A new structure by combining a single cavity and coupled-cavity waveguides (CCWs) for wavelength division multiplexing (WDM) applications was proposed. As such, a structure in which the coupling between the cavity mode and the guiding model allows to drop a selective wavelength λi was designed. The selectivity of dropping wavelength was determined by local properties of the cavity modes. Such results were said to be important for designing future ultrasmall optical circuits.