CN101825713A - 2 mu m all-fiber coherent laser Doppler wind finding radar system - Google Patents
2 mu m all-fiber coherent laser Doppler wind finding radar system Download PDFInfo
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Abstract
The invention discloses a 2 mu m all-fiber coherent laser Doppler wind finding radar system, which consists of a 2 mu m off-axis Cassegrain optical antenna system, a 2 mu m laser beam splitting system, a 2 mu m seed implantation laser amplifier, a 2 mu m monitoring detector system, and a 2 mu m balanced heterodyne detection system. The system overcomes the defect of ambient interference existing in a free space optical path, overcomes the influence of shot noise on heterodyne reception signal-to-noise ratio, and solves the problems of all fiber and miniaturization of the 2 mu m all-fiber coherent laser Doppler wind finding radar system, so that the 2 mu m all-fiber coherent laser Doppler wind finding radar system has a more compact structure. In addition, the system has the characteristics of safe laser for human eye, optical path connection by adopting flexible optical fiber devices, high operability and stability, low cost, good real time, long effectively measured distance, high measurement accuracy (speed measurement and distance measurement) and the like, and has high practical value in the field of coherent laser Doppler wind finding radar.
Description
Technical field
The present invention relates to a kind of coherent laser Doppler windfinding radar system, particularly a kind of eye-safe 22 mu m all-fiber coherent laser Doppler wind finding radar systems of use 2 mu m all-fiber acousto-optic frequency shifters.
Background technology
Traditional radar system structure all is to adopt the free space light channel structure, and shortcoming is that structural volume is big, owing to adopted a large amount of optical elements, its cost height is regulated difficulty, poor stability, and operability is not strong, and needs calibration adjustments repeatedly.
Along with developing rapidly of laser technology and optical communication technology, particularly fast development of optical fiber, brought opportunity for the laser radar system structure optimization.Therefore, a lot of researchers have both at home and abroad all been transferred to sight on the optical fiber technology, wish that the optical fibre device of high beam transmission quality solves the variety of problems that the conventional radar systems structure exists by low-cost.
Until now, Chinese scholars has proposed the multiple technologies scheme, particularly the radar system structure of optical communicating waveband has fully reached the requirement of full fiberize and miniaturization, and for optical communication wave band 1.5 μ m radar systems commonly used, its major advantage is that the light intensity that can bear of human eye is higher more than 10 times than 2 μ m places.But this laser technique is not overripened, and effectively measuring distance is near, and efficient is low, makes the radar system of optical communicating waveband fail to be widely used.
Over past ten years, 2 μ m laser instruments have obtained develop rapidly.2 μ m laser instrument principal features are: system need not refrigeration, pump energy coupling efficiency height, and stability is strong, good beam quality, the life-span is long, compact conformation.Especially the diode pumping solid laser about 2 μ m is the optimum matching of coherent laser radar.In order to improve resolution and the analysis precision that the microvortex flow disturbance is measured, 2 mu m coherent laser Radar Development have been promoted, at present, states such as the U.S., Britain, Germany, France, Holland, Ireland, Japan all are devoted to the research of 2 μ m solid state lasers, detector, optical system and performance test and application facet such as measurement earth atmosphere, earth wind field, and this makes 2 mu m coherent laser Doppler anemometry radars become domestic and international research focus.
But the development of 2 μ m optical fibre devices is relatively backward, does not catch up with the paces of 2 μ m laser technique development.Therefore, all there is problem separately in the structure of 2 present mu m coherent laser Doppler anemometry radar systems, promptly do not solve the full optical fiber miniaturization issues of receiving optics fully, can not satisfy the requirement of vehicle-mounted at present, unloaded and spaceborne 2 mu m coherent laser Doppler anemometry radar system miniaturizations.
In a word, all there is deficiency more or less in the technical scheme of existing 2 mu m coherent laser Doppler anemometry radar system structure optimizations, can't reach simultaneously that cost is low, the requirement of eye-safe, good stability, good, workable, the effective far measuring distance of real-time, the high and full optical fiber miniaturization of measurement (test the speed and find range) precision.
