I measured CCFC FDS with fixed homodyne angle for 3 hours with 30 minutes interval (figure 1). The FC was unlocked between each FDS measurement. According to the least square fitting, the detuning changed by 7 Hz in 3 hours even with fixed homodyne angle.

Before each FDS measurement, I optimized p pol PLL frequency to have maximum BAB transmission with 20mW green. The nonlinear gain change was 4.4-4.7 in 3 hours, which corresponds to generated squeezing of 10.1-10.5 dB. Since I optimized p pol PLL every time I measured the nonlinear gain, this nonlinear gain change is the real nonlinear gain change, not the detuning change of BAB.

I also measured shot noise before/after all the FDS measurement (figure 2). The shot noise changed by 0.15dB in 3 hours.

sqz_dB = 10.5;                   % generated squeezing (dB)

L_rt = 120e-6;                   % FC losses

L = 0.49;                        % propagation losses  

A0 = 0.06;                       % Squeezer/filter cavity mode mismatch

C0 = 0.02;                       % Squeezer/local oscillator mode mismatch

ERR_L =   1.5e-12;               % Lock accuracy (m)

ERR_csi = 30e-3;                 % Phase noise (rad)