Wind speed sensor system and method based on fiber grating

Abstract

The present invention relates to a wind speed sensor system and method based on fiber grating, including a pumping light source, a sensing light source, a circulator, a wavelength division multiplexer, a fiber sensing probe and a wavelength demodulation unit, wherein the pumping light source is used to generate pumping light to heat a doped optical fiber with the pumping light, and the sensing light source is used to generate sensing light; the circulator is used to transmit the sensing light and isolate the grating reflection signal; the wavelength division multiplexer is used to multiplex the pumping light and the sensing light into the doped optical fiber; the fiber sensing probe is used to transmit the pumping light to heat the doped optical fiber and sense the wind speed, and reflect the sensing signal and the reference signal; the wavelength demodulator is used to receive the sensing signal and the reference signal, and respectively calculate the center wavelength drift amount affected by the wind speed according to the first center wavelength of the sensing signal and the second center wavelength of the reference signal, and calculate the wind speed of the wind field based on the center wavelength drift amount. The present invention has a simple structure and low manufacturing cost.

Description

Technical Field

[0001] The present invention relates to the technical field of wind speed sensing, and in particular to a wind speed sensor system and method based on fiber grating. Background Art

[0002] Wind speed is a concept that measures the speed of air flow. Wind speed sensing is of great significance in industry, agriculture, disaster warning, transportation and other fields.

[0003] Common anemometers include cup anemometers, acoustic anemometers, and hot-wire anemometers. The cup anemometer is the most common anemometer. The flow of air causes the cup to rotate, and the wind speed is obtained by measuring the angular velocity of the rotation. Although this type of anemometer has a simple structure, it is large in size, has a complex circuit system, and has low accuracy. The principle of the acoustic anemometer is that the speed at which fluids in different states transmit ultrasound is different. When the propagation direction of the ultrasound is consistent with the direction of air flow, the propagation speed of the ultrasound increases, and vice versa. The ultrasonic anemometer has good directionality, but the structure is complex and the cost is high. The hot-wire anemometer is based on the principle of thermal balance. The probe used is a metal wire heated by electric current. The change in wind speed will cause the temperature of the metal wire to change. By measuring the change in temperature, the wind speed can be obtained. On this basis, a hot-wire anemometer based on optical fiber has been developed. The sensing probe of this type of anemometer is an optical fiber with a metal film on the surface. The metal film is heated by a metal electrode, or the metal film is heated by a pump laser by designing a special optical fiber probe structure.

[0004] The existing optical fiber-based hot wire anemometer has the advantages of small size, fast response, and high accuracy. However, due to the presence of electrodes and metal films, the sensor probe has a complex structure and poor stability. It is not suitable for flammable and explosive places, and calibration is required during measurement. Summary of the invention

[0005] In view of this, it is necessary to propose a fiber Bragg grating-based wind speed sensor system and method to solve the problems of complex sensor probe structure, poor stability, unsuitability for flammable and explosive places, and calibration required during measurement in the existing fiber Bragg grating-based wind speed sensing technology.

[0006] In order to solve the above problems, in a first aspect, the present invention provides a wind speed sensor system based on fiber grating, comprising a pump light source, a sensing light source, a circulator, a wavelength division multiplexer, a fiber optic sensing probe and a wavelength demodulation unit.

[0007] A pump light source, used to generate pump light to heat the doped optical fiber using the pump light, wherein the doped optical fiber is placed in the optical fiber sensing probe;

[0008] A sensing light source, used for generating sensing light;

[0009] a circulator for transmitting the sensing light and isolating the grating reflection signal;

[0010] A wavelength division multiplexer, used for multiplexing the pump light and the sensing light into a doped optical fiber;

[0011] A fiber optic sensing probe for transmitting pump light for heating and wind speed sensing of the doped fiber and reflecting sensing and reference signals;

[0012] The wavelength demodulator is used to receive the sensing signal and the reference signal, calculate the center wavelength drift affected by the wind speed according to the first center wavelength of the sensing signal and the second center wavelength of the reference signal, and calculate the wind speed of the wind field based on the center wavelength drift.

