> maybe most commercial ones are, but there are also very (extremely) fats
> optical sensors and transmitters. Just imagine the speeds of fiber
> optics comms.

In project at work, I frequently run about 50kbsp synchronous through
the (reasonably-priced) optoes we use.  Pushing things to 250kpbs works
just fine with these optoes, but since the application gets no further
benefit, I prefer to keep the safety margin I get with the slower speeds
(at the faster speeds the signals look pretty mungey).  I don't know
off-hand what type of optoes we're using, but this is with what the parts-
selection guy regards as relatively "vanilla" optoes; the slightly more
expensive optoes can operate at 500kps with decent-looking waveforms.