CN103713293A - All-fiber Doppler lidar wind field detection system and method - Google Patents

Abstract

An all-fiber Doppler lidar wind field detection system comprises a laser emission system, an optical receiving system, a frequency discrimination and optical detection system and a signal processing system, wherein the frequency discrimination and optical detection system is connected with the signal processing system; the laser emission system and the optical receiving system are connected with the frequency discrimination and optical detection system through multi-mode/single-mode converters; the laser emission system emits laser light into the atmosphere; the optical receiving system receives backscattering light of atmospheric molecules and couples the backscattering light into multimode fibers, then, the backscattering light is fed into the signal processing system after entering the frequency discrimination and optical detection system for processing through the multi-mode/single-mode converters, and wind speed information is obtained after the backscattering light is processed. A fiber M-Z interferometer is used as a frequency detector, the wavelength range is wide, the selectivity of a laser light source is high, the ability to resist external interference is high, and spectral resolution and light splitting efficiency are high; in this way, the stability of detection is improved, detection accuracy is high, and the all-fiber Doppler lidar wind field detection system is convenient to use.

Description

Full optical fiber Doppler lidar wind field detection system and detection method

Technical field

The invention belongs to wind field detection system technical field, relate to a kind of full optical fiber Doppler lidar wind field detection system, also relate to the method for utilizing this system to survey.

Background technology

Wind field is important meteorologic parameter and atmospheric dynamics parameter, with the close relationship that has of climate change and various extreme climate phenomenons, the research of the meticulous wind field Detection Techniques of high space-time large scale is one of the important research target of laser radar remote sensing and cutting edge technology always.

Laser radar, as the new technical means with high-spatial and temporal resolution and clear sky detection wind field, is just being subject to concern widely and the fund input of countries in the world.The countries such as U.S. NASA and the ESA of European Space Agency have researched and developed ground, airborne and satellite-bone laser radar survey wind technology in succession, Chinese Academy of Sciences's Anhui ray machine of China in one's power unit such as Chinese Marine University is also carried out fruitful research, successively develop the Doppler wind-measuring laser radar system of different wave length, and for preliminary day to day operation and scientific research observational study.Spaceborne anemometry laser radar is for the research of global dimensional wind data snooping, the developed countries such as USA and Europe have started the project verification beforehand research work in early stage, also there are various spatial emission plans, as ESA is planning the ALADIN/ADM-Aeolus plan of surveying for global wind field in first of transmitting in 2015, Japan plans to combine in 2015 transmitting for atmospheric aerosol with Europe, the ATLID/EarthCARE plan of the high spectral resolution satellite-bone laser radar of the meticulous detection such as cloud, these plans will drop into actual transmission operation in a few years from now on, will produce far-reaching influence to Global climate change and disaster prewarning and forecasting etc.

At present, the principle that laser radar is surveyed for atmospheric wind is the Doppler shift based on atmospheric molecule and suspended particulate substance, and by the mode of frequency coherence detection and direct frequency discrimination is realized to Doppler shift frequency discrimination, inverting obtains atmosphere wind speed.Directly frequency discrimination measurement Doppler shift (noncoherent detection) method mainly comprises edge detecting technology and fringe technique.Normal high-resolution Fabry-Perot (F-P) etalon, the Mach-Zehnder(M-Z of adopting of rim detection) interferometer, Michelson interferometer, grating etc. or utilize various molecules, Atomic filter, as iodine filter, sodium, potassium, silver-colored steam wave filter etc. are as frequency discriminator, Doppler shift is measured in the variation that the variation of frequency signal is converted into relative energy signal, and it measures the filtering characteristic that sensitivity mainly depends on edge detection filter; Stripe pattern technology is the striped imaging that utilizes multi channel detector to become interferometer, when there is Doppler shift, the energy of fringe distribution on each passage changes, and striped center of gravity is moved, can Wind Speed Inversion by measuring relatively moving of striped center of gravity.With respect to F-P interferometer frequency discrimination, M-Z interferometer is as frequency discriminator, have that transmitance is high, the wide ranges of surveying spectrum, can carry out field widening and obtain large luminous flux, and become vertical bar line can mutually mate with detector etc. advantage, for Doppler anemometry laser radar, can obtain when large wind field investigative range of higher detection noise.Yet the shortcomings such as volume is large, light path adjustment is complicated, structure is not compact, be subject to environmental interference, system stability is poor that traditional physical construction formula M-Z interferometer often has, restrict its application and development, particularly the application in airborne and onboard system.

