Transmission vs Transverse Offset for Parabolic-Profile Fiber Splices With Unequal Core Diameters

Abstract

A geometrical optics model is presented that is based on defining a local numerical aperture as a function of fiber radius with a uniform power distribution. Transmission vs transverse offset characteristics for parabolic-profile fiber splices are calculated for unequal fiber-core diameters. We show that the often-used assumptions of equal-mode excitation, equal-mode attenuation, and no-mode coupling are not adequate to calculate realistic transmission vs offset characteristics. Splice-loss measurements with long fiber lengths on each side of the splice show less than the calculated sensitivity to small offsets and greater than the calculated sensitivity to large offsets.