A sensitive measurement method for analyzing the central DIP region of MCVD fibers

A rapid, easy to use transmitted near field (TNF) measurement method has been developed for analyzing the central dip region of MCVD multimode graded-index fibers. Because the presence of the central dip degrades the inherent bandwidth of a graded-index fiber, diagnostic techniques that provide detailed profile information about the central core region of the fiber are especially useful. This profile information about the central core region of the fiber are especially useful. This profile information can be used in conjunction with etching techniques to reduce the width of the center dip. This should lead to improvement in the bandwidth of the resulting fibers. The measurement system used in this study is shown in Figure 1. A typical TNF measurement of a fiber sample takes about ten minutes. This time includes fiber end preparation with a cutting tool, fiber insertion and tuning of the test set, and data acquisition and storage by the computer. A comparison of TNF data with preform profile data will be presented.