  We present a numerical method for modelling noise in Stimulated Brillouin
Scattering (SBS). The model applies to dynamic cases such as optical pulses,
and accounts for both thermal noise and phase noise from the input lasers.
Using this model, we compute the statistical properties of the optical and
acoustic power in the pulsed spontaneous and stimulated Brillouin cases, and
investigate the effects of gain and pulse width on noise levels. We find that
thermal noise plays an important role in the statistical properties of the
fields, and that laser phase noise impacts the SBS interaction when the laser
coherence time is close to the time-scale of the optical pulses. This algorithm
is applicable to arbitrary waveguide geometries and material properties, and
thus presents a versatile way of performing noise-based SBS numerical
simulations, which are important in signal processing, sensing, microwave
photonics and opto-acoustic memory storage.
