GlobalFoundries Thomas Barber: CPO, Silicon Photonics, 300mm, SiGe, OCI, NRZ

The physical limits of copper are forcing a shift to optical interconnects in AI data centers. Austin sits down with GlobalFoundries' Thomas Barber to unpack why GF thinks it can lead that transition twice over: once with its long-running silicon photonics platform, and again with the specialty Silicon Germanium process the industry needs to drive it.
"The enemy to me right now is copper. I'm trying to beat copper, right? If TSMC wins and we win, that's great because we're both displacing copper. And until all the copper is gone, there's plenty of market to go around."
— Thomas Barber, GlobalFoundries
Key Takeaways:
- Copper's usable range halves every time the data rate doubles, and 200 Gbps/lane inside a rack-scale AI cluster is already past the point copper can handle.
- CPO's real win isn't speed, it's power: saving 20-25 pJ/bit frees part of a data center's fixed 50-100 MW budget to go toward compute instead of moving bits.
- GlobalFoundries leads photonics revenue for an unglamorous reason: it moved to 300mm wafers early, which yields 2.25x more die per wafer than the 200mm lines rivals still run.
- CPO can end up more reliable than the pluggables it's replacing, not less, because it deletes the physical plug connector, and dust at that connector is the leading cause of field failures.
- The OCI MSA picks NRZ over faster PAM4, deliberately going wide and slow, because NRZ's native bit error rate is a million times lower, which simplifies the receiver and cuts power.
- GlobalFoundries stacks two specialty processes into one edge: micro-mirror couplers on the photonic side, and Silicon Germanium transistors hitting 350-400 GHz on the electrical side driving them.
- The real competitor for silicon photonics isn't another foundry, it's copper itself — and that market is big enough that GlobalFoundries and TSMC can both win without taking share from each other.
Chapters:
0:00 GlobalFoundries in Photonics
1:21 GF's Photonics Strategy
3:02 GF's Market Leadership
5:06 300mm Wafer Advantage
6:55 Copper's Range Limits
9:18 Pluggable to CPO
13:48 CPO Reliability
19:22 OCI MSA Explained
26:20 GF's Scale Platform
29:04 Micro Mirror Technology
31:32 Photonics vs. Copper
38:25 Silicon Germanium Advantage
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