Ghost reflections can appear when testing through
bridged taps. Referring to Figure 6a, it appears as
though there is a partial open at Point E. This cannot be
true as the cable physically ends at Point D. Referring to
the cable plant layout in Figure 6b, the ghost is caused
when the signal
returning
from Point D passes Point B.
The signal splits, some energy returning straight to the
TDR (Point D) and some energy traveling down the
lateral, reflecting from the end and returning to the TDR
(Point E)
after
the reflection of the end of the cable.
Figure 6a
A
B C
D
Figure 6b