NSA tapping undersea fibers?

[Matt Crawford]

> To sum this whole thing up - /IS/ there a way to put a tap on a fiber line
> without letting the whole world know you're doing it, if not just the
> operator/owner of the line itself? And if so could someone sketch it out for
> me or point me to a resource? I'd love to learn of it

In an optical fiber, the light is constantly bouncing back and forth
off the sides of the glass.  (Actually, off the sides of the inner
region with the higher index of refraction.)  This is limits the
distance at which high-rate signals can be received even if power
loss is not a problem -- the bouncing spreads out one bit into the
next.

If you put another piece of suitably chosen glass up against the
first, some light will leak through.  If you've got a neurosurgeon's
fingers, you can increase the leakage by scraping the first fiber's
outer layer, but that's not at all necessary if you can provide local
amplification.



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