Polarization-maintaining fibers are specialty fibers with strong built-in birefringence, preserving the linear polarization of an input beam. In fiber optics, polarization-maintaining optical fiber (PMF or PM fiber) is a single-mode optical fiber in which linearly polarized light, if properly launched into the fiber, maintains a linear polarization during propagation, exiting the fiber in a specific linear polarization state; there is. Optical fibers always exhibit some degree of birefringence, even if they have a circularly symmetric design because in practice there is always some amount of mechanical stress or other effect which breaks the symmetry. Such fibers are thus high-birefringence fibers (HIBI fibers). This polarization degeneracy allows the two independent polarization states to easily couple when. In this article, the latest in FOC's series covering specialty fibers and their fabrication, we discuss polarization-maintaining (PM) fibers and the various approaches used to make them.
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