The fabrication of polymeric single-mode Gaussian profile optical waveguides is described. We used poly(methyl methacrylate) and a mixture of two intermiscible monomers for the cladding and the core, respectively, of the waveguides. The cores of the waveguides were fabricated by with an argon-ion laser beam. The waveguides had single-mode Gaussian refractive-index profiles. By using such waveguides, we fabricated directional couplers for power coupling to the adjacent waveguides and also parallel waveguide arrays for preventing power coupling to adjacent waveguides for use in interconnect chips. We analyzed the characteristics of these couplers by using the coupled-mode theory and compared the results with those obtained with the beam propagation method. Experimental results showed good correlation with the theoretical values. We designed optical bus arrays for interconnect chips, considering the variation of normalized frequency V, the power penalty, and the dimensions of the waveguides and the separation between them. The number of waveguides in the bus array increased with increasing V. For a known value of V, a waveguide’s density increases with a decrease of its dimensions. The theoretical maximum number of waveguides is ∼1490/cm and ∼846/cm for 2 μm × 2 μm and 4 μm × 4 μm single-mode waveguides, respectively, to satisfy a 1-dB power penalty criterion at bit-error rate of 1029. We fabricated interconnect bus arrays with fifteen 4 μm × 4 μm waveguides for a 3-cm coupling length, and the experimental results were verified to be in good agreement with the theoretical values. © 1998 Optical Society of America.