OTDR is a precision photoelectric integrated instrument made using the backscattering of Rayleigh scattering and Fresnel reflection when light is transmitted in optical fiber. It is widely used in the maintenance and construction of optical cable lines. Fiber length, transmission attenuation, joint attenuation and fault location can be measured.
The OTDR test is performed by emitting light pulses into the fiber and then receiving the returned information at the OTDR port. When light pulses are transmitted in the fiber, scattering and reflection occur due to the properties of the fiber itself, connectors, junction points, bends, or other similar events. Some of the scattering and reflection will return to the OTDR. The useful information returned is measured by the OTDR detector, which acts as a fragment of time or curve at different positions in the fiber. The distance can be calculated by determining the speed of light in the glass material from the time the signal is emitted to the return signal.