Fig. 1: Concept for the mid-infrared (IR) wavelength-division-multiplexing (WDM) and orbital angular momentum (OAM)-based mode-division-multiplexing (MDM) free-space optical (FSO) communication system. | Nature Communications

Fig. 1: Concept for the mid-infrared (IR) wavelength-division-multiplexing (WDM) and orbital angular momentum (OAM)-based mode-division-multiplexing (MDM) free-space optical (FSO) communication system.

From: High-capacity free-space optical communications using wavelength- and mode-division-multiplexing in the mid-infrared region

Fig. 1: Concept for the mid-infrared (IR) wavelength-division-multiplexing (WDM) and orbital angular momentum (OAM)-based mode-division-multiplexing (MDM) free-space optical (FSO) communication system.The alternative text for this image may have been generated using AI.

Mid-IR WDM signals are generated by wavelength converting C-band signals using the difference-frequency generation (DFG) process, and detected at the C-band after being converted via another DFG process. Mid-IR OAM beams are generated by passing mid-IR Gaussian beams through spiral phase plates (SPPs), and converted back to Gaussian beams using SPPs of inverse orders.

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