Reflectograms

Reflectogram is a graphical representation of reflected signals as a function of time or distance, produced by sending a probe signal into a medium and recording reflections from interfaces or defects. The technique is used in optical time-domain reflectometry (OTDR), electrical time-domain reflectometry, ultrasound, radar, and other forms of reflectometry.

In practice, a reflectogram plots the amplitude of the back-reflected signal against distance (or time), with peaks indicating interfaces or discontinuities in the medium. From the positions and magnitudes of these peaks, one may estimate layer thickness, location of faults, or impedance changes.

In fiber optics, OTDR traces are a common example of reflectograms, used to assess fiber continuity, loss, and to locate breaks or connectors along the fiber. Similar traces are used in non-destructive testing and medical ultrasound to visualize internal features such as voids, inclusions, or structural defects.

Processing of reflectograms often includes baseline correction, normalization, filtering, and sometimes deconvolution to improve resolution and feature visibility. Interpretation requires calibration against known standards and awareness of factors such as signal attenuation, multiple reflections, and noise.

Limitations of reflectograms include resolution constraints set by the probe pulse bandwidth and system sampling rate, potential ambiguities from overlapping reflections, and sensitivity to loss and noise. Despite these challenges, reflectograms provide a versatile, noninvasive means to characterize layered structures and detect anomalies across disciplines.