As AI models and data center workloads continue to scale at an unprecedented pace, PCI Express (PCIe) is undergoing its most profound transformation since its introduction over two decades ago. The long-standing reliance on copper signaling is giving way to optical interconnects, fundamentally reshaping how GPUs, accelerators, and memory systems are connected.
By late 2025, optical PCIe has moved beyond research prototypes into early production deployments—becoming a critical enabler for large-scale AI and HPC infrastructure.
🚧 The Copper Wall: Why Optics Are Inevitable #
Since PCIe’s debut in 2000, each generation has doubled bandwidth while retaining copper as the physical medium. With PCIe 7.0, that strategy reaches its physical limit.
At 128 GT/s per lane, copper traces and cables struggle to maintain signal integrity beyond approximately one meter without heavy retiming, increased power draw, and added latency. Even with advanced equalization, copper becomes an inefficient solution at these speeds.
Optical signaling removes these constraints by eliminating electrical loss, enabling longer reach and improved energy efficiency—precisely what large GPU clusters require.
⚙️ PCIe 7.0: Built for Extreme Bandwidth #
Officially released in June 2025, PCIe 7.0 targets the most demanding workloads in AI, HPC, networking, and emerging quantum systems.
Key technical advances include:
- 128 GT/s per Lane: A full 2× increase over PCIe 6.0.
- PAM4 Signaling: Allowing higher data density without proportional increases in clock frequency.
- Optical-Aware Retimer ECN: The first standardized mechanism enabling PCIe links to transition cleanly from electrical to optical domains.
| Feature | PCIe 6.0 | PCIe 7.0 |
|---|---|---|
| Raw Data Rate | 64 GT/s | 128 GT/s |
| Bidirectional Bandwidth (x16) | 256 GB/s | 512 GB/s |
| Practical Copper Reach | ~2 m | < 1 m |
| Optical Reach | ~100 m | 100 m+ |
PCIe 7.0 is not merely faster—it is explicitly designed to coexist with optical transport.
🛣️ CopprLink vs. Optics: A Dual-Path Strategy #
Rather than forcing a single solution, PCI-SIG is advancing a two-path ecosystem.
-
CopprLink
- Optimized for short-distance connections.
- Targets up to 1 meter internal and 2 meters external cabling.
- Best suited for intra-rack and chassis-level connectivity.
-
Optical Interconnects
- Developed under the Optical Working Group (OWG).
- Supports pluggable optics, onboard optics, and Co-Packaged Optics (CPO).
- Enables connections spanning entire rows or rooms within a data center.
This approach allows system designers to balance cost, power, and reach depending on deployment scale.
🚀 Industry Momentum in 2025 #
Throughout 2025, the ecosystem demonstrated rapid progress toward production-ready optical PCIe.
⚡ Connectivity Leaders: Marvell & Astera Labs #
- Marvell showcased the industry’s first end-to-end PCIe Gen 6 over optics at OFC 2025, validating low-latency scaling for AI fabrics.
- Astera Labs demonstrated Scorpio P-Series PCIe switches at OCP 2025, enabling optical multi-rack GPU clusters with integrated telemetry.
🧪 IP and EDA Leaders: Cadence & Synopsys #
- Cadence successfully demonstrated a stable 128 GT/s PCIe 7.0 link over Linear Pluggable Optics (LPO) without retimers, exceeding BER requirements.
- Synopsys, in collaboration with OpenLight, showcased PCIe 7.0 data-rate-over-optics using a linear-drive architecture that significantly reduces power and latency.
These demonstrations substantially lower adoption risk for silicon vendors.
🏭 Intel and Integrated Photonics #
Intel continues to lead in silicon photonics integration. Its Optical Compute Interconnect (OCI) chiplet—co-packaged with CPUs and GPUs—supports 64 lanes of PCIe connectivity.
By late 2025, Intel demonstrated:
- 4 Tbps bidirectional bandwidth
- 100-meter fiber reach
- Energy efficiency of approximately 5 pJ/bit
This level of efficiency is difficult to achieve with traditional pluggable optical modules.
🧠 CXL and Optical Memory Disaggregation #
The implications extend well beyond GPU connectivity. CXL, built on the PCIe physical layer, is emerging as a major beneficiary of optical transport.
- CXL-over-Optics: Demonstrated by vendors such as Rambus and Kioxia, enabling memory pools located up to 40 meters away.
- Latency: Sub-microsecond access times, suitable for memory expansion and pooling.
- Architectural Impact: Reduces stranded memory and allows dynamic allocation of DRAM and emerging memory technologies across servers.
Optical PCIe transforms memory from a local constraint into a shared data center resource.
🔮 The Road Ahead #
Copper-based PCIe is not disappearing—but its role is becoming localized. Short-reach CopprLink connections will dominate inside racks, while optical PCIe 7.0 enables scale-out architectures spanning hundreds of meters.
By breaking the distance and power barriers simultaneously, optical interconnects are turning the modern data center into a single, fluid compute fabric—a foundational shift for AI superclusters, disaggregated memory, and next-generation accelerator platforms.
PCIe’s future is no longer just faster—it is fundamentally optical.