CN109959944B - Wind lidar based on wide-spectrum light source - Google Patents
Wind lidar based on wide-spectrum light source Download PDFInfo
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- CN109959944B CN109959944B CN201910256086.7A CN201910256086A CN109959944B CN 109959944 B CN109959944 B CN 109959944B CN 201910256086 A CN201910256086 A CN 201910256086A CN 109959944 B CN109959944 B CN 109959944B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/26—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the direct influence of the streaming fluid on the properties of a detecting optical wave
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
- G01S17/95—Lidar systems specially adapted for specific applications for meteorological use
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4816—Constructional features, e.g. arrangements of optical elements of receivers alone
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4818—Constructional features, e.g. arrangements of optical elements using optical fibres
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The invention discloses a wind lidar based on a wide-spectrum light source. The invention adopts the optical switch gating to enable the transmitting laser and the atmosphere echo signal to share one filter, thereby realizing the direct detection wind-measuring laser radar based on a wide-spectrum light source. The invention proposes to use a frequency shifter to shift the frequency of the emitted laser light onto the edges of the filter. When the atmospheric echo signal is subjected to Doppler frequency shift, the intensity change of the transmission signal and the reflection signal of the atmospheric echo signal passing through the filter is caused, one is enhanced, the other is reduced, and the atmospheric wind speed is extracted through the intensity change information. Since the emitted laser and the atmospheric echo signal pass through the filter in the millisecond or even microsecond time, the wind-sensing laser radar has the advantages that firstly, the wind-sensing laser radar is insensitive to the frequency drift of the laser and the filter; secondly, a narrow linewidth single-frequency laser is not needed, the emergent laser power of a broad-spectrum light source can be improved, and the cost of the laser is reduced; finally, no reference laser is needed, simplifying the light path.
Description
Technical Field
The invention relates to the field of laser radars, in particular to a direct detection wind lidar based on a wide-spectrum light source.
Background
In atmospheric wind speed remote sensing, the wind-measuring laser radar has the characteristics of high precision, high space-time resolution and the like, and is widely applied to the fields of atmospheric wind profile detection, wind shear early warning, aircraft wake detection, wind power generation, aerospace, military and the like.
Wind lidar can be classified into direct detection and coherent detection. At present, the light sources of the wind lidar with the two mechanisms adopt lasers with strict requirements and narrow linewidth. The coherent laser radar improves the coherence length by adopting a narrow linewidth, so that the coherence efficiency is improved, and the wider the spectrum is, the worse the coherence efficiency is. In the direct detection wind-finding laser radar, a narrow linewidth laser is locked on the steep edge of a filter, and a weak Doppler frequency shift causes large change of transmission intensity, so that wind speed information is extracted, and the detection sensitivity is higher when the laser spectrum is narrower. In practice, the reference light is used to lock the laser frequency to the filter due to drift between the laser and the filter. This brings about several problems, firstly, when the ambient temperature and pressure changes are large, a large frequency drift of the laser and the filter will be caused, which increases the difficulty of locking, and also puts a better requirement on the stability of the system, and on the other hand, introduces a systematic error; secondly, in the fiber laser, the narrower the linewidth is, the stronger the stimulated brillouin scattering effect is, so that the output power of the laser is limited, and the cost of the laser is increased.
Disclosure of Invention
In one aspect, the disclosure provides a wind lidar based on a broad spectrum light source, comprising: a seed laser pulse generating unit for generating a seed laser pulse; a filtering unit including a filter for filtering the generated seed laser pulse; a laser frequency shift and amplification unit for receiving the filtered seed laser pulse filtered by the filtering unit and frequency shifting and amplifying the filtered seed laser pulse; a laser light transmitting and receiving unit for receiving the frequency-shifted and amplified laser light frequency-shifted and amplified by the laser light frequency-shifting and amplifying unit and transmitting the frequency-shifted and amplified laser light to the atmosphere; the laser transmitting and receiving unit is also used for receiving an atmosphere echo signal generated after the frequency-shifted and amplified seed laser pulse interacts with the atmosphere; the atmospheric echo signals received by the laser transmitting and receiving unit are filtered by the filter to respectively obtain transmission signals and reflection signals, the transmission signals and the reflection signals are sensitive to atmospheric Doppler frequency shift, and the atmospheric wind speed information can be obtained by inversion through measuring the intensity changes of the transmission signals and the reflection signals.