Summary of the invention
Therefore, task of the present invention provides a kind of eye-safe 2 mu m coherent laser Doppler anemometry radar systems of use 2 mu m all-fiber acousto-optic frequency shifters.
The invention provides a kind of 22 mu m all-fiber coherent laser Doppler wind finding radar systems, it is characterized in that: 22 mu m all-fiber coherent laser Doppler wind finding radar systems comprise that this 2 μ m transmitting-receiving is closed and put from axle cassegrain optics antenna system, 2 μ m laser beam light splitting systems, 2 μ m linear polarization seed injection laser amplifier stages, 2 μ m monitoring detector systems and 2 μ m balanced type heterodyne detection systems.Described 2 μ m seed injection laser amplifier stages comprise 2 μ m continuous lines polarization laser seed sources, 2 μ m linear polarization pulse laser amplifier stages, 2 mu m all-fiber acousto-optic frequency shifters, the online fiber optic splitter of 2 μ m and 2 μ m beam splitters.Described 2 mu m all-fiber acousto-optic frequency shifters are under the effect of radio-frequency (RF) driving signal source, produce zero level and first-order diffraction light respectively, first-order diffraction light keeps the frequency of incident laser, and first-order diffraction light will produce frequency shifts with respect to incident laser, and its frequency shifts size equals the frequency in radio-frequency (RF) driving signal source.The diffraction efficiency of 2 mu m all-fiber acousto-optic frequency shifters is 95%, bandwidth 10MHz, the shift frequency scope is 95～105MHz, radio-frequency driven power 0.5W, centre frequency 100MHz, the Bragg diffraction angle is 41 °, the employed acousto-optic crsytal of 2 mu m all-fiber acousto-optic frequency shifters is an oxide glass, its refractive index is 2.7, and laser damage threshold is 3W/mm
2, the velocity of sound is 2.52 * 10
3M/s, quality factor are 1.64x10
-13m
2/ w, and laser input, zero level and the one-level of 2 mu m all-fiber acousto-optic frequency shifters be 2 μ m single-mode polarization maintaining fibers output entirely, and the input and output port type is FC/APC.2 μ m continuous lines polarization seed laser emitted laser are divided into two bundles after by online fiber optic splitter, and wherein a branch of seed light is as local oscillator light, and local oscillator light is divided into two bundles by online fiber optic splitter; Another bundle seed light is injected into behind 2 mu m all-fiber acousto-optic frequency shifters shift frequencies in the 2 μ m linear polarization pulse laser amplifier stages, the linearly polarized laser that amplifies through amplifier stage is divided into two bundles by 2 μ m spectroscopes, and reflected light is coupled into by 2 μ m single mode collimating apparatuss and is injected in the 2 μ m monitoring detectors after optical fiber and a branch of local oscillator light close bundle by bundling device; And transmitted light is expanded bundle by pre-beam-expanding system, expand linearly polarized light incident behind 2 μ m light laser cube polarization splitting prisms and quarter-wave plate of bundle, to the secondary mirror reflecting surface of optical antenna, linearly polarized light is reflexed on the primary mirror reflecting surface by secondary mirror again afterwards, final directive atmosphere; Behind telescope primary mirror, secondary mirror, quarter-wave plate, reflected successively again by the light of atmospheric backscatter by 2 μ m light laser cube polarization splitting prisms, reflected light is coupled into optical fiber by 2 μ m single mode fiber collimators behind 1/2nd wave plates, enter to be injected in the 2 μ m balanced type detectors after the linearly polarized laser of optical fiber and another Shu Benzhen light close bundle by online optical-fiber bundling device.
In the 2 above-mentioned 2 mu m all-fiber coherent laser Doppler wind finding radar systems, described 2 μ m comprise optical antenna primary mirror and secondary mirror from axle cassegrain optics antenna system, primary mirror effective aperture 150mm, secondary mirror effective aperture 10mm, primary mirror is 190mm from the axle amount, and secondary mirror is measured 12.67mm from axle.
In the 2 above-mentioned 2 mu m all-fiber coherent laser Doppler wind finding radar systems, described optical antenna primary mirror and surface, secondary mirror reflecting part are coated with the high-reflecting film that increases the laser beam reflection efficiency.
