A coherent double spectral method for measuring the parameters of single-mode optical fibers with strong linear birefringence
In this work, a coherent spectral method for measuring the parameters of anisotropic optical fiber with taking into account polarization dispersion of refractive indices (RI) and possible angular mismatches of birefringence axes of the circuit optical elements has been analyzed thoroughly. Using the Jones matrix method, the measuring polarization interferometer was treated and the relationship between its characteristics and circuit parameters was obtained. The deviations of the axial angles from the optimal ones were shown to lead to a decrease in the contrast of the output interference signals and to the appearance of parasitic spectral components. Analytical expressions for the birefringence and beat length of polarization modes having regard to the RI dispersion, as well as for the spectral transfer function (STF) of the polarization interferometer and its Fourier image were derived. The features of the application of the described method for measuring the key parameters of three types of birefringent fibers were experimentally demonstrated.