Arnaud, Eric G, Apollo, Thomas We've installed the optical lever with two levels of 1:10 whitening in hardware and complimentary de-whitening in software. They are calibrated to micro-radians and I've attached a plot showing the linear response. The difference in their gains is most likely due to their difference in beam width. Pit_Gaussian_width = 2.02 mm Yaw_Gaussian_width = 1.41 mm H1:SUS-ETMY_L3_OPLEV_PIT_GAIN = 95.50 H1:SUS-ETMY_L3_OPLEV_YAW_GAIN = 69.33 H1:SUS-ETMY_L3_OPLEV_SUM_OUT = 20,000 counts.