阅读说明：本技术 用于水汽差分吸收激光雷达的光纤激光装置及使用方法 (Optical fiber laser device for water vapor differential absorption laser radar and use method ) 是由 吴德成 刘�东 钟志庆 邓迁 王英俭 于 2020-11-26 设计创作，主要内容包括：本发明公开了一种用于水汽差分吸收激光雷达的光纤激光装置及使用方法,装置包括依次设置的第一DFB光纤激光器和第二DFB光纤激光器,作为种子激光光源；脉冲调制模块,将种子激光光源输出的连续光调制成设定重复频率的脉冲激光；掺杂光纤放大器,用于将脉冲调制模块输出的脉冲激光进行放大；倍频模块,将放大后的脉冲激光进行倍频。本发明利用两个DFB光纤激光器作为种子激光并分时输出,然后用脉冲调制模块将DFB光纤激光器输出的连续种子光调制成脉冲光,脉冲光经过掺杂光纤放大后倍频,获得脉冲能量几十uJ的双波长单纵模激光输出,满足水汽差分吸收激光雷达的应用需求。(The invention discloses a fiber laser device for a water vapor differential absorption laser radar and a use method thereof, wherein the device comprises a first DFB fiber laser and a second DFB fiber laser which are sequentially arranged and used as seed laser light sources; the pulse modulation module is used for modulating the continuous light output by the seed laser light source into pulse laser with a set repetition frequency; the doped fiber amplifier is used for amplifying the pulse laser output by the pulse modulation module; and the frequency doubling module is used for doubling the frequency of the amplified pulse laser. The invention utilizes two DFB fiber lasers as seed lasers to output in a time-sharing manner, then uses the pulse modulation module to modulate the continuous seed light output by the DFB fiber lasers into pulse light, and the pulse light is amplified by the doped fiber and then frequency-doubled to obtain dual-wavelength single longitudinal mode laser output with pulse energy of dozens of uJ, thereby meeting the application requirement of the water vapor differential absorption laser radar.)

1. A fiber laser device for water vapor differential absorption laser radar, characterized in that, including what set gradually

A first DFB fiber laser (1) and a second DFB fiber laser (2) as seed laser light sources;

the pulse modulation module (4) is used for modulating the continuous light output by the seed laser light source into pulse laser with a set repetition frequency;

the doped fiber amplifier (5) is used for amplifying the pulse laser output by the pulse modulation module (4);

the frequency doubling module (6) is used for frequency doubling the laser output and amplified by the first DFB optical fiber laser (1) to obtain the laser output with the wavelength positioned on the water vapor absorption line wing lambda off; and frequency doubling the laser output and amplified by the second DFB fiber laser (2) to obtain the laser output with the wavelength positioned on the water vapor absorption line lambda on.

2. The fiber laser device for the water vapor differential absorption lidar according to claim 1, wherein the device comprises two sets of laser processing units consisting of a pulse modulation module (4), a doped fiber amplifier (5) and a frequency doubling module (6), which are respectively used for processing the laser output by the first DFB fiber laser (1) and the laser output by the second DFB fiber laser (2).

3. The fiber laser device for the water vapor differential absorption laser radar according to claim 1, wherein the device further comprises a light switching module (3) for time-sharing gating the seed lasers output by the first DFB fiber laser (1) and the second DFB fiber laser (2) to realize the alternate output of the seed lasers with two wavelengths.

4. The fiber laser device for moisture differential absorption lidar according to claim 1, further comprising a frequency locking module (7) for locking the output frequency of the second DFB fiber laser (2).

5. The fiber laser device for moisture differential absorption lidar according to claim 1, wherein the pulse modulation module (4) is an acousto-optic modulator AOM or a chopper.

6. The fiber laser device for moisture differential absorption lidar of claim 1, further comprising a first temperature control module providing a set ambient temperature for the first DFB fiber laser (1) and the second DFB fiber laser (2).

7. The fiber laser apparatus for differential water vapor absorption lidar of claim 1, wherein the first DFB fiber laser center wavelength is set at 1949.8nm, the second DFB fiber laser center wavelength is set at 1950.4nm, λ off-974.9 nm, and λ on-975.2 nm.

8. The fiber laser device for water vapor differential absorption lidar according to claim 1, further comprising a second temperature control module that provides a set ambient temperature for the frequency doubling module (6).

