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Entry  Wed Feb 11 00:07:54 2015, rana, Update, LSC, Lock Loss plot 1107673198.png1107673198.png
    Reply  Wed Feb 11 02:42:05 2015, Jenne, Update, LSC, PRC error signal RF spectra REFL33_25.pdfREFL33_15.pdf
       Reply  Wed Feb 11 03:41:12 2015, Koji, Update, LSC, PRC error signal RF spectra 
          Reply  Wed Feb 11 17:31:11 2015, ericq, Update, LSC, RFPD spectra REFL.pngAS.pngPOP.png2015-02-PDSpectra.zip
             Reply  Wed Feb 11 18:07:42 2015, ericq, Update, LSC, RFPD spectra 
                Reply  Thu Feb 12 01:00:18 2015, rana, Update, LSC, RFPD spectra 
Message ID: 11008     Entry time: Thu Feb 12 01:00:18 2015     In reply to: 11004
Author: rana 
Type: Update 
Category: LSC 
Subject: RFPD spectra 

The nonlinearity in the LSC detection chain (cf T050268) comes from the photodetector and not the demod board. The demod board has low pass or band pass filters which Suresh installed a long time ago (we should check out what's in REFL33 demod board). 

Inside the photodetector the nonlinearity comes about because of photodiode bias modulation (aka the Grote effect) and slew rate limited distortion in the MAX4107 preamp.

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