CN100529797C - All-fiber Raman scattering laser radar system based on wavelength-division multiplex technology for diffracting - Google Patents

Abstract

The invention discloses a full optical fiber Roman scattering laser radar system based on WDM technique multiplexer light split which comprises a laser emission system, a receiving system, a light splitting system, an optical electric probing part and a computer system; the invention is characterized of the design of the light splitting system; the light splitting system in the invention splits light by depending on the characters of the WDM technique multiplexer such as sound wave length selectivity, high spectrum resolution and strong out-of-band inhibiting capability; the invention offers five design proposals which splits light by an optical fiber Bragg raster, a cascade connection optical fiber raster coupler, a multi-layer medium thin film filter, the optical fiber raster coupler based on Mach-Zehnder interferometer and a optical fiber Fabry-Perot cavity.

Description

All-fiber Raman scattering laser radar system based on wavelength-division multiplex technology for diffracting

Technical field

The invention belongs to meteorological and environmental observation technical field, relate to a kind of to the meteorological laser radar system of observing with atmospheric environment, the all-fiber Raman scattering laser radar system that particularly a kind of demodulation multiplexer (Demultiplexer) that utilizes wavelength-division multiplex (WDM) technology carries out beam split.

Background technology

Laser radar has been widely used in research fields such as Laser Atmospheric Transmission, global climate prediction, gasoloid radiation effect and atmospheric environment as a kind of active remote sensing prospecting tools.Laser radar (Lidar:Lightdetection and ranging) system is mainly by laser transmitting system, receiving system, compositions such as beam splitting system and photoelectric detecting parts and computer system.Ultimate principle is: the pulse laser beam directive atmosphere that is sent by laser instrument, through with atmosphere in the material effect after the scattered signal that produces be received systematic collection and get off, and after the light-splitting processing of optics beam splitting system, be converted to electric signal by photoelectric detecting parts, send into computing machine and carry out data processing.

The basis of laser remote sensing is the various physical processes that interact and produced between atom, molecule and the particulate in optical radiation and the atmosphere.Mie scattering (Mie scattering) is that a kind of centre wavelength of scattering spectra is identical with laser wavelength of incidence, and the spectrum width of scattering spectra is similar to the elastic scattering of incident laser spectrum width, and it is by particle diameter quite or the scattering that causes greater than the particulate of optical maser wavelength.Rayleigh scattering (Rayleigh scattering) also is that a kind of centre wavelength is identical with laser wavelength of incidence, the elastic scattering that the interdependent atmospheric temperature of spectrum width changes, and it is the scattering phenomenon that is caused by little molecule of scatterer particle diameter ratio optical maser wavelength or atom.Raman scattering (Raman scattering) can be divided into rotary Raman and vibrating Raman scattering, it is a kind of inelastic scattering that causes by atmospheric molecule or atom, scattering spectra is distributed in the both sides of incident laser spectral line, its scattering cross-section is less a kind of in the various scattering mechanisms, is well suited for being used for atmospheric sounding temperature and Atmospheric components.

Meteorological observation mainly is the measurement of carrying out atmospheric temperature, and atmospheric environment observation mainly carries out the measurement as Aerosol Extinction and scattering coefficient, aerosol optical depth, atmospheric visibility parameter.Usually, meteorological observation laser radar and atmospheric environment observation laser radar all are to use separately independently system, because the atmospheric environment laser radar uses is rice-Rayleigh scattering signal in the atmosphere echoed signal, and these are different with the scattered signal that utilized in the meteorological observation laser radar.In order to make the same laser radar system parameter of can making weather observations, can observe atmospheric environment again, just must effectively separate each scattered signal spectral component in the atmosphere echoed signal, and detect, also to effectively utilize its mutual relationship to carry out analysis and solution.

But, because the Rayleigh scattering that Mie scattering that the cross section of Raman scattering causes with respect to gasoloid and atmospheric molecule cause is wanted a little 3-4 order of magnitude, this just need have 7 inhibition more than the order of magnitude to rice and Rayleigh scattering signal, and from strong rice, Rayleigh scattering signal, extract faint Raman line, also need the beam splitting system of laser radar that outer inhibition ability of band and very high spectrally resolved ability are arranged.In addition, also need to consider sun bias light carried out effectively filtering when surveying daytime.At present, generally adopt interference filter element, monochromatic light grid monochromator in conjunction with the atomic resonance absorption filter in the beam split scheme of rotary Raman laser radar extraction rotational raman scattering spectrum, perhaps the light-splitting method of double grating monochromator.

In recent years, along with Fibre Optical Communication Technology ground develop rapidly, generally adopt WDM technology very ripe in the optical fiber communication.The scheme that WDM technology adopted is to use identical speed to transmit the light signal of a plurality of wavelength in same optical fiber.The core optical device of wdm system is that its function of multiplexing demultiplexing device (Multiplexer/Demultiplexer) is to adopt optical means with each wavelength (channel) of close interval separately, or the Add/drop Voice Channel of realization optical wavelength (channel), the latter is commonly referred to light Add/drop Voice Channel multiplexer (Optical Add/Drop Multilexer).Be that they are respectively combination (coupling) and the device that separates (separation) wavelength optical signals, Multiplexer makes up on channel to an optical fiber of several wavelength, Demultiplexer just in time in contrast, in the reality, often a WDM device not only is Demultiplexer but also be Multiplexer.Because WDM technology has good wavelength selectivity, the spectral resolution height, the spectral response functions secondary lobe is little, and half-peak value width is little, have multiport simultaneously, volume is little, insert that loss is low, simple and compact for structure, stable performance and be easy to realize full optical fiber connection characteristics.

Therefore, the present invention uses for reference the demodulation multiplexer of WDM technology of optical fiber communication and strict wavelength selectivity thereof, high spectrally resolved ability and the outer inhibition ability of band, proposes a kind of full fiber Raman laser radar that carries out meteorological observation and atmospheric environment observation of the demodulation multiplexer light splitting technology based on WDM technology.

Summary of the invention

The objective of the invention is to propose a kind of all-fiber Raman scattering laser radar system, utilize the demodulation multiplexer of WDM to carry out beam split, one cover laser radar system carries out meteorology and atmospheric environment observation simultaneously, the final atmospheric temperature meteorologic parameter that realizes is measured, and the measurement of atmospheric environmental parameters such as atmospheric aerosol extinction coefficient and scattering coefficient, aerosol optical depth, atmospheric visibility.