9. The use method of the optical fiber laser device for the water vapor differential absorption laser radar is characterized by comprising the following steps of:

s1, selecting a first DFB fiber laser (1) and a second DFB fiber laser (2) with the frequency stabilization within the set range of about 1950nm as seed laser sources;

s2, using the optical switching module (3), alternately outputting the laser output by the first DFB optical fiber laser (1) and the second DFB optical fiber laser (2) to the pulse modulation module (4);

s3, converting the continuous laser input into the pulse modulation module (4) into pulse laser;

s4, the output pulse laser is amplified by a doped fiber amplifier (5) and then output to a frequency doubling module (6);

s5, frequency doubling is carried out on the amplified pulse laser through a frequency doubling module (6), frequency doubling is carried out on the laser output by the first DFB fiber laser (1), and the output laser is positioned on a water vapor absorption line wing lambda off; and frequency doubling is carried out on the laser output by the second DFB optical fiber laser (2), and the output laser is positioned on the water vapor absorption line lambda on.

10. The use method of the optical fiber laser device for the water vapor differential absorption laser radar is characterized by comprising the following steps of:

s1, selecting a first DFB fiber laser (1) and a second DFB fiber laser (2) with the frequency stabilization within the set range of about 1950nm as laser sources;

s2, the two laser light sources are respectively input into the corresponding pulse modulation modules (4) to convert the continuous laser into pulse laser;

s4, amplifying the two output pulse lasers by the corresponding doped fiber amplifiers (5) respectively and outputting the amplified pulse lasers to the frequency doubling module (6);

and S5, the two beams of amplified pulse laser are subjected to frequency doubling by the corresponding frequency doubling modules (6) respectively, the frequency doubled laser correspondingly output by the first DFB optical fiber laser (1) is positioned on the water vapor absorption line lambda off, and the frequency doubled laser correspondingly output by the second DFB optical fiber laser (2) is positioned on the water vapor absorption line lambda on.

Technical Field

The invention relates to the technical field of laser radars, in particular to an optical fiber laser device for a water vapor differential absorption laser radar and a using method.

Background

Differential Absorption Lidar (DIAL) is a device that uses the difference in Absorption intensity of a measured object at different wavelengths to measure its concentration remotely. The basic principle is as follows: two beams of laser with very close wavelength intervals are emitted to the atmosphere, the wavelength of one beam of laser is positioned on the spectral absorption line of the gas to be detected and is marked as lambda on, and the laser is strongly absorbed by the gas to be detected and is called as on-line; the wavelength of the other laser beam is on the spectral absorption line wing of the gas to be measured, and is marked as lambda off, and the laser beam is basically not absorbed by the gas to be measured or is weakly absorbed and is called off-line. Because the wavelength interval of the two beams of laser is very close, the influence of atmospheric scattering and the influence of a transmitting and receiving system on the two beams of laser are basically the same, and the influence of other gas component absorption is avoided through reasonable wavelength selection, so that the interference difference can be eliminated by utilizing the echo signals of the two beams of laser, and the concentration of the gas to be measured is inverted. Compared with the water vapor Raman laser radar, the echo signal of the differential absorption laser radar is composed of the meter scattering and the Rayleigh scattering, and the echo signal is strong, so that the water vapor differential absorption laser radar can also have better detection performance in daytime.

In the differential absorption laser radar, a titanium-sapphire laser is used as a light source in the early stage, a grating is used as a rear cavity mirror, and two differential absorption wavelengths are output in a time-sharing manner by adjusting the angle of the grating. The titanium sapphire laser usually needs to use a YAG laser as a pumping source, which results in high system cost, large system volume and weight, and professional maintenance.

In recent years, a semiconductor laser is used as seed light, and after pulse modulation and amplification, dual-frequency narrow-linewidth pulse output is obtained. However, due to the limitation of laser wavelength and gain medium, the amplification factor is limited, and usually several uJ laser pulse outputs can be obtained, which limits the detection capability of the laser radar. Furthermore, the coupling between the seed source and the amplification stages is relatively complex. When an Optical Parametric Oscillator (OPO) is used for amplifying seed light output by a semiconductor laser, a laser pump OPO is needed, the system cost is high, the system volume and weight are large, and a professional is needed to maintain and operate.

Disclosure of Invention

In order to solve the problem of a laser light source in the water vapor differential absorption laser radar, the invention provides an optical fiber laser device for the water vapor differential absorption laser radar and a using method thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a optic fibre laser device for steam differential absorption laser radar, including setting gradually

The first DFB fiber laser and the second DFB fiber laser are used as seed laser light sources;

the pulse modulation module is used for modulating the continuous light output by the seed laser light source into pulse laser with a set repetition frequency;

the doped fiber amplifier is used for amplifying the pulse laser output by the pulse modulation module;

the frequency doubling module is used for doubling the frequency of the laser output and amplified by the first DFB fiber laser to obtain the laser output with the wavelength positioned on the water vapor absorption line wing lambda off; and frequency doubling the laser output and amplified by the second DFB fiber laser to obtain the laser output with the wavelength positioned on the water vapor absorption line lambda on.

