A new optical hybrid technology that employs a hollow waveguide (HWG) structure has the potential to cut more than 50% off the cost of complete optical circuits, according to its developers at UK-based QinetiQ.
The Hollow Waveguide (HWG) itself is etched from a flat substrate, providing a guide channel in the material 50 microns or more wide through which light travels. This approach to making the waveguide makes it easier to achieve a low polarisation dependent loss (PDL), according to QinetiQ.
The performance of the waveguide may be also be enhanced by coating the guide walls to alter its optical properties. A lid is attached to the structure to provide a fourth guide wall.
The HWG complements the traditional ‘rib’ or ‘ridge’ guide structure and maintains all the usual performance criteria of such a structure.
But it has some advantages over the conventional approach too. Qinetiq developers say that discrete devices can be placed directly into the structure with very simple interfaces and low tolerance placement. And Multi Mode Interferometry devices (MMI) can be fabricated directly in the substrate using the same process that is used to make the HWG.
This can allows splitters, MUX/DEMUX and combiners to be manufactured monolithically in one process step. The same process could also be used to make MEMS devices – a MEMS Variable Optical Attenuator (VOA), filter and switch could be made directly in the guide and no alignment of the components would be required.