Further, in the described 22 mu m all-fiber coherent laser Doppler wind finding radar systems, the face type on described optical antenna primary mirror and surface, secondary mirror reflecting part is generally sphere, ellipsoid, hyperboloid and parabola.
In the 2 above-mentioned 2 mu m all-fiber coherent laser Doppler wind finding radar systems, described 2 μ m laser beam light splitting systems comprise 2 μ m light laser cube polarization splitting prisms, quarter-wave plate and 1/2nd wave plates, and the light splitting surface of described 2 μ m light laser cube polarization splitting prisms is coated with multilayer particular polarization film.
Further, described multilayer particular polarization film is all-trans to the P polarized light to S polarized light full impregnated.
In the 2 above-mentioned 2 mu m all-fiber coherent laser Doppler wind finding radar systems, described 2 μ m seed injection laser amplifier stages comprise 2 μ m continuous lines polarization laser seed sources, 2 μ m linear polarization impulse laser amplifiers, the online fiber optic splitter of 2 μ m and 2 μ m beam splitters.
In the 2 above-mentioned 2 mu m all-fiber coherent laser Doppler wind finding radar systems, described 2 μ m monitoring detector systems comprise 2 μ mInGaAs photodetectors, optical-fiber bundling device and 2 μ m optical fiber collimators.
Further, the coupling efficiency of described 2 μ m single mode fiber collimators is more than 80%.
In the 2 above-mentioned 2 mu m all-fiber coherent laser Doppler wind finding radar systems, described 2 μ m balanced type heterodyne detection systems comprise 2 μ m balanced type InGaAs photodetectors, 2 μ m single mode fiber collimators and online optical-fiber bundling device.
Further, described 2 μ m balanced type InGaAs photodetectors can reach the diffraction limit level, fully eliminate shot noise to the heterodyne influence on signal-to-noise ratio (SNR).
Take technique scheme, can successfully remedy the defective that there is environmental interference in the free space light path, overcome shot noise to the heterodyne detection influence on signal-to-noise ratio (SNR), and successfully solved the problem of the full optical fiber miniaturizations of 22 mu m all-fiber coherent laser Doppler wind finding radar systems, make 22 mu m all-fiber coherent laser Doppler wind finding radar system architectures compact more, in addition, the present invention have simultaneously laser for eye-safe, light path adopt the flexible optical fibre device connect, workable,
Good stability, characteristics such as cost is low, real-time good, effective far measuring distance and measurement (test the speed and find range) precision height have very high practical value in coherent laser Doppler windfinding radar field.
Description of drawings
Below, describe embodiments of the invention in conjunction with the accompanying drawings in detail, wherein:
Fig. 1 is that 2 μ m are from axle cassegrain optics antenna system configuration synoptic diagram;
Fig. 2 is 2 μ m beam splitting system structural representations;
Fig. 3 is 2 mu m all-fiber acousto-optic frequency shifters structural representations;
Fig. 4 is 2 μ m single mode fiber collimator structural representations;
Fig. 5 is 2 μ m balanced type photodetector structure synoptic diagram;
Fig. 6 is a kind of structural representations of 22 mu m all-fiber coherent laser Doppler wind finding radars;
Embodiment
Fig. 1 is that 2 μ m are from axle cassegrain optics antenna system configuration synoptic diagram.Comprise 45 ° of plane mirrors 101 of light beam steering device and 102, optical antenna primary mirror 103, secondary mirror 104 and atmosphere 105.Described optical antenna adopts transmitting-receiving to close the two emission-type structures from the axle Cassegrain of putting, adopt quadric surface to reach in the double reflection system to eliminate various primary aberrations, the parameter designing of emission coefficient to consider mainly that the light beam of laser blocks and the speckle effect of laser radiation after the target.The emission beam diameter 10mm of transmitting optics antenna system, transmitting optics antenna system enlargement factor is 15 times, and the primary mirror bore is 160mm, and effective aperture is 150mm; Inferior aperture of mirror is 12.7mm, and the effective aperture is 10mm.The aspheric surface face type that primary mirror 103 and secondary mirror 104 are all selected for use is the secondary