Integrated sensor for vibration, temperature and strain monitoring and demodulation method thereof

Abstract

The invention provides an integrated sensor for vibration, temperature and strain monitoring and a demodulation method thereof, and belongs to the technical field of optical measurement. Comprising an optical fiber, the optical fiber is arranged on a measured object, and three Bragg gratings are connected in series on the optical fiber; the broadband light source emitter is connected with the optical fiber which is connected with the demodulation device. The broadband light source emitter emits light signals to irradiate the three Bragg gratings on the optical fiber, vibration, temperature and strain signals of a measured object are measured in real time, and the three Bragg gratings carry measured signal spectrums and reflect the measured signal spectrums back to the demodulation device for demodulation. The three key parameters of vibration, temperature and strain of the measured object are measured at the same time, and the actual state of the monitored object can be reflected more comprehensively compared with an existing single-parameter or multi-independent-sensor respective measurement mode. The problem of misjudgment of the health condition of the structure caused by insufficient monitoring of a single parameter is avoided, and richer and more accurate data support is provided for accurately evaluating the safety, reliability and residual life of the structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber sensors, and particularly relates to an integrated sensor for vibration, temperature and strain monitoring and a demodulation method thereof. Background Art

[0002] In actual engineering application scenarios, the physical environment faced by a structure or system is often complex and changeable, and it is difficult for the monitoring of a single physical quantity to comprehensively reflect its true state. For example, when a bridge structure bears the passing of vehicles, not only will strain changes occur, but also vibrations will accompany, and the change of environmental temperature will also affect the strain and vibration measurements; the blades of an aero-engine, during the high-speed rotation process, bear the strain caused by huge centrifugal forces, the vibrations caused by complex airflows, and the action of the high-temperature environment inside the engine; the bogie of a high-speed train has a complex operating environment and high stress intensity, and is a component with frequent failures on a high-speed train. The axle box temperature, vibration and wheel-to-rail strain are the main causes of failure.

[0003] In order to accurately and comprehensively evaluate the health status, performance, etc. of a structure or system, it is urgently necessary to simultaneously monitor multiple key physical quantities (such as vibration, temperature, strain, etc.). Initially, multiple independent optical fiber sensors were used to separately monitor different physical quantities, but this method has many problems, such as large space occupation and difficulty in ensuring data consistency. In this context, fiber Bragg grating sensors use light as the sensing signal and data transmission, and have the advantages of small size, light weight, multi-parameter measurement, anti-electromagnetic interference, etc. The fiber integrated sensor that integrates multiple sensing functions into one optical fiber structure came into being, aiming to realize the synchronous, accurate and stable monitoring of multiple related physical quantities in a compact optical fiber device through optimized design and innovative sensing mechanisms, so as to better meet the actual needs of multi-parameter monitoring in complex environments in various industries.

[0004] Limitations of the multi-sensor combination method In the prior art, a common practice is to use multiple independent optical fiber sensors to separately monitor vibration, temperature and strain, and then layout and install these sensors on the structure, and respectively obtain the data of each sensor through a data acquisition and processing system. Although this method can realize the measurement of each parameter, it has obvious deficiencies. First, the installation of multiple sensors requires a large amount of space, and it is difficult to effectively arrange them in some structural parts with limited space. For example, in the complex and compact structural space inside an aero-engine, it is very difficult to find enough space to reasonably arrange multiple independent sensors. Second, it is very difficult to ensure that the installation positions and angles of different sensors are exactly the same, which will cause certain deviations in the data obtained by each sensor in time and space, thereby affecting the accuracy of the subsequent analysis of the coupling relationship between multi-parameters and being unfavorable for accurately judging the true health status of the structure.

[0005] In many existing fiber optic sensor technologies, due to the physical characteristics of the three parameters of vibration, temperature, and strain themselves and the characteristics of the fiber optic sensing mechanism, serious cross-sensitivity phenomena will occur. For example, when a fiber Bragg grating measures strain, its wavelength change will also be affected by temperature change at the same time, and it is very difficult to simply separate the change information corresponding to the strain parameter; similarly, vibration sensors based on the interference principle will also be interfered to a certain extent by temperature and strain changes, resulting in errors in vibration measurement results. At present, for this cross-sensitivity problem, although there are some solutions such as compensating for temperature effects based on a reference grating and using complex algorithms for data decoupling, the compensation accuracy of these methods is limited, and the algorithms are too complex, resulting in poor real-time performance and high calculation costs, and cannot well meet the requirements of high-precision and real-time synchronous monitoring of multiple parameters in actual engineering. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problem that existing fiber optic sensors will have serious cross-sensitivity phenomena, resulting in errors in signal measurement, and provide an integrated sensor for vibration, temperature, and strain monitoring and its demodulation method.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides an integrated sensor for vibration, temperature, and strain monitoring, including an optical fiber, the optical fiber is arranged on the object to be measured, and three Bragg gratings are connected in series on the optical fiber, which are respectively used to measure the vibration, temperature, and strain signals of the object to be measured; a broadband light source emitter is connected to the optical fiber, and the optical fiber is connected to a demodulation device.

