阅读说明：本技术 基于电光调制单种子注入差分吸收激光雷达 (Single seed injection differential absorption laser radar based on electro-optical modulation ) 是由 刘林美 杨勇 林鑫 程学武 李发泉 季凯俊 马昕 龚威 于 2020-07-13 设计创作，主要内容包括：本发明公开了基于电光调制单种子注入差分吸收激光雷达,包括种子激光器、吸收光谱稳频系统、第一分光光纤、电光调制器、光纤放大器、脉冲激光器、激光发射系统、接收望远镜、信号检测系统、数据采集系统和时序同步系统,本发明通过电光调制实现了单一种子激光器产生第一波长和第二波长的交替激光,降低成本,对第一波长和第二波长均具有稳频的效果,提高了系统的精度。(The invention discloses a single seed injection differential absorption laser radar based on electro-optical modulation, which comprises a seed laser, an absorption spectrum frequency stabilization system, a first light splitting optical fiber, an electro-optical modulator, an optical fiber amplifier, a pulse laser, a laser transmitting system, a receiving telescope, a signal detection system, a data acquisition system and a time sequence synchronization system.)

1. The single seed injection differential absorption laser radar based on electro-optical modulation comprises a seed laser (1) and is characterized in that laser output by the seed laser (1) enters an input end of a first light splitting optical fiber (3), laser output by a first output end of the first light splitting optical fiber (3) enters an input end of an absorption spectrum frequency stabilization system (2), an output end of the absorption spectrum frequency stabilization system (2) is connected with a frequency control end of the seed laser (1), laser output by a second output end of the first light splitting optical fiber (3) enters an input end of an electro-optical modulator (4), an output end of the electro-optical modulator (4) is connected with a seed laser input end of a pulse laser (6) through an optical fiber amplifier (5), pulse laser output by the pulse laser (6) is emitted into the atmosphere through a laser emission system (7), and echo scattered light of the pulse laser in the atmosphere is received through a receiving telescope (8) and is received by a signal detection system (9) ) Photoelectric detection is carried out to obtain scattered echo electric signals, the scattered echo electric signals are collected by a data collecting system (10), and a time sequence synchronization system (11) outputs two paths of same square waves to a time sequence control end of an electro-optical modulator (4) and a synchronization triggering end of the data collecting system (10) respectively.

2. The uni-species injection differential absorption lidar based on electro-optic modulation according to claim 1, characterized in that the absorption spectrum frequency stabilization system (2) comprises a second splitting optical fiber (21), a first focusing lens (22), a first photodetector (23), a collimating mirror (24), a long-range gas absorption cell (25), a second focusing lens (26), a second photodetector (27) and a frequency stabilization controller (28),

laser emitted from a first output end of the first light splitting optical fiber (3) enters an input end of a second light splitting optical fiber (21), the laser emitted from a first output end of the second light splitting optical fiber (21) is focused to a first photoelectric detector (23) through a first focusing lens (22) to perform photoelectric detection to obtain a reference signal, the laser emitted from a second output end of the second light splitting optical fiber (21) is collimated through a collimating lens (24) and then passes through a long-optical-range gas absorption cell (25), and then is focused on a second photoelectric detector (27) through a second focusing lens (26) to perform photoelectric detection to obtain an absorption spectrum signal of detection gas, the long-optical-range gas absorption cell (25) is filled with the detection gas, the reference signal detected by the first photoelectric detector (23) and the absorption spectrum signal detected by the second photoelectric detector (27) are input into an input end of a frequency stabilizing controller (28), and an output end of the frequency stabilizing controller (28) is connected with a frequency control end of the seed laser (1).