In recent years, along with the develop rapidly of optical fiber sensing technology, the technology such as the optical fiber filter based on optical fiber technology, fibre optic interferometer reach its maturity.The all-fiber coherent anemometry laser radar of the minitype airborne 1.5um-2.0um wavelength of MIT's research and development, utilizes fiber laser and coherent fiber technology to survey wind field, and research has approached commercialization, can be commercial passenger aircraft and surveys Cloudless atmosphere wind field and turbulent flow.

Summary of the invention

The object of the invention is to propose a kind of full optical fiber Doppler lidar wind field detection system, the mechanism that solves prior art existence is huge, complex structure, and the unsettled problem of result of detection.

Second object of the present invention is to provide a kind of method of utilizing above-mentioned detection system to survey.

Technical scheme of the present invention is, a kind of full optical fiber Doppler lidar wind field detection system, comprise laser transmitting system, optical receiving system, frequency discrimination and optical detection system and signal processing system, frequency discrimination and optical detection system are connected with signal processing system, and laser transmitting system is connected with frequency discrimination and optical detection system by multimode/single mode converter with optical receiving system; Laser transmitting system Emission Lasers enters atmosphere, optical receiving system receives the rear orientation light of atmospheric molecule, and is coupled into multimode optical fiber, then after multimode/single mode converter enters frequency discrimination and optical detection system processing, send into signal processing system, the treated wind speed information that obtains.

Feature of the present invention is also:

Before laser transmitting system, be provided with beam splitter, catoptron and scanning mirror, laser arrives scanning mirror by beam splitter, catoptron, by scanning mirror, is reflected and is entered atmosphere, and optical receiving system receives the rear orientation light of atmospheric molecule by scanning mirror.

Frequency discrimination and optical detection system comprise optical fiber M-Z interferometer and photodetector, and optical fiber M-Z interferometer is by two fiber coupler C ₁, C ₂with two fiber optic interferometric arm L ₁, L ₂form; Light signal, from the input of optical fiber M-Z interferometer input end, is exported by optical fiber M-Z interferometer output port; The light signal of output has two-way route of transmission, and a road is through fiber coupler C ₁straight-through arm, fiber optic interferometric arm L ₁with fiber coupler C ₂straight-through arm, another road is through fiber coupler C ₁transposition arm, fiber optic interferometric arm L ₂with fiber coupler C ₂transposition arm, two paths of signals is interfered mutually at output port, by photodetector, is received.

Optical fiber M-Z interferometer comprises input end 1 and 2, and optical fiber M-Z interferometer comprises output port 3 and 4; The signal of output port 3 outputs is received by photodetector PMT1, and the signal of output port 4 outputs is received by photodetector PMT2.

Utilize the detection method of above-mentioned detection system, the stable seed of laser transmitting system proportion injects ND:YAG pulsed laser, through two frequency-doubling crystal shoot lasers, light beam arrives scanning mirror through collimating and beam expanding system, beam splitter, catoptron, by scanning mirror, reflect and enter atmosphere, echoed signal receives by optical receiving system, then by scatter echo signal coupling in multimode optical fiber, process multimode/single mode converter and collimated enter the input end of optical fiber M-Z interferometer, 3dB photo-coupler C again ₁light is divided into the two-beam that intensity is equal, through thering are two arm transmission of optical path difference, then through three-dB coupler C ₂after interference, from two-port 3 and 4, export, then send into signal processing system after being received by detector, carry out data acquisition and Inversion Calculation, obtain wind speed size information, wind speed direction is determined by optical beam scanning system.

