Propagation of broadband optical radiation in a spun high-birefringent fibre

The evolution of the polarisation state of the broadband optical radiation, propagating through a spun high-birefringent fibre is studied. A theoretical model describing the polarisation state of the radiation in the spun fibre depending on the input polarisation parameters is developed. The model is based on the geometric analysis of the polarisation states of the spectral components of the radiation on the Poincare sphere. It is shown that when the propagation path length of the radiation in the optical fibre exceeds some value (the coherence length), the spectrum-averaged polarisation state of the output light is determined only by the parameters of the spun fibre, while the degree of polarisation of the output radiation depends on the input polarisation state.