  In this paper we consider stationary solutions to the nonlinear
one-dimensional Schroedinger equation with a periodic potential and a
Stark-type perturbation. In the limit of large periodic potential the
Stark-Wannier ladders of the linear equation become a dense energy spectrum
because a cascade of bifurcations of stationary solutions occurs when the ratio
between the effective nonlinearity strength and the tilt of the external field
increases.