The technical solution adopted in the present invention is, the all-fiber Raman scattering laser radar system based on the demultiplexer beam split of WDM technology comprises laser transmitting system, receiving system, beam splitting system and photoelectric detecting parts and computer system, and this system comprises

Laser transmitting system, Nd:YAG pulsed laser, the paired pulses laser that comprises emission pulse laser collimate and expand the beam expander of bundle, also comprise a plurality of catoptrons, and the setting of a plurality of catoptrons makes the laser vertical directive atmosphere behind the collimator and extender,

Receiving system is used for receiving the rear orientation light that produces behind the molecule of laser and atmosphere and the particle interaction, and the laser radar atmosphere echoed signal that receives is coupled to multimode optical fiber, and multimode optical fiber is sent into this atmosphere echoed signal

Multimode/single-mode fiber converter is used for converting multimode atmosphere echoed signal to the single-mode fiber signal, and sends into through single-mode fiber, or the laser radar atmosphere echoed signal that telescope receives is directly coupled to single-mode fiber, sends into then

Beam splitting system is used for the rotary Raman spectral line of echoed signal is separated with rice-Rayleigh scattering spectral line, and each scattered signal after will separating exports from corresponding ports, sends into

Photoelectric detecting parts is used for that each scattered light signal after separating is become electric signal and receives, and sends into

Computer system, be pre-loaded into meteorological and atmospheric environmental parameters inversion algorithm program, be used for the scattering spectral line signal that receives is carried out analyzing and processing, obtain the atmospheric temperature meteorologic parameter, and atmospheric aerosol extinction coefficient and scattering coefficient, aerosol optical depth, atmospheric visibility atmospheric environmental parameters value.

Beam splitting system of the present invention is used for reference the good wavelength selectivity that demodulation multiplexer had of the WDM technology of optical fiber communication, and spectral resolution is high and be with the strong characteristics of outer inhibition ability to carry out beam split.

Description of drawings

Fig. 1 is laser radar system theory of constitution figure of the present invention, and wherein, a utilizes multimode optical fiber, multimode/single mode converter, single-mode fiber transmission echoed signal to beam splitting system, and b utilizes single-mode fiber transmission echoed signal to beam splitting system;

Fig. 2 is that beam splitting system structure of the present invention is formed synoptic diagram, wherein, a is the optical fiber Bragg raster beam splitting system, b is the fibre optic grating coupler beam splitting system, c is a dielectric multi-layer optical thin film wave filter beam splitting system, d is based on the fibre optic grating coupler beam splitting system of Mach-Zehnder interferometer, and e is an optical fiber Fabry-Perot chamber beam splitting system;

Fig. 3 is the Bragg reflectance spectrum and the atmospheric molecule N of optical fiber Bragg raster in the beam splitting system of the present invention ₂, O ₂Rotational raman spectrum concern synoptic diagram;

Fig. 4 is the transmission characteristics of the FBG1 of optical fiber Bragg raster in the beam splitting system of the present invention and the reflectivity Characteristics synoptic diagram of FBG2 and FBG3, and wherein, a is the transmission characteristics synoptic diagram of FBG1, and b is the reflectivity Characteristics synoptic diagram of FBG2 and FBG3;

Fig. 5 is the intensity distribution of atmosphere echoed signal after optical splitter filters;

Fig. 6 is the measurement noise height profile figure of thermometric error when at attainable daytime and night on the Systems Theory of the present invention.

Among the figure, 1. laser transmitting system, 2. telescope receiving system, 3. beam splitting system and photoelectric detecting parts, 4. computer system, 5. first fiber optical circulator, 6. first Fiber Bragg Grating FBG (FBG1), 7. second fiber optical circulator, 8. second Fiber Bragg Grating FBG (FBG2), 9. the 3rd fiber optical circulator, 10. the 3rd Fiber Bragg Grating FBG (FBG3), 11. first photoelectric detecting parts (PMT1), 12. second photoelectric detecting parts (PMT1), 13. the 3rd photoelectric detecting parts (PMT1), 14. first fibre optic grating coupler (FBG1), 15. second fibre optic grating coupler (FBG2), 16. the 3rd fibre optic grating couplers (FBG3), 17. dielectric multi-layer optical thin film wave filters (MDTFF), 18. first lens (Lens), 19. second lens, 20. the 3rd lens, 21. the 4th lens, 22. first fibre optic interferometer (M_ZI1), 23. second fibre optic interferometer (M_ZI2), 24. the 3rd fibre optic interferometers (M_ZI3), 25. first fiber couplers (FC1), 26. second fiber coupler (FC2), 27. the 3rd fiber coupler (FC3), 28. the 4th fiber couplers (FC4), 29. the 5th fiber couplers (FC5), 30. six fibers coupling mechanism (FC6), 31. first fiber resonance cavity (F-P cavity1), 32. second fiber resonance cavities (F-P cavity2), 33. the 3rd fiber resonance cavities (F-P cavity3).

Embodiment

The present invention is described in detail below in conjunction with the drawings and specific embodiments.

The present invention is a kind of Raman lidar system that can be used for meteorological observation and atmospheric environment observation simultaneously, the system of laser radar constitutes as shown in Figure 1, wherein, a utilizes multimode optical fiber, multimode/single mode converter, single-mode fiber transmission echoed signal to beam splitting system, and b utilizes single-mode fiber transmission echoed signal to beam splitting system.Comprise laser transmitting system 1, receiving system 2, beam split and Photodetection system 3 and computer system 4, laser transmitting system 1 comprises Nd:YAG pulsed laser, collimator and extender device and a plurality of catoptron.

Laser transmitting system 1 of the present invention adopts the Nd:YAG pulsed laser, and it exports its second harmonic (λ ₀=532.25nm) as light source, and and the optics and the structure of launching.

Photodetection system is made up of first photoelectric detecting parts 11 (PMT1), second photoelectric detecting parts 12 (PMT2) and the 3rd photoelectric detecting parts 13 (PMT3), is used for that echo optical signal is become electric signal and receives.Wherein, first photoelectric detecting parts 11 detects rice-Rayleigh scattering signal, can be used for the measurement of atmospheric aerosol optical characteristics; Second photoelectric detecting parts 12, the 3rd photoelectric detecting parts 13 detect 2 rotational raman scattering signals, are used for temperature survey.

The effect of beam splitting system is that the rotary Raman spectral line in the echoed signal is separated with rice-Rayleigh scattering spectral line etc., suppresses the interference of Mie scattering, Rayleigh scattering signal and sun bias light in the temperature detection channels to the full extent.The critical piece of beam splitting system realizes that by the demodulation multiplexer of WDM technology concrete implementation is as follows respectively among the present invention:

Scheme 1

The main optical fiber Bragg Bragg grating (FBG) that adopts is realized beam split.

