Birefringence is the optical property of a material having refractive index that depend on polarization and propagation of light. These optically anisotropic materials are said to be birefringent.
Polarization mode converters may be fabricated in birefringent fibers using this scheme. In this case, it is necessary to orient the birefringent axes of the fiber at 45° to the illuminating beam. Two methods have been demonstrated to form such polarization converters. In order to use a nonbirefringent standard telecommunication fiber for a polarization mode converter, it must be made birefringent. The fiber can be wrapped on a cylinder of an appropriate diameter to induce a specific birefringent. The beat length of the modes in the fiber is a function of the bend-induced birefringence and may be changed by altering the diameter of the cylinder. The induced birefringent axes are along the radius and parallel to the surface of the cylinder, with the fast axis in the radial direction.
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