Evaluation of techniques to model bend loss in multimode fibers for endoscopic application.

Bend loss from optical fibers can have positive applications, which need to be characterized and related to fiber curvature in a systematic approach to be useful. One potential application for optical fibers is a shape sensor for tracking flexible bodies in remote access environments, such as in endoscopy or boroscopy. We conducted a review of bend-loss characterization and evaluated several methods for characterizing bend loss in multimode optical fibers for an endoscopic shape-tracking application. Specifically, closed-form equation-based methods and numerical simulations were examined. Beam propagation method (BPM) simulations were determined to be the most applicable characterization tool. Results from simulations using BPM software were compared to experimentally obtained data. BPM simulation was sufficiently accurate for modeling 50 mum fibers but impractical for larger, multimode fibers.