[Aritomi, Yuhang]

We measured free running and closed loop CC2 phase noise from filter cavity (attached picture). CC2 error signal is 356 mVpp. Phase noise from filter cavity is large at low frequency. Although phase noise at low frequency is suppressed by CC2, bump at low frequency in squeezing spectrum might be phase noise of CC2. Odd number harmonics of 50Hz peaks appear when CC2 is closed. These peaks are related to electronics of CC2.