We did the measurement of the Finess and coupling with the NKT, with 2 EOM, without AOM (so the lock signal is noisy), on the burst line.

For the coupling, we have the same value as with the GHz locked on the burst line too, which is around 20 percent.

it seems this low coupling comes from the geometrical coupling as we observed an incoming beam bigger than the cavity mode on the cameras.
(the same oscillator, locked on the lock line exhibit 50% coupling)

the FSR center value is 879.9MHz, and the FWHM is between 879.67MHz and 880.1MHz.

So, the linewidth is about 430kHz and then the Finess value is roughly the same as before about 2050.