A distributed laser Doppler anemometer and distributed measurement method based on Fizeau interferometry principle

Abstract

The invention discloses a distributed laser Doppler anemometer and a distributed measurement method based on the Fizeau interference principle, wherein: a rotating mechanism drives an optical antenna tube to rotate, and the optical antenna tube is built with an optical antenna for receiving the wind speed Doppler effect, a circulator is arranged in an instrument box, a first port of the circulator is connected to a narrow line width light source through a first optical fiber amplifier, and the narrow line width light source generates pulse light with a base, a second port of the circulator is connected to a stationary end of an optical fiber slip ring in the rotating mechanism, and the sliding end of the optical fiber slip ring is connected to the optical antenna, the invention adopts a light pulse with a base as the emission light, and interferes with the reflected pulse light to form time domain interference fringes that vary with distance, the invention has stable interference, can improve measurement stability, can not only measure the size of the wind speed, but also determine the position of the wind speed, and realizes distributed measurement of the wind speed.

Description

Technical Field

[0001] The invention belongs to the technical field of anemometers, and in particular relates to a distributed laser Doppler anemometer based on the Fizeau interference principle and a distributed measurement method. Background Art

[0002] Wind speed detection has always been a concern in meteorological detection. At present, there are anemometers based on various principles. Anemometers based on wind pressure measurement can measure the wind speed at the location where it is installed.

[0003] However, the movement of the atmosphere is not uniform, that is, the local wind speed is different. Therefore, a method is needed to measure the wind speed at different atmospheric levels or at different distances, that is, to achieve distributed measurement of wind speed.

[0004] An anemometer that can achieve distributed measurement of wind speed should be non-contact, so a mechanical anemometer that uses wind pressure detection, or a thermal anemometer that needs direct contact with wind for heat dissipation, can only detect the wind speed at the probe, but cannot detect the wind speed at a position that the probe cannot reach.

[0005] Although the anemometer based on the principle of coherent Doppler laser interferometry can achieve non-contact measurement and the measurement distance is slightly longer, it still cannot achieve distributed measurement. This is because the atmosphere is a basically transparent medium with very weak backscattered light. The reflected scattered light contains light scattered from different distances or different layer heights. In other words, the light received by the optical antenna in this laser anemometer is the superposition of the returned light from different positions in the atmosphere. It is already an interference signal in itself. Further interference with the local oscillator light is actually multi-signal interference, which is a mixed messy signal. Since the interferometer of this structure cannot distinguish wind speeds from different distances or different layer heights, the measurement has large errors.

[0006] As a basic method of existing distance measurement, laser radar can measure the position of the light reflection point very well. However, laser radar sends out a pulse light signal. When the pulse signal returns from the reflection point, the sent pulse has passed and interference cannot be achieved. Therefore, simple laser radar cannot measure the Doppler frequency shift and thus measure the wind speed.

[0007] In addition, existing laser interferometer anemometers all use the Michelson interferometer principle, see Figure 1 Here, they used a 2x2 coupler as an optical interference element, and needed to separate one path of light from the laser as the local oscillator light. Since this interferometer used two paths of light interference, they experienced different optical paths, so the interference signal was very unstable and required a complex processing circuit.

[0008] Moreover, during the wind measurement process, since the wind direction is not fixed, the Doppler frequency shift is related to the angle between the wind direction and the incident light. If the optical antenna for wind measurement can only point to a fixed direction, it will cause errors caused by the angle. Therefore, a rotatable wind measurement antenna is needed that can emit light pulses from different angles. Summary of the invention

[0009] The object of the present invention is to provide a distributed laser Doppler anemometer and a distributed measurement method based on the Fizeau interferometer principle to solve the above technical problems.

[0010] To achieve the above object, the present invention provides the following technical solution: a distributed laser Doppler anemometer based on the Fizeau interferometer principle, comprising an instrument box, a rotating mechanism and an optical antenna tube arranged on the rotating mechanism, wherein:

[0011] The rotating mechanism drives the optical antenna tube to rotate, and the optical antenna tube has a built-in optical antenna for receiving the wind speed Doppler effect;

[0012] A circulator is arranged in the instrument box, a first port of the circulator is connected to a narrow line width light source through a first optical fiber amplifier, and the narrow line width light source generates pulse light with a base;

[0013] The second port of the circulator is connected to the stationary end of the optical fiber slip ring in the rotating mechanism, and the sliding end of the optical fiber slip ring is connected to the optical antenna;

[0014] The third port of the circulator is connected to the photoelectric converter through the second optical fiber amplifier, the photoelectric converter is connected to the data acquisition and processing module, and the data acquisition and processing module includes an offline processing module and / or an online processing module.