Optionally, the wind lidar based on the broad spectrum light source further includes: an echo signal detection unit for detecting the transmission signal and the reflection signal; and the signal acquisition and processing unit is used for acquiring the transmission signal and the reflection signal detected by the echo signal detection unit, measuring the intensity changes of the transmission signal and the reflection signal, and inverting to obtain the atmospheric wind speed information.
Optionally, the wind lidar based on a broad spectrum light source, wherein the filtering unit further includes: the first optical switch and the second optical switch enable the seed laser pulse and the atmospheric echo signal to pass through the filter in a time-sharing way through a gating mode of the first optical switch and the second optical switch, wherein the first optical switch is connected with the seed laser pulse generating unit, and the second optical switch is connected with the laser frequency shifting and amplifying unit and the echo signal detecting unit.
Optionally, in the wind-measuring laser radar based on the broad spectrum light source, the seed laser pulse is incident to the filter after passing through the first optical channel of the first optical switch, the filter filters the seed laser pulse to obtain the filtered seed laser pulse, and the filtered seed laser pulse is incident to the first optical channel of the second optical switch and is further input to the laser frequency shift and amplification unit.
Optionally, the filtering unit further includes: the circulator is connected with the laser transmitting and receiving unit and the echo signal detecting unit, wherein the atmospheric echo signal received by the laser transmitting and receiving unit passes through the circulator, enters the filter through the second optical channel of the first optical switch, and is filtered by the filter to obtain a transmission signal and a reflection signal respectively; the transmission signal enters the echo signal detection unit after passing through a second optical channel of the second optical switch; the reflected signal enters the echo signal detection unit after passing through the second optical channel of the first optical switch and the circulator.
Optionally, the seed laser pulse generating unit includes: a seed laser for generating a seed laser; the pulse generator is connected with the seed laser and used for receiving the seed laser and generating pulse laser based on the seed laser; and the first filter is connected with the pulse generator and filters the pulse laser to form the seed laser pulse.
Optionally, the filter includes a second filter and a third filter, where the second filter and the third filter are connected.
Optionally, the laser frequency shift and amplification unit includes: the laser frequency shifter is connected with the filtering unit and is used for receiving the filtered seed laser pulse from the filtering unit and shifting the frequency of the filtered seed laser pulse; the delay optical fiber is connected with the laser frequency shifter and is used for receiving the frequency-shifted seed laser pulse from the laser frequency shifter and delaying the frequency-shifted seed laser pulse so as to separate the atmospheric echo signal from the seed laser pulse in a time domain; and the optical fiber amplifier is connected with the delay optical fiber and the laser transmitting and receiving unit and is used for receiving the delayed seed laser pulse from the delay optical fiber, amplifying the delayed seed laser pulse to obtain the frequency-shifted and amplified seed laser pulse, and inputting the frequency-shifted and amplified seed laser pulse into the laser transmitting and receiving unit.
Optionally, the signal acquisition and processing unit includes: the acquisition card is used for acquiring the transmission signal and the reflection signal detected by the echo signal detection unit; and the processor is used for measuring the intensity changes of the transmission signal and the reflection signal acquired by the acquisition card and obtaining the atmospheric wind speed information by inversion.
Optionally, the laser transmitting and receiving unit includes: a transmitting telescope for transmitting the frequency-shifted and amplified seed laser pulses from the laser frequency shifting and amplifying unit into the atmosphere; and the receiving telescope is used for receiving the atmospheric echo signal from the atmosphere and inputting the atmospheric echo signal into the filtering unit.
