EvanH, LouisD, GabrieleV, FranciscoL

We wanted to see if frequency noise was the source of noise in DARM. To test that, we measured the DARM power spectrum from REFL A and REFL B with various configurations, namely we measured both A and B in loop, then only A in loop and only B in loop.

If the source of noise was frequency noise, we should see a increase of sqrt(2) when measuring from only one photodiode.

We do not see any increase in the DARM power spectrum (see attached figure) so the contribution from frequency noise is not the culprit for the excess noise.