3. The single seed injection differential absorption lidar based on electro-optical modulation as claimed in claim 2, characterized in that the electro-optical modulator (4) comprises an electro-optical crystal (41), a bias controller (42), a first radio frequency amplifier (43), a second radio frequency amplifier (44) and a radio frequency signal source (45),

laser output by a second output end of the first light splitting optical fiber (3) is incident to an input end of the electro-optical crystal (41), an output end of the bias voltage controller (42) is connected with a bias voltage input end of the electro-optical crystal (41), two output ends of the radio frequency signal source (45) are respectively connected with two radio frequency signal input ends of the electro-optical crystal (41) after being amplified by the first radio frequency amplifier (43) and the second radio frequency amplifier (44), and an output end of the electro-optical crystal (41) serves as an output end of the electro-optical modulator (4).

4. The singlet injection differential absorption lidar based on electro-optic modulation according to claim 3, wherein when the square wave is at a high level, the wavelength of the laser output by the electro-optic modulator (4) is a first wavelength, and the data acquisition system (10) is triggered to acquire the scattered echo electrical signal and mark the acquired scattered echo electrical signal as scattered echo electrical signal data corresponding to the first wavelength;

when the square wave is at a low level, the wavelength of the laser output by the electro-optical modulator (4) is a second wavelength, and meanwhile, the data acquisition system (10) is triggered to acquire the scattering echo electric signal and mark the scattering echo electric signal as scattering echo electric signal data corresponding to the second wavelength.

Technical Field

The invention relates to the field of atmospheric and photoelectric detection, in particular to a single seed injection differential absorption laser radar based on electro-optical modulation.

Background

Global changes cause huge economic losses to human society every year, and all aspects of influence on the environment directly endanger human survival. It is now well recognized that changes in fossil fuel use and land utilization caused by human activities change the original carbon cycle process of the earth, so that carbon-containing greenhouse gases in the atmosphere are continuously and rapidly accumulated, a stronger greenhouse effect is caused, and unbalance of energy balance of the earth is caused, thereby causing the most important climate change in global change.

The laser radar is an effective means for detecting the profile of greenhouse gases at present, wherein the differential absorption laser radar is mainly used for emitting pulse lasers with two wavelengths, one wavelength is called on wavelength on the absorption peak of the greenhouse gases, and the other wavelength is called off wavelength on the absorption valley of the greenhouse gases, so that the detection inversion is carried out. The positions of the two wavelengths directly affect the accuracy of the inversion, and the two wavelengths need to be frequency-locked to obtain the inversion result with high accuracy.

There are currently two main ways to obtain laser light at on and off wavelengths: one is through a frequency difference mode, such as described in literature 1 (ma xin, goffer, margar, etc., "frequency stabilization research of pulse differential absorption CO2 lidar based on matching algorithm", physical science report, 64(15),154215-1-154215-11,2015), where the laser obtained in this way can only lock the frequency of the output pulse on wavelength, but not the off wavelength, and this pulse frequency locking mode has great technical difficulty and low precision. Another method is to use two continuous wave lasers to output seed lasers with on wavelength and off wavelength respectively, and then inject the seed lasers into two pulse lasers respectively to generate the required pulse on wavelength laser and pulse off wavelength laser, as described in document 2 (Honghuang, Wangchun, Shouchun, etc. "an optical transmitter for differential absorption lidar detecting atmospheric pressure", infrared and millimeter wave academy 38(4),451-458,2019), which not only needs two seed lasers to inject, but also can only lock the frequency of the on wavelength laser and cannot lock the frequency of the off wavelength laser when a standard light source is used to stabilize the frequency of the laser.

Disclosure of Invention

The technical problem to be solved by the present invention is to overcome the defects of the prior art, and to provide a singlet injection differential absorption laser radar based on electro-optical modulation, which utilizes a seed laser and an electro-optical modulator to generate alternating laser light of a first wavelength and a second wavelength, wherein the first wavelength and the second wavelength can be rapidly switched, and both can utilize atomic-molecular spectroscopy to realize absolute locking. The method only needs one seed laser, so that the cost is reduced, and the laser frequency is stabilized by stabilizing the frequency of the continuous light. The continuous light can be continuously sampled, so that the laser frequency stabilization technology of the invention is stable and reliable, and the frequency of each emitted light pulse can be ensured to be locked on the designated frequency. The long-term stability of the frequency of the seed laser is better than 2 MHz. And then, injecting continuous seed laser into the pulse laser by adopting a continuous seed injection technology to realize high-precision stability of the frequency of the pulse laser.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

