As the industry moves towards Co-Packaged and Near-Packaged Optics, the fiber attach is forced to land on the PIC itself. Fiber coupling is a very precise endeavor, with micron level precision requirements. An edge coupler wants the fiber core roughly within half a micron of the waveguide otherwise this leads to unwanted coupling losses which are unaffordable for high bandwidth throughput.

This precision is brought usually with active alignment where each fiber is positioned at sub-micron accuracy (usually through signal peak calculations) and then glued down. This is however a serial process and ends up being unrealistic for high fiber count attach. More importantly, such an alignment system is inherently non-detachable.

This is where passive alignment becomes a viable alternative to active alignment. In such systems, mechanical features hold the fiber within tolerance. Fiber attach thus becomes a passive, repeatable and even re-mateable operation. (1/3)🧵