Far-field power-distribution measurement in axially symmetrical and nonsymmetrical fibers using a variable-width slit

A method for the measurement of the far-field power radiation pattern in axially symmetrical and nonsymmetrical single-modeoptical fibers is proposed. The method, based on monitoring of the power passed through a variablewidth slit in the far field, gives the power distribution as an associated Gauss-Laguerre expansion. The experimental setup permits the study of the power distribution and mode-field diameter dependence on the wavelength. Results for different types of single-mode optical fiber, including polarization-maintaining types, are presented.