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Making Measurements
Measuring Jitter Transfer
Measuring Jitter Transfer
Description:
Perform vital jitter transfer (gain) measurements using the OmniBER 718.
Option 200 is
With the OmniBER 718 you can perform Jitter transfer measurements at each of the
required for Jitter
four PDH rates 2, 8, 34, 140 Mb/s, plus DS1, DS3 and also STM-0, STM-1, STM-4
measurement and
and STM-16. Jitter Transfer measurements are also available when ATM is selected
012 for PDH
as a payload.
operation.
Jitter transfer defines the ratio of output jitter amplitude to input jitter amplitude
versus jitter frequency for a given bit rate. In network equipment some of the jitter
present at the input port of a regenerator will be transmitted to the output port. On
networks with cascaded equipment on long trunk routes it is important to limit jitter
transfer.
The jitter generator provides the stimulus for the jitter transfer measurement.
Automatic band filtering is used in the jitter receiver this provides selection and
measurement of the relevant jitter components to provide accurate and repeatable
results.
The jitter transfer results are presented in graphical and tabular form.
Graphical results are plotted as Gain V Frequency.
The relevant Pass Mask for PDH or SDH is also displayed on the graph. Please refer
to the OmniBER 718 Specifications book provided with your instrument for
detailed information on Jitter Transfer input and pass masks.
The OmniBER is capable of generating input jitter frequencies up to 20MHz. For
ITU-T G.958 Type B 'Jitter Transfer' testing at STM-4 and STM-16, we recommend
that a maximum input frequency of 3MHz is used. This will ensures that the transfer
measurement remains within the dynamic range of the receiver.
N O T E
1.The Transmitter and Receiver must be set to the same interface rate.
2. There is no ITU-T Pass Mask for 140 Mb/s.
HOW TO:
Achieve the required accuracy:
1 The OmniBER 718 must be connected back to back in order to perform a
calibration cycle before making a Jitter Transfer measurement (see figure on next
page). Use an optical attenuator to keep optical power at optimum level if you are
performing tests on optical signals.
142
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