The direct detection wind-finding laser radar provided by the disclosure adopts a mode of gating an optical switch to achieve a broad spectrum light source of an echo signal, and locks seed laser pulses at the half height of a filter through frequency shift of a laser frequency shifter, so that detection of an atmospheric wind field is achieved. The wind-measuring laser radar disclosed by the publication has the characteristics of high system stability, no need of reference light, insensitivity to laser frequency jitter and high broad-spectrum laser emergent power.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only embodiments of the present disclosure, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
FIG. 1 schematically illustrates a schematic optical path diagram of a lidar according to an embodiment of the disclosure;
FIG. 2 schematically illustrates a timing diagram of operation of a lidar according to an embodiment of the present disclosure; and
fig. 3 schematically illustrates a schematic diagram of a direct detection anemometry principle of a lidar according to an embodiment of the present disclosure.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is only exemplary and is not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the concepts of the present disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "comprises," "comprising," and/or the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It should be noted that the terms used herein should be construed to have meanings consistent with the context of the present specification and should not be construed in an idealized or overly formal manner.
Where expressions like at least one of "A, B and C, etc. are used, the expressions should generally be interpreted in accordance with the meaning as commonly understood by those skilled in the art (e.g.," a system having at least one of A, B and C "shall include, but not be limited to, a system having a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.). Where a formulation similar to at least one of "A, B or C, etc." is used, in general such a formulation should be interpreted in accordance with the ordinary understanding of one skilled in the art (e.g. "a system with at least one of A, B or C" would include but not be limited to systems with a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.).
The following description of the embodiments of the present disclosure, taken in conjunction with the accompanying drawings, will clearly and fully illustrate the technical aspects of the embodiments of the present disclosure, and it will be apparent that the embodiments described are only some, but not all embodiments of the present disclosure. All other embodiments, which are derived by a person of ordinary skill in the art from embodiments of the invention without creative efforts, are within the protection scope of the present disclosure.
Fig. 1 schematically illustrates an optical path schematic diagram of a lidar according to an embodiment of the present disclosure.
As shown in fig. 1, a laser radar according to an embodiment of the present disclosure, in particular, a direct detection wind lidar based on a broad spectrum light source, includes a seed laser pulse generating unit 10, a filtering unit 20, a laser frequency shift and amplification unit 30, a laser transmitting and receiving unit 40, an echo signal detecting unit 50, and a signal collecting and processing unit 60.
According to an embodiment of the present disclosure, the seed laser pulse generating unit 10 is used for generating seed laser pulses. Alternatively, the seed laser pulse generating unit 10 may be another laser capable of generating a broad-spectrum laser pulse.
According to an embodiment of the present disclosure, the seed laser pulse generating unit 10 includes, for example, a seed laser 11, a pulse generator 12, and a first filter 13. The seed laser 11 comprises, for example, a continuous broad spectrum seed laser for generating seed laser light. The pulse generator 12 is connected to the seed laser 11 for receiving the seed laser light and generating a pulse laser light based on the seed laser light. The first filter 13 is connected to the pulse generator 12 and filters the pulse laser light to form seed laser pulses, which are incident to the filtering unit 20.
Specifically, the seed laser 11 first forms pulsed light through the pulse generator 12, and then intercepts the spectrum for detection through the first filter 13. The preferred laser has a center wavelength of 1.5 microns.
According to an embodiment of the present disclosure, the filtering unit 20 includes a filter 21, the filter 21 being configured to filter the generated seed laser pulse.
According to an embodiment of the present disclosure, the filtering unit 20 further includes: the first optical switch 24 and the second optical switch 25 time-share the seed laser pulse and the atmospheric echo signal through the filter 21 by the gating mode of the first optical switch 24 and the second optical switch 25, wherein the first optical switch 24 is connected with the seed laser pulse generating unit 10, and the second optical switch 25 is connected with the laser frequency shift and amplifying unit 30 and the echo signal detecting unit 50.
