This work presents design guidelines and performance investigation of plasmonic wavelength demultiplexers for optical communication systems. First the performance of multichannel demultiplexers designed using planar metal-insulator-metal plasmonic structure is investigated. Each demultiplexer unit consists of a bus waveguide supported by two, feedback and drop, nanocavities. Detail parametric study is used to design a high-drop efficiency demultiplexer. The results are then coupled with particle swarm optimization technique to redesign the demultiplexer with high drop efficiency. Simulation...