Optical switch type coherent wind lidar optical system

Abstract

The utility model relates to an optical switch type coherent wind lidar optical system, which comprises a transmitting and receiving unit, the transmitting and receiving unit comprises an optical fiber circulator, an optical switch and a plurality of telescopes with different orientations, the input end of the optical switch is connected with the optical fiber circulator, and the output end of the optical switch is connected with the optical fiber circulator. The optical switch is provided with a plurality of output ends, the output ends correspond to the telescopes respectively, and the input end of the optical switch is sequentially connected with the output ends of the optical switch so that the optical switch can be sequentially connected with the telescopes. According to the utility model, the problem of insufficient time resolution of a traditional mechanical scanning mechanism is avoided; optical switch switching is used for replacing motor driving scanning, so that vibration and noise are not generated any more; the whole optical system is optical fiber devices, optical fibers are connected with the optical fiber devices in a welding mode, the influence of the environment is small, the continuity and stability of an optical path are improved, the structure is more compact, assembly and integration are easy, and the optical system is more portable.

Description

TECHNICAL FIELD

[0001] The utility model relates to laser radar technical field especially relates to a light switch formula coherent wind finding laser radar optical system. BACKGROUND

[0002] Real-time measurement of atmospheric wind field information not only affects people's daily life, but also has an important role in environmental monitoring, aviation meteorological safety, weather warning, wind farm performance evaluation and other aspects. Especially in the field of meteorology, the detection of atmospheric wind field has an important influence on the research of monsoon climate change, atmospheric circulation system, numerical weather prediction and other aspects. Coherent wind finding laser radar has high spatial and temporal resolution and small volume, and can be carried on observation platforms such as vehicles, aircraft and satellites, which is convenient for flexible measurement of wind field information and has become the leading equipment for realizing three-dimensional detection of atmospheric wind field in the future, and has a broad application prospect in various fields.

[0003] The currently commonly used coherent wind finding laser radar optical system structure is as shown in Figure 1 The transmitting and receiving unit includes a laser, a polarization beam splitter, a lambda / 4 wave plate, a converging and collimating lens, a telescope and a wedge mirror, and the optical conversion unit includes a fiber coupler and a photoelectric balance detector. Single longitudinal mode laser pulses emitted by the fiber laser are input to one input end of the fiber coupler as a local oscillator light. Another pulse output tail fiber is connected with the collimator, and after expanding and collimating through the collimator, the laser signal reaches the lambda / 4 wave plate through the polarization beam splitter. After passing through the lambda / 4 wave plate, the linearly polarized laser pulse becomes a circularly polarized laser pulse. The circularly polarized laser pulse reaches the telescope, and then is emitted to the atmosphere through the wedge mirror after expanding and collimating by the telescope. The laser signal as the signal light is emitted to the atmosphere through the fiber ring, the telescope and the wedge mirror, and interacts with the atmosphere to generate a return signal. By changing the azimuth of the wedge mirror, different radial detection can be realized. The return signal first passes through the wedge mirror and the telescope to reach the lambda / 4 wave plate. After passing through the lambda / 4 wave plate, the polarization mode of the circularly polarized laser scattering return signal becomes linear polarization, and the polarization direction is perpendicular to the polarization direction of the outgoing laser pulse. The laser scattering return signal is reflected by the polarization beam splitter and reaches the collimator to be coupled into the other input end of the fiber coupler. The fiber coupler mixes the local oscillator light and the signal light based on the light signals obtained from the two input ends, and converts the mixed light signal into an electrical signal through the photoelectric balance detector.

[0004] However, the existing coherent wind measurement laser radar optical system uses a polarization beam splitter and a lambda / 4 wave plate to constitute an optical transceiver switch, which is difficult to assemble, is greatly affected by the environment, and in addition, the motor is driven to change the azimuth of the wedge mirror to realize the detection of different radial directions, which is difficult to operate at a high speed, and each direction needs a certain time for scanning, so there is a problem of insufficient time resolution. And the motor emits vibration and noise during operation, affecting the stability of the optical path. The motor and the gear are worn and damaged to different degrees during use, causing problems such as gear stall, jamming, positioning error and inability to reset, affecting the safety of the equipment and the continuity and accuracy of the data. Practical new type content

[0005] Therefore, the utility model discloses a light switch type coherent wind measurement laser radar optical system to solve the problems of high assembly difficulty, great environmental influence factors of optical transceiver switch in the traditional atmospheric wind field wind speed measurement mode, and the mechanical scanning mechanism is difficult to complete real-time detection task under the condition that the wind field changes quickly, and is easy to produce resonance, stall and jamming during operation, affecting the stability of the optical path, and the problems such as unable to reset accurately.

