Fluke Networks CertiFiber Pro Users Manual - Manual (Page 121)

Chapter 3: How to Certify Twisted Pair Cabling
Twisted Pair Autotest Results
99
NEXT (Near-End Crosstalk)
NEXT results show the crosstalk attenuation between wire pairs.
NEXT is the difference in amplitude (in dB) between a transmitted
signal and the crosstalk received on other wire pairs at the same
end of the cabling. Higher NEXT values correspond to larger
differences between the amplitudes of the transmitted signals
and the crosstalk, which corresponds to better cabling
performance. Figure 45 shows the NEXT plot. The tester puts the
cursor at the worst margin.
Note
If the NEXT result is an an , the 4 dB rule applies.
See “About dB Rules” on page 116.
Because of insertion loss, crosstalk signals occurring farther from
the signal source are weaker and cause less trouble than crosstalk
nearer the source (Figure 45). For this reason, the tester measures
NEXT from both ends of the cabling.
For NEXT failures, you can use the HDTDX analyzer plot to locate
cause of the failure. See “The HDTDR Analyzer” on page 135.
GPU82.EPS
Figure 45. Near-End Crosstalk (NEXT)
Signal
input
Crosstalk near
the source
Crosstalk
farther from
the source
NEXT