parabola.103 types of primary mirror are parabolic, primary mirror 103 vertex curvature radius 1500mm, primary mirror be 190mm from the axle amount, it is parabolic that 104 types of secondary mirror are similarly, the radius-of-curvature 100mm on secondary mirror 104 summits, secondary mirror 104 be 12.67mm from the axle amount.System's field angle is 0.1mrad, has reached the diffraction limit level; Receiving the effective main bore of optical antenna is 150mm, and instantaneous field of view angle and coherent reception field angle are mated 2 ω=0.017mrad, the effective focal length f ' of system=4500mm, and image quality requires to reach the diffraction limit level, and wavefront distortion requires less than λ/20; When the effective aperture of optical antenna system is 150mm, wavelength is 2 μ m, when operating distance is R=1 10km, in weak turbulent flow
Under the situation, the antenna efficiency of system is 0.51, at strong turbulence
Down, the antenna efficiency of system is 0.03.Wherein, optical antenna primary mirror 103 is made by special material, described special material comprises glass, melts quartz, silicon chip, transparent plastic and the little metal material of thermal expansivity, its primary mirror reflecting surface is coated with the high-reflecting film that increases the laser output laser beam reflection efficiency, reflecting surface face type is a hyperboloid, also can make sphere, ellipsoid and parabola according to concrete needs.Optical antenna secondary mirror 104 is made by special material, described special material comprises glass, melts quartz, silicon chip, transparent plastic and the little metal material of thermal expansivity, secondly specularly reflecting surface is coated with the high-reflecting film that increases the laser output laser beam reflection efficiency, secondary mirror 104 reflecting surface face types are parabolic, can make sphere, ellipsoid and hyperboloid by actual needs equally.45 ° of plane mirrors 101 of light beam steering device and 102 surfaces are coated with the high-reflecting film that increases the laser beam reflection efficiency.When laser incides on 45 ° of plane mirrors 101, careful regulate that incident light is reflected on 45 ° of plane mirrors 102 when making its normal direction and incident light optical axis direction at 45, after same the adjusting its reflected light is incided on the reflecting surface of optical antenna secondary mirror 104, the light that is reflected by secondary mirror 104 incides again on optical antenna primary mirror 103 reflectings surface, the direct directive atmosphere of light that is reflected by primary mirror 103.
Fig. 2 is 2 μ m beam splitting system structural representations.Comprise pre-beam expander 201,2 μ m light laser cube polarization splitting prisms 202, quarter-wave plate 203,1/2nd wave plates 204, optical antenna 205 and atmosphere 206.Wherein, the beam split part surface 207 of 2 μ m light laser cube polarization splitting prisms 202 is coated with special polarizing coating, the characteristics of this polarizing coating are to be all-trans at specific S polarized light, the P polarized light of S specific with it polarization direction quadrature is full impregnated then, 2 μ m light laser cube polarization splitting prisms are made by the high permeability material, and described high permeability material comprises K9 glass, melts quartz, CaF
2, MgF
2, ZnSe, germanium wafer and silicon chip etc., its structure is generally plate and cubic type, can be according to any type selecting of concrete needs.When incident S polarized light incides light splitting surface 207 after pre-beam expander expands bundle, regulate the light splitting surface position of polarization spectroscope, make its most transmittance, the S polarized light of transmission becomes circularly polarized light through quarter-wave plate 203, this circularly polarized light enters atmosphere 206 after by optical antenna, process atmosphere 206 backward scattered circularly polarized lights are through identical quarter-wave plate 203, because variation has taken place in its polarization direction, become the P polarized light, reflectance coating plays a leading role in the time of on inciding light splitting surface 207, overwhelming majority light is reflected, and reflected ray polarized light normal incidence to two/wave plate 204 carries out becoming the S polarized light again after polarization state is proofreaied and correct.
