板级光互连链路设计研究

【作者】 邵科杰；

【导师】 李剑峰；

【作者基本信息】 中国工程物理研究院 ， 光学， 2009， 硕士

【摘要】 随着晶体管尺寸不断缩小,芯片速度不断提高,芯片间传输的信息量也越来越大,电传输线将面临着带宽受限、信号串扰、功耗急剧增加、时钟歪斜等“电子互连瓶颈”,传统的电互连逐渐无法满足高性能传输的要求。光互连相比电互连具有无可比拟的优势,是未来替代电互连的最佳选择。目前,板级芯片问的光互连研究刚刚起步,还没有建立起相关的协议标准。本文研究了适用于板级芯片间光互连的物理层链路设计。首先在元器件的选择上,重点讨论适用于板级光互连的传输介质。比较并分析自由空间、石英光纤、聚合物波导、塑料光纤等各种可能的传输方案,综合考虑成本、光学特性、机械特性等因素,塑料光纤是目前最合适的选择。然后提出了链路设计过程中需遵循的四条规范:低成本、高效率(低损耗)、高带宽、可扩展性。其中高效率包括有源器件的光电/电光转换效率高、链路的传输效率高。从目前来看,影响光互连技术走向实用的主要障碍来自光路的耦合与器件连接比电互连更加复杂,于是分析了链路中各个光接口(VCSEL—POF、POF—POF、POF—探测器)机械对准误差的影响,并根据理论分析、实验验证、模拟计算等方法确定耦合容限。由于POF纤芯尺寸较大,POF-探测器连接不能采用直接耦合,本文详细讨论了基于球透镜的耦合方案。板级光互连链路空间有限以及链路体系结构等原因,光路必然存在弯曲。本文分析弯曲光路对链路性能的影响,采用光线追迹法讨论了元件参数的影响,并进一步优化参数,提出弯曲光路设计准则。对链路整体进行分析,分析了三种不同配置方案的功率预算。最后设计了两种光供能方案,分别是光伏发电与光纤传能。以电-光-电方式实现了能量供应的光输入,完全电隔离,可使信息处理系统应用在一些特殊场合。更多还原

【Abstract】 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.更多还原