Do you mean dispersion as in "a pulse gets longer in time due to different length of paths taken by different photons due to scattering"? If not, what do you me

Do you mean dispersion as in "a pulse gets longer in time due to different length of paths taken by different photons due to scattering"? If not, what do you mean? My point about seeing a flash was precisely that SNR is high, because I can distinguish the flash from noise. EDIT: SNR depends on frequency only inasmuch noise level depends on frequency.