A SOR file is a data file saved in the Standard Optical Time-domain Reflectometer (OTDR) Record (SOR) format. It contains fiber trace data, which includes the distance, reflectance, loss, and fiber attenuation measurements, recorded by an OTDR instrument when testing a fiber optic cable.

The OTDR instrument sends optical pulses into the fiber, then collects light that has been reflected back from various points in the fiber. The instrument then measures the strength of the return pulses, which are known as "traces." The data is then transferred to a computer and stored in a SOR file, which can be viewed and analyzed by various programs, such as VeEX Fiberizer Desktop, Optixsoft TraceViewer, and VIAVI FiberTrace. NOTE: There are two versions of SOR files. The earlier version was developed by Bellcore and the newer version was developed by Telcordia.