing frame is made of rigid material.

[0043] Diaphragm 3, disposed at one end of the sensing frame 1, is used to convert vibration signals into sound waves;

[0044] The first sensing fiber 2 is wound around the side of the sensing frame 1 and is used to convert the ultrasonic signal into the first optical signal. The first sensing fiber 2 forms a stress buffer layer by being tightly wound around the sensing frame 1, which can effectively reduce the direct damage to the fiber by external mechanical impact.

[0045] The second sensing fiber 4 (bare fiber) is disposed on the diaphragm 3 and is used to convert the sound wave into a second optical signal;

[0046] The first and second optical signals are output to the outside and, after signal processing, the detected ultrasonic and vibration signals are obtained.

[0047] In this embodiment, the fiber optic sensor also includes a housing, which is used to encapsulate and fix the fiber optic sensor.

[0048] Specifically, the shape parameters of the conical recess 5 satisfy:

[0049]

[0050] In the above formula, The diameter of the base of the cone. The height of the cone. The angle of the cone's apex;

[0051] The cylindrical surfaces should be matched with a path difference to form constructive interference, then:

[0052]

[0053] In the above formula, The height of the cylindrical surface. The resonant frequency wavelength of the target frequency sound wave;

[0054] The side of the sensing frame 1 forms a sound pressure focusing area, and the sound pressure parameters are:

[0055]

[0056] In the above formula, SPL is the sound pressure level. Sound pressure level (unit: Pa), As the reference sound pressure level, and has For example, for a -6dB focused sound field, the design of the focused sound field depth and the matching of the standing wave order should consider the relationship between the cylindrical wavelength and half the wavelength, which can be referred to by the following formula:

[0057]

[0058]

[0059]

[0060] In the above formula, F is the focal length and N is the near-field distance. The diameter of the cylinder is The width of the sound pressure focusing region. This represents the axial length of the sound pressure focusing region.

[0061] The specific design parameters of the conical depression 5 can be referenced from the COMSOL simulation design, the sound pressure parameters can be observed, and then calibrated through experiments.

[0062] See Figure 7 The working principle of the conical recess 5 of the sensing frame 1 is as follows: The conical recess 5 achieves sound field energy focusing through its unique geometric structure. When external sound waves or vibration signals transmitted from the bottom solid material enter the cylindrical surface and then enter the cavity along the axial direction of the cylindrical surface, the conical recess 5 reflects the sound wave propagation path according to the geometric reflection principle. After multiple reflections on the conical surface, the sound wave energy is concentrated in the side wall region of the cylindrical surface, forming a high-energy-density sound field focusing zone. The sound pressure level of this focusing zone can be increased by 10~20dB compared to the non-focusing area. Its position and size are determined by the apex angle of the conical recess 5. ,high The wavelength λ of the sound wave is determined by both the apex angle θ = 90° and the reflection angle α = 45°. After being reflected by the conical surface, the sound wave is directed at the side wall of the cylinder at a 45° angle. Combined with the matching condition that the circumference of the cylinder is an integer multiple of half the wavelength, a standing wave peak region with a width of approximately λ / 2 can be formed on the side wall. The high damping characteristics of the sensing frame 1 suppress mechanical resonance and extend the frequency response range, enabling the sensor to have a good response frequency in the 20–300 kHz frequency band.

[0063] Further, see Figure 4 The first sensing fiber 2 is wound in an equidistant spiral shape on the side of the sensing frame 1. The advantage of this winding method is that it can achieve a wide frequency response (20Hz-200kHz), which is suitable for acoustic emission signal detection. The phase sensitivity is improved (up to the μrad / Pa level) through the photoelastic effect.

[0064] Further, see Figure 5 The first sensing fiber 2 is spirally wound around the side of the sensing frame 1, and the spiral pitch varies non-periodically along the axis of the sensing frame. The first sensing fiber 2 can be fixed with high-rigidity adhesive (such as epoxy resin) to suppress non-contact noise interference, be highly sensitive to mechanical vibration signals, and shield air noise. This winding method supports multi-point distributed monitoring and is suitable for health assessment of large structures.

