  Typical two-path interferometers are intensity-balanced because this
maximizes the visibility of their interference patterns. Unbalancing the
interferometer can be advised when back action on the object whose position is
monitored is to be reduced. Variations of the intensity splitting ratios in
two-path interferometers are analyzed in order to determine optimal
interferometric performance while minimizing back action: it turns out that
homodyning-like schemes perform best.
