Natural Science Forum / Physics / Optics / October 2004

Just as a side note on this topic, I attended a seminar on the Terabeam
point-to-point laser communications system a couple of years ago.   If a
Terabeam system is set up between upper floor windows in two office
buildings the tip-tilt (or pointing and tracking) system has to respond
to significant thermally induced building tilts as the sun comes up or
the day warms up, along with seismic events, traffic vibrations, tidal
forces near coastlines, and the like.

At the same time the control electronics also adjusts the transmitted
power and/or the receiver sensitivity to compensate for transmission
variations due to fog, clouds, or atmospheric pollution.

If the communications link is being used to transmit Internet traffic,
the units at both ends of the link are actually also on the Internet and
in continuous communication with Terabeam's home office, and all the
control signals involved in these active control systems are sent back
to Terabeam's home office and logged in real time.

In other words every Terabeam system functions not only as a
communications link, but also as a fairly sophisticated real-time
seismological and meteorological data collecting system, with all of the
data from Terabeam links all over the world being collected at Terabeam
headquarters.

I spoke with the speaker about this after the seminar.  He said that no
scientific workers were actually using this data (not at that time
anyway), but that Terabeam actually had seismologist and meteorological  
types on its staff who used this data to help design and improve their
systems.