CN102412898B - Wave surface distortion-free free space remote laser transmission simulation device - Google Patents

Abstract

The invention discloses a wave surface distortion-free free space remote laser transmission simulation device. In the device, optical Fourier far field transformation is realized by adopting a long focal length Fourier lens; light field remote transmission simulation is realized by adopting single-stage single-lens imaging and amplifying, optical fiber sampling, optical fiber attenuation and laser collimation; and simulation of vibration of a satellite platform is realized by adopting vibration of an output optical fiber head. By the device, conversion of a light beam from near field distribution to far field distribution can be simulated under a laboratory space scale, and the simulation of the vibration of the satellite platform is realized at the same time. The device is mainly used for communication between two satellite laser communication terminals as well as ground detection and verification of the tracking and pointing performance, has the advantages of simple structure, low cost and wide applicability range, and is easy to adjust.

Description

Wave surface distortion-free free space remote laser transmission simulation device

Technical field

The present invention relates to the fields such as laser space communication, space laser radar and Space-based lasers, particularly laser beam, at a device for free space long distance transmission analog, is mainly used in space laser application system Laser emission corrugated in simulation and the check of far-field characteristic.

Background technology

Space laser application system, comprise laser space communication, space laser radar and Space-based lasers etc., all there is to very high requirement on the transmitting corrugated of laser, this is because the distance between launch terminal and target is all far, the category that belongs to far field, space, so its far-field distribution situation is to need to pay close attention in whole system performance.For laser space communication, far-field distribution situation has directly determined the performance of laser communication link, the final impact communication error rate; For space laser radar, not only can affect the intensity distributions of field of illumination, also can affect the quality of image reconstruction; And just more direct on the impact of Space-based lasers system, the distribution in far field is closely related with the strike effect of laser weapon.But because the operating distance of space laser application system is hundreds of to tens thousand of kilometers, also can not be in space-orbit Performance Detection and the checking that directly completes its far-field distribution, so must build a set of analogue system and be used for applied environment in-orbit that is virtually reality like reality ground experiment is indoor, carry out on this basis the detection validation of space laser application system performance.

At present, for free space long distance laser beam Propagation, simulation substantially all adopts Fourier transform object lens that the corrugated, near field of launch terminal is converted into the far-field distribution of dwindling on its focal plane to home and overseas, then adopt the free space beam transmission of several thousand kilometers to tens0000 kilometers of the principle simulations of imaging amplification and uniform zoom, this scheme can simulate the intensity distributions pattern in far field accurately, but its corrugated is different with actual far-field distribution, this is not all right for spatial coherent laser communication and synthetic aperture laser imaging radar.Chinese Academy of Sciences Shanghai people that ray machine waits had proposed improved modeling scheme afterwards, adopt 4-f imaging amplification system to replace previous einzel lens imaging to amplify, can effectively eliminate the distortion on corrugated like this, but the complexity of system is relatively high, actual dress school is more difficult.

Summary of the invention

The object of the invention is to overcome above-mentioned the deficiencies in the prior art, a kind of Wave surface distortion-free free space remote laser transmission simulation device is provided, to solve in limited space, laboratory simulated laser at the technique effect of free space long-distance transmissions.Be applied to space laser application system, comprise the fields such as laser space communication, space laser radar and Space-based lasers, Laser emission corrugated is in simulation and the check of far-field characteristic, for development and the development of space laser application system, has very large using value.

Technical conceive of the present invention is: long-distance propagation of laser beam has two key properties, the one, and the intensity distributions in far field, the 2nd, the corrugated in far field distributes.The present invention adopts Fourier transform object lens on Qi focal plane, Laser emission corrugated, near field, to be converted into the far-field distribution of dwindling, then adopt einzel lens imaging amplification system that the far-field distribution of dwindling is amplified, employing is carried out aperture sampling with the single-mode polarization maintaining fiber of adjustable attenuator, the intensity distributions of simulation free space long-distance transmissions, then adopt collimation parallel light tube that the point-source of light of polarization maintaining optical fibre output is collimated, the far field plane wave of simulation free space long-distance transmissions, optical fiber head is vibrated on focal plane, to produce the rapid scanning of outgoing plane wave, be used for simulating the Vibration Condition of carrying platform.