Fig. 3 is 2 mu m all-fiber acousto-optic frequency shifters structural representations.Comprise laser incident end 301, convergent lens 302, collimation lens 303, one-level light output end 304, collimation lens 305, zero level output terminal 306, radio-frequency (RF) driving signal source 307 and acousto-optic medium 308.The diffraction efficiency of 2 mu m all-fiber acousto-optic frequency shifters is 95%, bandwidth 10MHz, the shift frequency scope is 95～105MHz, radio-frequency driven power 0.5W, centre frequency 100MHz, the Bragg diffraction angle is 41 °, the employed acousto-optic crsytal of 2 mu m all-fiber acousto-optic frequency shifters is an oxide glass, its refractive index is 2.7, and laser damage threshold is 3W/mm
2, the velocity of sound is 2.52 * 10
3M/s, quality factor are 1.64x10
-13m
2/ w, and laser input, zero level and the one-level of 2 mu m all-fiber acousto-optic frequency shifters be 2 μ m single-mode polarization maintaining fibers output entirely, and the input and output port type is FC/APC.
2 mu m all-fiber acousto-optic frequency shifters are based on that the Bragg diffraction principle makes, and it can carry out frequency modulation (PFM) to incident light under the effect of radio driver, make one-level optical diffraction frequency produce frequency displacement.When 2 μ m continuous laser seed source laser emission laser is divided into two bundles through the online fiber optic splitter of 2 μ m after, a branch ofly enter online fiber optic splitter, another Shu Ze enters in the 2 mu m all-fiber acousto-optic frequency shifters, 2 mu m all-fiber acousto-optic frequency shifters are worked under 307 effects of radio-frequency (RF) driving signal source, produce first-order diffraction light, first-order diffraction light is injected in the 2 μ m laser pulse amplifier, linearly polarized light after power amplification is divided into a branch of reflected light and a branch of transmitted light by 2 μ m spectroscopes, usually the efficient of transmitted light is higher, about 99%, transmitted light can be through carrying out the pre-expansion bundle with beam expander to incident beam.And the benefit of using 2 mu m all-fiber acousto-optic frequency shifters be can frequency shifts 100MHz with laser instrument about.Because 2 mu m all-fiber laser windfinding radar systems adopt the heterodyne detection mode to come the Doppler shift of atmospheric sounding echo to be finally inversed by atmosphere dimensional wind information indirectly, usually the measuring wind speed accuracy requirement is 1m/s, wind speed is ± 35m/s, and for 2 mu m all-fiber laser windfinding radar systems, the corresponding air speed bandwidth is 70MHz, therefore, needs according to digital signal processing, in order to demodulate the size of wind speed, with regard to requiring the centre frequency of signal Processing is moved about 100MHz, handling in addition like this, a benefit is exactly the 1/f noise that can overcome signal processor, so, just can utilize 2 mu m all-fiber acousto-optic frequency shifters to reach the purpose that centre frequency moves 100MHz.This is fine understanding for those of ordinary skill in the art.
Fig. 4 is 2 μ m single mode fiber collimator structural representations.This optical fiber collimator comprises optical fiber pigtail 401, optical fiber contact pins 402, metal sleeve 403, gradient-index lens 404, glass bushing 407 and the joints of optical fibre 406.Wherein, single-mode fiber tail optical fiber 401 penetrates and is fixed on contact pin 402 centers, polishing is carried out on contact pin 402 surfaces after, gradient-index lens 404 and optical fiber contact pins 402 are put into glass bushing together realize aiming at; metal sleeve will be enclosed within the glass bushing outside simultaneously, play a protective role.Described gradient-index lens 404 adopts inclined-plane, the spherical connection with optical fiber contact pins 402 end faces, the middle body of contact jaw keeps sphere, and the other parts of end face are processed into the inclined-plane, and the angle that makes end face and shaft axis of optic fibre is less than 90 °, can increase contact area like this, make optically-coupled tightr.When end face and shaft axis of optic fibre angle are 8 °, insert loss less than 0.5dB, the loss of polishing inclined plane back reflection can reach 68dB, and having isolated rear orientation light admirably influences laser instrument.Simultaneously, the outer assembly of contact pin 402 adopts metal or nonmetallic material, and the inclined-plane that contact pin 402 contacts with gradient-index lens 404 must carry out milled processed, and the other end adopts crooked limiting member to support optical fiber or optical fiber flexible-cable with release stress usually.Gradient-index lens 404 is made by transparent material, described transparent material comprises silicon chip and oxide glass etc., the incident end face of its gradient-index lens 404 is shaped as sphere, also can make plane, ellipsoid, the conical surface and lozenges according to actual needs, two end faces of gradient-index lens are coated with the anti-reflection film that increases testing light source emission light beam efficiency of transmission.Glass bushing 407 is made by transparent material, and described transparent material comprises K9 glass, melts quartz, transparent plastic and pottery.Metal sleeve 403 is made by metal material, and described metal material comprises gold, copper, aluminium, steel etc.The used 2 μ m optical fiber collimator external diameters of system are 15mm, and effective clear aperture 10mm longly is 50mm, are about 86% for the coupling efficiency of quasi-parallel light.Each device is assembled according to shown in Figure 4, and when laser incided gradient-index lens 404 surfaces, the position of collimating apparatus was regulated in carefulness, can find the position of coupling efficiency maximum.
