Over the past two years, high-strength metal-jacketed lightguides have been developed with static-fatigue lifetimes orders of magnitude longer than those of conventional plastic-coated fibers. The advantage of the metal jacket is that it provides a hermetic seal that protects the surface of the glass from moisture, which is an essential ingredient for the delayed-failure phenomenon known as static fatigue. Although the metal-jacketed fibers have better mechanical characteristics than the plastic-coated fibers, their optical transmission losses tend to be somewhat higher. This is due to higher microbending losses associated with the metal jacketing, which is substantially less pliant than typical plastic coatings. The soft plastic tends to cushion the fibers from microbends. We have studied the problem of excess loss in metal-coated fibers of varying geometry and have found that the excess loss can be reduced to acceptable values.
© 1979 Optical Society of AmericaPDF Article