[Aritomi, Yuhang]

We checked the FC length correction to end mirror and CC2 correction to input mirror when the homodyne angle was changed from anti-squeezing to squeezing (attached figure). The blue and green curves show the CC2 input mirror correction and FC end mirror correction, respectively. The homodyne angle changed from anti-squeezing to squeezing at around -1 min (actually, we don't know the exact timing, but it is between -1.5 min and 1 min).

As shown in the figure, there was no change in input and end mirror correction signal when the homodyne angle changed. This means the FC length is not changed by the homodyne angle change. So the detuning drift in FDS will not be due to the homodyne angle change.