In an eye diagram, jitter is visually represented by the horizontal blurring of the transition edges. Jitter reduces the certainty of when a signal crosses a logical threshold, making bit errors more likely. Constant binary 1 and 0 levels are shown, as well as transitions from 0 to 1, 1 to 0, 0 to 1 to 0, and 1 to 0 to 1. In telecommunications, an eye pattern, also known as an eye diagram, is an oscilloscope. This instrument class measures samples of the input signal to form an eye diagram that can be used for analysis of the signal's noise, jitter, and eye mask compliance. The resulting image takes on a distinct eye-like shape, from which engineers can discern important signal characteristics. Eye diagrams provide an intuitive graphical representation of optical digital communication signals. The quality of the signal, that is, and fall times, the amount of intersymbol interference (ISI), noise, can be judged from the appearance of the eye.
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