Theoretical analysis of the evanescent wave absorption coefficient for multimode fibre-optic evanescent wave absorption sensors

In an optical fibre of circular cross section, leaky skew rays transmit pow er in a different way from trapped and meridional rays. In this paper, a th eoretical analysis of the evanescent wave absorption coefficient for leaky skew rays in multimode optical fibre evanescent wave absorption sensors is presented. Further, a comprehensive expression for the effective evanescent wave absorption coefficient is obtained. Some numerical results are given to illustrate this theoretical analysis. This work could be applied to opti mize the design of fibre-optic evanescent wave absorption sensors.