Why Optical Circuit Switches Are No Longer Optional in the AI Era

In 2025, as the explosive growth of AI compute demand continues unabated, data center networks are facing unprecedented pressure. Traditional electrical packet switches are increasingly exposed to severe limitations in bandwidth, power consumption, and reliability when handling massive east-west traffic. Against this backdrop, optical circuit switches (OCS), with their unique advantages in bandwidth scalability, energy efficiency, flat network architecture evolution, and fault tolerance, have become the key enabling technology for next-generation data center network upgrades.

Part I: The Evolution from Hierarchical to Flat Architecture and the Rise of Optical Switching
For the past two decades, the vast majority of data centers have relied on the classic three-tier “Core-Aggregation-Access” tree topology (with Spine-Leaf being merely a partial optimization). This architecture worked reasonably well when traffic patterns were predictable and east-west traffic was moderate. However, large-scale AI training has completely overturned the status quo:
• A single AllReduce operation in a 100,000-GPU cluster can generate instantaneous traffic in the tens of petabytes per second.
• Training a trillion-parameter model requires exchanging exabytes of data among GPUs.
• A single link flap or packet drop can force the entire cluster to roll back hours or even days of progress.

Under these extreme conditions, the three fatal weaknesses of traditional electrical switching become impossible to ignore:
• Port speed is fundamentally constrained by silicon process nodes; 800G electrical ports only entered volume production in 2025, while 1.6T remains years away.
• Every O/E/O conversion consumes 3–5 W per 100 Gbps; in a 100,000-GPU cluster, conversion alone can waste hundreds of megawatts.
• Implementing 1+1 electrical redundancy doubles equipment, power, and rack space, while protection switching typically takes 50 ms or more—unacceptable for AI training.
It is precisely under these pressures that the industry has turned its attention to all-optical switching. Among all optical switching technologies, optical circuit switches—especially MEMS-based OCS—stand out as the most mature, cost-effective, and immediately deployable solution.

Part II: Four Killer Advantages of Optical Circuit Switches in Data Centers
Advantage 1: Turning Bandwidth from “Scarce Resource” into “Nearly Unlimited”
Light is not limited by electron mobility or the skin effect in copper. In theory, a single fiber can exceed 100 Tbps (already demonstrated in labs). Optical circuit switches turn this theoretical potential into engineering reality.
Take mainstream MEMS optical switches as an example:
• Typical insertion loss: 0.5–1.0 dB
• Full C+L band support (1260–1670 nm)
• Combined with DWDM, a single fiber can carry 96–128 wavelengths
• Each wavelength supports 400G (coherent) or 800G (IM-DD), pushing total fiber capacity beyond 30–50 Tbps

Compare this with traditional gray optics:
• 400G gray optics requires 4 fibers (4×100G PAM4)
• 800G requires 8 fibers
• 1.6T requires 16 fibers

Fiber count explodes, driving up jumper cables, splicing points, cabinet space, and deployment complexity. With the “colored optics + OCS” approach, however:
One fiber + one optical switch = a tens-of-Tbps dynamically allocatable bandwidth pool.
Real-world deployment: In late 2024, a leading cloud provider built an AI supercomputing cluster where the core interconnection layer adopted 1×64 MEMS OCS arrays. Fiber count per rack dropped from over 3,000 to under 400, reducing jumper installation time by 85%. Future capacity expansion only requires adding wavelengths—no rewiring needed.

Advantage 2: Making PUE Drop from 2.0 to the 1.X Era Possible
In 2025, the electricity bill for training a trillion-parameter model is now on par with—or even exceeds—the cost of the GPUs themselves. Google, Microsoft, and Meta have all committed to carbon neutrality by 2030; energy efficiency has become a matter of survival.
Optical switches deliver a “dimensionality-reducing blow” to power consumption:
• Eliminate O/E/O conversion power entirely
A traditional 100G electrical switch port consumes 15–25 W, while an optical switch port consumes only tens of milliwatts. In a 100,000-H100 cluster, removing optoelectronic conversion alone saves nearly 10 MW—equivalent to nearly 100 million RMB in annual electricity costs.
• Truly zero-power standby
Latching MEMS switches maintain their optical state even when power is removed. During low-traffic periods, all control electronics can be shut down completely.
• Dramatically reduced cooling ""
Real measurements show that all-optical AI clusters reduce heat dissipation by 35–42%, cutting air-conditioning power proportionally.

