In wavelength division multiplexing (WDM) systems, coarse and dense WDM (CWDM/DWDM) are two key technologies. In general, it takes two steps to accomplish this mixing (coarse/dense) WDM function. In order to make the WDM device compact and low loss, it is necessary to integrate these two WDM functions into one step. In this paper, we propose two typical designs of the coarse/dense multiplexers, which multiplex the coarse/dense-WDM (C/D-WDM) signals simultaneously. We believe that, although their operation principle is simple, the proposed structures simplify the design of integrated photonic devices and will be the guideline in the development of future WDM devices.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.