According to the embodiment of the disclosure, after passing through the first optical channel of the first optical switch 24, the seed laser pulse is incident on the filter 21, the filter 21 filters the seed laser pulse to obtain a filtered seed laser pulse, and the filtered seed laser pulse is incident on the first optical channel of the second optical switch 25 and is further input to the laser frequency shift and amplification unit 30.
In the embodiment of the present disclosure, the filter 21 includes a second filter 22 and a third filter 23, and the second filter 22 and the third filter 23 are connected.
Specifically, the seed laser pulse enters the second filter 22 after passing through the first optical channel of the first optical switch 24 (for example, the 1-2 channels of the first optical switch 24), and then passes through the third filter 23 and the first optical channel of the second optical switch 25 (for example, the 1-2 channels of the second optical switch 25). Wherein the first optical switch 24 and the second optical switch 25 are used for gating the seed laser pulse and the atmospheric echo signal. The second filter 22 is used to filter the atmospheric echo information and to filter out solar background and sky background radiation. The third filter 23 is used as an edge filter for filtering out seed laser pulses and as an atmospheric wind field detection.
According to an embodiment of the present disclosure, the laser frequency shifting and amplifying unit 30 is configured to receive the laser light filtered by the filtering unit 20 and to shift and amplify the filtered laser light. Wherein the laser frequency shift and amplification unit 30 includes: a laser frequency shifter 31, a delay fiber 32, and a fiber amplifier 33.
The laser frequency shifter 31 is connected to the filtering unit 20, and is configured to receive the filtered laser light from the filtering unit 20 and frequency shift the filtered laser light. A delay fiber 32 is connected to the laser frequency shifter 31 for receiving the frequency shifted laser light from the laser frequency shifter 31 and delaying the frequency shifted laser light so as to temporally separate the atmospheric echo signal from the seed laser pulse. The optical fiber amplifier 33 is connected to the delay optical fiber 32 and the laser transmitting and receiving unit 40, and is configured to receive the delayed laser light from the delay optical fiber 32, amplify the delayed laser light to obtain frequency-shifted and amplified laser light, and input the frequency-shifted and amplified laser light to the laser transmitting and receiving unit 40.
The laser emitted from the filter unit 20 passes through the laser frequency shifter 31, and then sequentially passes through the delay fiber 32 and the fiber amplifier 33 for delay and optical amplification. The laser frequency shifter 31 is used for shifting the laser light emitted from the filter unit 20 to the half height of the transmittance curve of the third filter 23. The delay fiber 32 is used to time-domain separate the outgoing laser pulse from the atmospheric echo signal.
According to an embodiment of the present disclosure, the laser transmitting and receiving unit 40 is configured to receive the shifted and amplified laser light shifted and amplified by the laser light shifting and amplifying unit 30 and transmit the shifted and amplified laser light into the atmosphere, and the laser transmitting and receiving unit 40 is further configured to receive an atmospheric echo signal generated after the shifted and amplified laser light interacts with the atmosphere.
The atmospheric echo signal received by the laser transmitting and receiving unit 40 is filtered by the filter 21 to obtain a transmission signal and a reflection signal, which are sensitive to the atmospheric doppler shift, and the atmospheric wind speed information can be obtained by inversion by measuring the intensity changes of the transmission signal and the reflection signal.
Specifically, the laser transmitting and receiving unit 40 includes: a transmitting telescope 41 and a receiving telescope 42. The transmitting telescope 41 is used to transmit the frequency-shifted and amplified laser light from the laser frequency shifting and amplifying unit 30 into the atmosphere. The receiving telescope 42 is used for receiving an atmospheric echo signal from the atmosphere and inputting the atmospheric echo signal to the filtering unit 20.
