We study the role of Coulomb interaction in an electronic Fabry-Perot
interferometer (FPI) realized with chiral edge states in the integer quantum
Hall regime in the limit of weak backscattering. Assuming that a compressible
Coulomb island in a bulk region of the FPI is formed, we develop a capacitance
model which explains the plethora of experimental data on the flux and gate
periodicity of conductance oscillations. It is also shown that a suppression of
finite-bias visibility stems from a combination of weak Coulomb blockade and a
nonequilibrium dephasing by the quantum shot noise