Design, fabrication, and packaging of free space optical interconnects

Free-space optical interconnects can potentially solve the communications bottleneck in high-performance/parallel computing. The optical transpose interconnection system (OTIS) is one particular optical interconnect which has been shown useful for shuffle based multi-stage interconnection networks. Using commercially available ray-tracing optical design software, OTIS systems based on diffractive lenslets have been designed and optimized; the various design approaches are compared and the optimal design is extracted. System geometry, symmetry, and illumination issues relevant to the system design are also addressed.; Another major class of free-space optical interconnects is the microbeam relay, which uses a microlens for each optical transmitter and receiver. Because of the small apertures and long propagation distance, geometrical optics is not a valid approximation, and ray-tracing is not an acceptable simulation method. This type of optical system is usually modeled using the Gaussian beam formulae. A more accurate method to simulate the effects of truncation of a Gaussian beam at a lens plane is presented; this method is particularly well suited for modeling the microbeam relay. Using a complete Gaussian beam model, also including the effects of misalignments, a system design study and tolerancing procedure is presented. The tolerancing procedure is based on several statistical techniques such as Monte Carlo simulation, the Design of Experiments method, and regression analysis.; Finally, a packaged OTIS system is presented. The optics provide a bi-directional connection between two optoelectronic chips, each of which contains thirty-two modulators and detectors. The optical system consists of two polarization-selective computer generated holograms, which combine a 4x8 lenslet array for illumination of the modulators and a 2x2 lenslet array for interconnection, allowing for a very simple and compact optical system. In addition to the holograms, the only other components necessary to complete the optical system are a polarizing beam splitter, two quarter-wave retardation plates, and a spacer. All of the optics are aligned and packaged into a single unit that is remarkably compact: 12.x32.2mm, weighing only 8.3g.