Application Tutorials
Tutorial 3: Measure Extinction Ratios on Low-Level Signals
Tutorial 3: Measure Extinction Ratios on Low-Level Signals Repeatable extinction ratio measurements can be made on low-level signals.
This is accomplished by applying a filter to the signal. This filter improves
measurement sensitivity and is useful for analyzing:
•low-level extinction ratios
•pattern dependent transitions
•intersymbol interference
In this tutorial, the eye-diagram analyzer is placed in ey eline mode so that the
eye filter can be applied to reduce trace noise. To measure the signa l, a photo-
diode converter with a responsivity of 30 volts/watt is used.
When making extinction ratio measurements in eyeline mode, the number of
samples should be increased from the default of 1000 to something on the
order of 20000. This insures a number of traces are evaluated to co mpute the
extinction ratio. The compatible mode is eyeline.
Change to Eyeline Mode
1Set the instrument to a known state by pressing:
INSTR PRESET, Setup, diagram, EYELINE, Traces
2Set the number of persistence sweeps by pres sing:
persist, VARIABL, PERSIST SWEEPS and enter 5, prev menu
3Turn on autoscaling by pressing:
Trg,Cal, more 1 of 2, Traces, AUTO-SCALE
The display should look like the following figure.
A low-amplitude response, similar to that shown in this figure, can result when
using non-amplified lightwave converters to measure optical signals.