CN203909299U - All-fiber laser radar aerosol detection device - Google Patents

Abstract

The utility model discloses an all-fiber laser aerosol detection device, which comprises a signal transmitting channel, a signal receiving channel and a signal processing channel, wherein the signal transmitting channel is used for emitting laser signals; the signal receiving channel is used for receiving the emitted laser signals and receiving echo signals generated by emission of the laser signals into the atmosphere; the signal processing channel is used for converting the echo signals into electric signals and analyzing and processing the electric signals; and the signal transmitting channel, the signal receiving channel and the signal processing channel are of an all-fiber structure. The all-fiber laser radar aerosol detection device has the characteristics of continuous high repetition frequency, high sensitivity and the like, adopts the all-fiber structure, can achieve up to 20kHz picowatt-level signal detection, and has very high temporal-spatial resolution. The overall system is small in size and high in stability.

Description

Full optical fiber laser radar aerosol detection device

Technical field

The utility model belongs to laser radar field, particularly a kind of full optical fiber laser radar aerosol detection device.

Background technology

Atmospheric aerosol refers to and is suspended in the liquid or solid particulate that in atmosphere, diameter is 0.001-100um, and its generation is subject to the impact of natural source (volcano, sandstorm etc.) and artificial source's (industry, rural activity etc.) many factors.Although the content of gasoloid in atmosphere is relatively less, can change the circulation pattern of atmosphere, affect air quality and the climate change in some areas, even jeopardize people's health of human body and living environment.Therefore, the research of aerosol detection is also subject to increasing attention in recent years.

Laser radar is one of effective means of atmospheric parameter detection, is that one has high-spatial and temporal resolution, can monitor continuously the active remote sensing equipment that gasoloid changes.Due to characteristics such as laser beam divergence are little, wavelength is short, energy density is high, monochromaticity is good, can be effectively and atmospheric aerosol particle interaction, make laser radar can effectively monitor aerosol optical characteristics and distribution characteristics, make up over the deficiency of traditional detection instrument.

Conventional be used for accurately measuring the distributed intelligence of inverting atmospheric aerosol have Raman lidar and a high spectral resolution lidar, both compare, Raman lidar is that a kind of structure is relatively simple, with low cost, emerging a kind of aerosol detection Radar Technology, obtain aerosol properties information by laser and the indirect inverting of particulate inelastic scattering, must consider particulate component, scattering spectrum and suppress the impact of other scattered signals etc.Mie's scattering laser radar is the most common a kind of radar that is used for measuring aerosol properties, utilize the Mie scattering between laser and atmospheric aerosol particle to obtain corresponding echoed signal, scatter echo is relevant with scattering particle (as gasoloid), thereby some parameter that can Inversion Calculation goes out to characterize scattering particle characteristic is (with reference to [1] Zhou Jun, Yue Guming etc. Optical Properties of Aerosol Derived from Lidar Measurements [J]. quantum electronics report, 1988,15 (2)).

Prior art [2] (the wide space of uncle etc. atmospheric sounding temperature and aerocolloidal Rayleigh-Raman-Mie's scattering laser radar [J]. Acta Optica, 2010,30 (1)) troposphere, Hefei district temperature, aerocolloidal routine observation data have been provided, adopt 532nm pulsed solid stale laser, under 20Hz repetition, the spatial resolution of accumulative total 10000 subpulse signal acquisition 30m; Prior art [3] (Zhou jun, et al.Two-Wavelength Mie Lidar for Monitoring of Tropospheric Aerosol[J] .Acta Optica Sinica, 2000,20 (10)) set up a dual wavelength Mie scattering laser radar, survey the Vertical Profile of two wavelength troposphere Aerosol Extinction of 532nm and 1064nm simultaneously, also be to adopt pulsed solid stale laser, space optical path to realize echoed signal to survey, huge structure complexity (needing water-cooled), repetition is low, and resolution is limited.

Utility model content

Utility model object: the utility model aims to provide a kind of continuous high repetition, high sensitivity full optical fiber laser radar aerosol detection device, adopts all optical fibre structure to realize, and can realize up to 20kHz the acquisition of signal of micromicrowatt magnitude; Have very high spatial and temporal resolution, whole system volume is little, and stability is high.