Fig. 2 a is depicted as an embodiment, and system comprises first fiber optical circulator 5, first Fiber Bragg Grating FBG 6, its wavelength X _bBe λ _B1=532.25nm, second fiber optical circulator 7, second Fiber Bragg Grating FBG 8, its wavelength X _bBe λ _B2=530.6nm, the 3rd fiber optical circulator 9, the 3rd Fiber Bragg Grating FBG 10, its wavelength X _bBe λ _B3=528.8nm.λ _B1, λ _B2And λ _B3Respectively corresponding rice-Rayleigh scattering signal, low quantum number rotational raman scattering signal and high quantum number Raman scattering signal make each FBG have very high reflectivity and extremely low transmissivity respectively to above-mentioned wavelength selected by design.

The atmosphere echoed signal that contains a plurality of wavelength that telescope is received is coupled into multimode optical fiber (MMF), after multimode/single-mode fiber converter conversion, the input port port1 that sends into first fiber optical circulator 5 through single-mode fiber (SMF) (or is directly coupled to single-mode fiber (SMF) with the atmosphere echoed signal that telescope receives, send into the input port port1 of first fiber optical circulator 5 then), output to the input port port2 that is connected to first Fiber Bragg Grating FBG 6 through first fiber optical circulator 5, the wavelength that first Fiber Bragg Grating FBG 6 will satisfy the Bragg condition equals λ _B1Rice-Rayleigh scattering signal reflected back first fiber optical circulator 5 in, and, receive by first photoelectric detecting parts 11 by after the output port port3 of first fiber optical circulator 5 output.This is a passage 1.At passage 1 place, by designing the parameter of first Fiber Bragg Grating FBG 6, it is very faint to make transmission cross the rice of first Fiber Bragg Grating FBG 6-Rayleigh signal, has reached the very high outer inhibiting rate of band.

Because first Fiber Bragg Grating FBG 6 is to the light no reflection events effect of other wavelength, therefore after the output port port4 of first Fiber Bragg Grating FBG 6 is crossed in the transmittance of other wavelength, enter the input port port1 of second fiber optical circulator 7 again, second Fiber Bragg Grating FBG 8 equals wavelength to λ _B2Low quantum number rotate complete reflected back second fiber optical circulator 7 of scattered signal, and after its output port port3 output, receive by second photoelectric detecting parts 12.This is a passage 2.

In like manner, other wavelength are not λ _B2The light signal transmission cross second Fiber Bragg Grating FBG 8 after, again through the 3rd fiber optical circulator 9 by the reflection of the 3rd Fiber Bragg Grating FBG 10, isolating wavelength is λ _B3High quantum number Raman scattering signal, and receive by the 3rd photoelectric detecting parts 13.This is a passage 3.

At passage 2, passage 3 places,, make them carry out further inhibition respectively again to residual rice, Rayleigh scattering signal by designing the parameter of second Fiber Bragg Grating FBG 8 and the 3rd Fiber Bragg Grating FBG 10.

So far, when the carrying out to rice, Rayleigh scattering signal effectively separates and suppress, realized being used for two height quantum number rotational raman scattering spectral line extracted with high accuracy of thermometric.

Scheme 2

The main fibre optic grating coupler (FGC) of cascade that adopts is realized beam split.

Fig. 2 b is depicted as an embodiment, system comprises first fibre optic grating coupler 14, second fibre optic grating coupler 15 and the 3rd fibre optic grating coupler 16 of cascade, and first photoelectric detecting parts 11, second photoelectric detecting parts 12 and the 3rd photoelectric detecting parts 13 that receive reflected signal, design the Bragg wavelength X of each fibre optic grating coupler _b, set the λ of first fibre optic grating coupler 14 _bBe λ _B1=532.25nm sets the λ of second fibre optic grating coupler 15 _bBe λ _B2=530.6nm sets the λ of the 3rd fibre optic grating coupler 16 _bBe λ _B3=528.8nm, promptly respectively corresponding rice-Rayleigh scattering signal, low quantum number rotational raman scattering signal and high quantum number Raman scattering signal make each FBG have very high reflectivity and extremely low transmissivity respectively to above-mentioned wavelength selected by design.

The atmosphere echoed signal that contains a plurality of wavelength that telescope is received is coupled into multimode optical fiber (MMF), after multimode/single-mode fiber converter conversion, send into first fibre optic grating coupler 14 through single-mode fiber (SMF), or the atmosphere echoed signal that telescope receives is directly coupled to single-mode fiber (SMF), send into first fibre optic grating coupler, 14, the first fibre optic grating couplers 14 then wavelength is equaled λ _B1Rice-Rayleigh scattering signal reflect fully, after output port port2 output, receive by first photoelectric detecting parts 11.This is a passage 1.At passage 1 place, by designing the parameter of first fibre optic grating coupler 14, it is very faint to make transmission cross the rice of first fibre optic grating coupler 14-Rayleigh signal, has reached the very high outer inhibiting rate of band.

Because first fibre optic grating coupler 14 is to the light no reflection events effect of other wavelength, so after the transmittance of other wavelength crosses first fibre optic grating coupler 14, enters second fibre optic grating coupler, 15, the second fibre optic grating couplers 15 wavelength is equaled λ _B2The signal reflex of low quantum number rotational raman scattering and after its output port port3 output, receive by second photoelectric detecting parts 12.This is a passage 2.

In like manner, other wavelength are not λ _B2Light signal continue transmission and cross second fibre optic grating coupler 15 after, by 16 reflections of the 3rd fibre optic grating coupler, isolate wavelength and be respectively λ again _B3High quantum number Raman scattering signal.And by 13 receptions of the 3rd photoelectric detecting parts.This is a passage 3.

At passage 2, passage 3 places,, make them carry out further inhibition respectively again to residual rice, Rayleigh scattering signal by designing the parameter of second fibre optic grating coupler 15 and the 3rd fibre optic grating coupler 16.

So far, when the carrying out to rice, Rayleigh scattering signal effectively separates and suppress, realized being used for two height quantum number rotational raman scattering spectral line extracted with high accuracy of thermometric.

Scheme 3

The main dielectric multi-layer optical thin film wave filter (DTMF) that adopts is realized beam split.

Fig. 2 c is depicted as an embodiment, and system comprises dielectric multi-layer optical thin film wave filter 17 and first lens 18, second lens 19, the 3rd lens 20 and the 4th lens 21.Transmission peak wavelength in the dielectric multi-layer optical thin film wave filter 17 is designed to λ respectively ₁=532.25nm, λ ₂=530.6nm and λ ₃=528.8nm, respectively corresponding rice-Rayleigh scattering signal, low quantum number rotational raman scattering signal and high quantum number Raman scattering signal make DTMF have very high transmissivity and extremely low reflectivity respectively to above-mentioned wavelength selected by design.

