A thermodynamic study of low-power modal multiplexed systems

Modal multiplexing is a part of the more general space-division multiplexing (SDM) technique, aimed to solve the capacity crunch issue adding a further multiplexing layer using multimode fibers. SDM system designers often assume that groups of degenerate modes do not exchange power, and that the linear random-mode coupling (RMC), caused by fiber imperfections, induces power exchange among quasi-degenerate modes only. In our experimental and theoretical study, me show that RMC produces asymmetric power flow among modal groups, promoting the lower-order mode groups at the expense of the higher-order groups. The study, completed by a thermodynamic interpretation, is aimed to improve the design of SDM systems against RMC.