[0008] The demodulation device includes a first splitter, a second splitter, and a third splitter connected in sequence by the optical fiber. The first splitter is connected to the broadband light source emitter, the second splitter is connected to a first photodetector, and the third splitter is connected to a reference grating and a second photodetector.

[0009] A chirped grating is arranged between the second splitter and the third splitter, and the chirped grating is used to filter the temperature and vibration spectra.

[0010] The three Bragg gratings connected in series on the optical fiber include a first Bragg grating, a second Bragg grating, and a third Bragg grating, where: The first Bragg grating measures the temperature signal of the object to be measured, the second Bragg grating measures the vibration signal of the object to be measured, and the third Bragg grating measures the strain signal of the object to be measured.

[0011] In the second aspect, the present invention provides a demodulation method for an integrated sensor for vibration, temperature, and strain monitoring, including the following steps: The broadband light source emitter emits an optical signal, which irradiates three Bragg gratings on the optical fiber. The three Bragg gratings measure the vibration, temperature, and strain signals of the object to be measured in real time. The three Bragg gratings carry the measured signal spectra and reflect them back to the demodulation device for demodulation. The wavelength division multiplexing principle is used to divide the sensing of the three parameters of vibration, temperature, and strain signals.

[0012] The demodulation process of the demodulation device is as follows: The signal spectra carried by the three Bragg gratings are divided into two paths by the second splitter. One path is converted into voltage by the first photodetector to separate the vibration and temperature information. The other path passes through the chirped grating to filter out the temperature and vibration spectra and only retain the spectrum of the strain signal. The signal processed by the chirped grating is mixed with the reflection signal of the reference grating and transmitted to the second photodetector through the third splitter for strain demodulation.

[0013] The optical signal intensity of the optical signal emitted by the broadband light source emitter after being reflected by the three Bragg gratings of the optical fiber and entering the demodulation device is as follows:

[0014] Among them, is the optical intensity of the reflection spectra of the three Bragg gratings; is the optical intensity utilization rate; represents the wavelength of light, is the intensity reflection spectra of the three Bragg gratings.

[0015] For the optical signal entering the demodulation device, the optical signal intensity directly received by the first photodetector is as follows:

[0016] Among them, represents the envelope area of the reflection spectra of the first Bragg grating and the second Bragg grating; represents the envelope area of the reflection spectrum of the third Bragg grating.

[0017] The envelope area of the reflection spectrum of the third Bragg grating remains unchanged. Therefore, the optical signal intensity detected by the first photodetector includes the temperature and vibration information of the object to be measured. The optical signal intensity detected by the first photodetector is subjected to a fast Fourier transform to convert the optical intensity signal in the time domain into an optical intensity signal in the frequency domain, and the vibration signal in the optical intensity signal is extracted.

[0018] In the step of mixing the signal processed by the chirped grating with the reflection signal of the reference grating and transmitting it to the second photodetector through the third splitter for strain demodulation, the expression of the optical signal intensity received by the second photodetector is as follows:

[0019] Among them, represents the envelope area of the reflection spectra of the third Bragg grating and the reference grating. The optical intensity signal detected by the second photodetector only contains the strain information of the third Bragg grating.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an integrated sensor for vibration, temperature and strain monitoring, including an optical fiber. The optical fiber is disposed on the object to be measured. Three Bragg gratings are connected in series on the optical fiber and are respectively used for measuring the vibration, temperature and strain signals of the object to be measured. A broadband light source emitter is connected to the optical fiber, and the optical fiber is connected to a demodulation device. The broadband light source emitter emits an optical signal, which irradiates the three Bragg gratings on the optical fiber. The three Bragg gratings measure the vibration, temperature and strain signals of the object to be measured in real time. The three Bragg gratings carry the measured signal spectra and reflect them back to the demodulation device for demodulation. Through the three Bragg gratings, the three key parameters of vibration, temperature and strain of the object to be measured can be measured simultaneously. Compared with the prior art of measuring a single parameter or multiple independent sensors separately, the actual state of the monitored object can be more comprehensively reflected. It avoids the problem of misjudging the structural health status due to insufficient monitoring of a single parameter, and provides richer and more accurate data support for accurately evaluating the safety, reliability and remaining life of the structure. Based on the optical demodulation principle, the temperature, vibration and strain signals are demodulated using the optoelectronic conversion technology. The system integrates the wavelength division multiplexing principle, separates the acceleration, temperature and strain measurements, and distinguishes the acceleration and temperature signals through frequency division multiplexing, thereby realizing the accurate measurement of the three parameters.

