Exploring Slow & wide approach using uLEDs and uVCSEL for AI scale up networks

Time: Tuesday, 3 November 2026 | 1:30 p.m. - 5:00 p.m.

Location: Conference Room 205

Session Description:

Optical I/O (OIO) interconnect technology aims to address power and bandwidth bottlenecks in AI computing clusters for Chip-to-Chip (C2C) and Device-to-Device (D2D) scenarios through a “high-parallelism, low-single-channel-rate” architecture. Regarding transmitter selection, Mode-Refractive Modulators (MRMs) are the mainstream solution in OCI-MSA due to their miniaturization, CMOS compatibility, and support for high-speed single-channel and WDM expansion.

However, since MRMs require independent DFB lasers, direct modulation schemes using MicroLEDs (uLEDs) and MicroVCSELs (uVCSELs) offer potential for further cost and power reduction. uLEDs exhibit superior thermal stability but suffer from low single-channel bandwidth (1–4 Gbps) and complex coupling processes, necessitating breakthroughs in single-channel rates or the design of low-power Gearboxes to adapt to switch interfaces. In contrast, uVCSELs provide higher bandwidth, yet the yield of high-density arrays and the maturity of Fiber Array Units (FAUs) remain to be validated. 

To achieve extreme low power consumption, OIO technology must evolve toward a Serdes-less and Gearbox-less form, facing challenges in architecture compatibility, performance, packaging/coupling processes, and multi-channel reliability. This requires restructuring the switch architecture, including supporting I/O Die direct drive for low-speed parallel channels, adjusting Small IO bandwidth (4G–64G), and adopting control-data separation scheme. Furthermore, when using low-cost light sources, receiver performance must be enhanced via high-sensitivity Photodiodes (PDs) and low-noise CMOS TIAs. As parallelism increases, novel packaging solutions like 2.5D TMV and 3D TSV must be developed to integrate high-density optoelectronic devices with chips, while precise coupling with various fiber types remains an engineering challenge. Finally, thermal risks must be addressed, and redundancy designs implemented to mitigate reliability risks arising from engineering fluctuations.

Keywords: Switch, OIO, MRM, uLED, uVCSEL, Data Center Interconnect

Organisers:

Ye Yao, Huawei Hisilicon

Gordon Ning Liu, Soochow University

Frank Chang, Source Photonics