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Entry  Wed Jul 23 22:34:07 2008, Yoichi, Update, LSC, Arm cavity g-factor measurement 
    Reply  Thu Jul 24 01:27:00 2008, Koji, Update, LSC, Arm cavity g-factor measurement 
       Reply  Thu Jul 24 02:57:26 2008, rob, Update, LSC, Arm cavity g-factor measurement 
          Reply  Thu Jul 24 08:09:26 2008, Yoichi, Update, LSC, Arm cavity g-factor measurement 
Message ID: 733     Entry time: Thu Jul 24 08:09:26 2008     In reply to: 731
Author: Yoichi 
Type: Update 
Category: LSC 
Subject: Arm cavity g-factor measurement 

Quote:

A-ha! Do you always expect the 30Hz signal, don't you?
Because this is the PDH technique.


Yes you are right. I realized this when I was thinking about it in the bed Smile
The 30Hz signal should always be present because the carrier is phase shifted at 30Hz by the cavity length change.
I think the change in the signal ratio between I and Q happened because as the 166MHz sidebands get phase change when they move around the MC transmission peak due to the cavity pole of the MC. It changes the optimal demodulation phase for the 166MHz PDH signal at the AS port.


Quote:

We should be able to see 166MHz sideband resonances using the double demodulated photodetectors. With these, the 33MHz sidebands will be acting as LO when the 166MHz sideband (or mode) resonates. Some modeling may be necessary to determine if the SNR will be good enough to make this worthwhile, however.


I will try, but at 100kHz away from the MC FSR (the number predicted by John's calculation), the transmission of the 166MHz sidebands is very weak. I did not see any signal when I swept it +/- 500kHz. Unfortunately, the Marconi's output level is almost at its maximum. So we don't have much room for increasing the sideband power.
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