Technical solution of the present invention is as follows:

A kind of Wave surface distortion-free free space remote laser transmission simulation device, feature is that its formation comprises: the single-mode polarization maintaining fiber of long-focus fourier transform lens, imaging amplifying lens, adjustable attenuator, optical fiber head fast vibration device and laser alignment lens, and its position relationship is as follows:

Between the first measured laser communication terminal and the second measured laser communication terminal, along optical path direction, be single-mode polarization maintaining fiber, optical fiber head fast vibration device and the laser alignment lens of long-focus fourier transform lens, imaging amplifying lens, adjustable attenuator successively, the emergent pupil face of the front focal plane of described long-focus fourier transform lens and the emission system of the first measured laser communication terminal overlaps; The enlargement ratio of described imaging amplifying lens is M, the object distance of this imaging amplifying lens be exactly the back focal plane of long-focus fourier transform lens from the distance of imaging amplifying lens object space interarea, the input end face of the single-mode polarization maintaining fiber of the picture plane of this imaging amplifying lens and described adjustable attenuator overlaps; The output of the single-mode polarization maintaining fiber of this adjustable attenuator is placed on described optical fiber head fast vibration device, under the driving of the drive motors of this optical fiber head fast vibration device, the optical fiber head fast vibration of the output of the single-mode polarization maintaining fiber of the adjustable attenuator described in driving, the front focal plane of the output end face of the single-mode polarization maintaining fiber of this adjustable attenuator and described laser alignment lens overlaps, and through the plane wave of described laser alignment lens output, by the second described measured laser communication terminal, is received.

Described drive motors is piezoelectric ceramic actuator, or the fast-loop driver of other type.

Technique effect of the present invention:

Wave surface distortion-free free space remote laser transmission simulation device of the present invention, utilize optical Fourier transformation, optical imagery amplifier, aperture sampling, light intensity attenuation and laser collimation technology to realize the long-distance transmissions light intensity of light beam and the physical analogy of PHASE DISTRIBUTION, adopt piezoelectric ceramic actuator to drive the motion simulation in the front focal plane of laser alignment parallel light tube of output optical fibre head to receive the vibration of laser communication terminal carrying platform.The present invention can be applicable to the link communication performance of satellite laser communications terminal and the laboratory of vibration suppression performance and detects, and for development and the development of laser space communication terminal, has very large using value.

Accompanying drawing explanation

Fig. 1 is the light path schematic diagram of Wave surface distortion-free free space remote laser transmission simulation device embodiment of the present invention.

In figure: the front focal plane of 1-long-focus fourier transform lens, 2-long-focus fourier transform lens, the back focal plane of 3-long-focus fourier transform lens, 4-imaging amplifying lens, 5-imaging amplifying lens is as plane, the single-mode polarization maintaining fiber of 6-adjustable attenuator, 7-optical fiber head fast vibration device, 8-laser alignment lens focal plane, 9-laser alignment lens, 10-the first measured terminal, 11-the second measured terminal.

Fig. 2 is optical fiber head fast vibration device schematic diagram of the present invention.

In figure: 12-optical fiber head support, 13-base, the right hold-down screw of 14-, the left hold-down screw of 15-, 16-piezoelectric ceramic actuator base, adjusts screw rod under 17-, the left adjustment screw rod of 18-, 19-optical fiber head, 20-upward adjustment screw, the right adjustment screw rod of 21-, 22-piezoelectric ceramic actuator.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the invention will be further described, but should not limit the scope of the invention with this.

