| 摘要 |
<p>A cylindrical optical waveguide soot preform of the kind having a cylindrical center hole is described, the center hole being surrounded by a core portion made up of a plurality of vitreous soot layers and the inner core layers adjacent the center hole being subject to tensile stress. In the inventive preform at least the innermost core layer is replaced by a soot layer having a relatively low expansion coefficient with respect to at least one of the succeeding layers, in order to reduce the tensile stress at the center hole. A method for making the preform is also described.</p> |
