Base on measured TFs and spectra, we made noise budget model of ALS of X arm experiment.
The attached figure shows the preliminary results of expected frequency stability of the main laser to the arm cavity, and measured frequency stablity of ALS (7561).

This results are prelininary in the sense that I have to measure a couple of things:
* Green PD noise has a jump in its spectrum at ~ 13 Hz, which indicates I might have made some mistakes when measuring it.
* CARM servo noise to be measured.
* OLTF of ALS CARM, just to make sure.

From the noise budget for the current configuration, it seems that Green noise, or more specifically servo noise and PD noise in green PDH loop, is limiting the stability.
So, the next thing I have to do is to increase the optical gain of the green PDH.