In this technique, a short pulse of light is launched into the fiber under test. As the pulse propagates within the fiber, a small amount of light is continuously reflected back toward the source by the medium itself (Rayleigh Scattering).
By measuring the amount of backscatter as a function of time, the loss profile along the fiber is obtained.
This method is not very accurate since the loss at the front end and back end connector cannot be measured .
Moreover ,it assumes that the attenuation in the back scatter power is equivalent to attenuation in the transmitted power.