Two-way or bi-directional OTDR testing is essential for a comprehensive evaluation of fiber optic cables, providing insights into network integrity, fault localization, and overall performance, ultimately ensuring the reliability and efficiency of communication networks. Bi-directional testing ensures accurate assessment. Verification of. In the 2014 version of ISO/IEC 14763-3, testing of optical fiber cabling, unidirectional testing for permanent links is required. Because the distance and attenuation measurements are based on optical light backscattering and Fresnel reflection principles, scattered and reflected light photons can be analyzed at. ic system. On the home screen, tap the Next ID panel.