Re: super-fast freespace optics last-mile tech

From: Brian Atkins (
Date: Thu Mar 02 2000 - 16:29:00 MST

"Eliezer S. Yudkowsky" wrote:
> Brian Atkins wrote:
> >
> > Here you can read a patent app from a very secretive Seattle company:
> >
> >
> >
> > this looks to me like a very amazing advance in the speeds that people
> > will be able to access the net in the near future. Basically you slap
> > some of these lasers onto cell towers around a city and you get a super-
> > fast network (the cell towers can communicate with each other, so no
> > land lines needed) providing anywhere from 1.5mbit up to 10gbit to
> > individual users.
> I'm skeptical. The whole reason for fiber optic cables is that air,
> dust, water drops, et cetera scatter laser light beyond retrieval. I
> don't see any obvious way to get around that limitation; you'd have to
> use gamma-ray lasers, or neutrino lasers, or tachyon lasers, or such
> high-powered ordinary lasers that they'd punch through intervening
> airplanes as well as dust particles, and even then I'm not sure you
> could get 1MHz useful data out of it. If this company has invented a
> workaround, they *deserve* a 20-year patent. But I'll believe it when I
> see it.

Read the patent docs if you have time. The cell towers send the laser
light as diverging light-cones of various colored near-infrared light
that is then picked up by the customers using dishes that recover the
light (dishes about the size of those dbs satellite dishes). The dishes
can be indoors behind windows. The towers also sectorize the light
radially and vertically so that there are many different light cones
aimed at different areas, allowing a single cell to provide something
like 8 to maybe 20 terabit throughput total (assuming 8 different
wavelenghts of light used in each sector). This can easily provide
100mbit plus to everyone in a city if you slap it up on the existing
towers. They do mention that in heavy fog areas such as Seattle where
they developed it that you may have to reduce distances below the
normal 3 km range.

Actually this is already a proven technology in point to point
configurations, Lucent already has tested a product. This new stuff
provides point to multipoint.

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