All-optical Ti:PPLN wavelength conversion modules for free-space optical transmission links in the mid-infrared

Data-format-independent all-optical transmitter and receiver modules for free-space optical communications in the 3.8 um region have been developed, essentially consisting of Ti-indiffused, periodically poled LiNbO3 waveguides. Using these modules, conversion of C-band radiation to/from the mid-infrared (MIR) via difference-frequency generation was demonstrated. More than 10 mW of MIR power could be generated with the transmitter unit; the internal low-power conversion efficiency was 69 % / W. A free-space MIR link was set up with a −41 dB fiber-to-fiber loss; only −15 dB are due to the parametric processes.