OTDR (Optical Time-Domain Reflectometer)

An OTDR is a measurement device that sends a light pulse into an optical fiber and analyzes the backscattered light (Rayleigh scattering) as well as light reflected from discontinuities, in order to diagnose the condition of a fiber route and locate faults.

How does an OTDR work?

Based on the return time of the backscattered signal, the OTDR calculates the exact distance to a given point in the fiber, and from the intensity of that signal — the attenuation of the route at that point. Sudden jumps in intensity indicate connectors, splices, or fiber damage (breaks, sharp bends).

Applications

An OTDR is a standard diagnostic tool during installation and maintenance of fiber-optic networks — it lets you locate a cable fault to within meters without physically searching the whole route, and verify splice and connector quality after installation.

Related terms

DTS

Chromatic dispersion

WDM