400G ZR+ BiDi does not exist, it can't hurt you. Or can it?#

Nicola von Thadden (PFALZKOM), Arjan Koopen (i3D.net / Stichting EventInfra)

• Why: A creative, out-of-spec experiment building a 400G link over a single fiber pair using ZR+ optics — relevant to the PM's optics and DC interconnect interests as a proof of what's technically possible outside standards.
• What: For the WHY2025 hacker summer camp in the Netherlands, the speakers built a 400G link over a single fiber. Since 400G BiDi doesn't exist as a standard product, they built something out-of-spec using ZR+ coherent optics. (from abstract and page only — no slides available)
• How: Not specified in the abstract — presumably using two wavelengths (one per direction) with coherent ZR+ modules on a single fiber pair, a non-standard but functional configuration. The title's "Or can it?" suggests they'll discuss whether this out-of-spec approach caused problems.
• Where applicable: Limited direct applicability — this is a proof-of-concept in a temporary event network. But it demonstrates what coherent optics can tolerate outside their specified operating envelope, useful knowledge for DCI planning when fiber count is constrained. Event/non-profit network context.