[0015] Preferably, the optical antenna comprises a self-focusing lens with a pigtail and a beam expanding lens, and the self-focusing lens has the characteristics of partially reflecting and partially transmitting light.

[0016] Preferably, the narrow linewidth light source is a DFB distributed feedback laser, and the pulse light with a base is obtained by changing the DC operating point and the magnitude of the modulation current of the narrow linewidth light source.

[0017] Preferably, the narrow linewidth light source includes a narrow linewidth laser, an optical modulator is arranged behind the narrow linewidth laser, and pulse light with a base is obtained by changing the bias voltage of the optical modulator and the amplitude of the modulation pulse signal.

[0018] Preferably, the first optical fiber amplifier is a linear optical amplifier with high power output, and in the process of amplifying the optical pulse with the base, the first optical fiber amplifier amplifies the amplitude of the base and the amplitude of the pulse by the same multiple to ensure that the extinction ratio remains unchanged.

[0019] Preferably, the second optical fiber amplifier is a low-noise linear preamplifier, and the amplification factor of the second optical fiber amplifier for the reflected pulse light and the local base pulse light is the same.

[0020] Preferably, the data acquisition and processing module includes an oscilloscope and a laptop computer or a data acquisition card and a microcomputer.

[0021] Preferably, the rotating mechanism includes an upper joint and a lower joint, and the optical fiber slip ring is arranged in the upper joint and the lower joint, the upper joint and the lower joint are rotationally connected through a rotating connection part, and the rotating connection part is a parent-child buckle structure, which is rotationally connected in a buckle manner. An annular groove is arranged between the upper joint and the lower joint and on one side of the rotating connection part, and a plurality of steel balls for assisting rotation are arranged in the annular groove.

[0022] The present invention also provides a distribution measurement method of a laser Doppler anemometer based on the Fizeau interferometer principle, which specifically comprises the following steps:

[0023] Step 1, emitting periodic pulsed light with a base into the atmosphere through the optical antenna;

[0024] Step 2, the pulsed light with the base is reflected by wind at different heights or distances and forms a Doppler frequency shift;

[0025] Step 3, the reflected light of the object under test with Doppler frequency shift interferes with the base part of the reflected light of the optical antenna to form time domain interference fringes;

[0026] Step 4: The interference fringes are converted into electrical signals by a photoelectric converter and collected by a data acquisition and processing module;

[0027] Step 5: The data acquisition processing module processes the collected data and obtains a periodic signal reflecting the Doppler frequency shift, and obtains the magnitude of the Doppler frequency shift by counting the periodic signal;

[0028] Step 6: Use the arrival time of the reflected light from the object to be measured as the horizontal coordinate and the size of the Doppler frequency shift as the vertical coordinate, and draw a distance-wind speed distribution curve to achieve distributed measurement of wind speed.

[0029] Technical effects and advantages of the present invention: The distributed laser Doppler anemometer and distributed measurement method based on the Fizeau interferometer principle:

[0030] 1. The present invention measures wind speed by emitting pulsed light and calculates the position of the measured point by calculating the round-trip time of the light pulse, which can effectively distinguish reflected light from different positions;

[0031] 2. The present invention adopts a light pulse with a base as the detection light, so that the pulse light with the base will produce Mie scattering and reflection when reaching different distances in the atmosphere, and the position of the reflected pulse and the size of the wind speed can be obtained, thereby realizing distributed measurement;

[0032] 3. By adopting the Fizeau interference principle, the interference between the two beams of pulse light with a base can be used to make the optical paths of the pulse light with a base the same, the interference is stable, and no other stabilization measures are needed;

[0033] 4. The present invention can reduce the error introduced by the angle between wind speed and incident light by adopting a rotating mechanism, so that the direction of the optical antenna output light is consistent with the direction of wind speed. In order to achieve a stable connection of the rotating mechanism, a fiber optic slip ring is arranged in the rotating mechanism so that the rotating mechanism can still maintain a good optical connection during the rotation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of an existing Doppler laser anemometer;

[0035] Figure 2 is a schematic diagram of the Fizeau interferometer of the present invention;

[0036] Figure 3 Schematic diagram of the pulse shape structure output by the narrow linewidth light source of the present invention (t is the time axis, P is the optical power axis);

[0037] Figure 4 An interference pattern of the present invention;

[0038] Figure 5 It is a structural schematic diagram of the present invention;

[0039] Figure 6 It is a schematic diagram of the internal structure of the rotating mechanism of the present invention.