According to an embodiment of the present disclosure, the laser transmitting and receiving unit 40 transmits the amplified laser pulse to the atmosphere through the transmitting telescope 41, and an atmosphere echo signal generated by the interaction of the laser pulse and the atmosphere is received by the receiving telescope 42. As shown in fig. 1, the laser transmitting and the atmospheric echo signal receiving are of a receiving-transmitting separated structure, which is a preferred scheme, and the laser transmitting and the atmospheric echo signal receiving can also be of a receiving-transmitting coaxial structure, and the transmitting and the receiving share a telescope.
According to an embodiment of the present disclosure, the filtering unit 20 further includes: the circulator 26, the circulator 26 is connected to the laser transmitting and receiving unit 40 and the echo signal detecting unit 50.
The atmospheric echo signal received by the laser transmitting and receiving unit 40 passes through the circulator 26, then enters the filter 21 through the second optical channel of the first optical switch 24, and is filtered by the filter 21 to obtain a transmission signal and a reflection signal, wherein the transmission signal passes through the second optical channel of the second optical switch 25, then enters the echo signal detection unit 50, and the reflection signal passes through the second optical channel of the first optical switch 24 and the circulator 26, then enters the echo signal detection unit 50.
For example, the atmospheric echo signal passes through the circulator 26, passes through the second optical channel of the first optical switch 24 (for example, the 3-2 channel of the first optical switch 24), and then enters the second filter 22 and the third filter 23, wherein the transmission signal passes through the second optical channel of the second optical switch 25 (for example, the 1-4 channel of the second optical switch 25) and enters the echo signal detecting unit 50. The reflected signals of the atmospheric echo signals passing through the third filter 23 enter the echo signal detecting unit 50 after passing through the second filter 22 and the second optical channel of the first optical switch 24 (for example, the 2-3 channels of the first optical switch 24).
According to an embodiment of the present disclosure, the echo signal detection unit 50 is used to detect transmission signals and reflection signals.
The echo signal detection unit 50 is a single photon detector, including but not limited to a superconducting nanowire single photon detector, a frequency up-conversion single photon detector, and an InGaAs (indium gallium arsenide) single photon detector.
Specifically, when the echo signal detection unit 50 is a superconducting nanowire single photon detector, it may include a refrigeration preparation and superconducting chip 51, an electric pulse signal amplification unit 52, and an electric pulse signal discrimination unit 53. The refrigeration preparation and superconducting chip 51 is used for converting a single photon signal into an electric pulse signal, the electric pulse signal amplifying unit 52 is used for amplifying the electric pulse signal, and the electric pulse signal discriminating unit 53 is used for discriminating the electric pulse signal exceeding a certain threshold value.
According to an embodiment of the present disclosure, the signal acquisition and processing unit 60 is configured to acquire the transmission signal and the reflection signal detected by the echo signal detection unit 50, measure intensity variations of the transmission signal and the reflection signal, and obtain the atmospheric wind speed information by inversion.
Specifically, the signal acquisition and processing unit 60 includes: a pick-up card 61 and a processor 62. The acquisition card 61 is used to acquire the transmission signal and the reflection signal detected by the echo signal detection unit 50. The processor 62 (e.g., a computer) is configured to measure the signal intensities of the transmitted signal and the reflected signal acquired by the acquisition card 61, and to obtain the atmospheric wind speed information by inversion.
Fig. 2 schematically illustrates an operational timing diagram of a lidar according to an embodiment of the present disclosure.
As shown in fig. 2, the gating of the seed laser pulse and the atmospheric echo signal is completed by the first optical switch 24 and the second optical switch 25, that is, the pulse laser line is incident into the atmosphere through the 1-2 channel of the first optical switch 24 and the 1-2 channel of the second optical switch 25, and then the 1-2 channel of the first optical switch 24 and the 1-2 channel of the second optical switch 25 are closed by adjusting the level of the electric signal input to the optical switch, so that the 3-2 channel of the first optical switch 24 and the 1-4 channel of the second optical switch 25 are opened, and the filtering of the atmospheric echo signal is completed. The laser frequency shifter 31 shifts the seed laser pulse frequency to the half height of the transmittance curve of the third filter 23. Through signal acquisition, a transmission signal and a reflection signal of the atmospheric echo signal through the third filter 23 are obtained, respectively, as shown in fig. 2.
