Since the previous measurement showed too high loss, the optical setup was checked.
It seemed that a PBS right before the T&R measurement setup was creating a lot of scattering (halo) visible with a sensor card.

This PBS was placed to confirm the output polarization from the fiber, so it was ok to remove it.

After the removal, the R&T measurement was redone.
This time the loss distributed from 0.2% to 0.8% except for the one with 1.3%. Basically 0.25% is the quantization unit due to the lack of resolution.

At least B7, B10, B12 seems the good candidate for the DCPD BS.

The AR reflection was also measured. There was a strong halo from the main reflection with an iris and sense the power at ~.5mm distance to separate the AR reflection from anything else. Now they are all somewhat realistic. I'll elog the measurement tonight.

33.6 +/- 0.2 uW out of 39.10+/-0.05 mW was observed. The offset was -0.236uW.
This gives us the AR reflectivity of 865+/-5ppm . This meets the spec R<0.1%

Mirror | P_Incident   P_Trans      P_Refl       | T             R             loss          |
       | [mW]         [mW]         [mW]         |                                           |
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B1     | 39.10+/-0.05 19.65+/-0.05 19.25+/-0.05 | 0.503+/-0.001 0.492+/-0.001 0.005+/-0.002 |
B2     | 39.80+/-0.05 19.90+/-0.05 19.70+/-0.05 | 0.500+/-0.001 0.495+/-0.001 0.005+/-0.002 |
B4     | 39.50+/-0.05 19.70+/-0.05 19.30+/-0.05 | 0.499+/-0.001 0.489+/-0.001 0.013+/-0.002 |
B5     | 39.50+/-0.05 19.70+/-0.05 19.50+/-0.05 | 0.499+/-0.001 0.494+/-0.001 0.008+/-0.002 |
B6     | 39.55+/-0.05 19.50+/-0.05 19.95+/-0.05 | 0.493+/-0.001 0.504+/-0.001 0.003+/-0.002 |
B7     | 40.10+/-0.05 19.80+/-0.05 20.20+/-0.05 | 0.494+/-0.001 0.504+/-0.001 0.002+/-0.002 |
B8     | 40.15+/-0.05 19.80+/-0.05 20.20+/-0.05 | 0.493+/-0.001 0.503+/-0.001 0.004+/-0.002 |
B9     | 40.10+/-0.05 19.90+/-0.05 19.90+/-0.05 | 0.496+/-0.001 0.496+/-0.001 0.008+/-0.002 |
B10    | 40.10+/-0.05 19.70+/-0.05 20.30+/-0.05 | 0.491+/-0.001 0.506+/-0.001 0.002+/-0.002 |
B11    | 40.20+/-0.05 19.80+/-0.05 20.20+/-0.05 | 0.493+/-0.001 0.502+/-0.001 0.005+/-0.002 |
B12    | 40.20+/-0.05 19.90+/-0.05 20.20+/-0.05 | 0.495+/-0.001 0.502+/-0.001 0.002+/-0.002 |
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