A concept of noncoaxially propagating discrete data by coding/decoding orbital angular momentum (OAM) of vortex beam through multiple channels is proposed. Four independent channels along different directions (diffraction orders/angles) are established by a series of specially designed holograms. Sixteen vortex beams are used to code each sequence with the length of 4 bits into an OAM mode in each channel. The theoretical analysis (simulation) demonstrates that the proposed scheme is reliable. In addition, an experiment is also designed and performed for practically certifying the feasibility of the proposed scheme. A 16-bits-length sequence, which is coded into four OAM modes in four channels (one channel with one OAM mode), is successfully received/decoded by observing the intensity-profile arrays (OAM-mode spectrum) generated by a specially designed Dammann vortex grating. The measured results show that the proposed concept is also viable in practice. Moreover, the received/recovered images indicate that the performance of the system decreases as the atmosphere turbulence strength increases when a color image and a gray-scale image are simultaneously propagated. Besides, the measured bit error rate (BER) gradually decreases with the increase of bit rate or propagation distance. The acceptable BER under the threshold of forward error correct can be achieved for a short-distance communication network.

中文翻译：

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通过编码/解码涡旋光束通过多个通道的轨道角动量非同轴传播离散数据

提出了一种通过多通道对涡旋光束的轨道角动量（OAM）进行编码/解码来非同轴地传播离散数据的概念。一系列特殊设计的全息图建立了沿不同方向（衍射阶次/角度）的四个独立通道。16个涡旋光束用于将每个4位长度的序列编码为每个通道中的OAM模式。理论分析（仿真）表明，该方案是可靠的。此外，还设计并进行了一项实验，以实际证明所提出方案的可行性。16位长度的序列，被编码为四个通道中的四个OAM模式（一个通道带有一个OAM模式），通过观察由特殊设计的达曼涡旋光栅产生的强度分布阵列（OAM模式频谱），可以成功接收/解码信号。测量结果表明，所提出的概念在实践中也是可行的。而且，当同时传播彩色图像和灰度图像时，接收/恢复的图像指示系统的性能随着大气湍流强度的增加而降低。此外，随着比特率或传播距离的增加，测得的误码率（BER）逐渐降低。对于短距离通信网络，可以在前向纠错阈值以下获得可接受的BER。接收/恢复的图像表示当同时传播彩色图像和灰度图像时，系统的性能会随着大气湍流强度的增加而降低。此外，随着比特率或传播距离的增加，测得的误码率（BER）逐渐降低。对于短距离通信网络，可以在前向纠错阈值以下获得可接受的BER。接收/恢复的图像表示当同时传播彩色图像和灰度图像时，系统的性能会随着大气湍流强度的增加而降低。此外，随着比特率或传播距离的增加，测得的误码率（BER）逐渐降低。对于短距离通信网络，可以在前向纠错阈值以下获得可接受的BER。