Now a day all the telecommunication industries are using fibers for faster data communication and long distance communication. Fibers use light as the information and it is carried over long distances. Optical fiber has large advantages over a copper and co-axial cable because of its lower attenuation and interference. Optical time domain reflectometer (OTDR) is also one of the important devices using in telecommunication industries to characterize an optical fiber. This article deals with the study of long distance backbone single mode fiber and their features are discussed with the use of an OTDR. The results of this article focused on the losses and breaks of the fiber with the events. The Single mode OTDR is used to find the events, losses and breaks of the backbone fiber between the two locations. This work will give a way to study the nature of optical fibers and understand the practical application of optical fiber communication.