CN114111909A - Fiber Bragg grating temperature and stress dual-parameter integrated sensing and demodulating system based on diffraction grating - Google Patents
Fiber Bragg grating temperature and stress dual-parameter integrated sensing and demodulating system based on diffraction grating Download PDFInfo
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- CN114111909A CN114111909A CN202111445213.1A CN202111445213A CN114111909A CN 114111909 A CN114111909 A CN 114111909A CN 202111445213 A CN202111445213 A CN 202111445213A CN 114111909 A CN114111909 A CN 114111909A
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- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35306—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement
- G01D5/35309—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer
- G01D5/35316—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using an interferometer arrangement using multiple waves interferometer using a Bragg gratings
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Abstract
本发明公开了一种基于衍射光栅的光纤布拉格光栅温度、应力双参数一体式传感及解调系统，属于光纤光学测量技术领域，包括光电转换装置、电源驱动模块、信号采集模块和信号解调模块；光电转换装置包括功率可调的宽带光源、光纤环形器、1*N路耦合器、光纤布拉格光栅和光电转换模块；电源驱动模块用于为光电转换模块供电，通过调整供电频率实现静、动态测量功能；信号采集模块用于采集光电转换模块的输出信号；信号解调模块用于对采集信号进行解调，获得各路光纤布拉格光栅的中心波长，通过中心波长与温度/应变的对应关系，实时获得待测物体表面不同位置的温度和应力变化。本发明能够实现对温度和应力的一体式测量，并对静、动态光谱均可测量。
The invention discloses a fiber Bragg grating temperature and stress dual-parameter integrated sensing and demodulation system based on diffraction grating, belonging to the technical field of optical fiber measurement, comprising a photoelectric conversion device, a power drive module, a signal acquisition module and a signal demodulation module; the photoelectric conversion device includes a power-adjustable broadband light source, an optical fiber circulator, a 1*N coupler, a fiber Bragg grating and a photoelectric conversion module; the power drive module is used to supply power to the photoelectric conversion module, and the static, Dynamic measurement function; the signal acquisition module is used to collect the output signal of the photoelectric conversion module; the signal demodulation module is used to demodulate the acquired signal to obtain the center wavelength of each fiber Bragg grating, through the corresponding relationship between the center wavelength and temperature/strain , to obtain the temperature and stress changes at different positions on the surface of the object to be measured in real time. The invention can realize the integrated measurement of temperature and stress, and can measure both static and dynamic spectra.
Description
Technical Field
The invention belongs to the technical field of optical fiber optical measurement, and particularly discloses a diffraction grating-based optical fiber Bragg grating temperature and stress dual-parameter integrated sensing and demodulating system.
Background
The temperature and the stress are important monitoring contents in the building structure health monitoring, the temperature and the stress in the building construction and use process are monitored, the changes of performance parameters such as stress, deformation, temperature, thermal expansion and the like of the building during construction and operation can be accurately reflected, the aging, damage position and degree of the building can be effectively evaluated through calculation, the structure health condition, reliability, durability, bearing capacity and other performances of the building can be comprehensively evaluated, and evaluation basis is provided for later maintenance, maintenance and management of the building.
At present, the temperature and stress monitoring technology based on fiber optics mainly comprises Fiber Bragg Grating (FBG) and Brillouin Optical Time Domain Analyzer (BOTDA) technologies. FBG has the advantages of high measurement accuracy, simple structure, convenient installation, electromagnetic interference resistance, acid and alkali corrosion resistance and the like, and is widely applied to the structural health detection of buildings. In recent years, fiber grating demodulation techniques have been developed rapidly, and there are many methods, mainly including wavelength demodulation, polarization demodulation, phase demodulation, frequency demodulation, and the like. The wavelength demodulation has the advantages of high demodulation rate, good stability, small volume and the like, so that the wavelength demodulation is generally applied.
