High-sensitivity wind speed sensor, wind speed measuring method and preparation method

Abstract

The invention relates to a high-sensitivity wind speed sensor, a wind speed measuring method and a preparation method, and the high-sensitivity wind speed sensor comprises a broadband light source, a first circulator, a first optical fiber Fabry-Perot interference cavity, a second circulator, a second optical fiber Fabry-Perot interference cavity and a spectrometer. The output end of the broadband light source is connected with the first port of the first circulator; a second port of the first circulator is connected with an input end of the first optical fiber Fabry-Perot interference cavity; a third port of the first circulator is connected with a first port of the second circulator; the second port of the second circulator is connected with the input end of the second optical fiber Fabry-Perot interference cavity; and a third port of the second circulator is connected with the input end of the spectrograph. The high-sensitivity wind speed sensor has the advantages of being resistant to electromagnetic interference, good in environmental adaptability and high in sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing and wind speed measurement technology, specifically relating to a high-sensitivity wind speed sensor, a wind speed measurement method, and a preparation method. Background Technology

[0002] Accurate wind speed measurement is crucial in fields such as meteorological monitoring, aerospace, wind power generation, environmental engineering, and industrial safety. Traditional wind speed sensors, such as hot-wire anemometers, while offering fast response times, are susceptible to electromagnetic interference due to their electrical sensing principle. Furthermore, their reliability decreases significantly in high-temperature, high-humidity, or corrosive environments, limiting their application range.

[0003] Anemometers based on fiber optic Fabry-Perot interferometers utilize optical interference principles for measurement, offering advantages such as inherent resistance to electromagnetic interference, corrosion resistance, and suitability for remote monitoring. They provide a novel solution for wind speed measurement in harsh environments. These sensors typically achieve sensing by modulating the interference spectrum through changes in the cavity length caused by wind speed. However, the optical sensitivity (i.e., the spectral shift caused by a unit change in wind speed) of a single Fabry-Perot interferometer anemometer is directly limited by the inherent optical response of the single cavity. This means that for minute changes in wind speed, the resulting spectral shift signal is extremely weak and easily drowned out by system noise, leading to limited measurement sensitivity and insufficient resolution. This makes it difficult to meet the stringent requirements of high-precision, high-stability applications (such as boundary layer wind field research and precision industrial airflow control).

[0004] Therefore, it is of great practical value to develop a novel sensing structure and method that can significantly amplify weak optical signals caused by wind speed, while retaining the inherent advantages of fiber optic sensors and breaking through the sensitivity bottleneck of single interference cavities. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-sensitivity wind speed sensor; the high-sensitivity wind speed sensor has the advantages of anti-electromagnetic interference, good environmental adaptability and high sensitivity.

[0006] The second objective of this invention is to provide a wind speed measurement method using a high-sensitivity wind speed sensor.

[0007] The third objective of this invention is to provide a method for preparing a high-sensitivity wind speed sensor.

[0008] The technical solution of the present invention to solve the above-mentioned technical problems is:

[0009] A high-sensitivity wind speed sensor includes a broadband light source, a first circulator, a first fiber Fabry-Perot interferometer, a second circulator, a second fiber Fabry-Perot interferometer, and a spectrometer, wherein...

[0010] The output of the broadband light source is connected to the first port of the first circulator; the second port of the first circulator is connected to the input of the first fiber Fabry-Perot interferometer; the third port of the first circulator is connected to the first port of the second circulator; the second port of the second circulator is connected to the input of the second fiber Fabry-Perot interferometer; and the third port of the second circulator is connected to the input of the spectrometer.

[0011] Preferably, both the first fiber Fabry-Perot interferometer cavity and the second fiber Fabry-Perot interferometer cavity are fiber end-face thin-film type Fabry-Perot cavities.

[0012] Preferably, a polymer thin film cavity is directly fabricated on the end face of a single-mode optical fiber using two-photon polymerization 3D printing technology, thereby obtaining the optical fiber end face thin film type Fabry-Perot cavity.

