• Network output jitter (G.825)
• Network element output jitter (G.783, G.813)
• Jitter transfer function (G.958)
• Jitter and Wander tolerance (G.825, G.813)
Showing posts with label Jitter. Show all posts
Showing posts with label Jitter. Show all posts
Sunday, September 6, 2009
How to Measure Jitter?
A jitter meter test set is basically made up from the following items:
- Pattern clock converter
- reference clock generator
- phase meter
- weighting filters
- peak value detector
What is the Source of Jitter?
•Interference signals
Impulsive noise or cross talk may cause phase variations (non systematic jitter). Normally high frequency jitter.
•Pattern dependent jitter
Distortion of the signal lead to so-called inter-symbol interference, which is pulse cross talk that varies with time (Pattern dependent jitter.
•Phase noise
The clock regenerators in SDH systems are generally synchronized to a reference clock. Some phase variations remain, due to thermal noise or drift in the oscillator used.
•Delay variation
Changes in the signal delay times in the transmission path lead to corresponding phase variations. These variations are generally slow (Wander). (e.g. Temperature changes in optical fibers).
•Stuffing and wait time jitter
During removing of stuffing bits gaps have to be compensated out by a smoothed clock.
•Mapping jitter
•Pointer jitter
During incrementing or decrementing of the pointer value. This shifts the payload by 8 or 24 bits corresponding to a phase hit of 8 or 24 UI.
Impulsive noise or cross talk may cause phase variations (non systematic jitter). Normally high frequency jitter.
•Pattern dependent jitter
Distortion of the signal lead to so-called inter-symbol interference, which is pulse cross talk that varies with time (Pattern dependent jitter.
•Phase noise
The clock regenerators in SDH systems are generally synchronized to a reference clock. Some phase variations remain, due to thermal noise or drift in the oscillator used.
•Delay variation
Changes in the signal delay times in the transmission path lead to corresponding phase variations. These variations are generally slow (Wander). (e.g. Temperature changes in optical fibers).
•Stuffing and wait time jitter
During removing of stuffing bits gaps have to be compensated out by a smoothed clock.
•Mapping jitter
•Pointer jitter
During incrementing or decrementing of the pointer value. This shifts the payload by 8 or 24 bits corresponding to a phase hit of 8 or 24 UI.
What is Jitter?
Jitter
Periodic or random changes in the phase of the transmission clock referred to the master or reference clock. In other words, the edges of a digital signal are advanced or retarded in time when compared with the reference clock or an absolutely regular time framework. Jitter generally referes to deviations of more than 10Hz.
Periodic or random changes in the phase of the transmission clock referred to the master or reference clock. In other words, the edges of a digital signal are advanced or retarded in time when compared with the reference clock or an absolutely regular time framework. Jitter generally referes to deviations of more than 10Hz.
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