A process includes the steps of disposing a solid core glass rod at a
point removed from hot temperature that can cause crystallization in the
core glass rod, disposing a solid clad glass rod at a point removed from
the core glass rod; softening to the flowing condition the solid clad
glass rod, transferring the softened clad glass to a lower point, the
softened clad glass having a central void therethrough, heating the
softened clad glass above its crystallization temperature, cooling the
softened clad glass to a draw temperature, transferring the solid core
glass rod into the central void in the softened glad glass, softening to
the flowing condition the solid core glass rod with the heat from the
softened and cooled clad glass, and drawing the core/clad, glass fiber by
allowing the clad and core glasses to flow in the form of a fiber.