White-light spectral interferometry to measure intermodal dispersion in two-mode elliptical-core optical fibres

White-light spectral interferometric technique employing a low-resolution spectrometer is used to measure intermodal dispersion for LP01x and LP11x, modes of elliptical-core optical fibres in the spectral range approximately from 540 to 870 nm. The technique utilizes a tandem configuration of a Michelson interferometer and an optical fibre to measure the equalization wavelengths as a function of the optical path difference (OPD) between beams of the interferometer, or equivalently, the wavelength dependence of the intermodal group OPD in the optical fibre. A polynomial fit applied to the measured data gives the wavelength dependence of the difference between propagation constants of modes with 2pi ambiguity. The wavelength dependences of both the difference between propagation constants of modes and the intermodal group OPDs obtained are used to compare the theoretical spectral interferograms with the recorded ones and to confirm good agreement between theory and experiment. (C) 2003 Elsevier Science B.V. All rights reserved.