Optical fiber M-Z interferometer output port 3 and 4 transmitance are derived and are drawn by coupled mode theory, and when not considering insertion loss, the relation of input light field and output light field can be expressed as:

In formula, E ₁, E ₂respectively the input light field of port one and 2, E ₃, E ₄respectively the output light field of port 3 and 4, k ₁, k ₂respectively fiber coupler C ₁, C ₂coupling coefficient,

n is optical fiber effective refractive index, and l is the arm length difference of interferometer two arms, and σ is incident light wave wave number.By formula (1), can be obtained:

If input signal E ₁=1, E ₂=0, and coupling fiber coefficient k ₁=k ₂=0.5, have:

Therefore the transmitance of two output ports of optical fiber M-Z interferometer is respectively:

The intensity distributions of incident spectrum is I (σ), and form is

$I\left({\mathrm{\σ}}^{\′}\right)=\frac{1}{r\sqrt{\mathrm{\π}}}\exp [-\frac{{({\mathrm{\σ}}^{\′}-\mathrm{\σ})}^2}{{\mathrm{\γ}}^2}]---\left(5\right)$

Wherein

k is Boltzmann constant, and c is the light velocity, and T is atmospheric temperature, the average quality that m is atmospheric molecule.The signal that detector receives is the convolution of incident light spectrum and transmitance, is respectively:

$S_1\left(\mathrm{\σ}\right)=\mathrm{sI}\left(\mathrm{\σ}\right)\⊗T_1\left(\mathrm{\σ}\right),S_2\left(\mathrm{\σ}\right)=\mathrm{sI}\left(\mathrm{\σ}\right)\⊗T_2\left(\mathrm{\σ}\right)---\left(6\right)$

The responsiveness that wherein s is detector, is made as 1, and convolution can obtain:

$\begin{array}{c}{S}_1=\frac{1}{\mathrm{\γ}\sqrt{\mathrm{\π}}}\exp (-\frac{{\mathrm{\σ}}^2}{{\mathrm{\γ}}^2})\⊗{\sin }^2\frac{\mathrm{n\π\σ}}{\mathrm{\δ}}=\frac{1}{2}[1-\exp (-\frac{{\mathrm{\π}}^2{\mathrm{\γ}}^2}{{\mathrm{\δ}}^2})\cos \frac{2\mathrm{n\π\σ}}{\mathrm{\δ}}]\\ S_2=\frac{1}{\mathrm{\γ}\sqrt{\mathrm{\π}}}\exp (-\frac{{\mathrm{\σ}}^2}{{\mathrm{\γ}}^2})\⊗{\cos }^2\frac{\mathrm{n\π\σ}}{\mathrm{\δ}}=\frac{1}{2}[1+\exp (-\frac{{\mathrm{\π}}^2{\mathrm{\γ}}^2}{{\mathrm{\δ}}^2})\cos \frac{2\mathrm{n\π\σ}}{\mathrm{\δ}}]\end{array}---(7)$

Wherein δ is that optical path difference is reciprocal.Calculate differential signal

$Q=\frac{S_1-S_2}{S_1+S_2}=-\exp (-\frac{{\mathrm{\π}}^2{\mathrm{\γ}}^2}{{\mathrm{\δ}}^2})\cos \frac{2\mathrm{n\π\σ}}{\mathrm{\δ}}---\left(8\right)$

According to Doppler shift principle, the relation of wind speed u and atmospheric backscatter light wave number

$\mathrm{\σ}={\mathrm{\σ}}_0(1+\frac{2u}{c})---\left(9\right)$

The pass that can obtain Q and wind speed after optimization is

$Q\left(u\right)=-\exp (-\frac{{\mathrm{\π}}^2{\mathrm{\γ}}^2}{{\mathrm{\δ}}^2})\cos \left[2\mathrm{n\π}\frac{{\mathrm{\σ}}_0}{\mathrm{\δ}}(1+\frac{2u}{c})\right]---\left(10\right)$

Formula can be finally inversed by air speed value thus.

