  We study theoretically two coupled periodically-curved optical waveguides
with Kerr nonlinearity. We find that the tunneling between the waveguides can
be suppressed in a wide range of parameters due to nonlinearity. Such
suppression of tunneling is different from the coherent destruction of
tunneling in a linear medium, which occurs only at the isolated degeneracy
point of the quasienergies. We call this novel suppression nonlinear coherent
destruction of tunneling.
