The variation of the core-cladding refractive index difference Δn(λ) is determined as a function of wavelength for GeO2-SiO2, B2O3-SiO2, TiO2-SiO2, P2O5-SiO2, Al2O3-SiO2, and Cs2O-SiO2 optical fibers. The measurements are obtained by electronically processing the output of an interference microscope illuminated by a monochromatic light source variable over the 0.5–1.1-µm range. The Δn(λ) results are utilized to calculate the precise grading of the refractive index profile characterized by an exponent α(λ) required to achieve a minimum modal dispersion. The material dispersion for these compositions is also calculated with the aid of available n(λ) data for SiO2.
H. M. Presby and I. P. Kaminow, "Binary silica optical fibers: refractive index and profile dispersion measurements," Appl. Opt. 15, 3029-3036 (1976)