Tektronix CSA8000B - Manual (Page 310)

Appendix B: Automatic Measurements Reference
B- 48 CSA8000B & TDS8000B User Manual
Table B- 7: NRZ Measurements - Amplitude (cont.)
Name Definition
NRZ Q Factor NRZ Q Factor is a figure of merit of an eye diagram, reporting the ratio between the amplitude
of the NRZ eye to the total RMS noise on the High and Low levels. The NRZ eye is sampled
within the Eye Aperture, where the High and Low levels are determined as the mean of the
histogram of the data distribution in the upper and lower half of the eye, respectively. The noise
levels are characterized by
σhigh and σlow, the standard deviations from the mean for the High
and Low levels.
Where High and Low are the logical 1 and 0 levels, and
σhigh and σlow are the standard
deviations. See RZ Eye Aperture Parameters on B--62.
The Eye Aperture is adjustable and defaults to 20% of the NRZ bit time.
If enabled, measurement gates constrain the measurement region to the area between the Start
Gate (G1) and Stop Gate (G2). See To Localize a Measurement on page 3--83.
This measurement requires the use of a waveform database. When this measurement is turned
on, it will automatically set the measurement system to use a waveform database if available.
See Use a Waveform Database on page B--70.
For best results with this measurement:
H Perform a Dark Level compensation before taking this measurement if the source of the
measured waveform is an optical channel. See To Perform Dark-Level and User
Wavelength Gain Compensations on page 3--98.
H Optimize the vertical resolution before taking this measurement. See How to Optimize the
Vertical Resolution on page B--70.
NRZ Q Factor =
(High
− Low)
( σhigh + σlow)
NRZ RMS The true root mean square amplitude of the selected waveform within the measurement region.
See Defining and displaying waveforms on page 3--56.
If enabled, measurement gates constrain the measurement region to the area between the Start
Gate (G1) and Stop Gate (G2).
When this measurement is turned on, it will automatically set the measurement system to use a
waveform database if available.
For best results with this measurement:
H Perform a Dark Level compensation before taking this measurement if the source of the
measured waveform is an optical channel. See To Perform Dark-Level and User
Wavelength Gain Compensations on page 3--98.
H Optimize the vertical resolution before taking this measurement. See To Optimize the
Vertical Resolution on page B--69.