  We study the interference of two tunable Rashba regions in a quantum wire
with one propagating mode. The transmission dips (Fano-Rashba dips) of the two
regions either cross or anti cross depending on the distance between the two
regions. For large separations we find Fabry-P\'erot oscillations due to the
interference of forwards and backwards propagating modes. At small separations
overlapping evanescent modes play a prominent role, leading to an enhanced
transmission and destroying the conductance dip. Analytical expressions in
scattering-matrix theory are given and the relevance of the interference effect
in a device is discussed.
