In contrast to power and energy meters, which can directly measure the loss of fiber optic cable equipment, optical time domain reflectometers (OTDR) workÂ
indirectly. Optical Time Domain Reflectometer (OTDR) is made according to the principle of backward scattering and Fresnel inversion of light, using the backward scattered light generated when the light propagates in the optical fiber to obtain information about the attenuation, thus indirectly measuring the loss and fault location of optical fiber cables.