I checked the LSC related PDs
during O4c full lock (2025/07/08 02:39:26 UTC, red)
No IMC output (2025/08/20 00:00:00 UTC, blue)
The excess blue spectrum than red spectrum in LSC-REFL_PDA1_RF45_{I,Q}_ERR_DQ would come from the setting of whitening filters
red : -12 dB, 2 zero-pole fileters
blue : no whitening filters
Anyway, we cansee several 1 Hz comb lines at the
LSC-REFL_PDA1_RF45_Q_ERR_DQ
LSC-REFL_PDA3_RF45_{I,Q}_ERR_DQ
have some 1 Hz comb lines
And no lines at the POP PDs and 3f PDs.
I will check current situation with changing the whitening filters
The 1 Hz comb peaks disappeared in current sensitivity curve.
My assumption would be related the clean up campaign for GR/IR coupling, klog36533 .