Fig. 3 schematically illustrates a schematic diagram of a direct detection anemometry principle of a lidar according to an embodiment of the present disclosure.
Referring to fig. 3, since the transmit laser and the echo signal share a filter, the fabry-perot interferometer (FPI) spectrum and the laser spectrum have the same line type, and since the line type of the fabry-perot interferometer is a lorentz line type, the convolution of two lorentz functions is still the lorentz line type, and the width is the sum of the widths of the two lorentz functions. The convolution of the atmospheric echo signal and the fabry-perot interferometer is still lorentz, but the width is doubled, and the transmission spectrum and reflection spectrum of the atmospheric echo signal through the fabry-perot interferometer are shown in fig. 3 (b). The emitted laser frequency is shifted by using a laser frequency shifter (AOM), for example, to lock the laser frequency at half the height of the curve shown in fig. 3 (b).
The core module of the present disclosure is a filtering module 20, and by means of gating the first optical switch 24 and the second optical switch 25, the emitted laser and the atmospheric echo signal pass through the same filter 21, so as to implement a broad spectrum light source. In order to extract the frequency shift of the atmospheric echo signal, so as to realize the detection of the atmospheric wind field, the emitted laser is frequency-shifted to the edge of the filter 21 by the laser frequency shifter 31, when the frequency of the echo signal changes, the intensity of the transmitted signal and the reflected signal of the atmospheric echo signal on the filter 21 is caused to change, one is enhanced, the other is reduced, and the atmospheric wind speed information is extracted by the intensity information.
The invention discloses a direct detection wind lidar based on a wide-spectrum light source. The invention adopts a gating mode of two optical switches, so that the emitted laser and the atmospheric echo signal share one filter, and the direct detection wind-measuring laser radar based on a wide-spectrum light source is realized. In order to improve the sensitivity of wind measurement, the invention proposes to use a frequency shifter to shift the frequency of the emitted laser to the edge of the filter. When the atmospheric echo signal emits Doppler frequency shift, the intensity of a transmission signal and a reflection signal of the atmospheric echo signal on a filter is changed, one of the transmission signal and the reflection signal is enhanced, the other is reduced, and the atmospheric wind speed information is extracted through the intensity change information. Since the emitted laser and the atmospheric echo signal pass through the filter in the millisecond or even microsecond time, the invention has the advantages that firstly, the direct detection wind lidar is insensitive to the frequency drift of the laser and the filter; secondly, a narrow linewidth single-frequency laser is not needed, the emitted laser power can be improved by a wide-spectrum light source, and the cost of the laser is reduced; finally, no reference laser is needed, simplifying the light path.
The direct detection wind-finding laser radar based on the wide-spectrum light source has the following beneficial effects:
(1) The wide-spectrum laser is adopted, so that the requirement of the laser radar on the narrow linewidth of the laser is reduced, the laser emission power of the wide-spectrum laser can be improved, and the cost of the laser is reduced.
(2) The method has the advantages that the scheme that the transmitting laser and the atmospheric echo signal share one filter is provided, the transmitting laser is locked at the half height of a spectrum after convolution of the Fabry-Perot interferometer and the atmospheric echo signal through the laser frequency shifter, and because the transmitting laser and the atmospheric echo signal pass through the Fabry-Perot interferometer in microsecond time, the drift amount of the Fabry-Perot interferometer is negligible in the time scale, and the requirement of the direct detection wind-measuring laser radar on the stability of the Fabry-Perot interferometer is reduced.
