WO2020056756A1 - 脉冲相干多普勒测风激光雷达及测风方法 - Google Patents

脉冲相干多普勒测风激光雷达及测风方法 Download PDF

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Publication number
WO2020056756A1
WO2020056756A1 PCT/CN2018/107084 CN2018107084W WO2020056756A1 WO 2020056756 A1 WO2020056756 A1 WO 2020056756A1 CN 2018107084 W CN2018107084 W CN 2018107084W WO 2020056756 A1 WO2020056756 A1 WO 2020056756A1
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signal
optical
scattered light
pulse
atmospheric
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PCT/CN2018/107084
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English (en)
French (fr)
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钱勇
朱海龙
周军
黄晨
高炎锟
李智
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南京牧镭激光科技有限公司
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Priority to PCT/CN2018/107084 priority Critical patent/WO2020056756A1/zh
Priority to JP2020572591A priority patent/JP7029620B2/ja
Publication of WO2020056756A1 publication Critical patent/WO2020056756A1/zh

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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
    • 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

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  • the present application relates to the field of radar technology, and in particular, to a pulse coherent Doppler wind measurement laser radar and a wind measurement method.
  • Doppler wind lidar technology It came into being, it is a high-precision atmospheric wind field information telemetry technology, which mainly uses the principle of Doppler frequency shift to measure the atmospheric wind field.
  • pulse coherent Doppler wind measurement lidar which is widely used, still suffers from more noise interference, resulting in lower signal-to-noise and lower accuracy of wind measurement.
  • the object of the present application includes providing a pulse coherent Doppler wind measurement lidar and a wind measurement method, which can improve at least one of the above problems.
  • an embodiment of the present application provides a pulsed coherent Doppler wind measurement laser radar, including: a light source transmitting unit, a signal receiving unit, a detecting unit, and a signal processing unit; the light source transmitting unit and the signal receiving unit Both are connected to the detection unit, and the detection unit is also connected to the signal processing unit; wherein the signal receiving unit and / or the detection unit is provided with at least one noise filtering device; the light source The transmitting unit is configured to transmit a laser pulse to the airspace to be measured, and is also configured to transmit a local oscillating optical signal to the detection unit; the signal receiving unit is configured to receive an atmospheric scattered light signal, and is further configured to transmit the atmospheric scattered light signal Transmitted to the detection unit; wherein the atmospheric scattered light signal is obtained by scattering the laser pulse by atmospheric particles in the airspace to be measured; the detection unit is configured to be based on the local oscillating optical signal and the Atmospheric scattered light signals are subjected to beat balance detection and detection results are obtained; the signal processing
  • the noise filtering device in the signal receiving unit includes a fast electro-optical switch and / or a fiber grating filter.
  • the noise filtering device in the signal detection unit includes an optical fiber delay line.
  • the light source transmitting unit includes a local oscillating light source, a light modulator, a fiber amplifier, a first optical circulator, and a transmitting and receiving co-optic antenna connected in sequence; the pulse synchronization signal generator and A driver; wherein the driver is connected to the pulse synchronization signal generator and the optical modulator, respectively.
  • the local oscillating light source is configured to output two continuous laser beams, transmit a first laser beam to the detection unit, and transmit a second laser beam to the light modulation.
  • the first laser beam is used as the local oscillating optical signal
  • the second laser beam is used as a seed source of laser pulses emitted to the airspace to be measured
  • the optical modulator is configured to The second laser beam is modulated into a preset laser pulse, and the laser pulse is transmitted to the fiber amplifier
  • the pulse synchronization signal generator is configured to generate a synchronous pulse electrical signal and convert the synchronization pulse
  • the electric signal is transmitted to the driver;
  • the driver is configured to amplify the synchronous pulse electric signal, and the amplified optical signal is used to drive the optical modulator to work;
  • the fiber amplifier is configured to amplify the laser pulse To obtain the laser pulse to be transmitted, and transmit the laser pulse to be transmitted to the transceiver optical antenna through the first optical circulator;
  • the antenna is configured to transmit the laser pulse to be transmitted to
  • the first optical circulator includes a first port, a second port, and a third port; the first optical circulator is configured to receive the laser light to be transmitted through the first port. Pulse, and transmitting the laser pulse to be transmitted to the transceiver optical antenna through the second port; the first optical circulator is further configured to receive the atmospheric scattered light signal through the second port, And transmitting the atmospheric scattered light signal to the signal receiving unit through the third port.
  • the optical isolation between the first port and the third port is greater than 50 dB.
  • the local oscillation light source is a single-frequency low-noise semiconductor laser source; and / or, the optical modulator is a fiber acousto-optic modulator or a fiber electro-optic modulator; and / or,
  • the fiber amplifier is an erbium-doped fiber amplifier or an erbium co-doped fiber amplifier.
  • the signal receiving unit includes a fast electro-optical switch.
  • the signal receiving unit further includes a second optical circulator and a fiber grating filter; wherein the fast electro-optical switch, the second optical circulator, and the fiber grating filter are in order connection.
  • the fast electro-optical switch is further connected to the first optical circulator and the pulse synchronization signal generator, respectively; the first optical circulator is further configured to scatter the light from the atmosphere A signal is transmitted to the fast electro-optic switch; the pulse synchronization signal generator is further configured to transmit the synchronization pulse electrical signal to the fast electro-optic switch; the fast electro-optic switch is configured to change a switch in accordance with the synchronous pulse electrical signal State, filtering out scattered light noise in the atmospheric scattered light signal, and transmitting the scattered light noise filtered out of the scattered light noise to the fiber grating filter through the second optical circulator; the optical fiber The grating filter is configured to perform a spectral noise filtering process on the atmospheric scattered light signal filtered out of the scattered light noise, and transmit the atmospheric scattered light signal processed by the spectral noise filtering process to the second optical circulator to the optical circulator. Detection unit.
  • the second optical circulator includes a fourth port, a fifth port, and a sixth port; the second optical circulator is configured to receive and filter out the scattering through the fourth port.
  • the atmospheric scattered light signal of the optical noise is transmitted to the fiber grating filter through the fifth port, and the second optical circulator is further configured to pass through the fifth port.
  • the fifth port receives the atmospheric scattered light signal after the spectral noise filtering process, and transmits the atmospheric scattered light signal after the spectral noise filtering process to the detection unit through the sixth port.
  • the reflection bandpass width of the fiber grating filter is less than 1 nm.
  • the detection unit includes a tunable optical attenuator, a fiber delay line, and an optical mixing detector connected in sequence.
  • the adjustable optical attenuator is further connected to the local oscillating light source; the adjustable optical attenuator is configured to transmit the local oscillating light transmitted by the local oscillating light source Adjust the intensity of the signal, and transmit the local oscillating optical signal after the intensity is adjusted to the optical fiber delay line; the optical fiber delay line is configured to delay the local oscillating optical signal after the intensity is adjusted to reach the optical hybrid Frequency detector time; the optical mixing detector is configured to perform beat balance detection on the atmospheric scattered light signal after the spectral noise filtering process and the local oscillating light signal after a delay time, and obtain Detection results.
  • the photosensitive material of the optical mixing detector includes indium gallium arsenic.
  • the radar adopts an all-fiber structure or a non-all-fiber structure.
  • an embodiment of the present application further provides a wind measurement method, where the method is applied to the pulse coherent Doppler wind measurement lidar according to any one of the first aspect, and the method includes: the light source The transmitting unit transmits a laser pulse to the airspace to be measured, and transmits a local oscillating optical signal to the detecting unit; the signal receiving unit receives an atmospheric scattered light signal, and transmits the atmospheric scattered light signal to the detecting unit; wherein The atmospheric scattered light signal is obtained by scattering the laser pulse by atmospheric particles in the airspace to be measured; the detection unit performs beat balance detection based on the local oscillation light signal and the atmospheric scattered light signal, A detection result is obtained; the signal processing unit calculates wind speed information according to the detection result and a Doppler effect relationship.
  • Embodiments of the present application provide a pulse coherent Doppler wind measurement laser radar and a wind measurement method.
  • the radar includes a light source transmitting unit, a signal receiving unit, a detecting unit, and a signal processing unit. Among them, the signal receiving unit and / or the detecting unit There is at least one noise filtering device in the filter. Since the noise filtering device can better reduce the influence of noise on the signal-to-noise ratio by filtering the noise, compared with the existing pulse coherent Doppler wind lidar, The radar provided by the embodiment has a high signal-to-noise ratio, which is helpful to further improve the accuracy of the radar's wind measurement.