The atmosphere echoed signal that contains a plurality of wavelength that telescope is received is coupled into multimode optical fiber (MMF), after multimode/single-mode fiber converter conversion, send into dielectric multi-layer optical thin film wave filter 17 through single-mode fiber (SMF) transmission and after by first lens, 18 post-concentrations, or after the atmosphere echoed signal that telescope receives is directly coupled to single-mode fiber (SMF) transmission, by sending into dielectric multi-layer optical thin film wave filter 17 behind first lens, 18 post-concentrations, after 17 pairs of corresponding wavelength of dielectric multi-layer optical thin film wave filter carry out selective transmission respectively, export at each output port port, the light signal of output transmission is respectively crossed second lens 19, behind the 3rd lens 20 and the 4th lens 21, respectively by first photoelectric detecting parts 11 of correspondence, second photoelectric detecting parts 12 and the 3rd photoelectric detecting parts 13 receive.Realized needed rice-Rayleigh scattering signal, low quantum number rotational raman scattering signal and high quantum number Raman scattering signal are carried out beam split and detection.

Scheme 4

The main employing based on the fibre optic grating coupler (M-ZI-FGC) of Mach-Zehnder interferometer (M-ZI) realized beam split.

Fig. 2 d is depicted as an embodiment, is made up of first fiber coupler 25, first fibre optic interferometer 22, second fiber coupler 26, the 3rd fiber coupler 27, second fibre optic interferometer 23, the 4th fiber coupler 28, the 5th fiber coupler 29, the 3rd fibre optic interferometer 24 and the six fibers coupling mechanism 30 of cascade.The Bragg wavelength X of the FBG in each optical fiber Mach-Zehnder interferometer wherein _bBe designed to λ respectively _B1=532.25nm, λ _B2=530.6nm and λ _B3=528.8nm, promptly respectively corresponding rice-Rayleigh scattering signal, low quantum number rotational raman scattering signal and high quantum number Raman scattering signal make each fibre optic interferometer have very high reflectivity and extremely low transmissivity respectively to above-mentioned wavelength selected by setting.

The atmosphere echoed signal that contains a plurality of wavelength that telescope is received is coupled into multimode optical fiber (MMF), by multimode/single-mode fiber converter conversion, behind single-mode fiber (SMF), be divided into two-beam by first fiber coupler 25 (FC1), or after the atmosphere echoed signal that telescope receives is directly coupled to single-mode fiber (SMF) transmission, be divided into two-beam by first fiber coupler 25, send into first fibre optic interferometer 22, in the two arms transmission of first fibre optic interferometer 22, the wavelength that satisfies the optical grating reflection condition equals λ respectively _B1Rice-Rayleigh scattering signal light reflect from two arms, during once more through first fiber coupler 25, the two-beam signal is interfered mutually and from output port port2 output, is received by first photoelectric detecting parts 11.This is a passage 1.The flashlight that does not satisfy the gratings strips part sees through fiber grating, when being transferred to second fiber coupler 26, interfering and exports from output port.The flashlight that so just will satisfy the grating wavelength condition separates with the flashlight of its commplementary wave length.

In like manner, all the other light signals by first fibre optic interferometer 22 continue to propagate, respectively through behind second fibre optic interferometer 23, the 3rd fibre optic interferometer 24, interferometer carries out demultiplexing to corresponding low quantum number and high quantum number Raman scattering signal, after output port port3, the port4 of each interferometer M-ZI output, by second photoelectric detecting parts 12 (this is a passage 2), the 3rd photoelectric detecting parts 13 (this is a passage 3) reception of correspondence.

So far, when the carrying out to rice, Rayleigh scattering signal effectively separates and suppress, realized being used for two height quantum number rotational raman scattering spectral line extracted with high accuracy of thermometric.

Scheme 5

Beam split is realized in the main optical fiber Fabry-Perot chamber (F-P Cavity) of adopting.

Fig. 2 e is depicted as an embodiment, is made up of first fiber resonance cavity 31, second fiber resonance cavity 32 and the 3rd fiber resonance cavity 33 of cascade.Wherein the wavelength X among each fiber resonance cavity Fabry-Perot Cavity is designed to λ respectively ₁=532.25nm, λ ₂=530.6nm and λ ₃=528.8nm, promptly respectively corresponding rice-Rayleigh scattering signal, low quantum number rotational raman scattering signal and high quantum number Raman scattering signal make each F-P Cavity have very high reflectivity and extremely low transmissivity respectively to above-mentioned wavelength selected by design.

The atmosphere echoed signal that contains a plurality of wavelength that telescope is received is coupled into multimode optical fiber (MMF), after multimode/single-mode fiber converter conversion, send into the input port port1 of first fiber optical circulator 5 through single-mode fiber (SMF), or the atmosphere echoed signal that telescope receives is directly coupled to single-mode fiber (SMF), send into the input port (port1) of first fiber optical circulator 5 then, be connected to the output port port2 output of first fiber resonance cavity 31 behind first fiber optical circulator 5, first fiber resonance cavity 31 equals wavelength to λ ₁Rice-Rayleigh scattering signal descend the road to output port port4 output fully, receive by first photoelectric detecting parts 11; This is a passage 1.

The light of other wavelength back that is reflected continues to propagate forward, after the output port port3 output of first fiber optical circulator 5, enters the input port port1 of second fiber optical circulator 7 again, and second fiber resonance cavity 32 equals wavelength to λ ₂Low quantum number rotate that the road is received by second photoelectric detecting parts 12 under the scattered signal after output port port4 output.This is a passage 2.

In like manner, can isolate wavelength is the high quantum number Raman scattering signal of λ 3, and is received by the 3rd photoelectric detecting parts 13.This is a passage 3.

So far, when the carrying out to rice, Rayleigh scattering signal effectively separates and suppress, realized being used for two height quantum number rotational raman scattering spectral line extracted with high accuracy of thermometric.

Computer system comprises multi-channel synchronous high-speed a/d capture card, computing machine, and for trying to achieve listed data inversion method of atmospheric temperature and parameters such as atmospheric aerosol extinction coefficient and aerosol optical depth and corresponding application software thereof.

Can detect the Raman scattering signal that obtains according to photoelectric detecting parts PMT2 and PMT3, obtain the intensity of surveying two signals obtaining and the strength ratio of two signals by the Raman scattering laser radar equation, utilize the radiosondage data that following formula is demarcated match, try to achieve the Temperature numerical of atmosphere.By utilizing the signal to noise ratio (S/N ratio) of the Raman scattering signal that sensitivity that temperature surveys and detection obtain, obtain the temperature detecting error of system then.

