Between the 1930s and the 1970s, Bell Labs had a substantial research
program [8] aimed at developing a hollow-core waveguide to transport micro-
wave (GHz) electromagnetic signals for long-distance communications. It devel-
oped a 60-mm-diameter hollow-core tube, the inside of which was coated with
copper. The range of operational frequencies was aimed to be 40–110 GHz, with
losses less than 1 dB/km. Interestingly enough, one of the major obstacles that
precluded it from deploying the cable was economic; the price of deployment was
substantial, so only deployment for large markets could pay off, yet there were
very few markets at the time that could make anywhere close to the full use of the
274-Mbps capacity of such a cable. In the 1970s, Corning ...