[0013] Further, the optical fiber sensing probe comprises a doped optical fiber, a first optical fiber grating, a second optical fiber grating, a ventilation pipe and an air isolation pipe, wherein the first optical fiber grating is placed in the ventilation pipe, and the second optical fiber grating is placed in the air isolation pipe;

[0014] A doped optical fiber, used for absorbing pump light power to achieve self-heating of the optical fiber, and transmitting the sensing signal and the reference signal;

[0015] A first fiber grating is used for wind speed sensing and transmitting the sensing signal;

[0016] A second fiber Bragg grating, used for transmitting the reference signal;

[0017] A ventilation pipe, used for forming air convection, so that the first fiber grating is exposed to the wind field;

[0018] The wind isolation duct is used to isolate the air flow around the second fiber grating so that the second fiber grating is not affected by the wind field.

[0019] Furthermore, the first fiber grating and the second fiber grating are engraved on the doped optical fiber to form an integrated structure;

[0020] Alternatively, the first fiber grating and the second fiber grating are fixed side by side with the doped optical fiber to form a dual-fiber structure.

[0021] The first fiber grating and the second fiber grating are fiber Bragg gratings.

[0022] Furthermore, the central wavelength of the first fiber Bragg grating is 1550 nm and the length is 5 mm, the central wavelength of the second fiber Bragg grating is 1553 nm and the length is 5 mm, and the first fiber Bragg grating is spaced 3 cm from the second fiber Bragg grating.

[0023] Furthermore,

[0024] The absorption coefficient of the doped optical fiber is 0.71 dB / cm, the operating wavelength is 1250-1620 nm, and the length is set to 10 cm;

[0025] The doped optical fiber includes any one of erbium-doped optical fiber, neodymium-doped optical fiber and cobalt-doped optical fiber.

[0026] Furthermore, the ventilation pipe is made of stainless steel, the inner diameter of the ventilation pipe is 3 mm, the outer diameter of the ventilation pipe is 4 mm, and the ventilation pipe is not sealed.

[0027] Furthermore, the air isolation tube is made of polyvinyl chloride material, the inner diameter of the air isolation tube is 0.6 mm, the outer diameter is 1 mm, and the air isolation tube is sealed.

[0028] Furthermore, the power of the pump light source is 1500mw, and the pump light source is a semiconductor laser or a YAG laser;

[0029] The sensing light source is a tunable laser or a solid laser.

[0030] Further, the wavelength demodulator is a spectrometer;

[0031] The spectrometer is specifically used to obtain the spectrum of the sensing signal reflected by the first fiber grating and the spectrum of the reference signal reflected by the second fiber grating.

[0032] In a second aspect, the present invention further provides a wind speed sensing method based on fiber grating, comprising:

[0033] Generate pump light by a pump light source, and transmit the pump light to the doped optical fiber via a wavelength division multiplexer to heat the doped optical fiber;

[0034] Generating sensing light through a sensing light source, and transmitting the sensing light to the doped optical fiber via a circulator and a wavelength division multiplexer, so that the sensing light is transmitted on the doped optical fiber;

[0035] Transmitting a sensing signal through a first fiber grating, wherein the first fiber grating is placed in the ventilation pipe;

[0036] Transmitting a reference signal via a second fiber Bragg grating, wherein the second fiber Bragg grating is placed in the air isolation duct;

[0037] The sensing signal and the reference signal are received by a wavelength demodulator to calculate the center wavelength drift affected by the wind speed according to the first center wavelength of the sensing signal and the second center wavelength of the reference signal, and the wind speed of the wind field is calculated based on the center wavelength drift.

[0038] The beneficial effects of adopting the above embodiment are:

[0039] The present invention generates pump light through a pump light source to realize self-heating of the optical fiber, and the sensing light and the pump light are multiplexed into the doped optical fiber; when the wind speed in the wind field changes, the first fiber grating in the optical fiber sensing probe is placed in the ventilation duct, and the central wavelength of its reflected light drifts, and its reflected light is used as a sensing signal; the second fiber grating is placed in the wind isolation duct, and its reflected light is used as a reference signal, and finally the central wavelength of the sensing signal received by the wavelength demodulator and the reference signal are subtracted, and the magnitude of the central wavelength drift affected by the wind speed can be obtained, thereby indirectly obtaining the magnitude of the wind speed in the wind field. The structure of the system in the present invention is simpler and lower in cost than the existing fiber grating wind speed sensor; and a grating placed in the ventilation duct is used for sensing, and a grating placed in the wind isolation duct is used for reference, which avoids the problem of cross-sensitivity of ambient temperature, and no calibration is required during measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic structural diagram of an embodiment of a wind speed sensor system based on fiber grating provided by the present invention;

[0041] Figure 2 A schematic diagram of the structure of an optical fiber sensing probe provided by one embodiment of the present invention;

[0042] Figure 3 A schematic flow chart of an embodiment of a wind speed sensing method based on fiber grating provided by the present invention. DETAILED DESCRIPTION

[0043] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0044] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. Reference to "embodiments" in this article means that the specific features, structures or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0045] The present invention provides a wind speed sensing system and method based on fiber grating, which utilizes the thermal effect of doped optical fiber and uses a pump laser to heat the grating. The heated grating will produce different degrees of heat loss under different wind speeds, thereby affecting the center position of the grating's reflection wavelength. The wind speed is indirectly measured by measuring the drift of the center wavelength of the grating's reflection spectrum.

