The 400G-per-lane era is here. At OFC 2026, Coherent showed InP components with more than 100 GHz of bandwidth - but how do you keep TDECQ low while absorbing a 5 dB sensitivity penalty? A deep dive into the technical and commercial tradeoffs of IM/DD for AI interconnects.

At 1.6T, choosing IMDD no longer buys you lower power — only shorter reach. With a reach-collapse chart and a standards matrix full of "Undefined," Nokia argues the real 1600G+ problem isn't physics but too many options and an industry slow to converge.

The optics problem at 400G/lane is essentially solved; what remains is electrical, packaging and connectors. Coherent pinpointed the bottlenecks: wire bonds collapse above 110 GHz, OSFP connectors dip at 90 GHz, and PAM6 in optics hits an SNR wall. IM/DD can stretch to 800G, but it needs electronics, not photonics.