Intel has announced a significant advancement in integrated photonics technology, achieving a groundbreaking milestone in high-speed data transmission. At the 2024 Optical Fiber Communication Conference (OFC), Intel‘s Integrated Photonics Solutions (IPS) Group showcased the industry’s first fully integrated optical compute interconnect (OCI) chiplet.
This chiplet, co-packaged with an Intel CPU, was demonstrated running live data, marking a substantial leap in high-bandwidth interconnect technology for data centers and high-performance computing (HPC) applications.
Thomas Liljeberg, Senior Director of Product Management and Strategy at IPS, highlighted the importance of this development, stating, “The ever-increasing movement of data from server to server is straining the capabilities of today’s data center infrastructure, and current solutions are rapidly approaching the practical limits of electrical I/O performance. However, Intel’s groundbreaking achievement empowers customers to seamlessly integrate co-packaged silicon photonics interconnect solutions into next-generation compute systems.”
The OCI chiplet is engineered to support 64 channels of 32 gigabits per second (Gbps) data transmission in each direction over up to 100 meters of fiber optics. This design aims to meet the escalating demands for higher bandwidth, lower power consumption, and longer reach in AI infrastructure. The chiplet enables scalability of CPU/GPU cluster connectivity and supports novel compute architectures, including coherent memory expansion and resource disaggregation.
Optical I/O in CPUs and GPUs
The growing deployment of AI-based applications globally, particularly with advancements in large language models (LLMs) and generative AI, underscores the necessity for scalable computing platforms. These platforms require exponential growth in I/O bandwidth and extended reach to support larger CPU/GPU/IPU clusters. Traditional electrical I/O solutions, limited by short reach and high power consumption, are becoming inadequate for these evolving needs. Intel’s OCI chiplet, with its co-packaged xPU optical I/O solution, offers a higher bandwidth, improved power efficiency, and longer reach, addressing these critical requirements.
Using an analogy, replacing electrical I/O with optical I/O in CPUs and GPUs is akin to shifting from horse carriages, limited in capacity and range, to cars and trucks, capable of delivering larger quantities of goods over greater distances. This transition would reflect the enhanced performance and energy efficiency that optical I/O solutions like Intel’s OCI chiplet bring to AI scaling.
The fully integrated OCI chiplet utilizes Intel’s “proven” silicon photonics technology, integrating a silicon photonics integrated circuit (PIC), which includes on-chip lasers and optical amplifiers, with an electrical IC. The demonstration at OFC featured the chiplet co-packaged with an Intel CPU, but it can also be integrated with future-generation CPUs, GPUs, IPUs, and other system-on-chips (SoCs).
This initial OCI implementation supports up to 4 terabits per second (Tbps) bidirectional data transfer, compatible with PCIe Gen5. The live demonstration showcased a transmitter (Tx) and receiver (Rx) connection between two CPU platforms over a single-mode fiber (SMF) patch cord. The CPUs generated and measured the optical Bit Error Rate (BER), demonstrating strong signal quality with 8 wavelengths at 200 gigahertz (GHz) spacing on a single fiber.
The chiplet supports 64 channels of 32 Gbps data in each direction over distances up to 100 meters, though practical applications may be limited to tens of meters due to latency. It employs eight fiber pairs, each carrying eight dense wavelength division multiplexing (DWDM) wavelengths. The co-packaged solution is energy efficient, consuming only 5 pico-Joules (pJ) per bit compared to approximately 15 pJ/bit for pluggable optical transceiver modules. This hyper-efficiency is crucial for data centers and HPC environments, potentially addressing the unsustainable power requirements of AI infrastructure.
OCI Chiplet – Prototype
Intel’s leadership in silicon photonics is built on over 25 years of internal research, pioneering integrated photonics. The company says it was the first to develop and ship silicon photonics-based connectivity products with industry-leading reliability at high volume to major cloud service providers. Intel’s unique hybrid laser-on-wafer technology and direct integration enable superior performance and efficiency.
The OCI chiplet is currently a prototype, with Intel collaborating with select customers to co-package OCI with their SOCs as an optical I/O solution. As AI infrastructure continues to evolve, Intel’s innovations in high-speed data transmission and integrated photonics are poised to shape the future of connectivity, maintaining the company’s position at the forefront of technological advancement.