Also can detect the rice-Rayleigh scattering signal that obtains, press the Mie scattering laser radar equation, try to achieve the atmospheric aerosol optical property parameter through inverting according to photoelectric detecting parts PMT1.

The Nd:YAG pulsed laser sends the pulse laser beam that wavelength is 532.25nm, behind the collimating and beam expanding system collimator and extender, through the vertical directive atmosphere of a plurality of catoptrons, the rear orientation light that produces behind molecule in laser and the atmosphere and the particle interaction is received by the telescope receiving system, the laser radar atmosphere echoed signal that receives is coupled to multimode optical fiber, behind multimode/single-mode fiber converter, directly send into beam splitting system by single-mode fiber, or the laser radar atmosphere echoed signal that telescope receives is directly coupled to single-mode fiber, send into beam splitting system then, beam splitting system becomes various light signals with the beam split of atmospheric backscatter light, export from corresponding port port, receive by photoelectric detecting parts PMT, send into computer system again and carry out analyzing and processing.

Fig. 3 is the Bragg reflectivity and the atmospheric molecule N of optical fiber Bragg raster in the beam splitting system of the present invention ₂, O ₂Rotational raman spectrum concern synoptic diagram.

When the emitted laser bundle is propagated in atmosphere, with the N in the atmosphere ₂And O ₂Interact, produce Raman scattering.Because N ₂And O ₂The intensity distributions of pure rotational raman spectrum (PRRS) environment temperature is had dependence, consider simultaneously that atmospheric fluorescence props up pure rotational raman spectrum Stokes and have characteristics of interference, select to survey Anti-Stokes and prop up.Backscattering cross formula according to pure rotary Raman signal can calculate N ₂Molecule changes at the raman scattering cross section at different wave length place.

Consider that lower atmosphere layer variation of temperature scope is 200K-300K, so get line strength of temperature T=200K and T=300K.From figure as can be seen, N ₂The PRRS intensity distributions change with temperature T, raise with temperature near the Raman line intensity of emission optical maser wavelength and reduce, and raise with temperature away from the Raman lines intensity of the spectral line of emission.Promptly reduce, and raise corresponding to the rising of line strength of higher amount subnumber J with temperature corresponding to the rising of line strength of low quantum number J with temperature.Therefore, selected two intensity vary with temperature the quantum number J that is inverse variation ₁=6, J ₂=14, corresponding wavelength is respectively 530.6nm and 528.8nm, promptly is respectively the centre wavelength that the demodulation multiplexer of WDM is used for separating two Raman lines.When the design beam splitting system, for two Raman signals that guarantee to survey all have certain intensity, selected all kinds of light-splitting devices will guarantee certain bandwidth,

Because the low quantum number of the pure rotation Raman lines of atmosphere and the intensity of high quantum number spectral line can reduce respectively with the rising of temperature and strengthen, select the Raman signal of above-mentioned 2 centre wavelengths for use, and 2 measuring-signals are carried out difference processing, temperature survey susceptibility among the present invention become 2 channel temperature susceptibilitys and, thereby improved the whole thermometric sensitivity characteristic of system.

Fig. 4 is the transmission characteristics of the FBG1 of optical fiber Bragg raster in the beam splitting system of the present invention and the reflectivity Characteristics synoptic diagram of FBG2 and FBG3,, explains the principle of beam splitting system with scheme 1 herein.

Selecting the Bragg wavelength of FBG1 is λ _B1=532.25nm is mainly used in filtering rice and Rayleigh scattering signal.The spectral range of considering Rayleigh scattering signal is 3GHz, therefore selects FBG1 at λ _B1The full width at half maximum degree (FWHM) of reflectance spectrum be Δ λ _FWHM1=0.018nm, it is to λ _B1Reflectivity be R1 (λ _B1)=0.999, and transmitance only is T1 (λ _B1)=2.036 * 10 ^-4, shown in a among Fig. 4, then almost can all see through the Raman spectrum signal of other wavelength, also have also transmissive of residual part rice, Rayleigh signal certainly, but this moment the inhibiting rate of rice, Rayleigh signal is reached to 4 orders of magnitude.

Select the Bragg wavelength of FBG2, FBG3 to be respectively λ _B2=530.6nm and λ _B3=528.8nm is mainly used in the extracted amount subnumber and is respectively J ₁=6 and J ₂=14 Raman line, the full width at half maximum degree of their reflectance spectrums is respectively Δ λ _FWHM2=0.288nm, Δ λ _FWHM3=0.508nm, reflectivity are respectively R2 (λ _B2)=0.908, R3 (λ _B3)=0.945 is like this at λ _B2And λ _B3The place just can effectively extract Raman line respectively, shown in the b among Fig. 4.In addition, λ _B2, λ _B3At λ _B1The reflectivity at place is respectively R2 (λ _B1)=4.059 * 10 ^-4, R3 (λ _B1)=6.887 * 10 ^-4So they are to from λ _B1The remaining rice of place's transmission, Rayleigh signal can suppress respectively further, and its inhibiting rate has reached 3 orders of magnitude.So far, the WDM demodulation multiplexer of system of the present invention has reached 7 more than the order of magnitude to the inhibiting rate of rice, Rayleigh signal, has guaranteed height quantum number Raman line ground extracted with high accuracy.

Fig. 5 is the intensity distribution of atmosphere echoed signal after optical splitter filters, and, calculates atmosphere echoed signal intensity distributions after the beam split with scheme 1 and 2 herein.

Getting the sampling period during calculating is 300ns, and corresponding detection height resolving power is 45m.Suppose wavelength X by day _B2Near the radiant flux density of sun bias light is 3 * 108 Wm ^-2Sr ^-1Nm ^-1,, can estimate in wavelength X according to the systematic parameter of laser radar _B2And λ _B3Near the spectrum line, the sun bias light intensity that system detects is 3.251 * 10 ^-11W.Systematic parameter according to atmosphere Mie scattered signal model and radar, and consider that beam splitting system has the rejection rate of 7 orders of magnitude to the Mie-Rayleigh scattered signal, can calculate each scattered signal of entering radar system and sun background light intensity with surveying height profile by laser radar equation, its result as shown in Figure 5.

As seen from Figure 5, beam splitting system reaches 7 orders of magnitude to the rejection rate of Mie-Rayleigh scattered signal, guaranteed the system signal noise ratio that thermometric is required effectively, and the Raman signal of surveying below the 2.7km height than sun background light intensity, thereby can realize low latitude atmospheric temperature detecting on daytime.

According to residue Mie-Rayleigh flashlight subnumber and the photon number of sun bias light and the dark noise of detector in Raman scattering flashlight subnumber that receives separately in passage 1 and the passage 2 and the passage, the total signal to noise ratio snr of the system that calculates _Total(z) be shown in Fig. 6.Got Measuring Time 10 minutes.