[0065] Further, see Figure 6 The first sensing fiber 2 forms multiple parallel and equidistant fiber rings on the side of the sensing frame 1, and each fiber ring is provided with an FBG; an example of this winding method is as follows.

[0066] Axial coverage: 20mm;

[0067] Fiber optic spacing ≤ 5mm (to avoid spatial aliasing, minimum resolution distance for 100kHz sound waves ≈ 5mm).

[0068] Number of fiber optic rings: 4 (20mm / 5mm spacing);

[0069] The advantage of this winding method is that it has high spatial resolution, making it suitable for locating sound sources.

[0070] Regarding the design of the winding arrangement parameters of the first sensing fiber 2, it is required to cover the sound pressure focusing area and avoid spatial aliasing, and the interaxial distance should be less than half of the wavelength corresponding to the highest frequency, so that the final fiber sensitivity matches the strain sound pressure vibration response:

[0071]

[0072] In the above formula, For sound pressure vibration response, R is the radial displacement of the first sensing fiber caused by sound pressure, and R is the radius of the cylindrical surface.

[0073] When selecting a suitable coupling adhesive for the first sensing optical fiber 2 that is fixedly wound, the curing method, environmental resistance, mechanical strength, and impact on the transmission performance of the optical fiber must be comprehensively considered. Epoxy resin adhesive can provide long-term stable mechanical fixation and vibration resistance, and its temperature resistance can reach 200℃, making it suitable for complex environments such as humid or chemically exposed scenarios.

[0074] The first sensing fiber 2, wound around the sidewall of the sensing skeleton 1, works in synergy with the acoustic pressure focusing region through two mechanisms: 1. Acoustomechanical coupling: The high acoustic pressure in the focusing region drives the cylindrical sidewall to produce micron-level periodic deformation, which is directly converted into axial strain of the fiber close to its surface. The vibration amplitude is precisely quantified through interference phase changes; 2. Acousto-optic modulation: The acoustic pressure fluctuation squeezes the fiber core through the silicone coupling layer, changing the refractive index distribution of the light wave transmission. This has a significant phase modulation effect, especially on interferometric fibers, enabling the monitoring of high-frequency acoustic emission signals of 20–300 kHz. This synergistic design of acoustic field focusing and fiber optic sensing enhances the detection limit of weak vibration signals by 1 to 2 orders of magnitude compared to traditional sensors, while simultaneously achieving synchronous monitoring of acoustic vibration signals across the entire frequency band (0~300 kHz) and the entire space (360° axial coverage).

[0075] Furthermore, the middle portion of the first sensing fiber 2 and the second sensing fiber 4 is the sensing region, and both ends are the transmission ends. The sensing region is a large-core fiber (large-core fiber may include coreless fiber, multi-core fiber, hollow fiber, photonic crystal fiber, step-index multimode fiber, etc.), and the transmission ends are single-mode fibers. The single-mode fiber and the large-core fiber are connected by fusion splicing. The diameter of the large-core fiber is ≥50μm. In this embodiment, both the first sensing fiber 2 and the second sensing fiber 4 are silica fibers, which have the characteristics of corrosion resistance, electromagnetic interference resistance, and high temperature resistance (up to 800°C), making them suitable for harsh environments such as chemical and nuclear power plants.

[0076] The sensing principle of the first sensing fiber 2 is as follows: When ultrasonic waves act on the sensing frame 1, they cause periodic mechanical vibrations, resulting in axial strain and radial bending deformation of the wound first sensing fiber 2. The strain changes the refractive index of the fiber core through the elasto-optic effect. ), while the fiber length changes ( This creates an optical path difference, enabling the ultrasonic signal to modulate the optical phase.

[0077]

[0078] in, Let n be the change in optical path difference, n be the refractive index of the fiber core, and L be the fiber length. This represents the change in the refractive index of the fiber core. λ represents the change in fiber length, and λ is the wavelength of light transmission.

