OTDR tester tests a fiber cable's integrity. It builds, certified, maintains and troubleshoots fiber optic systems. They form a virtual image of fiber cable for determining the performance capability and condition of the fiber cable. It also helps in testing the components of a cable such as bends, connection points, or splices for analyzing the start to end capability of cables. The OTDR tester inserts a light pulse into the fiber cable from one end. The reflected signal that reaches the OTDR port helps us to know the results. A part of the light scatters and a part of it returns to OTDR. These reflections and scatters help us in getting important information about the cable. It tells us about losses as well as the distances to faults or connectors. Light while travelling, loses some of its part due to Rayleigh Scattering. The signal scatters irregularly through the fiber. The longer the backscattering, the stronger the power. It is important to set the OTDR parameters correctly to get accurate results. Auto-test function is enough in some cases to get accurate results.