The local mode theory for two copropagating and two counterpropagating
waves in nonlinear waveguides is formulated. The presented model allo
ws us to describe the inverse effects as well as the propagating waves
interaction in optical waveguides. The results are compared with the
conventional coupled mode theory solution and they can be applied to t
he analysis of such devices like nonlinear directional couplers and wa
veguide Fabry-Perot resonators.