Aritomi and Yuhang

As Aritomi-san said in entry 1542, we have power fluctuation issue. We are interested in the amplitude and frequency of these fluctuations. The detail investigation about this will be done later. The spectrum of this reflected signal is attached in the figure.

We could see the noise goes up from 50 Hz to 10Hz. This can be an issue for further squeezing degradation.

We are thinking to check also this signal together with filter cavity IR transmission. And GR transmission and reflection. Besides, we didn't use filter cavity length control at that moment. So we will also compare this spectrum when there will be length control.