An optical time-domain reflectometer (OTDR) is an optoelectronic instrument used to characterize an optical fiber. OTDR testing analyzes fiber optic cable performance from end to end by testing components along the cable, including connection points, bends, and splices. They are mostly used in the technology of optical fiber communications for testing fiber-optic links (e. They characterise the len th, attenuation and return loss (ov se individual events along ink: connection points (splices, connectors), te ng by particles much smaller than the wavelength of the. Shop handheld time domain reflectometers with color displays and comprehensive testing capabilities.