Abstract

The distribution of power among the modes in a multimode optical fiber is a function of two variables, for example, the azimuthal and radial mode numbers. Experimentally it is desirable to measure such distributions as a function of two orthogonal variables. In the case of step-index fibers it is quite simple, by measuring the far field, to extract a distribution of power as a function of propagation constant (β), and, since this is the most interesting parameter, the remaining one (which is much more difficult to extract) is generally ignored. An equivalent process is not possible in a graded fiber, and measurement in terms of two parameters is therefore necessary. Note that the distribution cannot be reconstructed by measuring, for example, the near and far fields, this being equivalent to measuring a two-dimensional distribution in two projections only, it being well-known that the reconstruction process now required is not generally possible.

© 1979 Optical Society of America