The first scheme is as follows: the device comprises two sets of laser processing units consisting of a pulse modulation module, a doped fiber amplifier and a frequency doubling module, and the laser processing units are respectively used for processing the laser output by the first DFB fiber laser and the laser output by the second DFB fiber laser.

The second scheme is as follows: the device also comprises an optical switching module which gates the seed lasers output by the first DFB fiber laser and the second DFB fiber laser in a time-sharing mode, and seed lasers with two wavelengths are alternately output.

Specifically, the frequency locking module is further included and is used for locking the output frequency of the second DFB fiber laser.

Specifically, the pulse modulation module is an acousto-optic modulator AOM or a chopper.

Specifically, the apparatus further includes a first temperature control module that provides a set ambient temperature for the first DFB fiber laser and the second DFB fiber laser.

Specifically, the center wavelength of the first DFB fiber laser is set at 1949.8nm, the center wavelength of the second DFB fiber laser is set at 1950.4nm, λ off is 974.9nm, and λ on is 975.2 nm.

Specifically, the device also comprises a second temperature control module for providing the set environment temperature for the frequency doubling module.

The use method of the optical fiber laser device for the water vapor differential absorption laser radar comprises the following steps:

s1, selecting a first DFB fiber laser and a second DFB fiber laser with the frequency stabilization within the set range of about 1950nm as seed laser sources;

s2, using the optical switching module to alternately output the laser output by the first DFB fiber laser and the second DFB fiber laser to the pulse modulation module;

s3, modulating the continuous laser input into the pulse modulation module into pulse laser;

s4, amplifying the output pulse laser by a doped fiber amplifier and outputting the amplified laser to a frequency doubling module;

s5, frequency doubling the amplified pulse laser through a frequency doubling module to obtain frequency doubling the laser output by the first DFB fiber laser, wherein the output laser is positioned on a water vapor absorption line wing lambda off; and frequency doubling is carried out on the laser output by the second DFB fiber laser, and the output laser is positioned on the water vapor absorption line lambda on.

In a second scheme, the use method of the fiber laser device for the water vapor differential absorption laser radar comprises the following steps:

s1, selecting a first DFB fiber laser and a second DFB fiber laser with the frequency stabilization within the set range of about 1950nm as laser sources;

s2, inputting the two laser light sources into corresponding pulse modulation modules respectively, and modulating continuous laser into pulse laser;

s4, amplifying the two output pulse lasers by the corresponding doped fiber amplifiers respectively and outputting the amplified pulse lasers to a frequency doubling module;

and S5, frequency doubling is carried out on the two amplified pulse lasers through the corresponding frequency doubling modules respectively, the frequency doubling lasers correspondingly output by the first DFB fiber laser are positioned on the water vapor absorption wing lambda off, and the frequency doubling lasers correspondingly output by the second DFB fiber laser are positioned on the water vapor absorption line lambda on.

The invention has the advantages that:

(1) the invention uses the DFB fiber laser with the characteristics of narrow output line width, stable frequency, good environmental adaptability and the like as the seed laser, then uses the pulse modulation module to modulate the continuous seed light output by the DFB fiber laser into pulse light, and obtains the laser output with pulse energy of dozens of uJ after the pulse light is amplified by the doped fiber, thereby meeting the application requirement of the water vapor differential absorption laser radar.

(2) In the scheme, a proper differential absorption wavelength pair is selected near an absorption spectral line of water vapor molecules near 975nm, a DFB fiber laser with the output center wavelength of 1950nm can be correspondingly selected as a seed light source, and single-frequency laser pulse output near 975nm is obtained through a frequency doubling module after the DFB fiber laser is amplified by a doped fiber. And the spectral line absorption intensity of the water vapor molecules near 975nm is proper, the interference of other gas components is very small, and the method is suitable for differential absorption detection of water vapor distribution in the atmosphere.

(3) The DFB fiber laser, the all-fiber modulator AOM and the doped fiber amplifier are selected to realize the all-fiber dual-wavelength single longitudinal mode pulse laser, so that the miniaturization level and the environmental adaptability of the water vapor differential absorption laser radar can be effectively improved.

