A method and apparatus for detecting excess absorption of therapeutic radiation at a bend in a fiber, and the possibility of imminent fiber failure, by monitoring stimulated radiation emission by phosphors in a coating of the fiber, the stimulated emission being caused by leakage of an aiming beam through the cladding into the coating. To accomplish the detection, a conventional monitoring method and equipment are modified to detect the absence of, or an interruption in, the stimulated emission, which is caused by separation of the coating from the cladding in the area of the bend as a result of the excess absorption.
