The use of buried channel waveguides in optical printed circuit boards (O-PCB) offers the possibility of overcoming problems and limitations encountered in high-frequency electrical interconnects. Although the use of optical waveguides reduces significantly crosstalk and electromagnetic interferences, parasitic coupling effects between adjacent channels may appear. In a recent study, published by the prestigious Journal of Lightwave Technology, researchers from Somacis pcb industries and Dibet showed this effect to be dependent upon the formation of a parasitic slab waveguide that induces coupling between adjacent buried channels. Then, they suggest this formation to reasonably be a consequence of the refractive index variation caused by the waveguide array realization process.