[0021] Furthermore, integrating the three sensing functions into one greatly reduces the volume and occupied space of the sensor, and is particularly suitable for application scenarios with strict space requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the structural diagram of the integrated sensor of the present invention; Figure 2 is the demodulation optical path diagram of the integrated sensor system of the present invention; Figure 3 is the three-grating spectrogram of the present invention; Figure 4 is the spectrogram after filtering of the present invention; Explanation of the reference numerals in the drawings: 1, optical fiber; 11, first Bragg grating; 12, second Bragg grating; 13, third Bragg grating; 2, object to be measured; 3, first splitter; 4, second splitter; 5, third splitter; 6, broadband light source emitter; 7, first photodetector; 8, reference grating; 9, chirped grating; 10, second photodetector; 14, demodulation device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In the following text, only some exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the accompanying drawings and description are to be regarded as illustrative in nature and not restrictive.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0025] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0026] In the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled", "fixed", etc. should be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or a communication connection; it may be directly connected, or indirectly connected through an intermediate medium, and may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0028] 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, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or their combinations.

[0029] It should also be understood that the terms used in the specification of the present invention are for the purpose of describing particular embodiments only and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0030] It should be further understood that the term "and / or" used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0031] Various schematic structural diagrams according to the disclosed embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, where certain details are enlarged for the purpose of clear illustration, and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art can additionally design regions / layers with different shapes, sizes, and relative positions according to actual requirements.

[0032] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0033] Embodiment 1 An integrated sensor for vibration, temperature, and strain monitoring, the system of which is composed as follows: As Figures 1 - 2 shown, an integrated sensor for vibration, temperature, and strain monitoring includes an optical fiber 1, the optical fiber 1 is disposed on the object to be measured 2, three Bragg gratings are connected in series on the optical fiber 1, the temperature signal of the object to be measured 2 is measured by the first Bragg grating 11, the vibration signal of the object to be measured 2 is measured by the second Bragg grating 12, and the strain signal of the object to be measured 2 is measured by the third Bragg grating 13; a broadband light source emitter 6 is connected to the optical fiber 1, and the optical fiber 1 is connected to a demodulation device 14.

[0034] Further, the demodulation device 14 includes a first optical splitter 3, a second optical splitter 4, and a third optical splitter 5 connected in sequence by an optical fiber 1. The first optical splitter 3 is connected to a broadband light source emitter 6, the second optical splitter 4 is connected to a first photodetector 7, and the third optical splitter 5 is connected to a reference grating 8 and a second photodetector 10; a chirped grating 9 is arranged between the second optical splitter 4 and the third optical splitter 5, and the chirped grating 9 is used to filter temperature and vibration spectra.

[0035] Embodiment 2 An integrated sensor for vibration, temperature, and strain monitoring, and its demodulation method is as follows: The broadband light source emitter 6 emits an optical signal. The optical signal is transmitted along the optical fiber 1 through the first optical splitter 3 to the first Bragg grating 11 (FBG1), the second Bragg grating 12 (FBG2), and the third Bragg grating 13 (FBG3) to measure the temperature, vibration, and strain signals of the object to be measured. The three Bragg gratings carry the sensing signal spectra and reflect them back to the mediation device 14 for demodulation. As Figure 3 shown, two reflection peaks are displayed, where the peak at a wavelength of 1540 nm is higher because the wavelengths of FBG1 and FBG2 overlap. The signal is divided into two paths by the second optical splitter 4. One path is converted into a voltage by the first photodetector 7 (PD1) to separate vibration and temperature information; the other path passes through the chirped grating 9 (CFBG) to filter out temperature and vibration spectra and only retain the spectrum of FBG3. The signal processed by the chirped grating 9 (CFBG) is mixed with the reflection signal of the reference grating 8 (FBG4) and transmitted through the third optical splitter 5 to the second photodetector 10 (PD2) for detection to demodulate the strain.

[0036] Further, the optical signal intensity of the optical signal emitted by the broadband light source emitter 6 and reflected by the three Bragg gratings (FBG) of the optical fiber 1 and entering the demodulation device 14 is as shown in the following formula (1-1): (1-1) In the formula: is the optical intensity of the reflection spectra of the three Bragg gratings (FBG) of the optical fiber 1; is the optical intensity utilization rate; represents the wavelength of light, is the intensity reflection spectra of the three Bragg gratings (FBG1, FBG2, and FBG3).