First refer to Fig. 1, the embodiment light path schematic diagram that Fig. 1 is Wave surface distortion-free free space remote laser transmission simulation device of the present invention.As seen from the figure, embodiment of the present invention Wave surface distortion-free free space remote laser transmission simulation device, comprise: the single-mode polarization maintaining fiber 6 of long-focus fourier transform lens 2, imaging amplifying lens 4, adjustable attenuator, optical fiber head fast vibration device 7 and laser alignment lens 9, its position relationship is as follows:

Between the first measured laser communication terminal 10 and the second measured laser communication terminal 11, along optical path direction, be single-mode polarization maintaining fiber 6, optical fiber head fast vibration device 7 and the laser alignment lens 9 of long-focus fourier transform lens 2, imaging amplifying lens 4, adjustable attenuator successively, the emergent pupil face of the front focal plane 1 of described long-focus fourier transform lens 2 and the emission system of the first measured laser communication terminal 10 overlaps; The enlargement ratio of described imaging amplifying lens 4 is M, the object distance of this imaging amplifying lens 4 be exactly the back focal plane 3 of long-focus fourier transform lens from the distance of imaging amplifying lens 4 object space interareas, the input end face of the single-mode polarization maintaining fiber 6 of the picture plane 5 of this imaging amplifying lens and described adjustable attenuator overlaps; The output of the single-mode polarization maintaining fiber 6 of this adjustable attenuator is placed on described optical fiber head fast vibration device 7, under the driving of the piezoelectric ceramic actuator 22 of this optical fiber head fast vibration device 7, the optical fiber head fast vibration of the output of the single-mode polarization maintaining fiber 6 of the adjustable attenuator described in driving, the front focal plane 8 of the output end face of the single-mode polarization maintaining fiber 6 of this adjustable attenuator and described laser alignment lens 9 overlaps, and the plane wave of exporting through described laser alignment lens 9 is received by the second described measured laser communication terminal 11.

The Emission Lasers light beam of the first measured laser communication terminal 10 exit pupil positions is after 2 conversion of long-focus fourier transform lens, at long-focus fourier transform lens back focal plane, 3 places form the far-field distribution of dwindling, using the object plane 3 of this plane as imaging amplifying lens 4, after 4 imagings of imaging amplifying lens, the far field light intensity distributions pattern being amplified as plane 5 at imaging amplifying lens, but far-field distribution phase place now has twice, additional phase place, after the reception optical fiber head coupling of the single-mode polarization maintaining fiber 6 of adjustable attenuator, due to the natural modeling characteristic of monomode fiber, only have with the pattern of monomode fiber coupling and just likely in optical fiber, propagate, therefore at the output of the single-mode polarization maintaining fiber 6 of adjustable attenuator, only retained the information of far field light intensity distributions, twice additional, phase place is got rid of after coupling fiber, the output of the single-mode polarization maintaining fiber of adjustable attenuator 6 is placed on the front focal plane 8 of described laser alignment lens 9, after laser alignment lens 9 collimations, form plane wave, finally by the second measured laser communication terminal 11, received.In addition, the output of the single-mode polarization maintaining fiber 6 of adjustable attenuator drives fast vibration by optical fiber head fast vibration device 7, the Vibration Condition of analog satellite platform, and Fig. 2 is the structural representation of optical fiber head fast vibration device 7 of the present invention.In figure: 12-optical fiber head support, 13-base, the right hold-down screw of 14-, the left hold-down screw of 15-, 16-piezoelectric ceramic actuator base, adjusts screw rod under 17-, the left adjustment screw rod of 18-, 19-optical fiber head, 20-upward adjustment screw, the right adjustment screw rod of 21-, 22-piezoelectric ceramic actuator.Under the driving of described piezoelectric ceramic actuator, the output of the single-mode polarization maintaining fiber 6 of described adjustable attenuator just produces vibration, the Vibration Condition of analog satellite platform.