There are also many methods for detecting the wavelength drift amount of the fiber grating, and the methods can be classified into a matched grating filtering method, an unbalanced M-Z interferometer method, a tunable filter method, and the like. Although the matched grating filtering method has no absolute requirement on the light intensity of the detected spectrum and does not influence the output result on the noise with various intensities, the precision is easily influenced by the stability of a light source and external interference, and the requirement on a detector is higher; the unbalanced M-Z interferometer is easily influenced by the environment, so that the unbalanced M-Z interferometer can be used for high-resolution measurement of dynamic strain of more than 100Hz, has a limited measurement range due to the phase change range of the interferometer and is not suitable for measurement of static strain; the tunable F-P filtering method has the advantages of good system stability, small volume and capability of directly outputting electric signals corresponding to spectral wavelengths, but for a high-precision F-P filter, the detection precision can be influenced by the characteristics of nonlinearity and non-repeatability, the price is high, and the development cost is high.
Under the above circumstances, it is becoming more and more important to find a demodulation system that has a variable demodulation frequency, a simple structure, and is capable of measuring both static and dynamic spectra and simultaneously detecting temperature and strain.
Disclosure of Invention
The invention aims to provide a fiber Bragg grating temperature and stress double-parameter integrated sensing and demodulating system based on a diffraction grating, which aims to solve the problems that the cost is high, the static and dynamic spectrum measurement functions cannot be realized, and the temperature and the stress cannot be measured simultaneously in the prior art.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a fiber Bragg grating temperature and stress double-parameter integrated sensing and demodulating system based on a diffraction grating comprises a photoelectric conversion device, a power supply driving module, a signal acquisition module and a signal demodulating module;
the photoelectric conversion device comprises a broadband light source with adjustable power, a first connecting optical fiber, an optical fiber circulator, a second connecting optical fiber, a 1 x N path coupler, an optical fiber Bragg grating, a third connecting optical fiber and a photoelectric conversion module; the broadband light source emits light which is connected to a first port of the optical fiber circulator through a first connecting optical fiber, a second port of the optical fiber circulator is connected with an incident port of the 1X N-path coupler through a second connecting optical fiber, a light splitting port of the 1X N-path coupler is connected with the N-path fiber Bragg gratings, each N-path fiber Bragg grating comprises at least one temperature measuring grating and one stress measuring grating, and the N-path fiber Bragg gratings are attached to the surface of an object to be measured;
the third port of the optical fiber circulator is connected with a photoelectric conversion module, the photoelectric conversion module comprises a diffraction grating and a photodiode array, light reflected by the N fiber Bragg gratings is converged by the 1 × N coupler and then returns to the third port of the optical fiber circulator from the optical fiber circulator, the light is transmitted to the diffraction grating through a third connecting optical fiber, light with different wavelengths is imaged to different positions of the photodiode array, and the light is converted into electric signals with corresponding intensities;
the signal acquisition module is used for acquiring electric signals of different positions of the photodiode array;
the power supply driving module is used for supplying power to the photodiode array and realizing static and dynamic measurement functions by adjusting power supply frequency;
the signal demodulation module is used for acquiring the acquired electric signals, demodulating the central wavelength of each path of fiber Bragg grating, and acquiring the temperature and stress changes of different positions on the surface of the object to be detected in real time according to the corresponding relation between the central wavelength and the temperature/strain.
Preferably, the fiber bragg grating is attached to different positions on the surface of the object to be measured, and is used for acquiring temperature or stress values at different positions.
Preferably, the diffraction grating adopts second-order diffraction, wherein the first-order diffraction grating is used for performing first-order diffraction on the reflection spectrum of each path of fiber bragg grating, and the light beam emitted to the grating is dispersed according to different wavelengths and then diffracted to the second-order diffraction grating; the second-order diffraction grating performs second-order diffraction on the reflection spectrum, light with different wavelengths is obviously distinguished, and then the light is transmitted to different positions of the photodiode array for imaging.
Preferably, the light after the second-order diffraction is reflected by a reflecting mirror and then is vertically incident on the photodiode array.
Preferably, the demodulation method of the signal demodulation module is as follows:
1) reading electric signals of different positions of the photodiode array obtained by the signal acquisition module, and obtaining original spectrum data after A/D conversion;
2) the original spectrum data with the signal intensity larger than the threshold value is reserved as effective spectrum data, peak separation is carried out on the effective spectrum data by adopting a peak searching algorithm, and the maximum value coordinate of each single-peak signal is recorded;
3) carrying out Gaussian fitting on the effective spectrum data by using the maximum value coordinate of each unimodal signal to obtain the central wavelength of each effective spectrum data;
4) and obtaining the temperature and stress changes of different positions of the surface of the object to be measured in real time through the corresponding relation between the central wavelength and the temperature/strain.
