GENERAL-SOLUTIONS FOR STRESS-INDUCED POLARIZATION IN OPTICAL FIBERS

General solutions of thermal stresses and material birefringence in polarization-maintaining optical fibers are presented that give the stresses and birefringence at every point in the cross section of various fibers. The fundamental solution of the stress field is constructed by using the complex variable method in elasticity. When the cores, inner claddings, or stress inducing regions are ellipses, circles, or bow-tie shapes, exact closed-form solutions can be found. The average core birefringence and center core birefringence of elliptical core, elliptical cladding, twin core, Panda, and bow-tie fibers are calculated and compared. Among those fibers, the bow-tie fiber shows the highest birefringence. Bow-tie, Panda, and elliptical cladding fibers with small cores all have nearly uniform stresses and birefringence distribution in the fiber cores; however, the nonuniformity will increase with the size of the fiber core. In contrast, twin-core fibers always show a nonuniform stress and birefringence distribution in the core, even though the core is small. The birefringence of twin-core fiber is smaller by approximately one order of magnitude than other fibers studied.