the single-seed injection differential absorption laser radar based on electro-optical modulation comprises a seed laser, wherein laser output by the seed laser enters an input end of a first light splitting optical fiber, laser emitted by a first output end of the first light splitting optical fiber enters an input end of an absorption spectrum frequency stabilization system, an output end of the absorption spectrum frequency stabilization system is connected with a frequency control end of the seed laser, laser emitted by a second output end of the first light splitting optical fiber enters an input end of the electro-optical modulator, an output end of the electro-optical modulator is connected with a seed laser input end of a pulse laser through an optical fiber amplifier, pulse laser output by the pulse laser is emitted into the atmosphere through a laser emission system, scattered echo light of the pulse laser in the atmosphere is received through a receiving telescope and is subjected to electro-optical detection through a signal detection system to obtain scattered echo electric signals, and the scattered echo electric signals are collected through a data collection system, the time sequence synchronization system respectively outputs two paths of same square waves to a time sequence control end of the electro-optical modulator and a synchronization triggering end of the data acquisition system.

The absorption spectrum frequency stabilization system comprises a second light splitting optical fiber, a first focusing lens, a first photoelectric detector, a collimating mirror, a long-optical-path gas absorption cell, a second focusing lens, a second photoelectric detector and a frequency stabilization controller,

laser emitted from a first output end of the first optical fiber enters an input end of a second optical fiber, the laser emitted from a first output end of the second optical fiber is focused to a first photoelectric detector through a first focusing lens to perform photoelectric detection to obtain a reference signal, the laser emitted from a second output end of the second optical fiber passes through a long-optical-range gas absorption cell after being collimated through a collimating mirror, and then is focused to a second photoelectric detector through a second focusing lens to perform photoelectric detection to obtain an absorption spectrum signal of detection gas, the long-optical-range gas absorption cell is filled with the detection gas, the reference signal detected by the first photoelectric detector and the absorption spectrum signal detected by the second photoelectric detector are input to an input end of a frequency stabilizing controller, and an output end of the frequency stabilizing controller is connected with a frequency control end of a seed laser.

The electro-optic modulator as described above includes an electro-optic crystal, a bias controller, a first radio frequency amplifier, a second radio frequency amplifier, and a radio frequency signal source,

the laser output by the second output end of the first light splitting optical fiber is incident to the input end of the electro-optical crystal, the output end of the bias voltage controller is connected with the bias voltage input end of the electro-optical crystal, the two output ends of the radio frequency signal source are respectively connected with the two radio frequency signal input ends of the electro-optical crystal after being amplified by the first radio frequency amplifier and the second radio frequency amplifier, and the output end of the electro-optical crystal is used as the output end of the electro-optical modulator.

When the square wave is at a high level, the wavelength of the laser output by the electro-optical modulator is a first wavelength, and meanwhile, the data acquisition system is triggered to acquire the scattered echo electric signal and mark the scattered echo electric signal as scattered echo electric signal data corresponding to the first wavelength;

when the square wave is at a low level, the wavelength of the laser output by the electro-optical modulator is a second wavelength, and meanwhile, the data acquisition system is triggered to acquire the scattered echo electric signal and mark the scattered echo electric signal as scattered echo electric signal data corresponding to the second wavelength.

Compared with the prior art, the invention has the following beneficial effects:

compared with the traditional method that two seed lasers are used for generating laser with the first wavelength (on wavelength) and the second wavelength (off wavelength), the method has the advantages that one seed laser is saved, the cost is reduced, more importantly, the frequency of the first wavelength (on wavelength) is stabilized, the electro-optically modulated second wavelength (off wavelength) also has the frequency stabilizing effect, and the frequency of the second wavelength (off wavelength) cannot be stabilized in the traditional mode, so that the cost is reduced, and the precision of the system is improved.

