cheryl.vorvick@LIGO.ORG - posted 14:56, Friday 18 January 2013 (5162)
IO path pick off to optical spectrum analyzer on the PSL is modified to watch for beam drift in the IO path.
I'm using the beam that is transmitted through the bottom periscope mirror to monitor the IO beam pointing. The beam is the pick off for the OSA, and is normally (and currently) blocked when not in use for diagnostics.