Abstract

Accurate measurements of the baseband frequency response of graded-index fibers are required both for quality assurance of fiber cables and for design of fiber transmission systems. As is well-known, the measured bandwidth is strongly affected by the launching conditions, that is, how the launched optical power is distributed among the propagating modes. This paper describes the experiments showing the dependence of the bandwidth upon the launching spot size and numerical aperture (NA). It is also reported that theoretical analysis can explain the experimental results especially for MCVD fibers.