OK, I’m still a little confused because Noise figure is not just a property of the noise signal, it is the ratio of the input signal to noise ratio and the output signal to noise ratio, which also depends on the gain of an amplifier. I think I understand where you are going with this. You want to add the noisy sampled signal to get around the problem with the spatial modes and noise bins.
Let me know if I am understanding this correctly and I will try to get a working project file, which will mimic the optical amplifier noise without the noise bins interfering.
Regards