[0079] Helical or distributed winding can increase the contact area between the optical fiber and the ultrasonic field, enhance strain transfer efficiency, and sensitivity can be further improved by increasing the number of winding turns.

[0080] The sensing principle of the second sensing fiber 4 is as follows: When light enters the multimode fiber from the single-mode fiber, it excites multiple higher-order modes. Due to the different propagation constants of each mode, there will be a certain phase difference between the modes under the same optical path. These modes meet and superimpose during propagation, forming a multimode interference phenomenon. When the sound wave acts on the surface of the diaphragm 3, the diaphragm 3 deforms, causing micro-displacement or bending of the attached single-mode multimode fiber structure. The fiber structure utilizes the mode interference effect of the multimode fiber segment. The vibration of the diaphragm 3 caused by the sound wave will disturb the light transmission mode in the multimode fiber, ultimately forming a light intensity change related to the sound pressure at the single-mode output end. The simulation model of the diaphragm vibration with sound pressure is as follows: Figure 8 As shown.

[0081] The acoustic-structure coupling method simulates the vibration modes of the diaphragm under sound pressure using finite element analysis (FEA). The vibration state of diaphragm 3 at various frequencies is analyzed. Diaphragm 3 deforms under sound pressure, and the deformation is linearly related to the sound pressure amplitude. Different frequency sound signals cause different vibration states of diaphragm 3. By analyzing the vibration state of diaphragm 3, the signal disturbance caused by vibration to the optical fiber can be better analyzed, thus facilitating the analysis of sound signals.

[0082] See Figure 3 This embodiment also provides an integrated acoustic and vibration damage monitoring device, comprising:

[0083] The fiber optic sensor used for integrated acoustic and vibration monitoring described above;

[0084] An excitation light source is used to output light to the first sensing fiber 2 and the second sensing fiber 4.

[0085] A photodetector is used to receive a first optical signal and a second optical signal; the first optical signal and the second optical signal interfere at the input end of the photodetector, and the photodetector converts the interference light intensity into a current signal;

[0086] The signal processing module is used to convert the current signal generated by the photodetector into the detected ultrasonic and vibration signals.

[0087] The excitation light source includes a broadband ASE laser source (wavelength range 1520-1620nm) and a dual-beam splitter (splitting ratio 50:50; the dual-beam splitter can also be directly connected to the input of the photodetector via optical fiber to provide an unmodulated reference signal); the signal processing module includes a preamplifier, a multi-channel data acquisition unit, a signal analysis processor, and a display; the broadband ASE laser source outputs broadband light, which is split into two beams by the dual-beam splitter, and the two beams enter the first sensing fiber and the second sensing fiber, respectively; the first sensing fiber 2 and the second sensing fiber 4 are connected to the input of the photodetector (indium phosphate). A gallium arsenide PIN photodetector performs photoelectric conversion on the light carrying sensing information (the first and second optical signals interfere at the input of the photodetector, and the detector converts the interference light intensity signal into a current signal), and then outputs the electrical signal to a preamplifier for signal amplification. A multi-channel data acquisition unit (sampling rate ≥20MS / s in this embodiment) collects and performs analog-to-digital conversion on the electrical signals transmitted by the multi-point fiber optic sensors. The signal analysis processor performs signal processing (amplification and noise reduction) on the digital signal, determines the damage location through a positioning algorithm, and then displays the monitoring results (including time-domain waveform, spectrum, and sound source localization results) on the display.

[0088] Among them, the current signal generated by the photodetector The relationship with the light intensity signal is expressed as follows:

[0089]

[0090] Where η is the quantum efficiency of the photodetector, e is the electron charge, hv is the photon energy, ν is the light frequency, and P(t) is the instantaneous incident light power.

