CURVATURE INDUCED MODE-COUPLING IN LARGE-CORE OPTICAL FIBERS WITH STEP REFRACTIVE-INDEX PROFILES

A simple ray model is developed to approximate the output beam angle i ncrease caused by a symmetric bend with variable curvature in a large core optical fibre beam delivery system of the type commonly used in l aser material processing. The results are compared with experiments us ing curved fibres in the shape of half-cycle cosines with different ra tes of curvature change. The theoretical model was supported by experi ment, and is sufficiently simple for application in the design of an o ptical fibre beam delivery system.