Atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual-comb

Abstract

A laser radar system for measuring atmospheric greenhouse gases based on electro-optical modulation dual optical combs, the system comprises a continuous laser, a first coupler, a first electro-optical phase modulator, a second electro-optical phase modulator, a first acousto-optic frequency shifter, a second acousto-optic frequency shifter, a first multi-channel optical filter, a second multi-channel optical filter, a first radio frequency signal generator, a second radio frequency signal generator, a second coupler, a first optical fiber amplifier, a modulation chopper, a second optical fiber amplifier, a third coupler, a circulator, a telescope, an optical fiber attenuator, a fourth coupler, a photodetector, an electronic amplifier, an electronic filter, an analog data acquisition card, a trigger control unit and a data processing unit. The present invention utilizes the method of simultaneously emitting two optical combs with different repetition frequencies from the same absorption line of the greenhouse gas to be measured, and utilizes the dual optical comb spectrum detection technology to obtain the absorption information of multiple points of the atmospheric greenhouse gas absorption line, and finally achieves high-precision acquisition of the atmospheric greenhouse gas concentration while obtaining the atmospheric temperature and pressure information.

Description

Technical Field

[0001] The present invention belongs to the field of laser radar, and in particular relates to an atmospheric greenhouse gas measurement laser radar system based on electro-optical modulation dual light comb. Background Art

[0002] With the development of modernization, fossil fuel combustion, industrial emissions, and land type changes caused by human activities have caused great changes in the global atmosphere, especially in the atmospheric CO 2 , CH 4 and N 2 Greenhouse gases such as O have an immeasurable impact on global climate change, and there is a strong demand for the detection of major atmospheric greenhouse gases.

[0003] At present, there are two main methods for detecting atmospheric greenhouse gases: active and passive detection, both of which utilize the spectral absorption characteristics of atmospheric molecules. Passive detection directly analyzes the solar radiation after being absorbed by atmospheric molecules. This method is easily affected by various stray lights and cannot be measured at night. Active detection directly uses lidar to emit lasers and receive scattered light absorbed by atmospheric molecules to detect atmospheric molecules, making up for the defect that passive detection cannot detect at night. However, differential absorption usually has a single wavelength, and the inversion result strongly depends on the weight function determined by the preset atmospheric environment parameters. For multi-wavelength laser differential absorption, the wavelengths are not synchronized in time, which is not suitable for application on high-speed satellite platforms.

[0004] In recent years, an optical frequency comb method has been developed, which combines the advantages of active detection and passive detection. By simultaneously emitting lasers with comb spectra, high-sensitivity and rapid gas absorption line detection can theoretically be achieved. In particular, dual-comb spectroscopy technology can convert the absorption spectrum to be measured from the spectrum to the radio frequency, thereby obtaining absorption spectrum information and realizing high-precision detection of atmospheric components such as greenhouse gases.

[0005] However, current dual-comb spectroscopy technology is limited by extremely low power per comb tooth and complex optical comb generation systems, which results in detection scenarios being confined to laboratories. Detection results are limited to qualitative descriptions of absorption lines, or rely on long-term detection accumulation, and cannot fully realize the technical potential of dual-comb spectroscopy technology in terms of both detection speed and spectral line detection in actual open path detection. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of traditional active and passive spectral detection technologies, and overcome the problem of power dispersion and low signal-to-noise ratio when dual-comb spectroscopy technology is applied to open paths, which leads to a long detection time. An atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual-comb is proposed, which can meet the needs of rapid and accurate measurement of atmospheric greenhouse gases and synchronous acquisition of path atmospheric temperature information.

[0007] The basic principle of the present invention is to obtain two optical frequency combs with intrinsic coherence based on electro-optic modulation and acousto-optic frequency shift, and the two optical combs have different comb tooth frequency intervals and acousto-optic frequency shift amounts. By synchronously transmitting and receiving the two optical combs, the radio frequency signal generated by asynchronous optical sampling of the two optical combs is measured, and by controlling the electro-optic modulation signal and the acousto-optic frequency shift amount, a mapping of the radio frequency signal comb teeth and the optical frequency comb teeth in an orderly corresponding manner is established to invert the greenhouse gas absorption characteristics in the optical frequency domain, and at the same time, the length of the absorption path is obtained according to the flight time of the chopping pulse.

