Apparatus for coating optical fibers

Abstract

Vitreous optical fibers are useful in an expanding number of technologies. A process, corresponding apparatus, and a hermetically sealed fiber of the above nature are disclosed wherein high energy ionized plasmas are used in a continuous production of a coated vitreous optical fiber. Drawn fibers are axially aligned by ambient gases discharging through high vacuum gas locks. These fibers are then continuously fed through a high energy plasma zone so that the surface of the drawn fiber is subjected to ionized bombardment. This provides plasma-milling of the fiber surface for improving the fiber strength and for superior bonding of subsequently applied coatings. In preferred practice, a vacuum zone is used to deposit, from a plasma ion source, a diamond-like elemental carbon film onto the moving fiber. Another plasma vacuum zone may be used to deposit, over the carbon film, a very thin film of a conductive elemental metal illustratively; tin, indium and aluminum. To increase the thickness of the previously deposited metallized coating or film, the moving, pre-coated fiber is immersed in and passed through a more condensed molecular form of the metal used in the previous coating process. A molten liquid and/or vapor phase of the metal may be used in this latter process, although the former is preferred.