High-dimensional vortex beam encoding/decoding for high-speed free-space optical communication

The development of communication technologies has led to an ever-increasing demand for higher dimension and higher speed of optical coding technology. The orbital angular momentum (OAM) of vortex beams provides a new degree of freedom for optical coding in recent years. In this paper, we propose a novel high-dimensional vortex beam encoding/decoding scheme for high-speed free-space communication. An off-axis 4f-configuration with a digital micromirror device (DMD) and a MIP-based pattern formation algorithm are employed to generate fast switchable, accurate vortex beams (arrays) that can be used for encoding. Interference is introduced to efficiently decode data information. We experimentally demonstrate a high-quality communication link based on 64-ary vortex beam encoding/decoding and zero bit error rate is observed, which shows the validity of the proposed high-dimensional scheme. Owing to enhancement of encoding dimension and employment of high-speed DMDs, the proposed scheme enjoys a higher transfer rate exceeding other communication technologies. What is more, the data transfer rate can be further improved by introducing vortex arrays, which is demonstrated by the rapid transmission of a 24-bit true color bitmap.