[0008] The technical solution of the present invention is as follows:

[0009] An atmospheric greenhouse gas measurement laser radar system based on electro-optical modulation dual optical comb, characterized in that the device includes a continuous laser, a first coupler, a first electro-optical phase modulator, a first multi-channel optical filter, a first acousto-optic frequency shifter, a second coupler, a second electro-optical phase modulator, a second multi-channel optical filter, a second acousto-optic frequency shifter, a first radio frequency signal generating unit, a second radio frequency signal generating unit, a first optical fiber amplifier, a modulation chopper, a second optical fiber amplifier, a third coupler, a circulator, a telescope, an optical fiber attenuator, a fourth coupler, a photodetector, an electronic amplifier, an electronic filter, a data acquisition card, a data processing unit, and a trigger control unit;

[0010] The output end of the continuous laser is connected to the input end of the first coupler, and the first coupler divides the input light into two continuous lights: one continuous light passes through the first output end of the first coupler, the first electro-optic phase modulator, the first multi-channel optical filter, the first acousto-optic frequency shifter, and the first input end of the second coupler in sequence; the other continuous light passes through the second output end of the first coupler, the second electro-optic phase modulator, the input end of the second multi-channel optical filter, the second multi-channel optical filter, the second acousto-optic frequency shifter, and the second input end of the second coupler in sequence; the first multi-channel optical filter and the second multi-channel optical filter are respectively connected and locked with the continuous laser; the first output end of the first radio frequency signal generating unit is connected to the first The modulation signal input end of the electro-optic phase modulator, the second output end of the first radio frequency signal generating unit is connected to the modulation signal input end of the second electro-optic phase modulator, the first output end of the second radio frequency signal generating unit is connected to the modulation signal input end of the first acousto-optic frequency shifter, and the second output end of the second radio frequency signal generating unit is connected to the modulation signal input end of the second acousto-optic frequency shifter; the above two continuous lights are modulated by the first radio frequency signal generating unit and the second radio frequency signal generating unit, respectively, into two nearly flat-top electro-optic light combs with different repetition frequencies and staggered center frequencies, and are combined through the second coupler to form a combined laser; the two light combs have intrinsic coherence, and the frequency domain shows a few comb teeth feature, and the distribution range of its strong comb teeth is sufficient to cover a certain absorption spectral line window of greenhouse gases; the time domain shows a quasi-continuous feature;

[0011] The output end of the second coupler is connected to the input end of the first optical fiber amplifier, the output end of the first optical fiber amplifier is connected to the input end of the modulation chopper, the output end of the modulation chopper is connected to the input end of the second optical fiber amplifier, the output end of the second optical fiber amplifier is connected to the input end of the third coupler, and the third coupler divides the input light into a large light energy beam and a small light energy beam: the large light energy beam is sequentially emitted to the atmospheric space of an open path through the first output end of the third coupler, the first port and the second port of the circulator, and the telescope, the laser reflected by the diffuse reflection target is received by the telescope, and is transmitted to the photoelectric detector through the second port and the third port of the circulator and the fourth coupler; the small light energy beam is sequentially transmitted to the photoelectric detector through the second output end of the third coupler, the optical fiber attenuator, and the fourth coupler;

[0012] The output end of the photodetector is connected to the input end of the electronic amplifier; the output end of the electronic amplifier is connected to the input end of the electronic filter, the low-pass filter of the electronic filter removes the redundant RF combs that are confused, and retains the only RF comb that corresponds to the teeth of the dual optical comb in sequence; the output end of the electronic filter is connected to the input end of the analog data acquisition card, and the output end of the acquisition card is connected to the data processing unit;

[0013] The output end of the trigger control unit is respectively connected to the control end of the second optical fiber amplifier, the modulation chopper and the acquisition card to achieve synchronous generation, amplification and detection signal acquisition of pulses.

