Bend birefringence in finite-cladding W-fibres

Birefringence of the fundamental mode in a slightly bent single-mode fibre is not normally discernable. However, experimental transmission spectra of finite-cladding W-type fibres exhibit a splitting which can be interpreted as bend birefringence in its cladding modes. Using a slab waveguide model and an appropriate transform, we determine the birefringence and show that it is quantitatively similar to that observed in the fibre.