Hyperspectral optical fiber refractive index measurement spanning 2.5 octaves

Optical fiber refractive index profiles were measured across a 2.5 octave wavelength range (from 375 nm to 2100 nm) using a single phase-shifting interferometer. This spectral range is more than a factor of 2 larger than previously reported multi-wavelength interferometers, and includes the pump and amplification bands of Er-doped, Yb-doped, Er: Yb-doped, and Tm-doped fibers. The apparatus can measure the material dispersion in a spatially-resolved manner that permits more accurate prediction of the fiber's waveguide properties. The measurement wavelength can be tailored to optimize the beneficial or deleterious effects of material dispersion, optical resolution, and interferometric phase ambiguities.