Fan-out equalized shared optical backplane bus
Optics is distinguished for its interconnect capability. A variety of optical interconnect technologies have been successfully employed in the real applications where the conventional implementations that are exclusively based on electrical interconnects have become insufficient, and the boundary demarcating the electrical and optical domain is being further pushed down in the interconnect hierarchy. Many researches have projected an imminent bottleneck throttling the board-to-board data transfers. Accordingly, an opportunity exists for the continuing exploitation of optics to complement or even replace the conventional electrical backplanes. The most prominent benefit of utilizing optics is the tremendous gain in the bandwidth capacity. From the architecture point of view, however, three fundamental optical methodologies, optical waveguide interconnects, free-space optical interconnects, and substrate-guided optical interconnects, have a huge discrepancy in how effectively the obtained bandwidth gain would improve the overall system performance. The approaches that are based on optical waveguide or free-space interconnects provide only the point-to-point topology, in turn the various proposed architectures are essentially an optical point-to-point switched backplane. In contrast, the approaches that are based on substrate-guided optical interconnects can effectively fulfill the shared bus topology, and thus an optical backplane bus can be implemented. In this dissertation, the comparative examinations specifically point out that optical backplane bus has many considerable advantages over optical point-to-point switched backplane. An innovative optical backplane architecture, optical centralized shared bus, is created based on substrate-guided optical interconnects, which utilizes the beneficial physical characteristics of optics while retaining the desirable architectural properties of the shared bus topology. Therefore, it is projected that the bandwidth gain would be maximized. Superior to other optical shared bus architectures, this innovatively designed optical backplane bus can accomplish equalized fan-outs across the entire architecture in an elegant manner. This significant merit can substantially ease the overall system integration. In this dissertation, the equalized bus fan-outs are successfully established on the fabricated optical interconnect layer. To further verify the feasibility of optical centralized shared bus architecture in the practical scenarios, two research prototypes, a microprocessor-to-memory interconnect demonstrator and a centralized shared-memory multiprocessing emulator, are constructed with the physically characterized optical centralized shared bus.