基于无波前探测的大气光通信自适应补偿方法研究
发布时间：2019-04-09 20:08
【摘要】：自由空间光通信(FSO)由于通信容量大、速率高、保密性强等优势成为通信领域的研究热点和前沿。FSO是以激光为载体在大气信道中进行信息的传递,因而会受到大气湍流的影响。为了减小大气湍流引起的通信性能的降低,开展大气湍流下FSO系统的自适应光学补偿方法研究,对FSO系统性能改善与提高具有理论意义和实用价值。本文在自适应光学原理、湍流中激光传输特性研究基础上开展了基于无波前探测的自适应光学原理对FSO系统通信性能的改善研究。探讨了无波前探测的自适应光学工作原理及系统模型,重点讨论了差分进化(DE)、随机并行梯度下降(SPGD)和模拟退火(SA)算法应用原理,通过对不同均方根相位的校正,验证了三种算法对畸变波前校正均具有良好的效果。分析了大气信道对激光传输特性的影响,利用Zernike多项式展开法和功率谱反演法产生了Kolmogorov谱下不同强度的大气湍流相位屏,并对经过湍流传输后的光束远场光强分布进行了仿真计算。由于无波前探测的自适应光学无需波前探测且不受光强闪烁效应的限制,将该原理应用于FSO系统对湍流引起的光束波前畸变进行补偿,数值模拟了基于DE、SPGD和SA算法的无波前探测自适应光学原理在FSO系统中的应用过程。分别讨论了DE、SPGD和SA算法中各参数对算法收敛速度及收敛极值的影响,根据校正后光束斯特列尔比的变化规律给出了参数合适的取值范围。将三种算法参数调至合适数值后,在得出不同湍流强度下无波前探测自适应光学应用前后接收端光功率基础上,对比分析了系统误码率及光强闪烁指数的变化。结果表明:基于三种优化算法的无波前探测自适应光学原理都可增加FSO系统接收端光功率,进而提高系统耦合效率及信噪比,在与理想光强比值为0.008的噪声环境下,系统误码率可降低至610?以下,但对由小尺度湍流引起的光强闪烁效应未能起到改善效果。通过对三种算法在运行速度、校正效果上进行比较,发现DE算法在强湍流下校正效果最优,但需要的迭代次数最多,在较强湍流影响下SA比SPGD算法校正效果好,所需迭代次数比SPGD算法多。因此在实际应用中,应综合系统在收敛速度、校正效果等方面的需求选择合适的算法进行性能优化。
[Abstract]:Free space optical communication (FSO) has become a research hotspot and frontier in the field of communication due to its advantages such as large communication capacity, high speed and strong confidentiality, etc. FSO is the transmission of information in the atmospheric channel using laser as the carrier. Therefore, it will be affected by atmospheric turbulence. In order to reduce the communication performance degradation caused by atmospheric turbulence, the study of adaptive optical compensation for FSO system under atmospheric turbulence is of theoretical significance and practical value for improving and improving the performance of FSO system. In this paper, based on the principle of adaptive optics and the study of laser propagation characteristics in turbulence, the improvement of communication performance of FSO system based on adaptive optics principle without wavefront detection is studied. The principle and system model of adaptive optics for wavefront detection are discussed. The application principles of differential evolution (DE), random parallel gradient descent (SPGD) and simulated annealing (SA) algorithm are discussed. The results show that the three algorithms have good effects on distortion wavefront correction. The influence of atmospheric channel on the propagation characteristics of laser is analyzed. The atmospheric turbulent phase screens with different intensity under the Kolmogorov spectrum are generated by using the Zernike polynomial expansion method and the power spectrum inversion method. The far-field intensity distribution of the beam after turbulent propagation is simulated. Because the adaptive optics without wavefront detection does not need wavefront detection and is not limited by the flicker effect of light intensity, the principle is applied to compensate the wavefront distortion caused by turbulence in FSO system, and the numerical simulation based on DE, is presented. The principle of adaptive optics without wavefront detection based on SPGD and SA algorithm and its application in FSO system. The effects of the parameters in DE,SPGD and SA algorithms on the convergence rate and convergence extremum of the algorithm are discussed, and the appropriate range of parameters is given according to the variation rule of beam Steeler's ratio after correction. After adjusting the parameters of the three algorithms to the appropriate values, the optical power at the receiver end before and after the application of adaptive optics without wavefront detection under different turbulence intensities is obtained, and the changes of the bit error rate (BER) and the intensity scintillation index of the system are compared and analyzed. The results show that the principle of adaptive optics without wavefront detection based on the three optimization algorithms can increase the optical power at the receiving end of the FSO system, and then improve the coupling efficiency and the signal-to-noise ratio of the system. In the noise environment with a ratio of 0.008 to the ideal light intensity, the optical output of the system is improved. Can the BER of the system be reduced to 610? Below, the effect of light intensity scintillation caused by small-scale turbulence has not been improved. By comparing the operation speed and correction effect of the three algorithms, it is found that the DE algorithm has the best correction effect under strong turbulence, but it needs the most iterations. Under the strong turbulence influence, SA is better than the SPGD algorithm in the correction effect, and the correction effect of the SA algorithm is better than that of the SPGD algorithm under the influence of strong turbulence. The number of iterations required is more than that of SPGD algorithm. Therefore, in practical application, it is necessary to select the appropriate algorithm to optimize the performance of the system in terms of convergence rate, correction effect and so on.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.1
