Kiwamu, TJ, Elli
This morning while EY plugging HWS cables into the ISCTEY feedthrough panel, I touched the fiber bringing the red PLL reference signal to EY. This changed the fiber wrong polarization (see chanel H1:ALS-Y_FIBR_LOCK_FIBER_POLARIZATIONPERCENT) from 1% to 32%, which is above the maximum allowable value of 30%. This fiber is also connected to ISCTEY feedthrough panel, and then some of the fiber is sitting on a coil on top of ISCTEY. All I did to change the polarization was to gently move the coil on top of the table. When Kiwamu and TJ noticed the polarization had changed, I nudged the fiber coil on top of the table around a bit untill the fiber polarization returned to 8%. It seems it is very easy to bump the fiber and change the polarization.
One can use the fiber polarization controller in the MSR to bring it back.