Fundamental mode microbending loss in graded-index and W fibres

The microbending loss in single-mode or quasi-single-mode fibres is approximately determined from a calculation of the fundamental mode field in a fibre with constant curvature. The result of the microbending loss essentially depends on the spot size of the fundamental mode, only. The approximations are verified by studying a statistical model and by comparing the approximations with exact calculations in the case of W fibres.