[0091] The preamplifier performs current-to-voltage conversion and amplifies the current signal output from the detector. In this embodiment, the preamplifier has a gain of 60dB to suppress high-frequency noise; the output voltage of the preamplifier... Represented as:

[0092]

[0093] in, For the transimpedance gain resistor, the negative sign in the formula indicates that the signal is inverted.

[0094] In this embodiment, a set of excitation light source, fiber optic sensor, photodetector, and preamplifier can be connected in series to form a single sensing channel. Multiple sensing channels can work in parallel. Data from multiple sensing channels are synchronously acquired by a multi-channel data acquisition unit and then analyzed in real time by a signal analysis processor. This enables distributed multi-point real-time monitoring and allows for real-time location of multiple damage points.

[0095] This embodiment also provides an integrated acoustic-vibration damage monitoring method, including:

[0096] S1. Convert the input current signal into the detected ultrasonic and vibration signals;

[0097] The current signal is obtained by converting the first optical signal and the second optical signal, which are acquired by the fiber optic sensor for integrated acoustic and vibration monitoring described above.

[0098] Further, step S1 includes:

[0099] S101. Convert the current signal into a voltage signal;

[0100] S102. Convert the voltage signal from analog to digital to obtain a digital signal;

[0101] S103. Perform a Fast Fourier Transform on the digital signal to obtain the spectrum;

[0102] S104. Perform phase extraction on the spectrum to obtain the phase signal;

[0103] S105. Separate the detected ultrasonic signal and vibration signal from the phase signal.

[0104] The Fast Fourier Transform (FFT) includes: converting the time-domain acoustic vibration signal into the frequency domain while satisfying the Nyquist sampling frequency, determining the dominant frequency component and noise distribution, performing a coarse analysis of the spectrum, using the Hanning window to suppress spectral leakage and improve frequency resolution, performing FFT on discrete signals, extracting amplitude and phase spectra, identifying dominant frequency peaks, and marking harmonics and noise bands.

[0105] This embodiment employs a phase demodulation algorithm (PGC algorithm) for phase extraction, demodulating the phase change caused by acoustic vibration from the interfering optical signal. Suppressing light source noise and environmental disturbances, specifically including:

[0106] 1) Introducing a high-frequency phase carrier into the interference signal ( The value can be 500kHz), and the signal form is:

[0107]

[0108] Where I(t) is the instantaneous interference light intensity, A is the DC component of the light intensity (background light intensity), which is determined by the power of the light source and the system loss, B is the amplitude of the AC component of the light intensity, which is related to the interference visibility, and C is the carrier modulation depth.

[0109] 2) Signal I(t) and and Frequency mixing, through a low-pass filter (cutoff frequency ≈ / 10) Extracting content low frequency signal and Demodulate the phase using the arctangent operation:

[0110]

[0111] 3) The least squares phase expansion algorithm is used to eliminate the 2π jump and obtain a continuous phase curve.

[0112] Since vibration is a low-frequency signal and sound is a high-frequency signal, the demodulated phase signal... The sound wave (high frequency) and vibration (low frequency) components are separated, characteristic frequencies are extracted, and bandpass filtering is added for frequency division. In step S105, for low-frequency vibration signals (0~5kHz), low-frequency signals are extracted using a Butterworth low-pass filter for analyzing mechanical vibration modes. For high-frequency sound wave signals (5~300kHz), high-pass or bandpass filters (e.g., 20–200 kHz) are used to extract and capture acoustic emission events.

[0113] Further, step S105 includes: adding a sliding window to the separated ultrasonic signal and vibration signal, calculating the local spectrum within the sliding window, and obtaining the time spectrum diagram of the ultrasonic signal and vibration signal, which can be used to locate transient events (such as the sudden high-frequency components of crack propagation).

[0114] Further, step S105 includes: performing sliding filtering on the separated ultrasonic signal and vibration signal; specifically, defining the window size M, initializing the buffer to store the current window data, initially waiting for the window to be filled with data before starting output, adding new data to the end of the window, removing old data from the beginning, summing and averaging the data in the window, and outputting the filtering result, which can effectively reduce noise.

