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Cross Section of Polarization Maintaining Fibers:
Source of the figure: http://www.fiberoptics4sale.com/wordpress/what-are-polarization-maintaining-fibers/
The above three pictures illustrated the three different types of polarization maintaining fibers, which are Panda, Elliptical-clad, Bow-tie. There fibers contain a unique feature; they have stress rods in fibers (a feature not seen in other fiber types). The stress rods are two circles in the Panda PM fiber, a elliptical clad in elliptical-clad PM fiber and two bow-ties in the Bow-Tie type PM fiber. The most important property of stress rods is that it creates stress in the core of the fiber such that the transmission of only one polarization plane of light is favored.
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