| Free space optics communication (FSO) is a new way of the wirelesscommunication, it concludes many aspects, for example: the wireless lasercommunications between the deep space, middle orbit and ground stations. In someconditions the communication between the satellite and the ground exists. Generallywe also called the laser communication between the ground stations “atmosphericlaser communication”.FSO attracts more and more researchers because it has the following advantages:FSO can offer the considerably high transmit rate, which matches the transmit rate inthe optical fiber. Even in some conditions, the rate of FSO can access2.5Gb/s, andthe communication distance can be4km; There is no limitation of spectrum in FSO,so this is an important advantage relative to the conventional radio frequency wirelesscommunication.Of course there are many problems in the FSO system, in the transmit process ofvisible light, one of the bottlenecks limit the communication quality andcommunication distance is the atmospheric attenuation and the fluctuation of lightintensity. Atmospheric absorption and scattering lead to visible light intensityattenuation, atmospheric turbulence can cause atmospheric scintillation, beam drift,arrival angle fluctuation and wave-front aberration. In order to overcome the influenceof atmospheric turbulence and realize the effective channel compensation, a lot ofexperimental researches and theoretical explorations are required.The use of combinational deformable mirror (CDM) in FSO has its precedent.Different from the previous CDM, the CDM proposed in this paper mainly considersthe parameter and the structure of the deformable mirror. Different structures of theCDM have conspicuous differences in the compensation of the wave-front aberration,in this paper, we take the two deformable mirrors to cope with the different types ofwave-front aberrations, and get the best result. In addition, a decoupling algorithm-confinement correction algorithm–is also introduced.There are some drawbacks or limitations in the traditional PID control algorithmwhen it is used in the adaptive optics systems or the free-space optical communicationsystems. The tuning technology of PID parameters is not mature enough, generally,which always depends on the experience of the operators. It is not advisable in somesituation which needs high precision requirements, like the visible lightcommunication atmosphere communication system in this paper, especially theperformance of the wave-front detection equipment will fall sharply under some strong turbulence situation. Then the new adaptive optics system without thewave-front sensor equipment and based on the intelligent optimal control algorithmsmakes sense.In this paper, we propose an adaptive optics control system based on someoptimization algorithms namely, stochastic parallel gradient descent (SPGD)algorithm, simulated annealing (SA) algorithm, modified artificial fish swarm (MAFS)algorithm, modified shuffled frog leaping (MSFL) algorithm and so on, which hasbetter compensation effect on the wave-front distortion, and the optical couplingefficiency of receiving end is improved obviously.Presented simulation results demonstrate that the deformable mirrors and acombination of heuristics or swarm intelligent bionic optimization algorithm proposedin this paper can get better results in the adaptive optics system or free-space opticalcommunication systems. The above optimization algorithms can achieve a good finalconvergence value by fewer iterative loop, thus efficiently improve communicationquality of the total free-space optical communication systems. |
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