Vibration light intensity demodulation method and system based on real spectrum of double-fiber grating

Abstract

The invention provides a dynamic vibration signal light intensity demodulation method and system based on a real spectrum, and the method comprises the steps: obtaining a light intensity signal outputted by an integrated sensor, obtaining a fusion spectrum through a spectrometer, analyzing the fusion spectrum, obtaining an optical path difference, and obtaining the optical power through a demodulation algorithm based on the real spectrum; the method comprises the following steps: analyzing optical power to obtain light current, converting the light current into voltage, and gradually deducing vibration amplitude, vibration frequency and other information related to a vibration signal by using the relationship between the voltage and wavelength movement amount, thereby realizing the conversion from a light intensity signal to the vibration signal related information, and completing the measurement and demodulation of the vibration signal. The real measuring range of the double-grating cascade structure sensor can be accurately reflected, the temperature and vibration integrated signals can be demodulated, the accuracy and authenticity of the signals are improved, the measurement of the vibration signals is completed, the measurement of the temperature and vibration signals is realized, and the problem that the dynamic vibration signals are difficult to demodulate truly is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber sensing, and relates to a vibration light intensity demodulation method and system based on a dual optical fiber grating real spectrum. Background Art

[0002] Fiber optic sensing technology is a new technology that has gradually developed in the 1970s. It was born out of the need to break through the limitations of traditional sensors in some special environments. For example, in harsh environments such as strong electromagnetic interference, flammable and explosive, and limited space, traditional electronic sensors are difficult to work normally, and fiber optic sensors have gradually attracted attention due to their unique advantages. The basic principle of fiber grating is based on the interference phenomenon of light. When the light waves in the optical fiber encounter an area where the refractive index changes, part of the light waves will be reflected back to form an interference pattern. The periodic structure of the fiber grating enables it to selectively reflect certain specific wavelengths of light, and the changes in these wavelengths are closely related to external environmental factors. The fiber grating can be affected by strain and temperature at the same time. From the principle of its perception of strain, when the fiber grating is strained, the period of the fiber grating will change accordingly. This periodic change will further cause the change in the wavelength of the light reflected by the fiber grating, causing the wavelength to drift. By accurately measuring the displacement of the wavelength of the reflected light, the magnitude of the strain can be accurately calculated. As for temperature perception, due to the thermo-optical effect and thermal expansion effect of the optical fiber material itself, when the ambient temperature changes, the refractive index and grating period of the fiber Bragg grating will also change. This will also cause the wavelength of the reflected light to change. By measuring the displacement of the wavelength, the magnitude of the temperature effect can be inferred. This enables accurate perception of temperature. However, since the effects of strain and temperature on the fiber Bragg grating both cause the drift of the reflected wavelength, the action mechanisms are similar and affect each other. The temperature signal and the strain signal can be separated by demodulation, and then the demodulated signal can be measured and analyzed. In this way, the magnitude of the fiber Bragg grating affected by temperature and vibration at the same time can be accurately measured.

[0003] The existing grating demodulation algorithms are mainly based on the reflection spectrum function intensity demodulation algorithm derived from the transfer matrix method and the reflection spectrum function intensity demodulation algorithm based on the Gaussian function. The reflection spectrum function intensity demodulation algorithm based on the transfer matrix method is mainly applicable to linear optical systems and has limited processing capabilities for nonlinear optical phenomena. When dealing with high-loss materials, the transfer matrix method may introduce additional complexity, especially when considering nonlinear effects. The accuracy of the algorithm depends on the accuracy of the optical constants of the material (such as refractive index, absorption coefficient, etc.). If the material parameters are inaccurate, it may lead to deviations in the reflection spectrum results. For complex structures or multi-peak reflection spectra, the Gaussian function cannot accurately describe the reflection spectrum function intensity demodulation algorithm based on the Gaussian function, resulting in fitting errors. For reflection spectra with strong non-Gaussian characteristics, the use of Gaussian functions may lead to information loss or misunderstanding, affecting the reliability and accuracy of the results. Both algorithms have certain problems in demodulating dynamic real vibration signals and cannot meet the requirements of real-time measurement of dynamic signals. Summary of the invention

[0004] In response to the problems existing in the prior art, the present invention proposes a dynamic vibration signal light intensity demodulation algorithm based on the real spectrum, which can accurately reflect the real range of the dual grating cascade structure sensor and can demodulate the temperature and vibration integrated signals, improve the accuracy and authenticity of the signal, complete the measurement of the vibration signal, realize the measurement of temperature and vibration signals, and solve the problem that the dynamic vibration signal is difficult to be truly demodulated.

