Design limitations of highly parallel free-space optical interconnects based on arrays of vertical-cavity surface-emitting laser diodes, microlenses, and photodetectors

The packing density of a highly parallel free-space multi-stage optical interconnect network involving arrays of vertical cavity surface-emitting lasers (VCSELs), microlenses, and photodetectors is analyzed for the first time, based on a crosstalk model involving the diffraction-induced crosstalk among pixels. Variations of channel packing density, interconnection distance, and optical transmission efficiency are evaluated to provide optimum design parameters for the arrays of VCSELs, microlenses, and photodetectors. It is shown that it is pivotal to optimize the photodetector diameter in such an optical interconnect network. Photodetector array misalignment effects on system performance are further investigated, providing both transverse and longitudinal alignment tolerance. Several experiments are also conducted to verify the theory developed herein.