Fabrication of large preforms for low-loss single-mode optical fibers by a hybridized process

Abstract

A hybridized fabrication process for single-mode optical fibers has been studied. The process consists of direct overcladding a VAD derived core rod with a porous body made from commercial silica powder by means of the cold isostatic pressing technique. By using a mixture of main silica powder with an average particle diameter of 10 µm and 1 w t% of fine silica powder with an average particle diameter of 0.04 µm and a core rod having a core/cladding diameter ratio of 1/2.4 as starting materials, large preforms for 300 km fibers were fabricated, which were drawn into fibers with attenuation losses of 0.350 dB/km at 1.31 µm and 0.232 dB/km at 1.55 µm. In the process, a special rubber mold with a structure in which both ends of the core rod are pressed by hydrostatic pressure makes the fabrication of large hybridized soot preforms possible, plastic deformation of the porous body during degreasing being remarkably reduced by using a suitable content of glycerol.