[SI-LIST] Fw: Anritsu PPG output glitches

  • From: hwg <hwg434@xxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Fri, 23 Apr 2010 09:56:47 -0700 (PDT)

Hello SI gurus,

I was on si-list years ago when I was doing some optical line card hardware 
design.  I've been doing other things recently, but a colleague of mine is 
having an issue, and I wonder if any of you have seen anything like this.

We have a production test environment for 10Gbps lasers, which uses Anritsu 
pattern generators to generate signals to drive the lasers.

We share a single PPG among multiple test fixtures, by
- using DATA and DATA_BAR to drive separate fixtures
- using an external 3db splitter (Picosecond Pulse) to split one of the outputs

In total, we have 3 PPG's driving 8 test fixtures.  There are external RF 
amplifiers, RF switches and bias-Tees connected as well.  (Details are in the 
attached slides.)

We're seeing that occasionally, the output of the Anritsu PPG gets "noisy" 
(that the best I can describe it; see the pictures in the attached slides).

This never happened, over a 5-year period, until we recently upgraded our 
Anritsu PPG's to a new model.  (MUT181020A)

I suspect something with the output driver of the new Anritsu PPG.  Perhaps 
when we switch the RF switches, there is a momentary impedance discontinuity, 
and thus a reflection back to the PPG, which puts its output into a "bad" 

The only way to recover the PPG so it generates a clean output again is to 
power cycle it.

Has anyone seen anything like this before?  Any suggestions on how to solve it 
would be greatly appreciated.

- hwg


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