Fig. 5 is 2 μ m balanced type photodetector structure synoptic diagram.Shown in Fig. 5 (b), comprise flashlight 510, local oscillator light 511, photodetector 512 and 513, prime amplifier 514 and 515, wave filter 516 and 517, totalizer or difference engine 518, electric current of intermediate frequency 519 and beam splitter 520.2 μ m balanced type photodetectors are theoretical according to the monitoring of balanced type heterodyne:
Design.Wherein, i
N1(t), i
N2(t)---represent the shot-noise current in two branch roads respectively.Used 2 μ m balanced type photodetector photosurface bores are about 1mm, bandwidth 150MHz, and sensitivity 0.65A/W can reach the diffraction limit level, fully eliminates shot noise to the heterodyne influence on signal-to-noise ratio (SNR).
When on a probe unit, making the almost completely identical PIN photodiode of two parameters simultaneously, the flashlight 510 of incident and local oscillator light are divided into two bundles through beam splitter 520 respectively, incide two of two parameter matching then respectively oppositely (or in the same way the time, one the tunnel adds 180 ° of phase shifters therein) carry out optical mixing on photodetector 513 and 514 photosurfaces, produce heterodyne signal separately, respectively by entering the wave filter 516 and 517 in the light path separately behind prime amplifier 514 and 515, after the electric current of intermediate frequency of the two-way heterodyne signal of filtering through totalizer 518 (or difference engine) output balance heterodyne electric current of intermediate frequency signal I
OutBalanced reciver is compared with the simple detector receiver, and two important advantages are arranged: 1. can effectively suppress the noise of the superfluous intensity of local oscillator laser, improve the sensitivity of system; 2. can make full use of the energy of local oscillator laser instrument.
Fig. 6 is 22 mu m all-fiber coherent laser Doppler wind finding radar structural representations.Comprise 2 μ m continuous lines polarization laser seed sources 601,2 μ m linear polarization impulse laser amplifiers 602,2 mu m all-fiber acousto-optic frequency shifters 603, online fiber optic splitter 604 and 605,2 μ m spectroscopes 606,2 μ m single mode fiber collimators 607, pre-beam expander 608,2 μ m light laser cube Amici prisms 609, quarter-wave plate 610,2 μ m are from axle cassegrain optics antenna system secondary mirror 611, primary mirror 612, / 2nd wave plates 613,2 μ m single mode fiber collimators 614, online optical- fiber bundling device 615 and 616,2 μ m monitoring detectors 617 and 2 μ m balanced type heterodyne detectors 618.
