Group IV and III–V semiconductor photonic devices are prime candidates for photonic and opto-electronic (OEIC) applications in the 1.8 to 5.0 µm infrared wavelength range. Si-based active photonics in the GeSn/SiGeSn heterosystem (LDs, PDs, LEDs, amplifiers, EOMs) offers the Si CMOS “foundry advantage” for high-volume low-cost OEIC manufacture. Two MIR applications stand out: (1) deployment of GeSn SOI-based OEICs in a new “supplemental” global fiber-optic network at ∼ 2 um wavelengths; (2) creation/deployment of GeSn-related photonic chem-bio-physical sensor OEICs (as well as night-vision-imaging chips) in hand-held tablets and smart phones. The new smart sensors will be part of a local or global network-of-sensors utilizing the “internet of things.”