  We introduce soliton percolation phenomena in the nonlinear transport of
light packets in suitable optical lattices with random properties.
Specifically, we address lattices with a gradient of the refractive index in
the transverse plane, featuring stochastic phase or amplitude fluctuations, and
we discover the existence of a disorder-induced transition between
soliton-insu-lator and soliton-conductor regimes. The soliton current is found
to reach its maximal value at intermediate disorder levels and to drastically
decrease in both, almost regular and strongly disordered lattices.