Optimum optical path difference is:

$l_{\mathrm{opt}}=\frac{c}{2\mathrm{n\π}{\mathrm{\σ}}_0}{\left(\frac{m}{{\mathrm{kT}}_0}\right)}^{1/2}$

。

The present invention has following beneficial effect:

1, the present invention adopts optical fiber M-Z interferometer as frequency discriminator, has wider wavelength coverage, and the selectivity of LASER Light Source is large, and anti-external interference ability is strong, and has higher spectral resolution and spectroscopical effeciency; Insensitive to incident beam field angle; Optical energy loss is minimum, and transmitance is high, and luminous flux is large; Improved the stability of surveying.

2, wind field detection system of the present invention has softness, and shape such as can arbitrarily change at the feature, and applicable to various inflammable and explosive or rugged surroundings that radiation is strong, compact conformation, lightweight simultaneously, and system performance is stable.

3, detection method detection accuracy of the present invention is high, easy to use.

Accompanying drawing explanation

Fig. 1 is the full optical fiber Doppler lidar of the present invention wind field detection system structural representation;

Fig. 2 is the Fiber Mach-Zehnder Interferometer frequency discrimination system architecture schematic diagram of the full optical fiber Doppler lidar of the present invention wind field detection system.

Fig. 3 is normalized signal intensity curve and the spectral distribution curve figure of the Fiber Mach-Zehnder Interferometer frequency discrimination system of the full optical fiber Doppler lidar of the present invention wind field detection system.

In figure, 1. laser transmitting system, 2. optical receiving system, 3. frequency discrimination and Photodetection system, 4. signal processing system.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

A kind of full optical fiber Doppler lidar wind field detection system, referring to Fig. 1, comprise laser transmitting system 1, optical receiving system 2, frequency discrimination and optical detection system 3 and signal processing system 4, frequency discrimination and optical detection system 3 are connected with signal processing system 4, and laser transmitting system 1 is connected with frequency discrimination and optical detection system 3 by multimode/single mode converter with optical receiving system 2; Laser transmitting system 1 Emission Lasers enters atmosphere, optical receiving system 2 receives the rear orientation light of atmospheric molecule, and is coupled into multimode optical fiber, then after multimode/single mode converter enters frequency discrimination and optical detection system 3 processing, send into signal processing system 4, the treated wind speed information that obtains.

Before laser transmitting system 1, be provided with beam splitter, catoptron and scanning mirror, laser arrives scanning mirror by beam splitter, catoptron, by scanning mirror, is reflected and is entered atmosphere, and optical receiving system 2 receives the rear orientation light of atmospheric molecule by scanning mirror.Catoptron comprises catoptron 1, catoptron 2 and catoptron 3, and catoptron 2 is oppositely arranged with catoptron 1 and catoptron 3, and laser arrives catoptron 1 by beam splitter, through catoptron 2, arrives catoptron 3, through catoptron 3, arrives scanning mirror.

Optical receiving system 2 comprises Cassegrain telescope.

Frequency discrimination and optical detection system 3 comprise optical fiber M-Z interferometer and photodetector; Optical fiber M-Z interferometer is by two fiber coupler C ₁, C ₂with two fiber optic interferometric arm L ₁, L ₂form; Optical signals optical fiber M-Z interferometer input end 1 or 2 inputs, by optical fiber M-Z interferometer output port 3 and 4 outputs; The light signal of output port 3 outputs has two-way route of transmission, and a road is through fiber coupler C ₁straight-through arm, fiber optic interferometric arm L ₁with fiber coupler C ₂straight-through arm, another road is through fiber coupler C ₁transposition arm, fiber optic interferometric arm L ₂with fiber coupler C ₂transposition arm, two paths of signals is interfered mutually at output port 3, by photodetector, PMT1 receives.Similarly, by photodetector, PMT2 receives the output signal of output port 4.

