Evan G., Sheila D.

After disconnecting the EY OpLev fiber so that no light enters the vacuum, see LHO aLOG 35774, we have not observed any glitching around the 30 Hz region as compared to previous days. The attached Omicron spectrogram shows no indication of these glitches compared to previous days (for comparison, see the previous day here).

Our speculation is that the coupling to h(t) is caused by the changing radiation pressure as the OpLev mode hops, but the best way to confirm this is to put the OpLev light on a PD so that we can monitor the OpLev laser glitches and also see no corresponding glitch in h(t). This would eliminate some other electromagnetic coupling as a possible mechanism for this glitch pathway.