This paper reports some theoretical and experimental investigations on the propagation of a pulse in long step-index optical fibers where mode conversion is present. We derive simple analytical expressions for the frequency response and the radiation pattern as a function of the fiber’s length provided the launching conditions are known. A comparison with experimental observations made on a 3-km long Corning fiber shows reasonable agreement. We conclude that the approximations used to obtain the simple analytical solutions are satisfactory for predicting the transmission characteristics of the fiber.
L. Jeunhomme, M. Fraise, and J. P. Pocholle, "Propagation model for long step-index optical fibers," Appl. Opt. 15, 3040-3046 (1976)