An extended analysis of the effects of uncompensated fiber dispersion on the fringe visibility of a fiber optic interferometer is developed, with particular emphasis on stellar interferometry. Both material and waveguide dispersion for single-mode, polarization-preserving fibers are considered. It is found that dispersion causes the fringe visibility curve to broaden, decrease in contrast, shift its centroid location, and in some cases become asymmetric. It is also shown that when the interferometer is operated at wavelengths near 1300 nm, cancellation of second-order material and waveguide dispersion significantly improves the fringe visibility. The theoretical results are verified experimentally at both 672 nm and 1307 nm using a fiber optic Mach-Zehnder interferometer. © 1997 Society of Photo-Optical Instrumentation Engineers.