[0037] The optical signal entering the demodulation device 14 is divided into two paths after passing through the 3 dB first optical splitter 3 and the 3 dB second optical splitter 4. The optical signal intensity directly received by the first photodetector 7 (PD1) is as shown in the following formula (1-2): (1-2) In the formula: is the reference temperature The reference optical intensity value under represents the envelope area of the reflection spectra of FBG1 and FBG2; represents the envelope area of the reflection spectrum of FBG3.

[0038] The central wavelength of FBG3 is far from that of FBG1 and FBG2, and its reflection spectrum moves left and right under the action of strain without changing the envelope area of the reflection spectrum , so the optical intensity signal detected by the first photodetector 7 (PD1) only contains temperature and vibration information. Under different known temperature conditions, the optical intensity signal detected by the first photodetector 7 (PD1) is measured. Since the central wavelength of the Bragg grating changes with temperature, and this change is reflected in the optical intensity signal, the optical intensity signal is measured in real time by the first photodetector 7 (PD1), and then the measured optical intensity value is substituted into the established temperature-optical intensity relationship model, and the current temperature value is calculated by Equation (1-4).

[0039] The established temperature-optical intensity relationship model is shown in (1-3): (1-3) where represents the temperature-optical intensity sensitivity coefficient, represents the temperature at the time of the optical intensity.

[0040] Based on the temperature-optical intensity relationship model, the optical intensity is measured in real time corresponding to the temperature is: (1-4) Vibration usually causes periodic changes in the reflection spectrum of the Bragg grating, and this change is reflected in the optical intensity signal detected by the first photodetector 7 (PD1) through the second splitter 4. Spectrum analysis methods such as fast Fourier transform (FFT) are performed on the optical intensity signal detected by PD1 to convert the optical intensity signal in the time domain to the frequency domain, so as to extract the characteristic frequency components (vibration signals) in the optical intensity signal.

[0041] The other path of the second splitter 4 is filtered by the transmission spectrum of the chirped grating 9 to shield the spectrum containing temperature and vibration, and only the spectrum of FBG3 containing strain information is allowed to pass through. Its spectrogram is as Figure 4 , and is sent to the reference grating 9 (FBG4) for temperature compensation and demodulation through the 3dB third splitter 5, and then the optical signal intensity reflected back is detected by the second photodetector 10 (PD2). The optical signal intensity received by PD2 is the following formula (1-3): (1-3) In the formula: It represents the envelope area of the reflection spectra of FBG3 and FBG4. The envelope area of FBG4 is constant. Therefore, the optical intensity signal detected by the second photodetector 10 (PD2) only contains the strain information of FBG3.

[0042] Furthermore, in the present invention, the wavelength-division multiplexing principle is adopted to divide the sensing of three parameters: vibration, temperature, and strain. Specifically, through a specific wavelength-division multiplexer, according to the wavelength characteristics of the optical signals corresponding to different parameters, the composite optical signal carrying vibration, temperature, and strain information is separated into three parts: acceleration and temperature sensing, and strain sensing. Since there is a certain pattern in the wavelength distribution of the optical signal changes caused by acceleration and temperature, and the wavelength range corresponding to the optical signal of strain is different from the former two, the wavelength-division multiplexer can achieve accurate separation based on these wavelength differences.

[0043] After separating the acceleration and temperature sensing parts, the Fourier transform is used to further distinguish the acceleration signal and the temperature signal. First, the mixed time-domain signal of the acceleration and temperature sensing parts is collected and then input into the Fourier transform module. During the Fourier transform process, the time-domain signal is converted to the frequency domain for analysis. Due to different generation mechanisms, the acceleration signal and the temperature signal show different change characteristics in the time domain. After Fourier transform, this difference is reflected as different frequency distributions in the frequency domain. By identifying and analyzing the characteristics of the frequency-domain signal, according to the preset frequency range and characteristic parameters, the acceleration signal and the temperature signal can be accurately distinguished.

[0044] Finally, by combining the strain sensing signal separated by wavelength-division multiplexing and the acceleration signal and temperature signal distinguished by Fourier transform, the complete demodulation of the three parameters of vibration, temperature, and strain is achieved.

[0045] Finally, it should be noted that the above embodiments only describe the basic principles, main features, and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic features of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed claims.

