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Making Measurements
Measuring Wander
Measuring Wander
Description:
Wander is defined as the long- term variations of the significant instants of a digital
Option 200 is
signal from their ideal positions in time, where long-term implies phase oscillations
required for Jitter
of frequency less than or equal to a demarcation point that is specified for each
measurement.
interface rate. Refer to ANSI T1.102 for the demarcation frequencies for each
digital signal.
Accurate Wander measurements require a Wander reference derived from a master
timing external source. Connect your external timing source to the appropriate port
on the instrument clock module. Wander results are displayed in UI or nanoseconds.
Jitter Amplitude and Jitter Hits results are also available.
Problems may arise due to wrongly configured equipment running on internal
clocks or at the junction of different operator's network equipment. Since the timing
sources may operate at slightly different frequencies and exhibit long term
frequency drift, phase difference (Wander) may occur between the incoming data
and the network equipment. This causes "Bit Slips" in the network equipment
buffers and results in frames being repeated or deleted thus reducing the efficiency
of data transfer.
When wander is measured at 2 Mb/s or DS1, Estimated Bit and Frame slips are
calculated and a Bar Graph shows the cumulative Wander over the measurement
period.
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