CN110456383B - Molecular scattering coherent laser radar system - Google Patents
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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
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Abstract
The application provides a coherent laser radar system of molecular scattering, this coherent laser radar system of molecular scattering adopts coherent detection's mode, detects the molecular scattering spectral line in the atmosphere backscattering signal, through handling the molecular scattering spectral line, can realize measuring simultaneously to wind speed and temperature.
Description
Technical Field
The invention relates to the technical field of laser radars, in particular to a molecular scattering coherent laser radar system.
Background
In the field of atmospheric detection, a doppler laser radar for atmospheric wind field detection generally adopts two modes of direct detection and coherent detection.
Wherein, the elastic scattering of atmospheric molecules or aerosol is directly detected, the Doppler frequency change is converted into intensity change through molecular absorption or a high-precision narrow-band frequency discriminator, and the Doppler frequency shift is calculated through detecting the intensity change; coherent detection adopts backward scattering light of aerosol particles and continuous local oscillation light to carry out beat frequency, and Doppler frequency shift can be directly obtained by detecting beat frequency signals.
However, since aerosol components in the atmosphere are mainly distributed in a low altitude range such as a boundary layer, the detection altitude of the coherent doppler lidar is limited to a certain extent. Compared with a narrow-band rice scattering signal, the spectral width of Rayleigh scattering caused by thermal motion is wider, and certain difficulty is brought to beat frequency and detection of the signal if the Rayleigh scattering is applied to coherent detection.
For the detection of atmospheric temperature, the currently common laser radar technology mainly comprises a rotating Raman technology, an integration technology, a resonance fluorescence technology and the like, wherein the rotating Raman technology utilizes the dependency relationship between the temperature and the rotating Raman line intensity to invert the temperature; the integration technology is to calculate the number density of molecules and then calculate the atmospheric temperature; the resonance fluorescence technology utilizes the Doppler broadening of the resonance fluorescence of metal atoms by temperature to invert the temperature. In addition, the differential absorption technique and the brillouin-doppler technique measure temperature by the intensity of a molecular scattering signal or doppler spread effect, rather than directly detecting the spectral width of the molecular scattering signal.
At present, fewer laser radar systems capable of simultaneously measuring wind speed and temperature are available, and no relevant report is provided for the laser radar system capable of simultaneously measuring wind speed and temperature by directly measuring molecular scattering spectral lines.
Disclosure of Invention
In view of the above, in order to solve the above problems, the present invention provides a molecular scattering coherent lidar system, which has the following technical scheme:
a molecular scattering coherent lidar system, comprising:
the device comprises an optical fiber seed laser, a polarization-maintaining optical fiber beam splitter, an acousto-optic modulator, a main laser, a beam expanding lens, a polarization beam splitting prism, a quarter-wave plate, a coupling lens, an optical fiber adjusting frame, an optical fiber coupler, a balanced photoelectric detector, an amplification module, an analog-to-digital conversion data acquisition device and a beam expanding telescope;
the optical fiber seed laser is used for outputting single longitudinal mode continuous light;
the optical fiber beam splitter is used for splitting the single longitudinal mode continuous light into seed light and local oscillation light according to a preset proportion under the condition of ensuring that the polarization state of the single longitudinal mode continuous light is not changed;
the acousto-optic modulator is used for carrying out frequency shift on the seed light;
the main laser is used for outputting pulsed light;
the beam expander is used for expanding the pulse light and compressing a divergence angle;
the coupling lens is used for coupling the atmosphere backscattered light to the optical fiber coupler;
the polarization beam splitter prism and the quarter wave plate form an optical receiving and transmitting switch, only P polarized light is allowed to penetrate, and S polarized light is reflected on the beam splitting surface;
the quarter wave plate is used for adjusting the polarization states of the emitted laser and the atmosphere backward scattering light;
the optical fiber coupler receives the atmospheric backscattered light and the local oscillator light and couples the atmospheric backscattered light and the local oscillator light to the balanced photoelectric detector;
the balance photoelectric detector is used for converting a beat frequency signal obtained by mixing the atmospheric back scattering light and the local oscillator light into an electric signal;
the amplifying module is used for amplifying the electric signal;
the analog-to-digital conversion data acquisition device is used for converting the amplified electric signals into digital signals.
