The major limitation on fiber optic cable is the distance. The signal rapidly degrades on standard fiber optics, either being absorbed into the fiber or escaping from the fiber. This requires expensive boosters to keep the signal strong.

Recently a couple of different groups (using different technologies) have been able to create hollow fiber optic cables that can send data hundreds of miles with almost no detectable degredation of data.

The problem with hollow tubes is that to reflect light the outside must have a lower refraction index than the interior, and almost nothing has a lower index than air (a vacum has an index of 0). Mirrors absorb almost 60% of the light and thus would not work well either. One method used is to surround the hollow part with a honeycomb-like structure with holes that are too small for the light to go through. The light is then unable to escape the tube. Such a method even allows for the tube to have a vacum in it, which would further reduce signal degredation.

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