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Sat Jul 28 17:17:45 EDT 2007

the backscatter, correlating time-of-flight with the Raman-scattering lines
(Stokes and anti-Stokes).  One of those spectral lines is
temperature-dependent while the other isn't, so by recording the separation,
they end up with is a graph of temperature versus distance along the fiber,
gathering up to a few kilometers' worth of data with what looked like
sub-meter resolution.

No doubt this effect is old hat to physicists on the list, but I'd never
heard how it worked before.  So if you buried a fiber like this, you'd
presumably get a great picture of what happens with temperature at various
depths.  Plotting the temperature-versus-distance on a waterfall display
gives a nice diurnal picture.  The article used it to study water
temperature along the course of a stream, but you could think of plenty of
other uses for 2D remote temperature sensing.

-- john, KE5FX

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