Nishino,

This is a result on 2024/10/10.

I measured the open loop transfer function (OLTF, Fig.1) of the GR lock loop. The filter funtion and actuator efficiency is measured independently (Fig. 2 and 3, Fig. 4 is their sum).

Setting of SR560 (Fig. 7) and Moku (Fig. 8):

SR560: 3 Hz, first order low pass, gain=100

Moku PID: P=10 dB, D=4.118 kHz, DS=13.0 dB

The inferred optical gain is plotted in Fig. 5. From this result, I modified the shape of filter by Moku PID controller as:

P = 10 dB, D = 20 dB, DS = 8 kHz.

Then the modified OLTF is plotted in Fig. 6 with UGF=4 kHz and phase margin=50 degrees.