The first plot shows the situation at the beginning of a full power, low noise lock. The ISS second loop is closed. After the re-tuningof the IMC offsets, the periscope peaks are no more visible in either the in-loop or out-of-loop ISS second loop signals.  This is very good.

However, the first plot shows that the peaks were, at that time, still visible in the DARM spectrum, together with some coherence with the periscope accelerometer. So, there is residual beam jitter that does not generate intensity noise anymore, but that is transmitted to the IFO input and couples to the OMC transmitted power.

The second plot shows the situation after a while we were locked in low noise. The peaks are no more visible in DARM: so something in the IFO drifted in the right direction (probably some thermally induced drift) and now jitter is no more converted by an IFO misalignment into intensity noise. This is something interesting to investigate in the future over long lock stretches.