Material Structure of Germanium-Doped Optical Fibers and Preforms

Abstract

The structural characteristics of preforms and optical fibers fabricated by modified chemical vapor deposition were studied by optical, interference, and scanning electron microscopy. It was observed that the structural features resulting from the deposition process are preserved through subsequent processing and appear in the fiber with the exception of a region at the center of the fiber. Here, selective evaporation of dopant material from the inner surface of the deposit results in a refractive index depression on the axis of the optical waveguide.