阅读说明：本技术 一种基于dwdm光开关模块测量三维风量的光路切换通道和切换方法、及激光雷达 (Optical path switching channel and switching method for measuring three-dimensional air volume based on DWDM optical switch module, and laser radar ) 是由 卢立武 肖增利 罗浩 李五一 乔乃燕 李智 于 2021-08-16 设计创作，主要内容包括：本发明提供了一种基于DWDM光开关模块测量三维风量的光路切换通道,该通道是通过可调谐种子源激光器发出不同波段的激光,经过隔离分路、调制、放大,再通过DWDM光开关模块,进行分配到不同的对应的波长光路中的通道,其中还包括可调谐种子源激光器输出不同波长是通过可调谐种子驱动调整电流来实现的。同时还提供了包括上述光路切换通道的切换方法及激光雷达,是可调谐种子源和DWDM光开关取代原先MEMS光开关的新型方法,是能够通过采用DWDM光开关替换常规MEMS光开关,DWDM作为无源器件,无需外接供电,也不需要电路时序控制,插损较低,成本低,可靠性高,易于集成,可维护性高,满足目前批量生产激光雷达的需求。(The invention provides an optical path switching channel for measuring three-dimensional air volume based on a DWDM optical switch module, which is characterized in that the channel is a channel which is distributed to different corresponding wavelength optical paths through a DWDM optical switch module after laser of different wave bands is emitted by a tunable seed source laser, isolated, shunted, modulated and amplified, and the output of different wavelengths by the tunable seed source laser is realized by driving and adjusting current through tunable seeds. The DWDM is used as a passive device, external power supply is not needed, circuit time sequence control is not needed, insertion loss is low, the cost is low, the reliability is high, the integration is easy, the maintainability is high, and the requirement of the existing laser radar in batch production is met.)

1. An optical path switching channel based on DWDM optical switch module measures three-dimensional amount of wind, its characterized in that: the channel is a channel which emits laser with different wave bands through a tunable seed source laser (1), is distributed to different corresponding wavelength light paths through an isolation shunt, modulation and amplification and a DWDM optical switch module (8), wherein the channel is realized by adjusting current through a tunable seed driver (2) when the tunable seed source laser (1) outputs different wavelengths.

2. The utility model provides a laser radar based on DWDM photoswitch module measures three-dimensional amount of wind which characterized in that: the laser radar adopts the optical path switching channel of claim 1, and specifically comprises a tunable seed source laser (1), a tunable seed driver (2), an isolator (3), a DWDM optical switch module (8), a telescope group (9), a coupler (10), a photoelectric detector (11) and an A/D data acquisition and signal processing module (12);

the tunable seed driver (2) is used for assisting the tunable seed source laser (1) to emit laser with different wavelengths;

the tunable seed source laser (1) is used for emitting laser with different wavelengths and sending the laser to the isolator (3);

the isolator (3) divides the laser into two paths, one path of the laser passes through the DWDM optical switch module (8) and the optical path of the telescope group (9) for returning processing, and is coupled and coherent with the other path of the laser in the coupler (10);

the photoelectric detector (11) is used for converting the coupled optical signal into an electric signal and outputting a difference frequency signal;

and the A/D data acquisition and signal processing module (12) is connected to the output signal end of the photoelectric detector and is used for processing data to obtain a time domain and frequency domain diagram of the signal.

3. A lidar for measuring three-dimensional air volume based on a DWDM optical switch module according to claim 2, wherein: the device also comprises an acousto-optic modulator (4), a radio frequency driver (5) and a laser amplification module (6); the video driver (5) is used for outputting an external signal to the acousto-optic modulator (4); the acousto-optic modulator (4) is arranged at the output signal end of the isolator (3) and is used for modulating laser; and the laser amplification module (6) is arranged at the signal output end of the acousto-optic modulator (4) and is used for amplifying the output light of the modulator to proper power.