In laser transmitting system 1, Emission Lasers is through the light splitting of collimator and extender process beam splitter, sub-fraction light beam directly enters frequency discrimination system through coupling fiber, this signal not only can be used as the reference signal of surveying wind, and can also control seed laser frequency locking and the optical path difference that regulates interferometer through data processing and algorithm.Data acquisition adopts PCI-9826 data collecting card, 4 passages, sampling rate 20M, 16 ADC, meet the requirement that anemometry laser radar system data is processed, adopted industrial computer processing signals, not only realized the processing of data, the preservation of data, can also be through the frequency of some Processing Algorithm monitoring seed lasers locking shoot lasers, but also 3-D scanning that can software control system, with the fine setting of axial adjustment and interferometer optical path difference etc.

The effect of optical fiber M-Z interferometer frequency discrimination system is that the Received Signal receiving according to telescope calculates echoed signal with respect to the Doppler shift of reference light through the variation of interferometer output light intensity, thereby Wind Speed Inversion is big or small.

Optical fiber M-Z interferometer frequency discrimination and detection system are referring to Fig. 2, and optical fiber adopts the single-mode fiber of 532nm, two fiber coupler C ₁and C ₂splitting ratio be 1:1, two arm optical path differences are 3.3cm, detector adopts photomultiplier PMT.Fig. 3 is the transmittance curve of optical fiber M-Z interferometer frequency discrimination system, laser pulse, is reference light frequency ν ₀frequency locking is to S ₁=S ₂on position.When echoed signal has a Doppler shift with respect to reference light, the transmitance S of interferometer ₁and S ₂can change, the energy that detector PMT surveys also correspondingly changes, can inverting Doppler shift and wind speed according to this variation.

Set incident central wavelength lambda=532.25nm, reference temperature T ₀=250K, optical fiber effective refractive index n=1.46, can obtain l _oPT=3.3cm.Figure 3 shows that two channel normalization signal intensity S under optimum optical path difference ₁and S ₂with the variation of wave number, I ₁(σ) while being wavelength X=532.25nm, spectrum distributes, the corresponding S in visible spectrum center in figure ₁=S ₂, when receiving the relative Emission Lasers of rear orientation light, have certain displacement, as I in Fig. 3 ₂(σ) shown in, the corresponding S of center wave number now ₁', S ₂', by S ₁', S ₂' can be finally inversed by wind speed size in substitution formula (8) and (10).

Concrete detection method is as follows:

The stable seed of laser transmitting system 1 proportion injects Nd:YAG pulsed laser, the laser that is 532nm through two frequency-doubling crystal outgoing wavelength, light beam is through collimating and beam expanding system, beam splitter 5, catoptron 6 arrive scanning mirror 7, by scanning mirror 7 refractions, enter atmosphere, echoed signal adopts Cassegrain telescope to receive, telescope receives atmospheric backscatter echoed signal and is coupled in multimode optical fiber, process multimode/single mode converter and collimated enter the input end of optical fiber M-Z interferometer, 3dB photo-coupler C again ₁light is divided into the two-beam that intensity is equal, through thering are two arm transmission of certain optical path difference, then through three-dB coupler C ₂after interference, from two-port (3 and 4), export, then send into signal processing system after being received by detector (photomultiplier PMT1 and PMT2), carry out data acquisition and Inversion Calculation, obtain wind speed size information, wind speed direction is determined by optical beam scanning system.

Optical fiber M-Z interferometer output port 3 and 4 transmitance are derived and are drawn by coupled mode theory, and when not considering insertion loss, the relation of input light field and output light field can be expressed as:

In formula, E ₁, E ₂respectively the input light field of port one and 2, E ₃, E ₄respectively the output light field of port 3 and 4, k ₁, k ₂respectively fiber coupler C ₁, C ₂coupling coefficient,

n is optical fiber effective refractive index, and l is the arm length difference of interferometer two arms, and σ is incident light wave wave number.By formula (1), can be obtained:

If input signal E ₁=1, E ₂=0, and coupling fiber coefficient k ₁=k ₂=0.5, have:

Therefore the transmitance of two output ports of optical fiber M-Z interferometer is respectively:

The intensity distributions of incident spectrum is I (σ), and form is

$I\left({\mathrm{\σ}}^{\′}\right)=\frac{1}{r\sqrt{\mathrm{\π}}}\exp [-\frac{{({\mathrm{\σ}}^{\′}-\mathrm{\σ})}^2}{{\mathrm{\γ}}^2}]---\left(5\right)$

