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

在计算机芯片的当前设计中，电线用于芯片的不同组件之间的通信。随着技术缩小到纳米领域，由电线引起的信号延迟和功耗开始主导芯片上的整体延迟和功耗，主要是因为电线不像其他逻辑元件那样缩放。一个有希望的替代使用电线的方法是使用光波导进行通信。将纳米光子学用于片上通信可以导致更快的信号传播、增加的带宽密度和降低的功耗。然而，将光学器件集成到商业芯片中面临着许多根本性的挑战。该项目解决了其中的一些挑战，其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。前者是指由于制造过程中的制造误差而导致的光学器件谐振波长的漂移。后者指的是在操作期间由于芯片内的温度波动而导致的类似漂移。这两种漂移在当前技术下都是不可避免的，并导致光网络损失大量带宽。而不是依赖于设备级的创新，所提出的研究采取了一种架构的方法来忍受和容忍波长谐振漂移。具体来说，它研究了不同的技术，以最大限度地提高有效带宽在运行时存在的缺陷和工作温度的变化。这些技术将带宽视为按需分配给不同节点的资源，以掩盖光学设备的谐振偏移。由于聚合的可用片上带宽通常大于对带宽的瞬时需求，因此通过将波长适当地分配给节点来减轻不完美硬件的影响，从而为系统的其他组件提供可靠且近乎完美的光通信层。

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.