If the fiber interface on the data Ethernet port is not OK, there are three possible causes: 1) the fiber interface has been installed but disabled, 2) the interface could not be established even though no LOS was detected (i.e. an optical carrier was detected, which could be due to a broken TX fiber, or because the interface is disabled at the other end of the fiber link), or 3) the interface could not be established and LOS is detected (i.e. no optical carrier is detected). NB: a change of status may generate an SNMP trap and/or SMTP email alert