Theory of microbending loss in curved graded-index monomode fibres

The effect of pseudo-random transverse microscopic corrugations on the amplitude attenuation of the fundamental hybrid mode in curved graded-index monomode fibres is investigated. For the first time in the literature, a general formulation of microbending loss in local toroidal co-ordinates is presented. The formulation does not, in any way, depend on the existence of a large number of statistically identical and independent monomode fibres of which the given specimen is an ensemble averaged sample.This general formalism is used to derive an expression for the microbending coupling spectrum which encapsulates the essential analytical characteristics of both non-zero polarisation and curvature effects. Theoretical results of the wavelength dependence of excess microbending loss for two power spectral density functions along with their respective optimised statistical fibre parameters are investigated and show considerable improvement over previous studies