涡旋光束可以有效提高通信系统的信道容量,但大气环境下光通信信道受大气湍流的影响,因此研究涡旋光束大气湍流传输特性具有重要意义。大气湍流广泛采用Kolmogorov谱模型进行描述,但对大气湍流的进一步研究表明,大气湍流还具有非Kolmogorov谱特征。开展了非Kolmogorov谱湍流下涡旋光束传输特性的研究,基于数值方法研究了湍流内外尺度、广义指数因子、折射率结构常数对拉盖尔-高斯光束在不同传输距离下的螺旋谱分布、拓扑荷探测概率等参量的影响,仿真结果表明,拓扑荷探测概率与以上参量密切相关。最后,提出了一种数值计算涡旋光束闪烁指数的方法,并据此计算分析了大气湍流对通信误码率的影响。结果表明,即使在弱湍流中传输至1000 m处,误码率也很难达到通信要求,因此有必要采取进一步的相位校正措施。

A vortex beam can effectively improve the channel capacity of the communication system, however in the atmospheric environment, the optical communication channel is influenced obviously by the atmospheric turbulence. Thus it is of great significance to study the transmission characteristics of a vortex beam in the atmospheric turbulence. The Kolmogorov spectral model is widely used to describe the atmospheric turbulence previously, but the further researches show that the atmospheric turbulence also has the non-Kolmogorov spectral characteristics. Therefore, the investigation of the non-Kolmogorov spectral transmission characteristics for a vortex beam is conducted. Based on the numerical methods, the influence of outer- and inner-scale of turbulence, generalized exponential factor, refractive-index structure constant on the spiral spectral distributions, topological detection probabilities and others of a Laguerre-Gaussian beam after different transmission distances is investigated. The simulation results show that the topological detection probability is closely related with the above parameters. Finally, a numerical method for calculating the scintillation index is proposed, and the influence of turbulence on bit-error-rate (BER) is figured out. The results show that when the beam is propagated up to 1000 m even in a weak turbulence, the BER is still difficult to meet the communication requirements, and thus a further phase correction is quite necessary.