EAGER: Tackling the Variations and Instability of Nanophotonic Interconnection Network via Architecture Techniques

在目前的计算机芯片设计中，芯片的不同组件之间使用电线进行通信。随着技术向纳米领域缩小，电线引起的信号延迟和功耗开始主导芯片上的总体延迟和功耗，主要是因为电线的规模不如其他逻辑元件。使用电线的一个有前景的替代方案是使用光波导来进行通信。使用纳米光子学进行片上通信可能会导致更快的信号传播速度、更高的带宽密度和更低的功耗。然而，将光学设备集成到商业芯片上面临着许多根本性的挑战。该项目解决了其中的一些挑战，它的成功将对半导体行业产生重大影响。该项目解决的两个主要挑战是工艺变化和光学器件的热敏性。前者是指光学器件在制造过程中由于制造误差而引起的谐振波长的漂移。后者指的是由于芯片内部的温度波动而在操作过程中产生的类似漂移。这两种漂移在当前技术下都是不可避免的，并会导致光纤网络失去大量带宽。这项拟议的研究没有依赖于设备级的创新，而是采用了一种架构方法来忍受和容忍波长共振中的漂移。具体地说，它研究了在存在缺陷和运行温度变化的情况下最大化运行时有效带宽的不同技术。这些技术将带宽视为按需分配给不同节点的资源，其方式屏蔽了光学设备的共振偏移。由于聚合的可用片上带宽通常大于对带宽的瞬时需求，因此通过适当地向节点分配波长来减轻不完美硬件的影响，从而向系统的其他组件提供可靠且接近完美的光通信层。

In current designs of computer chips, electrical wires are used for communication between the different components of the chip. As technology scales down into the nanometer domain, the signal delay and power consumption caused by electrical wires start to dominate the overall delay and power consumption on the chip, mainly because wires do not scale as well as other logic components. A promising alternative to using electrical wires is to use optical waveguides for communication. Using nanophotonics for on-chip communication may lead to faster signal propagation, increased bandwidth density and reduced power consumption. However, many fundamental challenges face the integration of optical devices into commercial chips. This project addresses some of these challenges and its success will have a significant impact on the semiconductor industry.The two major challenges addressed in this project are process variations and thermal sensitivity of optical devices. The former refers to the drifts in resonance wavelengths of optical devices due to fabrication errors during the manufacturing process. The latter refers to similar drifts that result during operation due to temperature fluctuations within the chip. Both drifts are inevitable with current technology and cause the optical network to lose significant bandwidth. Instead of relying on device level innovations, the proposed research takes an architectural approach to endure and tolerate drifts in wavelength resonance. Specifically, it investigates different techniques to maximize the effective bandwidth at run-time in the presence of defects and changes in operating temperatures. These techniques treat bandwidth as a resource that is allocated, on-demand, to different nodes in a way that masks the resonance shifts of optical devices. Since the aggregated available on-chip bandwidth is usually larger than the instantaneous demand for bandwidth, the effect of the imperfect hardware is mitigated by appropriately assigning wavelengths to nodes, thus offering a reliable and near perfect optical communication layer to the other components of the system.