Participant: Eleonora, Aritomi, Matteo, and Yuhang

Today we found the problem why I can have so large noise of cc-PLL. The reason is fiber PD is broken again. We just swap the PD and we could lock cc PLL very well. After the swap, we measured the beatnote level which is 7dBm now(measured by hp-E4411B, so the real amplitude should be -10dBm). This should be a reference for the future.

Then I measured the phase noise of both loops again. The result is shown in the attached figure 1. As you can see, in this figure, the RMS phase noise of cc PLL is 5mrad. This is 30 times smaller than the previous measurement. (Actually, I made a mistake of estimating the phase noise level of the previous measurement) While the measurement of p-pol PLL shows RMS phase noise of 15mrad, which is 3 times higher than the measurement of Marco.

While I was checking the demodulated beat note of p-pol PLL, I found a very low-frequency oscillation. This is shown in the attached figure 2. We should investigate how to remove this oscillation because it brings us almost 1rad of phase noise, which is a lot.

Next step:

buy new power cable for fiber PD or many batteries.

we should also check the level of p-pol beat note.