MANUFACTURE OF MULTICORE FIBER PREFORM

PURPOSE:To improve the sphericity of a core after spinning by closely arranging perform rods in a sheath pipe and by making the pipe solid by heating after packing spacer rods in gaps. CONSTITUTION:In a sheath pipe 1, preform rods 4 are arranged closely and in gaps, spacer rods 5 and 6 are packed. materials of the spacer rods 5 and 6 have softening points, coefficients of thermal expansion, and mechanical strength nearly equal to those of the sheath pipe 1 and preform rods 4. One terminal of the sheath pipe 1 is sealed and while discharge of air is carried out from the other terminal, the entire body is heated to manufacture a solid preform having no gap. Consequently, the sphericity of each core 2 after spinning is improved.