The role of optics in future high radix switch design

Abstract

For large-scale networks, high-radix switches reduce hop and switch count, which decreases latency and power. The ITRS projections for signal-pin count and per-pin bandwidth are nearly flat over the next decade, so increased radix in electronic switches will come at the cost of less per-port bandwidth. Silicon nanophotonic technology provides a long-term solution to this problem. We first compare the use of photonic I/O against an all-electrical, Cray YARC inspired baseline. We compare the power and performance of switches of radix 64, 100, and 144 in the 45, 32, and 22 nm technology steps. In addition with the greater off-chip bandwidth enabled by photonics, the high power of electrical components inside the switch becomes a problem beyond radix 64.We propose an optical switch architecture that exploits highspeed optical interconnects to build a flat crossbar with multiplewriter, single-reader links. Unlike YARC, which uses small buffers at various stages, the proposed design buffers only at input and output ports. This simplifies the design and enables large buffers, capable of handling ethernet-size packets. To mitigate head-of-line blocking and maximize switch throughput, we use an arbitration scheme that allows each port to make eight requests and use two grants. The bandwidth of the optical crossbar is also doubled to to provide a 2x internal speedup. Since optical interconnects have high static power, we show that it is critical to balance the use of optical and electrical components to get the best energy efficiency. Overall, the adoption of photonic I/O allows 100,000 port networks to be constructed with less than one third the power of equivalent all-electronic networks. A further 50% reduction in power can be achieved by using photonics within the switch components. Our best optical design performs similarly to YARC for small packets while consuming less than half the power, and handles 80% more load for large message traffic.

Optimize the Power Consumption and SNR of the 3D Photonic High-Radix Switch Architecture Based on Extra Channels and Redundant Rings

“…Vantrease et al [6] proposed an optical interconnection network called Corona, which is a 64-radix multiwrite single read (MWSR) crossbar architecture. Many later researchers [5,[7][8][9] also proposed some other architectures based on Corona to improve the scalability of the silicon photonic network.…”

DSENT - A Tool Connecting Emerging Photonics with Electronics for Opto-Electronic Networks-on-Chip Modeling

“…One may expect that the high number of rings at 2 Gb/s results in huge ring tuning costs. However, the bit-reshuffling strategy strategies of [11,39] allow tuning costs to remain comparable; the large modulator, receiver, SerDes, and laser energy costs per bit incurred at high data-rate overwhelm the small savings in tuning power from having fewer λ and rings.…”

Modular architecture for fully non-blocking silicon photonic switch fabric

“…Optical switching has the potential to enable ultra-high capacity optical networks that can deliver large volumes of data with timeof-flight latencies [1][2][3][4] . A compact switching device has the potential to enable emerging applications in computing architectures such as optically interconnected processors and memories 5,6 .…”