[0014] The combined laser beam of the second coupler is sufficient to cover the 1572nm carbon dioxide absorption line or the 1645nm methane absorption line in the frequency domain, and the point light comb generated by the two-way modulation meets the conditions for frequency conversion of the dual-comb spectrum.

[0015] The beam splitting ratio of the first coupler is 50%:50%, and the beam splitting ratio of the third coupler is 99%:1%.

[0016] The same photoelectric detector is used to successively receive the local monitoring signal and the echo detection signal, thereby avoiding the asymmetric detection effect caused by the detector response.

[0017] The first multi-channel optical filter and the second multi-channel optical filter are used to filter out the power dispersion caused by the clutter introduced by the imperfect electro-optical phase modulation and the phase noise, and concentrate the power in the spectrum.

[0018] The electrical signal collected by each trigger should be two segments in succession, that is, two RF comb signals. After multiple detections, the signal is superimposed to improve the signal-to-noise ratio according to the signal period determined by the inverse of the repetition frequency difference of the dual optical combs. The spectrum characteristics of the local and outgoing dual optical combs are inverted respectively, and the spectrum absorption characteristics of the atmosphere are obtained by comparison. The greenhouse gas concentration information and atmospheric temperature and pressure information are extracted using the optimal estimation algorithm.

[0019] The beneficial effects of the present invention are:

[0020] 1. In the atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual optical combs of the present invention, the local optical comb and the outgoing optical comb are received successively in the same detection channel by controlling the trigger and pulse duration, which naturally corrects the response difference between the outgoing optical comb and the local optical comb detection, and helps to achieve higher detection accuracy.

[0021] 2. The atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual light comb of the present invention is equivalent to emitting multiple wavelength laser signals at the same time, avoiding the time delay problem of frequency scanning in traditional passive methods or the time delay problem of sequentially emitting multiple wavelengths in traditional active methods, and avoiding the interference caused by atmospheric state changes such as atmospheric turbulence and reflective surface state changes during frequency scanning or tuning, causing errors.

[0022] 3. The atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual light comb of the present invention can obtain spectral information by active detection. It makes up for the deficiency that traditional active detection can only emit dual wavelengths on and off on a certain absorption line and can only invert column concentration information; it makes up for the deficiency that traditional passive detection relies on sunlight and can only work during the day. It can achieve the acquisition of atmospheric temperature and pressure information, and at the same time, it can also realize self-calibration of the emission center wavelength with the atmospheric absorption line type as a natural reference.

[0023] 4. The atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual optical comb of the present invention adopts a specific radio frequency signal to modulate a power-concentrated electro-optical optical comb, which solves the problem of power dispersion of traditional optical frequency combs and low signal-to-noise ratio of each comb tooth detection, and realizes fast, high-precision and long-distance atmospheric absorption spectrum line detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the overall structural block diagram of the atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual light comb of the present invention:

[0025] In the figure: 1—continuous laser, 2—first coupler, 3—first electro-optic phase modulator, 4—first multi-channel optical filter, 5—first acousto-optic frequency shifter, 6—second coupler, 7—second electro-optic phase modulator, 8—second multi-channel optical filter, 9—second acousto-optic frequency shifter, 10—first radio frequency signal generating unit, 11—second radio frequency signal generating unit, 12—first optical fiber amplifier, 13—modulation chopper, 14—second optical fiber amplifier, 15—third coupler, 16—circulator, 17—telescope, 18—optical fiber attenuator, 19—fourth coupler, 20—photodetector, 21—electronic amplifier, 22—electronic filter, 23—analog data acquisition card, 24—data processing unit, 25—trigger control unit. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with examples and drawings, but the protection scope of the present invention should not be limited thereto.

