What is the SOR file format?
.sor is the standard file format for OTDR (Optical Time-Domain Reflectometer) trace data, defined by Telcordia Technologies (formerly Bellcore) under specification SR-4731. OTDRs are instruments used by fiber-optic network engineers to test, characterize, and troubleshoot optical fiber cables - sending light pulses into a fiber and measuring back-scattered reflections over distance.
A .sor file stores a complete measurement trace from an OTDR instrument, including fiber length, signal attenuation, splice losses, connector reflections, and detected fault events. The format is binary and block-structured: the file consists of a sequence of named blocks such as Map, GenParams, SupParams, FxdParams, DataPts, KeyEvents, and Cksum. There is no single fixed magic number; parsers identify .sor files by recognizing readable ASCII block-name strings - especially Map - near the file start.
Two issues of the SR-4731 standard exist, and many OTDR manufacturers append proprietary extension blocks to the core structure. Related formats include .trc and .msor files, which some instruments produce as alternatives or supplements to standard .sor traces.
.sor files are opened and analyzed by dedicated OTDR management software such as EXFO FastReporter, Viavi FiberTrace, and AFL/Noyes TRM. The open-source pyOTDR library (Python) can parse .sor files on Windows, macOS, and Linux, and web-based SOR viewers allow quick inspection without installing local software.
Security & safety
RISK: LOWA .SOR file is inert measurement data - a binary trace with no scripts or executable code, so opening one is safe. The only real concern is using a trustworthy viewer: stick to the instrument vendors (Viavi, EXFO, AFL, Anritsu) or the open-source parsers (pyOTDR, otdrs) rather than ad-laden 'free OTDR viewer' download portals. The data itself can be business-sensitive (network topology/fiber routes), so handle as-built records accordingly.
Format details
in a nutshell- Corel Paradox Sort Definition - An auxiliary sort-order definition used by the long-discontinued Corel/Borland Paradox database - the meaning shown in this database, but rare in the wild.
- Source / SQL script (.sor) - Occasionally a plain-text source or SQL script file; readable in any text editor.
Programs that open SOR files
Windows4 apps
Viavi FiberTrace / OFS-355 (FiberCable)
Free Install Viavi's free SOR viewer/reporting tool, File > Open the .sor to plot the trace and read the event table. (Viavi = former JDSU.)
EXFO FastReporter
Freemium Open the .sor in FastReporter to view traces, edit events and batch-generate PDF acceptance reports (free viewer; full reporting licensed).
AFL/Noyes TRM (Test Results Manager)
Free Free SOR analysis/reporting software from AFL; open the .sor to view and report on traces.
pyOTDR
Open-source Command-line: 'pyOTDR file.sor' parses the trace and exports the data to JSON/CSV - vendor-independent, free. 
macOS1 app
pyOTDR
Open-source Run via Python to parse a .sor and export its data points/metadata to JSON or CSV on macOS. 
Linux1 app
pyOTDR / otdrs
Open-source Parse SOR to JSON/CSV from the command line (pyOTDR in Python, or the Rust 'otdrs' tool) for analysis or storage.
Online SOR viewer (Sor-Viewer / SOR Converter)
Free Upload a .sor to a browser-based viewer to plot the trace and read events without installing vendor software. Technical details
deep spec| Format type | Binary, block-structured; file is a sequence of named blocks as defined by Telcordia SR-4731 |
| Core blocks | `Map` (block directory), `GenParams` (general parameters), `SupParams` (supplier info), `FxdParams` (fixed parameters), `DataPts` (trace samples), `KeyEvents` (event table), `Cksum` (checksum) |
| File identification | No fixed magic bytes at offset 0; parsers recognize `.sor` files by readable ASCII block-name strings (first block: `Map`) embedded in the binary data |
| Numeric byte order | Little-endian (Intel) byte order for all multi-byte integer and floating-point fields |
| Trace data | Backscatter power levels sampled at fixed distance intervals along the fiber - typically thousands of data points per measurement |
| Event table | `KeyEvents` block records each detected event (splice, connector, fault) with loss, reflectance, and distance values |
| Wavelength coverage | Each `.sor` file covers a single test wavelength; multi-wavelength tests produce one file per wavelength |
| Distance range | Configurable via pulse width and sampling interval; instruments support ranges from a few hundred metres to 250+ km of fiber |
| Checksum | `Cksum` block contains a 16-bit FCS checksum computed over all preceding block data for integrity verification |
| String encoding | Text fields (fiber ID, operator name, location) stored as fixed-length, null-padded ASCII strings within each block |
| Vendor extensions | Manufacturers may append proprietary named blocks beyond the SR-4731 core; parsers should skip unrecognised blocks gracefully |
| MIME type | application/octet-stream (no dedicated IANA media type registered) |
| Open-source parsing | Supported by `pyOTDR` (Python) and `otdrs` (Rust) libraries on Windows, macOS, and Linux |
| Related formats | `.trc` (vendor-specific OTDR trace), `.msor` (multi-fiber SOR variant), `.otdr` (generic OTDR trace container) |
| Released | Bellcore/Telcordia SR-4731 (the SOR interchange format predates 2000; Issue 2 standardized later) |
| Open standard | Yes · royalty-free |
| Specification | telecom-info.njdepot.ericsson.net |
SOR conversions
Community Q&A
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