(3) The present disclosure proposes a scheme in which the transmitting laser and the atmospheric echo signal share one filter, and since the position of the transmitting laser relative to the fabry-perot interferometer can be controlled by the laser frequency shifter, this omits the reference light of the conventional direct detection wind lidar, and simplifies the optical path.
Those skilled in the art will appreciate that the features recited in the various embodiments of the disclosure and/or in the claims may be provided in a variety of combinations and/or combinations, even if such combinations or combinations are not explicitly recited in the disclosure. In particular, the features recited in the various embodiments of the present disclosure and/or the claims may be variously combined and/or combined without departing from the spirit and teachings of the present disclosure. All such combinations and/or combinations fall within the scope of the present disclosure.
While the present disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. The scope of the disclosure should, therefore, not be limited to the above-described embodiments, but should be determined not only by the following claims, but also by the equivalents of the following claims.
Claims (7)
1. A wind lidar based on a broad spectrum light source, comprising:
a seed laser pulse generation unit (10) for generating a seed laser pulse;
-a filtering unit (20) comprising a filter (21), said filter (21) being adapted to filter the generated seed laser pulses;
a laser frequency shift and amplification unit (30) for receiving the filtered seed laser pulse filtered by the filtering unit (20) and frequency shifting and amplifying the filtered seed laser pulse;
a laser light transmitting and receiving unit (40) for receiving the frequency-shifted and amplified seed laser light pulse frequency-shifted and amplified by the laser light frequency-shifting and amplifying unit (30) and transmitting the frequency-shifted and amplified seed laser light pulse into the atmosphere; the laser transmitting and receiving unit (40) is further used for receiving an atmosphere echo signal formed after the frequency-shifted and amplified seed laser pulse interacts with the atmosphere;
an echo signal detection unit (50) for detecting a transmission signal and a reflection signal;
the atmospheric echo signals received by the laser transmitting and receiving unit (40) are filtered by the filter (21) to respectively obtain the transmission signals and the reflection signals, the transmission signals and the reflection signals are sensitive to atmospheric Doppler frequency shift, and the atmospheric wind speed information can be obtained by inversion through measuring the intensity changes of the transmission signals and the reflection signals;
wherein the filtering unit (20) further comprises:
a first optical switch (24) and a second optical switch (25), wherein the seed laser pulse and the atmospheric echo signal pass through the filter (21) in a time sharing way through a gating mode of the first optical switch (24) and the second optical switch (25),
wherein the first optical switch (24) is connected with the seed laser pulse generating unit (10), and the second optical switch (25) is connected with the laser frequency shift and amplification unit (30) and the echo signal detecting unit (50);
the seed laser pulse passes through a first optical channel of the first optical switch (24) and then enters the filter (21), the filter (21) filters the seed laser pulse to obtain the filtered seed laser pulse, and the filtered seed laser pulse enters the first optical channel of the second optical switch (25) and then is input to a laser frequency shift and amplification unit (30);
wherein the filtering unit (20) further comprises: a circulator (26), the circulator (26) being connected to the laser transmitting and receiving unit (40) and to an echo signal detecting unit (50),
the atmospheric echo signal received by the laser transmitting and receiving unit (40) passes through the circulator (26), then enters the filter (21) through a second optical channel of the first optical switch (24), and is filtered by the filter (21) to obtain a transmission signal and a reflection signal respectively; the transmission signal enters the echo signal detection unit (50) after passing through a second optical channel of the second optical switch (25); the reflected signal enters the echo signal detection unit (50) after passing through the second optical channel of the first optical switch (24) and the circulator (26).
2. The broad spectrum light source based wind lidar of claim 1, further comprising:
and the signal acquisition and processing unit (60) is used for acquiring the transmission signal and the reflection signal detected by the echo signal detection unit (50), measuring the intensity changes of the transmission signal and the reflection signal, and inverting to obtain the atmospheric wind speed information.