[0027] Please refer to Figure 1 , Figure 1The figure is a block diagram of the overall structure of the atmospheric greenhouse gas measurement laser radar system based on electro-optical modulation dual optical comb of the present invention. As can be seen from the figure, the atmospheric greenhouse gas measurement laser radar system based on electro-optical modulation dual optical comb of the present invention includes a continuous laser 1, a first coupler 2, a first electro-optical phase modulator 3, a first multi-channel optical filter 4, a first acousto-optic frequency shifter 5, a second coupler 6, a second electro-optical phase modulator 7, a second multi-channel optical filter 8, a second acousto-optic frequency shifter 9, a first radio frequency signal generating unit 10, a second radio frequency signal generating unit 11, a first optical fiber amplifier 12, a modulation chopper 13, a second optical fiber amplifier 14, a third coupler 15, a circulator 16, a telescope 17, an optical fiber attenuator 18, a fourth coupler 19, a photodetector 20, an electronic amplifier 21, an electronic filter 22, a data acquisition card 23, a data processing unit 24, and a trigger control unit 25.

[0028] The output end of the continuous laser 1 is connected to the input end of the first coupler 2, and the first coupler 2 divides the input light into two continuous lights: one continuous light passes through the first output end of the first coupler 2, the first electro-optic phase modulator 3, the first multi-channel optical filter 4, the first acousto-optic frequency shifter 5, and the first input end of the second coupler 6 in sequence; the other continuous light passes through the second output end of the first coupler 2, the second electro-optic phase modulator 7, the second multi-channel optical filter 8, the second acousto-optic frequency shifter 9, and the second input end of the second coupler 6 in sequence; the first multi-channel optical filter 4 and the second multi-channel optical filter 8 are respectively connected and locked with the continuous laser 1; the first output end of the first radio frequency signal generating unit 10 is connected to the first electro-optic phase modulator 3, the second output end of the first RF signal generating unit 10 is connected to the modulation signal input end of the second electro-optic phase modulator 7, the first output end of the second RF signal generating unit 11 is connected to the modulation signal input end of the first acousto-optic frequency shifter 5, and the second output end of the second RF signal generating unit 11 is connected to the modulation signal input end of the second acousto-optic frequency shifter 9; the above two continuous lights are modulated by the first RF signal generating unit 10 and the second RF signal generating unit 11, respectively, into two nearly flat-topped electro-optic light combs with different repetition frequencies and staggered center frequencies, and are combined through the second coupler 6 to form a combined laser; the two light combs have intrinsic coherence, and the frequency domain shows a few comb teeth feature, and the distribution range of its strong comb teeth is sufficient to cover a certain absorption spectral line window of greenhouse gases; the time domain shows a quasi-continuous feature;

[0029] The output end of the second coupler 6 is connected to the input end of the first fiber amplifier 12, the output end of the first fiber amplifier 12 is connected to the input end of the modulation chopper 13, the output end of the modulation chopper 13 is connected to the input end of the second fiber amplifier 14, the output end of the second fiber amplifier 14 is connected to the input end of the third coupler 15, and the third coupler 15 divides the input light into a large light energy beam and a small light energy beam: the large light energy beam is sequentially emitted to the open path atmosphere through the first output end of the third coupler 15, the first port and the second port of the circulator 16, and the telescope 17, the laser reflected by the diffuse reflection target is received by the telescope 17, and is transmitted to the photoelectric detector 20 through the second port and the third port of the circulator 16 and the fourth coupler 19; the small light energy beam is sequentially transmitted to the photoelectric detector 20 through the second output end of the third coupler 15, the fiber attenuator 18, and the fourth coupler 19;

[0030] The output end of the photodetector 20 is connected to the input end of the electronic amplifier 21; the output end of the electronic amplifier 21 is connected to the input end of the electronic filter 22, and the low-pass filter of the electronic filter 22 removes the redundant RF combs that are confused, and retains the only RF comb that corresponds to the teeth of the dual optical comb in sequence; the output end of the electronic filter 22 is connected to the input end of the analog data acquisition card 23, and the output end of the acquisition card 23 is connected to the data processing unit 24;

[0031] The output end of the trigger control unit 25 is respectively connected to the control end of the second optical fiber amplifier 14, the modulation chopper 13 and the acquisition card 23 to achieve synchronous generation, amplification and detection signal acquisition of pulses.

