After PBS is rotated to the right position (yesterday I made a mistake by minimizing the split beam.

The split beam is minimized. This guarantees that the beam passing through is highly linearly polarized.

The reflection back to PMC is reduced from 1.9 mW to ~1.1 mW.

The cross correlation between the beat measurement and RIN is measured before and after the reduction of back reflection.

The plot shows certain correlation between RCAV's RIN and beat measurement when there is back reflection to PMC.