How to read a .sor file: OTDR traces explained
A .sorfile is the raw output of an OTDR test — a fiber's signature as a curve of reflected light over distance. otsora parses .sor files in your browser and turns them into a readable trace, a key-events table and a Good/Caution/Bad health verdict.
What is a .sor file?
.sor stands for Standard OTDR Record, the interchange format for OTDR measurements defined by Telcordia (formerly Bellcore) standard SR-4731. It is a binary file that stores everything one acquisition captured: the trace data points, the detected events, and the test parameters (wavelength, pulse width, range, refractive index and units).
Because the format is vendor-neutral, a .sor written by an EXFO, Viavi (JDSU), Anritsu or Yokogawa OTDR can be read by any tool that understands SR-4731 — including otsora.
What is an OTDR trace?
An OTDR (Optical Time-Domain Reflectometer) sends pulses of light down a fiber and measures how much scatters back over time. Light travels at a known speed in glass, so time maps to distance — the result is a curve of returned power (in dB) against distance (in km).
A healthy fiber shows a steady, gentle downward slope (uniform attenuation), small steps at splices, taller reflective spikes at connectors, and a final Fresnel reflection at the fiber end. Reading those features is how you locate faults, measure loss, and find the end of the link.
How do I read or parse a .sor file?
You don't need the OTDR vendor's desktop software. Open the free otsora viewer, drop in a .sor file, and otsora parses it and renders the trace, the key events and a verdict in seconds. It works on traces from every major OTDR maker because they all write the SR-4731 format.
Open the .sor viewerWhat does otsora analyze?
For each .sor trace, otsora reports:
- Key events — reflective and non-reflective events along the fiber, with distance and loss.
- Attenuation — overall loss in dB and the slope in dB/km.
- Splice loss — the worst splice/event loss on the core.
- Length — the measured fiber length to the end event.
- A health verdict — Good, Caution or Bad, from the worst splice loss and slope against field thresholds.
On Pro, otsora analyzes a whole cable: upload every core and it ranks repair locations by how many cores are affected, so you go straight to the splice that matters.