[0005] The present invention is achieved through the following technical solutions: The vibration light intensity demodulation method based on the real spectrum of dual fiber Bragg gratings includes: The integrated signal output by the dual fiber Bragg grating temperature and vibration sensor is obtained, and the integrated signal is converted into an electrical signal, and then fused to obtain a fused spectrum; wherein the integrated signal includes a sensing grating signal and a reference grating signal; The fused spectrum is analyzed to obtain the optical path difference, and the optical path difference is demodulated based on the real spectrum to obtain the actual spectral optical power; The photocurrent is calculated by the actual spectral light power, and then converted into voltage; The wavelength shift of the fiber Bragg grating is obtained by voltage, and then the relationship between the wavelength shift and the axial strain is established; Based on the relationship between the wavelength shift and the axial strain, the vibration signal of the vibration amplitude and vibration frequency is obtained.

[0006] Preferably, the integrated signal output by the temperature and vibration sensor of the dual fiber Bragg grating is obtained, the integrated signal is converted into an electrical signal, and then fused to obtain a fused spectrum. The specific process is as follows: The integrated signal output by the temperature and vibration sensor of the dual fiber Bragg grating is obtained, wherein the integrated signal includes a sensing grating signal and a reference grating signal. The reflection spectra of the sensing grating signal and the reference grating signal are measured by a spectrometer. The wavelength of the sensing grating signal is moved toward the long-wave direction by heating, and the spectra are fused. During the fusion process, the spectrum measured by the spectrometer is saved, and the light intensity of the spectrum reflected by the two sensing grating signals and the reference grating signal is measured by a photoelectric converter. The above fusion process steps are repeated until the central wavelength of the sensing grating signal moves to the preset wavelength of the reference grating signal, and the reflection spectra of the sensing grating signal and the reference grating signal overlap, and then the fused spectrum is obtained.

[0007] Preferably, the fused spectrum is analyzed to obtain the optical path difference, specifically: By analyzing the concavity of the fused spectrum curve, the central wavelengths of the reference grating and the sensor grating are obtained at the two inflection points of the fused spectrum curve, and the optical path difference is obtained through the central wavelengths of the reference grating and the sensor grating. .

[0008] Preferably, the optical path difference ; In the formula, is the central wavelength of the sensing grating, is the central wavelength of the reference grating.

[0009] Preferably, the photocurrent is obtained for the actual spectral light power, and the photocurrent is converted into a voltage, specifically: The photoelectric converter converts the actual spectral light power into P Converted to photocurrent i , photocurrent i Converted to voltage by current-to-voltage conversion circuit V ; Among them, the photocurrent i The relationship with the actual spectral optical power is:

[0010] Where: i is the photocurrent, is the quantum efficiency of the photoelectric converter, and P is the actual spectral light power.

[0011] Preferably, the wavelength shift of the fiber grating is obtained by voltage, and the specific expression is:

[0012] Where: V is the voltage, R is the equivalent resistance of the conversion circuit, A is the effective area of ​​the photoelectric converter, is the relationship between the light intensity and the shift of the fiber Bragg grating center wavelength, is the wavelength shift.

[0013] Preferably, the relationship between the wavelength shift and the axial strain is specifically:

[0014] Where: is the conversion coefficient of different optical paths, is the axial strain, The central wavelength of the vibration sensor; is the wavelength shift.

[0015] Preferably, the specific process of obtaining the vibration amplitude is: For the dynamic axial strain caused by vibration, the vibration amplitude is obtained by analyzing the changes in the axial strain at multiple moments and combining the material properties and structural parameters. The specific expression is: A=m

[0016] Where: A is the vibration amplitude, m is the coefficient related to the material structure, is the change in axial strain.

[0017] Preferably, the specific process of obtaining the vibration frequency is: The axial strain measured continuously over a period of time , fast Fourier transform FFT is used to perform spectrum analysis to obtain the vibration frequency component of the axial strain changing with time, and the vibration frequency component is the vibration frequency of the vibration signal;

[0018] Where: X(n) is the discrete time signal, N is the signal length, k=0, 1, 2,...N-1, and X(k) is the corresponding frequency domain signal.

