This paper presents the approximate estimation of PMD in optical fibre, that arises in consequence of electromagnetic field of lightning stroke to earth in vicinity of fibre cable. Estimation is based by analogy with account of PMD in fibre with eccentricity. Small rotation of the polarization plane of lights in fibre under influence of lightning fields causes the same distribution of orthogonal modes to main axis as a small eccentricity. Estimation can be made by this method if rotation is less than 20 grad.
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