Hybrid multiplexing and encoding/decoding based on the spatial coordinates and mode states of vector beams in free space

Abstract. Due to the characteristics of spatially inhomogeneous polarization and unlimited spatial coordinates, a concept of hybrid multiplexing and encoding/decoding based on spatial coordinates and mode states of vector beams is proposed for potentially enhancing the channel capacity and spectrum efficiency. For the sake of verifying the potentiality, a new encoding/decoding method by the mode states (i.e., polarization and mode) and spatial coordinates of vector beams is also proposed in this paper. In addition, the hybrid multiplexed vector beams are also utilized as carriers (16 channels) for transmitting data by four spatial coordinates and four mode states. In order to verify the feasibility of the proposed concepts, the relevant experimental setups are elaborated and established in this paper. Meanwhile, a fast mode recognition method based on the lookup table (LUT), image processing, and digital signal processing are employed to decode data when the hybrid vector beams propagate in free space (FS). The experimental results demonstrate that the encoded sequences (i.e., 0, 66, and D9) by the mode states and spatial coordinates can be successfully received and demodulated to the original data without errors after propagating 115 cm when the hybrid multiplexed vector beams are used for encoding/decoding. The total transmission rate of 320  Gbit  /  s can be acquired by combining the 16 channels (four mode states and four spatial coordinates) when the hybrid multiplexed vector beams are used as carriers. Furthermore, bit error rate, constellation diagrams (different transmission distance, transmitting data rate), and crosstalk among different channels or coordinates are employed to evaluate the propagation performances when the hybrid multiplexed vector beams are used as carriers.