4. A lidar for measuring three-dimensional air volume based on a DWDM optical switch module according to claim 3, wherein: the optical fiber circulator (7) comprises a plurality of ports, one port is used for receiving light emitting light of the laser amplification module (6), the second port is used for emitting signal light, and the third port is used for receiving echo signal light which is returned and processed through the DWDM optical switch module (8) and the telescope group (9) in sequence.

5. A method for switching optical paths of a laser radar for measuring three-dimensional air volume based on a DWDM optical switch module according to any one of claims 2 to 4, wherein: the method comprises the following specific steps:

(i) seed source current is adjusted through a tunable seed driver (2) to tune the seed source laser (1) to emit laser of different wave bands;

(ii) dividing the laser in the step (i) into two paths by a beam splitter, wherein one path of the laser is used as local oscillation light to be input into a coupler (10) after passing through an adjustable attenuator; the other path is that the laser is modulated into pulse laser after passing through an acousto-optic modulator (4) and generates frequency shift quantity f_AOMAfter being amplified by the laser amplification module (6), the pulse laser is emitted to the atmosphere through the optical fiber circulator (7), the DWDM optical switch module (8) and the telescope group (9), the pulse laser interacts with aerosol particles moving in the atmosphere, and a backscattering signal of the aerosol generates Doppler frequency shift f_DThen returning to the DWDM optical switch module (8) and the optical fiber circulator (7) until the coupler (10) and the local oscillation light are in coherent beat frequency; the coherent beat frequency signal is converted into analog radio frequency signal by a balanced photoelectric detector (11), and the analog radio frequency signal is acquired by an A/D data acquisition and signal processing module (12)The signal is converted into a digital signal, and then the frequency f-f of the signal is calculated through algorithm processing_AOM+f_D，f_DThe amount of doppler shift generated for the aerosol backscatter signal.

6. The method for switching the optical path of the lidar for measuring three-dimensional air volume based on a DWDM optical switch module according to claim 5, wherein: DWDM optical switch module (8) divides the optical path into multiple channels, and when establishing a coordinate system, f-f is defined₀>At 0, the radial wind speed should be greater than 0, where the radial wind speedf: the total frequency of the received scattered signals; f. of_AOM: acousto-optic frequency shift, wherein the specific method for establishing a coordinate system comprises the following steps: dividing the telescope into four parts, simultaneously emitting the telescope into the atmosphere at different angles, sequentially marking the telescope with a No. 1 telescope tube at the upper right corner in the anticlockwise direction, and sequentially marking los1, los2, los3 and los 4; wherein the horizontal included angle of los1, los3, los2 and los4 is 30 degrees; los1, los2, los3 and los4 are separated by a vertical included angle of 25 degrees, so that emitted laser forms a rectangular square matrix, and a horizontal line is formed on a plane of a tested distance range by light beams n1 and n2 emitted by los1 and los2, and is taken as an upper light beam plane; the beams n3 and n4 emitted from los3 and los4 form a horizontal line on the plane of the test distance range, and the horizontal line is taken as the lower beam plane.

7. The method for switching the optical path of the lidar for measuring three-dimensional air volume based on the DWDM optical switch module according to claim 6, wherein:

two laser beams in the upper beam plane according to the geometrical relationshipThe wind speed in the sight line direction is respectively as follows:

x is then_u、y_uThe solution of (a) is:

the plane wind speed and wind direction of the upper light beam are respectively as follows:

θ_up＝arctan2(-y_u,-x_u)。

8. the method for switching the optical path of the lidar for measuring three-dimensional air volume based on the DWDM optical switch module according to claim 6, wherein: calculating the lower beam plane wind speed component v_downIn the lower beam plane, two beams of laser light according to the geometrical relationshipThe wind speed in the sight line direction is respectively as follows:

x is then_d、y_dThe solution of (a) is:

wherein, lower beam plane wind speed, wind direction do respectively:

θ_down＝arctan2(-y_d,-x_d)，

wherein eta is the laser efficiency constant, theta t: horizontal telescope transmission angle, θ up: upper flat beam angle, Vup: upper plane wind speed, Vdown: lower plane wind speed, θ down: lower plane beam angle.

