Oxide impurity absorptions in Ge-Se-Te glass fibres

Oxide impurity absorptions in Ge-Se-Te glass fibres and the cause of the absorption loss around 943 cm^–1, the frequency of the CO² laser, have been investigated. The oxygen in the glass bounds preferentially to germanium and causes the absorptions due to Ge-O bond vibrations at 765 cm^–1 (band I) and 1230cm^–1 (band II). The excess absorptions due to these bands were determined as 0.228cm^–1/P.p.m. wt O₂ for band-I and 0.006cm^–1 /p.p.m. wt O₂ for band II. The loss of the fibre at 943cm^–1 increased with the oxygen content. It was, however, revealed from the deconvolution of the IR spectra into the independent absorption components that the absorption tails of band I and band II did not affect the loss at 943 cm^–1. The content of the impurities except oxygen analysed by a mass spectroscopy was too low to affect the loss at 943 cm^–1.