Analysis of polarization-mode coupling by acoustic torsional waves in optical fibers

Coupling of polarization modes of the LP01 spatial mode by acoustic torsional waves in an optical fiber is considered in detail. Analytic expressions of the coupling coefficients based on the combined effects of birefringence and photoelastic contributions are found. The results show that for regular fibers the birefringence component is the larger of the two. By the use of higher radial orders of the acoustic torsional modes, the coupling efficiency can be increased.