[0032] The combined laser beam of the second coupler 6 is sufficient to cover the 1572nm carbon dioxide absorption line or the 1645nm methane absorption line in the frequency domain, and the point light comb generated by the two-way modulation meets the conditions for frequency conversion of the dual-comb spectrum.

[0033] The same photoelectric detector 20 is used to successively receive the local monitoring signal and the echo detection signal, thereby avoiding the asymmetric detection effect caused by the detector response.

[0034] The first multi-channel optical filter 4 and the second multi-channel optical filter 8 are used to filter out the power dispersion caused by the clutter introduced by the imperfect electro-optical phase modulation and the phase noise, and concentrate the power in the spectrum.

[0035] The basic principle of the present invention is to split the continuous laser into two equal parts through the first coupler 2, and the two parts are modulated by the first electro-optic phase modulator 3 and the second electro-optic phase modulator 7 to generate an electro-optic light comb, and the phase noise and redundant comb teeth generated by the undesirable modulation are suppressed by the first multi-channel optical filter 4 and the second multi-channel optical filter 8, and the frequency spectrum position of the light comb is changed by the first acousto-optic frequency shifter 5 and the second acousto-optic frequency shifter 9. In the above modulation process, the repetition frequencies of the two electro-optic light combs are different by controlling the two output signals of the first radio frequency signal generator 10 as the modulation signals of the two electro-optic modulators respectively; the center frequency offsets of the two electro-optic light combs are different by controlling the two output signals of the second radio frequency signal generator 11 as the modulation signals of the two acousto-optic frequency shifters. Thus, the two light combs meet the conditions for using the dual-comb spectrum detection technology. After the dual optical comb optical signal is combined, it is amplified by the first optical fiber amplifier 12, chopped by the modulation chopper 13, and amplified by the second optical fiber amplifier 14, and then split by the third coupler 15. Most of the light is transmitted to the telescope 17 through the circulator 16, and then emitted to the diffuse reflector and reflected again, received by the telescope 17, and then transmitted to the fourth coupler 19 through the circulator 16; a small part of the light is also transmitted to the fourth coupler 19 after attenuation by the optical fiber attenuator 18. The above two parts of light are received by the photodetector 20 successively because the flight time of the former in free space introduces delay. The detection results of the two parts of the dual optical comb signal are Fourier transformed to obtain two groups of radio frequency combs respectively. For the detected radio frequency signal, it is amplified by the electronic amplifier 21 and filtered by the electronic filter 22 to remove the redundant confusing radio frequency comb groups, and retain a single group of radio frequency combs that are mapped one by one with the comb teeth of the dual optical comb in sequence in the frequency domain. By comparing the detection signals of the local dual-comb and the dual-comb through the open path of the atmosphere, the atmospheric absorption spectrum information is inverted, thereby obtaining the concentration information of greenhouse gases in the atmosphere and the atmospheric temperature and pressure information.

[0036] Example

[0037] The beam splitting ratio of the first coupler 2 is 50%:50%, and the beam splitting ratio of the third coupler 15 is 99%:1%.

[0038] The specific devices used in this embodiment are: the wavelength of the continuous laser 1 is at 1572nm, corresponding to carbon dioxide, or 1645nm, corresponding to methane, which is different for the types of greenhouse gases detected but does not affect the principle of this embodiment; the first electro-optical phase modulator 3 and the second electro-optical phase modulator 7 are lithium niobate high-speed electro-optical phase modulators; the first multi-channel optical filter 4 and the second multi-channel optical filter 8 are FP cavities; the first coupler 2 and the second coupler 6 are 50%:50% optical couplers; the third coupler 15 is a 99%:1% optical coupler, in which 99% of the light is emitted through the circulator 16 and the telescope 17, and 1% of the light is transmitted to the optical fiber attenuator 18; the telescope 17 is a telescope system with a common optical axis for transmission and reception.

