Micro-optical System for Selective Excitation of Higher-order Fiber Modes

The increasing demand for high data rates to advance classical and quantum communication has become evident in the recent years. Space-Division-Multiplexing (SDM) overcomes the fundamental limit of channel capacity due to bandwidth, signal to noise ratio, environmental factors. Successful implementation of SDM requires devices such as mode-converters (e.g., phase plates) which come at a cost of considerable designing and fabrication effort and often have low transmission efficiency due to alignment imperfections and high wavelength dependencies. This work aims to analyze the prospect of selectively coupling two normally-incident gaussian beams into LP11 modal lobes. The input gaussian beams are optimally offset from the output fiber core axis and do not require direct phase manipulation. Initially, the concept was validated using a simplified mathematical model followed by design and optimization of a micro-optical system using ray- and wave-optical simulation tools. Finally, we fabricated a three-fold fiber connector combining precise mechanical mounting with our simulated optical system using two-photon polymerization-based 3D printing. 74 optik und integrierte Optik M. Hofmann