Calibrating the noise budget

1. I measured the noise spectra at the control point (after the servo) and the error point (before the servo and input attenuator) using the Moku. See these (loop, setup) diagrams for a better description. For the previous measurement (elog 2775 and elog 2776) we had chosen the ambiguous units of dBm/Hz, but this time we used the noise in dBV/rt Hz which does not require the impedance. I took separate measurements for the different frequency regions and stitched the data together. The raw noise spectra at both these points are shown in Attachment 1.
2. Using the PDH signal on the oscilloscope I estimated the cavity pole frequency using the same process outlined in the table here. I found the cavity pole frequency to be 2.3 MHz and the cavity response to be 132 mV/Hz -- the two quantities required to estimate the cavity transfer function (modeled as a single pole low pass filter). [update 27-Jan-22: Added Attachment 3 with the crude cavity pole and response measurements]
3. I also used the open loop transfer function measured earlier to correct for the loop suppression
4. I used the updated noise calibration notebook that I uploaded here and the data (uploaded here).
5. Attachment 2 shows a calibrated noise spectra using only the noise measured at the PDH error point. The red curves is the measured noise in-loop calibrated to the frequency noise at cavity input, the blue curves incorporate the inverted loop suppression factor. The lighter curves show the previously measured noise spectra without the cantilever.

All this was measured without adding the pomona box filter which would be my next step.