[0046] The specific embodiments are described in detail below:

[0047] See also Figure 1 , Figure 1 The present invention provides a schematic structural diagram of an embodiment of a wind speed sensor system based on a fiber Bragg grating, comprising a pump light source 1, a sensing light source 2, a circulator 3, a wavelength division multiplexer 4, a fiber optic sensor probe 5 and a wavelength demodulation unit 6.

[0048] A pump light source, used to generate pump light to heat the doped optical fiber using the pump light, wherein the optical fiber sensing probe includes the doped optical fiber;

[0049] A sensing light source, used for generating sensing light;

[0050] a circulator for transmitting the sensing light and isolating the grating reflection signal;

[0051] A wavelength division multiplexer, used for multiplexing the pump light and the sensing light into a doped optical fiber;

[0052] A fiber optic sensing probe for transmitting pump light for heating and wind speed sensing of the doped fiber and reflecting sensing and reference signals;

[0053] The wavelength demodulator is used to receive the sensing signal and the reference signal, calculate the center wavelength drift affected by the wind speed according to the first center wavelength of the sensing signal and the second center wavelength of the reference signal, and calculate the wind speed of the wind field based on the center wavelength drift.

[0054] It can be understood that the pump light source emits pump light through the wavelength division multiplexer to the doped optical fiber, and the doped optical fiber absorbs the energy of the pump light and converts the light energy into heat energy to achieve self-heating of the optical fiber; the sensing light source emits sensing light through the circulator and the wavelength division multiplexer to the doped optical fiber; when the wind speed in the wind farm changes, the doped optical fiber is heated and the wind speed is sensed, and the reflected signal is used as the reflected sensing signal and the reflected reference signal; the sensing signal and the reference signal are transmitted to the wavelength demodulator through the wavelength division multiplexer and the circulator; finally, the central wavelength of the sensing signal received by the wavelength demodulator is subtracted from the central wavelength of the reference signal, and the magnitude of the central wavelength drift affected by the wind speed can be obtained, thereby indirectly obtaining the magnitude of the wind speed in the wind farm.

[0055] The present invention generates pump light through a pump light source to realize self-heating of the optical fiber, and the sensing light and the pump light are multiplexed into the doped optical fiber; when the wind speed in the wind field changes, the first fiber grating in the optical fiber sensing probe is placed in the ventilation duct, and the central wavelength of its reflected light drifts, and its reflected light is used as a sensing signal; the second fiber grating is placed in the wind isolation duct, and its reflected light is used as a reference signal, and finally the central wavelength of the sensing signal received by the wavelength demodulator and the reference signal are subtracted, and the magnitude of the central wavelength drift affected by the wind speed can be obtained, thereby indirectly obtaining the magnitude of the wind speed in the wind field. The structure of the system in the present invention is simpler and lower in cost than the existing fiber grating wind speed sensor; and a grating placed in the ventilation duct is used for sensing, and a grating placed in the wind isolation duct is used for reference, which avoids the problem of cross-sensitivity of ambient temperature, and no calibration is required during measurement.

[0056] In one embodiment of the present invention, see Figure 2 , Figure 2 A schematic diagram of the structure of a fiber optic sensing probe provided in one embodiment of the present invention, wherein the fiber optic sensing probe 5 comprises a doped optical fiber 51, a first fiber optic grating 52, a second fiber optic grating 53, a ventilation pipe 54 and an air isolation pipe 55, wherein the first fiber optic grating is placed in the ventilation pipe, and the second fiber optic grating is placed in the air isolation pipe;

[0057] A doped optical fiber, used for absorbing pump light power to achieve self-heating of the optical fiber, and transmitting the sensing signal and the reference signal;

[0058] A first fiber grating is used for wind speed sensing and transmitting the sensing signal;

[0059] A second fiber Bragg grating, used for transmitting the reference signal;

[0060] A ventilation pipe, used for forming air convection, so that the first fiber grating is exposed to the wind field;

[0061] The wind isolation duct is used to isolate the air flow around the second fiber grating so that the second fiber grating is not affected by the wind field.

