Analytical solution of bow-tie fibres

In the letter we attempt to treat theoretically the complicated profile structure of a polarising bow-tie fibre. The mathematical steps taken in our analysis include the use of a Fourier expansion of the index profile and an iterative technique to obtain the Green functions of the optical field. Numerical examples show that a bow-tie fibre with the usual profile structure has higher leaky losses than the predicted leaky losses of an anisotropic step-index model.