By using the measured NPRO PZT actuation gain of ~4 MHz/V, along with an analytical model of the PDH box and primary OLTF, I estimated a cavity response of roughly 5.6 x 10-8 V/Hz. Using this, I calibrated both the primary error signal and feedback signal into units of frequency to see that they were consistent. The calibrations are
- Feedback signal: multiply by the PZT actuation gain in [Hz/V] and divide by the OLTF (to get the suppressed noise)
- Error signal: divide by the cavity response in [V/Hz]
The plot below demonstrates that they are self-consistent. Note that this is only done up to 10 kHz because I have not made an analytical model of the notch filter yet.