Sheila and I went out to IOT2L. We measured the power before and after the splitter called "IO_MCR_BS1" in this diagram of IOT2L. This is listed as a 50/50 beamsplitter. However, there is no possible way it can be, because we measure about 2.7 mW just before that splitter, and 2.45 mW on the IMC refl path and 0.25 mW on the WFS path. So we think it must be a 90/10.
Sheila then adjusted the have wave plate upstream of this splitter so that the light on IMC refl dropped from 2.4 mW to 1.2 mW., as measured from the IMC refl diode.
We compensated this change by raising the IMC gains by 6 dB in the guardian. I doubled all the IMC WFS input matrix gains, SDF attached.
SDFed the IMC PZT position that we think we like.
After the waveplate adjustment and updating of gains in Guardian, we took an IMC OLG measurement with the IMC locked at 2W input. The UGF was measured at 35.0 kHz.