Axial stress and its effect on relative strength of polarization-maintaining fibers and preforms

A method is given for the calculation of axial stress in polarization-maintaining optical fiber and preform. Detailed calculations are presented for circular side-lobe (CSL) and bow-tie fibers and preforms. The axial-stress results explain why preforms are more fragile than fibers in these designs. On the other hand, the stress analysis also shows that these fibers are more crack resistant at the surface than conventional single-mode fibers. To reduce the fragility of the fiber, it is suggested that a larger drawing tension be used during the fiber pulling process.