9. The optical path switching method for measuring three-dimensional air volume based on DWDM optical switch module according to claim 5, characterized in that: wherein, the index and the turbulent flow state of the wind shear are calculated, and the wind speed states of different height layers are as follows:

(i) turbulent flow regime

(ii) Index of wind shear

(iii) Wind speed calculation for different height layers

Wherein STATUS (v)_los): is a flag bit, σ_los: wind speed labeling difference;average wind speed; h_lidar：

Radar mounting height; x_t: horizontally measuring the distance; θ s: a vertical beam angle; h_hub: the hub height.

Technical Field

The invention belongs to the technical field of three-dimensional air volume measuring equipment and a three-dimensional air volume measuring method, and particularly relates to an optical channel and switching method for measuring three-dimensional air volume based on a DWDM optical switch module, and a laser radar.

Background

The coherent Doppler laser radar acquires the Doppler frequency shift of the scattering signal by using the aerosol backscattering signal and the beat frequency signal of the local oscillator light, so that the wind speed information is obtained. The inversion of the three-dimensional wind field requires at least three wind speed values, and the lidar measures the wind speeds in multiple directions by a scanning mode. The general laser circulator only has a single output head, can only measure a single radial wind speed, cannot distinguish the state of one wind speed and one wind direction in an area class, and needs to add an optical device for realizing multi-channel switching in the back so as to realize a measuring mode for forming three-dimensional wind quantity in multiple directions.

The conventional optical switching method includes: (1) the mechanical CDL structure is characterized in that a scanner is additionally arranged in front of a telescope tube, an optical wedge element with the angle of 8 degrees is arranged in the center of the scanner, light can be refracted when passing through the optical wedge, an inverted cone is formed in a circle after the scanner rotates for one circle, a laser radar forms coordinate systems in several directions in a scanning area, and wind speed information of a wind field is obtained by confirming wind speeds in different directions in the coordinate systems. The scheme is not only higher in price, not too fast in frequency and relatively complex in deflection angle control, and needs a separate controller to control a scanning mode, so that the reliability is general; the loss of the bearing is large due to long-term rotation, so that the center of a light path is easy to deviate, and the radar is arranged to have a larger integral structure.

(2) The magneto-optical switch is connected to the back of the circulator, the magneto-optical switch utilizes Faraday magneto-optical effect to change the action of the magneto-optical crystal on the polarization plane of incident polarized light through the change of an external magnetic field, so that the effect of switching light paths is achieved, and lasers are transmitted and received through telescopes with different directions, so that the detection of a three-dimensional wind field is realized. The scheme has the advantages of small structure, high switching speed, high stability, low driving voltage, small crosstalk and long service life, but the price is higher, an additional signal control time sequence is needed, temperature control is needed, the insertion loss change of a device is prevented, the number of internal optical elements is too large, the consistency of device parameters is difficult to control, the manufacturing period is longer, and the requirement of batch production cannot be met.

(3) The micro-mechanical MEMS optical switch focuses light on the MEMS galvanometer through a lens, and the galvanometer is electrically tuned to couple the light into the optical fiber array after rotating in different directions, thereby achieving the effect of switching optical channels. An external circuit is required as a control signal, and a state of light leakage and light non-cutting is easily generated during timing control.

