It was pointed out that the measurement of oplev p/y spectrums are not meaningful. So I went to check again what can be the problem. In the end, I found the laser head of the oplev is totally loose. After I fixed it, I took spectrums again. Figure 1 shows these spectrums.

Besides, I also put some pictures of the KAGRA QPD set-up. (note that we could close the black box, pictures are just taken with box open) (we will use a better box in the future if we really use this QPD)