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How to make a correct eye mask (86100C)?

Question asked by liwenzao on Jul 1, 2011
Hi all,

I have a very basic question. I'm trying to make a eye mask for testing an optical transmitter. Is the mask usually defined for normalized power level? Because I noticed that when I do eye mask tests for varying signal levels, it seems to rescale the mask automatically to accommodate the signal. If that is the case, how can I use it to qualify the transmitter power level? I have a bad transmitter that gives low output power, but the shape of the eye still looks okay, and it passes the eye test? What's the point of the size of the eye then? According to the transmitter specs, the minimum vertical eye opening should be a absolue power value.

I'm really confused. Anyone can enlighten me? or point me to a reference?

Thanks in advance. (BTW, my oscilloscope is 86100C.)