Coupled power equations for resonant optical fibre microbend sensors

Abstract

Coupled power equations, as originally derived by Marcuse [3] for weak mode coupling in optical fibres, are reformulated for application to resonant optical fibre microbend sensors. We show that the first-order perturbation theory approximations made in the derivation of the coupled power equations should not be used in the case of strong, highly resonant coupling, and that the coupled power equations are thus not necessarily valid when applied to resonant coupling as found in microbend sensors.