Yesterday the SOA (semiconductor optical amplifier) of the west end broke (SOA- 542-DBUT-PM, test report attached). The input fiber seemed to be burnt (see attached photo) but the company told us that they start to paint it in black to mark the higher PER ( polarization extinction ratio) port . The current setpoint was at 85mA (#65776 ), we verified that it had been plugged correctly (yellow=input, red=output) and the power at the input of the SOA was 2mW (which is consistent with the one measured back in 2020 #49407).
As a patch since we do not have a spare SOA, we removed the PSTAB photodiode and set the offset to have the maximum in transmission of the fibered AOM, thus obtaining 0dBm in input of the 2W amplifier (which is sufficient for the restart).
Diego commented the check on the PSTAB in the automation and I shelved the PSTAB in the DMS.
Discussing with the company we defined some possible tests to perform:
- One of the likely reasons of failure could be the thermal overheating of the SOA module. It gets overheated and the driver shuts down the emission. The SOA module itself could be ok and not damaged at all.
- Check the mechanical contact between the SOA module bottom and the mount ( if possible use some thermal paste between SOA module and the mount).
- Try to swap Pilot-4 controller used with K004997 with a different one and try repeating the test, making sure all cable connections are secure and electric cables are not damaged.