[0019] A vibration light intensity demodulation system based on dual fiber Bragg grating real spectrum, including a fiber Bragg grating vibration sensor, a fiber Bragg grating temperature sensor, a photoelectric converter, a coupler and a spectrometer; The fiber Bragg grating vibration sensor and the fiber Bragg grating temperature sensor are placed on an optical vibration table, and one end of the coupler is connected to the fiber Bragg grating vibration sensor and the fiber Bragg grating temperature sensor; The vibration sensor and the temperature sensor are arranged in the same optical fiber in a cascade structure. The light emitted by the light source is guided to the vibration sensor through a coupler, and the reflected light signal is guided to a photoelectric converter. The photoelectric converter converts the light signal into an electrical signal and inputs it into a spectrometer for fusion. The temperature grating FBG2 of the fiber Bragg grating temperature sensor is used as a reference grating; the vibration grating FBG1 on the fiber Bragg grating vibration sensor is used as a sensing grating.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention proposes a dynamic vibration signal light intensity demodulation method and system based on real spectrum, by acquiring the light intensity signal output by the integrated sensor, obtaining the fused spectrum through the spectrometer, analyzing the fused spectrum, and obtaining the optical path difference. The optical power is obtained through the demodulation algorithm based on the real spectrum; the optical power is analyzed to obtain the photocurrent, and then the voltage change is obtained; the wavelength shift of the fiber grating is analyzed through the voltage, and then the relationship with the axial strain is established, and the vibration amplitude, vibration frequency and other information related to the vibration signal are gradually derived, so as to realize the conversion from the light intensity signal to the vibration signal related information, and complete the measurement and demodulation of the vibration signal. The present invention provides a new and accurate algorithm solution to solve the problem of improving the accuracy of integrated signal demodulation, which can accurately reflect the real range of the dual grating cascade structure sensor and can demodulate the temperature and vibration integrated signals, improve the accuracy and authenticity of the signal, complete the measurement of the vibration signal, realize the measurement of the temperature and vibration signals, and solve the problem that the dynamic vibration signal is difficult to be truly demodulated.

[0021] Furthermore, the present invention analyzes based on the real spectrum, taking into account the difference between the reflection spectrum of the real grating and the approximate function, and provides a solution for the accuracy of the demodulated vibration signal. This analysis based on actual conditions avoids the errors caused by approximate processing, and can more accurately reflect the changes in light intensity caused by the movement of the spectrum, thereby establishing a real-time and accurate relationship between the vibration signal and the light intensity. This means that the algorithm is stable under certain conditions and will not produce large deviations due to slight fluctuations in some external factors, which enhances the reliability of the algorithm in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The flowchart of the method for demodulating the light intensity of a dynamic vibration signal based on a real spectrum is shown in FIG. Figure 2 This is the schematic diagram of the demodulation system; Figure 3 The fusion process spectrum of the central wavelength from 1556.22nm to 1557.14nm in the embodiment; Figure 4 It is the inflection point characteristic diagram of the reference grating in the embodiment. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] The conventional demodulation scheme of fiber Bragg grating has problems with spectrometers, such as the inability to complete high-frequency dynamic measurements, large size, and difficulty in integrating micro sensor systems. The present invention designs a fiber Bragg grating demodulation system that adopts the principle of light intensity demodulation to improve the signal demodulation of the entire sensor system, and uses photoelectric conversion technology and equipment to study the corresponding signal decoupling mechanism for the coupling mechanism of temperature and vibration dual parameters. The designed demodulation system adopts the principle of light intensity demodulation as a whole, and the detection frequency of the signal is not limited by the demodulation equipment, which can better complete the demodulation of high-frequency signals such as vibration; at the same time, the subsequent circuit is more concise, which facilitates the transmission of signals and further improves the fiber Bragg grating integrated sensor system.

