FCM9002 USER MANUAL
76-02-095 Rev.B
Page 97 of 145
The fibre length measurement is made by the device when the link is established
and LOS has been negated. The measurement is made and provides an
estimate of the fibre length based on the most distant OTDR value. Accuracy of
the cable length is to /- 10m.
When a fault is reported, the cable length shown is the previous measured
length, and the length is recalculated when faults are cleared.
4.4.2.8.3.4 Last Fault Start
When a fault is first detected the time is displayed. If the measured distance
changes by greater then 50m, then a new fault is considered to have been
detected and the time will be updated.
Due to the nature of OTDR measurements, it is occasionally the case that during
the reconnection during fault repair, a new fault may be detected which is equal
to the cable length, though this will be clear due to the short elapsed time
between onset and clearance of the fault condition.
4.4.2.8.3.5 Last Fault Cleared
The time that the fault clears is recorded in the display. This time indicates that
the fault has been cleared and the link has a valid optical signal present.
4.4.2.8.3.6 Last Fault Distance
The last Fault Distance records the OTDR measured distance of the last fault
and will be maintained as a record unless a new fault is detected.
Due to the nature of OTDR measurements, it is occasionally the case that during
the reconnection during fault repair, a new fault may be detected which is equal
to the cable length, though this will be clear due to the short elapsed time
between onset and clearance of the fault condition.