[0062] It can be understood that when the first fiber grating is placed in the ventilation duct, it will be affected by the wind field and will suffer heat loss, then the central wavelength of its reflected light will drift, and there will be different heat losses and drift amounts under different wind speeds, and its reflected light will be used as a sensing signal; when the second fiber grating is placed in the wind isolation duct, it will not be affected by changes in wind speed in the wind field, and its reflected light will be used as a reference signal; the sensing signal reflected by the first fiber grating and the reference signal reflected by the second fiber grating.

[0063] It can be seen that the fiber Bragg grating wind speed sensor proposed by the present invention is composed of only one doped optical fiber, two gratings, a ventilation pipe and an air isolation pipe. Its structure is simpler and the cost is lower than that of the existing fiber Bragg grating wind speed sensor. Compared with the traditional fiber Bragg grating sensor, it does not have a metal film and an electrode, so it is more corrosion-resistant, more stable and also suitable for flammable and explosive places. In addition, a grating placed in the ventilation pipe is used for sensing, and a grating placed in the air isolation pipe is used for reference, which avoids the problem of cross-sensitivity of ambient temperature, and no calibration is required during measurement.

[0064] In one embodiment of the present invention, the first fiber grating and the second fiber grating are written on the doped optical fiber to form an integrated structure;

[0065] Alternatively, the first fiber grating and the second fiber grating are fixed side by side with the doped optical fiber to form a dual-fiber structure.

[0066] The first fiber grating and the second fiber grating are fiber Bragg gratings.

[0067] It can be understood that the first fiber grating and the second fiber grating can be directly engraved on the doped optical fiber to form an integrated structure, or the first fiber grating and the second fiber grating can be fixed side by side with the doped optical fiber to form a dual-fiber structure. More specifically, the first fiber grating and the second fiber grating are fiber Bragg gratings.

[0068] In one embodiment of the present invention, the central wavelength of the first fiber Bragg grating is 1550 nm and the length is 5 mm, the central wavelength of the second fiber Bragg grating is 1553 nm and the length is 5 mm, and the first fiber Bragg grating is spaced 3 cm from the second fiber Bragg grating.

[0069] In one embodiment of the present invention,

[0070] The absorption coefficient of the doped optical fiber is 0.71 dB / cm, the operating wavelength is 1250-1620 nm, and the length is set to 10 cm;

[0071] The doped optical fiber includes any one of erbium-doped optical fiber, neodymium-doped optical fiber and cobalt-doped optical fiber.

[0072] It can be understood that the doped optical fiber is used to absorb the pump light power to achieve self-heating of the optical fiber and transmit the sensing signal and the reference signal; specifically, the absorption coefficient of the doped optical fiber is 0.71dB / cm, and the absorption coefficient is relatively large, so that the temperature rise of the optical fiber is high enough after absorbing the power of the pump light; the working wavelength is 1250-1620nm, and the length is set to 10cm.

[0073] In one embodiment of the present invention, the ventilation pipe is made of stainless steel, the inner diameter of the ventilation pipe is 3 mm, the outer diameter of the ventilation pipe is 4 mm, and the ventilation pipe is not sealed.

[0074] In one embodiment of the present invention, the air isolation tube is made of polyvinyl chloride material, the inner diameter of the air isolation tube is 0.6 mm, the outer diameter is 1 mm, and the air isolation tube is sealed.

[0075] It is understandable that the ventilation pipe is used to form air convection, so that the first fiber Bragg grating is exposed to the wind field, and the ventilation pipe is a hollow cylinder with a diameter larger than the diameter of the optical fiber, and is not sealed so that air convection can be formed. The material can be stainless steel, copper, etc. Specifically, the inner diameter of the ventilation pipe is 3 mm and the outer diameter is 4 mm.

[0076] The wind-shielding tube is used to isolate the air flow around the second fiber Bragg grating so that it is not affected by the wind field. The wind-shielding tube is a hollow cylinder with a diameter greater than the diameter of the optical fiber and a certain thickness. It is sealed to isolate the air flow. The material can be polyvinyl chloride, quartz glass, etc. Specifically, the inner diameter of the wind-shielding tube is 0.6 mm and the outer diameter is 1 mm.

