OTDR is called Optical Time Domain Reflectometer, which injects narrow light pulses into the fiber end face as a detection signal. When the light pulse propagates along the fiber, the backscattered part of Rayleigh scattering everywhere will continue to return to the incident end of the fiber. When the optical signal encounters a crack, Fresnel reflection will occur, and the back reflected light will also return Optical fiber incident end.

Rayleigh backscattering and Fresnel reflection will occur when light propagates in an optical fiber. OTDR takes advantage of this feature of light and collects light pulses by backscattering and reflection in the path. High-tech, high-precision photoelectric integrated instrument.

Through suitable optical coupling and high-speed response photodetector to detect the size and arrival time of the back light at the input end, the transmission characteristics, length and failure points of the optical fiber can be quantitatively measured.