Constant-curvature loss in monomode fibers: an experimental investigation

A new technique for the measurement of constant-curvature (bend) loss as a function of bend radius is described, and it is shown that the influence of transition (microbend) losses can be essentially eliminated. Based on this technique and via the application of curve-fitting procedures and the Newton-Raphson method for two variables, a sensible equivalent step index can be obtained if stress-induced changes in the bent fiber are taken into account. However, the prediction of bend losses at other wavelengths is coarse, and it is shown that, for our fiber, agreement between theory and experiment can be considerably improved via an empirically deduced stress-induced dependence that is far stronger than predicted by published theory.