| Popis: |
Optical communications systems using pulsed optical modulations and photon-counting receivers have been demonstrated to be capable of very high photon efficiencies. The basic trade is to achieve high photon efficiency by using more bandwidth along with higher ratios of peak-to-average transmitted power. We investigate here the efficiency a photon-counting receiver could achieve in the lower bandwidth regime. It is well known that the best efficiencies at high bandwidths are achieved using two-level pulsed signaling. We will show that it is possible to achieve medium efficiencies at somewhat reduced bandwidth if the pulses are allowed to have more than one level. Equivalently, we show that at fixed slot rates, it is possible to more than double the data rates achievable by a photon-counted, pulsed optical system, although at somewhat decreased photon efficiency. |