[0013] Preferably, the first fiber Fabry-Perot interferometer cavity is provided with a first reflecting surface and a second reflecting surface; the second fiber Fabry-Perot interferometer cavity is provided with a third reflecting surface and a fourth reflecting surface, wherein the first reflecting surface and the second reflecting surface have a first reflectivity; the third reflecting surface and the fourth reflecting surface have a second reflectivity; and the values ​​of the first reflectivity and the second reflectivity are both in the range of 0.01 to 0.1.

[0014] Preferably, the thin film containing the second reflective surface has a first effective radius and a first thickness, and the thin film containing the fourth reflective surface has a second effective radius and a second thickness; wherein the values ​​of the first effective radius and the second effective radius are both in the range of 50 micrometers to 150 micrometers; and the values ​​of the first thickness and the second thickness are both in the range of 30 micrometers to 200 micrometers.

[0015] Preferably, the initial optical cavity length of the first fiber Fabry-Perot interferometer cavity is not equal to the initial optical cavity length of the second fiber Fabry-Perot interferometer cavity, and each of them has a value range of 100 micrometers to 600 micrometers.

[0016] Preferably, the output spectral range of the broadband light source covers 1250nm to 1650nm.

[0017] Preferably, the broadband light source, the first circulator, the first fiber Fabry-Perot interferometer cavity, the second circulator, the second fiber Fabry-Perot interferometer cavity, and the spectrometer are all optically connected via single-mode optical fibers and fiber optic connectors.

[0018] A method for measuring wind speed includes the following steps:

[0019] S1: The first fiber Fabry-Perot interferometer cavity is placed in the wind speed environment to be measured as the sensing cavity, and the second fiber Fabry-Perot interferometer cavity is placed in a constant windless environment as the reference cavity.

[0020] S2: The broadband light source is turned on. The broadband light emitted by the broadband light source is transmitted to the first fiber Fabry-Perot interferometer cavity through the first circulator. The broadband light incident on the first fiber Fabry-Perot interferometer cavity undergoes the first multi-beam interference and forms the first interference signal. The reflected light of the first interference signal passes through the first circulator and the second circulator in sequence and then enters the second fiber Fabry-Perot interferometer cavity.

[0021] S3: The broadband light incident on the second fiber Fabry-Perot interferometer cavity undergoes a second multi-beam interference and forms a second interference signal; the reflected light of the second interference signal is transmitted to the spectrometer via the second circulator to form a composite interference spectrum obtained by superimposing the first interference signal and the second interference signal;

[0022] S4: Monitor the wavelength shift of the composite interference spectrum using a spectrometer and calculate the wind speed value based on the preset calibration relationship.

[0023] A preparation method for preparing the aforementioned high-sensitivity wind speed sensor.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. The high-sensitivity wind speed sensor of the present invention cleverly introduces a vernier amplification effect by cascading a first fiber Fabry-Perot interferometer and a second fiber Fabry-Perot interferometer with similar but unequal optical cavity lengths. The minute optical phase change of the first fiber Fabry-Perot interferometer, which serves as the sensing cavity, caused by the wind speed is modulated and amplified by the second fiber Fabry-Perot interferometer, which serves as the reference cavity, into a significant wavelength shift in the composite spectral envelope. Its sensitivity can reach more than 10 times that of a single interferometer, thereby greatly improving the detection capability of wind speed signals.

[0026] 2. The wind speed measurement method of the present invention adopts an all-fiber optical sensing scheme, which is essentially unaffected by electromagnetic interference; by placing the reference cavity in a stable environment, the influence of environmental common-mode noise such as temperature on the measurement results can be effectively suppressed, thereby greatly improving the long-term stability and reliability of the high-sensitivity wind speed sensor of the present invention.

