  We analyse the superluminal propagation of narrow-band pulses at resonances
in dissipative media. The output waveform is an attenuated, undistorted,
time-advanced version of the input which can be interpreted as the result of
the interference of two scaled replicas of the input having a positive relative
delay. The proposed analysis applies both to the propagation in a passive bulk
medium at an electronic resonance and in a dielectric waveguide coupled to a
lossy micro-ring resonator. This latter case provides a clear insight of the
underlying physical phenomena.
