Coupling structures for out-of-plane coupling in optical PCBs

Abstract

Coupling structures are critical building blocks that have a big influence on the performance of board-level optical interconnections. 45° micro-mirrors deflect the light beam over 90° and are used for out-of-plane coupling in single layer structures and out-of-plane and inter-plane coupling in multilayer structures. Two different approaches are being presented: a micro-mirror that is directly integrated with the multimode waveguides and a discrete coupling element that can be plugged into a cavity in the optical layer. The advantage of the integrated micro-mirror is the high achievable alignment accuracy. The discrete couplers on the other hand have the advantage that they can be characterized and measured prior to the insertion into the optical layer. Both mirror configurations are discussed and the performance is evaluated at wavelength 850nm.