Meanwhile, the existing MEMS optical switch has the following problems:

(a) the existing method uses an MEMS optical switch, has low tolerance power, is not beneficial to the performance improvement of the existing laser radar, is easy to damage the pittail by high power, causes large insertion loss, even does not emit light, and directly damages devices; the film layer of the optical fiber array cannot bear overhigh power, the optical fiber is focused on the micro-galvanometer through the C-LENS LENS, the temperature is very high, and the reflected light directly breaks the film layer of the optical fiber array; DWDM dense wavelength division multiplexer is passive device, to power customizable, and the laser damage rete is plated to inside components and parts accessible prevents that components and parts from appearing in radar promotion performance process by corresponding problems such as high power laser breakdown and the plug loss grow that leads to, the circumstances such as light-emitting. The DWDM dense wavelength division multiplexer can use large-mode field passive optical fibers and an internal coating process to improve optical power input and output, so that the laser radar is greatly helpful for improving future large energy.

(b) The existing method uses an MEMS optical switch, is sensitive to temperature, changes the refractive index of an internal C-LENS LENS, is easy to deflect when laser is coupled to an optical fiber array, is gasified when the laser hits peripheral glue, can attach the vaporized glue to the optical fiber array, and is easy to burn an end face after light passes through the optical fiber array; the DWDM dense wavelength division multiplexer has simple internal structure, low temperature influence and no influence of lens coupling factor

(c) In the existing method, an MEMS optical switch is used, the time sequence of a circuit board is required to be accurately modulated, otherwise, the state of light leakage and light cutting or light emitting is easy to occur, so that the radar detects error data, and the error rate is high; DWDM dense wavelength division multiplexer belongs to passive device, need not outside power and signal control, through inside filter and speculum structure, screens out different wavelength, from the optic fibre output of different wavelength to reach the effect of switching the passageway.

Based on the defects of the existing method, in order to meet the requirements of low cost, high reliability and batch production of the existing wind lidar optical switch module, a new technical scheme is urgently needed.

Disclosure of Invention

The technical scheme is as follows: in order to solve the technical problems, the invention provides a novel optical channel based on a DWDM switch module and a switching method under the optical channel based on a tunable seed laser and a DWDM (wherein the DWDM is also called a dense wavelength division multiplexer), and further provides a laser radar with the optical channel structure.

The optical channel based on the DWDM switch module gives out laser of different wave bands through the adjustable seed laser, after amplifying, can distribute automatically to the wavelength light path that corresponds after through DWDM, in the atmosphere is launched to through the telescope to the back, receives atmospheric echo signal simultaneously, and echo signal also receives from corresponding passageway to obtain wind speed information.

The invention provides an optical path switching channel for measuring three-dimensional air quantity based on a DWDM optical switch module, which comprises the following specific contents: the channel is a channel which emits laser with different wave bands through a tunable seed source laser, is distributed to different corresponding wavelength light paths through a DWDM optical switch module after isolation shunting, modulation and amplification, and the output of different wavelengths by the tunable seed source laser is realized by driving and adjusting current through a tunable seed.

Meanwhile, the invention also provides a laser radar comprising the optical path switching channel, wherein the laser radar adopts the optical path switching channel as claimed in claim 1, and specifically comprises a tunable seed source laser, a tunable seed driving isolator, a DWDM optical switch module, a telescope group, a coupler, a photoelectric detector and an A/D data acquisition and signal processing module;

the tunable seed driver is used for assisting the tunable seed source laser to emit laser with different wavelengths; the tunable seed source laser is used for emitting laser with different wavelengths and sending the laser to the isolator;

the isolator divides the laser into two paths, one path of laser passes through the DWDM optical switch module and the optical path of the telescope group for return processing, and is coupled and coherent with the other path of laser in the coupler;

the photoelectric detector is used for converting the coupled optical signal into an electric signal and outputting a difference frequency signal;

and the A/D data acquisition and signal processing module is connected to the output signal end of the photoelectric detector and is used for processing data to obtain a time domain and frequency domain diagram of the signal.

As an improvement, the device also comprises an acousto-optic modulator, a radio frequency driver and a laser amplification module; the video driver is used for outputting an external signal to the acousto-optic modulator; the acousto-optic modulator is arranged at the output signal end of the isolator and is used for modulating the laser; the laser amplification module is arranged at the output signal end of the acousto-optic modulator and used for amplifying the output light of the modulator to proper power.