Drawings

Fig. 1 is a schematic structural diagram of a single seed injection differential absorption laser radar based on electro-optical modulation.

Fig. 2 is a schematic structural diagram of an absorption spectrum frequency stabilization system.

Fig. 3 is a schematic diagram of the structure of an electro-optic modulator.

In the figure: 1-seed laser; 2-an absorption spectrum frequency stabilization system; 3-a first light splitting fiber; 4-an electro-optic modulator; 5-an optical fiber amplifier; 6-a pulsed laser; 7-a laser emission system; 8-a receiving telescope; 9-a signal detection system; 10-a data acquisition system; 11-a timing synchronization system;

21-a second beam splitting optical fiber; 22-a first focusing lens; 23-a first photodetector; 24-a collimating mirror; 25-a long optical path gas absorption cell; 26-a second focusing lens; 27-a second photodetector; 28-a frequency stabilization controller;

41-an electro-optic crystal; 42-a bias controller; 43-a first radio frequency amplifier; 44-a second radio frequency amplifier; 45-radio frequency signal source.

Detailed Description

The present invention will be described in further detail with reference to examples for the purpose of facilitating understanding and practice of the invention by those of ordinary skill in the art, and it is to be understood that the present invention has been described in the illustrative embodiments and is not to be construed as limited thereto.

Fig. 1 is a schematic structural diagram of the present invention, and the single-seed injection differential absorption lidar device based on electro-optical modulation includes a seed laser 1, an absorption spectrum frequency stabilization system 2, a first light splitting optical fiber 3, an electro-optical modulator 4, an optical fiber amplifier 5, a pulse laser 6, a laser emission system 7, a receiving telescope 8, a signal detection system 9, a data acquisition system 10, and a timing synchronization system 11, and implements high-precision detection of greenhouse gas differential lidar in the atmosphere.

The seed laser 1 is output by adopting a semiconductor continuous laser optical fiber, laser output by the seed laser 1 enters an input end of a first light splitting optical fiber 3, is split by the first light splitting optical fiber 3 and then is emitted through a first output end and a second output end respectively, wherein the laser emitted from the first output end of the first light splitting optical fiber 3 enters an absorption spectrum frequency stabilizing system 2, and the laser emitted from the second output end of the first light splitting optical fiber 3 enters an input end of an electro-optical modulator 4.

The structure of the absorption spectrum frequency stabilization system 2 is shown in fig. 2, and includes a second optical splitting fiber 21, a first focusing lens 22, a first photodetector 23, a collimating mirror 24, a long-optical-path gas absorption cell 25, a second focusing lens 26, a second photodetector 27, and a frequency stabilization controller 28.

The laser emitted from the first output end of the first optical splitter fiber 3 enters the input end of the second optical splitter fiber 21, is split by the second optical splitter fiber 21 and then is emitted through the first output end and the second output end, and the laser emitted from the first output end of the second optical splitter fiber 21 is focused by the first focusing lens 22 to the first photoelectric detector 23 for photoelectric detection to obtain a reference signal. The laser emitted from the second output end of the second light splitting fiber 21 is collimated by the collimator lens 24 and then enters the incident end of the long-optical-path gas absorption cell 25, the long-optical-path gas absorption cell 25 is filled with the detection gas, the laser is reflected for multiple times in the long-optical-path gas absorption cell 25 and then is output from the exit end of the long-optical-path gas absorption cell 25, and then is focused on the second photoelectric detector 27 through the second focusing lens 26 to perform photoelectric detection, so that the absorption spectrum of the detection gas is obtained. The reference signal detected by the first photodetector 23 and the absorption spectrum signal detected by the second photodetector 27 are input to the input end of the frequency stabilization controller 28 for processing, and the output end of the frequency stabilization controller 28 is connected to the frequency control end of the seed laser 1, so as to lock the wavelength of the seed laser 1 on the peak value of the absorption spectrum of the detection gas (as long as the gas detected by differential absorption can be realized by using the method, for example, the detection gas may be carbon dioxide, carbon monoxide, sulfur dioxide, nitrogen dioxide, methane, etc.).