[0006] To achieve the above-mentioned purpose, the utility model adopts the following technical scheme:

[0007] The utility model provides a light switch type coherent wind measurement laser radar optical system, it includes transmitting and receiving unit, transmitting and receiving unit includes optical fiber circulator, transmitting and receiving unit still includes optical switch and N detection direction different telescopes, and N is positive integer, the input of optical switch is connected with optical fiber circulator, and the optical switch has N output ends and a plurality of output ends are respectively with N telescopes one to one with setting, and the input of optical switch is in turn with its N output end connection to make the optical switch in turn with a plurality of telescopes.

[0008] As a further improvement of the above-mentioned scheme of the utility model, N telescopes are evenly distributed in a circle and N is greater than or equal to 4.

[0009] As a further improvement of the above-mentioned scheme of the utility model, the azimuth of N telescopes is 360 ° / N, 360 ° / (N-1),..., 360 ° respectively.

[0010] As a further improvement of the above-mentioned scheme of the utility model, if N is odd, the zenith angle of all telescopes remains consistent, and if N is even, the zenith angle of the two telescopes symmetrically arranged is the same.

[0011] As a further improvement of the above-mentioned scheme of the present application, the transmitting and receiving unit further comprises a laser, the laser emitted laser is divided into two paths, one of which is used as pulse light and input to the optical switch through the fiber circulator, the optical switch sequentially transmits the pulse light to the atmosphere through a plurality of telescopes, and the backscattered light signal is received by the corresponding telescope and input to the fiber circulator through the optical switch.

[0012] As a further improvement of the above-mentioned scheme of the present application, the optical switch type coherent wind measurement laser radar optical system further comprises an optical conversion unit; the other path of the laser emitted by the laser is used as the local oscillator light and input to the optical conversion unit, and the fiber circulator inputs the backscattered light signal to the optical conversion unit; the optical conversion unit mixes the local oscillator light and the backscattered light signal, performs beat frequency on the mixed signal, and converts the mixed light signal into an electrical signal output.

[0013] As a further improvement of the above-mentioned scheme of the present application, the optical conversion unit comprises a fiber coupler and a photoelectric balance detector; the fiber coupler has two incident ends and two emission ends, and the photoelectric balance detector has two input ends; the two incident ends of the fiber coupler are used for receiving the local oscillator light and the echo signal respectively, and the fiber coupler couples and beats the local oscillator light and the echo signal; the fiber coupler divides the beat frequency signal into two parts and inputs the two parts of the signal to the two input ends of the photoelectric balance detector through the two emission ends; and the photoelectric balance detector is used for converting the two beams of light signals after beat frequency into an electrical signal output.

[0014] As a further improvement of the above-mentioned scheme of the present application, the coupling ratio of the fiber coupler is 50:50, and the beam splitting ratio is 2x2.

[0015] As a further improvement of the above-mentioned scheme of the present application, the laser emitted by the laser is a 1550nm high polarization extinction ratio single longitudinal mode laser pulse.

[0016] As a further improvement of the above-mentioned scheme of the present application, the working wave band of the optical switch is 1520-1580nm, the numerical aperture NA is 0.12, and the switching frequency of the optical switch is ≥10 11 , and the switching time is ≤200 μs.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] The utility model discloses a light switch and a plurality of telescopes, through switching light switch to make different telescope emit laser and receive signal, realize the detection of different radial, avoid the problem of time resolution of traditional mechanical scanning mechanism shortage, through light switch switching instead of motor drive scanning, no longer produce vibration and noise, whole optical system is optical fiber device, and the optical fiber is connected through fusion between optical fiber device, is less by environment influence, improves the continuity and stability of optical path, structure is more compact and easily assembled and integrated, is more portable, avoids the wear and tear of motor and gear cooperation use process to cause the problem such as jamming and unable to reset, improves the stability of system, can better suit different places, such as vehicle, ship, airborne, even the need of star.

