8 March 2023
In booth #3950 at the Optical Fiber Communication conference (OFC 2023) in San Diego (7–9 March), Avicena Tech Corp of Sunnyvale, CA, USA (which develops ultra-low-energy optical links based on micro-LEDs) is demonstrating what is claimed to be the highest-temperature optical link, operating at up to 235°C using its LightBundle communication architecture and technology. The LightBundle architecture is said to unlock the performance of xPUs, memory and sensors, removing key bandwidth and proximity constraints while simultaneously offering an order-of-magnitude reduction in power consumption.
Most optical links use edge-emitting lasers or vertical-cavity surface-emitting lasers (VCSELs), but these typically exhibit dramatic performance and lifetime reductions at operating temperatures above 85°C and are thus unable to meet the 5–10-year field lifetime requirements of many higher-temperature applications. The lifetime limitations of these communications lasers are related to fundamental properties of the gallium arsenide (GaAs) and indium phosphide (InP) from which nearly all are made, and thus have proved very difficult to improve significantly despite decades of effort.
In contrast, Avicena’s LightBundle links use micro-LEDs made from gallium nitride (GaN), and are much less sensitive than GaAs and InP lasers to operating temperature, specifically regarding performance and reliability. Combined with high energy efficiency and low cost, these attributes have allowed GaN LEDs to transform the lighting industry over the past decade. LightBundle technology is based on arrays of GaN micro-LEDs that leverage the LED lighting and display ecosystems, and can be integrated directly onto high performance CMOS ICs. Each micro-LED array is connected via a multi-core fiber cable to a matching array of CMOS-compatible photodiodes (PDs).
Now, Avicena has demonstrated LightBundle links operating at up to 235°C. This brings the benefits of optical interconnects to the harsh environments encountered in a wide variety of automotive, industrial, aerospace and defense applications, while also offering other benefits of the LightBundle architecture, says the firm.
“We have already demonstrated the benefits of LightBundle links in data center, HPC [high-performance computing] and ML/AI [machine learning/artificial intelligence] with bleeding-edge power and density requirements,” says Chris Pfistner, VP of sales & marketing. “We have now shown that the unique benefits of the GaN materials system in micro-LEDs extends to applications with operating temperatures that have traditionally been beyond the capabilities of optical interconnects. This is igniting interest among our partners and customers in numerous market segments in the automotive, defense and aerospace industries.”
Today’s high-performance ICs use SerDes-based electrical links to achieve adequate IO density. However, the power consumption and bandwidth density of these electrical links degrade quickly with length. Conventional optical communications technologies developed for networking applications have been impractical for inter-processor and processor–memory interconnects due to their low bandwidth density, high power consumption, and high cost. Moreover, co-packaging existing laser sources with hot application-specific integrated circuits (ASICs) causes reliability problems unless external laser sources (ELS) are used, which increases complexity and cost.
“All of this is now changing,” says chief technology officer & co-founder Rob Kalman. “We are developing ultra-low power, high-density optical technology based on GaN micro-LED arrays optimized for high-speed interconnects. Our technology and inventions build on recent display industry advances and would have been impractical just a few years ago,” he adds. “Our innovative LightBundle architecture supports hundreds of lanes with per-lane speeds of 10Gbps or more to enable multi-Tbps links meeting the most demanding emerging compute interconnect needs. This also frees system designers to innovate beyond the bounds of today’s proximity constraints.”
Avicena says that the low power, high density and low latency of LightBundle is well matched to chiplet interfaces like UCIe, OpenHBI and BoW, and can also be used to rethink and enhance system architectures that are limited by the reach of existing compute interconnects like PCIe/CXL, and HBM/DDR/GDDR memory links.
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