Transmitting-receiving close put after axle cassegrain optics antenna debugging finishes, 2 μ m continuous lines polarization seed lasers, 601 emitted laser are divided into two bundles after by online fiber optic splitter 604, wherein a branch of seed light is as local oscillator light, and local oscillator light is divided into two bundles by online fiber optic splitter 605; Another bundle seed light is injected into after 2 mu m all-fiber acousto-optic frequency shifters 603 in the 2 μ m linear polarization impulse laser amplifiers 602, the linearly polarized laser that amplifies through amplifier is divided into two bundles by 2 μ m spectroscopes 606, reflected light is coupled into by 2 μ m single mode collimating apparatuss 607 and is injected on the photosurface of 2 μ m monitoring detectors 617 after optical fiber and a branch of local oscillator light close bundle by online optical-fiber bundling device 615, is used for monitoring the stability of seed source laser frequency; And transmitted light is expanded bundle by pre-beam expander 608, the linearly polarized light that expands bundle incides on secondary mirror 611 reflectings surface of optical antenna behind 2 μ m light laser cube polarization splitting prisms 609 and quarter-wave plate 610, linearly polarized light is reflexed on primary mirror 617 reflectings surface by secondary mirror again afterwards, final directive atmosphere; Behind telescope primary mirror 611, secondary mirror 612, quarter-wave plate 610, reflected successively again by the light of atmospheric backscatter by 2 μ m light laser cube polarization splitting prisms 609, reflected light is coupled into optical fiber by 2 μ m single mode fiber collimators 614 behind 1/2nd wave plates 613, enter and be injected on 2 μ m balanced type detectors, 618 photosurfaces after the linearly polarized laser of optical fiber and another Shu Benzhen light close bundle by online optical-fiber bundling device 616, can observe the waveform of heterodyne signal by oscillograph, both can be finally inversed by the relevant information of wind field then through follow-up signal Processing.
Wherein, it is continuous that local oscillator light requires, and therefore, tells one the tunnel in the continuous seed source laser 601 of 2 μ m and does local oscillator light, carries out beat frequency with impulse laser amplifier 602 and echoed signal light respectively, thereby observes the heterodyne signal waveform.
The seed that the laser instrument emission coefficient adopts injects the amplification mode, well behaved laser instrument seed source 601 is injected in the modulated pulse amplifier 602, close being transmitted in the atmosphere of putting through the pulse laser that amplifies by transmitting-receiving from axle cassegrain optics antenna, afterwards with atmosphere in particulate interact to produce the echoed signal that atmosphere Doppler shift information is carried in back scattering, it closes to put from axle cassegrain optics antenna through transmitting-receiving again and receives, carry out heterodyne with local oscillator light then and obtain Doppler shift information, after observing the heterodyne signal frequency-domain waveform, just can carry out real-time atmospheric wind data acquisition by the data-signal disposal system, thereby be finally inversed by the Changing Pattern of dimensional wind information and wind shear according to Doppler shift.
It should be noted that embodiment structure and the technical scheme only in above each accompanying drawing at last in order to 22 mu m all-fiber coherent laser Doppler wind finding radar systems of the present invention to be described, but unrestricted.Although the present invention is had been described in detail with reference to embodiment, those of ordinary skill in the art is to be understood that, technical scheme of the present invention is made amendment or is equal to replacement, do not break away from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of the claim scope of the present invention.
Claims (9)
1. 2 mu m all-fiber coherent laser Doppler wind finding radar system is characterized in that: 22 mu m all-fiber coherent laser Doppler wind finding radar systems comprise that this 2 μ m transmitting-receiving is closed and put from axle cassegrain optics antenna system, 2 μ m laser beam light splitting systems, 2 μ m linear polarization seed injection laser amplifier stages, 2 μ m monitoring detector systems and 2 μ m balanced type heterodyne detection systems.Described 2 μ m seed injection laser amplifier stages comprise 2 μ m continuous lines polarization laser seed sources, 2 μ m linear polarization pulse laser amplifier stages, 2 mu m all-fiber acousto-optic frequency shifters, the online fiber optic splitter of 2 μ m and 2 μ m beam splitters.Described 2 mu m all-fiber acousto-optic frequency shifters are under the effect of radio-frequency (RF) driving signal source, produce zero level and first-order diffraction light respectively, first-order diffraction light keeps the frequency of incident laser, and first-order diffraction light will produce frequency shifts with respect to incident laser, and its frequency shifts size equals the frequency in radio-frequency (RF) driving signal source.The diffraction efficiency of 2 mu m all-fiber acousto-optic frequency shifters is 95%, bandwidth 10MHz, the shift frequency scope is 95～105MHz, radio-frequency driven power 0.5W, centre frequency 100MHz, the Bragg diffraction angle is 41 °, the employed acousto-optic crsytal of 2 mu m all-fiber acousto-optic frequency shifters is an oxide glass, and its refractive index is 2.7, and laser damage threshold is 3W/mm2, the velocity of sound is 2.52 * 103m/s, and quality factor are 1.64x10