The light field of supposing the first measured laser communication terminal 10 transmittings is e _a0(x, y), under the physical condition of space, light field is transmitted after several thousand to several ten thousand kilometers, and the optical field distribution of its receiving terminal is the Fraunhofer diffraction of transmitting terminal:

$U_A(x,y)=K_z{E}_{A0}(\frac{x}{{\mathrm{\λ}}_{1}z},\frac{y}{{\mathrm{\λ}}_{1}z}),---\left(1\right)$

Wherein: $K_z=\frac{\exp \left[j\frac{k}{2z}(x^2+y^2)\right]}{\mathrm{i\λz}},$

E _a0(f _x, f _y) be e _a0the Fourier transform of (x, y).

Launch spot very large (tens of to hundreds of rice) when free space long-distance transmissions, and the Receiver aperture of the second measured laser communication terminal 11 is generally hundreds of millimeters, can only receive the far-field spot of a very little part, therefore desirable k _zfor constant.Now the light field at the second measured laser communication terminal 11 places can be expressed as:

$U_A(x,y)=E_{A0}(\frac{x}{{\mathrm{\λ}}_{1}z},\frac{y}{{\mathrm{\λ}}_{1}z})$

In the present invention, the Emission Lasers light beam e at the first measured laser communication terminal 10 emergent pupil places _a0(x, y) first carries out Fourier Far-Zone Field Transformation by long-focus fourier transform lens 2, and the focal length of this long-focus fourier transform lens 2 is f _a, the distance between the emergent pupil of the first measured laser communication terminal 10 and long-focus fourier transform lens is f _a.The back focal plane 3 of long-focus fourier transform lens 2 and the object plane of imaging amplifying lens 4 overlap, and optical field distribution is e _a1(x, y), object distance is l ₁, the focal length of imaging amplifying lens 4 is f _b, the light field as plane 5 places of imaging amplifying lens is e _a2(x, y), image distance is l ₂, be coupled into after the single-mode polarization maintaining fiber 6 of adjustable attenuator, in the optical field distribution of its output, be e _a3(x, y), the front focal plane 8 of output and laser alignment lens 9 overlaps, and after 9 conversion of laser alignment lens focal plane, the optical field distribution at the second reception laser communication terminal 11 places is e _a4(x, y).

The transmitting light field e of the first measured laser communication terminal 10 _a0(x, y), carries out Fourier Far-Zone Field Transformation by long-focus fourier transform lens 2, and the optical field distribution on this long-focus fourier transform lens back focal plane 3 is:

$U(x,y)=K_{A0}{E}_{A0}(\frac{x}{{\mathrm{\λ}}_1{f}_A},\frac{y}{{\mathrm{\λ}}_1{f}_A}),---\left(2\right)$

Wherein: K _a0for constant coefficient.After by this corrugated, Fourier far field, through described imaging amplifying lens, 4 imagings are amplified, in the light field of its image planes, can be expressed as:

$e_{A2}(x_2,y_2)=K_2\underset{-\∞}{\overset{+\∞}{\∫\∫}}\exp (-j\·k\·\frac{x_1^2+y_1^2}{2\·f_B})\·e_{A2}^{\′}(x_1,y_1)\·\exp \{j\frac{k}{2\·l_2}\·[{(x_2-x_1)}^2+{(y_2-y_1)}^2\left]\right\}{\mathrm{dx}}_1\·{\mathrm{dy}}_1---\left(3\right)$

Wherein:

$e_{A2}^{\′}(x_1,y_1)=K_1\·\{\underset{-\∞}{\overset{+\∞}{\∫\∫}}U(x,y)\·\exp \{j\frac{k}{2\·l_1}\·[{(x_1-x)}^2+{(y_1-y)}^2]\}\·\mathrm{dx}\·\mathrm{dy}\},$

K ₁, K ₂for proportionality coefficient.

