Structural analysis of optical fiber preforms using Raman microprobe.

We have investigated the incorporation of aluminum and phosphorus into vitreous silica using a Raman microprobe. By studying bulk glasses of varying Al/P ratio we have identified the presence of different structural units in the glass and used these to analyze radially their distribution in optical fiber performs. Our analysis has shown the coexistance of P=O and AlPO sub 4-like structures in glasses rich in phosphorus, as well as giving evidence for both phosphorus and aluminum diffusion in optical fiber performs prepared by MCVD.