Hi there,
Sorry for delay in response.
please be advised that, the extinction ratio as defined is the ratio between the “one” level and the “zero” level. so this value should be defined on the measuring device itself not in the propagating medium FSO channel or Optical fiber!!
so you can change this value in “BER Analyzer”, “EYE DIAGRAM ANALYZER”…etc.
So in your system, based on the propagation medium, you can set the Extinction ratio in the analyzer you use.
Hope this answer your question and clarify the issue.
thanks
Mohamed Abouseif