Centralized optical backplane bus using holographic optical elements for high performance computing
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Optical communication is distinguished for its enormous interconnect capacity over long distance. As the cost of optical components drops, high bandwidth optical systems were successfully employed into local area network and computer racks because electrical counterparts are not able to deal with the data rate demands for these applications. With the popularity of multi-core CPU in High Performance Computers, the board-to-board interconnects exclusive based on electrical technology in backplane applications become insufficient because of not only bandwidth crises, but also wiring congestions. Many researches have projected that the progress of optical technology will further push down the boundary demarcating electrical and optical domains in the interconnect hierarchy. Accordingly, backplane or even board-to-board level interconnects will benefit from the complement of optical interconnect. From architecture point of view, an optical bus implementation of the optical interconnect has the potential advantage of both huge bandwidth and elimination of wiring congestion. In contrast, optical waveguide and free-space interconnects although provide high bandwidth capacity, are essentially point-to-point technology which requires routing to a central switch on the backplane. The centralized approach that was based on substrate guided optical interconnects is the only way known that fulfills a uniform fan-out for different nodes in a bus architecture, which allows medium sharing among nodes. In this dissertation, innovative bit-interleaved optical backplane bus architecture is created based on centralized substrate-guide optical interconnect, which allows the tremendous bandwidth capacity to be shared by retaining the share bus architecture. Therefore, a secure and reliable high speed transmission channel could be established by distributing copies of confidential information separately. The feature provided by this innovative design cannot be fulfilled using electrical interconnects or other optical point-to-point technology without causing wiring congestions. In this dissertation, the optical characteristics of the centralized optical bus such as bandwidth and alignment tolerance are analyzed so that multi-channel implementation are successful on the fabricated optical interconnect layer. A 3-board-16-channel computer server using optical backplane board demonstrator using centralized optical bus was built upon the simulation, design and packaging work.