(4) And the output light of the second DFB fiber laser on the suction line is subjected to frequency monitoring and then fed back to the second DFB fiber laser for frequency stabilization, so that the output effect is optimized.

(5) The invention can promote the progress of the water vapor differential absorption laser radar technology and the application thereof in the fields of meteorology and environmental protection.

Drawings

FIG. 1 is a graph of the spectral transmittance of a water vapor molecule at a wavelength of about 975 nm.

Fig. 2 is a schematic structural diagram of a dual-wavelength single longitudinal mode pulse fiber laser device using a light switching module.

Fig. 3 is a schematic structural diagram of a dual-wavelength single longitudinal mode pulse fiber laser device using two sets of laser processing units.

The notations in the figures have the following meanings:

1. a first DFB fiber laser; 2. a second DFB fiber laser; 3. an optical switching module; 4. a pulse modulation module; 5. a doped fiber amplifier; 6. a frequency doubling module; 7. frequency locking module

Detailed Description

Example 1

As shown in FIG. 2, the fiber laser device for the water vapor differential absorption laser radar comprises a plurality of sequentially arranged fiber laser devices

The first DFB fiber laser 1 and the second DFB fiber laser 2 serve as seed laser light sources. Compared with the conventional method of adopting semiconductor laser as a seed laser light source in the water vapor differential absorption laser radar, the method can amplify the seed laser emitted by the DFB fiber laser by adopting the doped fiber, has larger gain coefficient, can obtain larger energy pulse output, and is favorable for improving the detection performance of the water vapor differential absorption laser radar.

And the optical switching module 3 is used for switching and outputting the laser output by the first DFB fiber laser 1 and the laser output by the second DFB fiber laser 2, and the output end of the optical switching module 3 is connected with the input end of the pulse modulation module 4. The optical switching module 3 is an optical switch.

A pulse modulation module 4 for modulating the continuous light as a laser light source into a pulse laser with a set repetition frequency; the pulse modulation module 4 is an acousto-optic modulator AOM or a chopper. In this scheme an acousto-optic modulator AOM.

The doped fiber amplifier 5 is used for amplifying the pulse laser output by the pulse modulation module 4;

the frequency doubling module 6 is used for doubling the frequency of the laser output and amplified by the first DFB optical fiber laser 1 to obtain the laser output with the wavelength positioned on the water vapor absorption line wing lambda off; and frequency doubling the laser output and amplified by the second DFB fiber laser 2 to obtain the laser output with the wavelength positioned on the water vapor absorption line lambda on. The frequency doubling module 6 is a frequency doubling crystal.

Preferably, the apparatus further comprises a frequency locking module 7 for locking the output frequency of the second DFB fibre laser 2. One path of continuous seed light output by the second DFB fiber laser enters a frequency locking module 7, and the output frequency of the continuous seed light is stably locked on a water vapor absorption line.

Preferably, the apparatus further comprises a first temperature control module for providing a set ambient temperature for the first and second DFB fibre lasers 1 and 2. Place first DFB fiber laser 1 and second DFB fiber laser 2 and encapsulate in first temperature control module, the control by temperature change precision can improve the stability of laser instrument output at 1mK within range, satisfies difference steam laser radar and surveys the demand.

Optimized, the device still includes and provides the second temperature control module who sets for ambient temperature for frequency doubling module 6, and frequency doubling module 6 direct relation is to the conversion efficiency and the power stability of laser, and higher frequency doubling conversion efficiency can be guaranteed to the second temperature control module, and the second temperature control module can also prevent frequency doubling crystal deliquescence, prevents that ambient temperature sharp change from causing the destruction to frequency doubling crystal structure.

The center wavelength of the first DFB fiber laser is set at 1949.8nm, the center wavelength of the second DFB fiber laser is set at 1950.4nm, and after frequency doubling, the corresponding lambda off is 974.9nm and lambda on is 975.2 nm.

A use method of a fiber laser device for a water vapor differential absorption laser radar comprises the following steps:

s1, selecting a first DFB fiber laser 1 and a second DFB fiber laser 2 with the frequency stabilization within the set range of about 1950nm as laser sources;

s2, using the optical switching module 3, alternately outputting the laser output by the first DFB fiber laser 1 and the second DFB fiber laser 2 to the pulse modulation module 4;

s3, converting the continuous laser input into the pulse modulation module 4 into pulse laser;

s4, amplifying the output pulse laser by the doped fiber amplifier 5 and outputting the amplified laser to the frequency doubling module 6;

s5, frequency doubling is carried out on the amplified pulse laser through a frequency doubling module 6, frequency doubling is carried out on the laser output by the first DFB fiber laser 1, and the output laser is positioned on a water vapor absorption line wing lambda off; and (3) frequency doubling is carried out on the laser output by the second DFB optical fiber laser 2, and the output laser is positioned on the water vapor absorption line lambda on.