[0026] The vibration light intensity demodulation system based on dual fiber Bragg grating real spectrum includes a fiber Bragg grating vibration sensor, a fiber Bragg grating temperature sensor, a photoelectric converter, a coupler and a spectrometer; The fiber Bragg grating vibration sensor and the fiber Bragg grating temperature sensor are placed on an optical vibration table, and one end of the coupler is connected to the fiber Bragg grating vibration sensor and the fiber Bragg grating temperature sensor. The vibration sensor and the temperature sensor are arranged in the same optical fiber in a cascade structure. The light emitted by the light source is guided to the vibration sensor through a coupler, and the reflected light signal is guided to a photoelectric converter. The photoelectric converter converts the light signal into an electrical signal and inputs it into a spectrometer for fusion. The temperature grating FBG2 of the fiber Bragg grating temperature sensor is used as a reference grating; the vibration grating FBG1 on the fiber Bragg grating vibration sensor is used as a sensing grating.

[0027] Vibration is a dynamic physical quantity, and it is not possible to measure vibration using a spectrometer. Therefore, the method of converting the central wavelength of the fiber grating into light intensity is adopted, and the acceleration signal and the temperature signal are distinguished in the frequency domain using the principle of frequency division multiplexing to complete the demodulation of temperature and vibration.

[0028] The grating FBG1 on the vibration sensor is affected by external vibration changes, causing the central wavelength to move. The temperature grating FBG2 is used as a light intensity demodulation grating, and the central wavelength is not affected by the vibration, and is used as a reference grating.

[0029] During the vibration detection process, the demodulation of the central wavelength movement of FBG1 is completed by detecting the change in light intensity during the vibration process. Then the photoelectric conversion module converts the light intensity into a voltage value, thereby establishing the relationship between voltage and wavelength movement, and finally completing the static and dynamic measurement of the measured object.

[0030] The conventional demodulation scheme of fiber Bragg grating is a spectrometer with problems such as the inability to complete high-frequency dynamic measurement and large size, which makes it difficult to integrate micro sensor systems. The fiber Bragg grating demodulation system based on the principle of light intensity demodulation is designed to improve the signal demodulation of the entire sensor system. The corresponding signal decoupling mechanism is studied for the coupling mechanism of temperature and vibration dual parameters using photoelectric conversion technology and equipment. The designed demodulation system adopts the principle of light intensity demodulation as a whole. The detection frequency of the signal is not limited by the demodulation equipment, and it can better complete the demodulation of high-frequency signals such as vibration; at the same time, the subsequent circuit is more concise, which facilitates the transmission of signals and further improves the fiber Bragg grating integrated sensor system.

[0031] Among them, the vibration quantity is a dynamic physical quantity, and the vibration measurement cannot be completed using a spectrometer. Therefore, the method of converting the central wavelength shift of the fiber grating into light intensity is adopted, and the acceleration signal and the temperature signal are distinguished in the frequency domain using the frequency division multiplexing principle to complete the demodulation of temperature and vibration.

[0032] The grating FBG1 on the vibration sensor is affected by external vibration changes, causing the central wavelength to move. The temperature grating FBG2 is used as a light intensity demodulation grating, and the central wavelength is not affected by the vibration, and is used as a reference grating.

[0033] During the vibration detection process, the demodulation of the central wavelength movement of FBG1 is completed by detecting the change in light intensity during the vibration process. Then the photoelectric conversion module converts the light intensity into a voltage value, thereby establishing the relationship between voltage and wavelength movement, and finally completing the static and dynamic measurement of the measured object.

[0034] like Figure 2 As shown in the figure, the demodulation system mainly has two sensors, namely vibration sensor FBG1 and temperature sensor FBG2 (as reference grating). The two sensors are arranged in the same optical fiber in a cascade structure. The light emitted by the light source is guided to the sensor through the coupler, and the reflected light signal is guided to the photoelectric converter, which then converts the light signal into an electrical signal. The real spectrum is displayed by the spectrometer. The schematic diagram of the demodulation system is shown in the figure. Figure 2 shown.

[0035] The two sensors are placed on an optical vibration table at room temperature, and the vibration table is vibrated up and down. FBG2 is placed on the vibration table, and FBG1 is fixed on the vibration table through a threaded connection to pick up the vibration signal. The light source injects broadband light into the fiber grating of the acceleration sensor, which picks up the vibration signal and reflects it back. The vibration signal is converted into a light intensity signal using the dual fiber grating demodulation principle, and then converted into a voltage signal by a photoelectric converter, and finally displayed by an oscilloscope.