[0019] The utility model discloses a fiber optic circulator instead of polarization beam splitter and lambda 4 wave plate realizes the integration of receiving and transmitting, and the optical fiber is connected through fusion between fiber optic circulator and other optical fiber device, easy operation, small, less environmental influence, more stable work, can better adapt to vehicle, airborne and other special environment, solve the return signal optical coupling efficiency problem, greatly improve the detection possibility of weak signal.

[0020] The utility model discloses a light switch switches and detects the wind field information of different space direction, wherein, light switch switching time is far less than 20ms, and the switching of 1 space direction is realized in about 1s by motor drive scanning. Therefore, the utility model greatly improves the time resolution of atmospheric wind field detection, can realize the accurate collection and measurement of atmospheric wind field information, and meets the demand of atmospheric wind field measurement in actual life and scientific research of people. DRAWINGS

[0021] Figure 1 It is the structural schematic diagram of coherent wind measurement laser radar optical system in prior art;

[0022] Figure 2 It is the structural schematic diagram of light switch type coherent wind measurement laser radar optical system of the utility model embodiment;

[0023] Figure 3 It is Figure 2 The optical path schematic diagram.

[0024] Sign: 1, fiber optic circulator;2, light switch;3, telescope;4, optical fiber coupler;5, photoelectric balance detector;6, laser. Specific implementation

[0025] For the purpose of facilitating the understanding of the present application, the present application will be described more fully below in connection with specific embodiments. However, the present application can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the present application to those skilled in the art.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application.

[0027] With reference to Figure 2 , Figure 3 The embodiment provides a kind of optical switch 2 formula coherent wind measuring laser radar optical system, including transmitting and receiving unit, can also include optical conversion unit.

[0028] Transmitting and receiving unit is used to emit pulsed light to atmosphere and receive backscattering light signal after being scattered by atmospheric aerosol particles, simultaneously, input local oscillation light to optical conversion unit and input backscattering light signal to optical conversion unit.

[0029] In the embodiment, transmitting and receiving unit includes laser 6, fiber optic circulator 1, optical switch 2 and four telescopes 3.

[0030] Laser 6 is used to emit laser, in the embodiment, the laser emitted by laser 6 is 1550nm high polarization extinction ratio single longitudinal mode laser pulse, laser 6 has two output ends, and is respectively marked as port1, port2, laser signal output by port1 is used as pulsed light, and laser signal output by port2 is used as local oscillation light.

[0031] Fiber optic circulator 1 is a three-port device, and the three ports are respectively marked as port3, port4 and port10, port port3 is used as pulsed light input end, port port4 is used as pulsed light output end and backscattering light signal input end, and port port10 is used as backscattering light signal output end. Laser signal input from port port3 is output from port port4 with low loss, at this time, port port10 has almost no light output. When light is input from port port4, light is output from port port10 almost without loss, and there is almost no light output at other ports.

[0032] The optical switch 2 is an optical device that switches the light in one optical channel to another optical channel by a certain method, and has one or more selectable transmission ports. Since the optical signal is not disturbed by electromagnetic radiation, the optical switch 2 can directly exchange between optical paths. In this embodiment, the optical switch 2 has one input port and four output ports, the input port is marked as port 5, and the four output ports are marked as port 6, port 7, port 8, and port 9. The input port 5 of the optical switch 2 is connected to the port 4 of the fiber ring 1, and through switching, the input port 5 can be connected to the port 6, port 7, port 8, and port 9 in turn, and the input port 5 can only be connected to one of the output ports at a time. In this embodiment, the working wavelength range of the optical switch 2 is 1520-1580 nm, the numerical aperture NA is 0.12, and the switching frequency of the optical switch is ≥10 11 , and the switching time is ≤200 μs.

