Advances in Multi-Channel Mid-IR Free-Space Optical Communications

Free-space optical (FSO) communications in the mid-infrared (mid-IR) wavelength region has gained increasing interest due, in part, to the lower atmospheric loss than at lower wavelengths. In this paper, we review multi-channel mid-IR FSO communications using channel multiplexing to increase the system data capacity. We discuss different channel multiplexing schemes and channel degradation effects for mid-IR beam propagating through the atmosphere. Additionally, we review different techniques for mid-IR data transceivers in mid-IR FSO links. Finally, we describe several recent multi-channel mid-IR FSO link demonstrations resulting in increased total data rates.