Free space optical (FSO) communications are a potential application envisioned for
Quantum Cascade Lasers technology. In this paper, we sketch out the main market scenarii
for FSO communications, where data channels should reach up to Tbit/s over distances
that range from 0.1 to 36000 km. We analyze where QCLs can be relevant, and what standards
they must meet to be relevant at the industrial level. The following topics are discussed:
competing technologies, atmospheric transmission physics, signal processing and multiplexing.
We try and translate the constraints of the system-level into challenges for device-level
research and development.
