EXFO FTB-800 Series for FTB-1 - Manual (Page 270)

Test Results
260 FTB-700G/800 Series
Alarms/Errors
Fibre Channel
Alarms

Link Down
RX: The Fibre Channel connection is down meaning that there is a
local or a remote fault condition.

LOS (Loss Of Signal)
RX: Absence of an input signal or an all-zeros pattern is received.

Frequency
RX: The received signal frequency meets the standard specifications
(green) or not (red). The frequency range is ± 100 ppm.
Error

Symbol
RX/TX: Invalid code-group is detected/generated in the code.

FCS (Frame Check Sequence)
RX: Frames with an invalid FCS are received.

Oversize (available when the Oversize Monitoring check box is
selected.)
RX: The number of received FL-2 frames larger than 2148 bytes with a
valid FCS.

Undersize
RX: FL-2 frames smaller than 36 bytes with a valid FCS.