This value indicates whether the port's multiple signaling lanes are carried on separate physical fibers or as different wavelengths on a single fiber. Admins use it to understand the port's optical architecture: fiber(2) means each lane has its own strand, while lambda(3) means all lanes are wavelength-multiplexed onto one single-mode fiber. For example, a CWDM-based CFP port would report lambda(3), while a parallel-fiber QSFP+ port would report fiber(2).