Dense optical bus arrays and optical routing components have limitations due to crosstalk between the waveguides and interference causing from system parameters. In this paper, crosstalk and interference penalty behavior in single mode polymeric optical bus arrays and optical multiplexers are investigated. It is shown that crosstalk power penalty and hence the waveguide density in these devices is controlled by crosstalk occurring due to the neighboring waveguides as well as systems parameters such as optical source linewidth, frequency spacing between sources, optical source and photodetector noises, waveguide parameters and others.