Modulation Schemes for Long Distance Optical Communication

This article presents a comparison of modulation techniques applicable to deep-space optical communication. We assume a gamma-gamma distributed signal at the near-earth phase of long-range links, which can be correctly used in the case of strong, moderate and weak turbulent media. Our article details the differences between short and long distance optical transmission. As a result, the modulation technique with high bandwidth and power efficiency is required. Accordingly, two intensity modulation schemes are analyzed, one is the well-known on-off keying, and the other is a specific pulse position modulation. In our article, we analyze the conditions under which these modulation techniques can apply.