Analysis on causes of faults and OTDR waveforms for optical link management

This paper has analyzed reflection types and index distribution in optical links and the consequent OTDR waveforms for various causes of link faults. For the advanced fault identification, the changes of index distribution by fiber´s bend have been simulated by the conformal transformation method. Faults due to the connector´s misalignment originate from coupling loss; however, faults by the bend originate from tilted index distribution. The wavelength dependence of loss by the misalignment is directly opposite to that by the bend. Using the properties of the index distribution and wavelength dependence, the causes for the smooth decrease on OTDR trace could be identified exactly.