Study on the Nature of Extrinsic Scattering Centers in Fluoride Glass Optical Fibers

Abstract

The origin and loss characteristics of extrinsic scattering centers in ZrF₄-based fluoride optical fibers have been investigated. Scattering centers larger than about 1 µm have been found to be micro-crystallites, inclusions of impurity particles or bubbles. They can be reduced by improving the preform-preparation conditions. For scattering centers of submicron size, scattering loss has been estimated at wavelengths of 0.633 and 2.55 µm and has been indicated to exhibit wavelength dependence of λ^-2. Loss factors for a fiber fabricated under improved preform-preparation conditions have been analyzed. A minimum loss of 3.0 dB/km at a wavelength of 2.55 µm was proved to arise from about 2 dB/km of scattering and about 1 dB/km of absorption.