In the satellite to earth laser communication link, large-aperture ground laser communication terminals usually are used in order to realize the requirement of high rate and long distance communication and restrain the power fluctuation by atmospheric scintillation. With the increasing of the laser communication terminal caliber, the primary mirror weight should also be increased, and selfweight, thermal deformation and environment will affect the surface accuracy of the primary mirror surface. A high precision vehicular laser communication telescope unit with an effective aperture of 600mm was considered in this paper. The primary mirror is positioned with center hole, which back is supported by 9 floats and the side is supported by a mercury band. The secondary mirror adopts a spherical adjusting mechanism. Through simulation analysis, the system wave difference is better than λ/20 when the primary mirror is in different dip angle, which meets the requirements of laser communication.
A novel realization method of a high-precision and wide-range echo-laser simulator is presented according to the detection requirement for ranging performance measurement of some fire control equipment.The simulator is designed to achieve both high resolution precision and wide dynamic range, the method of time delay combined with counter method and time to amplitude conversion method is adopted, the first stage time delay adopts the counter method which use FPGA as the core device to enlarge the simulation range, the second stage delay adopts time to amplitude conversion method which use a ramp delay circuit as the core device to improve the resolution precision of the simulation. The method can realize echo laser simulation of 0.5m high-precision with 50m-2km wide range, the detailed design of each component of the laser echo simulator is also given in this paper. The experimental results show that the echo simulation accuracy of the simulator is better than 0.5m, meeting the detection requirement of laser ranger performance test.
The research of laser communication system primary mirror deformation caused by back surface shape variation was done in this paper. The usual mirror back surface shapes were sphere, double arch, flat and biconcave shape and so on. Based on the four shape mirror, with the center hole rim support pattern, the four shape mirror temperature distribution equation was inferred by thermal elastic theory, deformation are compared in 1-5℃ radius direction temperature difference, in the case of minor weight gap and equal maximum thickness. As a result, the deformation of sphere back surface shape mirror is minimal. So sphere back surface shape is fit for the primary mirror.
Reconnaissance aircraft is an important node of the space-air-ground integrated information network, on which equipped with a large number of high-resolution surveillance equipment, and need high speed communications equipment to transmit detected information in real time. Currently RF communication methods cannot meet the needs of communication bandwidth. Wireless laser communication has outstanding advantages high speed, high capacity, security, etc., is an important means to solve the high-speed information transmission of airborne platforms. In this paper, detailed analysis of how the system works, the system components, work processes, link power and the key technologies of airborne laser communication were discussed. On this basis, a prototype airborne laser communications was developed, and high-speed, long-distance communications tests were carried out between the two fixed-wing aircraft, and the airborne precision aiming, atmospheric laser communication impacts on laser communication were tested. The experiments ultimately realize that, the communication distance is 144km, the communication rate is 2.5Gbps. The Airborne laser communication experiments provide technical basis for the application of the conversion equipment.
Proc. SPIE. 9795, Selected Papers of the Photoelectronic Technology Committee Conferences held June–July 2015
KEYWORDS: Sensors, Computing systems, Control systems, Telecommunications, Optical communications, Optical tracking, Servomechanisms, Laser communications, Control systems design, Laser systems engineering
Airborne space laser communication is characterized by its high speed, anti-electromagnetic interference, security, easy to assign. It has broad application in the areas of integrated space-ground communication networking, military communication, anti-electromagnetic communication. This paper introduce the component and APT system of the airborne laser communication system design by Changchun university of science and technology base on characteristic of airborne laser communication and Y12 plan, especially introduce the high communication speed and long distance communication experiment of the system that among two Y12 plans. In the experiment got the aim that the max communication distance 144Km, error ＜10-6（2.5Gbps） ＜10-7（1.5Gbps），capture probability ＞97%, average capture time 20s. The experiment proving the adaptability of the APT and the high speed long distance communication.
