Mode coupling in plastic optical fiber

Abstract

This paper presents a theoretical investigation on the mode coupling and mode coupling induced attenuation in step-index plastic optical fiber under different launching condition. We solved numerically power flow equation of multimode optical fiber by explicit finite difference methods. In our calculation, we adopted mode coupling coefficient measured in Garito’s experiments , and supposed power distribution of incident beam have Gaussin form with respect to angle between beam and optical core axis. Under different incident angle and same beam width, we calculated power distribution at fiber output end when optical fiber length is 1,5,15, 20, 50m respectively. In shorter transmission distance, mode coupling isn’t evident, output power distribution is similar to input ones. With increasing of fiber length, power diffused gradually from high order modes to low order modes, and mode coupling finished in about 20m, where equilibrium mode distribution is achieved. In addition, we calculated mode-coupling induced attenuation of different width and launching angle Gaussin beam, with enhancing of beam width and launching angle , attenuation increased .