High-birefringence optical fibers by preform deformation

High-birefringence optical fibers have been fabricated using a preform deformation technique in which an initially round preform is locally heated and squeezed from two sides. This technique has been used to make both polarization-preserving and single-polarization fibers. A novel feature of these new fibers is their rectangular shape which facilitates location of the principal axes and increases resistance to polarization breakdown from external perturbations. These fibers have circular cores, low loss, and excellent polarization holding.