Microbending losses of bow-tie and similar anisotropic fibres

In the letter the microbending behaviour of bow-tie fibres is investigated theoretically. Our results for the practically existing case of unequal core and cladding anisotropy agree satisfactorily, in a statistical sense, with the published experimental data. In the ideal case of equal core and cladding anisotropy, our results confirm the prediction by Snyder and Rühl that the polarising behaviour of a long bow-tie fibre with microbends is caused by the `small field? effect. The related but different problem concerning bow-tie macrobends is treated in another letter.