| 摘要 |
PURPOSE:To produce the optical fiber preform of a long size and large diameter at a high yield at the time of production without causing large eccentricity between a core and a clad and without requiring a particular surface treatment by using a heating furnace of a vertical type in a rod-in tube method. CONSTITUTION:A glass rod 1 previously formed with clad glass in a part of the circumference of core glass is prepd. and thereafter, the glass rod 1 is inserted into a glass tube 4 for the clad. The vertical heating furnace 8 is used and while the furnace is subjected to vacuum evacuation, the glass rod is moved from above to below in a perpendicular direction and is drawn under heating and melting, by the stretching of which the glass rod 1 and the glass tube 4 are fused and integrated and the optical fiber preform 12 is obtd. |
