Optical Time Domain Reflectometers are the epitome of active fiber optic measuring tools. Our OTDRs include also functions of Power Meter(OPM), Laser Source (OLS) and Visual Fault Locator (VFL) for a complete and indispensable tool for the fiber plant and fiber network engineers. An OTDR allows a complete diagnostic of a fiber circuit. It is strongly recommended that each fiber segment before being put into production should be tested and certified using an OTDR. Losses/attenuations at various wavelengths and in different places across a fiber segment can be detected and measured with the help of an OTDR.