Orbital angular momentum beamforming techniques for indoor multiuser optical wireless communications

Abstract

The orthogonality characteristics of orbital angular momentum (OAM) can provide a new degree of freedom for optical wireless communication (OWC) systems. By transmitting multiple different orders of OAM states within a single beam, multiple data channels can be carried to the end users simultaneously. As the value of the OAM state increases to a higher order, the conventional single OAM state beam suffers from destructive interference due to decreasing intensity and increasing divergence angle as the beam spreads out. In this paper, we propose a novel OAM beamforming technique for an indoor multiuser OWC network using weighted impulse response, based on the sum of intensity contributions of superposed multiple OAM states carrying Laguerre-Gaussian (LG) ultraviolet (UV) beams. The proposed OAM beamforming method is shown to reduce the destructive interference at the dark region of the beam and to increase the amplitude of intensity distribution of the beamformed OAM states. Consequently, the proposed method shows better performance with increasing OAM states beamformed together in the OWC channel, compared to a conventional single OAM state LG UV beam.