Teledyne LeCroy Eye Doctor II - Manual (Page 39)

Operator's Manual
Case 3
A S EVERELY D EGRADED S IGNAL (10G B / S T HROUGH 30” O F FR4)
First, we'll look at the input waveform. It's clear that this waveform is much worse than just a closed eye;
there are wiggles in it that don't even get close to the center line. Look, for example, at about 3.5
divisions from the left.
Case 3 input signal.
First, we'll try what we did for Case 2 . Along the way we run into one additional problem and resolve it.
As it says in case 2: setup the CTLE to equalize the signal, change the data path so that CTLE is only used
on the path to Clock Recovery, and then only use DFE to equalize the signal for EyeDrOut.
Note: We have entered the nominal bit rate, in this case 10Gb/s, manually.
It appears that 7dB of boost is enough, the first clue we have is that Find Frequency on the Clock Recov-
ery dialog produces a reasonable bit rate for 7dB and up to beyond 10dB of boost. At much lower boost
or much higher boost (say, 15dB) it does not. The following screen-shot shows the SDA II Eye turned on
again and, after pressing Find Rate on the SDA II Clock Recovery dialog (so SDA II also knows about the
new signal rate) we see the eye produced by 8dB of boost.
It's not ideal, but the eye is open.
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