Jitter

Jitter is an unwanted variation of one or more characteristics of a periodic signal in electronics and telecommunication.

Jitter has deterministic and random components. Deterministic jitter(DJ) comes from system sources such as crosstalk, inter-symbol interference and power-supply feed through. It is bounded so it can be characterized by it's peak-to-peak value. Random jitter(RJ) comes from physical sources such as thermal noise, shot noise and scattering in optical media. Random jitter is typically Gaussian in shape so it is unbounded.

Random Jitter
Random jitter is characterized by a Gaussian distribution and is assumed unbounded. The distribution is quantified by the standard deviation and mean to measure random jitters and can be used to predict peak-to-peak jitter as a function of Bit Error Rate(BER).
Common sources of RJ include shot noise, flicker noise and thermal noise.Shot noise amplitude is a function of average current flow. Flicker noise has a spectral distribution that is proportional to 1/f. Thermal noise can be represented by broadband "white" noise and has flat spectral density.

Deterministic Jitter