Wherein

k is Boltzmann constant, and c is the light velocity, and T is atmospheric temperature, the average quality that m is atmospheric molecule.The signal that detector receives is the convolution of incident light spectrum and transmitance, is respectively:

$S_1\left(\mathrm{\σ}\right)=\mathrm{sI}\left(\mathrm{\σ}\right)\⊗T_1\left(\mathrm{\σ}\right),S_2\left(\mathrm{\σ}\right)=\mathrm{sI}\left(\mathrm{\σ}\right)\⊗T_2\left(\mathrm{\σ}\right)---\left(6\right)$

The responsiveness that wherein s is detector, is made as 1, and convolution can obtain:

$\begin{array}{c}{S}_1=\frac{1}{\mathrm{\γ}\sqrt{\mathrm{\π}}}\exp (-\frac{{\mathrm{\σ}}^2}{{\mathrm{\γ}}^2})\⊗{\sin }^2\frac{\mathrm{n\π\σ}}{\mathrm{\δ}}=\frac{1}{2}[1-\exp (-\frac{{\mathrm{\π}}^2{\mathrm{\γ}}^2}{{\mathrm{\δ}}^2})\cos \frac{2\mathrm{n\π\σ}}{\mathrm{\δ}}]\\ S_2=\frac{1}{\mathrm{\γ}\sqrt{\mathrm{\π}}}\exp (-\frac{{\mathrm{\σ}}^2}{{\mathrm{\γ}}^2})\⊗{\cos }^2\frac{\mathrm{n\π\σ}}{\mathrm{\δ}}=\frac{1}{2}[1+\exp (-\frac{{\mathrm{\π}}^2{\mathrm{\γ}}^2}{{\mathrm{\δ}}^2})\cos \frac{2\mathrm{n\π\σ}}{\mathrm{\δ}}]\end{array}---(7)$

Wherein δ is that optical path difference is reciprocal.Calculate differential signal

$Q=\frac{S_1-S_2}{S_1+S_2}=-\exp (-\frac{{\mathrm{\π}}^2{\mathrm{\γ}}^2}{{\mathrm{\δ}}^2})\cos \frac{2\mathrm{n\π\σ}}{\mathrm{\δ}}---\left(8\right)$

According to Doppler shift principle, the relation of wind speed u and atmospheric backscatter light wave number

$\mathrm{\σ}={\mathrm{\σ}}_0(1+\frac{2u}{c})---\left(9\right)$

The pass that can obtain Q and wind speed after optimization is

$Q\left(u\right)=-\exp (-\frac{{\mathrm{\π}}^2{\mathrm{\γ}}^2}{{\mathrm{\δ}}^2})\cos \left[2\mathrm{n\π}\frac{{\mathrm{\σ}}_0}{\mathrm{\δ}}(1+\frac{2u}{c})\right]---\left(10\right)$

Formula can be finally inversed by air speed value thus.

In order to improve detection accuracy, meet S when optical maser wavelength ₁=S ₂and guarantee that wind speed deviation is minimum, obtain optimum optical path difference:

$l_{\mathrm{opt}}=\frac{c}{2\mathrm{n\π}{\mathrm{\σ}}_0}{\left(\frac{m}{{\mathrm{kT}}_0}\right)}^{1/2}$ 。

Claims (7)

1. a full optical fiber Doppler lidar wind field detection system, it is characterized in that: comprise laser transmitting system (1), optical receiving system (2), frequency discrimination and optical detection system (3) and signal processing system (4), frequency discrimination and optical detection system (3) are connected with signal processing system (4), and laser transmitting system (1) is connected with frequency discrimination and optical detection system (3) by multimode/single mode converter with optical receiving system (2); Laser transmitting system (1) Emission Lasers enters atmosphere, optical receiving system (2) receives the rear orientation light of atmospheric molecule, and be coupled into multimode optical fiber, again after multimode/single mode converter enters frequency discrimination and optical detection system (3) processing, send into signal processing system 4, the treated wind speed information that obtains.

