What is the right way to cool a 51.2T NPO switch? A Celestica ITherm 2023 paper answers: cold-plate liquid cooling at 2 LPM leaves margin for both the ASIC and the OEs. The real bottleneck is not the 835W ASIC but the 16 optical engines capped at a 70°C case temperature.

The external laser source has gone from "one part inside a module" to a formal product category with specs, interoperability requirements and multiple competitors. Of the seven spec fields laid out at ECOC, power is just one; the real ticket is spec completeness and packaging throughput.

NPO is being treated as a long-term architecture not out of technical preference, but because of supply constraints. Separable architectures create component markets - and whether NPO or CPO wins, the laser stays outside the package.

Chasing every option would force optical module makers to develop more than 50 SKUs. And at 1,024 lanes, OSFP beachfront density is just 0.07 T/mm versus a 0.3 T/mm target — a gap of over 4x. Huawei argues NPO means redesigning the whole switch, from sockets and thermals to PI/SI.

Scoring three architectures on the same criteria, Ciena shows single-vendor CPO going from second-best to best on technology, but from efficient to at-risk on supply chain, because the ASIC and interconnect are sold as one unit. Open CPX's answer is not a better component but a socket that optics and copper share, and a spec written in under six months.

At ECOC 2026, Huawei did something the industry rarely does in public: score NPO and CPO dimension by dimension. NPO won four, CPO two. But the real signal is the ranking, not the score - with supernodes heading to 4,096 accelerators in 2027, "can it be swapped when it fails" is put ahead of "how many pJ per bit it saves" for the first time.