EXFO VDSL2 - Manual (Page 98)

Fault Location Tests
90 AXS-200/635
TDR Test
Test Setup
The Test Setup tab allows you to
configure parameters for the TDR test.
VOP sets the velocity of propagation for
the cable as a ratio of the speed
of light.
Note: The default VOP is good for most
cables; only change it when you know
the correct VOP for the cable you are
measuring. An incorrect VOP will cause
distance errors.
TDR
The TDR test first attempts to find the
length of the circuit and then searches
all ranges from shortest to longest for
significant events. Upon completion,
the test selects the nearest major
event, sets the range to match, and
aligns the cursor with the event.
Est is the estimated length of the
circuit.