[0033] In this embodiment, the number of telescopes 3 is four, and each telescope 3 detects the atmosphere in a spatial direction. Considering that different radial wind speeds are measured, the four telescopes 3 are arranged in a ring shape and symmetrically distributed, and the detection directions are different. The four telescopes 3 are connected to the four output ports of the optical switch 2, and through switching, the optical switch 2 can be connected to the four telescopes 3 in turn, and the optical switch 2 can only be connected to one of the telescopes 3 at a time. In this embodiment, the optical and mechanical properties of the four telescopes 3 are the same, and the zenith angles of the four telescopes 3 are all 16°, and the azimuth angles of the four telescopes 3 are 90°, 180°, 270°, and 360°, respectively, so that the radial wind speeds in the east, south, west, and north directions can be detected. Of course, in its embodiment, the number of telescopes 3 can also be N, generally N≥4, and the optical switch 2 also needs to be provided with N corresponding output ports; similarly, the azimuth angle also changes to 360° / N, 360° / (N-1),..., 360°; the zenith angle is also not fixed at 16°, if N is odd, all the zenith angles of the telescopes in the optical system remain the same; if N is even, the zenith angles of the axisymmetric telescopes must be the same, which is convenient for subsequent data processing; for example, the zenith angle of the telescope with an azimuth angle of 180° and 360° is 16°; the zenith angle of the telescope with an azimuth angle of 90° and 270° is 20°; so that more radial wind speeds in more directions can be detected.

[0034] The optical fiber coupler 4 is used for beam splitting or beam combining, the coupling ratio is 50:50, the beam splitting ratio is 2x2, the optical fiber coupler 4 has two incident ends and two outgoing ends, the two incident ends are respectively marked as port 11 and port 12, and the two outgoing ends are respectively marked as port 13 and port 14. The incident end port 11 of the optical fiber coupler 4 is used for receiving the local oscillator light, and the incident end port 12 is used for receiving the backscattering light signal output by the port 10 of the optical fiber circulator 1. The optical fiber coupler 4 divides the local oscillator light into two beams of light signals in a ratio of 50:50, and also divides the backscattering light signal into two beams of light signals in a ratio of 50:50, so that 50% of the local oscillator light and 50% of the backscattering light signal are coupled to be output through the outgoing end port 13 after frequency mixing, and the other 50% of the local oscillator light and the other 50% of the backscattering light signal are coupled to be output through the outgoing end port 14 after frequency mixing.

[0035] The photoelectric balance detector 5 has two input ends, and the two input ends are respectively connected with the two outgoing ends of the optical fiber coupler 4. The photoelectric balance detector 5 converts the two beams of light wave signals after frequency mixing into electrical signals for easy measurement and output. The photoelectric balance detector 5 cannot directly detect the high-frequency signal responding to the backscattering, and needs to be coherently modulated with the local oscillator light to obtain an intermediate frequency signal for detection by the detector 5. The coherent laser radar usually adopts a double-input balanced detector 5 containing two groups of detection units to process the mixed laser beams. This differential detection method can effectively reduce signal noise and improve signal detection quality.

[0036] The above structure is provided. The pulsed light of the laser 6 is sequentially input to the port 5 of the optical switch 2 through the port 1 of the laser 6, the port 3 and the port 4 of the optical fiber circulator 1. The output end of the optical switch 2 is connected with the telescope 3. The pulsed laser is sequentially output from the output end of the optical switch 2 to the corresponding telescope 3 and emitted into the atmosphere. If necessary, the shutdown of each output end of the optical switch 2 can also be controlled by a central control device. For example, there are four telescopes 3 in the optical system. The four output ends corresponding to the four telescopes 3 in the specific direction are sequentially opened by the optical switch 2. Correspondingly, when one output end is opened, the remaining three output ends are closed. The backscattering light signals in different spatial directions are received by the corresponding telescopes 3 and input to the optical fiber circulator 1 through the optical switch 2, and then input to the optical fiber coupler 4 through the optical fiber circulator 1, so that different backscattering light signals can be input into the optical conversion unit.

