I took the transfer function of North FSS side to see how much suppression we are doing. I took the transfer function by sending source signal to EXC port in common path and measuring transfer function as Source/OUT2 in AG4395a. The open loop transfer function is related to this by G_OL = 1 - G₂ (Source/OUT2) . Here G₂ is the gain for source signal at the summing stage in common amplifier board which is -392/1.2e3 = -0.3267.

I have included an expected suppressed frequency noise plot assuming 10⁴/f Hz/rtHz frequency noise of free running NPRO. We need to suppress much more in 100Hz-1kHz  to be able to see Brownian noise.
I have also measured crossover frequency between PZT and EOM actuation. It came to around 26KHz which is not bad. We just need to increase FAST GAIN a lot more and COM gan little bit so that crossover remains the same while we get a lot of suppression in 100Hz-1kHz range. I'll look into the source of glitched causing our EOM to become unstable when increasing the feedback gains.

Code and Data

Edit Mon Jul 22 18:55:22 2019 by anchal

The gain values given in the plots are wrong. Correct values are unknown,