Methods of forming an overclad portion of an optical fiber are described which include positioning a core cane member in an overclad tube to form a rod and tube assembly. Thereafter, glass soot pellets are positioned in the rod and tube assembly between the core cane member and an interior sidewall of the overclad tube. The rod and tube assembly is then redrawn under conditions effective to form the overclad tube and the glass soot pellets into a continuous, void-free glass layer surrounding the core cane member at a sintering time tsinter of at least 1800 seconds thereby forming an overclad portion of an optical fiber.