  • FIG. 1 shows a schematic structural diagram of a pulse coherent Doppler wind measurement laser radar provided by an embodiment of the present application
  • FIG. 2 shows a specific structural schematic diagram of a pulse coherent Doppler wind measurement laser radar provided by an embodiment of the present application
  • FIG. 3 shows an optical path principle diagram of a pulse coherent Doppler wind measurement laser radar provided by an embodiment of the present application
  • FIG. 4 shows a schematic diagram of an atmospheric transmission spectrum range of 0.8-2.2 micrometers provided by an embodiment of the present application
  • FIG. 5 shows a typical spectral response curve of an indium gallium arsenic photodetector provided by an embodiment of the present application
  • FIG. 6 shows a flowchart of a wind measurement method according to an embodiment of the present application.
  • Optical mixing detectors are photosensors of photosensitive materials with a certain response spectral range. The response spectral width is generally much larger than the optical signal spectrum. Width, the detected background noise of the optical signal includes part of the solar radiation spectral noise, stray light noise generated by the interaction of particles of various scales in the atmosphere with the laser beam, thereby reducing the signal-to-noise ratio of the radar system.
  • phase / frequency noise of the local oscillating light source in the pulse coherent Doppler wind lidar will broaden the effective signal spectral peak width resolved by the optical mixing detection, thereby affecting the signal-to-noise ratio and inverse calculation Wind speed accuracy.
  • a pulse coherent Doppler wind measurement lidar and a wind measurement method provided by the embodiments of the present application can be applied to technologies such as clean wind power energy development, meteorological science, and airspace wind shear in civil aviation airports Early warning, wind tunnel fluid mechanics research, space atmospheric science research, and other fields that need to detect atmospheric wind fields.
  • technologies such as clean wind power energy development, meteorological science, and airspace wind shear in civil aviation airports Early warning, wind tunnel fluid mechanics research, space atmospheric science research, and other fields that need to detect atmospheric wind fields.
  • a pulse coherent Doppler wind lidar shown in FIG. 1, including: a light source transmitting unit, a signal receiving unit, a detecting unit, and a signal processing unit; the light source transmitting unit and the signal receiving unit are both connected with The detection unit is connected, and the detection unit is further connected to the signal processing unit.
  • the signal receiving unit and / or the detection unit are provided with at least one noise filtering device (not shown in FIG. 1).
  • the basic principles of the light source transmitting unit, signal receiving unit, detection unit and signal processing unit are as follows:
  • the light source transmitting unit is configured to transmit a laser pulse to the airspace to be measured, and is also configured to transmit a local oscillating optical signal to the detecting unit.
  • the signal receiving unit is configured to receive the atmospheric scattered light signal, and is also configured to transmit the atmospheric scattered light signal to the detection unit; wherein the atmospheric scattered light signal is obtained by scattering a laser pulse by atmospheric particles in the airspace to be measured.
  • the detection unit is configured to perform beat balance detection based on the local oscillation light signal and the atmospheric scattered light signal, and obtain a detection result.
  • the detection unit may mix the local oscillating light signal and the atmospheric scattered light signal, and generate a detection result of the analog electrical signal (which may be a time domain analog electrical signal) after the beat balance detection.
  • the signal processing unit is configured to calculate the wind speed information according to the detection result and the Doppler effect relationship.
  • the signal processing unit may first convert an analog electrical signal into a digital electrical signal, and then convert the time-domain data to the frequency-domain data through a fast discrete Fourier transform, and calculate the real-time according to the Doppler effect relationship. Wind speed data information.
  • the pulse coherent Doppler wind measurement laser radar provided by the embodiment of the present application includes a light source transmitting unit, a signal receiving unit, a detecting unit, and a signal processing unit. At least one of the signal receiving unit and / or the detecting unit is provided in the signal receiving unit and / or the detecting unit.
  • kind of noise filtering device because the noise filtering device can reduce the influence of noise on the signal-to-noise ratio by filtering the noise.
  • the radar provided by this embodiment Has a higher signal-to-noise ratio, which helps to further improve the accuracy of radar wind measurement.
  • the noise filtering device in the signal receiving unit may include a fast electro-optical switch and / or a fiber grating filter.
  • the noise filtering device in the signal detection unit may include an optical fiber delay line.
  • the noise filtering device provided in the embodiments of the present application may be implemented by using one or more of a fast electro-optical switch, a fiber grating filter, and a light delay line. Of course, other noise filtering devices may also be used, and will not be performed here. limit.
  • the pulse coherent Doppler wind measurement laser radar provided by this embodiment may adopt an all-fiber structure or a non-all-fiber structure, which is not limited herein.
  • FIG. 1 Based on FIG. 1, reference may be made to a specific structural schematic diagram of a pulse coherent Doppler wind measurement lidar shown in FIG. 2, and based on FIG. 2, a pulse coherent Doppler shown in FIG. 3 may be further referred to.
  • the principle of the optical path of the wind measurement lidar The difference between Figure 2 and Figure 3 is that Figure 2 simply shows the specific components included in the lidar and the connection relationship between the components.
  • the solid line in Figure 2 only represents two There is an association relationship between the two devices.
  • FIG. 3 further illustrates the signal transmission form between different devices.
  • the solid line in FIG. 3 indicates that the two devices are laser transmission, and the dotted line indicates that the two devices are to be tested. Atmospheric echo signals (that is, the above-mentioned atmospheric scattered light signals) are transmitted, and the dot-dash line indicates that electrical signals are transmitted between the two devices.
  • Atmospheric echo signals that is, the above-mentioned atmospheric scattered light signals
  • the light source transmitting unit may include a local oscillating light source, a light modulator, a fiber amplifier, a first optical circulator, and a co-located optical antenna connected in sequence; a pulse synchronization signal generator and a driver; wherein the driver and the pulse synchronization signal are respectively
  • the generator is connected to a light modulator.
  • the local oscillating light source is configured to output two continuous laser beams, transmit the first laser beam to the detection unit, and transmit the second laser beam to the optical modulator; wherein the first laser beam is used as the local oscillating optical signal
  • the second laser beam is used as the seed source of the laser pulse emitted to the airspace to be measured.
  • the local oscillating light source may be a single-frequency low-noise semiconductor laser with a wavelength of 1.5 micrometers (which belongs to the human eye-safe optical band).
  • the optical modulator is configured to modulate the second laser beam into a preset laser pulse (such as having a set repetition frequency and pulse width, and the modulation carrier frequency is a beat detection intermediate frequency), and transmits the laser pulse to a fiber amplifier
  • the pulse synchronization signal generator is configured to generate a synchronization pulse electrical signal and transmit the synchronization pulse electrical signal to the driver;
  • the driver is configured to amplify the synchronization pulse electrical signal and use the amplified synchronization pulse electrical signal to drive the optical modulator to work.
  • the optical modulator may use a fiber-optic acousto-optic modulator (of course, in practical applications, the optical modulator may also use an electro-optic modulator) to modulate continuous laser light into laser pulses, pulse repetition frequency, and pulse width. Determined by the pulse synchronization signal generator.
  • the pulse synchronization signal generator outputs a synchronous electric pulse signal.
  • the pulse repetition frequency and pulse width of the electric pulse determine the shape, repetition frequency and pulse width of the pulsed optical signal emitted by the laser radar.
  • Synchronous electrical pulse signals can be divided into two channels. One is driven by the driver to drive the optical modulator with appropriate RF power, and the other can be used to control the fast electro-optic switch in the signal receiving unit synchronously. Do not go into details).
  • the optical modulator modulates an input electrical signal (such as an analog or digital TTL signal), and amplifies the RF power through the driver.
  • the driver is then connected to the light through a standard SMA interface.
  • the interface of the optical modulator may include an electrical interface and an optical interface.
  • the electro-optic crystals and acousto-optic crystals in the optical modulator are driven by sufficient radio frequency power to pass the electro-optic effect, acousto-optic
  • the effect produces a pulse modulation effect on the incident laser light, thereby converting the continuous optical signal into a pulsed optical signal, that is, the optical modulator can modulate the continuous laser light into a laser pulse with a certain repetition frequency, pulse width, and modulation carrier frequency as the beat detection intermediate frequency.
