Board-level Optical Interconnect Link Design Studies

With decreasing transistor size, increasing chip speed, the data transmission between those chips is dramatically increasing as well, as a result the electrical transmission lines consisted of copper wiring will be confronted with "electrical interconnect bottleneck" such as bandwidth limited, signal crosstalk, power dissipation increasing sharply, so traditional electrical interconnect will not be able to accommodate the requirement of data traffic. Optical interconnect offer a good solution to improve the performance of data transmission, since it has many advantages compared with electrical interconnect and will replace it. Now optical interconnect between chips on board-level is still in an early stage of development and there is no some protocol or standard. This thesis will study the optical interconnect link design of physical layer which suits for board level.At first we choose the component for link design and discuss the transmission medium for board level optical interconnect. Many possible transmission medium such as free space, glass optical fiber, polymer waveguide and plastic optical fiber compared and analyzed. Among them, the plastic optical fiber (POF) is the appropriate choice after the mechanical properties, optical properties and cost compared and analyzed.Then four design specifications are proposed, which refer to low cost, high efficiency (low loss), high bandwidth, scalable. High efficiency means that the efficiency of OE/EO conversion of active component and transmission of medium are high. Now the obstacle of optical interconnect application is that the coupling in optical path is more complicated than electrical path. We analysis the influence of misalignment error of optical interface in the link (VCSEL-POF, POF-POF, POF-detector), and gained the coupling tolerance based theoretical analysis, experiment confirm and simulate calculation. Since the dimension of POF is large, POF-detector can't use butt-coupling. We discuss the coupling scheme based ball lens.For the reasons that limited space of board level optical interconnect and architecture of link, some bending paths exist in the link. We analysis the link from bending path, and discuss the influence of parameters using ray trace method. Then the parameters are optimized and the design rules of bending path are proposed.We discuss the performance of the whole link, and analysis the power budgets with three different configurations.At last we design two schemes for optically powered transmission, namely, photovoltaic power generation and fiber-based optical energy transfer. It use E-O-E energy supply to achieve the optically powered input, which is electrical isolation completely and will the information processing system used in some extremely occasions.