Optical modules connected by copper wires

Optical modules can be integrated with copper interconnects to combine high-speed optical transmission with the cost and flexibility of copper for short distances.

Overview

Optical modules convert electrical signals into optical signals for high-speed data transmission, often over longer distances where copper wires face bandwidth and signal integrity limitations . Copper wires remain widely used for short-range connections due to their low cost, reliability, and ease of installation, typically under 5 meters in data center racks . Hybrid systems allow designers to leverage both technologies, using copper for short, cost-sensitive links and optical fibers for high-bandwidth or long-distance connections.

Hybrid and Interchangeable Systems

Some modern interconnect systems, like Samtec's FireFly™ Micro Flyover System, provide flexibility to use either copper or optical cables with the same connector interface. This allows designers to optimize for cost, distance, or data rate without changing the board layout . These systems support data rates from 14 Gbps to 28 Gbps per lane, with optical paths extending to greater distances while copper is used for shorter, cost-effective links.

Co-Packaged and Near-Package Optics

Advanced approaches, such as Co-Packaged Optics (CPO) and Near-Package Optics (NPO), integrate optical components directly with electronic chips or ASICs. CPO places lasers and photodetectors alongside electrical components in the same package, reducing the distance between optical and electrical signals, improving bandwidth, and lowering power consumption . NPO positions the optical engine near the chip on the same PCB, maintaining short electrical paths while enhancing signal integrity and bandwidth utilization .

Active Copper and DSP Integration

For short-range copper connections, active electrical cables (AECs) and DSP-enhanced copper links improve bandwidth and signal quality. These solutions insert digital signal processors (DSPs) or retimers into copper connections to extend reach and maintain data integrity at higher speeds, bridging the gap between traditional copper limitations and optical performance .

Applications

• Data Centers: Hybrid copper-optical links are used for server-to-switch and switch-to-switch connections, balancing cost and performance .
• AI and HPC Clusters: Optical modules integrated with GPUs or memory packages enable high-bandwidth, low-latency communication over distances up to 2 km, often using wavelength-division multiplexing for multiple data lanes .
• Board-Level Interconnects: Mid-board optical transceivers allow chip-to-chip or board-to-board communication with high density and modularity, while copper can still be used for power and control signals .

Summary

Connecting optical modules with copper wires provides a flexible, scalable solution for modern high-speed computing environments. Copper remains cost-effective for short distances, while optical modules handle high-bandwidth or long-distance links. Hybrid systems, co-packaged optics, and DSP-enhanced copper links enable designers to optimize performance, energy efficiency, and density in data centers and AI clusters .