  • the fiber amplifier is configured to amplify the energy of the laser pulse to obtain the laser pulse to be transmitted, and transmit the laser pulse to be transmitted to the transmitting and receiving co-optic antenna through the first optical circulator.
  • the fiber amplifier may be an erbium-doped fiber amplifier or an erbium-doped fiber amplifier, which is used to amplify the laser pulse energy.
  • the pulse energy may be expanded in a multi-stage amplifier cascade.
  • the energy of the laser pulse to be transmitted is determined by the radar system index (mainly the distance of the detection range). Generally, it is confirmed according to the actual field test of the radar application. To adjust the laser energy, only the laser control current needs to be adjusted. It can be understood that the atmosphere has an attenuation effect on the laser signal. The higher the laser energy, the farther the laser is emitted, and the stronger the optical signal scattered back to the radar at the same distance, the stronger it becomes a useful detection signal.
  • the transmitting and receiving co-optical antenna is configured to transmit the laser pulse to be transmitted to the airspace to be measured, and the transmitting and receiving co-optical antenna is also configured to receive the atmospheric scattered light signal obtained by scattering of atmospheric particles in the airspace to be measured, and pass the atmospheric scattered light signal through
  • the optical circulator is transmitted to the signal receiving unit. Specifically, a laser pulse is emitted into the atmosphere, and after moving aerosol particles in the atmosphere are irradiated with the laser light, the scattered light signal is reflected and sent back to the same optical antenna.
  • the connection between the first optical circulator and the transmitting and receiving co-optical antenna may be as follows: an optical fiber connector at one end of the first optical circulator is connected to the connection port of the transmitting and receiving co-optical antenna and fixed. After the laser light is emitted from the end face of the optical fiber, it is focused and transmitted to the atmosphere through the optical lens and window mirror in the same optical antenna. Co-located optical antenna.
  • the first optical circulator includes a first port C1, a second port C2, and a third port C3; wherein the first optical circulator is configured to receive a laser pulse to be transmitted through the first port C1 and pass the first port
  • the second port C2 transmits the laser pulse to be transmitted to the co-located optical antenna;
  • the first optical circulator is further configured to receive the atmospheric scattered light signal through the second port C2, and transmit the atmospheric scattered light signal to the signal receiving through the third port C3 unit.
  • the laser pulse to be transmitted enters the second port C2 from the first port C1 of the first optical circulator, and then is transmitted to the air space to be measured through the transmitting and receiving optical antenna; the scattered light signal is collected by the receiving and transmitting optical antenna ,
  • the second port C2 of the first optical circulator enters the third port C3, and then the third port C3 enters the subsequent signal receiving unit.
  • the first optical circulator is a three-port fiber circulator.
  • the unidirectional propagation direction of the laser between the ports is C1 ⁇ C2, C2 ⁇ C3, and the propagation directions of C1 ⁇ C3 and C2 ⁇ C1 are prohibited.
  • the optical isolation between C1 and C3 is> 50dB.
  • the signal receiving unit may include a fast electro-optical switch, a second optical circulator, and a fiber grating filter connected in order; wherein the fast electro-optic switch, the second optical circulator, and a fiber grating filter are connected in order. Further, the fast electro-optical switch is also connected to the first optical circulator and the pulse synchronization signal generator, respectively.
  • the first optical circulator is further configured to transmit atmospheric scattered light signals to the fast electro-optic switch; the pulse synchronization signal generator is further configured to transmit synchronization pulse electric signals to the fast electro-optic switch.
  • the fast electro-optical switch is configured to change the switching state according to the synchronous pulse electrical signal, filter out scattered light noise in the scattered light signal, and transmit the scattered light signal filtered out by the scattered light noise to the fiber grating filter through the second optical circulator.
  • the fiber grating filter is configured to perform a spectral noise filtering process on the atmospheric scattered light signal filtered by the scattered light noise, and transmit the atmospheric scattered light signal processed by the spectral noise filtering process to the detection unit through a second optical circulator.
  • the fiber grating filter can reflect the light in the effective spectral range and transmit the light in the non-effective spectrum, so as to filter out the light in the non-effective spectrum.
  • the second optical circulator is mainly configured to guide the optical signal processed by the fast electro-optic switch to a fiber grating filter for spectral filtering. After the spectral noise is filtered, the optical signal filtered out from the spectral noise is guided into the optical mixer.
  • Frequency detector Specifically, the second optical circulator provided in this embodiment includes a fourth port C4, a fifth port C5, and a sixth port C6; wherein the second optical circulator is configured to receive and filter out scattered light noise through the fourth port C4.
  • the scattered light signal from the atmosphere and transmits the scattered light signal filtered by the scattered light noise to the fiber grating filter through the fifth port C5; the second optical circulator is further configured to receive the spectral noise filtering process through the fifth port C5 The atmospheric scattered light signal is transmitted to the detection unit through the sixth port C6.
  • the reflection bandpass width of the fiber grating filter provided in this embodiment may be less than 1nm.
  • the bandpass spectral width is larger. Wider, the more the other optical noise within the spectral width; and 1nm is an empirical value, and device manufacturers can provide large quantities of stable performance devices, which is helpful for large-scale applications.
  • the center wavelength of the lidar light source provided in the embodiments of the present application is determined by the center wavelength of the local oscillating light source, because 1550nm is a standard commonly used wavelength in the optical communication industry. The specific precise value is due to differences in manufacturing processes and materials, and batch device values.
  • the fiber grating filter provided in this embodiment can reflect an effective optical signal with a wavelength in the 1 nm spectral range around 1550 nm back to the second optical circulator, and enter the sixth port C6 from the fifth port C5.
  • the background light noise outside the effective spectral range (as shown in Figure 4 is the atmospheric transmission spectral range of 0.8-2.2 microns) passes through the fiber grating filter and is filtered by the fiber grating filter, thereby achieving the function of spectral noise filtering.
  • the entire all-fiber laser light sources (such as those that can contain local oscillator light sources, optical modulators, fiber amplifiers, drivers, etc.) are all miniature fiber optic devices used in the fiber optic communications industry
  • the device connection adopts the optical fiber fusion method, all optical signals are transmitted in the optical fiber, and there is no exposed free space, so that the scattered (or reflected) signal generated by the end face of the optical fiber is easily larger than the effective atmospheric scattered light signal.
  • this embodiment is provided with a fast electro-optic switch to filter out scattered light noise mixed in the scattered light signal of the atmosphere.
  • the specific principle is as follows:
  • the optical signal received by the third port C3 of the first optical circulator includes a transmitting and receiving signal.
  • the strong scattered light pulses generated by the fiber end face and the optical mirror surface of the optical antenna are installed.
  • the fast electro-optical switch can be based on the trigger timing control signal of the pulse synchronization signal generator (corresponding to the aforementioned synchronization pulse electrical signal). Scattered light pulses (corresponding to the aforementioned scattered light noise). It can be understood that the scattered light pulses or reflected light pulses in the radar (both fiber end faces, optical mirrors in the telescope, and emission optical windows can be generated, and the signal is very strong) and echo light signals scattered by particles in the long-distance atmosphere (that is, The aforementioned atmospheric scattered light signal has a weak time). There is a certain time difference. The scattered light pulse inside the radar first reaches the fast electro-optical switch.
  • the fast electro-optical switch changes the OFF state to the ON state.
  • the duration of the ON state can be slightly longer than the duration of the light pulse signal (usually on the order of 100ns). Because the switching speed of the switch ON / OFF is relatively fast (such as generally requiring ⁇ 10ns), a corresponding fast electro-optical switch can be selected for implementation.
  • the detection unit provided in this embodiment may include a tunable optical attenuator, a fiber delay line, and an optical mixing detector connected in this order. Moreover, the adjustable optical attenuator is also connected to the local oscillating light source.
  • the adjustable optical attenuator is configured to adjust the intensity of the local oscillating light signal transmitted by the local oscillating light source, and transmit the adjusted local oscillating light signal to the fiber delay line.
  • the fiber delay line is configured to delay the time when the local oscillating optical signal reaches the optical mixing detector after adjusting the intensity.
  • the optical mixing detector is configured to perform beat balance detection on the atmospheric scattered light signal after the spectral noise filtering process and the local oscillation light signal after the delay time, and obtain the detection result, and transmit the detection result to the signal processing unit.
