Lightguide preform fabrication

摘要

A lightguide preform (13) is fabricated by depositing and consolidating a plurality of doped silica layers (12), containing volatile germania, on the inside surface of a silica glass tube (11). The tube (11) is rotated while repeatedly traversing a hot zone therealong to shrink and collapse the tube in a final heat zone traversal. A gas mixture containing oxygen and germanium tetrachloride flow from an input gas line (23) and through the tube (11) during the shrinking traversals. The gas mixture continues to flow through at least a portion of the input gas line (23) during the final heat zone traversal.