[0027] 3. The high-sensitivity wind speed sensor of the present invention adopts a thin-film cavity structure directly formed on the end face of the optical fiber, which has the advantages of small size and easy packaging and protection; combined with the characteristics of the optical fiber itself, it is particularly suitable for harsh environments where traditional electrical sensors are difficult to operate, such as high pressure, high temperature, high humidity, corrosive or flammable and explosive environments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the high-sensitivity wind speed sensor of the present invention.

[0029] Figure 2 This is a flowchart of the wind speed measurement method of the present invention.

[0030] Figure 3 Scanning electron microscope (SEM) images of the structural morphology of the sensing cavity (left) and reference cavity (right) prepared for this invention.

[0031] Figure 4 The interference spectra of the sensing cavity and reference cavity prepared in this invention are obtained by connecting them to a spectrometer.

[0032] Figure 5 Simulation curve of the cavity length of the first fiber Fabry-Perot interferometer cavity (sensing cavity) prepared for this invention as a function of wind speed.

[0033] Figure 6 The theoretical interference spectrum simulation diagram of the first fiber Fabry-Perot interferometer cavity (sensing cavity) and the second fiber Fabry-Perot interferometer cavity (reference cavity) prepared for this invention under windless conditions.

[0034] Figure 7 The image shows a simulation of the composite interference spectrum (vernier envelope spectrum) of the cascaded system of the present invention under different wind speeds.

[0035] Figure 8 This is a simulation curve showing the characteristic wavelength of the composite interference spectrum of the cascaded system of the present invention as a function of wind speed.

[0036] In the figure: 1-Broadband light source; 2-First circulator; 3-First fiber Fabry-Perot interferometer cavity; 4-Second fiber Fabry-Perot interferometer cavity; 5-Second circulator; 6-Spectrometer. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0038] Example 1

[0039] See Figure 1The high-sensitivity wind speed sensor of the present invention includes a broadband light source, a first circulator, a first fiber Fabry-Perot interferometer, a second circulator, a second fiber Fabry-Perot interferometer, and a spectrometer. The output of the broadband light source is connected to a first port of the first circulator; a second port of the first circulator is connected to an input of the first fiber Fabry-Perot interferometer; a third port of the first circulator is connected to a first port of the second circulator; a second port of the second circulator is connected to an input of the second fiber Fabry-Perot interferometer; and a third port of the second circulator is connected to an input of the spectrometer.

[0040] See Figure 1 The output spectrum of the broadband light source covers 1250nm to 1650nm.

[0041] See Figure 1 The first fiber Fabry-Perot interferometer cavity and the second fiber Fabry-Perot interferometer cavity are both fiber end-face thin-film type Fabry-Perot cavities, that is, polymer thin-film cavities directly fabricated on the end face of a single-mode fiber using two-photon polymerization three-dimensional printing technology.

[0042] See Figure 1 The first fiber Fabry-Perot interferometer cavity is provided with a first reflecting surface and a second reflecting surface; the second fiber Fabry-Perot interferometer cavity is provided with a third reflecting surface and a fourth reflecting surface, wherein the first reflecting surface and the second reflecting surface both have a first reflectivity; the third reflecting surface and the fourth reflecting surface both have a second reflectivity, wherein the values ​​of the first reflectivity and the second reflectivity are both in the range of 0.01 to 0.1.

[0043] See Figure 1 The thin film containing the second reflective surface has a first effective radius and a first thickness, and the thin film containing the fourth reflective surface has a second effective radius and a second thickness; wherein the values ​​of the first effective radius and the second effective radius are both in the range of 50 micrometers to 150 micrometers; and the values ​​of the first thickness and the second thickness are both in the range of 30 micrometers to 200 micrometers.

[0044] See Figure 1 The initial optical cavity length of the first fiber Fabry-Perot interferometer cavity is not equal to that of the second fiber Fabry-Perot interferometer cavity, and their respective values ​​range from 100 micrometers to 600 micrometers.

[0045] See Figure 1 The broadband light source, the first circulator, the first fiber Fabry-Perot interferometer cavity, the second circulator, the second fiber Fabry-Perot interferometer cavity, and the spectrometer are all connected by single-mode optical fiber and optical fiber connectors.