  • the optical mixing detector can use indium gallium arsenide (InGaAs) as the main photosensitive material.
  • InGaAs indium gallium arsenide
  • the typical spectral response curve of indium gallium arsenide (InGaAs) is shown in Figure 5. It can also prove the effectiveness of spectral filtering of the aforementioned atmospheric scattered light signal, that is, the wide-spectrum noise outside the center wavelength of the optical signal can be efficiently filtered before detection.
  • the pulse coherent Doppler wind lidar mainly uses the principle of coherent detection to measure wind speed data. Specifically, the local oscillating optical signal (which also carries optical noise) and the scattered light signal (including other stray light) (Noise and scattered light signals reflecting wind speed, etc.) After mixing, the optical mixing detector outputs analog electrical signals, and the precise Doppler frequency difference that can reflect wind speed can be resolved by high-precision digital sampling of this analog electrical signal. .
  • the embodiments of the present application can first use local noise filter devices arranged in the radar system to filter the local oscillating light signal and the atmospheric scattered light signal, thereby improving the radar signal-to-noise ratio and helping to further improve the accuracy of wind measurement.
  • the optical fiber delay line is also a kind of noise filter device.
  • the basic principle of the optical fiber delay line provided in the embodiments of the present application is: the local oscillating optical signal and the atmospheric scattered optical signal (also the energy of the local oscillating optical signal are irradiated after being amplified) Atmospheric particles, and then scattered back signal)
  • the self-frequency or phase noise is time-dependent. If the local oscillator light signal and the atmospheric scattered light signal have the same transient phase or frequency at a transient moment, then The coherent detection sensitivity and efficiency will be better after mixing.
  • a fiber delay line is mainly used to delay the local oscillation light signal to make the local oscillation light as much as possible.
  • the signal and the atmospheric scattered light signal have the same transient phase or frequency, thereby reducing the influence of the frequency noise of the local oscillating light source on the signal-to-noise ratio.
  • the method of using a fiber delay line to delay the local oscillating optical signal can reduce the loss better than the method of delaying the atmospheric scattered optical signal (it is extremely weak), and can also make the structure of the radar system more reasonable.
  • the signal processing unit can convert the detection result (analog electrical signal in the time domain) into an analog digital signal, and transform the time domain data into the frequency domain data through a fast discrete Fourier transform. It can also process algorithms based on different spectral noise To calculate real-time wind speed data information.
  • the pulse coherent Doppler wind measurement lidar uses a combination of some optical fiber active and passive components to focus on several major influence signals in the pulse coherent Doppler wind measurement lidar.
  • the noise source of the noise ratio is filtered. For example, because the optical fiber delay line is set, the phase / frequency noise of the local oscillating light source can be reduced, and the selection range and technical specifications of related components can be further relaxed. To reduce costs. Because the fast photoelectric switch is set, the scattered light noise generated on the end face of the fiber can be effectively reduced; because the fiber grating filter is set, the background light noise outside the effective spectral range can be effectively filtered out.
  • This embodiment also provides a wind measurement method, which is applied to any one of the foregoing pulse-coherent Doppler wind measurement lidars provided in this embodiment. As shown in a flowchart of a wind measurement method shown in FIG. 6, Methods include:
