An optical time domain reflectometer is a device which is used to check the integrity of an optical fibre system detect and locate faults in optical cables.
The optical time domain reflector sends out a series of optical pulses from one end of the cable. The light which is reflected is analyzed. This gives information about the state of the optical cable and its terminations. If there is a drop in the quality of the light of if the distorted, it can indicate a problem such as a cut or an improper splice joint.
The optical time domain reflectometer can also measure the attenuation of signals through the optical fibre.