JPS5673642A - Manufacture of optical fiber - Google Patents

Abstract

PURPOSE:To manufacture an optical fiber while easily controlling the core to outside diameter ratio by introducing core forming material glass and clad forming material glass into a multiple crucible, melting them, and carrying out spinning while pressurizing the higher viscosity side glass. CONSTITUTION:Core forming glass rod 1 is put into melting crucible 2, clad forming glass rod 3 into melting crucible 4, and rods 1, 3 are melted by heating with heating furnace 5A. Core glass 9 is fed into spinning crucible 6 through U-shaped conduit 7. Clad glass 10 is introduced into the 2nd chamber 13 through central conduit 14 of partition plate 11 of the 1st chamber 12 of crucible 4, and it is fed into crucible 6 through U-shaped conduit 7 while being pressurized by oxygen gas supplied from gas introducing pipe 15. Glass 9 and glass 10 are then heated with heating furnace 5B and spun to obtain an optical fiber. This fiber is irradiated with laser beams, and on the basis of the pattern of the reflected beams the core to outside diameter ratio is detected to control the pressure of oxygen gas supplied to chamber 13. Thus, the core to outside diameter ratio is controlled.