  We formulate quantum optics to include frequency dependence in the modeling
of optical networks. Entangled light pulses available for quantum cryptography
are entangled not only in polarization but also, whether one wants it or not,
in frequency. We model effects of the frequency spectrum of faint
polarization-entangled light pulses on detection statistics. For instance, we
show how polarization entanglement combines with frequency entanglement in the
variation of detection statistics with pulse energy. Attention is paid not only
to single-photon light states but also to multi-photon states. These are needed
(1) to analyze the dependence of statistics on energy and (2) to help in
calibrating fiber couplers, lasers and other devices, even when their desired
use is for the generation of single-photon light.