When meeting image imaging formula:

$\frac{1}{l_1}+\frac{1}{l_2}=\frac{1}{f_B},$

Time, (3) formula can be reduced to:

$e_{A2}(x_2,y_2)=K_2\·K_{A0}\·\frac{1}{M}\·E_{A0}(\frac{x_2}{{\mathrm{\λ}}_1\·f_A\·M},\frac{y_2}{{\mathrm{\λ}}_1\·f_A\·M})\·\exp \{j\frac{k}{2\·l_2}\·[x_2^2+y_2^2\left]\right\}\·\exp \{j\frac{k}{2\·l_1\·M^2}\·[x_2^2+y_2^2]\}---\left(4\right)$

From (1) formula and the contrast of (4) formula, can find out, make the true transmission range z=f in space _aduring M, | U _a(x, y) |=| e _a2(x, y) |.Therefore, under laboratory condition, can realize the conversion of light beam near field distribution to far-field intensity distribution, can simulate free space long-distance transmissions.

But, from (1) formula and (4) formula, relatively can find out, in (4) formula, many additional quadratic phase items, in order to eliminate these additive phases, are coupled to this optical field distribution in polarization-maintaining single-mode fiber, and the light field after coupling can be expressed as:

e _f(x ₃，y ₃)＝e _A2(x ₂，y ₂)·e _f0(x ₃，y ₃)

Wherein, $e_{f0}(x_3,y_3)=A_f\·\exp [-\frac{{x_3}^2+{y_3}^2}{{\mathrm{\ω}}_0^2}]$ Mould field distribution function for optical fiber.

After optical fiber attenuation, the mould field distribution of fiber-optic output is:

$e_f(x_3,y_3)=e_{A2}(x_2,y_2)\·A_f\·{\mathrm{\β}}_f\·\exp [-\frac{{x_3}^2+{y_3}^2}{{\mathrm{\ω}}_0^2}]---\left(5\right)$

Wherein, β _fattenuation coefficient for optical fiber.

Because the output of optical fiber and the focal plane of laser alignment lens overlap, so in the optical field distribution of the back focal plane of laser alignment lens be:

e _ff(x，y)＝e _A2(x ₂，y ₂)·A _f·β _f·FT{e _f(x ₃-δx，y ₃-δy)}

Through substitution of variable, the light field that can obtain the second measured laser communication terminal 11 receptions is:

$e_{\mathrm{ff}}(x,y)=e_{A2}(x_2,y_2)\·A_f\·{\mathrm{\β}}_f\·\exp [-\frac{x^2+y^2}{{\left(\frac{\mathrm{\λ}\·f_B}{\mathrm{\π}\·{\mathrm{\ω}}_0}\right)}^2}]\·\exp \{-\mathrm{jk}(\frac{\mathrm{\δx}\·x}{f_B}+\frac{\mathrm{\δy}\·y}{f_B})\}---\left(6\right)$

Wherein, δ x, the translational movement that δ y is fiber-optic output.

From (6) formula, can find out e _a2(x ₂, y ₂) represent the first measured terminal 10 far-field intensity distribution after long-distance transmissions, represent the wave tilt that the vibration of the second measured terminal 11 carrying platforms causes, the angle of wave tilt is this just illustrates that the present invention can simulate intensity distributions and the corrugated distribution of free space transmission completely truly, and can simulate the Vibration Condition of carrying platform.

The parameter of a specific embodiment that is apparatus of the present invention is below as follows:

Suppose that laser communication link is between high rail satellite and low orbit satellite, interstellar distance is 45000km, and the bore of the first measured laser communication terminal 10 and the second measured laser communication terminal 11 is all Φ=150mm, and primary mirror focal length is all 1m, and optical maser wavelength is 1 micron.