Preferably, in the above molecular scattering coherent lidar system, the fiber seed laser is configured to output a single longitudinal mode continuous light with a wavelength of 1064 nm.
Preferably, in the above molecular scattering coherent lidar system, the optical fiber beam splitter is configured to split the single longitudinal mode continuous light into the local oscillation light and the seed light according to a ratio of 1 to 99, under a condition that a polarization state of the single longitudinal mode continuous light is guaranteed to be unchanged;
wherein, 99% of light is used as seed light, and 1% of light is used as local oscillator light.
Preferably, in the above molecular scattering coherent lidar system, the acousto-optic modulator is an all-fiber frequency shift element, and the frequency shift amount is 1 GHz.
Preferably, in the molecular scattering coherent lidar system, the primary laser is a seed injection diode pumped Nd: YAG laser.
Preferably, in the above molecular scattering coherent lidar system, the amplification module comprises: a low noise preamplifier and a low noise amplifier;
wherein the electrical signal passes through the low noise preamplifier and the low noise amplifier in sequence to amplify the electrical signal.
Preferably, in the above molecular scattering coherent lidar system, the beam expanding telescope is an off-axis reflective beam expanding telescope;
and the reflecting surface of the beam expanding telescope is plated with a high-reflection dielectric film.
Preferably, in the above molecular scattering coherent lidar system, the beam expanding telescope comprises: a primary mirror and a secondary mirror.
Compared with the prior art, the invention has the following beneficial effects:
the molecular scattering coherent laser radar system detects the molecular scattering spectral line in the atmosphere backscattering signal by adopting a coherent detection mode, and can realize the simultaneous measurement of the wind speed and the temperature by processing the molecular scattering spectral line.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a molecular scattering coherent lidar system according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a molecular scattering coherent lidar system according to an embodiment of the present invention.
The molecular scattering coherent lidar system includes:
the device comprises an optical fiber seed laser 1, a polarization-maintaining optical fiber beam splitter 2, an acousto-optic modulator 3, a main laser 4, a beam expander 5, a polarization beam splitter prism 6, a quarter-wave plate 7, a coupling lens 8, an optical fiber adjusting frame 9, an optical fiber coupler 10, a balanced photoelectric detector 11, an amplifying module 12, an analog-to-digital conversion data acquisition device 15 and a beam expander telescope 18;
the optical fiber seed laser 1 is used for outputting single longitudinal mode continuous light;
the polarization-maintaining optical fiber beam splitter 2 is used for splitting the single longitudinal mode continuous light into seed light and local oscillation light according to a preset proportion under the condition of ensuring that the polarization state of the single longitudinal mode continuous light is not changed;
the acousto-optic modulator 3 is used for carrying out frequency shift on the seed light;
the main laser 4 is used for outputting pulsed light;
the beam expander 5 is used for expanding the pulse light and compressing the divergence angle;
the polarization beam splitter prism 6 and the quarter-wave plate 7 form an optical transceiving switch, only P polarized light is allowed to transmit, and S polarized light is reflected on the beam splitting surface;
the quarter wave plate 7 is used for adjusting the polarization states of the emitted laser and the atmosphere backscattered light;
the coupling lens 8 is used for coupling the atmosphere backscattered light to the optical fiber coupler;
the optical fiber coupler 10 receives the atmospheric backscattered light and the local oscillator light, and couples the atmospheric backscattered light and the local oscillator light to the balanced photoelectric detector;
the balance photoelectric detector 11 is configured to convert a beat signal obtained by mixing the atmospheric backscattered light and the local oscillator light into an electrical signal;
the amplifying module 12 is used for amplifying the electrical signal;
the analog-to-digital conversion data acquisition device 15 is used for converting the amplified electric signal into a digital signal.
