CMRL (Common Mode Return Loss) - DSX CableAnalyzer
CMRL is a measurement of interest to those developing systems beyond 10GBASE-T.
There are no test limits in ANSI/TIA-568-C.2, ANSI/TIA-1005 or ISO/IEC 11801:2010.
The measurement is made by injecting a common mode signal (CM) into one twisted pair, then measuring the CM signal returned on that same pair. The smaller the CM signal returned, the better the CMRL.
If it looks similar to a Return Loss measurement, you're right. Except a Return Loss measurement is made by injecting a DM signal onto one pair and measuring the DM signal returned on the same.
Other balance measurements such as TCL, ELTCTL and CDNEXT are also available in the DSX-5000 CableAnalyzer.
If you wish to add CMRL to your standard Category 5e, 6, 6A or Class D, E or EA test, select your test limit with a suffix of (+ALL):
This will increase your AUTOTEST time.
The suffix of (+All) indicates a standard ANSI/TIA or ISO/IEC test with the addition of ELTCTL, TCL, Resistance Unbalance within a pair, Resistance Unbalance between pairs, CMRL and CDNEXT measurements.
In the example below from a DSX-5000 CableAnalyzer, a Category 6A Channel was tested.