Parasitic Coupling Effects in Multimode Buried Channel Waveguides Arrays for O-PCB Interconnects

The use of buried channel waveguides in optical printed circuits boards (O-PCB) offers the possibility of overcoming some 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 the buried channels may appear when waveguide arrays are realized. In this paper, we analyze theoretically and experimentally the conditions inducing crosstalk effects in a multimode array, realized by means of a conventional photolithographic patterning technique. In particular, the results show how the common configuration used to pattern an array of optical waveguides produces a parasitic slab waveguide close to the core channels, accounting for a substantial increase of the coupling effects.