Mode-field diameter measurements for single-mode fibers with non-Gaussian field profiles

The mode-field diameter (MFD) of a single-mode fiber can be measured using several different techniques. The extent to which these techniques are consistent depends upon the definition used to compute the MFD and upon the fiber design. In this paper, three measurement techniques (far-field scan, offset joint, and knife-edge scan) are applied to the measurement of both conventional step-index fibers and to non-step-index dispersion-shifted fibers. Using the far-field second moment definition, which is often called the "Petermann 2" definition, measurements made using these three techniques agree to within 1.6 percent.