The optical fiber circulator comprises a plurality of ports, one port is used for receiving light emitted by the laser amplification module, the second port is used for emitting signal light, and the third port is used for receiving echo signal light which is sequentially returned and processed by the DWDM optical switch module and the telescope group.

Meanwhile, the invention also provides an optical path switching method of the laser radar for measuring the three-dimensional air volume based on the DWDM optical switch module, which comprises the following specific steps:

(i) the seed source laser is tuned to emit laser of different wave bands by adjusting the seed source current through the tunable seed drive;

(ii) dividing the laser in the step (i) into two paths by a beam splitter, wherein one path is that the laser passes through an adjustable attenuator and then is input to a coupler as local oscillation light; the other path is that the laser is modulated into pulse laser after passing through an acousto-optic modulator and generates frequency shift quantity f_AOMAfter being amplified by the laser amplification module, the pulse laser is emitted into the atmosphere through the optical fiber circulator, the DWDM optical switch module and the telescope group, the pulse laser interacts with aerosol particles moving in the atmosphere, and a backscattering signal of the aerosol generates Doppler frequency shift f_DThen returning to the DWDM optical switch module and the optical fiber circulator until the coupler and the local oscillation light are subjected to coherent beat frequency; the coherent beat frequency signal is converted into analog radio frequency signal by the balance photoelectric detector, the analog signal is converted into digital signal by the A/D data acquisition and signal processing module, and the frequency f of the signal is calculated by algorithm processing_AOM+f_D，f_DThe amount of doppler shift generated for the aerosol backscatter signal.

As an improvement, the DWDM optical switch module divides the optical path into multiple channels, and when a coordinate system is established, f-f is defined₀>At 0, the radial wind speed should be greater than 0, where the radial wind speedf: the total frequency of the received scattered signals; f. of_AOM: acousto-optic frequency shift of frequency, built thereinThe specific method of the vertical coordinate system comprises the following steps: dividing the telescope into four parts, simultaneously emitting the telescope into the atmosphere at different angles, sequentially marking the telescope with a No. 1 telescope tube at the upper right corner in the anticlockwise direction, and sequentially marking los1, los2, los3 and los 4; wherein the horizontal included angle of los1, los3, los2 and los4 is 30 degrees; the vertical included angle of the intervals of los1, los2, los3 and los4 is 25 degrees, the emitted laser forms a rectangular matrix, and los1 and light beams n1 and n2 emitted by los2 form a horizontal line on a test distance range plane, and the horizontal line is taken as an upper light beam plane; the beams n3 and n4 emitted from los3 and los4 form a horizontal line on the plane of the test distance range, and the horizontal line is taken as the lower beam plane.

As an improvement, two lasers are arranged in the beam plane according to the geometrical relationThe wind speed in the sight line direction is respectively as follows:

x is then_u、y_uThe solution of (a) is:

the plane wind speed and wind direction of the upper light beam are respectively as follows:

θ_up＝arctan2(-y_u,-x_u)。

as an improvement, the lower beam plane wind speed component v is calculated_downIn the lower beam plane, two beams of laser light according to the geometrical relationshipWind speed of sight directionRespectively, the following steps:

x is then_d、y_dThe solution of (a) is:

wherein, lower beam plane wind speed, wind direction do respectively:

θ_down＝arctan2(-y_d,-x_d)

wherein eta is the laser efficiency constant, theta t: horizontal telescope transmission angle, θ up: upper flat beam angle, Vup: upper plane wind speed, Vdown: lower plane wind speed, θ down: lower plane beam angle.

As an improvement, the index and turbulence state of the wind shear are calculated, and the wind speed states of the different height layers are as follows:

(i) turbulent flow regime

(ii) Index of wind shear

(iii) Wind speed calculation for different height layers

Wherein STATUS (v)_los): is a flag bit, σ_los: wind speed labeling difference;average wind speed; h_lidar: radar mounting height; x_t: horizontally measuring the distance; θ s: a vertical beam angle; h_hub: the hub height.

