  We present exact N-soliton optical pulses riding on a continuous-wave (c.w.)
beam that propagate through and interact with a two-level active optical
medium. Their representation is derived via an appropriate generalization of
the inverse scattering transform for the corresponding Maxwell-Bloch equations.
We describe the single-soliton solutions in detail and classify them into
several distinct families. In addition to the analogues of traveling-wave
soliton pulses that arise in the absence of a c.w. beam, we obtain
breather-like structures, periodic pulse-trains and rogue-wave-type (i.e.,
rational) pulses, whose existence is directly due to the presence of the c.w.
beam. These soliton solutions are the analogues for Maxwell-Bloch systems of
the four classical solution types of the focusing nonlinear Schrodinger
equation with non-zero background, although the physical behavior of the
corresponding solutions is quite different.
