= Summary =
I removed a DC PD, PDA100A from BS chamber, and put it on the REFL table.
We can now see signals of the reflection light from ETMY, with the DC PD on the REFL table.

= What I did =
-- with a help from Fabian, removed the large pedestal that holded the PD from the BS optical bench. Yokozawa-san will take this large pedestal to EYA booth.
-- removed a D-sub 9 pin cable (~ 30m long) and a BNC cable (~ 5m long) that were used to send a signal from the PD to BS rack. I put these cables near IYA chamber, and Yokozawa-san will take care of them.
-- put the PD on the REFL table, using the iris Izumi-san put yesterday, as a reference. I set the gain of the PD to 20dB. See the attached photo to see how the reflection beam looks like (taken by Michimura-san).
-- did cabling for this PD; the output of the PD goes to BNC-Dsub converter with 20m long BNC, and then goes to an AI chasis in IOO rack. ADC2-ch28 is assigned for this signal.
-- modified k1imc model, and added a filter bank named K1:IMC-IFI_PDA1_DC to monitor the power of the reflection.
-- found the signal.

= On the power of the reflection light =
See the attached. The reflection power was at most 3500 counts, which corresponds to 0.47 mW (please refer to 3557, for example).
On the other hand, the expected power of light reaching the REFL port is ~ 1 mW (~ 400 mW after IMC, transmit through PRM twice and reflected twice by BS (1/400 in total) ).
I would say this result is reasonable, considering phi-100mm view port between Y arm and IYA is still there.