Reflectogram

A reflectogram is a graphical representation produced by optical time-domain reflectometry (OTDR) that shows the intensity of light that is reflected or backscattered from an optical fiber as a function of distance along the fiber. The measurement is made by launching a short light pulse into the fiber and recording the returned signal over time; distance is inferred from the travel time of the pulse, accounting for the fiber’s refractive index.

On the trace, the baseline backscatter forms a general profile, while spikes typically indicate discrete events such as connectors, splices, or faults where Fresnel reflections occur. Drops or changes in the slope indicate attenuation along fiber segments. The height and shape of events yield estimates of connector losses, splice losses, or damage location. OTDR traces may also reveal gradual changes in attenuation and detect bends or breaks that affect signal integrity.

Reflectograms are used for installation verification, fault locating, characterizing fiber routes, and maintaining optical networks. They provide a non-destructive, single-ended test that can be performed in some cases while the network remains in service. The trace is commonly analyzed with an accompanying event table listing positions, estimated losses, and remaining attenuation budget.

Interpretation requires calibration and expertise, and several limitations apply. Resolution depends on the transmitted pulse width; the dynamic range and noise can obscure small features; strong reflections can create dead zones where nearby events are difficult to resolve. Nonetheless, reflectograms are a standard diagnostic tool in fiber-optic testing and network maintenance.