2. full optical fiber Doppler lidar wind field detection system as claimed in claim 1, it is characterized in that: front beam splitter, catoptron and the scanning mirror of being provided with of laser transmitting system (1), laser arrives scanning mirror by beam splitter, catoptron, by scanning mirror, reflected and entered atmosphere, optical receiving system (2) receives the rear orientation light of atmospheric molecule by scanning mirror.

3. full optical fiber Doppler lidar wind field detection system as claimed in claim 1 or 2, is characterized in that: frequency discrimination and optical detection system (3) comprise optical fiber M-Z interferometer and photodetector, and optical fiber M-Z interferometer is by two fiber coupler C ₁, C ₂with two fiber optic interferometric arm L ₁, L ₂form; Light signal, from the input of optical fiber M-Z interferometer input end, is exported by optical fiber M-Z interferometer output port; The light signal of output has two-way route of transmission, and a road is through fiber coupler C ₁straight-through arm, fiber optic interferometric arm L ₁with fiber coupler C ₂straight-through arm, another road is through fiber coupler C ₁transposition arm, fiber optic interferometric arm L ₂with fiber coupler C ₂transposition arm, two paths of signals is interfered mutually at output port, by photodetector, is received.

4. full optical fiber Doppler lidar wind field detection system as claimed in claim 3, is characterized in that: optical fiber M-Z interferometer comprises input end 1 and 2, and optical fiber M-Z interferometer comprises output port 3 and 4; The signal of output port 3 outputs is received by photodetector PMT1, and the signal of output port 4 outputs is received by photodetector PMT2.

5. utilize the detection method of the full optical fiber Doppler lidar wind field detection system as described in claim 1-4 any one, it is characterized in that: the stable seed of laser transmitting system (1) proportion injects ND:YAG pulsed laser, through two frequency-doubling crystal shoot lasers, light beam is through collimating and beam expanding system, beam splitter, catoptron arrives scanning mirror, by scanning mirror, reflect and enter atmosphere, echoed signal receives by optical receiving system (2), then by scatter echo signal coupling in multimode optical fiber, process multimode/single mode converter and collimated enter the input end of optical fiber M-Z interferometer again, 3dB photo-coupler C ₁light is divided into the two-beam that intensity is equal, through thering are two arm transmission of optical path difference, then through three-dB coupler C ₂after interference, from two-port 3 and 4, export, then after being received by detector, send into signal processing system (4), carry out data acquisition and Inversion Calculation, obtain wind speed size information, wind speed direction is determined by optical beam scanning system.

6. detection method as claimed in claim 5, is characterized in that: optical fiber M-Z interferometer output port 3 and 4 transmitance are derived and drawn by coupled mode theory, and when not considering insertion loss, the relation of input light field and output light field can be expressed as:

In formula, E ₁, E ₂respectively the input light field of port one and 2, E ₃, E ₄respectively the output light field of port 3 and 4, k ₁, k ₂respectively fiber coupler C ₁, C ₂coupling coefficient,

n is optical fiber effective refractive index, and l is the arm length difference of interferometer two arms, and σ is incident light wave wave number, by formula (1), can be obtained:

If input signal E ₁=1, E ₂=0, and coupling fiber coefficient k ₁=k ₂=0.5, have:

Therefore the transmitance of two output ports of optical fiber M-Z interferometer is respectively:

The intensity distributions of incident spectrum is I (σ), and form is

Wherein

k is Boltzmann constant, and c is the light velocity, and T is atmospheric temperature, the average quality that m is atmospheric molecule, and the signal that detector receives is the convolution of incident light spectrum and transmitance, is respectively:

The responsiveness that wherein s is detector, is made as 1, and convolution can obtain:

Wherein δ is that optical path difference is reciprocal, calculates differential signal

According to Doppler shift principle, the relation of wind speed u and atmospheric backscatter light wave number

The pass that can obtain Q and wind speed after optimization is

Formula can be finally inversed by air speed value thus.

7. detection method as claimed in claim 6, is characterized in that:

Optimum optical path difference is

。

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