[0039] The specific process of implementing the atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual light comb in the present invention is:

[0040] ① The output laser of the continuous laser 1 is divided into two through the first coupler 2: 50% of the laser is transmitted to the second coupler 6 through the first electro-optic phase modulator 2, the first multi-channel filter 4, and the first acousto-optic frequency shifter 5; 50% of the laser is transmitted to the second coupler 6 through the second electro-optic phase modulator 7, the second multi-channel filter 8, and the second acousto-optic frequency shifter 9. The beams are combined in the second coupler 6 to form a dual-comb optical signal. Taking the third harmonic as an example, the modulated optical signal of any one path can be expressed as:

[0041]

[0042] ② The first fiber amplifier 12, the modulation chopper 13, and the second fiber amplifier 14 amplify, chop, and re-amplify the dual optical comb signal, and couple it into the third coupler 15. 99% of the laser light is transmitted from the first port to the second port through the circulator 16 and emitted through the telescope 17; 1% of the laser light is used as the local detection light of the dual optical comb through the fiber attenuator 18.

[0043] ③ The telescope 17 receives the echo signal light of the diffuse reflection target, which enters the circulator 16 through the second input port of the circulator 16 and enters the fourth coupler 19 through the output of the third port. The second input port of the fourth coupler 19 is connected to the optical fiber attenuator 18 to receive the monitoring signal light of the dual optical comb. The monitoring signal light and the echo signal light of each pulse are successively emitted to the photoelectric detector 20, and the electrical signal is amplified by the electronic amplifier 21. The electronic filter 22 performs low-pass filtering. The analog data acquisition card 23 collects the signal as a digital signal and sends it to the data processing unit 24 for superposition to improve the signal-to-noise ratio. In the data processing unit 24, the signal is Fourier transformed to obtain a radio frequency comb, and the absorption of the optical frequency comb is deduced. The concentration of greenhouse gases in the atmosphere and the temperature and pressure information of the atmosphere are inverted.

[0044] It should be understood that although the terms "first", "second", etc. may be used herein to describe various units, these units should not be limited by these terms. These terms are used only to distinguish one unit from another. For example, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit without departing from the scope of the exemplary embodiments.

