Investigation of bend loss in single mode fibers with ultra-high-resolution photon-counting optical time domain reflectometer.

An intensity peak associated with fiber bending could be detected thanks to the use of an ultra-high-resolution photon-counting optical time domain reflectometer (OTDR) setup. The peak intensity is shown to be dependent on the curvature radius and angular distance of the bend. To account for such peaks, we propose a model based on modal mismatching and coupling inside the bend region and show that the model is highly consistent with the acquired data. Combining the information of the bend peak and bend loss, and taking advantage of the high dependence of the peak value with the local modal field parameter, the technique could be employed as an optical fiber local-parameter characterization method.