  • Step S602 the light source transmitting unit transmits a laser pulse to the airspace to be measured, and transmits a local oscillating optical signal to the detecting unit;
  • Step S604 The signal receiving unit receives the atmospheric scattered light signal and transmits the atmospheric scattered light signal to the detection unit; wherein the atmospheric scattered light signal is obtained by scattering the laser pulse by atmospheric particles in the airspace to be measured;
  • Step S606 The detection unit performs beat balance detection based on the local oscillation light signal and the atmospheric scattered light signal, and obtains a detection result;
  • Step S608 The signal processing unit calculates the wind speed information according to the detection result and the Doppler effect relationship.
  • At least one noise filtering device is provided in the signal receiving unit and / or detection unit. By filtering the noise, the influence of noise on the signal-to-noise ratio can be better reduced, which will further improve the accuracy of radar wind measurement.
  • the terms “installation”, “connected”, and “connected” shall be understood in a broad sense unless otherwise specified and limited, for example, they may be fixed connections, detachable connections, or Integrated connection; it can be mechanical or electrical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements.
  • installation shall be understood in a broad sense unless otherwise specified and limited, for example, they may be fixed connections, detachable connections, or Integrated connection; it can be mechanical or electrical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two elements.
  • the specific meanings of the above terms in this application can be understood in specific situations.
  • noise can be better filtered, which helps to improve the signal-to-noise ratio of the radar and accuracy of wind measurement.

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Abstract

提供了一种脉冲相干多普勒测风激光雷达及测风方法，包括光源发射单元、信号接收单元、探测单元和信号处理单元；光源发射单元和信号接收单元均与探测单元相接，探测单元还与信号处理单元相接；其中，信号接收单元和/或探测单元中设置有至少一种噪声过滤器件；光源发射单元配置成向待测空域发射激光脉冲，还配置成向探测单元传输本机振荡光信号；信号接收单元配置成接收大气散射光信号，还配置成将大气散射光信号传输至探测单元；其中，大气散射光信号是激光脉冲经待测空域的大气颗粒散射得到的；探测单元配置成基于本机振荡光信号和大气散射光信号进行差拍平衡探测，并得到探测结果；信号处理单元配置成根据探测结果和多普勒效应关系式计算得到风速信息。本申请能够较好的过滤噪声，有助于提升雷达的信噪比和测风准确率。

Description

脉冲相干多普勒测风激光雷达及测风方法 技术领域
本申请涉及雷达技术领域，尤其是涉及一种脉冲相干多普勒测风激光雷达及测风方法。
背景技术
在诸如清洁风电能源开发、气象科学、民航机场空域风切变预警、风洞流体力学研究、空间大气科学研究等多种领域都需要较为准确地探测大气风场，多普勒测风激光雷达技术应运而生，其是一种高精度大气风场信息遥测技术，主要利用多普勒移频的原理测量大气的风场。而目前应用广泛的脉冲相干多普勒测风激光雷达，仍旧会受到较多噪声干扰，导致信噪比较低，测风准确率不高。
发明内容
有鉴于此，本申请的目的包括，提供一种脉冲相干多普勒测风激光雷达及测风方法，能够改善上述问题至少之一。
本申请实施例采用的技术方案如下：
第一方面，本申请实施例提供了一种脉冲相干多普勒测风激光雷达，包括：光源发射单元、信号接收单元、探测单元和信号处理单元；所述光源发射单元和所述信号接收单元均与所述探测单元相接，所述探测单元还与所述信号处理单元相接；其中，所述信号接收单元和/或所述探测单元中设置有至少一种噪声过滤器件；所述光源发射单元配置成向待测空域发射激光脉冲，还配置成向所述探测单元传输本机振荡光信号；所述信号接收单元配置成接收大气散射光 信号，还配置成将所述大气散射光信号传输至所述探测单元；其中，所述大气散射光信号是所述激光脉冲经所述待测空域的大气颗粒散射得到的；所述探测单元配置成基于所述本机振荡光信号和所述大气散射光信号进行差拍平衡探测，并得到探测结果；所述信号处理单元配置成根据所述探测结果和多普勒效应关系式计算得到风速信息。
在一种优选的实施方式中，所述信号接收单元中的噪声过滤器件包括快速电光开关和/或光纤光栅滤波器。
在一种优选的实施方式中，所述信号探测单元中的噪声过滤器件包括光纤延迟线。
在一种优选的实施方式中，所述光源发射单元包括依次连接的本机振荡光源、光调制器、光纤放大器、第一光环形器和收发同置光学天线；还包括脉冲同步信号发生器和驱动器；其中，所述驱动器分别与所述脉冲同步信号发生器和所述光调制器相连。
在一种优选的实施方式中，所述本机振荡光源配置成输出两路连续激光束，将第一路激光束传输给所述探测单元，并将第二路激光束传输给所述光调制器；其中，所述第一路激光束作为所述本机振荡光信号，所述第二路激光束作为发射到所述待测空域的激光脉冲的种子源；所述光调制器配置成将所述第二路激光束调制成预设的激光脉冲，并将所述激光脉冲传送至所述光纤放大器；其中，所述脉冲同步信号发生器配置成产生同步脉冲电信号，将所述同步脉冲电信号传输给所述驱动器；所述驱动器配置成放大所述同步脉冲电信号，采用放大后的所述同步脉冲电信号驱动所述光调制器工作；所述光纤放大器配置成放大所述激光脉冲的能量，得到待发射激光脉冲，并将所述待发射激光脉冲通过所述第一光环形器传输给所述收发同置光学天线；所述收发同置光学天 线配置成将所述待发射激光脉冲发射至待测空域，所述收发同置光学天线还配置成接收所述待测空域的大气颗粒散射得到的大气散射光信号，并将所述大气散射光信号通过所述第一光环形器传输给所述信号接收单元。
在一种优选的实施方式中，所述第一光环形器包括第一端口、第二端口和第三端口；所述第一光环形器配置成通过所述第一端口接收所述待发射激光脉冲，并通过所述第二端口将所述待发射激光脉冲传输给所述收发同置光学天线；所述第一光环形器还配置成通过所述第二端口接收所述大气散射光信号，并通过所述第三端口将所述大气散射光信号传输给所述信号接收单元。
在一种优选的实施方式中，所述第一端口和所述第三端口之间的光隔离度大于50dB。
在一种优选的实施方式中，所述本机振荡光源为单频低噪声半导体激光源；和/或，所述光调制器为光纤声光调制器或光纤电光调制器；和/或，所述光纤放大器为掺铒光纤放大器或铒镱共掺光纤放大器。
在一种优选的实施方式中，所述信号接收单元包括快速电光开关。
在一种优选的实施方式中，所述信号接收单元还包括第二光环形器和光纤光栅滤波器；其中，所述快速电光开关、所述第二光环形器和所述光纤光栅滤波器依次连接。
