Copper vs Optical in the AI Infrastructure Buildout

The Interconnect Debate

As AI-driven data center buildouts accelerate, the debate around interconnect technology has taken center stage. For decades, copper wiring has been the backbone of data transmission, favored for its reliability, cost efficiency, and ease of deployment. Traditional data centers were architected around these strengths, with copper interconnects effectively supporting server-to-server communication across limited distances. However, as compute power has scales due to the rise of AI workloads, the limitations of copper have become more apparent as higher data rates increase signal loss, power consumption, and thermal constraint bottlenecks in data systems. As a result of copper’s bottleneck in more complex systems, optical technology has emerged as a critical complement. Optical interconnects, which transmit data using light rather than electrical signals, offering increased bandwidth capacity and improved efficiency making them highly attractive for scaling AI workloads.¹

These advantages are becoming increasingly important as AI infrastructure evolves from localized compute environments to large, distributed clusters requiring seamless, high-speed communication. While some narratives suggest optical will eventually replace copper, insights and industry data from OFC 2026 emphasize that the industry is moving toward “interconnect heterogeneity,” where multiple technologies coexist and are deployed based on distance, cost, and performance requirements.

The Scale of the AI Buildout Demands Interconnectivity

What makes this transition so important is the sheer magnitude of the AI infrastructure buildout now underway. The data center and AI ecosystem is expanding at an unprecedented pace, with hyperscalers expected to spend over $761 billion on data centers and AI infrastructure in 2026.² This represents a dramatic acceleration from prior years, with total hyperscaler capex up 70% year-over-year, and roughly 75% of that spend (~$450 billion) directed specifically toward AI infrastructure.³ Due to the rapid pace of development in data centers, networking infrastructure is becoming a critical bottleneck and a growing share of total spend. This surge is being driven by the exponential increase in AI-related data movement, particularly east-west traffic within clusters, which is forcing a step-change in interconnect performance. At the same time, the opportunity set for interconnect technologies is expanding rapidly. The total addressable market for short-reach copper cables (under 3 meters) is projected to exceed $10 billion by 2029, highlighting the continued scale of copper demand even in a higher-speed environment.⁴ In parallel, the optical cable market for AI data centers is expected to grow more than threefold to 5.4 million units by 2029, reflecting accelerating adoption as clusters scale and distances increase.⁵ These figures underscore that this is not a substitution cycle, but rather a broad expansion across both technologies.

Existing and New Data Center Buildout Scale Map⁶

The Bandwidth Arms Race is Driving Network Evolution

At the core of the datacenter buildout is a rapid escalation in bandwidth requirements. AI clusters are driving a surge in internal data traffic, requiring interconnect speeds to scale from 100G to 200G and now toward 400G and beyond.⁷ This is fundamentally changing how networks are architected, with performance increasingly dependent on data movement rather than just compute. As bandwidth increases, the network naturally segments based on distance as it becomes more important to match the right technology to the right layer of the network.

Copper-based solutions such as direct attach cables (DACs) and active electrical cables (AECs) are expected to remain the preferred choice for intra-rack connectivity due to their lower cost, better total cost of ownership, and higher reliability. Broadcom’s CEO Hock Tan reinforced this view, noting that optical solutions can be more expensive and require more power at the system level, and that copper can scale from 100G to 400G per lane within a rack before more advanced solutions are required.⁸ This is consistent with broader industry sentiment, where companies such as NVIDIA, Broadcom, and OpenAI expect copper to remain the primary interconnect within the rack well into the next decade.⁹

While copper remains dominant at short distances, optical is becoming increasingly critical as networks scale beyond the rack. Optical fiber is now the preferred solution for mid- to long-reach connections (over 3 meters) due to its ability to handle significantly higher bandwidth and support the growing size and density of AI data centers. Optical segment growth is projected at approximately 21% through 2026, supported by continued data center expansion.¹⁰ Power efficiency is also becoming a critical factor in this transition. Optical fiber consumes significantly less power at scale and generates no heat, making it more suitable for large, distributed systems. This is driving a secular shift toward optical interconnects, particularly as AI workloads increase server-to-server traffic and require more efficient data movement. However, optical pluggables are at least three times more expensive than copper cables, while also exhibiting higher failure rates.¹¹ These increased costs are related to unique connector hardware and specialized installation labor increasing installation costs. These setbacks diminish many of the gains benefited from a transition to optics, keeping copper from being displaced for the foreseeable future. This transition is also being driven by architectural changes, specifically the move from single-rack systems to multi-rack clusters, which is expected to play out over a multi-year period extending into the latter part of the decade.

Higher Bandwidth is Driving a Hybrid Architecture

The increase in bandwidth requirements is not leading to the replacement of copper with optical, but rather to a more segmented and optimized network architecture. Both technologies are expected to coexist, with increasing interconnect heterogeneity across the stack as passive copper, active copper, pluggable optics, and co-packaged optics each play a role. Hybrid architecture is already emerging, combining optical interconnects for longer distances with short-reach copper solutions within the rack. This approach serves as a bridge toward more optical-heavy designs over time, while maintaining the cost and efficiency benefits of copper in the near term.

Rather than a zero-sum transition, the industry is moving toward a complementary, hybrid model where both technologies evolve together. As AI networks expand in size and complexity, the future of interconnects will not be defined by replacement, but by strategic integration across a rapidly scaling infrastructure landscape.

Copper vs Fiber Optics Comparisons Chart¹²

Sources:

1. Mizuho Analyst Note, As of April 14, 2026 ↩︎
2. Bloomberg Intelligence, As of March 16, 2026 ↩︎
3. Deutsche Bank Analyst Note, As of December 14, 2025 ↩︎
4. Mizuho Analyst Note, As of April 14, 2026 ↩︎
5. Mizuho Analyst Note, As of April 14, 2026 ↩︎
6. Mizuho Analyst Note, As of December 4, 2025 ↩︎
7. Barclays Analyst Note, As of March 23, 2026 ↩︎
8. AVGO Q1 ’26 Earnings Call, as of March 4, 2026 ↩︎
9. Needham Analyst Note, As of March 27, 2026 ↩︎
10. Wells Fargo Analyst Note, As of April 8, 2026 ↩︎
11. Mizuho Analyst Note, As of April 14, 2026 ↩︎
12. FiberOpticx, As of January 9, 2024 ↩︎

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