A thermodynamic approach to linear cross-talk in multimode fiber systems

Optical thermodynamic theory is extended to low-power multimode fiber systems to characterize with simple thermodynamic models the complex scenario of power exchange induced by random mode coupling between propagating modes. It is theoretically and experimentally demonstrated that low-power multimodal systems can give rise to steady-states described by a weighted Bose-Einstein modal power distribution. The theory applies also at quantum power level, indicating that optical thermodynamics and quantum optics coexist, allowing the study of multimodal optical systems in both classical and quantum regimes and simplifying the design of SDM systems.