In the embodiment, a coherent detection mode is adopted to detect the molecular scattering spectral line of the atmospheric backscattered light, and the simultaneous measurement of the wind speed and the temperature can be realized by processing the molecular scattering spectral line.
Further, based on the above embodiment of the present invention, the fiber seed laser 1 is used to output a single longitudinal mode continuous light with a wavelength of 1064 nm.
In this embodiment, the seed laser is a narrow linewidth fiber laser, and is mainly used to output a single longitudinal mode continuous light with a wavelength of 1064nm as a seed light source.
Further, based on the above embodiment of the present invention, the primary laser 4 is a seed injection diode pumped Nd: YAG laser.
In this embodiment, the master laser is configured to output pulsed light having a wavelength of 1064 nm. Coherent lidar systems typically operate in the near infrared band (1 μm, 1.5 μm-1.6 μm, or 2 μm), and coherent radars typically use long wavelengths of 1 μm or more, since optical coherent beat frequencies are more easily achieved in the long wavelength band.
In order to realize that the system can reach a higher detection range compared with the traditional coherent radar, the laser is required to provide output energy of hundreds of mJ magnitude.
Compared with the 1.5 μm or 2 μm wave band, the fiber laser with the wavelength of 1064nm can provide higher output power and single pulse energy, and in addition, the backscattering intensity of the molecules with the wavelength of 1064nm is stronger because the backscattering intensity of the molecules is inversely proportional to the fourth power of the wavelength.
In the present application, the detection object of the molecular scattering coherent lidar system is a molecular scattering spectrum, the laser wavelength is 1064nm, the main component of the molecular scattering spectrum is rayleigh scattering, and the full width at half maximum (FWHM) of the atmospheric backscattering spectrum satisfies the following formula:
wherein Δ v is the full width at half maximum of the atmospheric backscattering spectrum; k is Boltzmann constant; t is the atmospheric temperature; λ is the laser wavelength; m is the average mass of a single air molecule.
The full width at half maximum of the atmospheric backscattering spectrum is 1.2GHz, which is far larger than the bandwidth of aerosol scattering.
Further, based on the above embodiment of the present invention, the polarization maintaining fiber beam splitter 2 is a 1 × 2 polarization maintaining fiber beam splitter, and is configured to divide the single longitudinal mode continuous light into the local oscillation light and the seed light according to a ratio of 1 to 99 under the condition that the polarization state of the single longitudinal mode continuous light is not changed; wherein, 99% of light is used as seed light, and 1% of light is used as local oscillator light.
The seed light is used for entering the acousto-optic modulator to carry out frequency shift, and the frequency shift light is injected into the main laser to generate laser pulses.
The local oscillator light is used for being mixed with atmosphere backward scattering light to generate beat frequency signals.
Further, based on the above embodiment of the present invention, the acousto-optic modulator 3 is an all-fiber frequency shift element, and is used for performing frequency shift on the seed light so as to determine the wind speed direction in the wind measurement application.
The bandwidth requirement of the molecular scattering spectrum to be detected is very wide, so the frequency shift amount of the acousto-optic modulator is designed to be 1 GHz.
Further, based on the above embodiment of the present invention, the beam expander 5 is configured to perform beam expanding processing on the pulsed light output by the main laser, and output the pulsed light to the polarization splitting prism after beam expanding and collimating by using a divergence angle of the compressor.
Further, based on the above embodiment of the present invention, the polarization beam splitter prism 6 and the quarter-wave plate 7 constitute an optical transceiving switch. Only p-polarized light is allowed to pass through, and s-polarized light is reflected at the spectroscopic surface.
The quarter-wave plate 7 is used to adjust the polarization state of the outgoing laser light and the atmospheric backscattered light.
