Power Coupling Between Light Diffusing Fibers: Modelling and Validation

The power coupling between two light diffusing multimodal optical fibers of equal and finite lengths that are parallel oriented, and which are coupled through scattering processes, is investigated both theoretically and experimentally. In particular, a simple analytical model of the inherent coupling coefficient, derived according to a perturbation approach in a weak-coupling regime, is developed. The modelling results have been compared with the measurements performed, as a function of fiber distance and coupling length at three different wavelengths, and a close agreement is proved. The obtained results provide a better understanding of the power coupling mechanism and of the inherent functional dependence on the main structural parameters of the two-fiber configuration.