VeEX VEPAL CX350S-D3.1, Руководство пользователя

Страница: 31 / 114

Go back to top Go back to TOC
Equalized and Un-equalized MER measurements
Un-equalized MER is typically measured before the adaptive equalizer, and equalized MER is measured after the adaptive equalizer, but
often this circuitry resides in the QAM receiver and cannot be disabled. So while the adaptive equalizer does a great job of improving the
MER of a QAM signal, it makes troubleshooting marginal amplifiers, small ingress, CPD and related impairments a lot more difficult.
It is important to know how hard the adaptive equalizer is working to determine if there is any margin for system degradation. To solve this
problem, the CX380’s adaptive equalizer can be turned off, allowing a technician to easily identify, sectionalize and locate these difficult
linear type distortion problems. Tap the function of “Equalizer On/Off” to enable or disable the adaptive equalizer.
Tap Expert
By further analyzing the behavior of the equalizer taps, the following measurements can be performed:
Estimated Equalizer Stress
Estimated Un-equalized MER
Estimated Noise Margin
Estimated Echo margin
The measurement results provide an early indication that the system might have marginal performance, even though MER, pre-FEC errors
and post-FEC errors are acceptable.
Tap Expert
Go back to top Go back to TOC