Further, based on the above embodiment of the present invention, the optical fiber coupler 10 is a 2 × 2 polarization maintaining optical fiber coupler.
The optical fiber coupler receives the atmospheric backscattered light and the local oscillator light, couples the atmospheric backscattered light and the local oscillator light to the balanced photoelectric detector, and performs signal detection after the surface of the balanced photoelectric detector performs beat frequency, so that the polarization state of transmitted light is ensured to be unchanged.
Further, based on the above embodiment of the present invention, the balanced photodetector 11 is configured to convert a beat signal obtained by mixing the atmospheric backscattered light and the local oscillator light into an electrical signal.
The mode of adopting balanced detection can eliminate the extra intensity noise of local oscillator light, strengthen the intermediate frequency signal, improve the SNR. And, can all receive the optical energy of optic fibre output, make full use of local oscillator optical power.
Atmospheric backscattered light signal detection is a relatively weak signal detection, typically requiring a balanced photodetector with a relatively high responsivity, transimpedance gain, a relatively high saturation power threshold, and a sufficiently high corresponding bandwidth of 3 dB.
The full width at half maximum of a Rayleigh scattering spectrum corresponding to the wavelength of 1064nm is about 1.2GHz, and the bandwidth of the balance detector is designed to be 5GHz after the frequency shift amount of the acousto-optic modulator and the Doppler frequency shift corresponding to the wind speed measurement range are comprehensively considered.
Further, based on the above embodiment of the present invention, the amplifying module 12 includes: a low noise preamplifier 13 and a low noise amplifier 14;
wherein the electrical signal passes through the low noise preamplifier and the low noise amplifier in sequence to amplify the electrical signal.
In this embodiment, the molecular scattering spectrum signal obtained by the coherent detection system has a wide bandwidth and a very weak signal, and is likely to be buried in noise, and in order to observe a complete signal to further effectively extract the spectrum signal, the low-noise preamplifier and the low-noise amplifier in this application have the characteristics of low noise, wide operating frequency range and high power gain.
The power gain of the low-noise preamplifier is 40dB, and the working frequency range is 10kHz-2 GHz.
The power gain of the low-noise amplifier is 27dB, and the working frequency range is 50MHz-5 GHz.
Further, based on the above embodiment of the present invention, the analog-to-digital conversion data acquisition device 15 is configured to convert the amplified analog-to-digital signal into a digital signal.
The analog bandwidth of the analog-to-digital conversion data acquisition device is larger than the highest frequency of the sampling signal, and the adopted frequency is determined according to the Nyquist sampling theorem.
The sampling frequency of the analog-to-digital conversion data acquisition device is 10 GHz.
Further, based on the above embodiment of the present invention, the beam expanding telescope 18 is an off-axis reflective beam expanding telescope; and the reflecting surface of the beam expanding telescope is plated with a high-reflection dielectric film.
The beam expanding telescope 18 includes: the primary mirror 17 and the secondary mirror 16 have an effective aperture of 150mm, and are used for expanding and collimating the output light, transmitting the expanded and collimated light into the atmosphere, and receiving the atmosphere backscatter signal.
Based on all the above embodiments of the present invention, the working principle and flow of the molecular scattering coherent lidar system will be described below by way of example.
As shown in fig. 1, the fiber seed laser emits continuous linear polarization light with a wavelength of 1064nm, and is split into two beams at a ratio of 1: 99 by a 1 × 2 polarization maintaining fiber beam splitter.
