[Aritomi, Yuhang, Eleonora]

Recently we had a problem about IR back reflection from filter cavity. After installation of faraday, green phase error signal with p pol transmission is very stable (Pic 1) and we could lock green phase with p pol transmission stably. After locking of green phase, IR transmission of filter cavity is stable (Pic 2). One problem is that IR FC reflection is fluctuating even when green phase is locked and it seems to come from motion of suspended mirrors (entry 1547).