MINIMIZATION OF FIBER DISPERSION EFFECTS IN DOUBLE FOURIER STELLAR INTERFEROMETERS

One of the problems encountered when using single-mode fibers in a wid e band interferometer is the dispersion of the waveguide. We relate he re the phase curvature of the interferograms with the dispersion param eter of the fiber. Total dispersion in a fiber is the sum of material and waveguide dispersion. By optimizing the waveguide structure for an actual fluoride glass, we show that a fiber can be made whose dispers ion between 2 mu m and 2.7 mu m is reduced by more than two orders of magnitude. Simulated interferograms show that an interferometer using such a fiber could withstand a fiber length difference of 10 m without a substantial degradation of its performances. This raises the possib ility to consider all-fiber delay lines with several meters of optical path delay variation.