  We present a novel approach to cascaded stimulated Brillouin scattering and
frequency comb generation in which the multitude of interacting pump, Stokes,
and anti-Stokes optical fields are described by a single forward wave and a
single backward wave at a single carrier frequency. The envelopes of these two
waves are modulated through coupling to a single acoustic oscillation and
through four-wave mixing. Starting from a single pump field, we observe the
emergence of a comb of frequencies as the intensity is increased. The set of
three differential equations derived here are sufficient to describe the
generation of any number of Brillouin sidebands in oscillator systems that
would have required hundreds of coupled equations in the standard approach. We
test the new approach on some published experiments and find excellent
agreement with the results.
