大气湍流扰动下的涡旋光束光通信理论及实验研究

涡旋光束携带的轨道角动量是光场的一个新的自由度，把轨道角动量的正交性用于光通信系统的模分复用中，可以大幅度提高通信容量和频谱利用率。多路携带轨道角动量的涡旋光束的复用/解复用在自由空间光通信中具有广阔的应用前景。本项目拟采用基于拓展惠更斯-菲涅尔原理和大气湍流理论，分析多路涡旋光束在湍流大气中传输时的光强分布、光强闪烁和光束漂移，探究涡旋光束的传输机理；基于大气湍流扰动使涡旋光束仅产生附加相位假设和基矢展开理论，探究涡旋光束在湍流大气中传输时轨道角动量谱的概率分布规律，构建大气湍流对轨道角动量谱的影响机制；基于大气湍流扰动产生的光强闪烁和光束漂移对信号误码率的影响，建立光束漂移、光强闪烁和信号误码率之间相互关系的理论模型；基于光学系统、信号系统和误码率测量系统等，探究建立理论模型的正确性。本项目的实施将为涡旋光束轨道角动量的复用/解复用在自由空间光通信中的应用提供理论和实验支持。

Orbital angular momentum (OAM) carried by the vortex beam is a new degree of freedom for the optical field. Mutually orthogonal property of the OAM states used in mode-division multiplexing of optical communication system can dramatically increase capacity and spectral efficiency. Multiple OAM states carried by the vortex beams multiplexing/demultiplexing in free space optical (FSO) communications have the broad application prospect. Based on the extended Huygens-Fresnel integral and theory of atmospheric turbulence, this project will investigate the intensity distribution, intensity scintillation and beam wander of the multiple vortex beams propagation through atmospheric turbulence and obtain the propagation mechanism of the vortex beams. Based on the assumption of the additional phase for the vortex beam generated by atmospheric turbulence perturbed and the expansion method of basis vectors, the probabilities for OAM spectra of vortex beam propagation through atmospheric turbulence are studied and influence mechanism of the OAM spectra disturbed by atmospheric turbulence are established. Based on the bit error rate (BER) of the signals influenced by the intensity scintillation and beam wander generated by atmospheric turbulence, the theoretical model of the relationship for the intensity scintillation, beam wander and BER of the signals are established. Based on optical system, signal system and BER of the signal measurement system etc., the correctness of the theoretical model will be verified. This project provides the theoretical and experimental support of OAM states carried by vortex beams multiplexing/demultiplexing used in free space optical communications.