Analysis of etching-induced birefringence changes in elliptic core fibers

A mathematical model is presented that predicts birefringence changes in an optical fiber as the cladding is removed. This model approximates a highly elliptical fiber core with a rectangular dielectric waveguide. The birefringence calculations obtained with the model compare well with experimental evidenceobtained with real-time birefringence monitoring during cladding removal by chemical etching. The information is used to control the amount of cladding removed from a D fiber to within approximately 0.05 microm for use in the production of passive optical fiber components.