After the changes in our output arm this week (77427) we took some time to check the level of backscatter from the AS port, as a way to check the health of the OFI. 

I tried to reproduce Camilla and Eleonora's excitation from 71354, using a 0.65 Hz excitation on OMC L, and adjusted the amplitude until I saw about 12um peak to peak motion of the OMC (peak to peak amplitude measured by OMC M1 DAMP IN1, in um, are listed in the legend.) 

Comparing this plot to 71354, the amplitude of reflected light does seem higher now by about a factor of 2. We didn't repeat this measurement after the OMC was swapped, before the apparent changes in the OFI.