Dead time effects in non-line-of-sight ultraviolet communications

By exploiting unique properties of the atmospheric propagation of radiation in the deep-ultraviolet band (200-300 nm), ultraviolet communications (UVC) offers the novel possibility of establishing non-line-of-sight (NLOS) optical links. UVC systems often employ photon-counting receivers, which may exhibit nonideal behavior owing to dead time, a period of time after the detection of a photon during which such a receiver is unable to detect subsequently impinging photons. In this paper, we extend a NLOS UVC channel model to account for dead time and then use this extended model to study the effects of dead time in representative system scenarios. Experimentally collected channel-sounding data is then used for model validation and real-world illustration of these effects. Finally, we investigate the effect of dead time on communication performance. The results demonstrate that dead time can have a significant impact in practical communication scenarios and suggest the usefulness of the proposed modeling framework in developing receiver designs that compensate for dead time effects. (C) 2015 Optical Society of America