Real case: In Q1 2025, a major Chinese internet company completed an optical network upgrade. After replacing the core switching layer with MEMS OCS matrices, the data center’s PUE dropped from 1.58 to 1.19, saving approximately 28 million RMB in annual energy costs.
Advantage 3: Transforming Compute Scheduling from Static to Real-Time Fluid Al
One of the biggest pain points in AI training is resource fragmentation: one job may require exclusive access to 80,000 GPUs, while another needs only 2,000. Fixed electrical topologies cannot adapt.

Optical switches enable true optical-layer SDN:
• Millisecond-level topology reconfiguration: typical MEMS switching time 2–15 ms
• Non-blocking any-to-any connectivity via large-scale matrices (128×128, 256×256, etc.)
• Granular on-demand bandwidth al (100G/200G/400G steps) when paired with tunable lasers

Results observed:
• GPU utilization rises from 45–55% to 85–93%
• Average training time for a 175B model reduced by 17%
• Multiple training jobs of different scales can run concurrently without conflict

NVIDIA explicitly listed optical circuit switches as a recommended interconnect component in its 2024 DGX GB200 NVL72 system, stating: “Only optical circuit switches can meet the full-mesh, non-blocking, ultra-low-latency communication requirements among 72 GPUs.”
Advantage 4: Pushing Network Availability from 99.99% to 99.9999%

In AI training, a single network outage can cost millions of dollars.
Optical switches improve reliability on three levels:
• Ultra-fast protection switching
Leading MEMS switches achieve ≤5 ms protection switching—ten times faster than the 50–200 ms of electrical switches. For a 100,000-GPU cluster, 5 ms is virtually imperceptible, while 50 ms triggers widespread timeouts.

• Extremely low-cost 1+1/1:1 optical protection
Electrical redundancy requires double the equipment, power, and space. Optical protection only requires duplicate fibers plus switches—negligible additional power and footprint.

• Inherently high reliability
The passive optical path lasts over 20 years; micro-mirrors exceed 10 billion cycles. Products pass the harshest Telcordia GR-1221/GR-1073 tests and operate stably from –40 °C to +85 °C.

Real case: In 2025, a major Chinese securities firm upgraded its core trading system with optical-layer protection. Failover time dropped from 48 ms to 4.3 ms, and network-related trading anomalies fell from 27 incidents per year to zero, preventing losses exceeding 300 million RMB.

Conclusion: Optical Circuit Switches Are No Longer Optional—They Are Mandatory
In 2025, data center networks are no longer just “infrastructure that works.” They have become the core competitive factor determining the success or failure of AI training and the survival of enterprises.
• Without 800G/1.6T bandwidth, you cannot even build a 10,000-GPU cluster.
• Without extreme energy efficiency, electricity bills will devour all profits.
• Without dynamic scheduling, GPU utilization will never exceed 80%.
• Without 5 ms protection, a single failure can wipe out an entire training run.
Optical circuit switches solve all four of these critical problems—at once.

In this sense, optical circuit switches are no longer an optional enhancement; they have become a mandatory technology. Quietly but irresistibly, they are becoming one of the hardest core foundations of the AI infrastructure era.

Over the next decade, any player still relying solely on electrical switches to support clusters larger than 10,000 GPUs will inevitably be eliminated. Those who embrace all-optical interconnects and optical circuit switches first have already seized the winning position. Light is redefining the boundaries of compute power. And the optical circuit switch is the key that unlocks that door.