This tells the admin exactly which optical wavelength this transceiver transmits and receives on, essential when the link runs over a wavelength-division-multiplexed system where plugging in an optic on the wrong wavelength for its assigned WDM channel will simply not connect, or will interfere with a neighboring channel. For example, a reading of 1310 nanometers confirms a standard single-wavelength optic appropriate for a direct fiber run, whereas a system expecting a specific DWDM channel wavelength like 1550.12 would need a very different, channel-specific optic.