在一种优选的实施方式中，所述快速电光开关还分别与所述第一光环形器和所述脉冲同步信号发生器相连；所述第一光环形器还配置成将所述大气散射光信号传输给所述快速电光开关；所述脉冲同步信号发生器还配置成将所述同步脉冲电信号传输给所述快速电光开关；所述快速电光开关配置成按照所述同步脉冲电信号更改开关状态，滤除所述大气散射光信号中的散射光噪声，并将滤除了所述散射光噪声的大气散射光信号通过所述第二光环形器传输给所述 光纤光栅滤波器；所述光纤光栅滤波器配置成对滤除了所述散射光噪声的大气散射光信号进行光谱噪声滤波处理，将经所述光谱噪声滤波处理后的大气散射光信号通过所述第二光环形器传输至所述探测单元。
在一种优选的实施方式中，所述第二光环形器包括第四端口、第五端口和第六端口；所述第二光环形器配置成通过所述第四端口接收滤除了所述散射光噪声的大气散射光信号，并通过所述第五端口将滤除了所述散射光噪声的大气散射光信号传输给所述光纤光栅滤波器；所述第二光环形器还配置成通过所述第五端口接收经所述光谱噪声滤波处理后的大气散射光信号，并通过所述第六端口将经所述光谱噪声滤波处理后的大气散射光信号传输给所述探测单元。
在一种优选的实施方式中，所述光纤光栅滤波器的反射带通宽度小于1nm。
在一种优选的实施方式中，所述探测单元包括依次连接的可调光衰减器、光纤延迟线和光混频探测器。
在一种优选的实施方式中，所述可调光衰减器还与所述本机振荡光源相连；所述可调光衰减器配置成对所述本机振荡光源传输的所述本机振荡光信号进行强度调节，并将调节强度后的所述本机振荡光信号传输给所述光纤延迟线；所述光纤延迟线配置成延迟调节强度后的所述本机振荡光信号到达所述光混频探测器的时间；所述光混频探测器配置成对经所述光谱噪声滤波处理后的大气散射光信号和经延迟时间后的所述本机振荡光信号进行差拍平衡探测，并得到探测结果。
在一种优选的实施方式中，所述光混频探测器的光敏材料包括铟镓砷。
在一种优选的实施方式中，所述雷达采用全光纤结构或者非全光纤结构。
第二方面，本申请实施例还提供一种测风方法，所述方法应用于第一方面 提供的任一项所述的脉冲相干多普勒测风激光雷达，所述方法包括：所述光源发射单元向待测空域发射激光脉冲，以及向所述探测单元传输本机振荡光信号；所述信号接收单元接收大气散射光信号，以及将所述大气散射光信号传输至所述探测单元；其中，所述大气散射光信号是所述激光脉冲经所述待测空域的大气颗粒散射得到的；所述探测单元基于所述本机振荡光信号和所述大气散射光信号进行差拍平衡探测，并得到探测结果；所述信号处理单元根据所述探测结果和多普勒效应关系式计算得到风速信息。
本申请实施例提供了一种脉冲相干多普勒测风激光雷达及测风方法，该雷达包括光源发射单元、信号接收单元、探测单元和信号处理单元，其中，信号接收单元和/或探测单元中设置有至少一种噪声过滤器件，由于噪声过滤器件通过滤除噪声的方式可以较好地降低噪声对信噪比的影响，相比于现有的脉冲相干多普勒测风激光雷达，本实施例提供的雷达具有较高的信噪比，有助于进一步提升雷达的测风准确率。
本申请的其他特征和优点将在随后的说明书中阐述，或者，部分特征和优点可以从说明书推知或毫无疑义地确定，或者通过实施本公开的上述技术即可得知。
为使本申请的上述目的、特征和优点能更明显易懂，下文特举较佳实施例，并配合所附附图，作详细说明如下。
附图说明
为了更清楚地说明本申请具体实施方式或现有技术中的技术方案，下面将对具体实施方式或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1示出了本申请实施例所提供的一种脉冲相干多普勒测风激光雷达的结构示意图；
图2示出了本申请实施例所提供的一种脉冲相干多普勒测风激光雷达的具体结构示意图；
图3示出了本申请实施例所提供的一种脉冲相干多普勒测风激光雷达的光路原理图；
图4示出了本申请实施例所提供的0.8-2.2微米的大气透射光谱范围示意图；
图5示出了本申请实施例所提供的一种铟镓砷光电探测器的典型光谱响应曲线；
图6示出了本申请实施例所提供的一种测风方法流程图。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合附图对本申请的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
目前，无论是光纤结构的脉冲相干多普勒测风激光雷达，还是非光纤结构的脉冲相干多普勒测风激光雷达(诸如，将由光学镜片、激光晶体、光学镜架、等分立光学元件组成的固体激光器作为光源的激光雷达)，大多都因噪声干扰而导致信噪比较低，最终导致测风准确率不高，举例说明如下：
(1)脉冲相干多普勒测风激光雷达中大多有光混频探测器，光混频探测 器为具有一定响应光谱范围的光敏材料光电探测器，响应光谱宽度一般远远大于光信号的光谱宽度，探测到的光信号背景噪声包含部分太阳辐射光谱噪声、大气中各种不同尺度颗粒与激光束相互作用产生的杂散光噪声，从而降低了雷达系统信噪比。
(2)对于全光纤脉冲相干多普勒测风激光雷达而言，虽然结构紧凑，功耗较低，但是由于光纤截面小、光信号和噪声传播束缚在光波导内，光纤端面产生的反射信号强度远大于有效光探测信号，其中，光纤端面产生的反射信号又可称为散射光噪声，此类噪声易使光探测器饱和，也会影响信噪比，同时也降低雷达探测数据有效率。
(3)脉冲相干多普勒测风激光雷达中的本机振荡光源自身的相位/频率噪声会展宽光混频探测解析出的有效信号频谱峰宽度，从而影响信噪比，以及影响反演计算出的风速精度。
为改善上述问题至少之一，本申请实施例提供的一种脉冲相干多普勒测风激光雷达及测风方法，该技术可应用于诸如清洁风电能源开发、气象科学、民航机场空域风切变预警、风洞流体力学研究、空间大气科学研究等各种需要探测大气风场的领域。以下对本申请实施例进行详细介绍。
首先，可参见图1所示的一种脉冲相干多普勒测风激光雷达的结构示意图，包括：光源发射单元、信号接收单元、探测单元和信号处理单元；光源发射单元和信号接收单元均与探测单元相接，探测单元还与信号处理单元相接；其中，信号接收单元和/或探测单元中设置有至少一种噪声过滤器件(图1中未示出)。光源发射单元、信号接收单元、探测单元和信号处理单元的基本原理如下：
光源发射单元配置成向待测空域发射激光脉冲，还配置成向探测单元传输 本机振荡光信号。
信号接收单元配置成接收大气散射光信号，还配置成将大气散射光信号传输至探测单元；其中，大气散射光信号是激光脉冲经待测空域的大气颗粒散射得到的。
探测单元配置成基于本机振荡光信号和大气散射光信号进行差拍平衡探测，并得到探测结果。在一些实施方式中，探测单元可将本机振荡光信号和大气散射光信号进行混频，差拍平衡探测后生成模拟电信号的探测结果(可为时域模拟电信号)。
信号处理单元配置成根据探测结果和多普勒效应关系式计算得到风速信息。在一些实施方式中，信号处理单元可首先将模拟电信号转换为数字电信号，然后经快速分立傅里叶变换实现时域数据到频域数据的转换，根据多普勒效应关系式计算出实时风速数据信息。
本申请实施例提供的上述脉冲相干多普勒测风激光雷达，该雷达包括光源发射单元、信号接收单元、探测单元和信号处理单元，其中，信号接收单元和/或探测单元中设置有至少一种噪声过滤器件，由于噪声过滤器件通过滤除噪声的方式可以较好地降低噪声对信噪比的影响，相比于现有的脉冲相干多普勒测风激光雷达，本实施例提供的雷达具有较高的信噪比，有助于进一步提升雷达的测风准确率。
在一些实施方式中，信号接收单元中的噪声过滤器件可以包括快速电光开关和/或光纤光栅滤波器。信号探测单元中的噪声过滤器件可以包括光纤延迟线。在具体实施时，本申请实施例提供的噪声过滤器件可以采用快速电光开关、光纤光栅滤波器和光线延迟线中的一种或多种实现，当然也可以采用其它噪声过滤器件，在此不进行限制。
在实际应用中，本实施例提供的脉冲相干多普勒测风激光雷达可以采用全光纤结构或非全光纤结构，在此不进行限制。
在图1的基础上可参见图2示意的一种脉冲相干多普勒测风激光雷达的具体结构示意图，以及在图2基础上，还可以进一步参见图3示意的一种脉冲相干多普勒测风激光雷达的光路原理图，图2与图3的区别在于，图2中仅简单示意出激光雷达所包含的具体器件以及各器件之间的连接关系，图2中的实线仅表征两个器件之间具有关联关系。而图3在图2的基础上，进一步示意了不同器件之间的信号传输形式，诸如，图3中的实线表征两个器件之间是激光传输，虚线表征两个器件之间是待测大气回波信号(也即上述大气散射光信号)传输，点划线表征两个器件之间是电信号传输。
以下结合图2和图3，对本申请实施例提供的脉冲相干多普勒测风激光雷达进行详细说明：
光源发射单元可以包括依次连接的本机振荡光源、光调制器、光纤放大器、第一光环形器和收发同置光学天线；还包括脉冲同步信号发生器和驱动器；其中，驱动器分别与脉冲同步信号发生器和光调制器相连。为便于理解各器件的作用，具体说明如下：
本机振荡光源配置成输出两路连续激光束，将第一路激光束传输给探测单元，并将第二路激光束传输给光调制器；其中，第一路激光束作为本机振荡光信号，第二路激光束作为发射到待测空域的激光脉冲的种子源。在一种实施方式中，本机振荡光源可以为波长1.5微米(属于人眼安全光波段)的单频低噪声半导体激光。
光调制器配置成将第二路激光束调制成预设的激光脉冲(诸如，具有设定的重复频率和脉冲宽度，且调制载频为差拍探测中频)，并将激光脉冲传送至 光纤放大器；其中，脉冲同步信号发生器配置成产生同步脉冲电信号，将同步脉冲电信号传输给驱动器；驱动器配置成放大同步脉冲电信号，采用放大后的同步脉冲电信号驱动光调制器工作。
