OS2
A low-attenuation single-mode optical-cabling category. Achievable reach and upgrade reuse still depend on link budget, wavelength, optic class, connectors/splices, dispersion, fiber condition, and qualification—not a generation-agnostic or transceiver-only guarantee.
Current numbers
16 fibers800GBASE-DR8 over MPO-16/OS2: eight parallel single-mode lanes / 16 fibers; later reuse requires an application-specific qualified migration map