[0037] The embodiment is a single longitudinal mode laser pulse emitted by a fiber laser, one laser signal as a local light is input to one input end of a fiber coupler, and another laser signal as a signal light is output to port 4, an optical switch and a telescope through port 3 of a fiber circulator, and then is emitted into the atmosphere. The optical switch emits laser pulses to the corresponding detection space of the corresponding azimuth in turn by rapidly switching the optical path, and receives the echo signals generated by the interaction of the atmosphere, and the echo signals are transmitted to the fiber coupler through port 10 after input to port 4 through the telescope and the optical switch. The fiber coupler couples and beats the local light and the echo signals, and divides the signals after beating into two parts by 50 / 50 and inputs the two parts to two input ends of a photoelectric balance detector through two output ends. The photoelectric balance detector is used for converting the two optical wave signals after beating into electrical signals and outputting.

[0038] The technical features of the above embodiments can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the range disclosed in the specification.

[0039] The above embodiments only express several implementation manners of the utility model, the description is more specific and detailed, but it should not be understood as the limitation of the scope of the utility model patent. It should be pointed out that for ordinary skilled in the art, on the premise of not departing from the concept of the utility model, a number of modifications and improvements can be made, which belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent should be subject to the appended claims.

Claims

1. An optical switching coherent wind lidar optical system comprising a transmitting and receiving unit, said transmitting and receiving unit comprising a fiber-optic circulator, characterized in that, The transmitting and receiving unit further comprises an optical switch and N telescopes with different detection directions, N being a positive integer; the input end of the optical switch is connected with the fiber ring, the optical switch has N output ends, and the output ends are respectively and correspondingly arranged with the N telescopes; the input end of the optical switch is connected with the N output ends in sequence so that the optical switch is connected with the telescopes in sequence.

2. The optical-switching coherent wind lidar optical system according to claim 1, characterized in that, The N telescopes are uniformly distributed in a circle, and N≥4.

3. The optical-switching coherent wind lidar optical system according to claim 2, characterized in that, The azimuth angles of the N telescopes are 360° / N, 360° / (N-1),..., 360° respectively.

4. The optical-switching coherent wind lidar optical system according to claim 3, characterized in that, If N is an odd number, the zenith angles of all the telescopes are consistent; if N is an even number, the zenith angles of the two telescopes symmetrically arranged are the same.

5. The optical-switching coherent wind lidar optical system of claim 1, wherein, The transmitting and receiving unit further comprises a laser, the laser-emitted laser is divided into two paths, one of which is used as pulse light and input to the optical switch through the fiber ring, the optical switch transmits the pulse light to the atmosphere through the telescopes in sequence, and the backscattered light signal is received by the corresponding telescope and input to the fiber ring through the optical switch.

6. The optical-switching coherent wind lidar optical system of claim 1, wherein, The optical switch type coherent wind measurement laser radar optical system further comprises an optical conversion unit; the other path of the laser emitted by the laser is used as the local oscillator light and input to the optical conversion unit, the fiber ring inputs the backscattered light signal to the optical conversion unit; the optical conversion unit mixes the local oscillator light and the backscattered light signal, performs beat frequency on the mixed signal, and converts the mixed light signal into an electrical signal.

7. The optical-switching coherent wind lidar optical system according to claim 6, characterized in that, The optical conversion unit comprises a fiber coupler and a photoelectric balance detector; the fiber coupler has two incident ends and two emission ends, and the photoelectric balance detector has two input ends; the two incident ends of the fiber coupler are respectively used for receiving the local oscillator light and the echo signal, and the fiber coupler couples and beats the local oscillator light and the echo signal; the fiber coupler divides the beat frequency signal into two parts and inputs the two parts of the signal to the two input ends of the photoelectric balance detector through the two emission ends; the photoelectric balance detector is used for converting the two parts of the beat frequency signal into an electrical signal.

8. The optical-switching coherent wind lidar optical system according to claim 7, characterized in that, The coupling ratio of the fiber coupler is 50:50, and the beam splitting ratio is 2x2.

9. The optical-switching coherent wind lidar optical system of claim 5, wherein, The laser emitted by the laser is a 1550nm high polarization extinction ratio single-longitudinal-mode laser pulse.

10. The optical-switching coherent wind lidar optical system of claim 9, wherein, The optical switch operates in the 1520-1580nm wavelength range, has a numerical aperture (NA) of 0.12, and can switch ≥10 times. 11 Switching time ≤200μs.

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