Home – Home – Jornals – Atmospheric and Oceanic Optics 2025 number 8

A new method for wireless byte-by-byte optical transmission of a digital signal multiplexed by the value of orbital angular momentum (OAM) of electromagnetic wave is presented. The transmitter is a round array of coherent laser beams formed by splitting original narrow-band laser radiation into eight channels. Data transmission channels with different OAM values are formed through interference combining of eight coherent laser beams in the far diffraction zone. The amplitude and phase of these beams vary proportionally to the values of Fourier images of information signals coming from the programmable controller to the amplitude and phase modulators of the round array of laser beams. The wave field propagates in space and comes at the input of the receiving telescope. To demultiplex the signal, the sorter of OAM modes is used. It comprises beam splitters, vortex phase plates, focusing lenses, photodetectors, and a comparator. The sorter distributes the incoming radiation into eight channels, which differ in the OAM values in the range from -3 to +4. Upon the processing, the structure of a digital signal byte is reconstructed at the vortex phase plates at the photodetectors inputs. The combining of eight laser beams in the comparator yields the complete structure of the transmitted digital signal. A conceptual diagram of an experimental setup implementing this method is proposed. The possibility of its practical implementation is demonstrated through numerical simulation. Some technical methods improving the efficiency of the method are suggested, and the advantages of the method are described.