Example 2

As shown in FIG. 3, the fiber laser device for the water vapor differential absorption laser radar comprises a plurality of sequentially arranged fiber laser devices

A first DFB fiber laser 1 and a second DFB fiber laser 2 as laser light sources;

a pulse modulation module 4 for processing continuous light as a laser light source into pulse laser with a set frequency; the pulse modulation module 4 is an acousto-optic modulator AOM or a chopper. In this scheme an acousto-optic modulator AOM.

The doped fiber amplifier 5 is used for amplifying the pulse laser output by the pulse modulation module 4;

the frequency doubling module 6 is used for doubling the frequency of the laser output and amplified by the first DFB optical fiber laser 1 to obtain the laser output with the wavelength positioned on the water vapor absorption line wing lambda off; and frequency doubling the laser output and amplified by the second DFB fiber laser 2 to obtain the laser output with the wavelength positioned on the water vapor absorption line lambda on.

The device comprises two sets of laser processing units consisting of a pulse modulation module 4, a doped fiber amplifier 5 and a frequency doubling module 6, wherein the laser processing units are respectively used for processing the laser output by the first DFB fiber laser 1 and the laser output by the second DFB fiber laser 2.

Preferably, the apparatus further comprises a frequency locking module 7 for locking the output frequency of the second DFB fibre laser 2. One path of continuous seed light output by the second DFB optical fiber laser 2 enters a frequency locking module 7, and the output frequency of the continuous seed light is stably locked on a water vapor absorption line.

Preferably, the device further comprises a first temperature control module for providing the set environment temperature for the first DFB fiber laser 1 and the second DFB fiber laser 2, and a second temperature control module for providing the set environment temperature for the frequency doubling module 6.

The first DFB fiber laser 1 stabilizes the frequency at 1950.4nm, the second DFB fiber laser 2 stabilizes the frequency at 1949.8nm, and λ on is 975.2nm and λ off is 974.9 nm.

The use method of the optical fiber laser device for the water vapor differential absorption laser radar comprises the following steps:

s1, selecting a first DFB fiber laser 1 and a second DFB fiber laser 2 with the frequency stabilization within the set range of about 1950nm as laser sources;

s2, the two laser light sources are respectively input into the corresponding pulse modulation modules 4, and continuous laser is converted into pulse laser;

s4, amplifying the two output pulse lasers by the corresponding doped fiber amplifiers 5 respectively and outputting the amplified pulse lasers to the frequency doubling module 6;

and S5, frequency doubling is carried out on the two amplified pulse lasers respectively through the corresponding frequency doubling modules 6, the frequency doubling lasers correspondingly output by the first DFB fiber laser 1 are positioned on the water vapor absorption line lambda off, and the frequency doubling lasers correspondingly output by the second DFB fiber laser 2 are positioned on the water vapor absorption line lambda on.

The working principle of example 1 and example 2 is as follows: the first DFB fiber laser 1 and the second DFB fiber laser 2 are used as laser light sources, output fundamental frequency continuous light is modulated into pulse laser with 9kHz repetition frequency through an acousto-optic modulator AOM, then laser output with pulse energy of dozens of uJ is obtained through a doped fiber amplifier 5, laser output with the water vapor absorption line lambda on being 975.2nm and the water vapor absorption line wing lambda off being 974.9nm is obtained through a frequency doubling module 6, and single pulse energy reaches about 30 uJ. After beam expansion, the two laser beams are emitted into the atmosphere, and because the wavelength interval of the two laser beams is very close and the absorption of other gas components except water vapor on the two wavelengths is very small, the influences of other gas substances in the atmosphere and an emitting and receiving system on the two laser beams can be considered to be basically the same, so that the interference difference can be eliminated by utilizing the echo signals of the two laser beams, and the water vapor concentration can be inverted.

It should be noted that, in the above two solutions, the center wavelength of the first DFB fiber laser is set at 1949.8nm, the center wavelength of the second DFB fiber laser is set at 1950.4nm, λ off is 974.9nm, and λ on is 975.2 nm. The present application is not limited thereto, but only by way of example.

The invention is not to be considered as limited to the specific embodiments shown and described, but is to be understood to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.