在一种实施方式中，光调制器可以采用光纤声光调制器(当然，在实际应用中，光调制器还可以采用电光调制器)，将连续激光调制成激光脉冲，脉冲重复频率和脉宽由脉冲同步信号发生器决定。脉冲同步信号发生器输出同步电脉冲信号，电脉冲的脉冲重复频率和脉冲宽度决定了激光雷达发射的脉冲光信号形状、重复频率和脉冲宽度。同步电脉冲信号可以分为两路，一路经驱动器放大后以合适的射频功率驱动光调制器，另一路可用于同步控制信号接收单元中的快速电光开关(在后文中有详细介绍，在此先不赘述)。为便于理解，进一步阐述光调制器的基本原理：光调制器对输入电信号(诸如模拟或数字TTL信号)进行调制，并经驱动器进行射频功率放大，驱动器再由标准的SMA等接口连接到光调制器的电接口上。光调制器的接口可以包括电接口和光接口，诸如，当激光由光接口进出光调制器时，光调制器内的电光晶体、声光晶体在足够的射频功率驱动下，经电光效应、声光效应对入射激光产生脉冲调制作用，从而把连续光信号转化为脉冲光信号，也即，光调制器可以将连续激光调制成一定重复频率、脉冲宽度、调制载频为差拍探测中频的激光脉冲。
光纤放大器配置成放大激光脉冲的能量，得到待发射激光脉冲，并将待发射激光脉冲通过第一光环形器传输给收发同置光学天线。在一种实施方式中，光纤放大器可以采用掺铒光纤放大器或铒镱共掺光纤放大器，用于放大激光脉冲能量，视探测距离的要求，可采用多级放大器级联的方式扩展脉冲能量。待发射激光脉冲的能量大小由雷达系统指标确定(主要是探测距离的远近)，一般根据实际雷达应用外场的试验测试确认，调节激光能量只需调节激光器的控 制电流即可。可以理解的是，大气对激光信号有衰减作用，激光能量越高，激光发射越远，而且相同距离下散射回雷达的光信号越强，转化为有用的探测信号越强。
收发同置光学天线配置成将待发射激光脉冲发射至待测空域，收发同置光学天线还配置成接收待测空域的大气颗粒散射得到的大气散射光信号，并将大气散射光信号通过第一光环形器传输给信号接收单元。具体而言，激光脉冲发射到大气中，大气中的移动气溶胶颗粒受到激光照射后，散射的光信号反射回收发同置光学天线。其中，第一光环形器与收发同置光学天线的连接方式可以为：第一光环形器的一端光纤连接器接入至收发同置光学天线的连接口并固定。激光从光纤端面射出后经过收发同置光学天线内的光学透镜、窗口镜聚焦发射到大气中，大气中移动的气溶胶粒子散射的光信号(也即，大气散射光信号)按照相反路径回到收发同置光学天线。
在具体实施时，上述第一光环形器包括第一端口C1、第二端口C2和第三端口C3；其中，第一光环形器配置成通过第一端口C1接收待发射激光脉冲，并通过第二端口C2将待发射激光脉冲传输给收发同置光学天线；第一光环形器还配置成通过第二端口C2接收大气散射光信号，并通过第三端口C3将大气散射光信号传输给信号接收单元。也即，待发射激光脉冲由第一光环形器的第一端口C1进入到第二端口C2，再经由收发同置光学天线发射到待测空域；大气散射光信号由收发同置光学天线收集后，由第一光环形器的第二端口C2进入第三端口C3，进而由第三端口C3进入后续信号接收单元。具体而言，第一光环形器是一个三端口光纤环形器，激光在端口间的单向传播方向是C1→C2，C2→C3，而C1→C3、C2→C1的传播方向是禁止的。优选的，C1和C3间光隔离度＞50dB。
信号接收单元可以包括依次连接的快速电光开关、第二光环形器和光纤光栅滤波器；其中，快速电光开关、第二光环形器和光纤光栅滤波器依次连接。进一步，快速电光开关还分别与第一光环形器和脉冲同步信号发生器相连。第一光环形器还配置成将大气散射光信号传输给快速电光开关；脉冲同步信号发生器还配置成将同步脉冲电信号传输给快速电光开关。
快速电光开关配置成按照同步脉冲电信号更改开关状态，滤除大气散射光信号中的散射光噪声，并将滤除了散射光噪声的大气散射光信号通过第二光环形器传输给光纤光栅滤波器。
光纤光栅滤波器配置成对滤除了散射光噪声的大气散射光信号进行光谱噪声滤波处理，将经光谱噪声滤波处理后的大气散射光信号通过第二光环形器传输至探测单元。光纤光栅滤波器可反射位于有效光谱范围内的光，透过非有效光谱的光，从而达到将非有效光谱的光滤除的目的。
其中，第二光环形器主要配置成将经过快速电光开关处理后的光信号引导到光纤光栅滤除器进行光谱滤波，光谱噪声滤除后，再将滤除了光谱噪声的光信号引导进入光混频探测器。具体而言，本实施例提供的第二光环形器包括第四端口C4、第五端口C5和第六端口C6；其中，第二光环形器配置成通过第四端口C4接收滤除了散射光噪声的大气散射光信号，并通过第五端口C5将滤除了散射光噪声的大气散射光信号传输给光纤光栅滤波器；第二光环形器还配置成通过第五端口C5接收经光谱噪声滤波处理后的大气散射光信号，并通过第六端口C6将经光谱噪声滤波处理后的大气散射光信号传输给探测单元。
考虑到雷达光源的谱宽通常很窄(<1nm)，本实施例提供的光纤光栅滤波器的反射带通宽度可以小于1nm，当然也可以采用其它数值，但是通常情况下，带通谱宽越宽，谱宽内其他光噪声越多；而1nm为经验值，且器件制造商可 以提供大批量性能稳定器件，有助于规模化应用。而且，本申请实施例提供的激光雷达光源的中心波长由本机振荡光源的中心波长决定，因为1550nm为光通信行业中的标准常用波长，具体精确值由于制造工艺和材料的差异，批量器件数值会有波动，一般1550±0.5nm内批量采购会容易选择。基于此，本实施例提供的光纤光栅滤波器可将波长在1550nm附近1nm光谱范围内的有效光信号反射回第二光环形器，并由第五端口C5进入第六端口C6。有效光谱范围外的背景光噪声(如图4所示为0.8-2.2微米的大气透射光谱范围)透过光纤光栅滤除器，被光纤光栅滤除器过滤掉，从而实现光谱噪声滤波的作用。
在诸如全光纤结构的激光雷达中，整个全光纤激光光源(诸如，可包含本机振荡光源、光调制器、光纤放大器、驱动器等器件)用到的器件均为光纤通信行业所用的微型光纤器件，器件连接采用光纤熔接方式，所有光信号全部在光纤内传输，没有裸露的自由空间，从而容易导致光纤端面产生的散射(或反射)信号远大于有效的大气散射光信号。基于此，本实施例设置了快速电光开关，以滤除大气散射光信号中混有的散射光噪声，具体原理如下：第一光环形器的第三端口C3接收到的光信号中包含收发同置光学天线中光纤端面和光学镜面产生的强散射光脉冲，快速电光开关可基于脉冲同步信号发生器的触发时序控制信号(对应前述同步脉冲电信号)，通过改变开关状态而隔离滤除上述强散射光脉冲(对应前述散射光噪声)。可以理解的是，雷达内部的散射光脉冲或反射光脉冲(光纤端面、望远镜内的光学镜面、发射光学窗口均可产生，信号很强)与远距离大气中颗粒散射的回波光信号(也即前述大气散射光信号，信号很弱)有一定时间差，雷达内部的散射光脉冲先到达快速电光开关，此时只要快速电光开关处于OFF状态，即可将散射光脉冲挡住，而大气散射光信号延迟到达，快速电光开关再将OFF状态更换为ON状态，ON状态的持续时 间可稍大于光脉冲信号持续时间(一般为100ns量级)。由于需要开关ON/OFF的更换速度较快(诸如，一般要求<10ns)，因此可选用相应的快速电光开关实现。
本实施例提供的探测单元可以包括依次连接的可调光衰减器、光纤延迟线和光混频探测器。而且，可调光衰减器还与本机振荡光源相连。
可调光衰减器配置成对本机振荡光源传输的本机振荡光信号进行强度调节，并将调节强度后的本机振荡光信号传输给光纤延迟线。
光纤延迟线配置成延迟调节强度后的本机振荡光信号到达光混频探测器的时间。
光混频探测器配置成对经光谱噪声滤波处理后的大气散射光信号和经延迟时间后的本机振荡光信号进行差拍平衡探测，并得到探测结果，并将探测结果传输给信号处理单元。其中，光混频探测器可采用铟镓砷(InGaAs)为主要光敏材料的光电探测器，铟镓砷(InGaAs)的典型光谱响应曲线如图5所示，亦可见响应光谱范围较宽，从而也可证明前述大气散射光信号经光谱滤波的有效性，也即，光信号中心波长外的宽光谱噪声在探测前即可被高效滤除。
可以理解的是，脉冲相干多普勒测风激光雷达主要利用相干探测原理测量风速数据，具体而言，本机振荡光信号(自身也携带有光噪声)和大气散射光信号(含有其它杂散光噪声以及反映风速的散射光信号等)混频后，光混频探测器输出模拟电信号，而可反映风速的精确多普勒频率差可以通过对此模拟电信号进行高精度数字采样后解析出来。本申请实施例首先能够利用布设在雷达系统中的各噪声滤波器件对本机振荡光信号和大气散射光信号进行滤波处理，从而提升雷达信噪比，有助于进一步提升测风准确率。其中，光纤延迟线也是一种噪声滤波器件，本申请实施例提供的光纤延迟线的基本原理为：本机振荡 光信号和大气散射光信号(也是本机振荡光信号的能量经放大后照射到大气颗粒上，然后又散射回来的信号)的自身频率或相位噪声是和时间相关的，如果某一瞬态时刻，本机振荡光信号和大气散射光信号具有相同的瞬态相位或频率，则混频后的相干探测灵敏度和效率会更佳。为了能够更好的使本机振荡光信号和大气散射光信号具有相同的瞬态相位或频率，在本申请实施例中，主要采用光纤延迟线延迟本机振荡光信号，尽量使本机振荡光信号和大气散射光信号具有相同的瞬态相位或频率，从而降低本机振荡光源的频率噪声对信噪比的影响。而且，采用光纤延迟线延迟本机振荡光信号的方式，相比于延迟大气散射光信号(本身极弱)的方式，能够更好的降低损耗，同时也可以使雷达系统的结构更合理。
最后，信号处理单元可以将作为探测结果(时域模拟电信号)转换为模拟数字信号，经快速分立傅里叶变换实现时域数据到频域数据的变换，还可根据不同的频谱噪声处理算法，计算出实时风速数据信息。