Has the advantages that: the invention provides a technical content that a tunable seed source and a DWDM dense wavelength division multiplexer are used for replacing the method of using an optical switch of the original laser radar, and the method is a novel optical channel switching method.

Further compared with the existing conventional method, the method has the following advantages: adopt DWDM photoswitch to replace conventional MEMS photoswitch, DWDM is as passive device, need not external power supply, also need not circuit sequential control, and the insertion loss is lower, and is with low costs, and the reliability is high, easily integrates, and maintainability is high, satisfies present batch production laser radar's demand. Meanwhile, the device does not need external electric signal control, does not need an external temperature control system, can be integrated in miniaturization, can output multiple paths, has small insertion loss, can customize and change large-energy devices according to requirements, and has great help for radar improvement performance.

Wherein, insertion loss refers to insertion loss, and the ratio of the entering optical power to the output optical power of the optical fiber output head is specifically expressed as:

drawings

Fig. 1 is a schematic structural diagram of a laser radar according to the present invention.

FIG. 2 is a schematic diagram of the DWDM multiplexer according to the present invention.

Fig. 3 is a schematic diagram of the operation of the tunable seed source laser of the present invention.

FIG. 4 is a diagram of the four-beam set relationship of the laser radar of the present invention.

Detailed Description

The following examples are given to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Referring to fig. 1, the specific structure of the laser radar for measuring three-dimensional air volume based on the DWDM optical switch module of the present invention is as follows:

tunable seed source laser 1: for outputting continuous laser light of different wavelengths.

Tunable seed drive 2: for modulating the seed source laser 1 at different wavelengths.

The isolator 3: the return light is prevented from returning to the tunable laser 1, and the tunable seed source laser 1 is protected from being damaged; and the tunable seed source laser is divided into two paths of local oscillator light and signal light.

The acoustic optical modulator 4: the continuous light output from the isolator 3 is pulse-modulated by the acousto-optic modulator 4 to form a pulse laser, and the frequency changes and moves accordingly (the frequency shift amount depends on the frequency of the acousto-optic modulator 4).

The radio frequency driver 5: and outputting the external signal to the acousto-optic modulator 4 for modulation.

The laser amplification module 6: the modulator output light is amplified to a suitable power for detection.

Fiber circulator 7: the three ports are total, one port receives the light emitted by the amplification module, two ports emit signal light, and three ports receive echo signal light.

DWDM dense wavelength division multiplexer, also called DWDM optical switch module 8: the laser with different wavelengths is output to the telescope through different channels, then is emitted to the atmosphere, and receives the laser echo signal of the atmosphere through a receiving and transmitting co-location mode.

Telescope group 9: the energy is converged at the required atmospheric distance, and simultaneously, the signal of laser backscattering in the atmosphere is received.

The coupler 10: the local oscillation light output by the isolator 2 is coupled with the circulator echo signal of the optical fiber amplifier 5, and is coherent, and the coherent laser is divided into two beams and output to the balance detector 8.

The photodetector 11: and (3) performing beat frequency on the two beams of coherent light coupled by the coupler (7), converting the optical signals subjected to beat frequency into electric signals, and outputting difference frequency signals.

The A/D data acquisition and signal processing module 12: the continuous analog signal output by the balanced photodetector 8 is converted into a discrete digital signal, data processing is performed, and a time domain and frequency domain diagram of the signal is obtained.

