Tektronix CSA8000B - Manual (Page 303)

Appendix B: Automatic Measurements Reference
CSA8000B & TDS8000B User Manual B- 41
Table B- 7: NRZ Measurements - Amplitude (cont.)
Name Definition
NRZ Extinction Ratio
(dB) The ratio of the average power levels of the logic 1 level (High) to the logic 0 level (Low) of an
optical NRZ signal, expressed in decibels (dB). All level determinations are made within the
NRZ Eye Aperture.
Where High and Low are the logical 1 and 0 levels. See RZ Eye Aperture Parameters
on B--62.
The Eye Aperture is adjustable and defaults to 20% of the NRZ bit time. See NRZ Eye-Aperture
Parameters on page B--65.
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
or, 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 measurement results:
H Perform a Dark Level compensation before taking this measurement. 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 ExtRatio [dB]
= 10 × log
Ꮛ
High
Low
Ꮠ
NRZ Eye Height A measure of how noise affects the vertical opening between the High and Low levels of an
NRZ eye. 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.
NRZ Eye Height = (High – 3 *
σhigh) – (Low + 3 * σlow)
Where High and Low are the logical 1 and 0 levels, and
σhigh and σlow are the standard
deviations.
The Eye Aperture is adjustable and defaults to 20% of the NRZ bit time. See RZ Eye Aperture
Parameters on B--62.
If enabled, measurement gates constrain the measurement region to the area between the Start
Gate (G1) and Stop Gate (G2).
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.
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.