White-light spectral interferometry used for dispersion characterization of optical fibers

A new spectral-domain white-light interferometric technique employing a low-resolution spectrometer is used for dispersion characterization of optical fibers. The technique utilizes the fact that the spectral interference fringes are resolved at the output of a tandem configuration of the compensated (non-dispersive) Michelson interferometer and a two-mode optical fiber only in the vicinities of so-called equalization wavelengths at which the optical path difference (OPD) in the interferometer is the same as the intermodal group OPDs. Processing of these interference fringes in case of a two-mode optical fiber and measuring the OPD adjusted in the interferometer as a function of the equalization wavelength serve for dispersion characterization including the spectral dependence of both the difference between propagation constants of modes and the intermodal group OPD in the optical fiber. The white-light spectral interferometric technique is used for both circular-core and elliptical-core (highly birefringent) optical fibers. The measured dispersion characteristics of the optical fibers are compared with those corresponding to the results of an adequate theoretical analysis using the known parameters of the optical fibers.