Bandwidth limitations and dispersion in optical stellar interferometry

The fringe visibility measured by a stellar interferometer may be degraded if the interferometer uses an air delay line without compensating for longitudinal dispersion. Whereas in such circumstances simultaneous observations across the visible spectrum are shown to be impracticable at baselines as short as 10 m, it is shown possible to detect 95% of the visibility amplitude if the measurements are made sequentially at different wavelengths and the fractional bandwidth Δλ/λ at 950 nm is restricted to less than 10% when the baseline is 10 m, 6% at 30 m, and 3% at 100 m.