As a specific embodiment of the present invention, the specific test method using the laser radar described above is:

the current of a tunable seed source laser 1 is adjusted through a tunable seed driver 2 to control the tunable seed source to output continuous laser with different wavelength, the laser passes through an isolator 3 or a branching unit, one path of the laser is divided into local oscillator light serving as beat frequency and the other path of the laser is divided into signal light on a main light path, meanwhile, a radar circuit board provides a radio frequency driver 5 for synchronously modulating signals, the radio frequency driver 5 modulates the signals for an acousto-optic modulator 4, the signal light passes through the acousto-optic modulator 4, the signal light is modulated into pulse laser and generates a frequency shift amount f corresponding to the frequency of the acousto-optic modulator 4_AOM。

The optical fiber amplifier 6 is amplified to the power required by detection; the output pulse amplification laser is input from one port of the optical fiber circulator 7, is output from two ports of the optical fiber circulator 7, is accessed into the DWDM optical switch module 8 to perform channel switching of different wavelengths, is emitted onto aerosol in the atmosphere through the telescope group 8, has a backscattering effect after encountering the aerosol, receives backscattering signals through the telescope group 9 at the moment, and passes through the optical fiber circulator 7; the return optical signal and one local oscillator light of the shunt/isolator 3 are coupled into the coupler 10, and are subjected to coherent beat frequency and divided into two beams; the two coherent beat frequency light signals are input to the photoelectric detector 11, the photoelectric detector 11 converts the light signals into electrical signals, and the electrical signals are input to the a/D data acquisition and signal processing module 12.

The tunable seed driver 2 adjusts the tunable seed source laser 1 to emit laser with different wavelengths through the following settings: the laser has a sampling grating as a reflection grating at each of two ends of the resonant cavity. The grating spacing of the two sampled gratings is designed to be slightly different. The resulting spectra will have different mode spacing. Resonant amplification of the light is only possible if the modes are at the same time on both fiber reflection peaks. The reflection spectrum of one of the gratings is shifted by changing the injected current, so that the coincidence position of the reflection peaks is changed, and output light with different frequencies is obtained. Similarly, a first-stage phase area is arranged in the middle and also serves as a fine adjustment area, quasi-continuous wavelength adjustment is realized by changing oscillation positions of modes through the fine adjustment area, the range can reach hundreds of nanometers, and the selected wavelength is finer.

Optionally, a plurality of different wavelengths are modulated by increasing current, one path of light is led out to enter the etalon, and wavelength stabilization is realized through power change, current change and voltage change, mainly because the wind speed and the wavelength are related in wind speed inversion, and the wavelength precision influences the wind speed precision.

The DWDM optical switch module 8, also called DWDM dense wavelength division multiplexer, works according to the following principle: similar to multiple WDM devices integrated together. After passing through DWDM, multiple wavelengths are separated by wavelength division multiplexer. Coupling a plurality of wavelength composite lasers modulated by the DBR tunable seed source laser to a DWDM optical device through optical fibers, refracting the lights into each optical fiber array through a prism, placing a filter of a dielectric film at the front end of each optical fiber array, and transmitting the lights into the optical fibers through the filter only if the wavelength of the lights is within the filtering range; otherwise, the filter plate which can not pass through the wavelength can be reflected back by the filter plate, at the moment, a layer of reflecting film is plated on the edge of the module, the light reflected back by the first filter plate is reflected to the port of the next optical fiber array again, and the filter plates with different wavelengths are placed at the same next port. The method is used for realizing the optical switching by sequentially and repeatedly acting, finding out proper wavelengths through back-and-forth reflection of different filters and reflectors, and then enabling light to enter corresponding ports of the optical fiber array, so that most wavelengths in the multimode optical fiber are decomposed into single wavelengths to be output from different wavelength channels. Because the optical switch module in the radar system needs low insertion loss, high return loss, high withstand power, 18dB of polarization state and high reliability, the DWDM key parameters can well meet the requirements.

