A New Thermodynamic Approach to Multimode Fibre Self-cleaning and Soliton Condensation

A new thermodynamic theory for optical multimode systems is proposed. Theory is based on a weighted Bose-Einstein law, and includes the state equation, the fundamental equation for the entropy and a metric to measure the accuracy of the thermodynamic approach. The theory is used to compare the experimental results of two propagation regimes in multimode fibres, specifically the self-cleaning in the normal chromatic dispersion region and the soliton condensation in the anomalous dispersion region. Surprising similarities are found in terms of thermodynamic parameters, suggesting a common basis for the thermalisation processes observed in the two propagation regimes.