[0115] See Figure 9 This embodiment also provides an experimental calibration method for an optical fiber sensor. In this method, a signal generator is used to generate an acoustic signal, and a frequency range of 1kHz-200kHz is selected. Different frequencies of signals are selected for calibration experiments, and the experimental data are analyzed and statistically analyzed to analyze the response spectrum of the acoustic signal at different frequencies.

[0116] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0117] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for integrated acoustic and vibration damage monitoring, characterized in that, include: S1. Convert the input current signal into the detected ultrasonic and vibration signals; The current signal is obtained by converting the first optical signal and the second optical signal, which are acquired by an optical fiber sensor used for integrated acoustic and vibration monitoring. Step S1 includes: S101. Convert the current signal into a voltage signal; S102. Convert the voltage signal from analog to digital to obtain a digital signal; S103. Perform a Fast Fourier Transform on the digital signal to obtain the spectrum; S104. Perform phase extraction on the spectrum to obtain the phase signal; S105. Separate the detected ultrasonic signal and vibration signal from the phase signal; In step S104, phase extraction employs a phase demodulation algorithm to demodulate the phase change caused by acoustic vibration from the optical signal that generates interference. Suppressing light source noise and environmental disturbances, specifically including: 1) Introducing a high-frequency phase carrier into the interference signal The signal format is: in, A represents the instantaneous interference light intensity, which is determined by the power of the light source and the system loss. B represents the amplitude of the AC component of the light intensity, which is related to the interference visibility. C represents the carrier modulation depth. 2) Signal respectively with and Frequency mixing, extracting the signal through a low-pass filter. low frequency signal and Demodulate the phase using the arctangent operation: 3) The least squares phase expansion algorithm is used to eliminate the 2π jump and obtain a continuous phase curve; Step S105 includes: adding a sliding window to the separated ultrasonic signal and vibration signal, calculating the local spectrum within the sliding window, and obtaining the time spectrum diagrams of the ultrasonic signal and vibration signal; Step S105 includes: performing sliding filtering on the separated ultrasonic signal and vibration signal; In step S105, for low-frequency vibration signals, the low-frequency signals are extracted using a Butterworth low-pass filter for analysis of mechanical vibration modes; for high-frequency ultrasonic signals, they are extracted using a high-pass or band-pass filter to capture acoustic emission events. The fiber optic sensor includes: The sensor frame is made of a rigid material and is used to detect ultrasonic and vibration signals. The sides of the sensor frame are cylindrical, and the two end faces form conical recesses that reflect and focus the ultrasonic signals onto the sides of the sensor frame. A diaphragm, located at one end of the sensing frame, is used to convert vibration signals into sound waves; The first sensing fiber is wound around the side of the sensing frame, and multiple parallel and equidistant fiber rings are formed on the side of the sensing frame. Each fiber ring is provided with an FBG. The first sensing fiber is used to convert the ultrasonic signal into a first optical signal. The second sensing fiber is disposed on the diaphragm and is used to convert the sound wave into a second optical signal; The first optical signal and the second optical signal are output to the outside and processed in step S1 to obtain the detected ultrasonic signal and vibration signal. The excitation light source outputs light to the first sensing fiber and the second sensing fiber; the photodetector receives the first optical signal and the second optical signal, and the first optical signal and the second optical signal interfere at the input end of the photodetector. The photodetector converts the interference light intensity into the current signal. The middle part of the first sensing fiber and the second sensing fiber is the sensing area, and the two ends are the transmission ends. The sensing area is a large-core fiber, and the transmission ends are single-mode fibers. The large-core fiber and the multimode fiber are connected by fusion splicing. The diameter of the large-core fiber is ≥50μm.

2. The integrated acoustic-vibration damage monitoring method according to claim 1, characterized in that, The first sensing fiber is spirally wound around the side of the sensing frame, and the pitch of the spiral wound varies non-periodically along the axis of the sensing frame.

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