Editing Eye pattern (section)

== Modulation ==

Each form of baseband modulation produces an eye pattern with a unique appearance.

=== NRZ ===

The eye pattern of a [[w:Non-return-to-zero|NRZ]] signal should consist of two clearly distinct levels with smooth transitions between them.

[[File:Eye_pattern_example.png|thumb|upright=1.5|none|Eye pattern of a 1.25&nbsp;Gbit/s NRZ signal]]

=== MLT-3 ===

The eye pattern of a [[w:MLT-3_encoding|MLT-3]] signal should consist of three clearly distinct levels (nominally -1, 0, +1 from bottom to top). The 0 level should be located at zero volts and the overall shape should be symmetric about the horizontal axis. The +1 and -1 states should have equal amplitude. There should be smooth transitions from the 0 state to the +1 and -1 states, however there should be no direct transitions from the -1 to +1 state (which would indicate the signal is PAM-3 rather than MLT-3).

[[File:Eye pattern MLT3.png|thumb|upright=1.5|none|Eye pattern of a 125&nbsp;Mbit/s MLT-3 signal]]

=== PAM ===

The eye pattern of a [[w:Pulse-amplitude_modulation|PAM]] signal should consist of N clearly distinct levels (depending on the PAM order, for example PAM-4 should have four levels and PAM-3 should have three). The overall shape should be symmetric about the horizontal axis and the spacing of all levels should be uniform.

[[File:Eye pattern PAM3.png|thumb|upright=1.5|none|Eye pattern of a PAM-3 signal ([[100BASE-T1]] automotive Ethernet)]]

=== PSK ===
{{Main|Phase-shift keying}}
[[File:Binary PSK eye diagram.svg|Eye pattern of a binary [[Phase-shift keying|PSK]] system]]
[[File:Multipath system eye diagram.svg|Eye pattern of the same system with [[Multipath interference|multipath interference (MI)]] effects added]]