JDS Uniphase DSAM-2600B, Quick Start Manual

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Chapter 2 DSAM Meter Operation
Using Measure Mode
DSAM Product Family Quick-Start Guide Rev. 001 39
–
Performing
DQI
Measurements
The measurement Digital Quality Index (DQI) is a real-
time measurement that immediately detects intermittent
issues and some sustained issues within a downstream
QAM stream. In comparison, the typical measurement
used to check for these issues on a digital QAM carrier is
the pre and post forward error correction (FEC) bit error
rate (BER). The BER measurement relies on actual errors
and is slow to detect many issues. The DQI measurement
uses error magnitude information from the output of the
demodulator, including error magnitudes that do not result
in errors. Measurement response is considerably faster
than BER or MER and more sensitive to transient and
intermittent issues that affect the stream.
To access DQI measurement mode, use the arrow keys to
highlight the DQI feature on the Measure mode menu.
(
Figure 15 on page 30 ), and press Enter . Or, while in the
Level mode, press View softkey and select DQI from the
list of options. The DQI mode screen will look similar to
Figure 28 on page 40 .
Figure 27 DOCSIS® 3.0 Throughput