[0046] See Figure 2 The wind speed measurement method of the present invention includes the following steps:

[0047] S1: The first fiber Fabry-Perot interferometer cavity is placed in the wind speed environment to be measured as the sensing cavity, and the second fiber Fabry-Perot interferometer cavity is placed in a constant windless environment as the reference cavity.

[0048] S2: The broadband light source is turned on. The broadband light emitted by the broadband light source is transmitted to the first fiber Fabry-Perot interferometer cavity (i.e., the sensing cavity) through the first circulator. The broadband light incident on the first fiber Fabry-Perot interferometer cavity undergoes the first multi-beam interference and forms the first interference signal. The reflected light of the first interference signal passes through the first circulator and the second circulator in sequence and is then incident on the second fiber Fabry-Perot interferometer cavity (i.e., the reference cavity).

[0049] S3: The broadband light incident on the second fiber Fabry-Perot interferometer cavity undergoes a second multi-beam interference and forms a second interference signal; the reflected light of the second interference signal is transmitted to the spectrometer via the second circulator, and the signal received by the spectrometer is a composite interference spectrum obtained by superimposing the first interference signal and the second interference signal; since the optical cavity lengths of the first fiber Fabry-Perot interferometer cavity and the second fiber Fabry-Perot interferometer cavity are close but not equal, the composite spectrum exhibits a periodic "vernier envelope" feature;

[0050] S4: When wind speed acts on the sensitive thin film of the first fiber Fabry-Perot interferometer cavity, the pressure difference generated based on fluid dynamics principles causes it to undergo elastic deformation, resulting in a decrease in the physical cavity length. Changes have occurred ( ); thanks to the vernier amplification effect produced by the cascaded first and second fiber Fabry-Perot interferometer cavities, tiny This will cause a significant wavelength shift in the vernier envelope of the composite interference spectrum. (Precise monitoring of wavelength shift in the envelope of the composite interference spectrum using a spectrometer) According to the pre-defined With wind speed The corresponding relationship is used to calculate the corresponding wind speed value; the core physical conversion process is: wind speed →Pressure difference ( →Cavity length change ( → (Amplified by vernier) Wavelength drift ( → Wind speed Specifically:

[0051] Conversion of wind speed to pressure difference: When airflow acts on the thin film of the first fiber Fabry-Perot interferometer cavity, a pressure difference related to wind speed is generated on the surface of the thin film. ;

[0052] Conversion from pressure difference to deformation: the pressure difference This causes elastic deformation of the thin film in the first fiber Fabry-Perot interferometer cavity, thereby changing its physical cavity length. The change is ;

[0053] Conversion from deformation to optical signal (vernier amplification): cavity length variation First, it causes a slight drift in the interference spectrum of the sensing cavity itself; this slight drift is significantly amplified by the vernier effect of the two-cavity cascade, manifesting as a macroscopic wavelength drift in the envelope of the composite interference spectrum. ;

[0054] Signal demodulation to wind speed output: by measuring the macroscopic wavelength drift. ,in accordance with With wind speed The corresponding relationship is used to calculate the wind speed value.

[0055] Example 2

[0056] This embodiment relates to the fabrication of a thin-film Fabry-Perot interferometer cavity at the fiber end face; to verify the feasibility of the high-sensitivity wind speed sensor of this invention, this embodiment provides the fabrication of the sensing cavity and the reference cavity, the specific fabrication process of which is as follows:

[0057] Using two-photon polymerization 3D printing technology, polymer thin film cavities were fabricated on the end faces of two cleaned and planarized single-mode optical fibers. By precisely controlling the scanning path and exposure dose of the femtosecond laser, two interference cavities with different optical cavity lengths were prepared. The first interference cavity, designed as a sensing cavity, has a physical cavity length of approximately 300 μm, while the second interference cavity, designed as a reference cavity, has a physical cavity length of approximately 400 μm. The film thickness of both cavities is approximately 50 μm, and the effective radius is approximately 75 μm.