[0046] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. An integrated sensor for vibration, temperature and strain monitoring, characterized in that, It includes an optical fiber (1) which is disposed on the object to be measured (2). Three Bragg gratings are connected in series on the optical fiber (1) and are respectively used for measuring the vibration, temperature and strain signals of the object to be measured (2). A broadband light source transmitter (6) is connected to the optical fiber (1), and the optical fiber (1) is connected to a demodulation device (14).

2. The integrated sensor for vibration, temperature and strain monitoring according to claim 1, wherein The demodulation device (14) includes a first optical splitter (3), a second optical splitter (4) and a third optical splitter (5) which are connected in sequence by the optical fiber (1). The first optical splitter (3) is connected to the broadband light source transmitter (6), the second optical splitter (4) is connected to a first photodetector (7), and the third optical splitter (5) is connected to a reference grating (8) and a second photodetector (10).

3. An integrated sensor for vibration, temperature and strain monitoring according to claim 1, characterized in that, A chirped grating (9) is disposed between the second optical splitter (4) and the third optical splitter (5), and the chirped grating (9) is used for filtering the temperature and vibration spectra.

4. An integrated sensor for vibration, temperature and strain monitoring according to claim 1, characterized in that, The three Bragg gratings connected in series on the optical fiber (1) include a first Bragg grating (11), a second Bragg grating (12) and a third Bragg grating (13), where: The first Bragg grating (11) measures the temperature signal of the object to be measured (2), the second Bragg grating (12) measures the vibration signal of the object to be measured (2), and the third Bragg grating (13) measures the strain signal of the object to be measured (2).

5. A demodulation method for an integrated sensor for vibration, temperature and strain monitoring according to claims 1 to 4, characterized in that, It includes the following steps: The broadband light source transmitter (6) emits an optical signal, which irradiates the three Bragg gratings on the optical fiber (1). The three Bragg gratings measure the vibration, temperature and strain signals of the object to be measured (2) in real time. The three Bragg gratings carry the measured signal spectra and reflect them back to the demodulation device (14) for demodulation. The wave division multiplexing principle is adopted to divide the sensing of the three parameters of vibration, temperature and strain signals.

6. A demodulation method for an integrated sensor for vibration, temperature and strain monitoring according to claim 5, characterized in that The demodulation process of the demodulation device (14) is as follows: The signal spectra carried by the three Bragg gratings are divided into two paths by the second optical splitter (4). One path is converted into voltage by the first photodetector (7) to separate the vibration and temperature information. The other path passes through the chirped grating (9) to filter out the temperature and vibration spectra and only retain the spectrum of the strain signal. The signal processed by the chirped grating (9) is mixed with the reflection signal of the reference grating (8) and is transmitted to the second photodetector (10) through the third optical splitter (5) for detection to demodulate the strain.

7. A demodulation method for an integrated sensor for vibration, temperature and strain monitoring according to claim 6, characterized in that, The intensity of the optical signal entering the demodulation device (14) after being reflected by the three Bragg gratings of the optical fiber (1) from the optical signal emitted by the broadband light source transmitter (6) is as follows: Among them, are the light intensities of the reflection spectra of three Bragg gratings; is the light intensity utilization rate; represents the wavelength of light, are the intensity reflection spectra of three Bragg gratings.

8. A demodulation method for an integrated sensor for vibration, temperature and strain monitoring according to claim 7, characterized in that, For the optical signal entering the demodulation device (14), the intensity of the optical signal directly received by the first photodetector (7) is as follows: Among them, represents the envelope area of the reflection spectra of the first Bragg grating (11) and the second Bragg grating (12); represents the envelope area of the reflection spectrum of the third Bragg grating (13).

9. A demodulation method for an integrated sensor for vibration, temperature and strain monitoring according to claim 8, characterized in that, The envelope area of the reflection spectrum of the third Bragg grating (13) remains unchanged. Therefore, the intensity of the optical signal detected by the first photodetector (7) includes the temperature and vibration information of the object to be measured (2). The intensity of the optical signal detected by the first photodetector (7) is subjected to a fast Fourier transform to convert the optical intensity signal in the time domain into an optical intensity signal in the frequency domain, and the vibration signal in the optical intensity signal is extracted.

10. A demodulation method for an integrated sensor for vibration, temperature and strain monitoring according to claim 5, characterized in that, In the step of mixing the signal after processing the chirped grating (9) with the reflected signal of the reference grating (8) and transmitting it through the third splitter (5) to the second photodetector (10) for detection to demodulate the strain, the expression of the optical signal intensity received by the second photodetector (10) is as follows: Among them, represents the envelope area of the reflection spectra of the third Bragg grating (13) and the reference grating (8), and the optical intensity signal detected by the second photodetector (10) only contains the strain information of the third Bragg grating (13).

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