Toward the Deployment of Mid-IR Gb/s FSO Links: Laboratory Validation of a Packaged DFG-SFG Transceiver

We report laboratory validation of a compact mid-infrared free space optical (FSO) transceiver based on packaged intracavity difference frequency generation (DFG) module at the transmitter and sum frequency generation (SFG) unit at the receiver. A 1 Gb/s nonreturn-to-zero (NRZ) signal directly modulate C-band DFB laser is wavelength-converted to the mid-IR via DFG, propagated through free space, and subsequently upconverted by SFG, enabling compatibility with ground-station receiver architectures. The recovered signal is detected via a silicon compatible avalanche photodetector. Eye diagrams and bit error rate (BER) measurements as a function of output amplitude are presented. These experiments lay foundation for deployable mid-IR FSO links.