[0040] In the figure: 1. rotating mechanism; 2. optical antenna pipe; 3. optical antenna; 4. instrument box; 5. circulator; 6. first optical fiber amplifier; 7. narrow line width light source; 8. optical fiber slip ring; 9. second optical fiber amplifier; 10. photoelectric converter; 11. data acquisition and processing module; 12. upper joint; 13. lower joint; 14. rotating connection; 15. annular groove; 16. steel ball. DETAILED DESCRIPTION

[0041] The following will be combined with the attached embodiment of the present invention Figure 1-6, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The present invention provides Figure 1-6 A distributed laser Doppler anemometer based on the Fizeau interferometer principle shown in the figure comprises an instrument box 4, a rotating mechanism 1 and an optical antenna tube 2 arranged on the rotating mechanism 1, wherein:

[0043] The rotating mechanism 1 drives the optical antenna tube 2 to rotate, and the optical antenna tube 2 has a built-in optical antenna 3 for receiving the wind speed Doppler effect. The optical antenna 3 emits periodic pulsed light with a base into the atmosphere. The pulsed light with the base is reflected by wind at different heights or distances to form a Doppler frequency shift.

[0044] By arranging the antenna tube on the rotating mechanism 1, the rotating mechanism 1 drives the optical antenna 3 to rotate freely within a large angle range, so that the direction of the emitted light from the optical antenna 3 is consistent with the wind speed direction.

[0045] A circulator 5 , a narrow linewidth light source 7 , a first optical fiber amplifier 6 , a second optical fiber amplifier 9 and a photoelectric converter 10 are arranged in the instrument box 4 .

[0046] The first port of the circulator 5 is connected to the narrow linewidth light source 7 through the first optical fiber amplifier 6, and the narrow linewidth light source 7 generates a pulse light with a base. By using the pulse light with a base as the detection light, the detection light is neither a constant amplitude continuous light nor a single pulse light. The pulse light with a base will produce Mie scattering when it reaches different distances in the atmosphere, and the pulse part of the pulse light with a base has a larger reflection, while the base part has a smaller reflection, so it can be regarded as a single pulse return, and the reflected light of the object to be measured from different positions can interfere with the base part of the reflected light of the optical antenna 3 when reaching the optical antenna 3 and form time domain interference fringes. Since the base part of the reflected light of the optical antenna 3 is very weak, and the reflected light of the object to be measured reflected back from the atmosphere is also very weak, the two can achieve good interference. In this way, according to the change of the interference signal between the reflected pulse light and the once reflected base light over time, the position of the reflected pulse and the size of the wind speed are obtained, thereby realizing distributed measurement.

[0047] Since reflected pulses from different positions in the atmosphere have a certain time delay, the present invention adopts a method of measuring wind speed by emitting pulsed light with a base, calculates the position of the measured point by calculating the round-trip time of the light pulse, and effectively distinguishes reflected light from different positions.

[0048] The second port of the circulator 5 is connected to the stationary end of the optical fiber slip ring 8 in the rotating mechanism 1 through an optical fiber, and the sliding end of the optical fiber slip ring 8 is connected to the optical antenna 3. The optical fiber slip ring 8 is a special structure optical fiber connector including a rotatable joint and a stationary joint, which can ensure that when the rotating end joint rotates, the optical fiber slip ring 8 body and the stationary end joint still maintain a good optical connection.

[0049] The third port of the circulator 5 is connected to the photoelectric converter 10 through the second optical fiber amplifier 9. The photoelectric converter 10 is connected to the data acquisition and processing module 11. The data acquisition and processing module 11 includes an offline processing module and / or an online processing module.

[0050] Specifically, the optical antenna 3 includes a self-focusing lens with a pigtail and a beam expanding lens. The self-focusing lens has the characteristics of partially reflecting and partially transmitting light. It is used to emit pulsed light with a base into the atmosphere and receive light reflected from the atmosphere. The pigtail of the self-focusing lens can be connected through a multimode-single-mode fiber optic converter (MM converter).

[0051] Specifically, the narrow linewidth light source 7 is a DFB distributed feedback laser, and by changing the DC operating point and the modulation current of the narrow linewidth light source 7, pulse light with a base is obtained. The modulation circuit of the narrow linewidth light source 7 can be synthesized by a pulse circuit and a DC circuit.