The beneficial effects of this technical scheme lie in: (1) the invention realizes a fiber Bragg grating temperature and stress dual-parameter integrated sensing and demodulating system based on a diffraction grating by a method of setting a temperature compensation FBG.
(2) The scheme integrates the light source, the circulator, the coupler, the photoelectric conversion module and the embedded system, and has good stability and small volume.
(3) The invention can realize the function of variable demodulation frequency of the FBG center wavelength by adjusting the power supply frequency of the power supply driving module and changing the frequency of the electric signal output by the detector array, and can realize the measurement of both static and dynamic spectrums.
(4) The invention adopts a mode of adding a photodiode array to a diffraction grating, and uses a first-order diffraction grating to perform first-order diffraction on the reflection spectrum of each path of fiber Bragg grating, and light beams emitted to the grating are dispersed according to different wavelengths and then are diffracted to a second-order diffraction grating; the second-order diffraction grating performs second-order diffraction on the reflection spectrum, light with different wavelengths is obviously distinguished and then transmitted to different positions of the photodiode array for imaging, the demodulation precision of the FBG central wavelength is effectively improved, and the demodulation precision can reach 2 pm.
Drawings
Fig. 1 is a schematic structural diagram of a fiber bragg grating temperature and stress dual-parameter integrated sensing and demodulating system based on a diffraction grating according to an embodiment of the present invention:
fig. 2 is a flowchart of a computer demodulation procedure in the sensing and demodulation system shown in fig. 1.
Fig. 3 is a diagram of the results of demodulating multiple FBGs identified in a system.
FIG. 4 is a graph of the test results of three FBGs with different center wavelengths cured on a cantilever structure through a photoresist.
Fig. 5 is a graph of the demodulation accuracy results of the demodulation system when the FBG is under no stress and temperature effects.
In the figure: the power-adjustable broadband optical fiber connector comprises a broadband light source 1 with adjustable power, a first connecting optical fiber 2, an optical fiber circulator 3, a second connecting optical fiber 4, a 1 x N-path coupler 5, an optical fiber Bragg grating 6, a third connecting optical fiber 7, a diffraction grating 8, a reflector 9, a photodiode array 10, an embedded system 11 integrated with a signal acquisition module and a power supply driving module, a USB data line 12 and a signal demodulation module 13.
Detailed Description
The invention is explained in further detail below with reference to the figures and examples:
as shown in figures 1-2: a fiber Bragg grating temperature and stress double-parameter integrated sensing and demodulating system based on a diffraction grating comprises a photoelectric conversion device, a power supply driving module, a signal acquisition module and a signal demodulating module.
The photoelectric conversion device comprises a broadband light source 1 with adjustable power, a first connecting optical fiber 2, an optical fiber circulator 3, a second connecting optical fiber 4, a 1 x N-path coupler 5, an optical fiber Bragg grating 6, a third connecting optical fiber 7 and a photoelectric conversion module, wherein the photoelectric conversion module comprises a diffraction grating 8, a reflector 9 and a photodiode array 10; the power-adjustable broadband light source 1 is connected to a first port of the optical fiber circulator 3 through a first connecting optical fiber 2, a second port of the optical fiber circulator 3 is connected with an incident port of the 1 × N coupler 5 through a second connecting optical fiber 4, and a light splitting port of the 1 × N coupler 5 is connected with the N fiber Bragg gratings 6. In this embodiment, one or more paths may be arbitrarily selected as the temperature compensation sensor, and the other paths may be used as the stress sensors. The reflection spectrum of the N paths of fiber Bragg gratings is converged by the 1 × N path of couplers and then returns to the third port of the fiber circulator 3, the third port of the fiber circulator 3 is connected to the photoelectric conversion module through a third connecting fiber 7, the reflection spectrum of the fiber Bragg grating 6 is incident on the photodiode array 10 through a diffraction grating 8 and a reflector 9 in the photoelectric conversion module, and under the diffraction action of the diffraction grating, light with different wavelengths is imaged on different positions of the photoelectric detector array, so that the reflection spectrum of the fiber Bragg grating 6 is converted into an electric signal.
