Complex sentence: Each photon breaks up a number of Cooper pairs which depends on its wavelength, thus the detector can also serve as a spectrometer, with spectral resolution limited by the shot noise fluctuations in the released charge.
Split into simpler sentences: Each photon breaks up a number of Cooper pairs which depends on its wavelength. The detector can be operated as a photon-counting spectrometer, with a spectral resolution limited by the shot noise fluctuations in the released charge.