[0052] Specifically, the narrow linewidth light source 7 includes a narrow linewidth laser, and an optical modulator is arranged behind the narrow linewidth laser. By changing the bias voltage of the optical modulator and the amplitude of the modulated pulse signal, pulse light with a base is obtained.

[0053] Specifically, the first optical fiber amplifier 6 is a linear optical amplifier with high power output. The ordinary optical fiber amplifier is a gain saturation amplifier, which has a large amplification factor for small signals and a small amplification factor for large signals. Therefore, after the optical pulse with the base passes through this amplifier, its extinction ratio will become smaller. The first optical fiber amplifier 6 uses a linear optical amplifier with high power output to ensure that the amplitude of the base and the amplitude of the pulse are amplified by the same multiple during the process of amplifying the optical pulse with the base, so as to ensure that the extinction ratio remains unchanged.

[0054] Specifically, the second optical fiber amplifier 9 is a low-noise linear preamplifier, and the second optical fiber amplifier 9 has the same amplification factor for the pulse light reflected from the wind and the pulse light of the local base, ensuring that the ratio of the original signal to noise remains unchanged during the amplification process and the additional noise introduced is small.

[0055] Specifically, the data acquisition and processing module 11 includes an oscilloscope and a laptop computer or a data acquisition card and a microcomputer.

[0056] Specifically, the rotating mechanism 1 includes an upper joint 12 and a lower joint 13, and the optical fiber slip ring 8 is arranged in the upper joint 12 and the lower joint 13, the stationary end of the optical fiber slip ring 8 is arranged on the lower joint, and the sliding end of the optical fiber slip ring 8 is arranged in the upper joint 12, the upper joint 12 and the lower joint 13 are rotationally connected through a rotating connection part 14, and the rotating connection part 14 is a parent-child buckle structure, which is rotationally connected in a buckle manner, and an annular groove 15 is provided between the upper joint 12 and the lower joint 13 and on one side of the rotating connection part 14, and a plurality of steel balls 16 for assisting rotation are provided in the annular groove 15.

[0057] In the present invention, the rotation of the rotating mechanism 1 can be performed manually or automatically under the control of an automated control system. When it is performed automatically under the control of an automated control system, the rotating mechanism 1 should also include a driving motor. A driving gear can be fixedly provided on the output end of the driving motor. A driven gear is fixedly provided on the circumference of the upper joint 12. The driven gear is meshed with the driving gear. The driving motor can be controlled by an automated control system. The detection of wind speeds in different directions can be achieved through manual or automated control systems, which makes it more convenient and flexible to use.

[0058] The present invention also provides a distribution measurement method of a laser Doppler anemometer based on the Fizeau interferometer principle, which is characterized by comprising the following steps:

[0059] Step 1, emitting periodic pulsed light with a base into the atmosphere through the optical antenna 3;

[0060] Step 2: The pulsed light with the base is reflected by wind at different heights or distances and forms a Doppler frequency shift;

[0061] Step 3, the reflected light of the object under test with Doppler frequency shift interferes with the base part of the reflected light of the optical antenna 3 and forms time domain interference fringes. The reflected light of the object under test is the Mie scattered light of the atmosphere. Since the optical antenna 3 has the characteristics of partially reflecting and partially transmitting light, the reflected light of the optical antenna 3 is the partial reflected light of the optical antenna 3.

[0062] Step 4: The interference fringes are converted into electrical signals by the photoelectric converter 10 and collected by the data acquisition and processing module 11;

[0063] Step 5: The microcomputer in the data acquisition and processing module 11 performs averaging, high-frequency filtering and denoising operations on the collected data to obtain a periodic signal reflecting the Doppler frequency shift, and then obtains the size of the Doppler frequency shift by counting the periodic signals;

[0064] Step 6: Use the arrival time of the reflected light from the object to be measured as the horizontal coordinate and the size of the Doppler frequency shift as the vertical coordinate, and draw a distance-wind speed distribution curve to achieve distributed measurement of wind speed.

[0065] The Fizeau interferometer-based laser Doppler anemometer of the present invention has a simple structure and can automatically adjust according to the wind direction through the rotatable optical antenna 3 to measure wind speeds in different directions, thereby improving measurement accuracy and reducing measurement errors caused by wind direction problems.

[0066] The present invention adopts a light pulse with a base as the emission light, and interferes with the reflected pulse light to form time-domain interference fringes that vary with distance. The interference of the present invention is stable, which can improve the measurement stability. Not only can the size of the wind speed be measured, but also the position of the wind speed can be determined, thereby realizing the measurement of distributed wind speed.

