An Analysis of the Effect of Lossy Coatings on the Transmission Energy in a Multimode Optical Fiber

A thin lossy plastic coating applied to individual optical fibers is being considered as a means of decreasing crosstalk 1 between the optical fibers and as a mechanism for protecting the fibers during the cable-manufacturing process. The effect of the lossy coating on the transmission energy in a fiber is the subject of this paper. 2 3 A quasi-ray tracing approach is used to describe energy propagation in a multimoded step-index optical fiber with a lossy plastic coating. 4 5 An integral expression for the power transmitted in the fiber is developed in terms of the geometry of the round fiber, the intrinsic loss of the fiber core, the reflection coefficient at the core-cladding interface, and the energy distribution at the launching end of the fiber. To calculate the reflection coefficient at the core-cladding boundary, the strategy followed is to replace the round fiber by a lossy multilayered semi-infinite slab model. A computer evaluation of the integral expressions for the transmitted and input power has been made. Included in this paper are the results of a study showing the functional relationship between power loss due to a lossy coating and cladding thickness, mode energy distribution, numerical aperture, and wave length. 1531