Infrared optical properties of highly P doped silica fibres: a spectroscopic study

The infrared properties of silica fibre and preform samples doped with up to about 10 wt% phosphorus concentration have been studied. By combining cutback attenuation measurements, FTIR spectroscopy and Raman spectroscopy, wavelengths from 0.9-8 mu m were investigated. Fundamental and first overtone absorption bands of P=O were observed around 7.55 and 3.78 mu m, as predicted by the literature.((1.2)) Additional absorption bands located near 2.53, 1.92 and 1.56 mu m were observed and were identified as the second, third and fourth overtones of P=O stretching, respectively. Further experimental studies of these P=O bands confirmed the proposed identification and showed (a) their resistance to gamma-radiation and (b) their resistance to hydrogen exposure.