Optical communication offers several advantages over the presently used
microwave links. Most obviously, the higher carrier frequencies allow
higher modulation rates. Additionally, the shorter wavelengths spread the
transmitted power over a smaller area for reception after hundreds of
millions of kilometres of travel, providing an efficiency gain. The
situation is analogous to the proliferation of optical fibre network links
due to their superiority over coaxial copper cables.
The system envisioned would involve a communications relay satellite
in Martian orbit, with UHF receivers collecting data from local exploration
platforms, and a laser transmitter providing a high data rate to receivers
on or near Earth. Various technological approaches for the development of
such a laser system can be conceived. In all such concepts, a laser
transmitter, large aperture telescopes, and low-noise high-speed detectors
are common elements.
Preliminary analysis shows 108 b/s rates to be sensible aims,
for a system deployed on a 10 to 20 year timescale, but the expectation is
the use of scalable technologies allowing a system to be scaled up as need
and capability grow into the further future.
Such a system is clearly operationally in the order of two decades away,
however the technologies required need to be developed to be strategically
available when required.