Technical scheme: a kind of full optical fiber laser radar aerosol detection device, comprising:

Signal transmission channel, for sending laser signal;

Signal receiving cable, shines for receiving the laser signal sending and receiving laser signal the echoed signal that atmosphere produces;

Signal processing channel, for being converted to echoed signal electric signal and carrying out analyzing and processing;

Described signal transmission channel, signal receiving cable and signal processing channel are all optical fibre structure.

Between described signal transmission channel and signal receiving cable, circulator is set, for the transmitting of laser signal is coaxial with the receiving light path of echoed signal, circulator is also connected with signal processing channel, and the echoed signal that signal receiving cable receives is transported to signal processing channel via circulator.

Described circulator is three port organizations, the port I of circulator connects signal transmission channel, the port II of circulator connects signal receiving cable, the port III of circulator connects signal processing channel, the laser signal that signal transmission channel sends exports signal receiving cable to by port II after being input to port I, and the echoed signal that signal receiving cable receives is input to port II and exports signal processing channel to by port III.

Described signal transmission channel comprises pulse optical fiber and optoisolator, and pulse optical fiber is all optical fibre structure, regulates for sending laser signal and the pulsewidth to laser signal and power.Adopt all optical fibre structure pulsed laser as signal source, have high repetition, high-average power, pulsewidth, the adjustable feature of power, beam quality is high, and Stability Analysis of Structures, without water-cooled.

Described optoisolator is fibre optic isolater, is connected, for eliminating the impact on laser instrument of echoed signal by fused fiber splice with pulse optical fiber.

Described signal receiving cable comprises the conduction optical fiber, the telescopic system that set gradually along the described laser signal direction of propagation, and telescopic system comprises eyepiece and object lens, and conduction optical fiber is positioned at the front focal plane place of eyepiece, completes fiber coupler function with eyepiece.

The multimode optical fiber that described conduction optical fiber is thick fibre core, the numerical aperture NA>=0.18 of conduction optical fiber, has large-numerical aperture.

Described signal processing channel comprises along the filter plate, avalanche photodide, photon counter and the data handling system that set gradually.Avalanche photodide coordinates filter plate use to have gain and feature highly sensitive, fast response time, can realize the real-time detection of feeble signal, increases overall detectivity.

Described filter plate is the online narrow band filter slice of 1064nm, two ends band optical fiber output encapsulation.

Described avalanche photodide is optical fiber receiving port, for directly receiving fiber-optic signal or spatial light signal.

Principle of work: the laser signal sending passes through optical isolator, circulator successively, and by conducting the direct output injection of optical fiber to telescopic system, directive atmosphere after collimator and extender; Again be coupled into conduction optical fiber by the echoed signal of aerosol scattering by telescope receiving system, and change direction through circulator, output to filter plate by optical fiber, change electric signal into through avalanche photodide, can obtain required aerosol properties data by follow-up photon counter, data processing and inverting.

Beneficial effect: the utility model proposes and adopt all optical fibre structure to realize, can realize up to 20kHz the acquisition of signal of micromicrowatt magnitude; Have very high spatial and temporal resolution, whole system volume is little, and stability is high.Pulse optical fiber has high light beam quality, and repetition is up to 20kHz, and average power is 10W, and pulsewidth 10～200ns is adjustable, and the 1064nm laser of output is suitable for Mie's scattering laser radar application, can obtain sooner the higher aerosol properties data of resolution.The inner fiber optic conduction signal that adopts of laser radar, can better eliminate stray light, increases signal to noise ratio (S/N ratio).Can effectively realize Detection of Weak Signals, structure is tightly short light, simple and stable.

Also there is following features compared with current aerosol detection scheme:

1. adopt all optical fibre structure pulsed laser as signal source, have high repetition, high-average power, pulsewidth, the adjustable feature of power, beam quality is high, and Stability Analysis of Structures, without water-cooled;

2. signal transmitting and receiving all adopts all optical fibre structure to realize, and reduces optical path loss, makes system bulk small and exquisite, simple in structure; It is coaxial that the use of circulator can realize dual-mode antenna, reduced signal tracing, caught difficulty.

