Double-Laser Differential Signaling for Reducing the Effect of Background Radiation in Free-Space Optical Systems

In order to reduce the impact of background radiation on the performance of terrestrial free-space optical systems, we propose to use two laser wavelengths and to perform the data detection at the receiver in a differential mode. We consider first the case of simple on-off keying modulation and show the performance improvement by using the proposed technique when the background noise dominates. We also extend our study to the case of pulse position modulation while proposing special signaling schemes that allow an increase in the data transmission rate at the same time as reducing the background noise effect.