[0036] When the vibration signal acts on the FBG1 sensor, it will cause the FBG1 sensor to produce axial dynamic strain. By monitoring the strain state of the sensor, we can indirectly understand the relevant characteristics of the vibration signal. The change of the strain state also causes the central wavelength of the fiber Bragg grating to change. The FBG central wavelength changes periodically, and the changes in the vibration signal can be accurately captured by monitoring the movement of the central wavelength of the FBG.

[0037] In the demodulation system, the selection of fiber Bragg grating parameters is very important. The first thing to determine is the center wavelength of the fiber Bragg grating to ensure the range of the sensor and meet the requirements of the demodulation center wavelength of the adapted spectrometer. Then, the fiber Bragg grating is selected in combination with parameters such as length and reflectivity to ensure that there is sufficient intensity and accurate light signal returned to the demodulation device. After the fiber Bragg grating is determined, it is necessary to perform theoretical analysis through the light intensity demodulation algorithm to determine the maximum range in which the center wavelength of the fiber Bragg grating can move during the sensing process, so as to determine the range of the sensor. In this way, the structure and parameters of the fiber Bragg grating in the demodulation system are determined, and the appropriate fiber Bragg grating is selected.

[0038] The vibration light intensity demodulation method based on the real spectrum of dual fiber gratings provided by the present invention includes: Figure 1 As shown: The integrated signal output by the dual fiber Bragg grating temperature and vibration sensor is obtained, and the integrated signal is converted into an electrical signal, and then fused to obtain a fused spectrum; wherein the integrated signal includes a sensing grating signal and a reference grating signal; The fused spectrum is analyzed to obtain the optical path difference, and the optical path difference is demodulated based on the real spectrum to obtain the actual spectral optical power; The photocurrent is calculated by the actual spectral light power, and then converted into voltage; The wavelength shift of the fiber Bragg grating is obtained by voltage, and then the relationship between the wavelength shift and the axial strain is established; Based on the relationship between the wavelength shift and the axial strain, the vibration signal of the vibration amplitude and vibration frequency is obtained.

[0039] The reflection spectrum of the real spectrum is different from the approximate function, and there are also differences between the sensing grating and the reference grating, so the sensitivity analysis needs to be based on the real spectrum. The reflection spectrum of the 1556.22nm sensing grating and the 1557.14nm reference grating was measured by a spectrometer, and the wavelength of the sensing grating was moved to the long-wave direction by heating, showing the fusion process of the dual fiber Bragg grating from 1556.22nm to 1557.14nm center wavelength.

[0040] Figure 3 The fusion process of the central wavelength from 1556.22nm to 1557.14nm is shown. In order to maintain the stability of the measurement, the temperature is controlled at the same temperature to prevent the central wavelength of the sensing grating from drifting to the left due to temperature changes, which will affect the experimental results. During the fusion process, the spectrum of the spectrometer is saved, and the intensity of the spectrum reflected by the two gratings is measured by the photoelectric converter. The above process is repeated until the central wavelength of the sensing grating moves to 1557.14nm, that is, the reflection spectra of the two gratings completely overlap.

[0041] Through the analysis of the fused spectrum obtained by the spectrometer, it can be found that the highest point of the fused spectrum shows a certain pattern: when there are two highest points, the corresponding central wavelength is the central wavelength of the reference spectrum and the sensing spectrum respectively; when there are infinite highest points, the corresponding maximum central wavelength and minimum central wavelength are the central wavelengths of the reference spectrum and the sensing spectrum respectively; when there are three highest points, the corresponding maximum central wavelength and minimum central wavelength are the central wavelengths of the reference spectrum and the sensing spectrum respectively; when there is one highest point, through the concavity analysis of the fused spectrum curve, the two inflection points are the central wavelengths of the reference spectrum and the sensing spectrum respectively. The optical path difference that can be obtained from the central wavelengths of the reference spectrum and the sensing spectrum ( ).

