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.