Trellis coded modulation for multilevel photon communication system

The authors propose a new optical communication system called the multilevel photon communication system and clarifies the effect of combined coding and modulation. The multilevel optical communication system consists of a multilevel intensity modulator and photon counting receiver. They derive an upper bound on the error event probability for the trellis coded multilevel photon communication system. This bound shows that the distance between optical signal sequences may be considered as the Euclidean distance although the photon channel is not a Gaussian channel. The design the optical signal set for a four-level photon communication system so that the codes obtained by Ungerboeck for the additive white Gaussian noise (AWGN) channel become optimum. It is shown that coding gains of more than 4.6 dB over uncoded binary communication are attainable by using Ungerboeck´s codes. They also show that multidimensional trellis coded modulation employing multidimensional signals can yield significant coding gains without increasing the complexities of the codes