MANUFACTURE OF OPTICAL FIBER BUNDLE

PURPOSE:To increase the uniformity of a core diameter and to improve the quantity of light guidance by drawing a bundle of fibers which are arrayed by convergence in the state of the fiber bundle under specific set conditions. CONSTITUTION:Plural element wires of plastic optical fibers 1 each consisting of a core and a clad are charged in a plastic pipe 2 in the same axis direction to form a rod 3. Then the rod 3 is heated 6 above the thermal deformation temperature of the respective element wires and drawn, and the rod is cooled and solidified to obtain plural optical fibers which has thin core diameters. Core and clad materials in use are so selected that the clad materials are lower in viscosity than the core materials at the drawing temperature and Do-do>=(0.05do/dm)(dm+0.021) holds, where Do is the external diameter (mm) of the element wires, do is the core diameter (mm) of the element wires, and dm is the core diameter (mm) of the element wires after the drawing.