Atec Acterna-JDSU-ANT-20SE - Manual (Page 16)

Wander Analysis
Time Interval Error (TIE)
to O.172 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .numerical and graphical
Sampling rates . . . . . . . . . . . . . . . . . see under O.172 Wander Analyzer
for up to 622 Mbit/s
MTIE is additionally determined as a continually updated numerical
value.
To prevent data loss or premature termination of long term measure-
ments, the ANT-20SE checks the remaining space on the hard disk
before the start of the measurement. If necessary, the selected measure-
ment time can be adjusted.
The TIE values are recorded and are then available for subsequent off-
line MTIE/TDEV evaluations. The values are also saved in .csv format
for documentation or further analysis.
MTIE/TDEV Off-line Analysis Evaluation
Software
This software provides extended off-line statistical analysis facilities for
the results of wander measurements.
TIE values results obtained using the ANT-20SE are analyzed according
to ANSI T1.101, Telcordia GR-1244, ETSI ETS 300 462, EN 302 084,
ITU-T O.172, G.810 to G.813.
Network synchronization quality is presented graphically using the
MTIE (Maximum Time Interval Error) and TDEV (Time DEViation)
parameters. To ensure correct assessment, the tolerance masks for PRC
(Primary Reference Clock), SSU (Synchronization Supply Unit), SEC
(Synchronous Equipment Clock) or PDH can be superimposed.
The results and masks can be printed out with additional user-defined
comments.
This software allows several TIE results to be displayed simultaneously.
Decisive details during long term measurements disappear in the
multitude of results. An effective zoom function is available for detailed
wander characteristic analysis.
Result printout and export
The results can be printed out and stored internally or on floppy disk.
The file format allows further processing using standard PC software.
Frequency offset and frequency drift rate (ANSI T1.101)
To ensure reliable operation when a clock source is in holdover mode,
the frequency characteristics must not exceed specific deviation limits
relative to an absolute reference source.
To verify this data, the ANT-20SE determines the following over the
selected measurement interval:
Frequency offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . in ppm
Frequency drift rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . in ppm/s
MRTIE ± Relative MTIE (G.823 and EN 302 084)
If the reference is unavailable (too far away) when analyzing the wander
of asynchronous signals, the MTIE analysis may have a superimposed
frequency offset.
This offset depends on the difference between the signal and local
reference clocks.
The MRTIE measurement subtracts the frequency offset from the result
so that the ªactualº wander characteristic is shown.
Accessory for wander analysis
Standard frequency source . . . . . . . . . . . . . . . . . . . . . see end of chapter
Automatic Measurements
The following automatic measurements can be run for all standard bit
rates and interfaces included in the mainframe configuration
(electrical/optical) up to 2488 Mbit/s.
Automatic determination of selective Jitter Transfer
Function, JTF
Telcordia GR-499, GR-253, ANSI T1.105.03, ITU-T G.958
The Jitter Transfer Function indicates the ratio of the jitter amplitude
at the output of the device under test to that at the input at various
frequencies.
This determines whether the device under test reduces or amplifies
input jitter and at which frequencies. After a calibration measurement
to minimize intrinsic errors, the ANT-20SE outputs a pre-selected jitter
amplitude at various frequencies and measures selectively the jitter
amplitude at the output of the device under test.
The ratio of the amplitudes in dB is the Jitter Transfer Function.
The preselected amplitudes correspond to the mask for maximum
permitted input jitter. The jitter frequencies and amplitudes can also be
edited. The calibration values can be saved and used again for other
measurements.
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Figure 9: On-line wander testing (TIE).
Figure 10: Display of MTIE/TDEV results and comparison
against masks.