Profile Characterization of Optical Fibers - A Comparative Study

Precise methods for measuring index profiles in both multimode and single-mode optical fibers and preforms are required if the desired ideal index distributions are to be produced. This paper will provide a comparison of four current state-of-the-art techniques for making these measurements on fibers and two similarly current methods used for preforms. Implications of the results especially related to the applicability and utilization of the various techniques will be discussed. It is important to have some feeling for the structure of the object being profiled. The fibers and the preform studied were produced by the modified chemical vapor deposition process.1 In this procedure a silica tube is mounted on a glass-working lathe and slowly rotated while reactants and dopants flow through it in an oxygen stream. An oxy-hydrogen burner is slowly traversed along the outside of the tube to provide simultaneous deposition and fusion of a layer of the reacting materials. On the order of 50 layers are deposited by multiple passes of the burner. To fabricate graded-index fibers, the dopant concentration is gradually increased with increasing layer number. At the conclusion of deposition, the temperature of the burner is 1335