[0067] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A distributed laser Doppler anemometer based on the Fizeau interferometer principle, comprising an instrument box (4), a rotating mechanism (1) and an optical antenna tube (2) arranged on the rotating mechanism (1), characterized in that: The rotating mechanism (1) drives the optical antenna tube (2) to rotate, and the optical antenna tube (2) has a built-in optical antenna (3) for receiving the wind speed Doppler effect; A circulator (5) is arranged in the instrument box (4), a first port of the circulator (5) is connected to a narrow line width light source (7) via a first optical fiber amplifier (6), and the narrow line width light source (7) generates pulse light with a base; The second port of the circulator (5) is connected to the stationary end of the optical fiber slip ring (8) in the rotating mechanism (1), and the sliding end of the optical fiber slip ring (8) is connected to the optical antenna (3); The third port of the circulator (5) is connected to a photoelectric converter (10) via a second optical fiber amplifier (9), and the photoelectric converter (10) is connected to a data acquisition and processing module (11).

2. A distributed laser Doppler anemometer based on the Fizeau interferometer principle according to claim 1, characterized in that: The optical antenna (3) comprises a self-focusing lens with a pigtail and a beam expanding lens, and the self-focusing lens has the characteristics of partially reflecting and partially transmitting light.

3. The distributed laser Doppler anemometer based on the Fizeau interferometer principle according to claim 1, characterized in that: The narrow line width light source (7) is a DFB distributed feedback laser, and pulse light with a base is obtained by changing the DC working point and the magnitude of the modulation current of the narrow line width light source (7).

4. The distributed laser Doppler anemometer based on the Fizeau interferometer principle according to claim 1, characterized in that: The narrow linewidth light source (7) comprises a narrow linewidth laser, an optical modulator is arranged behind the narrow linewidth laser, and pulse light with a base is obtained by changing the bias voltage of the optical modulator and the amplitude of the modulated pulse signal.

5. The distributed laser Doppler anemometer based on the Fizeau interferometer principle according to claim 1, characterized in that: The first optical fiber amplifier (6) is a linear optical amplifier with high power output, and in the process of amplifying the optical pulse with the base, the first optical fiber amplifier (6) amplifies the amplitude of the base and the amplitude of the pulse by the same multiple to ensure that the extinction ratio remains unchanged.

6. The distributed laser Doppler anemometer based on the Fizeau interferometer principle according to claim 1, characterized in that: The second optical fiber amplifier (9) is a low-noise linear preamplifier, and the amplification factor of the second optical fiber amplifier (9) for the reflected pulse light and the local base pulse light is the same.

7. The distributed laser Doppler anemometer based on the Fizeau interferometer principle according to claim 1, characterized in that: The data acquisition and processing module (11) comprises an oscilloscope and a notebook computer or a data acquisition card and a microcomputer.

8. The distributed laser Doppler anemometer based on the Fizeau interferometer principle according to claim 1, characterized in that: The rotating mechanism (1) comprises an upper joint (12) and a lower joint (13), and the optical fiber slip ring (8) is arranged in the upper joint (12) and the lower joint (13); The upper joint (12) and the lower joint (13) are rotatably connected via a rotatable connection portion (14), and the rotatable connection portion (14) is a parent-child buckle structure, and is rotatably connected in a buckle manner; An annular groove (15) is provided between the upper joint (12) and the lower joint (13) and on one side of the rotary connection part (14), and a plurality of steel balls (16) for assisting rotation are provided in the annular groove (15).

9. The distribution measurement method of the laser Doppler anemometer based on the Fizeau interferometer principle according to claim 1, characterized in that: The specific steps include: Step 1, emitting periodic pulsed light with a base into the atmosphere through the optical antenna (3); Step 2, the pulsed light with the base is reflected by wind at different heights or distances and forms a Doppler frequency shift; Step 3, the reflected light of the object under test with Doppler frequency shift interferes with the base part of the reflected light of the optical antenna (3) to form time domain interference fringes; Step 4: The interference fringes are converted into electrical signals by the photoelectric converter (10) and collected by the data collection and processing module (11); Step 5: the data acquisition and processing module (11) processes the acquired data and obtains a periodic signal reflecting the Doppler frequency shift, and obtains the magnitude of the Doppler frequency shift by counting the periodic signal; Step 6: Use the arrival time of the reflected light from the object to be measured as the horizontal coordinate and the size of the Doppler frequency shift as the vertical coordinate, and draw a distance-wind speed distribution curve to achieve distributed measurement of wind speed.

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