In one embodiment of the invention, a diffraction grating is used to spatially separate wavelength spectra, where a uniquely high optical resolution optimization is performed, in conjunction with compact size, to rotate light 360 degrees in a small space. The diffraction grating adopts second-order diffraction, wherein the first-order diffraction grating is used for performing first-order diffraction on the reflection spectrum of each path of fiber Bragg grating, and light beams emitted to the grating are dispersed according to different wavelengths and then are diffracted to the second-order diffraction grating; the second-order diffraction grating performs second-order diffraction on the reflection spectrum, light with different wavelengths is obviously distinguished, and then the light is transmitted to different positions of the photodiode array for imaging.
The power supply driving module and the signal acquisition module are integrated in an embedded system, the embedded system receives a voltage signal which is from the photodiode array 10 and is converted by a Fiber Bragg Grating (FBG) reflection spectrum, an analog electric signal is converted into a digital signal through an A/D conversion circuit, and the digital signal is transmitted to the signal demodulation module 13 through the USB data line 12; the embedded system has a power supply function, outputs a driving power supply for the photodiode array 10 to work, and the supply frequency of the driving power supply directly influences the output frequency of the voltage signal of the photoelectric conversion module.
When the FBG for detection is subjected to slowly changing stress or under the condition of not drastic temperature change, the low-frequency measurement can meet the detection requirement, and the real change condition can be restored by a high-frequency measurement means in some scenes. The frequency of the voltage signal output by the photoelectric conversion module is controlled by controlling the frequency of the voltage pulse output by the driving power supply module in the embedded system, the photoelectric conversion module converts the energy spectrum of the reflection spectrum of the FBG into the corresponding voltage signal and outputs the voltage signal, the photoelectric conversion module outputs a group of voltage signals every time the reflection spectrum is scanned, the frequency of the voltage signal output by the photoelectric conversion module is the detection frequency of the spectrum change (FBG central wavelength change), and the stress and temperature changes corresponding to the FBG central wavelength change can be obtained after the output voltage signal is processed by the signal acquisition module and the signal demodulation module, so the demodulation frequency can be controlled by controlling the output frequency of the driving power supply module. The signal demodulation module is in real-time communication with the embedded system through a USB data line, and initialization setting of the output frequency of the driving power supply module can be completed by sending an instruction to the embedded system, so that the demodulation frequency can be controlled in an upper computer (the signal demodulation module) in a man-machine interaction mode, the function of variable demodulation frequency of the FBG center wavelength can be realized, and both static and dynamic spectrums (low-frequency measurement and high-frequency measurement) can be measured.
The signal demodulation module 13 is configured to demodulate the received digital signal, and obtain the central wavelength of the FBG reflected spectrum displayed in real time and the stress and temperature varying with time by performing steps such as setting a threshold, peak finding algorithm, threshold peak splitting, gaussian fitting on the obtained spectrum raw data.
The system can simultaneously provide a demodulation mode of temperature and stress, and according to the sensing principle of the fiber Bragg grating, when the wavelength meets the Bragg wavelength type lambdaB＝2neffAt Λ, the incident light will be reflected back by the fiber bragg grating, since the fiber bragg grating is sensitive to both stress and temperature, the stress influences λ by the elasto-optic effect and the variation of the fiber grating period ΛBThe temperature influences the lambda through the thermo-optic effect and the thermal expansion effectB. When the fiber grating is stressed, the refractive index and period of the fiber grating change, causing the reflection wavelength lambdaBMoving, therefore, there are:
in the formula: Δ neffIs a change in refractive index, ΔΛIs the variation of the grating period.
The refractive index change equation when the grating generates stress is as follows:
in the formula: ε is the axial strain, μ is the Poisson's ratio of the core material, P11、P12Is the elasto-optic coefficient, PeIs the effective elasto-optic coefficient. The fiber grating is assumed to be absolutely uniform, that is, the relative rate of change of the period of the grating and the relative rate of change of the physical length of the grating segments are identical.
Therefore:
central reflection wavelength lambda caused by temperature changeBThe movement can be expressed as
In the formula (I), the compound is shown in the specification,
describing the variation relation of the period of the grating with the temperature for the thermal expansion coefficient of the optical fiber;
the change of the effective refractive index of the grating with temperature is described as the thermo-optic coefficient of the optical fiber.