[0058] Figure 3 Scanning electron microscope (SEM) images of the sensing cavity and reference cavity prepared in this embodiment show that the structure is intact and the morphology is regular. The prepared single interference cavity was connected to a broadband light source and a spectrometer, respectively, and the measurements were as follows: Figure 4 The clear interference spectrum shown demonstrates that the sensing cavity and the reference cavity prepared in this embodiment have good Fabry-Perot interference characteristics. Moreover, the free spectral range (FSR) of the sensing cavity and the reference cavity differs, which lays the foundation for subsequent cascading to generate a vernier amplification effect.

[0059] Example 3

[0060] Based on the measured parameter range of the interferometric cavity prepared in Example 2, this embodiment further predicts and verifies the performance of the high-sensitivity wind speed sensor of the present invention through theoretical simulation. The key theoretical models involved in the simulation are as follows:

[0061] 1. Wind speed-pressure model:

[0062] Pressure difference generated by airflow acting on the diaphragm of the sensing cavity With wind speed The relationship can be represented as:

[0063] ;

[0064] In the formula: The density of air is 1.2 kg / m³.

[0065] 2. Pressure-deformation model:

[0066] The membrane under pressure difference Central shape variable under action (i.e., the change in cavity length) can be expressed as:

[0067] ;

[0068] in, Poisson's ratio for thin film materials The effective radius of the thin film, For Young's modulus, For film thickness;

[0069] 3. Cascaded Interference Spectral Model:

[0070] Interference light intensity of cascaded system It can be represented as:

[0071] ;

[0072] In the formula: These are the phase differences between the two interference cavities (i.e., the sensing cavity and the reference cavity); The effective phase difference between the two interference cavities is the key to generating the vernier envelope; To be related to reflectivity Correlation coefficient;

[0073] 4. Vernier sensitivity amplification:

[0074] Wavelength drift of vernier envelope The ratio of the change in cavity length ∆L1 to the system sensitivity is the system sensitivity. , can be represented as: This value is much greater than the inherent optical sensitivity of a single interference cavity.

[0075] Simulation parameters and results analysis:

[0076] In a specific simulation setup, the parameters are as follows: the cavity length of the sensing cavity. Reference cavity length The reflectivity of each reflective surface ranges from 0.034 to 0.045; the radius of the sensing film... ,thickness Young's modulus of thin film materials Poisson's ratio .

[0077] Simulation was performed based on the above parameters: Figure 5 This demonstrates the effect of wind speed on the cavity length L1 of the sensing cavity. The simulation curves that increase and decrease are consistent with the theoretical model; Figure 6 The simulation diagrams of the single-cavity interference spectra of the sensing cavity and the reference cavity under windless conditions are shown, and their free spectral ranges are different. Figure 7 Simulation diagrams of composite interferometric spectra of the cascaded system at different wind speeds (0-8 m / s) are shown. It can be clearly observed that as the wind speed increases, the vernier envelope shifts significantly towards the shortwave direction. Figure 8 The simulation curve of the vernier envelope characteristic wavelength changing with wind speed was quantitatively displayed; calculations showed that the system sensitivity (i.e., envelope wavelength drift) was approximately -8.6 to -12.6 nm / (m / s) in the wind speed range of 0-8 m / s.

[0078] Therefore, the simulation results above show that, based on the cascade structure and vernier effect, the wind speed sensor of the present invention achieves a significant amplification of the sensitivity of a single cavity; in the wind speed range of 0-5 m / s, its simulated sensitivity can reach tens of times that of a traditional single Fabry-Perot interferometer wind speed sensor, which fully verifies the technical advantages of the present invention in high-sensitivity wind speed measurement.

