A Concept for Accurate Edge-Coupled Multi-Fiber Photonic Interconnects

The alignment and fixation of multiple single-mode optical fibers to photonic integrated circuits is currently a challenging, expensive, and time-consuming task. In this paper, we present a concept for a sub-micrometer accurate multi-fiber array, where fibers are actively aligned with respect to each other and fixated to a flat carrier using ultraviolet-curable adhesive. Adhesives are prone to shrinkage, which can disturb the fiber alignment. As a result, especially, the fixation process forms the bottleneck in reaching the required alignment and not the alignment process itself. Simulations are performed to investigate the sensitivity of process variables on the adhesive bond geometry, which is important for the shrinkage amplitude. Furthermore, an experimental setup has been designed and fabricated to measure the shrinkage-induced fiber displacement for three selected types of adhesives. The results show a controllable adhesive shrinkage, where fibers can be aligned with a position reproducibility of ±40 nm, which is more than sufficient for the most critical fiber alignment applications. With this concept, an important step can be made in enabling sub-micrometer accurate photonic interconnects in a cost-effective way, which is suitable for automated production.