Detecting temperature error in the cards when in addition, Fig. 6 has also provided day and night observation is with the height change curve.Under the situation of sun bias light influence, when requiring the detecting temperature error less than 1K, can survey the following atmospheric temperature of 3.3km and distribute by day, the detection at night highly then reaches 5km.The data inversion of measurement parameter

After the conversion of signals of A/D capture card, send into that computing machine writes down and analyzing and processing by the detected signal of each photoelectric detecting parts (PMT1-PMT3).For the measuring-signal that is obtained by PMT1, computing machine can be obtained optical parametrics such as Aerosol Extinction, backscattering coefficient by inverting Mie scattering laser radar equation.For the measuring-signal that is obtained by PMT2 and PMT3, computing machine can be obtained the height profile of atmospheric temperature by separating the rotational raman scattering laser radar equation.

Specifically, can obtain the vertical distribution and the atmospheric aerosol optical thickness of atmospheric temperature vertical distribution and atmospheric aerosol extinction coefficient by following various inverting.

We can calculate the power P (z) of each scattered signal that enters radar system according to following laser radar equation:

$P\left(z\right)=K\&CenterDot;E0\&CenterDot;\frac{c\&CenterDot;\mathrm{\&tau;}}{2}\&CenterDot;\frac{\mathrm{<figure-callout\; id="2"\; label="Ar\; z"\; filenames="C20071001840600251.png,C20071001840600271.png"\; state="\{\{state\}\}">Ar</figure-callout>}}{z^{}}\&CenterDot;Y\left(z\right)\&CenterDot;\mathrm{\&beta;}\left(z\right)\&CenterDot;\exp [-2\underset{0}{\overset{z}{\&Integral;}}\mathrm{\&alpha;}\left(z\right)\mathrm{dz}]---\left(1\right)$

Wherein, K is an optical system efficiency, E0 is a pulsed laser energy, τ is the laser pulse interval time, Ar is the telescope light-receiving area, and Y (z) is the light path overlap coefficient of transmission with receiver, and z is for surveying height, β (z) is the backscattering coefficient (being the function of atmosphere number density N (z) and scattering cross-section intensity σ) at height z place, and α (z) is the atmospheric extinction coefficient at height z place.In the equation, the parameter except atmospheric extinction coefficient α (z) and backscattering coefficient β (z) all is the known quantity that system provides.

A) inverting of atmospheric temperature

By 2 Raman scattering signal intensities that passage 2 and passage 3 detect, represent by following 2 laser radar equations respectively:

$P_2(T,z)=K\&CenterDot;E0\&CenterDot;\frac{c\&CenterDot;\mathrm{\&tau;}}{2}\&CenterDot;\frac{\mathrm{<figure-callout\; id="2"\; label="Ar\; z"\; filenames="C20071001840600251.png,C20071001840600271.png"\; state="\{\{state\}\}">Ar</figure-callout>}}{z^{}}\&CenterDot;Y\left(z\right)\&CenterDot;N\left(z\right)\&CenterDot;{\mathrm{\&sigma;}}_{b\_1}({\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="C20071001840600251.png,C20071001840600271.png"\; state="\{\{state\}\}">J</figure-callout>}}_1,T)\exp [-2\underset{0}{\overset{z}{\&Integral;}}\mathrm{\&alpha;}\left(z\right)\mathrm{dz}]---\left(2\right)$

$P_3(T,z)=K\&CenterDot;E0\&CenterDot;\frac{c\&CenterDot;\mathrm{\&tau;}}{2}\&CenterDot;\frac{\mathrm{<figure-callout\; id="2"\; label="Ar\; z"\; filenames="C20071001840600251.png,C20071001840600271.png"\; state="\{\{state\}\}">Ar</figure-callout>}}{z^{}}\&CenterDot;Y\left(z\right)\&CenterDot;N\left(z\right)\&CenterDot;{\mathrm{\&sigma;}}_{b\_2}({\mathrm{<figure-callout\; id="2"\; label="J"\; filenames="C20071001840600251.png,C20071001840600271.png"\; state="\{\{state\}\}">J</figure-callout>}}_2,T)\exp [-2\underset{0}{\overset{z}{\&Integral;}}\mathrm{\&alpha;}\left(z\right)\mathrm{dz}]---\left(3\right)$

Wherein, T is an atmospheric temperature, J ₁And J ₂Be respectively the rotational quantum number of the Raman scattering signal of two passages detections, σ _{B_1}(J ₁, T) and σ _{B_2}(J ₂, T) be temperature rotational quantum number J when being T respectively ₁The scattering cross-section intensity and the rotational quantum number J of rotational raman scattering signal ₂The scattering cross-section intensity of rotational raman scattering signal, and J ₁And J ₂For known.

Then by (2) formula and (3) formula ratio, obtain passage 1 and passage 2 scattered signal strength ratio H (T z) is:

$H(T,z)=\frac{P_2(T,z)}{P_3(T,z)}=\frac{{\mathrm{\&sigma;}}_{b\_1}\left(T\right)}{{\mathrm{\&sigma;}}_{b\_2}\left(T\right)}---\left(4\right)$

Warp is to theoretic σ _{B_1}(J ₁, T) and σ _{B_2}(J ₂, T) find the solution, and carry out curve fitting, can obtain following relationship:

$H(T,z)=\frac{P_2(T,z)}{P_3(T,z)}\&ap;\exp \{-[\frac{A}{T^2\left(z\right)}+\frac{B}{T\left(z\right)}+C\left]\right\}---\left(5\right)$

In the formula, z is for surveying height, and A, B, C are constant.Utilize the radiosondage data that radar system is just demarcated and to simulate constant A, B, C.Therefore, the atmospheric temperature T (z) at height z place is

$T\left(z\right)=-\frac{-2A}{B\&PlusMinus;\sqrt{B^2-4A({\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="C20071001840600251.png,C20071001840600271.png"\; state="\{\{state\}\}">C</figure-callout>}}^2+\ln R(T,z))}}---\left(6\right)$

B) aerosol optical characteristics

Rice-Rayleigh scattering signal intensity the P that detects by passage 1 ₁(z), represent by following laser radar equation:

$P_1\left(z\right)=K\&CenterDot;E0\&CenterDot;\frac{c\&CenterDot;\mathrm{\&tau;}}{2}\&CenterDot;\frac{\mathrm{<figure-callout\; id="2"\; label="Ar\; z"\; filenames="C20071001840600251.png,C20071001840600271.png"\; state="\{\{state\}\}">Ar</figure-callout>}}{z^{}}\&CenterDot;Y\left(z\right)\&CenterDot;\mathrm{\&beta;}\left(z\right)\&CenterDot;\exp [-2\underset{0}{\overset{z}{\&Integral;}}\mathrm{\&alpha;}\left(z\right)\mathrm{dz}]---\left(7\right)$

In the formula, β (z)=β _m(z)+β _a(z), α (z)=α _m(z)+α _a(z),

And β _m(z) and β _a(z) be respectively the backscattering coefficient of atmospheric molecule and particulate, α _m(z) and α _a(z) be respectively the extinction coefficient of atmospheric molecule and particulate.

