Single-mode, single-polarization fibers made of birefringent material

Optical fibers composed of highly birefringent material are studied. One of the two fundamental modes can be made leaky when the birefringence is sufficiently large. This suggests a novel single-mode, single-polarization fiber design that can be realized by stress-induced birefringence. The leakage rate is calculated by a perturbation method, which accounts for degeneracy between a bound mode and a packet of radiation modes.