Energy-Efficient Photonics in Future High-Connectivity Computing Systems

Abstract

Energy-efficiency has become a critical parameter in the design of high-performance computing systems. Typically, compute elements consume the most energy in current systems, withmemories and interconnect networks close behind. This paper proposes an energy-efficient, high-connectivity, petascale computing system for the year 2020 timeframe by addressing the energy requirements of these three components. We start with projections based on purely evolutionary computer system design trends, then include the impact of breakthroughs in processor design, memory packaging and optical interconnect technologies. Based on these projections, we motivate the development for a 1-pJ/b optical intrasystem interconnect technology that significantly increases system interconnect bandwidth and relieves the distance-based energy dependence of electrical alternatives. We show that improvements in compute, memory, and IO, when simultaneously applied, become a vision for many-chip photonically-interconnected modules that could lead to an order of magnitude improvement in energy efficiency in the 2020 timeframe. The vision hinges on a high-density, energy-efficient optical link that can connect electronic compute and memory elements across short chip-to-chip distances while also capable of kilometer or longer spans across data centers. We discuss the power budget to enable such a link and review experimental progress toward creating an ultra-dense, hybrid-integrated low-power silicon photonic link that will enable this vision.

Attojoule Optoelectronics for Low-Energy Information Processing and Communications

“…Later, in Section VIII B, we will discuss "dual-rail" operation with stacked pairs of diodes, which avoids this difficulty for circuits with no load resistor. 17 The diode and load capacitances are effectively in parallel in a circuit like this. To change the voltage V OUT we have to charge or discharge both capacitances.…”

“…That energy must include the energy of all circuits, including the output driver circuit and, especially, the receiver circuit. Receiver circuits can dissipate substantial energies, in some cases possibly even being the largest single contributor to the power consumption overall in a link [17].…”

“…There are two basic approaches to WDM for short-distance interconnects: we can use passive optics to split different wavelengths to photodetectors and to combine signals on different wavelengths from modulators that do not themselves need to be tuned or resonant (see, e.g., [137], [138], [139]); or we can use resonator modulators and/or photodetectors that themselves extract the WDM channels by tuning to specific wavelengths (see, e.g., systems using sets of microring or microdisk resonators, each tuned to a chosen different wavelength [14], [17], [20], [105]). See also [140] for a critical analysis of WDM approaches for dense interconnections.…”

“…and cavity finesse F can loosely be considered either as energy stored within the cavity energy lost during one cavity round trip 2π 17) or equivalently as number of cavity round trips a photon makes before being los 2 t…”

Numerical Investigation of A New Junctionless Phototransistor for High-Performance and Ultra-Low Power Infrared Communication Applications

“…In the long-haul telecommunication system, the huge power consumption by the traditional transmission wires is an important limitation which degrades the communication system performance in terms of cost and power dissipation [1][2]. However, optical interconnects are considered as a good solution to remedy the problems faced by electric wires and can refashion the inter-chip data communications systems [2][3][4].…”