3. avalanche photodide coordinates filter plate use to have gain and feature highly sensitive, fast response time, can realize the real-time detection of feeble signal, increases the detectivity of system.

4. laser radar is that one has high-spatial and temporal resolution, continuous type active remote sensing equipment, can networking data share, and realizes the monitoring that the long-time gasoloid of large format changes.

Brief description of the drawings

Fig. 1 is schematic diagram of the present utility model.

Embodiment

As shown in Figure 1, a kind of full optical fiber laser radar aerosol detection device, comprises pulse optical fiber 1, optoisolator 2, circulator 3, conduction optical fiber 4, telescopic system 5, outgoing beam 6, echoed signal 7, filter plate 8, avalanche photodide 9, photon counter 10 and data handling system 11.Telescopic system 5 is made up of eyepiece 51, object lens 52, is the telescopic system of standard, simultaneously as emitting antenna and receiving antenna; Pulse optical fiber 1 is the full fiber pulse laser of MOPA structure, wavelength 1064nm, average power <10W, repetition <20kHz, pulsewidth and power are adjustable, pulse optical fiber 1 repetition frequency is from tens Hz to 20kHz, and pulsewidth is that 10-200ns is adjustable, and pulse optical fiber 1 makes the utility model gasoloid radar spatial resolution limit can reach tens tens meters of precision even.The laser signal that pulse optical fiber 1 produces directly outputs to telescopic system eyepiece 51, object lens 52 by 4 scatterings of conduction optical fiber through optoisolator 2, circulator 3, after beam-expanding collimation, directly exports as outgoing beam 6; Circulator 3 is three port organizations, the port I of circulator is connected with optoisolator 2, the end face of the conduction optical fiber 4 that the port II of circulator connects is positioned at the front focal plane place of telescopic system 5 eyepieces 51, complete fiber coupler function with eyepiece 51, port III is directly connected with avalanche photodide 9 optical fiber by filter plate 8.The laser signal that pulse optical fiber 1 sends exports conduction optical fiber 4 to by port II after optoisolator 2 is input to port I, and the echoed signal 7 that signal receiving cable receives is input to port II and exports filter plate 8 to by port III.

The echoed signal 7 of aerosol scattering receives and is coupled into conduction optical fiber 4 through telescopic system 5, by the unidirectional filter plate 8 that incides of circulator 4, after avalanche photodide 9 opto-electronic conversion, obtain corresponding digital signal by photon counter 10 and give data handling system 11.The multimode optical fiber that conduction optical fiber 4 is thick fibre core, has large-numerical aperture, and numerical aperture NA>=0.18, has larger acceptance angle; Filter plate 8 is the online narrow band filter slice of 1064nm, two ends band optical fiber output encapsulation; Avalanche photodide 9 can be configured to optical fiber receiving port, can directly receive fiber-optic signal or spatial light signal.Optoisolator 2 is fibre optic isolater, is connected with circulator 3 and pulse optical fiber 1 by fused fiber splice, eliminates the impact on laser instrument of echoed signal 7.

The 1064nm laser signal that pulse optical fiber 1 sends connects output injection to directive atmosphere after telescopic system 5 collimator and extenders by optoisolator 2, circulator 3 and by conduction optical fiber 4 successively; Again be coupled into conduction optical fiber 4 by the echoed signal 7 of aerosol scattering by telescopic system 5, and change direction through circulator 3, output to filter plate 8 by optical fiber, change electric signal into through avalanche photodide 9, can obtain required aerosol properties data by follow-up photon counter 10, data handling system 11 invertings.

Wherein pulse optical fiber 1 output power also can, by regulating seed source 101 and pumping source 105 power to mate with gasoloid layer height, be 10W to the maximum; Avalanche photodide 9 has high sensitivity and high gain characteristics, and full optical fiber optical optical road contributes to suppress parasitic light and sneak into, and therefore whole device can be realized high s/n ratio, micromicrowatt magnitude weak echo signal is surveyed.

The utility model is surveyed aerocolloidal principle process:

In atmosphere, main elastic scattering has Mie scattering and Rayleigh scattering, and scattering strength is all with highly reducing, and relevant with wavelength length, and short wavelength's Rayleigh scattering is stronger, and long wavelength's Mie scattering is main; Select 1064nm that wavelength grows as signal laser herein, can obtain stronger Mie scattering signal.

