Normalization of single-mode fibers having an arbitrary index profile

A method is proposed whereby the propagation characteristics of a single-mode fiber having an arbitrary refractive-index profile may be expressed in terms of a newly defined equivalent step-index profile. The theory is based on the fact that the field distribution of the HE(11) mode of a fiber closely resembles the Gaussian profile. The method makes it possible to characterize a fiber from a simple measurement of the HE(11) mode spot size without making difficult index profile and core radius measurements. It is also found that the step-index distribution is suitable for single-mode fibers.