Abstract

The benefits of aerial cables–modest installation cost, use of existing lines–are enhanced by the low weight and small diameter of fiber-optic cables with the optional surplus of a fully dielectric design. However, while conventional cable elements may tolerate strains of 1 %, optical fibers cannot. The present state of investigation does not allow long length fiber strain of more than 0.1 % in the long term. Former optimistic estimates of ≥0.5% generally have been reduced to ≤0.2%. Clear results in moist environments need giant efforts not yet made. As cable strains can reach or exceed 0.5%, practical cable designs are needed for not loading fibers in loaded cables. Alternative proposals of moisture impermeable jackets to make high fiber strains feasible are not realistic. Excluding weak fiber points by the proof test does not help unless fiber strain remains far below test strain, and the subsequent growth of remaining defects is slow enough to be safe. As fibers in stranded cables are never straight, they react to longitudinal forces by Irregular bends creating undesired changes in optical behavior.

© 1981 Optical Society of America