The electro-optical modulator 4 is constructed as shown in fig. 3, and the electro-optical modulator 4 includes an electro-optical crystal 41, a bias controller 42, a first radio frequency amplifier 43, a second radio frequency amplifier 44, and a radio frequency signal source 45. The laser output from the second output end of the first light splitting fiber 3 is incident to the input end of the electro-optical crystal 41, and the electro-optical crystal 41 needs to be controlled by a bias voltage and a radio frequency signal, so the output end of the bias controller 42 is connected to the bias input end of the electro-optical crystal 41, two output ends of the radio frequency signal source 45 are respectively connected to two radio frequency signal input ends of the electro-optical crystal 41 after being amplified by the first radio frequency amplifier 43 and the second radio frequency amplifier 44, and the output end of the electro-optical crystal 41 serves as the output end of the electro-optical modulator 4.

The output end of the electro-optical modulator 4 is connected with the input end of the optical fiber amplifier 5, the output end of the optical fiber amplifier 5 is connected with the seed laser input end of the pulse laser 6, and the continuous seed laser output by the optical fiber amplifier 5 is subjected to pulse amplification by the pulse laser 6 to obtain high-power narrow pulse laser. The pulse laser is transmitted to the atmosphere through the laser transmitting system 7, the scattered echo light of the pulse laser in the atmosphere is received through the receiving telescope 8, the echo signal received by the receiving telescope 8 is subjected to photoelectric detection through the signal detecting system 9 to obtain a scattered echo electric signal, and the obtained scattered echo electric signal is connected to the input end of the data collecting system 10 through the output end of the signal detecting system 9 through a cable to be subjected to data acquisition and processing. In the present invention, the laser beams of the first wavelength (on wavelength) and the second wavelength (off wavelength) are alternately detected in time division, and therefore, it is necessary to synchronize the timing. The time sequence synchronization system 11 generates two paths of identical square waves, one path of output end is connected to the time sequence control end of the electro-optical modulator 4, the other path of output end is connected to the synchronization trigger end of the data acquisition system 10, when the square waves are at a high level, the wavelength of laser output by the electro-optical modulator 4 is controlled to be a first wavelength (on wavelength), and meanwhile, the data acquisition system 10 is triggered to acquire scattered echo electric signals and mark the acquired data as scattered echo electric signal data corresponding to the first wavelength (on wavelength). When the square wave is at a low level, the wavelength of the laser output by the electro-optical modulator 4 is controlled to be a second wavelength (off wavelength), and meanwhile, the data acquisition system 10 is triggered to acquire the scattered echo electric signal and mark the acquired data as scattered echo electric signal data corresponding to the second wavelength (off wavelength).

In the absorption spectrum frequency stabilization system 2, the absorption peak of the continuous seed laser is obtained by adopting a mode of increasing the optical path because the absorption of the greenhouse gas in the near infrared is very weak. The wavelength of the seed laser is accurately stabilized on the absorption peak of the greenhouse gas by the absorption spectrum frequency stabilizing system 2.

The electro-optical modulator 4 couples the frequency-stabilized seed laser into the electro-optical modulator 4. The electro-optical modulator 4 controls the modulation voltage according to the square wave input from the time sequence control end, thereby realizing the frequency conversion of the seed laser. The electro-optical modulator 4 may shift the frequency of the laser light of the first wavelength (on wavelength) to a second wavelength (off wavelength). Since the first wavelength (on wavelength) passes through the stabilized laser wavelength, the second wavelength (off wavelength) shifted by the electro-optical modulator 4 also has the characteristic of frequency stabilization.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.