[0042] Through experiments, it can be found that when the wavelength of the sensing grating moves, it passes through different characteristic points of the reference grating, and the fused spectrum presents segmented characteristics. Therefore, the four inflection points a, b, c, and d of the reference grating are taken as characteristic value points, such as Figure 4 As shown. The optical path difference is obtained by the above process, and the fusion spectrum is judged by the optical path difference, and then brought into the piecewise function to find the actual spectrum optical power after the two fiber gratings are fused. Assuming that the initial center wavelength of the sensing grating is the same as the center wavelength of the reference grating when it is not affected by external signals, the spectrum moves toward the long-wave direction with the influence of external signals. The actual spectrum after the two gratings are fused can be expressed in segments: when hour

[0043] when

[0044]

[0045] Where: is the difference between the central wavelengths of the sensing grating and the reference grating, that is, ; is the central wavelength of the sensing grating; is the central wavelength of the reference grating; is the actual spectral wavelength value after the two grating spectra are fused; is the optical power of the sensing grating corresponding to a single wavelength value; is the optical power of the reference grating corresponding to a single wavelength value; is the actual spectral optical power after the two grating spectra are fused; are the four eigenvalue points of the reference grating; ——The wavelengths corresponding to the four eigenvalue points of the reference grating; is the fusion coefficient of the two grating spectra, which depends on the optical power of the actual spectrum after fusion.

[0046] In the fiber Bragg grating demodulation system, the photoelectric conversion module converts the light intensity into a voltage value, thereby establishing a relationship between the voltage and the wavelength shift. The photoelectric converter converts the optical power into a photocurrent i according to the photoelectric effect, and the relationship it follows is:

[0047] Where: is the quantum efficiency of the photoelectric converter; The photocurrent is converted into a voltage V by a current-to-voltage conversion circuit, thereby establishing the relationship between voltage and center wavelength as follows:

[0048] is the equivalent resistance of the conversion circuit, is the effective area of ​​the photoelectric converter, is the relationship between the light intensity and the shift of the fiber Bragg grating center wavelength After establishing the relationship between voltage and wavelength shift using the above formula, we get , through the relationship between wavelength shift and axial strain, the axial strain can be obtained by the following formula .

[0049] , Where: , is the axial strain, The central wavelength of the vibration sensor.

[0050] Stress is related to the vibration amplitude. For the dynamic strain caused by vibration, the vibration amplitude can be obtained by analyzing the strain measurement values ​​at multiple times and combining the material properties and structural parameters.

[0051] A=m

[0052] Where: A is the vibration amplitude, m is the coefficient related to the structure, is the change of axial strain; The strain data obtained by continuous measurement over a period of time , use fast Fourier transform FFT to perform spectrum analysis and obtain the frequency component of strain changing with time. This frequency component is the frequency of the vibration signal. The specific expression is:

[0053] Where: X(n) is the discrete time signal, N is the signal length, k=0, 1, 2,...N-1, and X(k) is the corresponding frequency domain signal.

[0054] Through the above conversion process, the relationship between voltage and wavelength shift is used to gradually derive information such as amplitude and frequency related to the vibration signal, thereby realizing the conversion from light intensity signal to vibration signal related information, and completing the measurement and demodulation of the vibration signal. The present invention provides a new and accurate algorithm solution for solving the problem of improving the accuracy of integrated signal demodulation.

[0055] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A vibration light intensity demodulation method based on the real spectrum of dual fiber Bragg gratings, characterized in that: include, The integrated signal output by the dual fiber Bragg grating temperature and vibration sensor is obtained, and the integrated signal is converted into an electrical signal, and then fused to obtain a fused spectrum; wherein the integrated signal includes a sensing grating signal and a reference grating signal; The fused spectrum is analyzed to obtain the optical path difference, and the optical path difference is demodulated based on the real spectrum to obtain the actual spectral optical power; The photocurrent is calculated by the actual spectral light power, and then converted into voltage; The wavelength shift of the fiber Bragg grating is obtained by voltage, and then the relationship between the wavelength shift and the axial strain is established; Based on the relationship between the wavelength shift and the axial strain, the vibration signal of the vibration amplitude and vibration frequency is obtained.

2. The vibration light intensity demodulation method based on dual fiber Bragg grating real spectrum according to claim 1 is characterized in that: The integrated signal output by the dual fiber Bragg grating temperature and vibration sensor is obtained, and the integrated signal is converted into an electrical signal, and then fused to obtain a fused spectrum. The specific process is as follows: The integrated signal output by the temperature and vibration sensor of the dual fiber Bragg grating is obtained, wherein the integrated signal includes a sensing grating signal and a reference grating signal. The reflection spectra of the sensing grating signal and the reference grating signal are measured by a spectrometer. The wavelength of the sensing grating signal is moved toward the long-wave direction by heating, and the spectra are fused. During the fusion process, the spectrum measured by the spectrometer is saved, and the light intensity of the spectrum reflected by the two sensing grating signals and the reference grating signal is measured by a photoelectric converter. The above fusion process steps are repeated until the central wavelength of the sensing grating signal moves to the preset wavelength of the reference grating signal, and the reflection spectra of the sensing grating signal and the reference grating signal overlap, and then the fused spectrum is obtained.