According to the formula, the variation of the stress and the temperature and the wavelength offset are in a linear relation, and the system can not measureShift of central wavelength by delta lambda with fibre bragg gratingBBy setting the temperature compensation FBG method, the change of temperature and stress can be measured simultaneously. The setting method of the temperature compensation FBG is as follows: the FBGs which measure the stress on other paths can cause the wavelength to change because of the change of the temperature, and the FBG which measures the temperature only is the temperature compensation FBG. The wavelength change of the FBG arranged as the stress sensor minus the wavelength change of the FBG arranged as the temperature sensor is the wavelength change caused by the stress, and the change conditions of the stress and the temperature can be respectively obtained through linear relational expressions of the wavelength change and the stress and the temperature.
The working process of the measuring system of the invention is as follows:
light emitted by a broadband light source 1 with adjustable power is coupled to a first port of a fiber circulator 3 through a first connecting fiber 2 and is emitted from a second port, light emitted from the second port of the fiber circulator 3 is coupled to an input port of a 1 x N-way coupler 5 through a second connecting fiber 4, light splitting ports of the 1 x N-way coupler 5 are connected with fiber Bragg gratings 6, light entering from the input port of the 1 x N-way coupler is respectively emitted into the light splitting ports of the coupler, reflected light of the fiber Bragg gratings converged by the light splitting ports of the N-way coupler returns to three ports of the fiber circulator 3, the reflected light of the fiber Bragg gratings is coupled into the three ports of the fiber circulator 3 and then is emitted into a photoelectric conversion module through a third connecting fiber 7, the reflected light of the fiber Bragg gratings 6 is emitted onto a photodiode array 10 through a diffraction grating 8 and a reflector 9 of the photoelectric conversion module, thereby converting the reflection spectrum of the fiber bragg grating 6 into an electrical signal. The photoelectric conversion module is connected with an embedded system 11 integrated by a power supply driving module and a signal acquisition module through an external circuit board, the embedded system receives a voltage signal from the photodiode array 10 and converted by FBG reflection spectrum, an analog signal is converted into a digital signal through an A/D conversion circuit, the embedded system outputs a driving power supply to supply the photodiode array 10 to work, and the supply frequency of the driving power supply directly influences the output frequency of the voltage signal of the photoelectric conversion module.
The embedded system 11 processes the digital voltage signal after a/D conversion and transmits the processed digital voltage signal to the signal demodulation module 13 through the USB data line 12, and in this embodiment, a computer is used as the signal demodulation module, and the obtained spectrum raw data is subjected to steps of setting a threshold, searching a peak algorithm, threshold peak splitting, gaussian fitting, and the like, so as to obtain the central wavelength of the FBG reflection spectrum displayed in real time and stress and temperature changing along with time.
In one embodiment of the present invention, as shown in fig. 3, the demodulation process is:
1) and reading the electric signals of different positions of the photodiode array obtained by the signal acquisition module, and obtaining original spectrum data after A/D conversion.
2) And (3) reserving the original spectrum data with the signal intensity larger than the threshold value as effective spectrum data, performing peak separation on the effective spectrum data by adopting a peak searching algorithm, and recording the maximum value coordinate of each single peak signal.
3) Carrying out Gaussian fitting on the effective spectrum data by using the maximum value coordinate of each unimodal signal to obtain the central wavelength of each effective spectrum data; in this embodiment, taking 10 FBGs as an example, as shown in fig. 3, the result graph of identifying a plurality of FBGs can display the FBG reflection spectrum and the center wavelength of each FBG that is fitted.
4) And obtaining the temperature and stress changes of different positions of the surface of the object to be measured in real time through the corresponding relation between the central wavelength and the temperature/strain.
Taking the cantilever beam structure as an example, in this embodiment, three FBGs with different central wavelengths are cured on three points to be measured of the cantilever beam structure through the photoresist, and a tapping experiment is performed on the cantilever beam, and the measured dynamic change conditions of the central wavelengths of the three FBGs are shown in (a), (b) and (c) of fig. 4. The embodiment tests the demodulation accuracy of the system, and as shown in fig. 5, when the FBG is in the condition without the influence of stress and temperature, the demodulation accuracy of the system is controlled within the range of 2 pm.