If the square distance correction function of laser radar echo signal is:

X(z)＝P(z)·z ² (8)

If the prior total extinction coefficient α (z of known a certain height Zc place atmosphere _c) or backscattering coefficient β (z _c), Z then _cSentence down the particulate extinction coefficient α on each height _a(z) or backscattering coefficient β _a(z) be respectively:

${\mathrm{\&alpha;}}_a\left(z\right)=\frac{X\left(z\right)}{\frac{X\left(z_c\right)}{\mathrm{\&alpha;}\left(z_c\right)}+2{\&Integral;}_z^{z_c}X\left(z^{\&prime;}\right)d{z}^{\&prime;}}-{\mathrm{\&alpha;}}_m\left(z\right)---\left(9\right)$

${\mathrm{\&beta;}}_a\left(z\right)=\frac{X\left(z\right)}{\frac{X\left(z_c\right)}{\mathrm{\&beta;}\left(z_c\right)}+2S{\&Integral;}_z^{z_c}X\left(z^{\&prime;}\right)d{z}^{\&prime;}}-{\mathrm{\&beta;}}_m\left(z\right)---\left(10\right)$

In the formula, α _m(z) and β _m(z) be respectively the extinction coefficient and the backscattering coefficient of atmospheric molecule, S is the laser radar ratio, S=α _a/ β _a, its value is relevant with different aerocolloidal optical characteristics, is a constant.

In last two formulas, the extinction coefficient α of the atmospheric molecule at height z place _m(z) or backscattering coefficient β _m(z) can obtain by the United States standard atmosphere model, if measuring height is higher, can choose one section and be close to the clean atmosphere layer that does not contain particulate, in this section altitude range, laser radar range correction logarithm echoed signal is carried out least square fitting, half of this regression curve slope is the atmospheric molecule extinction coefficient, obtains the extinction coefficient height profile model of atmospheric molecule, and this obtaining value method suits atmospheric condition at that time more.When measuring height is higher, can chooses to be close to and do not contain the clean atmosphere layer place height of particulate as Z _c, boundary value α (z then _c) or β (z _x) in just only contain the composition of atmospheric molecule; Equally, if measuring height is not high enough, can choose one section atmospheric envelope comparatively uniformly, this altitude range inner laser distance by radar be proofreaied and correct the logarithm echoed signal carry out least square fitting, half of regression curve slope is height z _cThe atmospheric extinction coefficient at place or the boundary value α (z of backscattering coefficient _x) or β (z _c).

Claims (6)

1. based on the all-fiber Raman scattering laser radar system of the demultiplexer beam split of WDM technology, it is characterized in that this system comprises

Laser transmitting system, Nd:YAG pulsed laser, the paired pulses laser that comprises emission pulse laser collimate and expand the beam expander of bundle, also comprise a plurality of catoptrons, and the setting of a plurality of catoptrons makes the laser vertical directive atmosphere behind the collimator and extender;

Receiving system is used for receiving the rear orientation light that produces behind the molecule of laser and atmosphere and the particle interaction, and the laser radar atmosphere echoed signal that receives is coupled to multimode optical fiber;

Multimode/single-mode fiber converter is used for converting multimode atmosphere echoed signal to the single-mode fiber signal, and sends into through single-mode fiber, or the laser radar atmosphere echoed signal that receiving system receives is directly coupled to single-mode fiber;

Beam splitting system be used for the rotary Raman spectral line of echoed signal is separated with rice-Rayleigh scattering spectral line, and each scattered signal after will separating is exported from corresponding ports;

Photoelectric detecting parts is used for that each scattered light signal after separating is become electric signal and receives;

Computer system, be pre-loaded into meteorological and atmospheric environmental parameters inversion algorithm program, be used for the scattering spectral line signal that receives is carried out analyzing and processing, obtain the atmospheric temperature meteorologic parameter, and atmospheric aerosol extinction coefficient and scattering coefficient, aerosol optical depth, atmospheric visibility atmospheric environmental parameters value.

2. according to the described laser radar system of claim 1, it is characterized in that described beam splitting system comprises,

First fiber optical circulator (5), be used to receive the echoed signal of a plurality of wavelength that single-mode fiber sends into, and this echoed signal outputed to first Fiber Bragg Grating FBG, with the rice-Rayleigh scattering signal that receives the first Fiber Bragg Grating FBG reflected back, and should output to first photoelectric detecting parts (11) by rice-Rayleigh scattering signal;

First Fiber Bragg Grating FBG (6) is set its wavelength X _bBe λ _B1=532.25nm is used for wavelength is equaled λ _B1Rice-Rayleigh scattering signal reflected back first fiber optical circulator (5) almost completely, and allow the light signal transmission of other wavelength pass through;

Second fiber optical circulator (7), be used to receive the signal that the first Fiber Bragg Grating FBG transmission is passed through, and this signal outputed to second Fiber Bragg Grating FBG, rotate scattered signal with the low quantum number that receives the second Fiber Bragg Grating FBG reflected back, and should rotate scattered signal and output to second photoelectric detecting parts (12);

Second Fiber Bragg Grating FBG (8) designs its wavelength X _bBe λ _B2=530.6nm is used for wavelength is equaled λ _B2Low quantum number rotate almost completely reflected back second fiber optical circulator of scattered signal, allow the light signal transmission of other wavelength pass through;

The 3rd fiber optical circulator (9), be used to receive the signal that the second Fiber Bragg Grating FBG transmission is passed through, and this signal outputed to the 3rd Fiber Bragg Grating FBG, with the high quantum number Raman scattering signal that receives the 3rd Fiber Bragg Grating FBG reflected back, and this scattered signal outputed to the 3rd photoelectric detecting parts (13);

The 3rd Fiber Bragg Grating FBG (10) designs its wavelength X _bBe λ _B3=528.8nm is used for wavelength is equaled λ _B3High quantum number Raman scattering signal reflected back the 3rd fiber optical circulator almost completely, allow the light signal transmission of other wavelength pass through.