[0045] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual light comb, characterized in that: The invention comprises a continuous laser (1), a first coupler (2), a first electro-optic phase modulator (3), a first multi-channel optical filter (4), a first acousto-optic frequency shifter (5), a second coupler (6), a second electro-optic phase modulator (7), a second multi-channel optical filter (8), a second acousto-optic frequency shifter (9), a first radio frequency signal generating unit (10), a second radio frequency signal generating unit (11), a first optical fiber amplifier (12), a modulation chopper (13), a second optical fiber amplifier (14), a third coupler (15), a circulator (16), a telescope (17), an optical fiber attenuator (18), a fourth coupler (19), a photodetector (20), an electronic amplifier (21), an electronic filter (22), a data acquisition card (23), a data processing unit (24), and a trigger control unit (25); The output end of the continuous laser (1) is connected to the input end of the first coupler (2), and the first coupler (2) divides the input light into two paths of continuous light: one path of continuous light passes through the first output end of the first coupler (2), the first electro-optic phase modulator (3), the first multi-channel optical filter (4), the first acousto-optic frequency shifter (5), and the first input end of the second coupler (6) in sequence; the other path of continuous light passes through the second output end of the first coupler (2), the second electro-optic phase modulator (7), the input end of the second multi-channel optical filter (8), the second multi-channel optical filter (8), the second acousto-optic frequency shifter (9), and the second input end of the second coupler (6) in sequence; the first multi-channel optical filter (4) and the second multi-channel optical filter (8) are respectively connected and locked to the continuous laser (1); the first output end of the first radio frequency signal generating unit (10) is connected to the first The modulation signal input end of the electro-optic phase modulator (3), the second output end of the first radio frequency signal generating unit (10) is connected to the modulation signal input end of the second electro-optic phase modulator (7), the first output end of the second radio frequency signal generating unit (11) is connected to the modulation signal input end of the first acousto-optic frequency shifter (5), and the second output end of the second radio frequency signal generating unit (11) is connected to the modulation signal input end of the second acousto-optic frequency shifter (9); the two continuous lights are modulated by the first radio frequency signal generating unit (10) and the second radio frequency signal generating unit (11) respectively into two nearly flat-top electro-optic light combs with different repetition frequencies and staggered center frequencies, and are combined by the second coupler (6) to form a combined laser beam; the electro-optic light comb has intrinsic coherence, and the frequency domain shows a few comb teeth feature, and the distribution range of its strong comb teeth is sufficient to cover a certain absorption spectral line window of greenhouse gases; the time domain shows a quasi-continuous feature; The output end of the second coupler (6) is connected to the input end of the first optical fiber amplifier (12), the output end of the first optical fiber amplifier (12) is connected to the input end of the modulation chopper (13), the output end of the modulation chopper (13) is connected to the input end of the second optical fiber amplifier (14), the output end of the second optical fiber amplifier (14) is connected to the input end of the third coupler (15), and the third coupler (15) divides the input light into a large optical energy beam and a small optical energy beam: the large optical energy beam is sequentially connected to the input end of the third coupler (15) and the output end of the second optical fiber amplifier (14) is connected to the input end of the third coupler (15). The first output end of the optical fiber circulator (15), the first port and the second port of the circulator (16), and the telescope (17) are emitted into the open path of the atmospheric space. The laser light reflected by the diffuse reflection target is received by the telescope (17) and transmitted to the photoelectric detector (20) via the second port and the third port of the circulator (16) and the fourth coupler (19); the small light energy beam is sequentially transmitted to the photoelectric detector (20) via the second output end of the third coupler (15), the optical fiber attenuator (18), and the fourth coupler (19); The output end of the photodetector (20) is connected to the input end of the electronic amplifier (21); the output end of the electronic amplifier (21) is connected to the input end of the electronic filter (22); the low-pass filter of the electronic filter (22) removes the redundant radio frequency combs that are confused, and retains the only radio frequency comb that corresponds to the teeth of the dual optical comb in sequence; the output end of the electronic filter (22) is connected to the input end of the data acquisition card (23); the output end of the acquisition card (23) is connected to the data processing unit (24); The output end of the trigger control unit (25) is respectively connected to the control ends of the second optical fiber amplifier (14), the modulation chopper (13) and the acquisition card (23), so as to realize synchronous generation, amplification and detection signal acquisition of pulses.

2. The atmospheric greenhouse gas measurement laser radar system based on electro-optical modulation dual light comb according to claim 1 is characterized in that: The combined laser beam of the second coupler (6) is sufficient to cover the 1572nm carbon dioxide absorption line or the 1645nm methane absorption line in the frequency domain, and the point light comb generated by the two-way modulation meets the conditions for frequency conversion of the dual-comb spectrum.

3. The atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual light comb according to claim 1 is characterized in that: The splitting ratio of the first coupler (2) is 50%:50%, and the splitting ratio of the third coupler (15) is 99%:1%.

4. The atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual light comb according to claim 1 is characterized in that The same photoelectric detector (20) is used to successively receive the local monitoring signal and the echo detection signal, thereby avoiding the asymmetric detection influence caused by the detector response.

5. The atmospheric greenhouse gas measurement lidar system based on electro-optical modulation dual light comb according to claim 1 is characterized in that The first multi-channel optical filter (4) and the second multi-channel optical filter (8) are used to filter out power dispersion caused by clutter and phase noise introduced by imperfect electro-optical phase modulation, thereby concentrating power on the spectrum.

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