| Free space optical communication technology,also known as wireless laser communication technology,enjoys its popularity for fast transmission speed and good confidentiality.Wireless laser communication technology has great prospects in the scene where the cables for sea termimals are difficult to be deployed,such as ships,islands,etc.However,the wavefront distortion caused by maritime atmosphere turbulence can cause dispersion of laser beam and energy,leading to a severe reduction of the communication efficiency.The adaptive optics system can correct the wavefront distortion timely and improve the energy of the laser beam received by the communication terminal.Therefore,the adaptive optics system is widely used in wireless laser communication systems.In this paper,a set of adaptive optics system is built,which includes two deformable mirrors,a wavefront sensor and a far-field camera.In the MATLAB platform,the algorithm of the adaptive optics system is developed and verified.The main methods include:using the Nelder-Mead simplex algorithm to pre-optimize the intensity of the laser beam to compensate for dimly laser beam caused by defects of hardware.The linear regression algorithm is used to estimate the linear model between the input voltages of the system and the positions of the centroids of the laser.Based on the system model,a compensation controller is designed to correct the wavefront distortion.Supplementary software with GUI(Graphical User Interface)is developed,where C++ and C#mixed programming is adopted for the Demo.The experimental results show that the intensity of laser beam becomes brighter and the energy is more convergent,with the help of light intensity pre-optimization using Nelder-Mead simplex algorithm.The light intensity of the brightest pixel increases from 74.5 to 215(overexposure),and the sum light intensity rises from 181.5 to 735.The model accuracy of the system(modeling group data)reaches 93.12%,which represents accurate relationship between the input and output of the system.The closed-loop controller,designed according to the system model,is able to correct the static disturbance of different Zenike items or different intensities.Software demo can realize following functions:hardware connection,light intensity pre-optimization,system modeling,closed-loop control,visual display,etc.In this paper,the experimental platform of the adaptive optics system is designed and built,and the control algorithm of the deformable mirror is proposed,and engineering implementation is carried out.The main contribution of this paper can help to correct wavefront distortion of the laser beam in the wireless laser communication system deployed in the marine environment.The energy of the laser beam received by the communication terminal is increased,thereby improving the communication quality. |
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