For Mie scattering laser radar, the aerocolloidal laser radar equation of its atmospheric sounding can be expressed as:

$P\left(z\right)=\frac{P_0\mathrm{C\&beta;}\left(z\right)}{z^2}\exp [-2{\&Integral;}_0^z\mathrm{\&alpha;}\left(z\right)\mathrm{dz}],$

P in formula ₀for the emissive power of laser, the system constants that C is laser radar, z is detection range, and α (z) and β (z) are respectively total backscattering coefficient and the extinction coefficient of height z place atmosphere.

To general atmospheric environment, adopt Klett method inverting atmospheric extinction coefficient, there is following relation in factor alpha (z) and β (z):

β(z)＝B·α ^k(z)

Consider the square distance correction function of laser radar echo signal:

D(z)＝P(z)·z ²

Z _cthe extinction coefficient α (z) and the backscattering coefficient β (z) that locate the particulate on following height are respectively:

$\mathrm{\&alpha;}\left(z\right)=\frac{P\left(z\right)\&CenterDot;z^2}{\frac{P\left(z_c\right)\&CenterDot;z_c^2}{\mathrm{\&alpha;}\left(z_c\right)}+2{\&Integral;}_{z^{,}}^{z_c}P\left(z^{,}\right)\&CenterDot;z^{,2}d{z}^{,}}-{\mathrm{\&alpha;}}_m\left(z\right)$

$\mathrm{\&beta;}\left(z\right)=\frac{P\left(z\right)\&CenterDot;z^2}{\frac{P\left(z_c\right)\&CenterDot;z_c^2}{\mathrm{\&beta;}\left(z_c\right)}+2S{\&Integral;}_{z^{,}}^{z_c}P\left(z^{,}\right)\&CenterDot;z^{,2}d{z}^{,}}-{\mathrm{\&beta;}}_m\left(z\right)$

In formula, B is relevant with the distribution of yardstick spectrum with the character of laser radar wavelength and particulate with k, and span can be consulted pertinent literature and be obtained, and S is Lidar Ratios, z _cfor a certain boundary height value of prior known extinction coefficient and backscattering coefficient; α _mand β (z) _m(z) be respectively atmospheric molecule extinction coefficient and backscattering coefficient, specifically can obtain by United States standard atmosphere model.

Therefore, as long as accurately measure the echoed signal power of Mie scattering, just can be finally inversed by Aerosol Extinction and the backscattering coefficient of corresponding height in atmosphere, gained extinction coefficient is quadratured and can be obtained the optical thickness of atmospheric aerosol, through long-time observation and iteration, finally obtain distribution character and the variation tendency of gasoloid large format.

And adopt avalanche photodide 9 and photon counter 10 receiving element as echoed signal, in fact that record is the power of echoed signal 7 and corresponding photoelectron number N (z), closes to be with received optical power P (z):

$N\left(z\right)=\left(\frac{\mathrm{\&eta;\&lambda;}}{\mathrm{hc}}\right)P\left(z\right)\&CenterDot;\mathrm{\&Delta;t}$

The quantum efficiency that in formula, η is avalanche photodiode detector, λ is corresponding optical maser wavelength, and h is Plank constant, and Δ t is the acquisition time of Mie's scattering laser radar signal, Δ t=2 Δ z/c, Δ z correspondence the range resolution in space; Because avalanche photodide has higher interior gain, for the echoed signal P (z) of certain power, photon counter minimum response degree is constant, contrary, and z is less for range resolution Δ, and the spatial resolution of system is higher.

