Co-packaged optical and memory chips

Co-packaged optical and memory chips integrate optical interconnects directly with processing or memory units to dramatically increase bandwidth, reduce latency, and improve energy efficiency in AI and data center systems.

Overview

Co-packaged optics (CPO) involves placing optical engines or photonic integrated circuits (PICs) directly adjacent to or within the same package as electronic ICs, such as GPUs, switch ASICs, or memory modules . This approach collapses traditional electrical interconnect distances from inches to millimeters, significantly reducing power consumption, signal loss, and latency while increasing bandwidth density . In AI and ML workloads, where multi-terabit data rates are required, CPO enables tightly coupled clusters of processors to communicate efficiently as a single logical system.

Integration with Memory

In next-generation architectures, memory and compute units can be disaggregated but connected via co-packaged optical links . This allows memory modules to be physically separated from processors while maintaining ultra-low latency and high-throughput communication, which is critical for large-scale AI/ML training and inference. Optical interconnects can deliver hundreds of terabits per second per die, far exceeding the capabilities of traditional copper-based links .

Benefits

• High Bandwidth: Optical links provide much higher data rates than copper, supporting multi-Tb/s interconnects .
• Energy Efficiency: By reducing electrical distances, CPO can lower link power consumption significantly (e.g., from 30 W to 9 W per link in some 1.6T networks), .
• Scalability: Supports large-scale AI clusters with millions of endpoints without excessive power or thermal overhead .
• Thermal Management: Stacking PICs and electronic ICs with careful placement improves heat dissipation and signal integrity .

Design Considerations

• Packaging Complexity: Co-packaging requires advanced 2.5D interposers, hybrid bonding, and precise optical coupling .
• Thermal Isolation: Optical engines may need mini heat sinks or spacing to allow airflow or cold plates to reach them .
• System Co-Optimization: Electrical, optical, thermal, and packaging parameters must be evaluated together early in the design phase .
• Interoperability: Standardization challenges exist when mixing different optical types or vendors .

Future Directions

CPO is expected to grow exponentially in AI data centers, with optical transceiver sales projected to more than double by 2029 . Emerging trends include glass-based substrates for improved mechanical and thermal properties, femtosecond laser processing for precise optical structures, and integration with disaggregated memory systems to maximize AI/ML performance . These developments aim to overcome the limitations of copper interconnects and enable sub-pJ/bit energy efficiency for next-generation computing systems. In summary, co-packaged optical and memory chips represent a transformative approach to high-performance computing, combining optical interconnects with memory and processing units to achieve unprecedented bandwidth, low latency, and energy efficiency, while posing new challenges in packaging, thermal management, and system design.