Abstract

Hermetic coatings are known to significantly reduce the static fatigue of optical fibers.^(1–6) Thus one would also expect to see a significant increase in strength of these fibers to the leve1 of the inert strength (measured in vacuum or at ℓN₂) i.e., 12-18 GPa. In fact such strengths have recently been achieved by coating with a variety of metals.(⁵) On the other hand, the strength of carbon coated fibers, which are the most widely used today, is 3.5 to 4.5 GPa.^(3,4) While a correlation has recently been found between the roughness of the carbon coating and the fiber strength,⁽⁶⁾ a detailed understanding of the strength of these fibers has not been achieved. A reasonable model is that the carbon fails first and allows access of the atmosphere to the silica surface. In order to confirm this supposition and to improve the strength of carbon-coated fibers, we have developed a technology for the fabrication of dual hermetically coated (DHC) fibers: a primary coating of CVD carbon and a secondary melt coating of a metal.

© 1992 Optical Society of America