[0079] The above are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above content. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A high-sensitivity wind speed sensor, characterized in that, It includes a broadband light source, a first circulator, a first fiber Fabry-Perot interferometer, a second circulator, a second fiber Fabry-Perot interferometer, and a spectrometer, among which, The output of the broadband light source is connected to the first port of the first circulator; the second port of the first circulator is connected to the input of the first fiber Fabry-Perot interferometer; the third port of the first circulator is connected to the first port of the second circulator; the second port of the second circulator is connected to the input of the second fiber Fabry-Perot interferometer; and the third port of the second circulator is connected to the input of the spectrometer.

2. The high-sensitivity wind speed sensor according to claim 1, characterized in that, Both the first fiber Fabry-Perot interferometer cavity and the second fiber Fabry-Perot interferometer cavity are fiber end-face thin-film type Fabry-Perot cavities.

3. The high-sensitivity wind speed sensor according to claim 2, characterized in that, A polymer thin-film cavity is directly fabricated on the end face of a single-mode optical fiber using two-photon polymerization 3D printing technology, thereby obtaining the aforementioned fiber end face thin-film Fabry-Perot cavity.

4. The high-sensitivity wind speed sensor according to claim 3, characterized in that, The first fiber Fabry-Perot interferometer cavity is provided with a first reflecting surface and a second reflecting surface; the second fiber Fabry-Perot interferometer cavity is provided with a third reflecting surface and a fourth reflecting surface, wherein the first reflecting surface and the second reflecting surface have a first reflectivity; the third reflecting surface and the fourth reflecting surface have a second reflectivity; the values ​​of the first reflectivity and the second reflectivity are both in the range of 0.01 to 0.

1.

5. The high-sensitivity wind speed sensor according to claim 4, characterized in that, The thin film containing the second reflective surface has a first effective radius and a first thickness, and the thin film containing the fourth reflective surface has a second effective radius and a second thickness; wherein the values ​​of the first effective radius and the second effective radius are both in the range of 50 micrometers to 150 micrometers; and the values ​​of the first thickness and the second thickness are both in the range of 30 micrometers to 200 micrometers.

6. The high-sensitivity wind speed sensor according to claim 5, characterized in that, The initial optical cavity length of the first fiber Fabry-Perot interferometer cavity is not equal to that of the second fiber Fabry-Perot interferometer cavity, and their respective values ​​range from 100 micrometers to 600 micrometers.

7. The high-sensitivity wind speed sensor according to claim 6, characterized in that, The output spectral range of the broadband light source covers 1250nm to 1650nm.

8. The high-sensitivity wind speed sensor according to claim 7, characterized in that, The broadband light source, the first circulator, the first fiber Fabry-Perot interferometer cavity, the second circulator, the second fiber Fabry-Perot interferometer cavity, and the spectrometer are all connected by single-mode optical fibers and fiber optic connectors.

9. A method for measuring wind speed using a high-sensitivity wind speed sensor according to any one of claims 1-8, characterized in that, Includes the following steps: S1: The first fiber Fabry-Perot interferometer cavity is placed in the wind speed environment to be measured as the sensing cavity, and the second fiber Fabry-Perot interferometer cavity is placed in a constant windless environment as the reference cavity. S2: The broadband light source is turned on. The broadband light emitted by the broadband light source is transmitted to the first fiber Fabry-Perot interferometer cavity through the first circulator. The broadband light incident on the first fiber Fabry-Perot interferometer cavity undergoes the first multi-beam interference and forms the first interference signal. The reflected light of the first interference signal passes through the first circulator and the second circulator in sequence and then enters the second fiber Fabry-Perot interferometer cavity. S3: The broadband light incident on the second fiber Fabry-Perot interferometer cavity undergoes a second multi-beam interference and forms a second interference signal; the reflected light of the second interference signal is transmitted to the spectrometer via the second circulator to form a composite interference spectrum obtained by superimposing the first interference signal and the second interference signal; S4: Monitor the wavelength shift of the composite interference spectrum using a spectrometer and calculate the wind speed value based on the preset calibration relationship.

10. A preparation method, characterized in that, Used to prepare the high-sensitivity wind speed sensor according to any one of claims 1-8.

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