  In this paper we describe a Fabry-Perot interferometer in the language of
quantum optics. We go on to model the Fabry-Perot interferometer as a beam
splitter having frequency dependent transmissivity and reflectivity
coefficients. The antibunching, a totally non-classical effect, is to be
expected if one excites this interferometer with carefully frequency-selected
single photons arriving simultaneously from opposite directions. Contrary to a
normal beam splitter, even slightly different frequency single photons should
be able to show this effect, as long as the photon counters are not frequency
selective.
