Coding and decoding data by multiplexing vortex beams in free space

Abstract

A novel concept of coding/decoding data is proposed by multiplexing vortex beams for short-haul-free-space light communication. Eight vortex beams carrying different orbital angular momentum (OAM) modes (-5, 3, -2, 1, 5, -3, 2, -1) are employed to code the initial information sequences into each 256-ary symbols by different multiplexing approaches. A specially-designed Dammam vortex grating is utilized to decode the received vortex beams into the initial information sequences. In order to certifying the validity and feasibility of the proposed concept in practice, a proof-of-concept experiment is also proposed and established. The measured results demonstrate that a 128 × 128 gray-scale image (“Lena”) can be perfectly propagated over a 10 m free space by the proposed concept. In order to further evaluate the performance of the proposed concept, bit error rate (BER) against the received optical signal-to-noise ratio (OSNR) is also employed to analyzing the influences of some parameters on the system performances. The measured BER distributions demonstrate that the BER performance decreases as the data rate/propagation distance/atmosphere turbulence strength increases, respectively.