Propagation constant of single-mode fibers measured from the mode-field radius and from the bending loss

The propagation constant was measured directly using the fiber bending losses (FBI) at different wavelengths, the outcome was compared with the more indirect results of the mode-field radius (MFR) method, and the integration constant determined for the measured wavelengths. This constant was found to be reasonably wavelength-independent. The absolute value rests strongly on the propagation constant model, i.e. on the structure of its empirical formula. As a result it is proposed to use the simple MFR method to determine the relative wavelength dependence of the propagation constant, and to fix its absolute values with only one more complicated FBL measurement at a convenient wavelength.<>