3. The broad spectrum light source based wind lidar of claim 1, wherein the seed laser pulse generation unit (10) comprises:
a seed laser (11) for generating a seed laser;
a pulse generator (12) connected to the seed laser (11) for receiving the seed laser and generating a pulse laser based on the seed laser;
and a first filter (13) connected with the pulse generator (12) and filtering the pulse laser to form the seed laser pulse.
4. The broad spectrum light source based wind lidar according to claim 1, wherein the filter (21) comprises a second filter (22) and a third filter (23), the second filter (22) and the third filter (23) being connected.
5. The broad spectrum light source based wind lidar as defined in claim 1, wherein the laser frequency shift and amplification unit (30) comprises:
a laser frequency shifter (31) connected to the filter unit (20) for receiving the filtered seed laser pulses from the filter unit (20) and frequency shifting the filtered seed laser pulses;
a delay fiber (32) connected to the laser frequency shifter (31) for receiving the frequency shifted seed laser pulse from the laser frequency shifter (31) and delaying the frequency shifted seed laser pulse so as to separate the atmospheric echo signal from the seed laser pulse in the time domain;
and the optical fiber amplifier (33) is connected with the delay optical fiber (32) and the laser transmitting and receiving unit (40) and is used for receiving the delayed seed laser pulse from the delay optical fiber (32), amplifying the delayed seed laser pulse to obtain the frequency-shifted and amplified seed laser pulse, and inputting the frequency-shifted and amplified seed laser pulse into the laser transmitting and receiving unit (40).
6. The broad spectrum light source based wind lidar of claim 2, wherein the signal acquisition and processing unit (60) comprises:
an acquisition card (61) for acquiring the transmission signal and the reflection signal detected by the echo signal detection unit (50);
and the processor (62) is used for measuring the intensity changes of the transmission signal and the reflection signal acquired by the acquisition card (61) and obtaining the atmospheric wind speed information in an inversion mode.
7. The broad spectrum light source based wind lidar as defined in claim 1, wherein the laser transmitting and receiving unit (40) comprises:
-a transmitting telescope (41) for transmitting the frequency shifted and amplified seed laser pulses from the laser frequency shifting and amplifying unit (30) into the atmosphere;
-a receiving telescope (42) for receiving the atmospheric echo signal from the atmosphere and inputting the atmospheric echo signal to the filtering unit (20).
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| PCT/CN2019/099781 WO2020199447A1 (en) | 2019-03-29 | 2019-08-08 | Broad-spectrum light source-based wind measurement lidar |
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| CN109959944B (en) * | 2019-03-29 | 2023-06-16 | 中国科学技术大学 | Wind lidar based on wide-spectrum light source |
| CN110764104B (en) * | 2019-11-07 | 2023-05-12 | 浙江缔科新技术发展有限公司 | Light quantum laser sighting telescope with wind measuring function |
| CN111257851B (en) * | 2020-04-03 | 2022-04-05 | 厦门大学 | Spectrum measurement method based on wide-spectrum light source and spectrum scanning laser radar |
| CN113281725A (en) * | 2021-05-13 | 2021-08-20 | 中国科学技术大学 | Laser radar optical transceiving system and feedback adjusting method thereof |
| CN115015966B (en) * | 2022-08-04 | 2022-10-28 | 南京信息工程大学 | Gas detection laser radar based on wide-spectrum light source |
| CN115453574B (en) * | 2022-10-27 | 2023-04-25 | 南京信息工程大学 | Multi-functional laser radar of atmosphere multiparameter detection |
| CN117031500B (en) * | 2023-05-11 | 2024-02-13 | 珠海光恒科技有限公司 | Light source system and method for long-distance all-fiber laser Doppler wind-finding radar |
| CN117214918B (en) * | 2023-11-09 | 2024-03-29 | 中国科学技术大学 | Rayleigh Doppler temperature measurement wind measurement laser radar |
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