Threshold design in fiber termination identification using local injection and OTDR

Abstract

We study how to set a threshold for how to identify the end of an optical fiber by reflectance ratio between wavelengths calculated from measurements of a temporary optical coupler (TOC) and a two-wavelength Optical Time Domain Reflectometer (OTDR). The threshold is affected by the difference in propagation loss between the wavelengths from the OTDR to the end of the optical fiber. The effectiveness of the threshold is inferred from measurements of the reflectance ratio of an Optical Network Unit (ONU) used for a Passive Optical Network (PON) and the propagation loss difference between the wavelengths of the TOC. The threshold adaptation conditions are also explained. Our results show that even with the worst propagation loss of existing single-mode fiber standards, it is possible to identify fiber ends 3.8 km away. However, if large bending or connection losses occur between the OTDR and the fiber end, the propagation loss difference between the wavelengths of the TOC must be improved.