Effect of anisotropy of a single-mode fibre on lightning-induced rotation of polarisation of a light signal in an optical ground wire

A numerical model is constructed for calculating lightning-induced rapid changes in the polarisation state of a light signal at the output of a fibre-optic communication line with an optical ground wire. It is shown that taking into account anisotropy of real optical fibres has a noticeable effect on the shape of the polarisation rotation speed time profile. It is found that the maximum rate of change in the polarisation state and its temporal profile depend on the location of the lightning strike in the fibre span, the magnitude of fibre anisotropy and the direction of propagation of a light wave.