Design, implementation and characterization of free-space optical interconnects for optical backplanes

Free-space optical interconnects (FSOIs) represent a potential solution for solving the bottleneck associated with the increasing demands for high bandwidth interconnections in modern communication services and advanced computing systems. Such interconnects utilize two-dimensional smart pixel arrays to take advantage of the additional degree of freedom gained in FSOIs. As a result, thousands of parallel optical channels may be available. This thesis studies the design issues of board-to-board free-space optical interconnections. The impacts of device technology, the data-link topology of multiple-board interconnections, and the imaging mapping between stages are explored. Four types of free-space optical interconnects have been examined in terms of system complexity, scalablity, and alignability. In particular, the alignment tolerance of a symmetric optical interconnect is analytically studied. Comparison of alignment tolerances is carried out between a system with telecentric configuration and a system with maximum lens-to-waist configuration. It has been shown that interconnection between integrated microlenses/transmitters and microlenses/receivers is generally more alignment toleranced than that of non-optical integrated transmitters and receivers.Key issues are identified and explored in the design, implementation and characterization of three types of optical systems, namely macrolens based optical interconnect, microlens based optical interconnect and hybrid-lens based optical interconnect. The microchannel optical interconnect employing a window-clustering scheme is demonstrated as well. The uniformity issue of a spot array generation using diffractive fanout gratings is experimentally studied. Imaging mapping between interconnection stages is developed using a standard matrix representation. For a complex multistage modulator-based free-space optical interconnet, the component requirements, alignment and assembly procedures, characterizing techniques, and system performance are presented. It is believed that modular subsystems with passive in-situ alignment techniques have potential for providing the required alignment solution of implementing free-space board-to-board interconnects