From the open loop transfer function we measured (6654), we estimated the cavity pole frequency of X arm for green, which is connected to the finesse.

I fitted the transfer function with the fitting parameters of overall gain (since we don't know the optical gain), pole for 100kHz LPF and phase delay (to phenomelogically explain the high frequency behavior, included in the fitting params), and the cavity pole frequency.

The attached figure shows the data and fitting curves.

According to this fitting results, the cavity pole frequency is 609 +/- 5 Hz, and equivalently the finesse is 41.0 +/ 0.3.

Note that T_ITMX = 7.5+/-0.4%, and T_ETMX = 7.1+/-0.2%, the expected cavity pole and finesse are 603 +/- 36 Hz and 41.4 +/- 2.4.
They are consistent. Cool!

NOTE:
For zero/pole frequencies for the servo circuit, we used the designed values, not the measured ones. This means that there might be systematic error due to that.
We will measure the TF of the circuit at some point.