Laser Demand Is Counted in Wavelengths, Not Units: OCP's 204.8T Fiber and Laser Bill Shows DWDM Could Cut External Laser Modules 8x

The market usually sizes the CPO laser opportunity as switch units times external laser source modules (ELSFPs) per switch, times unit price. Broadcom's Tomahawk 6 Davisson, in volume production today, puts 16 6.4T DR optical engines on a 102.4T switch, so the math looks fine.

In July, OCP released "Architecture Vision: Open Silicon Photonics for AI Systems," which itemizes the fiber, connector, and laser bill for a 204.8T switch.

For the same 204.8T switch, DR needs 2,048 fibers and 32 ELSFPs; OCI needs 1,024 fibers and 32 ELSFPs; DWDM 8+8 needs just 128 fibers and 4 ELSFPs. That is a 16x gap in fiber and an 8x gap in external laser modules.

STT's view: the size of the laser opportunity depends on how fiber converges, not on how many switches ship.

▲ Fiber and ELSFP counts for the same 204.8T switch under three convergence schemes: DR, OCI, and DWDM 8+8 (Source: OCP Architecture Vision: Open Silicon Photonics for AI Systems v1.0.6 (2026/07), Table P)

For background, start with our free piece "The Switch Breaks Before the GPU: Three Counterintuitive Takeaways from OCP's Open Silicon Photonics White Paper," and the external laser source specs we compiled in ECOC Draws the Spec Line for ELS.

Inside the Paid Edition

• The market's standard formula, and why analyst estimates differ by an order of magnitude

• Full bill of materials and tray counts for the three 204.8T convergence schemes

• Mechanical breakdown: DR needs 3 tray layers, DWDM only 1

• Laser power breakdown: ring modulators save about 3 dB, and what that means for the 400 mW laser premium

• Reliability breakdown: why there is a floor on ELSFP count

• Market sizing: how many ELSFPs every 100,000 204.8T switches need, and what they are worth

• What competitors' roadmaps tell us: NVIDIA, Coherent, Huawei, Broadcom

• Taiwan supply chain mapped link by link, and the two real bottlenecks

• Counterarguments and 6 signals to track

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That's the summary of this piece.

STT's full analysis (ELSFP demand per 100,000 switches, laser power and reliability breakdowns, and a map of Taiwan's CW laser and FAU supply chain) is in the paid edition, with 5 original charts.

👉 Subscribe to STT Premium and read the full analysis on vocus (in Chinese): https://vocus.cc/article/6ad05e64fd89780001c629a4

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