  We describe power-dependent dynamics of conversion of the guided modes of
various guiding structures due to nearly resonant longitudinal modulation of
the nonlinear coefficient of the medium. It is shown that the control of the
energy exchange integrals, as well as of the input weights of the interacting
modes is especially crucial for efficient mode conversion in the setting
considered here. Complex dynamics of conversion incorporates various scenarios,
including non-harmonic oscillations of the energy weights, which mimics Jacoby
elliptical functions.