-13m
2/ w, and laser input, zero level and the one-level of 2 mu m all-fiber acousto-optic frequency shifters be 2 μ m single-mode polarization maintaining fibers output entirely, and the input and output port type is FC/APC.2 μ m continuous lines polarization seed laser emitted laser are divided into two bundles after by online fiber optic splitter, and wherein a branch of seed light is as local oscillator light, and local oscillator light is divided into two bundles by online fiber optic splitter; Another bundle seed light is injected into after 2 mu m all-fiber acousto-optic frequency shifters in the 2 μ m linear polarization pulse laser amplifier stages, the linearly polarized laser that amplifies through amplifier stage is divided into two bundles by 2 μ m spectroscopes, and reflected light is coupled into by 2 μ m single mode collimating apparatuss and is injected in the 2 μ m monitoring detectors after optical fiber and a branch of local oscillator light close bundle by bundling device; And transmitted light is expanded bundle by pre-beam-expanding system, expand linearly polarized light incident behind 2 μ m light laser cube polarization splitting prisms and quarter-wave plate of bundle, to the secondary mirror reflecting surface of optical antenna, linearly polarized light is reflexed on the primary mirror reflecting surface by secondary mirror again afterwards, final directive atmosphere; Behind telescope primary mirror, secondary mirror, quarter-wave plate, reflected successively again by the light of atmospheric backscatter by 2 μ m light laser cube polarization splitting prisms, reflected light is coupled into optical fiber by 2 μ m single mode fiber collimators behind 1/2nd wave plates, enter to be injected in the 2 μ m balanced type detectors after the linearly polarized laser of optical fiber and another Shu Benzhen light close bundle by online optical-fiber bundling device.
2. 22 mu m all-fiber coherent laser Doppler wind finding radar systems according to claim 1, it is characterized in that, described 2 μ m comprise optical antenna primary mirror and secondary mirror from axle cassegrain optics antenna system, primary mirror effective aperture 150mm, secondary mirror effective aperture 10mm, primary mirror is 190mm from the axle amount, and secondary mirror is measured 12.67mm from axle.
3. 22 mu m all-fiber coherent laser Doppler wind finding radar systems according to claim 2 is characterized in that, described optical antenna primary mirror and surface, secondary mirror reflecting part are coated with the high-reflecting film that increases the laser beam reflection efficiency.
4. 22 mu m all-fiber coherent laser Doppler wind finding radar systems according to claim 2 is characterized in that, the face type on described optical antenna primary mirror and surface, secondary mirror reflecting part is parabola, ellipsoid, hyperboloid and sphere.
5. 22 mu m all-fiber coherent laser Doppler wind finding radar systems according to claim 1 is characterized in that, described 2 μ m laser beam light splitting systems comprise 2 μ m light laser cube polarization splitting prisms, quarter-wave plate and 1/2nd wave plates.
6. 22 mu m all-fiber coherent laser Doppler wind finding radar systems according to claim 1 is characterized in that, described 2 μ m monitoring detector systems comprise 2 μ m InGaAs photodetectors, online optical-fiber bundling device and 2 μ m single mode fiber collimators.
7. 22 mu m all-fiber coherent laser Doppler wind finding radar systems according to claim 6 is characterized in that the coupling efficiency of described 2 μ m single mode fiber collimators is more than 80%.
8. 22 mu m all-fiber coherent laser Doppler wind finding radar systems according to claim 1, it is characterized in that described 2 μ m balanced type heterodyne detection systems comprise 2 μ m balanced type InGaAs photodetectors, 2 μ m single mode fiber collimators and online optical-fiber bundling device.
9. 22 mu m all-fiber coherent laser Doppler wind finding radar systems according to claim 8 is characterized in that, described 2 μ m balanced type InGaAs photodetectors can reach the diffraction limit level, fully eliminate shot noise to the heterodyne influence on signal-to-noise ratio (SNR).
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