The specific design parameter of an embodiment below:

A kind of full optical fiber laser radar aerosol detection device, pulse optical fiber 1 adopts two-stage MOPA structure to realize, seed source 101 is pulsed drive 1064nm semiconductor laser, output peak power is 1W, the 976nm semiconductor laser that pumping source 105 is pulsed drive, the first gain fibre 103, the second gain fibre 108 is yb-doped double-clad fiber, fibre core/covering is 10/130um, every grade is amplified about 17dB, final pulse optical fiber 1 is realized repetition 10kHz, pulsewidth 20ns, the pulsed light output of the about 10kW of peak power, power stability is less than 3%, beam quality 1.3.Connect the conduction optical fiber 4 internal diameter 200um of telescopic system 5 and circulator 3, NA=0.22, corresponding fiber optic acceptance angle is 12.7 degree.Consider when telescopic system 5 expands to reduce system field angle, therefore telescopic system 5 enlargement factor M can not be too large, but in order to receive more echoed signal energy, need again more bigbore telescope objective 52, consider and get telescope enlargement factor M=6 herein, object lens 52 bores are 300mm, and eyepiece 51 bores are 50mm, and eyepiece 51 focal lengths are 200mm.This sentences optical fiber field of view of receiver and calculates, effective field of view of receiver of system is 2.2 degree, if optical coupling efficiency minimum is 10%, avalanche photodide 9 minimum detectable power are 0.5pW/Hz1/2, can realize minimum hundred micromicrowatt echo powers surveys, the spatial discrimination distance of tens meters, has higher sensitivity and spatial resolution.

Claims (10)

1. a full optical fiber laser radar aerosol detection device, is characterized in that, comprising:

Signal transmission channel, for sending laser signal;

Signal receiving cable, shines for receiving the laser signal that signal transmission channel sends and receiving laser signal the echoed signal (7) that atmosphere produces;

Signal processing channel, for being converted to echoed signal (7) electric signal and carrying out analyzing and processing;

Described signal transmission channel, signal receiving cable and signal processing channel are all optical fibre structure.

2. full optical fiber laser radar aerosol detection device according to claim 1, it is characterized in that, circulator (3) is set between described signal transmission channel and signal receiving cable, for the transmitting light path of laser signal is coaxial with the receiving light path of echoed signal (7), circulator (3) is also connected with signal processing channel, and the echoed signal (7) that signal receiving cable receives is transported to signal processing channel via circulator (3).

3. full optical fiber laser radar aerosol detection device according to claim 2, it is characterized in that, described circulator (3) is three port organizations, the port I of circulator (3) connects signal transmission channel, the port II of circulator (3) connects signal receiving cable, the port III of circulator (3) connects signal processing channel, the laser signal that signal transmission channel sends exports signal receiving cable to by port II after being input to port I, the echoed signal (7) that signal receiving cable receives is input to port II and exports signal processing channel to by port III.

4. full optical fiber laser radar aerosol detection device according to claim 1, it is characterized in that, described signal transmission channel comprises pulse optical fiber (1) and optoisolator (2), pulse optical fiber (1) is all optical fibre structure, regulates for sending laser signal and the pulsewidth to laser signal and power.

5. full optical fiber laser radar aerosol detection device according to claim 4, it is characterized in that, described optoisolator (2) is fibre optic isolater, be connected with pulse optical fiber (1) by fused fiber splice, for eliminating the impact on laser instrument of echoed signal (7).

6. full optical fiber laser radar aerosol detection device according to claim 1, it is characterized in that, described signal receiving cable comprises the conduction optical fiber (4), the telescopic system (5) that set gradually along the described laser signal direction of propagation, telescopic system (5) comprises eyepiece (51) and object lens (52), conduction optical fiber (4) is positioned at the front focal plane place of eyepiece (51), completes fiber coupler function with eyepiece (51).

7. full optical fiber laser radar aerosol detection device according to claim 6, is characterized in that, the multimode optical fiber that described conduction optical fiber (4) is thick fibre core, the numerical aperture NA>=0.18 of conduction optical fiber (4).

8. full optical fiber laser radar aerosol detection device according to claim 1, it is characterized in that, described signal processing channel comprises along the filter plate (8), avalanche photodide (9), photon counter (10) and the data handling system (11) that set gradually.

9. full optical fiber laser radar aerosol detection device according to claim 8, is characterized in that, described filter plate (8) is the online narrow band filter slice of 1064nm, two ends band optical fiber output encapsulation.

10. full optical fiber laser radar aerosol detection device according to claim 8, is characterized in that, described avalanche photodide (9) is optical fiber receiving port, for directly receiving fiber-optic signal or spatial light signal.