PCB integrated waveguides - launching light into highly multi mode structures

One future solution for overcoming the growing gap between the internal and external clock rates of today\´s integrated circuits lies undoubtedly in using optical interconnection technology on the PCB level. The requirements for PCB integration call for structural dimensions which enable multi mode transmission only. Up to now, the theoretical basis for the simulation of highly multi mode waveguides is still developing. However, the launching condition strongly influences the mode distribution. This is the reason why an empiric attempt to characterize the waveguide\´s light guiding properties was performed. For quality assessment of integrated waveguides, a computer controlled set-up for attenuation measurement was realized. The evaluation was carried out on an example of the "waveguide-in-copper" technology, The respective technology yields PCB integrated polymer waveguides. The paper analyzes the particularities of highly multi-mode structures in principle. By means of preliminary measurements, the effect of different coupling conditions on the mode distribution is discussed. Furthermore, the influence of changes in mode distribution on power transmission is presented.