Atec JDSU-DSM-6300 - Manual (Page 2)

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DSAM-6300 DigitAl Service AnAlySiS Meter
The level mode on a digital channel measures
the signal level and MER and tracks the BER and
errored seconds.
Signal Level Meter
The DSAM-6300 features extremely accurate JDSU digiCheck™ digital power
level measurements in addition to traditional signal level measurement (SLM)
test functions for analog video and audio levels. In addition to the standard analog
carrier-to-noise (C/N) measurement, a quadrature amplitude modulation (QAM)
ingress option enables viewing noise and ingress within the QAM signal spectrum.
The DSAM-6300 can measure downstream carriers to a full 1 GHz and analyze
64, 128, and 256 QAM including deep interleave (i=128, j=4) modulation. Also
included are modulation error ratio (MER) and pre- and post-FEC bit error rate
(BER), margin, and quality specifications.
Miniscan and Full Scan Modes
When measuring analog and digital signals, technicians can see high- and low-
frequency channels and verify how much level headroom remains when limits are
activated. In miniscan mode, the DSAM monitors up to 12 channels at a time and in
full scan mode it monitors the entire channel plan—up to 999 channels. The results
of both scans are displayed in either an easy-to-see bar graph or an informative table.
Tilt Mode
Part of the sweep procedure, tilt mode checks forward low- and high-frequency
channel level tilt. Level variances display at the bottom of the DSAM-6300 screen,
and a sampling of carrier levels throughout the spectrum provides a rough indica-
tion of frequency-response variation. Based on these results, technicians can choose
an equalizer pad that will provide optimum flatness at the end of the line.
MER, BER, and Errored Seconds
When the DSAM 6300 is tuned to a QAM signal in the level mode, it simultaneously
measures MER, BER, and errored and severely errored seconds.
MER is an indicator of transmission quality degradation resulting from noise,
ingress, and composite distortions. An expression of signal-to-noise ratio plus all
other non-transient distortion signals, MER also shows phase and amplitude dis-
tortions that may have been passed from the headend. MER is an overall quality
measurement that can be performed on a digital QAM carrier. JDSU has perfected
this valuable measurement by optimizing both custom hardware and proprietary
software algorithms. The result is accurate readings that far exceed those reported
from customer-premises equipment such as digital set tops.
BER quickly detects impulse noise in the system by revealing when information is lost
or corrupted at the bit layer. The DSAM-6300 measures BER by tracking the number of
errored bits (pre-FEC) and the number of bits that cannot be fixed by forward error cor-
rection (FEC) (post-BER).
The errored seconds measurement is for troubleshooting connections with intermit-
tent bit errors occurring over a period of time. If an error has occurred during any
second of elapsed time, the errored second field increments by one. One error or mul-
tiple errors in the same second is counted as one errored second. If there is more than
1 in 1 million bit errors occurring in the same second, the severely errored second
register increments by one. The errored seconds fields are conveniently included in
the digital level display.
Miniscan measures signal strength of up to
12 channels simultaneously.
Tilt mode checks forward low- and high-frequency
channel level tilt.
Features