For laser communication performance which carried by airplane or airship, due to high-speed platform movement, the air
has two influences in platform and laser communication terminal window. The first influence is that aerodynamic effect
causes the deformation of the optical window; the second one is that a shock wave and boundary layer would be
generated. For subsonic within the aircraft, the boundary layer is the main influence. The presence of a boundary layer
could change the air density and the temperature of the optical window, which causes the light deflection and received
beam spot flicker. Ultimately, the energy hunting of the beam spot which reaches receiving side increases, so that the
error rate increases. In this paper, aerodynamic theory is used in analyzing the influence of the optical window
deformation due to high speed air. Aero-optics theory is used to analyze the influence of the boundary layer in laser
communication link. Based on this, we focused on working on exploring in aerodynamic and aero-optical effect
suppression method in the perspective of the optical window design. Based on planning experimental aircraft types and
equipment installation location, we optimized the design parameters of the shape and thickness of the optical window,
the shape and size of air-management kit. Finally, deformation of the optical window and air flow distribution were
simulated by fluid simulation software in the different mach and different altitude fly condition. The simulation results
showed that the optical window can inhibit the aerodynamic influence after optimization. In addition, the boundary layer
is smoothed; the turbulence influence is reduced, which meets the requirements of the airborne laser communication.
With the highlights of the high transmission rate, large capacity, strong anti-interference and anti-capture ability, good
security and small light, space laser communication becomes an important hotspot. At present, the focus of research of
the laser communication system is point to point communication structure. However, from the application point of view,
both the realization of space laser communication among multiple points and the establishment of the information
transmission network can really have the practical value. Aiming at the problem of space laser communication network,
this article puts forward the general idea about optical antenna to achieve multiple tracking goals at the same time.
Through the analysis of the optical antenna, and the comparing of the current commonly used mirror driving mechanism,
a new mirror driving mechanism is designed. The azimuth motion, containing circular grating feedback, is driven by
torque motor，voice coil motor of fan produces pitch motion that has fan-shaped grating feedback, so that compression of the structure size to improve the efficiency of the reflector assembly. Through the establishment of the driving mechanism and the kinematic model of 3D entity, the relationship between the single drive azimuth and pitch angle following the angle of incident light is explained. The biggest ideal view area affecting the optical antenna is obtained by the simulation analysis of the kinematics model using MATLAB. The several factors of field overlap area and blind area offers a theoretical basis for structure optimization and control system for the subsequent optical antenna design.
In the space laser communication terminal with rotation-mirror, course- tracking system achieves APT (Alignment
Pointing and Tracking) function by a two-axis rotation-mirror and reduces the weight and power dissipation of the
system. Image rotation will be exist, if the photoelectric-detect unit is fixed and not rotate with rotation-mirror. Rotation
of mirror will make revolution between coordinates of mirror and detector, in which mirror’s adjust-angle is not linear to
detection-angle. In the paper, firstly math model of rotation-mirror course-tracking system for laser communication
terminal based on the vector theory of optical reflection is established and deduces the adjust formulation of mirror
tracking the beacon laser, figuring out relation between adjust-angle and detection-angle. As a result, the formulation is
very complex and is not desired for system. To optimize computed efficiency, the relationship between rotation-mirror
angle and the detector’s elevation and azimuth is analyzed in detail. The calculating formulation to eliminate
image-rotation's affection is simplified, while the angle error of this method has been got. Analytical result shows the
maximum calculating error is 3.9μrad, being satisfied with the need of course-tracking accuracy. The paper presents the
adjust-angle formulation for the two-axis rotation mirror course-tracking system used for laser communication terminal,
is useful for the design of tracking system.
The sight-axis alignment can be accomplished by the quick acquisition operation between two laser communication
terminals, which is the premise of establishing a free-space optical communication link. Especially for the laser
communication links of LEO (Low Earth Orbit)-Ground and LEO-GEO (Geostationary Earth Orbit), since the earth
would break the transmission of laser and break the communication as well, so the effective time for each
communication is very shot (several minutes~ dozens of minutes), as a result the communication terminals have to
capture each other to rebuild the laser communication link. In the paper, on the basis of the analysis of the traditional
methods, it presents a new idea that using the long beacon light instead of the circular beacon light; thereby the original
of two-dimensional raster spiral scanning is replaced by one-dimensional scanning. This method will reduce the setup
time and decrease the failure probability of acquisition for the LEO-GEO laser communication link. Firstly, the
analysis of the external constraint conditions in the acquisition phase has been presented in this paper. Furthermore, the
acquisition algorithm models have been established. The optimization analysis for the parameters of the acquisition unit
has been carried out, and the ground validation experiments of the acquisition strategy have also been performed. The
experiments and analysis show that compared with traditional capturing methods, the method presented in this article can
make the capturing time be shortened by about 40%, and the failure probability of capturing be reduced by about 30%.
So, the method is significant for the LEO-GEO laser communication link.