Composite solitons in optical systems with fast and slow saturable absorbers

We present a review of known and new theoretical results on short-pulse propagation in optical systems with either slow or fast saturable absorbers. The analysis is based on using a modified complex Ginzburg-Landau equation. We show that in addition to the normal "plain pulse" solutions, various other types of composite pulse solutions can exist. These composite solutions are formed from simpler solutions and may be considered as bound states of plain solitons or plain solitons and fronts. In the former case the bound states can be analysed using the "interaction plane" and balance equations.