| 摘要 |
PURPOSE:To obtain the titled long preform having low scattering, OH content and loss, by casting a core and a clad glass melts from a crucible of specific double structure into a mold, and solidifying the melts. CONSTITUTION:Core and clad fluoride glass raw materials are charged into melting parts 1 and 2 of a crucible of double structure having a melt outflow preventing wall 5, and a lid is placed thereon. The raw materials are heated at about 400 deg.C for about 1hr and then about 900 deg.C for about 2hr and melted to give core and clad glass melts, which are then cast through a core melt and clad melt casting nozzles 3 and 4 into a brass mold 6 having the gilded interior of the hollow part, dividable into three parts in the longitudinal direction and integrated with a ring 7 and bottom ring 8 at about 260 deg.C to solidify a core melt 9 and clad melt 10. Thus, the rings 7 and 8 are removed to take out the aimed preform. |
