Cmrl (Common-Mode Return Loss) - Fluke Versiv Series Technical Reference Handbook

Versiv Series Cabling Certification Product Family
Technical Reference Handbook

CMRL (Common-Mode Return Loss)

Common-mode return loss is the difference (in dB) between the
power of a common-mode signal applied to a wire pair and the
power of the common-mode signal reflected back on the same
pair. The reflections are caused by variations in the cable's
impedance. Smaller reflected signals correspond to better CMRL.
CMRL is similar to return loss, except that return loss is measured
by applying a differential-mode signal to one pair and measuring
the differential-mode signal reflected back on the same pair.
At the time this manual was released, no test standards required
CMRL measurements. The CMRL test is available for
troubleshooting purposes, and is useful when developing systems
above 10GBASE-T.
Figure 64 shows the CMRL plot.
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