Wherein, a small part of continuous light is taken as local oscillation light, is led out from a port b of the 1 multiplied by 2 polarization-maintaining optical fiber beam splitter, enters the 2 multiplied by 2 polarization-maintaining optical fiber coupler from a port d of the 2 multiplied by 2 polarization-maintaining optical fiber coupler, is split into a balanced photoelectric detector by the 2 multiplied by 2 polarization-maintaining optical fiber coupler according to the proportion of 1 to 1 after beat frequency of atmosphere backscattered light signals is carried out, and is subjected to signal detection
Most continuous light is used as seed light, enters the acousto-optic modulator from the port a of the 1 multiplied by 2 polarization-maintaining optical fiber beam splitter for frequency shift, the frequency shift amount is 1GHz, and the seed light after frequency shift enters the main laser to output pulse light with the wavelength of 1064.
Pulse light output by the main laser is expanded by the beam expander, the divergence angle is compressed, and the pulse light after beam expansion and collimation is guided into the polarization beam splitter prism.
The installation direction of the polarization beam splitter prism needs to enable the linearly polarized light emitted by the main laser to be projected, the transmitted light is guided into the quarter-wave plate, and is changed into the circularly polarized light after passing through the quarter-wave plate, and then enters the beam expanding telescope.
The beam expanding telescope adopts an off-axis reflection type beam expanding telescope, consists of a secondary mirror and a primary mirror, both are parabolic reflectors, the reflecting surfaces of the parabolic reflectors are plated with high-reflection dielectric films, and the reflectivity is more than or equal to 99.5 percent.
The transmission light is incident to the secondary mirror, transmitted and reflected, and then incident to the primary mirror, the primary mirror is used for collimating and expanding the light beam, and the expanded parallel light enters the atmosphere and interacts with the atmosphere to generate atmosphere backscattered light.
Atmospheric back scattering light is collected by the beam expanding telescope through the same optical path, then is changed into linearly polarized light through the quarter-wave plate, and the polarization direction of the linearly polarized light and the polarization direction of laser emitted by the main laser form 90 degrees, so that the atmospheric back scattering light is reflected when passing through the polarization beam splitting prism.
The parallel reflected light is incident into the coupling lens to be converged and is coupled into the 2 x 2 polarization-maintaining fiber coupler through the c port of the 2 x 2 polarization-maintaining fiber coupler.
The optical fiber adjusting frame is used for adjusting the position of the optical fiber head so as to couple all the atmosphere back scattered light to the 2 x 2 polarization-maintaining optical fiber coupler.
The atmospheric back scattering light and the local oscillator light are mixed in a 2 x 2 polarization-maintaining optical fiber coupler, the mixed signal is divided into two beams according to the proportion of 1 to 1 and enters a balanced photoelectric detector, and the signal detection is carried out after the surface of the balanced photoelectric detector carries out beat frequency.
The electric signal output by the balanced photoelectric detector enters an amplification module to be amplified, the signal is firstly amplified by a low-noise preamplifier, the power gain is 40dB, and the output signal is amplified by the low-noise amplifier, and the power gain is 27 dB.
The fully amplified signals are acquired by an analog-to-digital conversion data acquisition device, continuous analog electric signals are converted into discrete digital signals, and the sampling frequency is 10 GHz.
And analyzing and processing the data of the sampled discrete data signals, and combining a corresponding algorithm to obtain atmospheric parameters such as wind speed, temperature and the like.
According to the description, the molecular scattering coherent laser radar system provided by the application detects the molecular scattering spectrum in a coherent detection mode, is a brand new detection technology in the fields of wind measurement and temperature measurement laser radars, and has no relevant report at home and abroad.
Compared with the traditional molecular scattering laser radar, the method has the advantages that the frequency change is not required to be converted into the intensity change for measurement, the molecular scattering spectrum is directly measured, the Doppler signal is analyzed in the frequency domain, corresponding parameters can be obtained after data processing, and the measurement accuracy is higher.
Because the detection object is the molecular scattering of wide spectrum, different from the measurement of the narrow-band aerosol scattering of the traditional coherent detection, the molecular scattering distribution range is wider, and the detection height range is not limited to the bottom layer atmosphere such as a boundary layer.
