Differential Group Index Dispersion of a Holey Fiber Measured by White-Light Spectral Interferometry

We present a new white-light interferometric method to measure the differential group index dispersion of a pure-silica holey fiber. The method is based on the recording a series of the spectral interferograms in an unbalanced Mach-Zehnder interferometer with the fiber of known length placed in one of the interferometer arms and the other arm with adjustable path length. We measure the equalization wavelength as a function of the path length difference, or equivalently the group index dispersion. Subtracting the group dispersion of the optical components present in the interferometer along with the fiber, we measure the wavelength dependence of the differential group index of both the pure-silica fiber glass and fundamental mode supported by the holey fiber.