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Entry  Mon Sep 19 23:19:40 2011, Keiko, Update, IOO, AM modulation mistery 
    Reply  Tue Sep 20 23:01:37 2011, Keiko, Update, IOO, AM modulation mistery 
       Reply  Wed Sep 21 16:44:18 2011, Keiko, Update, IOO, AM modulation mistery P9210138.JPGP92101381.jpg
          Reply  Wed Sep 21 17:42:35 2011, rana, Update, IOO, AM modulation misery 
             Reply  Wed Sep 21 18:53:03 2011, Keiko, Update, IOO, AM modulation misery AM0.pngAMratio1.pngAMratio50.png
                Reply  Wed Sep 21 21:13:35 2011, rana, Update, IOO, AM modulation misery 
                   Reply  Thu Sep 22 17:29:42 2011, Keiko, Update, IOO, AM modulation mistery AMmod0MICH.pngAMmod1e-1MICH.pngAMmod0SRCL.pngAMmod3e-3SRCL.pngAMmod3e-3SRCL-AS55I.png
                      Reply  Sat Sep 24 09:55:42 2011, Keiko, Update, IOO, AM modulation mistery 
Message ID: 5520     Entry time: Thu Sep 22 17:29:42 2011     In reply to: 5506     Reply to this: 5538
Author: Keiko 
Type: Update 
Category: IOO 
Subject: AM modulation mistery 

AM modulation will add offset on SRCL signal as well as PRCL signal. About 2% of the signal amplitude with the current AM level. MICH will not be affected very much.

From #5504, as for the AM modulation I checked the MICH and SRCL signals in addition to the last post for PRCL, to see the AM modulation effect on those signals. On the last post, PRCL (REFL11I) was found to have 0.002 while the maximum signal amplitude is 0.15 we use . Here, I did the same simulation for MICH and SRCL.

As a result, MICH signals are not affected very much. The AM modulation slightly changes signal slopes, but doesn't add offsets apparently. SRCL is affected more, for REFL signals. All the REFL channels get about 0.0015 offsets while the signal ampliture varies up to 0.002. AS55I (currently used for SRCL) has 1e-7 offset for 6e-6 amplitude signal (in the last figure) - which is the same offset ratio comparing with the amplitude in the PRCL case -

 

(1) MICH signals at AS port with AM m=0

AMmod0MICH.png

(2) MICH signals at AS port with AM m=0.003

AMmod1e-1MICH.png

(3) SRCL signals at AS/REFL port with AM m=0

AMmod0SRCL.png 

(3) SRCL signals at AS/REFL port with AM m=0.003

AMmod3e-3SRCL.png

AMmod3e-3SRCL-AS55I.png

 

Quote:

How about changing the x-axis of all these plots into meters or picometers and tell us how wide the PRC resonance is? (something similar to the arm cavity linewidth expression)

Also, there's the question of the relative AM/PM phase. I think you have to try out both I & Q in the sim. I think we expect Q to be the most effected by AM.

 

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