Last Friday, Niko and I performed TX module maintenance measurements on both EX and EY PCal systems. Primarily we were interested in the health of the aging lasers in the TX modules, which have been running continuously for both O1 and O2 as well as much of the time when we were not in observing runs. The stated expected lifetime of these lasers from the CrystaLaser website is >10000 hours. The duration of just O1 and O2 combined was ~10000 hours, so I would estimate these lasers have been running for more like 20000 hours. See attached photos of the log sheets for both ends stations. Comparing the laser output powers for both lasers from what was measured in the incoming inspection document (T1300100):
| SN | Incoming power as measured | Current power as measured | |
| EX | 01 | 2.05 W | 1.72 W |
| EY | 08 | 2.03 W | 1.94 W |
The EX laser appears to be degrading faster than EY and is at a level that we believe we should attempt to tune up the laser itself. Rick has instructions from CrystaLaser on how to do so, which we will attempt during an upcoming maintenance period.
We also took OLTF measurements of the OFS servo as per T1600436. We adjusted the gains to get the UGFs to be at 100kHz. Screen dumps of the SR785 traces also attached.
I turned the lasers off after these measurements to save some lifetime, but Rick suggested that we leave them on to stabilize and start producing baseline data. Today, I turned both EX and EY PCal lasers ON.