The foregoing is merely an example of the present invention and common general knowledge of known specific structures and features of the embodiments is not described herein in any greater detail. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.
Claims (5)
1. A fiber Bragg grating temperature and stress double-parameter integrated sensing and demodulating system based on a diffraction grating is characterized by comprising a photoelectric conversion device, a power supply driving module, a signal acquisition module and a signal demodulating module;
the photoelectric conversion device comprises a broadband light source (1) with adjustable power, a first connecting optical fiber (2), an optical fiber circulator (3), a second connecting optical fiber (4), a 1 × N coupler (5), an optical fiber Bragg grating (6), a third connecting optical fiber (7) and a photoelectric conversion module; the broadband light source (1) emits light which is connected to a first port of the optical fiber circulator (3) through a first connecting optical fiber (2), a second port of the optical fiber circulator (3) is connected with an incident port of the 1 x N-path coupler (5) through a second connecting optical fiber (4), a light splitting port of the 1 x N-path coupler (5) is connected with the N-path fiber Bragg gratings (6), the N-path fiber Bragg gratings (6) comprise at least one temperature measuring grating and one stress measuring grating, and the N-path fiber Bragg gratings (6) are attached to the surface of an object to be measured;
the third port of the optical fiber circulator (3) is connected with a photoelectric conversion module, the photoelectric conversion module comprises a diffraction grating and a photodiode array (10), light reflected by the N paths of optical fiber Bragg gratings (6) is converged by the 1 x N path coupler 5 and then returns to the third port of the optical fiber circulator (3) from the optical fiber circulator (3), the light is transmitted to the diffraction grating through a third connecting optical fiber (7), and light with different wavelengths is imaged to different positions of the photodiode array (10) and converted into electric signals with corresponding intensities;
the signal acquisition module is used for acquiring electric signals of different positions of the photodiode array (10);
the power supply driving module is used for supplying power to the photodiode array (10) and realizing static and dynamic measurement functions by adjusting power supply frequency;
the signal demodulation module is used for acquiring the acquired electric signals and demodulating the central wavelength of each path of fiber Bragg grating (6), and the temperature and stress changes of different positions on the surface of the object to be detected are obtained in real time through the corresponding relation between the central wavelength and the temperature/strain.
2. The diffraction grating-based fiber bragg grating temperature and stress dual-parameter integrated sensing and demodulating system as claimed in claim 1, wherein the fiber bragg grating (6) is attached to different positions on the surface of an object to be measured, and is used for acquiring temperature or stress values at different positions.
3. The system of claim 1, wherein the diffraction grating is a two-level diffraction grating, wherein the first-level diffraction grating is configured to perform a first-level diffraction on the reflection spectrum of each fiber bragg grating, and the light beam incident on the grating is dispersed according to different wavelengths and then diffracted to the second-level diffraction grating; the second-order diffraction grating carries out second-order diffraction on the reflection spectrum, light with different wavelengths is obviously distinguished, and then the light is transmitted to different positions of the photodiode array (10) for imaging.
4. The system for sensing and demodulating fiber Bragg grating temperature and stress double-parameter integrated type based on diffraction grating as claimed in claim 3, wherein the light after secondary diffraction is reflected by the reflector (9) and then vertically incident on the photodiode array (10).
5. The system for sensing and demodulating fiber Bragg grating temperature and stress integrated type based on diffraction grating of claim 1, wherein the demodulation method of the signal demodulation module is as follows:
1) reading electric signals of different positions of the photodiode array (10) obtained by the signal acquisition module, and obtaining original spectrum data after A/D conversion;
2) the original spectrum data with the signal intensity larger than the threshold value is reserved as effective spectrum data, peak separation is carried out on the effective spectrum data by adopting a peak searching algorithm, and the maximum value coordinate of each single-peak signal is recorded;
3) carrying out Gaussian fitting on the effective spectrum data by using the maximum value coordinate of each unimodal signal to obtain the central wavelength of each effective spectrum data;
4) and obtaining the temperature and stress changes of different positions of the surface of the object to be measured in real time through the corresponding relation between the central wavelength and the temperature/strain.
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