A Dielectric-Free Superconducting Coaxial Cable

We have investigated the theoretical properties of a dielectric-free superconducting coaxial cable with a magnetically levitated inner conductor. We found that at 100 GHz the intrinsic attenuation along such a cable is on the order of .1 dB per kilometer. Furthermore, for a given cable, the loss decreases with the square of the frequency. Thus, at 10GHz, on could expect losses on the order of 10 sup (-3) dB/km. This low loss coupled with a generous signal to noise ratio (~80db at 100GHz bandwidth) provide bit rates of 100Gbit/sec over 1000 kilometers. At 10Gbit/sec the distance increases to 10 sup 5 kilometers (more than 2.5 times the earth's circumference). Such a high-bandwidth extremely low-loss electronic transmission medium might be of interest for use in a distributed local area network and for very long distance repeaterless communications as well.