I tuned the intensity control and changed autolock parameters to get 2.6 mW light at the output of cavities on both paths. At present, the South Path has 74 % mode matching and North Path has 63% mode matching. These numbers were higher yesterday, so I'm suspecting something shifted over a day.
I also maximized gains on PMC loops and FSS loops:
| |
North |
South |
| PMC Gain (dB) |
30 (Max) |
21 |
| FSS Common Gain (V) [32dB/V] |
3.2 |
10 (Max) |
In FSS loop, I kept gain margin of 0.64 dB (i.e. the oscillations are seen at 0.2V above the set value of Common Gain) and in PMC loop, I kept it at 2 dB. I yet have to characterize noise in the FSS error signal and see what I can make better. On another note, I did a rough calculation today and I think shotnoise intercept current for our RFPDs is ~2.6 mA which means atleast 3.45 mW light should be falling on them for them to be shotnoise limited. I have to check the validity of my rough estimation but if this is true, then our FSS RFPDs are not shot noise limited. |