Nvidia temporarily abandons TSMC’s COUPE optical solution! Switch to Tower silicon photonics, and the reason for exiting Plan A is revealed

Nvidia temporarily shelved TSMC’s COUPE (Compact Universal Photonic Engine) co-packaged optics approach and instead switched to Tower Semiconductor’s silicon photonics platform. TSMC’s delay in developing its titanium nitride (SiN) PDK and a mistake in the 2D grating coupler design forced Nvidia to initiate Plan B.
(Background recap: Nvidia’s 800V power delivery revolution isn’t delayed! Confirmed with Delta Electronics and ABB partners: Q3 on-time mass production)
(Background addition: Intel fell from the semiconductor kingpin throne, sought TSMC for foundry services, and in the end ended up being urged to get acquired by Qualcomm—how did it lose with so many good cards in hand?)

Table of Contents

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• Plan A exits: TSMC co-packaged optics route
• Plan B steps in: Tower Semiconductor silicon photonics route
• The significance for Taiwan’s semiconductor supply chain

Nvidia has decided to temporarily give up TSMC’s COUPE (Compact Universal Photonic Engine) co-packaged optics solution and instead use Tower Semiconductor’s silicon photonics platform. The reason is that TSMC’s progress in advancing titanium nitride (SiN) technology has been slow, and the development of the 2D grating coupler has not met expectations.

Plan A exits: TSMC co-packaged optics route

According to engineering analysis from Irrational Analysis, Nvidia’s original “Plan A” was a co-packaged optics (CPO) approach on TSMC’s COUPE platform, using a 50-64G NRZ low-speed broadband and an 8-wavelength DWDM architecture.

CPO technology directly packages the laser next to the switching chip, significantly shortening the distance for optical signal transmission, while reducing power consumption and signal loss. TSMC’s COUPE platform was originally viewed as a core element of Nvidia’s next-generation network architecture, but two key technological bottlenecks have slowed progress:

• Titanium nitride (SiN) PDK development delays — TSMC’s silicon photonics process design kit (PDK) is delayed, affecting downstream customers’ circuit design schedules
• 2D grating coupler misstep — the development of high-density 2D grating couplers did not reach specifications, directly impacting the optical signal coupling efficiency

Plan B steps in: Tower Semiconductor silicon photonics route

Nvidia has moved the project to Tower Semiconductor’s silicon photonics (SiPho) platform, switching to the NPO (Near-Photonics Optics) architecture:

• 200G / 400G PAM4 modulation — replacing the original 50-64G NRZ
• 16-wavelength DWDM — doubling the 8 wavelengths of Plan A to compensate for NPO’s lower frequency bandwidth efficiency
• Stronger electrical SerDes — because the NPO electrical channels are longer and have more reflections (bump capacitance is a key factor), it requires a more powerful equalizer (EQ) and driver

However, the Tower solution also comes with two costs:

• Lower channel density — more wavelengths are needed to achieve the same bandwidth
• Worse power efficiency — the power and noise requirements for grating lasers rise exponentially, increasing SNR requirements and further burdening the laser

The significance for Taiwan’s semiconductor supply chain

This news reflects the competitive pressure on TSMC in the silicon photonics race. COUPE is TSMC’s self-developed universal photonic engine platform, aiming to standardize and make optical components as interchangeable as transistors. If development is delayed, Nvidia’s network architecture timeline will be directly affected.

It’s also worth noting that TSMC’s COUPE platform is not only being used by Nvidia—multiple AI chip design companies are evaluating TSMC’s silicon photonics process as well. The delay in the SiN PDK means downstream design schedules will shift back in sync.

On the other hand, Tower Semiconductor, as the semiconductor foundry under Infineon (Infineon), draws its silicon photonics technology from years of optical-electronic integrated circuit R&D in Germany, with especially mature mass-production experience in Datacom and Telecom areas. Nvidia’s pivot to Tower indicates that the silicon photonics race is not monopolized by TSMC alone.