PCB integrated waveguides Launching light into highly multi mode structures

Abstract

One future solution for overcoming the growing gap between the internal and external clock rates of today’s integrated circuits lies undoubtedly in usage of 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 simulation of highly multi mode waveguides is still developing. However it is common knowledge that the launching condition strongly influences the mode distribution. This is the reason why an empiric attempt for characterizing 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 the 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 for the power transmission is presented.
Autorzy: Michał DUŻYNSKI, Ralf RIESKE, Klaus-Jürgen WOLTER, Sergiusz PATELA

1. INTRODUCTION

As can be assumed from the respective roadmaps there will be alternative interconnection technologies to address the steadily growing bandwidth demand. Optical interconnections are one possible as well as promising approach to bridge the gap between on-chip and off-chip clock rates on the printed circuit board (PCB) level. Future multilayer PCBs will therefore be hybrid devices combining electrical and optical interconnections. One of the solutions for a period of time before “all optical connections” is the “waveguide-in-copper” technology that yields PCB integrated polymer waveguides [6]. The key requirements for a successful introduction of these technologies are to enable freely structurable layers for economic integration to PCB processes and efficient passive alignment. To meet those conditions the geometric dimensions would only allow a multimode technology. Motivation for this article was to expand the existing set-up into the direction of reliable and repeatable attenuation measurements of integrated waveguides produced in the mentioned technology. The structure of the article encloses the fundamental part with short introduction into the theoretical aspects of work as well as used technology. Second would be the experimental part with exact description of undertaken experiments. Finally it will be summed up to emphasize the most important results and achievements.