Coupling (launching) efficiency for a light-emitting diode,optical fibre termination

A ray tracing technique is used for calculating coupling efficiency between a light-emitting diode (LED) and an optical fibre. With an air interface, efficiency is estimated as a function of separation, waveguide diameter and source diameter, estimates are obtained using numerical methods. Initially the treatment considers a uniform source and is subsequently extended to Lambertian and weighted Lambertian distributions. The effect of numerical aperture on coupling coefficients is described.