Relation Between External Stresses and the Degradation of Extinction Ratio of Polarization Maintaining Fibers

An analytical model is established for described the relation between packaging induced external stresses and the extinction ratio of polarization maintaining fibers. Fiber packaging inevitably introduces stresses to the fiber. While axial and axially symmetric stresses do not degrade the extinction ratio of the polarization maintaining fiber, other types of stresses generally do. Except when coinciding with the fast or slow axes of the polarization maintaining fiber, external stresses are superimposed to the intrinsic stresses of the fiber in such a way that the orientation of the resultant principal stress axes, i.e., the fast and slows axes, of the fiber changes. As a result, a light vector initially aligned with either the fast or the slow axis of the fiber will propagate along the externally stressed section of the fiber with an angle with respect of the rotated fast or slow axis of the fiber, degrading the extinction ratio.