In addition, the bandwidth of the molecular scattering spectrum is considered to be very large, so that the widths of the balanced photoelectric detector, the amplification module and the analog-to-digital conversion data acquisition device are all larger than 2GHz, and the measurement of wide-spectrum signals can be realized.
And considering that the molecular scattering signal detected by the coherent detection system is very weak, a secondary amplification module consisting of a low-noise preamplifier and a low-noise amplifier is designed, so that the power gain is very high while the noise is suppressed, and the detection and extraction of the weak signal are realized.
The above detailed description of the molecular scattering coherent lidar system provided by the present invention applies specific examples to illustrate the principle and the implementation of the present invention, and the above description of the embodiments is only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
It should be noted that, in the present specification, the embodiments are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include or include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. A molecular scattering coherent lidar system, comprising:
the device comprises an optical fiber seed laser, a polarization-maintaining optical fiber beam splitter, an acousto-optic modulator, a main laser, a beam expanding lens, a polarization beam splitting prism, a quarter-wave plate, a coupling lens, an optical fiber adjusting frame, an optical fiber coupler, a balanced photoelectric detector, an amplification module, an analog-to-digital conversion data acquisition device and a beam expanding telescope;
the optical fiber seed laser is used for outputting single longitudinal mode continuous light;
the polarization maintaining optical fiber beam splitter is used for splitting seed light and local oscillation light according to a preset proportion under the condition of ensuring that the polarization state of the single longitudinal mode continuous light is not changed;
the acousto-optic modulator is used for carrying out frequency shift on the seed light, wherein the acousto-optic modulator is an all-fiber frequency shift element, and the frequency shift amount is 1 GHz;
the main laser is used for outputting pulsed light;
the beam expander is used for expanding the pulse light and compressing a divergence angle;
the polarization beam splitter prism and the quarter wave plate form an optical receiving and transmitting switch, only P polarized light is allowed to penetrate, and S polarized light is reflected on the beam splitting surface;
the quarter-wave plate is used for adjusting the polarization states of the emitted laser and the atmosphere backscattered light;
the coupling lens is used for coupling the atmosphere backscattered light to the optical fiber coupler;
the optical fiber coupler receives the atmospheric backscattered light and the local oscillator light and couples the atmospheric backscattered light and the local oscillator light to the balanced photoelectric detector;
the balance photoelectric detector is used for converting a beat frequency signal obtained by mixing the atmospheric back scattering light and the local oscillator light into an electric signal, and the bandwidth of the balance detector is 5 GHz;
the amplifying module is used for amplifying the electric signal;
the analog-to-digital conversion data acquisition device is used for converting the amplified electric signals into digital signals, and the sampling frequency of the analog-to-digital conversion data acquisition device is 10 GHz.
2. The system according to claim 1, wherein the fiber seed laser is configured to output single longitudinal mode continuous light at a wavelength of 1064 nm.
3. The molecular scattering coherent lidar system of claim 1, wherein the fiber splitter is configured to split the single longitudinal mode continuous light into the local oscillator light and the seed light according to a ratio of 1 to 99 under a condition that a polarization state of the single longitudinal mode continuous light is guaranteed to be unchanged;
wherein, 99% of light is used as seed light, and 1% of light is used as local oscillator light.
4. The molecular scattering coherent lidar system of claim 1, wherein the primary laser is a seed injection diode pumped Nd: YAG laser.
5. The molecular scattering coherent lidar system of claim 1, wherein the amplification module comprises: a low noise preamplifier and a low noise amplifier;
wherein the electrical signal passes through the low noise preamplifier and the low noise amplifier in sequence to amplify the electrical signal.
6. The molecular scattering coherent lidar system of claim 1, wherein the beam expanding telescope is an off-axis reflective beam expanding telescope;
and the reflecting surface of the beam expanding telescope is plated with a high-reflection dielectric film.
7. The molecular scattering coherent lidar system of claim 1, wherein the beam expanding telescope comprises: a primary mirror and a secondary mirror.
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