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.