本文编号：2455496
[Abstract]:Free space optical communication (FSO) has become a research hotspot and frontier in the field of communication due to its advantages such as large communication capacity, high speed and strong confidentiality, etc. FSO is the transmission of information in the atmospheric channel using laser as the carrier. Therefore, it will be affected by atmospheric turbulence. In order to reduce the communication performance degradation caused by atmospheric turbulence, the study of adaptive optical compensation for FSO system under atmospheric turbulence is of theoretical significance and practical value for improving and improving the performance of FSO system. In this paper, based on the principle of adaptive optics and the study of laser propagation characteristics in turbulence, the improvement of communication performance of FSO system based on adaptive optics principle without wavefront detection is studied. The principle and system model of adaptive optics for wavefront detection are discussed. The application principles of differential evolution (DE), random parallel gradient descent (SPGD) and simulated annealing (SA) algorithm are discussed. The results show that the three algorithms have good effects on distortion wavefront correction. The influence of atmospheric channel on the propagation characteristics of laser is analyzed. The atmospheric turbulent phase screens with different intensity under the Kolmogorov spectrum are generated by using the Zernike polynomial expansion method and the power spectrum inversion method. The far-field intensity distribution of the beam after turbulent propagation is simulated. Because the adaptive optics without wavefront detection does not need wavefront detection and is not limited by the flicker effect of light intensity, the principle is applied to compensate the wavefront distortion caused by turbulence in FSO system, and the numerical simulation based on DE, is presented. The principle of adaptive optics without wavefront detection based on SPGD and SA algorithm and its application in FSO system. The effects of the parameters in DE,SPGD and SA algorithms on the convergence rate and convergence extremum of the algorithm are discussed, and the appropriate range of parameters is given according to the variation rule of beam Steeler's ratio after correction. After adjusting the parameters of the three algorithms to the appropriate values, the optical power at the receiver end before and after the application of adaptive optics without wavefront detection under different turbulence intensities is obtained, and the changes of the bit error rate (BER) and the intensity scintillation index of the system are compared and analyzed. The results show that the principle of adaptive optics without wavefront detection based on the three optimization algorithms can increase the optical power at the receiving end of the FSO system, and then improve the coupling efficiency and the signal-to-noise ratio of the system. In the noise environment with a ratio of 0.008 to the ideal light intensity, the optical output of the system is improved. Can the BER of the system be reduced to 610? Below, the effect of light intensity scintillation caused by small-scale turbulence has not been improved. By comparing the operation speed and correction effect of the three algorithms, it is found that the DE algorithm has the best correction effect under strong turbulence, but it needs the most iterations. Under the strong turbulence influence, SA is better than the SPGD algorithm in the correction effect, and the correction effect of the SA algorithm is better than that of the SPGD algorithm under the influence of strong turbulence. The number of iterations required is more than that of SPGD algorithm. Therefore, in practical application, it is necessary to select the appropriate algorithm to optimize the performance of the system in terms of convergence rate, correction effect and so on.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.1
【参考文献】
相关期刊论文 前1条
1 张建柱;张飞舟;吴毅;;大气湍流随机相屏模拟方法研究[J];强激光与粒子束;2012年10期
，本文编号：2455496
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