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Entry  Thu Jul 3 18:48:09 2008, Alberto, Update, General, Beats of the two lasers in the absolute length measurement observed  
    Reply  Thu Jul 3 22:54:45 2008, Koji, Update, General, Beats of the two lasers in the absolute length measurement observed  
       Reply  Mon Jul 7 11:22:02 2008, Alberto, Update, General, Beats of the two lasers in the absolute length measurement observed  
          Reply  Mon Jul 7 13:06:38 2008, Koji, Update, General, Beats of the two lasers in the absolute length measurement observed  
Message ID: 637     Entry time: Mon Jul 7 11:22:02 2008     In reply to: 635     Reply to this: 638
Author: Alberto 
Type: Update 
Category: General 
Subject: Beats of the two lasers in the absolute length measurement observed  
I didn't post a screenshot from the RF SA because I had troubles with the interface with the computer (unfortunately the network SA cannot export the data either).

There is problem with the PLL circuit. The signal, beside the beat, also contains peaks at 33, 66 and 99 MHz, so we should think about filtering those out.


Quote:
Great! Conguraturation! I wish if I could see it! It's nice if you can put the photo or anything of the RF spectrum analyzer.

Next step:
o You can try to maximize the beat amplitude by the tuning of the Injection steering mirrors.

o At the south end of the SP table, I prepared a frequency mixer. You can put the beat signal into the RF input, and an oscillator (which you can bring from somewhere) to the LO input in order to obtain the error signal of the PLL. Put the IF output of the mixer in a SR560, and please try to lock it by a simple 6db/oct (1st order) LPF of the SR560. For the actuator you can use the fast-pzt input of the NPRO.


Quote:
Then I explored the range of temperature of the NPRO from 35deg (C) to 51.2807deg and at that point I could observe a peak corresponding to the beat at about 10MHz on the network analyzer.
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