OTDR Viewer
Open & Read .sor Files Free

Drop in a .sor OTDR trace file to see the full trace graph and detected events, then drag markers onto the trace to read the footage between any two points. Runs entirely in your browser — nothing is uploaded.

📈 OTDR Viewer
Trace graph  ·  Key events  ·  Marker & footage readout
📁
Drop a .sor file here, or click to choose one
Stays entirely on your device — nothing is uploaded anywhere

What's in a .sor File?

A .sor file (Bellcore/Telcordia SR-4731 format) is the standard trace file every OTDR (Optical Time Domain Reflectometer) exports. It stores the full backscatter trace curve, the instrument's settings (wavelength, pulse width, index of refraction), and a list of key events — connectors, splices, and the fiber end or break — that the OTDR auto-detected.

This viewer reads that binary file directly in your browser using the File API, decodes the trace and event data, and draws it exactly like the OTDR's own software would — no proprietary software or upload required.

Measuring Footage Between Two Points

Every OTDR trace plots distance (in feet or km) against signal loss (in dB). To find the real-world footage between any two points on the fiber — say, between a known landmark and a suspected fault — drop the A and B markers on those two points.

  • The readout shows each marker's distance from the launch point
  • The difference between them is the footage you're after
  • The dB/km figure between them tells you the loss rate over that span, useful for spotting a bad splice or macrobend

Reading a Trace: What to Look for First

A raw OTDR trace can look intimidating the first few times — here's the order experienced techs actually read it in:

  1. Check the launch cable region first. The first few hundred feet of any trace sit inside the OTDR's own dead zone (see the Dead Zone Calculator) — a real event there can be masked or misread. If your trace starts right at the connector with no launch cable, treat any event in the first 100–300ft with suspicion.
  2. Scan for sharp downward steps. Each vertical drop is a discrete event — a connector, splice, or bend. A drop of 0.3–0.5 dB is a normal splice; anything over ~1 dB on a single fusion splice deserves a second look.
  3. Find the true end of fiber. A clean break or open connector shows as a sharp upward reflective spike followed by the trace dropping to the noise floor. A gradual slope to nothing (no spike) usually means a macrobend or a very lossy break rather than a clean cut — useful information when you're briefing a repair crew.
  4. Cross-check total loss against expectation. Multiply the fiber's rated attenuation (dB/km) by the total length shown, add roughly 0.1–0.2 dB per splice and 0.5 dB per connector, and compare that estimate to what the trace actually measured end-to-end — the Fiber Loss Calculator will do this arithmetic for you.

Frequently asked questions

Does this work with .sor files from any OTDR vendor?
The .sor format (Telcordia SR-4731) is a shared industry standard, so files from EXFO, Viavi, AFL, Fluke Networks, and other major vendors all use the same underlying block structure. Minor vendor-specific extensions exist, but the core trace curve and key-event data this viewer reads are standardized across them.

Is my trace file uploaded anywhere?
No. The file never leaves your device — it's read and parsed entirely in your browser's memory using the File API, the same way opening a local photo in an image editor doesn't upload it anywhere.

Why does my marker's distance not match the fault's actual GPS location?
OTDR distance is measured along the glass fiber itself, which includes slack coiled in every splice enclosure along the route — it's always longer than the straight-line ground distance. Use the Cable Slack & OTDR Distance Correction tool to convert your marker's OTDR distance into an accurate real-world location.

Related Tools

OTDR Dead Zone Calculator
Check whether an event near the start of your trace is hiding in the dead zone.
Cable Slack & Distance Correction
Convert the OTDR's measured distance into the real-world ground location of a fault.
Optical Path Calculator
Cross-check your trace's total loss against a calculated power budget for the link.