We develop a nonlinear theory of soliton-induced waveguides that describes a
finite-amplitude probe beam guided by a spatial dark soliton in a saturable
nonlinear medium. We suggest an effective way to control the interaction of
these soliton-induced waveguides and also show that, in sharp contrast with
scalar dark solitons, the dark-soliton waveguides can attract each other and
even form stationary bound states.Comment: 3 pages, 4 figure