3. The vibration light intensity demodulation method based on dual fiber Bragg grating real spectrum according to claim 1 is characterized in that: The fused spectrum is analyzed to obtain the optical path difference, which is: By analyzing the concavity of the fused spectrum curve, the central wavelengths of the reference grating and the sensor grating are obtained at the two inflection points of the fused spectrum curve, and the optical path difference is obtained through the central wavelengths of the reference grating and the sensor grating. .

4. The vibration light intensity demodulation method based on dual fiber Bragg grating real spectrum according to claim 3 is characterized in that: Optical path difference ; In the formula, is the central wavelength of the sensing grating, is the central wavelength of the reference grating.

5. The vibration light intensity demodulation method based on dual fiber Bragg grating real spectrum according to claim 1 is characterized in that: The actual spectral light power is used to obtain the photocurrent, which is converted into voltage, specifically: The photoelectric converter converts the actual spectral light power into P Converted to photocurrent i , photocurrent i Converted to voltage by current-voltage conversion circuit V ; Among them, the photocurrent i The relationship with the actual spectral optical power is: Where: i is the photocurrent, is the quantum efficiency of the photoelectric converter, and P is the actual spectral light power.

6. The vibration light intensity demodulation method based on dual fiber Bragg grating real spectrum according to claim 1 is characterized in that: The wavelength shift of the fiber Bragg grating is obtained by voltage. The specific expression is: Where: V is the voltage, R is the equivalent resistance of the conversion circuit, A is the effective area of ​​the photoelectric converter, is the relationship between the light intensity and the shift of the fiber Bragg grating center wavelength, is the wavelength shift.

7. The vibration light intensity demodulation method based on dual fiber Bragg grating real spectrum according to claim 6 is characterized in that: The relationship between wavelength shift and axial strain is as follows: Where: is the conversion coefficient of different optical paths, is the axial strain, The central wavelength of the vibration sensor, is the wavelength shift.

8. The vibration light intensity demodulation method based on dual fiber Bragg grating real spectrum according to claim 1 is characterized in that: The specific process of obtaining the vibration amplitude is: For the dynamic axial strain caused by vibration, the vibration amplitude is obtained by analyzing the changes in the axial strain at multiple moments and combining the material properties and structural parameters. The specific expression is: A=m Where: A is the vibration amplitude, m is the coefficient related to the material structure, is the change in axial strain.

9. The vibration light intensity demodulation method based on dual fiber Bragg grating real spectrum according to claim 1, characterized in that: The specific process of obtaining the vibration frequency is: The change in axial strain measured continuously over a period of time , the fast Fourier transform FFT is used for spectrum analysis to obtain the vibration frequency component of the axial strain changing with time. The vibration frequency component is the vibration frequency of the vibration signal. The specific expression is: Where: X(n) is the discrete time signal, N is the signal length, k=0, 1, 2,...N-1, and X(k) is the corresponding frequency domain signal.

10. The vibration light intensity demodulation system based on the real spectrum of dual fiber Bragg gratings is characterized by: Including fiber Bragg grating vibration sensor, fiber Bragg grating temperature sensor, photoelectric converter, coupler and spectrometer; The fiber Bragg grating vibration sensor and the fiber Bragg grating temperature sensor are placed on an optical vibration table, and one end of the coupler is connected to the fiber Bragg grating vibration sensor and the fiber Bragg grating temperature sensor. The vibration sensor and the temperature sensor are arranged in the same optical fiber in a cascade structure. The light emitted by the light source is guided to the vibration sensor through a coupler, and the reflected light signal is guided to a photoelectric converter. The photoelectric converter converts the light signal into an electrical signal and inputs it into a spectrometer for fusion. The temperature grating FBG2 of the fiber Bragg grating temperature sensor is used as a reference grating; the vibration grating FBG1 on the fiber Bragg grating vibration sensor is used as a sensing grating.

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