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re: liquid light pipe
7 may 2001
m russon <> wrote:
>"ron herff" wrote:
>>a company named bominsolar is developing a daylighting system using a
>>fresnel lens and what they call a liquid light pipe of 4 cm in diameter.
>>they claim that the "pjpie" will transmit light up to 200 feet..
i wonder what they mean by "transmit." the fraction of incident solar
energy left after passing through l meters of water is approximately
0.36-0.08ln(l), eg 3% after 61 m (200'). full sun is 200x brighter than
a bright room (10k vs 50 footcandles), so the pipe might deliver 300 fc
in full sun, enough to light a 10 cm circle at 50 fc :-)
>...the "light tube' is most likely a flexible fiber optical cable with
>a reflective foil spiral wrap around it to hold light in over a longer
>distance. we used the same thing at my employment to carry network
>information over 900 feet.
long fast data links use very narrow fibers with total internal reflection.
no need for foil, but it's hard to launch much light into them. i designed
a 2 megabit 6 km ir led version with 3 db/km fusion-spliced fiber in 1984,
when att & ntt were sending gigabits over many kilometers using lasers.
nick
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