Optical networking is already widely used for scale-out connections across data centers, while low-latency scale-up links between GPUs inside a rack still rely primarily on copper technologies such as NVIDIA NVLink. As signaling speeds increase, copper links face greater attenuation, power consumption, and heat. NVIDIA plans to expand its tightly connected systems from 72 GPUs today to as many as 576 by 2027, and the company acknowledges that in-rack copper is approaching its physical limits. NVIDIA’s NVLink Fusion ecosystem now includes photonics companies such as Ayar Labs, Marvell, and Lightmatter. Ayar Labs is developing optical chiplets positioned beside processors, while Lightmatter is pursuing photonic interposers that can sit underneath compute chips. Improvements in foundry processes, hybrid bonding, packaging, and testing have made co-packaged optics more manufacturable. However, integrating large numbers of lasers efficiently and reliably remains a major challenge. NVIDIA is taking a gradual approach, adopting optics first in scale-out networks and potentially extending it into scale-up systems as bandwidth requirements increase. Industry participants expect multiple high-volume optical scale-up implementations around 2028, although this remains a forecast and copper is likely to coexist with optics for some time. --> Optical scale-up is being pursued through a wide range of architectures by multiple companies and engineering teams. Ayar Labs is developing optical chiplets, while Lightmatter is taking a photonic-interposer approach, and other implementations will continue to emerge. At this stage, predicting the eventual architectural winner is difficult. A more useful strategy is to focus on the common bottlenecks and chokepoints that every solution must pass through. As I have consistently argued, the two most critical layers in silicon photonics and co-packaged optics are packaging and measurement/testing. Optical devices, electronic chips, lasers, and fibers must be integrated with low loss, high yield, and sufficient reliability. Once assembled, both individual components and complete optical engines must also be tested at production speed and scale. As competition between architectures intensifies, these two layers are likely to determine which technologies can actually reach high-volume manufacturing.