Cooling of a soliton gas

Summary form only given. Temporal soliton pulses in optical fiber owe their usefulness as bits of optical information to their remarkable stability. Their particle-like behavior enables them to survive severe perturbations, like collisions with one another, spectral filtering, or even attenuation with subsequent amplification. Solitons will thus inevitably be generated from a wide range of initial conditions. When the fiber dispersion is anomalous, an ensemble of bright solitons is created. We have further shown that the soliton ensemble can exist in two distinct states, or phases. Either the individual solitons are in vigorous relative motion like particles in a fluid, or in an ordered state in which the solitons sit on a regular lattice. In analogy to thermodynamics these states are referred to as soliton gas and soliton crystal, respectively. The transition from gas to crystal can be obtained by reduction of the input power. Carrying the analogy further, one can think of the input power as being acting like a heat input, which drives the system away from thermal equilibrium until a balance between heat input and heat loss is reached. If this reasoning is valid, then it should be possible to obtain the phase transition not only through a decrease of the heat flux from the source but also by an increase of the heat flux to the sink-in other words, by cooling the soliton gas. We present evidence that selective removal of the hottest solitons from the gas will produce the phase transition.