如图2和图3所示的脉冲相干多普勒测风激光雷达，利用一些光纤有源和无源器件的组合，可集中对脉冲相干多普勒测风激光雷达中的几个主要影响信噪比的噪声源进行滤除，诸如，因设置了光纤延迟线，可减少本机振荡光源自身的相位/频率噪声的影响，可进一步放宽相关器件的选型范围和技术规格要求，还有助于降低成本。因设置了快速光电开关，可有效降低光纤端面产生的散射光噪声；因设置了光纤光栅滤波器，可有效过滤掉掉有效光谱范围外的背景光噪声。通过在激光雷达的结构中布设这些噪声过滤器件，能够较好的滤除影响信噪比的不同噪声，从而有效提升雷达的信噪比，以及雷达的测风准确率。
本实施例还提供了一种测风方法，该方法应用于本实施例提供的前述任一种脉冲相干多普勒测风激光雷达，如图6所示的一种测风方法流程图，该方法 包括：
步骤S602，光源发射单元向待测空域发射激光脉冲，以及向探测单元传输本机振荡光信号；
步骤S604，信号接收单元接收大气散射光信号，以及将大气散射光信号传输至探测单元；其中，大气散射光信号是激光脉冲经待测空域的大气颗粒散射得到的；
步骤S606，探测单元基于本机振荡光信号和大气散射光信号进行差拍平衡探测，并得到探测结果；
步骤S608，信号处理单元根据探测结果和多普勒效应关系式计算得到风速信息。
由于本实施例提供的上述测风方法是采用本实施例提供的前述任一种脉冲相干多普勒测风激光雷达实现的，信号接收单元和/或探测单元中设置有至少一种噪声过滤器件，通过滤除噪声的方式可以较好地降低噪声对信噪比的影响，有助于进一步提升雷达的测风准确率。
所属领域的技术人员可以清楚地了解到，为描述的方便和简洁，上述描述的采用脉冲相干多普勒测风激光雷达进行测风的具体工作过程，以及脉冲相干多普勒测风激光雷达中各器件在测风过程中的主要作用，可以参考前述实施例中的对应过程，在此不再赘述。
在本申请实施例的描述中，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以具体情况理解上述术语在本申请中的具体含义。
在本申请的描述中，需要说明的是，术语“中心”、“上”、“下”、“左”、“右”、“竖直”、“水平”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。此外，术语“第一”、“第二”、“第三”仅用于描述目的，而不能理解为指示或暗示相对重要性。
最后应说明的是：以上所述实施例，仅为本申请的具体实施方式，用以说明本申请的技术方案，而非对其限制，本申请的保护范围并不局限于此，尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，其依然可以对前述实施例所记载的技术方案进行修改或可轻易想到变化，或者对其中部分技术特征进行等同替换；而这些修改、变化或者替换，并不使相应技术方案的本质脱离本申请实施例技术方案的精神和范围，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以所述权利要求的保护范围为准。
工业实用性：
通过应用本申请的技术方案，能够较好的过滤噪声，有助于提升雷达的信噪比和测风准确率。

Claims (18)

  1. 一种脉冲相干多普勒测风激光雷达，其特征在于，包括：光源发射单元、信号接收单元、探测单元和信号处理单元；所述光源发射单元和所述信号接收单元均与所述探测单元相接，所述探测单元还与所述信号处理单元相接；其中，所述信号接收单元和/或所述探测单元中设置有至少一种噪声过滤器件；
    所述光源发射单元配置成向待测空域发射激光脉冲，还配置成向所述探测单元传输本机振荡光信号；
    所述信号接收单元配置成接收大气散射光信号，还配置成将所述大气散射光信号传输至所述探测单元；其中，所述大气散射光信号是所述激光脉冲经所述待测空域的大气颗粒散射得到的；
    所述探测单元配置成基于所述本机振荡光信号和所述大气散射光信号进行差拍平衡探测，并得到探测结果；
    所述信号处理单元配置成根据所述探测结果和多普勒效应关系式计算得到风速信息。
  2. 根据权利要求1所述的雷达，其特征在于，所述信号接收单元中的噪声过滤器件包括快速电光开关和/或光纤光栅滤波器。
  3. 根据权利要求1或2所述的雷达，其特征在于，所述信号探测单元中的噪声过滤器件包括光纤延迟线。
  4. 根据权利要求1至3任一项所述的雷达，其特征在于，所述光源发射单元包括依次连接的本机振荡光源、光调制器、光纤放大器、第一光环形器和收发同置光学天线；还包括脉冲同步信号发生器和驱动器；其中，所述驱动器分别与所述脉冲同步信号发生器和所述光调制器相连。
  5. 根据权利要求4所述的雷达，其特征在于，所述本机振荡光源配置成 输出两路连续激光束，将第一路激光束传输给所述探测单元，并将第二路激光束传输给所述光调制器；其中，所述第一路激光束作为所述本机振荡光信号，所述第二路激光束作为发射到所述待测空域的激光脉冲的种子源；
    所述光调制器配置成将所述第二路激光束调制成预设的激光脉冲，并将所述激光脉冲传送至所述光纤放大器；其中，所述脉冲同步信号发生器配置成产生同步脉冲电信号，将所述同步脉冲电信号传输给所述驱动器；所述驱动器配置成放大所述同步脉冲电信号，采用放大后的所述同步脉冲电信号驱动所述光调制器工作；
    所述光纤放大器配置成放大所述激光脉冲的能量，得到待发射激光脉冲，并将所述待发射激光脉冲通过所述第一光环形器传输给所述收发同置光学天线；
    所述收发同置光学天线配置成将所述待发射激光脉冲发射至待测空域，所述收发同置光学天线还配置成接收所述待测空域的大气颗粒散射得到的大气散射光信号，并将所述大气散射光信号通过所述第一光环形器传输给所述信号接收单元。
  6. 根据权利要求5所述的雷达，其特征在于，所述第一光环形器包括第一端口、第二端口和第三端口；
    所述第一光环形器配置成通过所述第一端口接收所述待发射激光脉冲，并通过所述第二端口将所述待发射激光脉冲传输给所述收发同置光学天线；
    所述第一光环形器还配置成通过所述第二端口接收所述大气散射光信号，并通过所述第三端口将所述大气散射光信号传输给所述信号接收单元。
  7. 根据权利要求6所述的雷达，其特征在于，所述第一端口和所述第三端口之间的光隔离度大于50dB。
  8. 根据权利要求4或5所述的雷达，其特征在于，所述本机振荡光源为单频低噪声半导体激光源；
    和/或，
    所述光调制器为光纤声光调制器或光纤电光调制器；
    和/或，
    所述光纤放大器为掺铒光纤放大器或铒镱共掺光纤放大器。
  9. 根据权利要求5所述的雷达，其特征在于，所述信号接收单元包括快速电光开关。
  10. 根据权利要求9所述的雷达，其特征在于，所述信号接收单元还包括第二光环形器和光纤光栅滤波器；其中，所述快速电光开关、所述第二光环形器和所述光纤光栅滤波器依次连接。
  11. 根据权利要求10所述的雷达，其特征在于，所述快速电光开关还分别与所述第一光环形器和所述脉冲同步信号发生器相连；所述第一光环形器还配置成将所述大气散射光信号传输给所述快速电光开关；所述脉冲同步信号发生器还配置成将所述同步脉冲电信号传输给所述快速电光开关；
    所述快速电光开关配置成按照所述同步脉冲电信号更改开关状态，滤除所述大气散射光信号中的散射光噪声，并将滤除了所述散射光噪声的大气散射光信号通过所述第二光环形器传输给所述光纤光栅滤波器；
    所述光纤光栅滤波器配置成对滤除了所述散射光噪声的大气散射光信号进行光谱噪声滤波处理，将经所述光谱噪声滤波处理后的大气散射光信号通过所述第二光环形器传输至所述探测单元。
  12. 根据权利要求11所述的雷达，其特征在于，所述第二光环形器包括第四端口、第五端口和第六端口；
    所述第二光环形器配置成通过所述第四端口接收滤除了所述散射光噪声的大气散射光信号，并通过所述第五端口将滤除了所述散射光噪声的大气散射光信号传输给所述光纤光栅滤波器；
    所述第二光环形器还配置成通过所述第五端口接收经所述光谱噪声滤波处理后的大气散射光信号，并通过所述第六端口将经所述光谱噪声滤波处理后的大气散射光信号传输给所述探测单元。
  13. 根据权利要求10至12任一项所述的雷达，其特征在于，所述光纤光栅滤波器的反射带通宽度小于1nm。
  14. 根据权利要求11至13任一项所述的雷达，其特征在于，所述探测单元包括依次连接的可调光衰减器、光纤延迟线和光混频探测器。
  15. 根据权利要求14所述的雷达，其特征在于，所述可调光衰减器还与所述本机振荡光源相连；所述可调光衰减器配置成对所述本机振荡光源传输的所述本机振荡光信号进行强度调节，并将调节强度后的所述本机振荡光信号传输给所述光纤延迟线；
    所述光纤延迟线配置成延迟调节强度后的所述本机振荡光信号到达所述光混频探测器的时间；
    所述光混频探测器配置成对经所述光谱噪声滤波处理后的大气散射光信号和经延迟时间后的所述本机振荡光信号进行差拍平衡探测，并得到探测结果。
  16. 根据权利要求14或15所述的雷达，其特征在于，所述光混频探测器的光敏材料包括铟镓砷。
  17. 根据权利要求1至16任一项所述的雷达，其特征在于，所述雷达采用全光纤结构或非全光纤结构。
  18. 一种测风方法，其特征在于，所述方法应用于权利要求1至17任一项所述的脉冲相干多普勒测风激光雷达，所述方法包括：
    所述光源发射单元向待测空域发射激光脉冲，以及向所述探测单元传输本机振荡光信号；
    所述信号接收单元接收大气散射光信号，以及将所述大气散射光信号传输至所述探测单元；其中，所述大气散射光信号是所述激光脉冲经所述待测空域的大气颗粒散射得到的；
    所述探测单元基于所述本机振荡光信号和所述大气散射光信号进行差拍平衡探测，并得到探测结果；
    所述信号处理单元根据所述探测结果和多普勒效应关系式计算得到风速信息。
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