Marc, Michael and Yuhang
We have characterized some signal and noise of CCFC PD in elog2384. However, the pump power was 30mW in that case. According to the simulation and experiment, for the current system, 18mW of pump power would be better. Therefore, we did more test with 18mW pump.
In the attached figure, some signal and noise levels are shown. From this plot, 18mW pump power seems to be not large enough. Indeed, we also tried to close anyway the loop with such small error signal. But we couldn't find a good filter configuration to make the loop closed proporly.