Astract:

For 20W operation, we need to reduce the laser power on TMSX/Y PDs and S/PPOL monitor at POP/POS tables.

Detail:

I checked the PD/QPD signals when IFO was locked with 10W.

QPD signals:

IMMT1T QPDs: less than half of the saturation (fig1).
IMC REFL QPDs: less than half of the saturation (fig2).
IMC trans QPDs: less than half of the saturation (fig3).
TMSX IR QPDs: less than half of the saturation (fig4).
TMSY IR QPDs: less than half of the saturation (fig5).
POPFORWARD QPDs: less than half of the saturation (fig6).

PD signals:

MC trans, MC REFL, and IFO REFL PDs: less than half of the saturation (fig7).
POP, POS, AS PDs: POP_SPOL and POS_SPOL reached more than half of the saturation (fig8).
TMSX, TMSY PDs: both reached more than half of the saturation (fig9).

So, laser power on POP SPOL, POS SPOL, TMSX, TMSY PD should be reduced at least by a factor of 2 for 20W operation.

Note:

Since PDA100 is used for POP SPOL, POS SPOL, TMSX, and TMSY PDs, saturation level is not the ADC saturation (32768 cnts) but 5V of PD output, which is about half of ADC saturation.