Oplev spectra and IFO signals.

I put the current IFO signal and the one in ER(12/20). Almost no difference, although there is control noise around 30-40 Hz. We need to tweak roll-off, or design filters for low noise mode. However, it helps the low frequency angular motion and doing nothing worse for lock acquisition. I would say this damping helps a lot for P(D)RFPMI lock acquisition and ASC.