3. according to the described laser radar system of claim 1, it is characterized in that described beam splitting system comprises,

First fibre optic grating coupler (14) is set its wavelength X _bBe λ _B1=532.25nm is used to receive the echoed signal of a plurality of wavelength that single-mode fiber sends into, and wavelength is equaled λ _B1The reflection of rice-Rayleigh scattering signal, and the rice-Rayleigh scattering signal that will reflect is sent into first photoelectric detecting parts (11);

Second fibre optic grating coupler (15) is set its wavelength X _bBe λ _B2=530.6nm is used to receive the light signal that first fibre optic grating coupler (14) are crossed in transmission, and wavelength is equaled λ _B2The signal reflex of low quantum number rotational raman scattering, and the low quantum number rotational raman scattering signal that will reflect is sent into second photoelectric detecting parts (12);

The 3rd fibre optic grating coupler (16) is set its wavelength X _bBe λ _B3=528.8nm is used to receive the light signal that second fibre optic grating coupler (15) are crossed in transmission, and wavelength is equaled λ _B3High quantum number Raman scattering signal reflex, and with the reflection high quantum number Raman scattering signal send into the 3rd photoelectric detecting parts (13).

4. according to the described laser radar system of claim 1, it is characterized in that described beam splitting system comprises,

One dielectric multi-layer optical thin film wave filter (17) is set its transmission peak wavelength and is respectively λ ₁=532.25nm, λ ₂=530.6nm and λ ₃=528.8nm is used to receive the echoed signal of a plurality of wavelength that single-mode fiber sends into, and respectively wavelength is equaled λ ₁Rice-Rayleigh scattering signal, wavelength equal λ ₂Low quantum number rotational raman scattering signal and wavelength equal λ ₃The transmission of high quantum number Raman scattering signal, and the signal of transmission sent into first photoelectric detecting parts (11), second photoelectric detecting parts (12) and the 3rd photoelectric detecting parts (13) respectively;

The front of described dielectric multi-layer optical thin film wave filter (17) also is provided with first lens (18), the back of dielectric multi-layer optical thin film wave filter (17) is provided with second lens (19), the 3rd lens (20) and the 4th lens (21), after making each light signal of reflection three lens being crossed in transmission respectively, enter photoelectricity inspection exploring block again.

5. according to the described laser radar system of claim 1, it is characterized in that, described beam splitting system,

First fiber coupler (25), first fibre optic interferometer (22), second fiber coupler (26), the 3rd fiber coupler (27), second fibre optic interferometer (23), the 4th fiber coupler (28), the 5th fiber coupler (29), the 3rd fibre optic interferometer (24) and the six fibers coupling mechanism (30) that comprise cascade

First fiber coupler (25) is used for that single-mode fiber is sent into echoed signal and is divided into two-beam, and the wavelength that two arms transmit and reception reflects from first fibre optic interferometer (22) at first fibre optic interferometer (22) equals λ respectively ₁Rice-Rayleigh scattering signal of=532.25nm is also interfered mutually and is exported, and is received by first photoelectric detecting parts (11);

First fibre optic interferometer (22), setting its wavelength X is λ ₁=532.25nm is used for wavelength is equaled λ ₁Rice-Rayleigh scattering signal reflected back optical fiber coupling mechanism (25) almost completely, and allow the light signal transmission of other wavelength pass through;

Second fiber coupler (26) is used to receive first fibre optic interferometer (22) transmission by not satisfying the signal of optical grating reflection condition, and interferes and from outputing to the 3rd fiber coupler (27);

The 3rd fiber coupler (27) is used for the echoed signal that second fiber coupler (26) is sent into is divided into two-beam, and the wavelength that two arms transmit and reception reflects from second fibre optic interferometer (23) at second fibre optic interferometer (23) equals λ respectively ₂The low quantum number rotational raman scattering signal of=530.6nm is also interfered mutually and is exported, and is received by second photoelectric detecting parts (12);

Second fibre optic interferometer (23), setting its wavelength X is λ ₂=530.6nm is used for wavelength is equaled λ ₂Low quantum number rotational raman scattering signal reflected back optical fiber coupling mechanism (27) almost completely, and allow the light signal transmission of other wavelength pass through;

The 4th fiber coupler (28) is used to receive second fibre optic interferometer (23) transmission by not satisfying the signal of optical grating reflection condition, and interferes and from outputing to the 5th fiber coupler (29);

The 5th fiber coupler (29) is used for the echoed signal that the 4th fiber coupler (28) is sent into is divided into two-beam, and the wavelength that two arms transmit and reception reflects from the 3rd fibre optic interferometer (24) at the 3rd fibre optic interferometer (24) equals λ respectively ₃The high quantum number rotational raman scattering signal of=528.8nm is also interfered mutually and is exported, and is received by the 3rd photoelectric detecting parts (13);

The 3rd fibre optic interferometer (24), setting its wavelength X is λ ₂=528.8nm is used for wavelength is equaled λ ₃High quantum number rotational raman scattering signal reflected back optical fiber coupling mechanism (29) almost completely.

6. according to the described laser radar system of claim 1, it is characterized in that described beam splitting system comprises,

First fiber optical circulator (5), be used to receive the echoed signal of a plurality of wavelength that single-mode fiber sends into, and this echoed signal outputed to first fiber resonance cavity (31), with the scattered signal that receives first fiber resonance cavity (31) reflected back, and this scattered signal outputed to second fiber optical circulator (7);

First fiber resonance cavity (31), setting its wavelength X is λ ₁=532.25nm is used for wavelength is equaled λ ₁Rice-Rayleigh scattering signal under the road, output to first photoelectric detecting parts (11), allow the light signal of other wavelength launch back first fiber optical circulator (5);

Second fiber optical circulator (7), be used to receive the light signal of first fiber optical circulator (5) output, and this echoed signal outputed to second fiber resonance cavity (32), with the scattered signal that receives second fiber resonance cavity (32) reflected back, and this scattered signal outputed to the 3rd fiber optical circulator (9);

Second fiber resonance cavity (32), setting its wavelength X is λ ₂=530.6nm is used for wavelength is equaled λ ₂Low quantum number rotational raman scattering signal under the road, output to second photoelectric detecting parts (12), allow the light signal of other wavelength launch back second fiber optical circulator (7);

The 3rd fiber optical circulator (9), be used to receive the light signal of second fiber optical circulator (7) output, and this echoed signal outputed to the 3rd fiber resonance cavity (33) and receive the scattered signal of the 3rd fiber resonance cavity (33) reflected back, and with this scattered signal output;

The 3rd fiber resonance cavity (33), setting its wavelength X is λ ₃=528.8nm is used for wavelength is equaled λ ₃High quantum number Raman scattering signal under the road, output to the 3rd photoelectric detecting parts (13), allow the light signal of other wavelength launch back the 3rd fiber optical circulator (9).

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