Example 1

The method for switching the optical path of the laser radar for measuring the three-dimensional air volume based on the DWDM optical switch module comprises the following specific steps:

(i) the seed source current is adjusted through the tunable seed driver 2 to tune the seed source laser 1 to emit laser of different wave bands;

(ii) dividing the laser in the step (i) into two paths by a beam splitter, wherein one path of the laser is used as local oscillation light to be input into the coupler 10 after passing through an adjustable attenuator; the other path is that the laser is modulated into pulse laser after passing through the acousto-optic modulator 4 and generates frequency shift quantity f_AOMAfter being amplified by the laser amplification module 6, the pulse laser is emitted to the atmosphere through the optical fiber circulator 7, the DWDM optical switch module 8 and the telescope group 9, the pulse laser interacts with aerosol particles moving in the atmosphere, and a backscattering signal of the aerosol generates Doppler frequency shift f_DThen returning to the DWDM optical switch module 8 and the optical fiber circulator 7 until the coupler 10 beats frequency coherently with the local oscillation light; the coherent beat frequency signal is converted into an analog radio frequency signal by a balanced photoelectric detector 11, the analog signal is converted into a digital signal by an A/D data acquisition and signal processing module 12, and then the frequency f of the signal is calculated by algorithm processing_AOM+f_D，f_DThe amount of doppler shift generated for the aerosol backscatter signal.

Since f is known_AOMBy the formula v ═ f_Dλ/2 (wherein f)_DCalculating the wind speed (c-3-10) of different distances D-C/2 for the Doppler frequency shift quantity generated by the aerosol backscattering signal, wherein lambda is the laser wavelength, v is the wind speed in the light detection direction) and the pulse laser flight time delta T²m/s, the speed of light). Because the laser radar measures the wind speed change information of a wind field, the single channel can only detect the radial wind speed of the laser radar, and cannot measure the wind direction and the change state; as shown in fig. 1, the light splitting of the light path into multiple channels can realize inversion of wind direction, wind speed and changing state of a three-dimensional wind field.

(1) Measuring radial wind velocity v₁、v₂、v₃、v₄The calculation formula is as follows:

when f-f is defined according to the previous coordinate system₀>At 0, the radial wind speed should be greater than 0, so for the resulting radial wind speed, in practice, v is-v, where f: the total frequency of the received scattered signals; f. of_AOM: acousto-optic frequency shift.

The telescope is divided into four parts and is shot into the atmosphere at different angles. According to the anticlockwise direction, the upper right corner is taken as a No. 1 telescope tube, and los1.los2.los3.los4 are marked in sequence; wherein the horizontal included angle of los1 and los3 at intervals of los2 and los4 is 27 degrees; los1, los2, los3 and los4 are separated by 15 degrees of vertical included angle, so that the emitted laser can form a rectangular matrix, as shown in fig. 4. The beams n1 and n2 emitted by los1 and los2 form a horizontal line on a test distance range plane, and the horizontal line is taken as an upper beam plane; the beams n3 and n4 emitted from los3 and los4 form a horizontal line on the plane of the test distance range, and the horizontal line is taken as the lower beam plane.

(2) Calculating the upper beam plane wind velocity component v_up。

In the upper beam plane, two beams of laser light according to the geometrical relationshipThe wind speed in the sight line direction is respectively as follows:

x is then_u、y_uThe solution of (a) is:

therefore, the upper beam plane wind speed and wind direction are respectively:

θ_up＝arctan2(-y_u,-x_u)

(3) calculating the lower beam plane wind speed component v_down。

In the lower beam plane, two beams of laser light according to the geometrical relationshipThe wind speed in the sight line direction is respectively as follows:

x is then_d、y_dThe solution of (a) is:

therefore, the lower beam plane wind speed and wind direction are respectively:

θ_down＝arctan2(-y_d,-x_d)

at this time, the wind speed and wind direction states of the upper and lower beam planes are obtained, and then the index and turbulence state of the wind shear and the wind speed state of the height layer are calculated.

(4) Turbulent flow regime

(6) Index of wind shear

(7) Wind speed calculation for different height layers

Wherein STATUS (v)_los): is a flag bit, σ_los: wind speed labeling difference;average wind speed; h_lidar: radar mounting height; x_t: horizontally measuring the distance; θ s: a vertical beam angle; h_hub: the hub height.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.