[0077] In one embodiment of the present invention, the power of the pump light source is 1500mw, and the pump light source is a semiconductor laser or a YAG laser; the sensing light source is a tunable laser or a solid laser; the wavelength demodulator is a spectrometer, and the spectrometer is specifically used to obtain the spectrum of the sensing signal reflected by the first fiber grating and the spectrum of the reference signal reflected by the second fiber grating.

[0078] It is understandable that the pump light source is used to provide excitation power for the doped optical fiber, and can be a semiconductor laser, a YAG laser, etc., and the present invention does not impose further restrictions on this, and the power of the pump light source is set to 1500mw. Too low power will result in little change in the temperature of the optical fiber and respond to the temperature measurement sensitivity. The sensing light source is used to emit an optical signal for sensing, wherein the sensing light source is a continuous light source, and can be a semiconductor laser, a solid laser, etc. The wavelength demodulator, i.e., the spectrometer, is used to obtain the spectrum of the sensing signal reflected by the first fiber Bragg grating and the spectrum of the reference signal reflected by the second fiber Bragg grating.

[0079] In order to better implement the wind speed sensing system based on fiber Bragg grating in the embodiment of the present invention, on the basis of the wind speed sensing system based on fiber Bragg grating, correspondingly, please refer to Figure 3 , Figure 3 The present invention provides a wind speed sensing method based on fiber gratings, which includes:

[0080] Step S301: Generate pump light through a pump light source, and the pump light is transmitted to the doped optical fiber through a wavelength division multiplexer to heat the doped optical fiber;

[0081] Step S302: generating sensing light through a sensing light source, and transmitting the sensing light to the doped optical fiber via a circulator and a wavelength division multiplexer, so that the sensing light is transmitted on the doped optical fiber;

[0082] Step S303: transmitting a sensing signal through a first fiber grating, wherein the first fiber grating is placed in the ventilation pipe;

[0083] Step S304: transmitting a reference signal through a second fiber Bragg grating, wherein the second fiber Bragg grating is placed in the air isolation duct;

[0084] Step S305: receiving the sensing signal and the reference signal through a wavelength demodulator, calculating the center wavelength drift affected by the wind speed according to the first center wavelength of the sensing signal and the second center wavelength of the reference signal, and calculating the wind speed of the wind field based on the center wavelength drift.

[0085] It can be understood that the pump light source emits pump light through a wavelength division multiplexer to the doped optical fiber, and the doped optical fiber absorbs the energy of the pump light and converts the light energy into heat energy to achieve self-heating of the optical fiber; the sensing light source emits sensing light through a circulator and a wavelength division multiplexer to the doped optical fiber; when the wind speed in the wind field changes, the first fiber grating is placed in the ventilation duct, which will be affected by the wind field and will suffer heat loss, and the central wavelength of its reflected light will drift, with different heat losses and drift amounts at different wind speeds, and its reflected light is used as a sensing signal; the second fiber grating is placed in the wind isolation duct and is not affected by changes in wind speed in the wind field, and its reflected light is used as a reference signal; the sensing signal and the reference signal are transmitted to a wavelength demodulator via a wavelength division multiplexer and a circulator; finally, the central wavelength of the sensing signal received by the wavelength demodulator and the reference signal are subtracted to obtain the amount of central wavelength drift affected by the wind speed, and thus the wind speed in the wind field can be indirectly obtained.

[0086] It can be seen that the fiber Bragg grating wind speed sensor proposed by the present invention is composed of only one doped optical fiber, two gratings, a ventilation pipe and an air isolation pipe. Its structure is simpler and the cost is lower than that of the existing fiber Bragg grating wind speed sensor. Compared with the traditional fiber Bragg grating sensor, it does not have a metal film and an electrode, so it is more corrosion-resistant, more stable and also suitable for flammable and explosive places. In addition, a grating placed in the ventilation pipe is used for sensing, and a grating placed in the air isolation pipe is used for reference, which avoids the problem of cross-sensitivity of ambient temperature, and no calibration is required during measurement.

[0087] It should be noted here that the fiber Bragg grating-based wind speed sensing method provided in the above embodiment can implement the technical solutions described in the above system embodiments, which will not be described in detail here.

