以下几张图摘自：http://blog.ednchina.com/frankie_wang/1460374/message.aspx
以下文字摘自：http://cp.literature.agilent.com/litweb/pdf/70874-90023.pdf
Measurement Definitions
Extinction Ratio This measurement is the ratio of the most prevalent high level to the most prevalent low level over one bit interval. The measurement results are displayed in both linear and logarithmic (10log) forms of the ratio. The peaks of the histogram are used to set initial limits for the computation of the one and zero levels. The initial mean and sigma of the one level is based on histogram data above the relative 50% point of the peaks. The limits for the next evaluation of the histogram data are set to the initial mean plus-or-minus one sigma. The new mean and sigma for the one level is determined. This process iterates several times until the sigma becomes small and the mean converges on the most prevalent one level. The determination of the most prevalent zero level is based on the same algorithm, except the initial mean and sigma of the zero level are based on histogram data below the relative 50% point of the peaks.
1 Level (mean, σ) This measurement is the mean and sigma of the one level determined from a 20% window of a bit interval centered in the middle of the bit.
0 Level (mean, σ) This measurement is the mean and sigma of the zero level determined from a 20% window of a bit interval centered in the middle of the bit.
Eye Height This measurement is the difference between the mean minus-three sigma of the one level and the mean plus-three sigma of the zero level.
Crossing Level This measurement is the amplitude that the one level and zero level cross. It also expresses the level as a percentage of the mean one level and mean zero level difference.
Eye Width This measurement is the eye width determined from the bit period and the eye jitter. On the eye, the edges are defined to be the left crossing point plus three sigma and the right crossing point minus-three sigma.
Eye Jitter (σ) This measurement is the sigma of a horizontal histogram at the crossing point.
Mean Rise Time This measurement is the mean time interval between a horizontal histogram centered at the lower threshold point and a horizontal histogram centered at the upper threshold point on a rising edge of an eye-diagram.
Mean Fall Time This measurement is the mean time interval between a horizontal histogram centered at the upper threshold point and a horizontal histogram centered at the lower threshold point on a falling edge of an eye-diagram.
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