Using the discrete dipole approximation method and exact analytical solutions, we demonstrate that an incident electromagnetic wave can be confined and enhanced between two silver layers due to the Fabry-Perot effect. The enhanced electric field between the two layers depends on the distance between the two layers and each layer's thickness. An enhanced electric field, |E|(2), with an enhancement factor of 50 was obtained at distances 100 nm above the surface. The resonance wavelength increases linearly with the distance between the two layers and varies with their thicknesses. Reduced scattering and enhanced absorption efficiencies of the interferometer at resonance wavelength were observed. The effect demonstrated here could be applied for studying both enhanced fluorescence and nanolasers.