Consider the symmetrical structure of two-way light path, long-focus fourier transform lens 2 is identical with the design of laser alignment lens 8, and bore is identical is all Φ 600mm, much larger than the bore of laser communication terminal, and the identical f of focal length _a=f _b=10m, the multiplication factor of imaging amplifying lens 4 is designed to M=5, and the spot size of the single-mode polarization maintaining fiber 6 of described adjustable attenuator is ω ₀=5 μ m.

Because each components and parts all can exist the unknown losses β such as certain aberration and transmitance in design and the course of processing ₀, therefore before using, must demarcate, according to the result of demarcating, determine optical fiber attenuation coefficient, make identical with the situation of actual far field propagation.

The concrete scaling method of optical fiber attenuation coefficient is as follows:

1, the corrugated of employing standard replaces the corrugated of the first measured laser communication terminal 10, and transmission range theory as required calculates the optical field distribution in actual far field;

2, measure light intensity and the PHASE DISTRIBUTION of apparatus of the present invention output, regulate the attenuation coefficient β of optical fiber simultaneously _f, until identical with the theoretical actual far-field distribution calculating, so far apparatus of the present invention calibration is complete.The distance of simulation free space transmission can be expressed as: $L=M\·f_A\·\frac{\mathrm{\Φ}}{2\·{\mathrm{\ω}}_0}\·\frac{1}{\sqrt{{\mathrm{\β}}_f\·{\mathrm{\β}}_0}};$

3, the first measured laser communication terminal 10 and the second measured laser communication terminal 11 are put in system and can be measured.

Known according to above-mentioned analogue transmission range formula, work as β _fβ ₀=400 o'clock, analogue transmission distance was 7500 kilometers.

The results showed, apparatus of the present invention not only can realize the simulation of communication link laser far-distance transmission between two satellites in limited space, laboratory, and vibration that can analog satellite platform.The present invention can be applicable to the optical acquisition pointing performance of satellite laser communications terminal and the laboratory of communication performance and detects, and for development and the development of laser space communication terminal, has very large using value.That the present invention has advantages of is simple in structure, cost is low, be easy to regulate, applicability is wide.

Claims (2)

1. a Wave surface distortion-free free space remote laser transmission simulation device, be characterised in that its formation comprises: the single-mode polarization maintaining fiber (6) of long-focus fourier transform lens (2), imaging amplifying lens (4), adjustable attenuator, optical fiber head fast vibration device (7) and laser alignment lens (9), its position relationship is as follows:

Between the first measured laser communication terminal (10) and the second measured laser communication terminal (11), along optical path direction, be single-mode polarization maintaining fiber (6), optical fiber head fast vibration device (7) and the laser alignment lens (9) of long-focus fourier transform lens (2), imaging amplifying lens (4), adjustable attenuator successively, the emergent pupil face of the front focal plane (1) of described long-focus fourier transform lens (2) and the emission system of the first measured laser communication terminal (10) overlaps, the enlargement ratio of described imaging amplifying lens (4) is M, the object distance of this imaging amplifying lens (4) be exactly the back focal plane (3) of long-focus fourier transform lens from the distance of imaging amplifying lens (4) object space interarea, the input end face of the single-mode polarization maintaining fiber (6) of the picture plane (5) of this imaging amplifying lens and described adjustable attenuator overlaps, the output of the single-mode polarization maintaining fiber of this adjustable attenuator (6) is placed on described optical fiber head fast vibration device (7), under the driving of the drive motors of this optical fiber head fast vibration device (7), the optical fiber head fast vibration of the output of the single-mode polarization maintaining fiber (6) of the adjustable attenuator described in driving, the front focal plane (8) of the output end face of the single-mode polarization maintaining fiber of this adjustable attenuator (6) and described laser alignment lens (9) overlaps, plane wave through described laser alignment lens (9) output is received by the second described measured laser communication terminal (11).

2. Wave surface distortion-free free space remote laser transmission simulation device according to claim 1, is characterized in that described drive motors is piezoelectric ceramic actuator, or the fast-loop driver of other type.