Silica based binary glass systems — refractive index behaviour and composition in optical fibres

Refractive index versus composition data are presented for three silica based binary glass systems SiO₂-B₂O₃, SiO₂-P₂O₅ and SiO₂-GeO₂. Using a near-field scanning method refractive index measurements were made on graded-index optical fibres, of known composition, fabricated by the chemical vapour deposition technique. The experimental data for each glass system is also compared with theoretical predictions of refractive index versus composition made from a single oscillator, Sellmeier model involving an oscillator energy and a dispersion energy term.