> Does the light signal in an fibre optic cable get noisy over distance? Yes. > If so, then wouldn't an analog signal amp such as this simply amplify the nois

> Does the light signal in an fibre optic cable get noisy over distance? Yes. > If so, then wouldn't an analog signal amp such as this simply amplify the noise along with the signal? Yes. That's why there are limits on the reach of amplified networks. > Decoding and re-encoding would have the effect of 'cleaning' the signal in this case. Yes, but regenerating the signal introduces complexity, and thus reduces reliability, adds latency and only works for a specific encoding, which makes upgrades impossible. None of these things are wanted at the bottom of the sea for the next 25 years. > If it does get noisy, where does the noise come from? There are lots of noise sources. See: http://www.svphotonics.com/pub/pub029.pdf http://www.svphotonics.com/pub/pub029.pdf > The medium? Yes, partly. > Leakage from outside the cable? No. Although vibrations can cause noise.