[0088] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0089] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A wind speed sensor system based on fiber Bragg grating, comprising a pump light source, a sensing light source, a circulator, a wavelength division multiplexer, a fiber sensing probe and a wavelength demodulation unit, characterized in that: A pump light source, used to generate pump light to heat the doped optical fiber using the pump light, wherein the optical fiber sensing probe includes the doped optical fiber; A sensing light source, used for generating sensing light; a circulator for transmitting the sensing light and isolating the grating reflection signal; A wavelength division multiplexer, used for multiplexing the pump light and the sensing light into a doped optical fiber; A fiber optic sensing probe for transmitting pump light for heating and wind speed sensing of the doped fiber and reflecting sensing and reference signals; The optical fiber sensing probe comprises a doped optical fiber, a first optical fiber grating, a second optical fiber grating, a ventilation pipe and an air isolation pipe, wherein the first optical fiber grating is placed in the ventilation pipe, and the second optical fiber grating is placed in the air isolation pipe; A doped optical fiber, used for absorbing pump light power to achieve self-heating of the optical fiber, and transmitting the sensing signal and the reference signal; A first fiber grating is used for wind speed sensing and transmitting the sensing signal; A second fiber Bragg grating, used for transmitting the reference signal; A ventilation pipe, used for forming air convection, so that the first fiber grating is exposed to the wind field; An air isolation duct, used to isolate the air flow around the second fiber grating, so that the second fiber grating is not affected by the wind field; The wavelength demodulator is used to receive the sensing signal and the reference signal, calculate the center wavelength drift affected by the wind speed according to the first center wavelength of the sensing signal and the second center wavelength of the reference signal, and calculate the wind speed of the wind field based on the center wavelength drift.

2. The fiber grating based wind speed sensor system according to claim 1, characterized in that: The first fiber grating and the second fiber grating are written on the doped optical fiber to form an integrated structure; Or, the first fiber grating and the second fiber grating are fixed side by side with the doped optical fiber to form a dual optical fiber structure; The first fiber grating and the second fiber grating are fiber Bragg gratings.

3. The fiber Bragg grating-based wind speed sensor system according to claim 1, characterized in that: The central wavelength of the first fiber Bragg grating is 1550 nm and the length is 5 mm. The central wavelength of the second fiber Bragg grating is 1553 nm and the length is 5 mm. The first fiber Bragg grating is spaced 3 cm from the second fiber Bragg grating.

4. The fiber Bragg grating-based wind speed sensor system according to claim 1, characterized in that: The absorption coefficient of the doped optical fiber is 0.71 dB / cm, the operating wavelength is 1250-1620 nm, and the length is set to 10 cm; The doped optical fiber includes any one of erbium-doped optical fiber, neodymium-doped optical fiber and cobalt-doped optical fiber.

5. The fiber Bragg grating-based wind speed sensor system according to claim 1, characterized in that: The ventilation pipe is made of stainless steel, the inner diameter of the ventilation pipe is 3 mm, the outer diameter of the ventilation pipe is 4 mm, and the ventilation pipe is not sealed.

6. The fiber Bragg grating-based wind speed sensor system according to claim 1, characterized in that: The air isolation tube is made of polyvinyl chloride material, the inner diameter of the air isolation tube is 0.6 mm, the outer diameter is 1 mm, and the air isolation tube is sealed.

7. The fiber Bragg grating-based wind speed sensor system according to claim 1, characterized in that: The power of the pump light source is 1500mw, and the pump light source is a semiconductor laser or a YAG laser; The sensing light source is a tunable laser or a solid laser.

8. The fiber Bragg grating-based wind speed sensor system according to claim 1, characterized in that: The wavelength demodulator is a spectrometer; The spectrometer is specifically used to obtain the spectrum of the sensing signal reflected by the first fiber grating and the spectrum of the reference signal reflected by the second fiber grating.

9. A wind speed sensing method based on fiber Bragg grating, applied to the wind speed sensing system based on fiber Bragg grating as claimed in any one of claims 1 to 8, characterized in that: The method comprises: Generate pump light by a pump light source, and transmit the pump light to the doped optical fiber via a wavelength division multiplexer to heat the doped optical fiber; Generating sensing light through a sensing light source, and transmitting the sensing light to the doped optical fiber via a circulator and a wavelength division multiplexer, so that the sensing light is transmitted on the doped optical fiber; Transmitting a sensing signal through a first fiber grating, wherein the first fiber grating is placed in the ventilation pipe; Transmitting a reference signal via a second fiber Bragg grating, wherein the second fiber Bragg grating is placed in the air isolation duct; The sensing signal and the reference signal are received by a wavelength demodulator to calculate the center wavelength drift affected by the wind speed according to the first center wavelength of the sensing signal and the second center wavelength of the reference signal, and the wind speed of the wind field is calculated based on the center wavelength drift.

Images