Practical guides written from the field, for the field. The kind of guidance a senior tech would give a newbie, with the field reality intact.
A .sor file is an OTDR trace, and it won't open without the tester's software. Here's how to view one free in your browser — no EXFO or Viavi program to install — plus the same trick for .msor, .trc, and .json files.
An OTDR trace is just a line sloping down a graph — once you know the axes and the four things that show up on it (fiber slope, splices, connectors, the end), you can read a span in seconds. Dead zones, reflectance, and reading loss with markers, in plain terms.
Read the guideIf it came off a fiber tester, a .trc file is an OTDR trace — EXFO's version of a .sor. What's inside it, how to tell it apart from an IBM Java .trc that isn't fiber at all, and how to open one free in your browser.
A .msor file packs the 1310, 1550, and 1625 nm shots of one fiber into a single file instead of three loose .sor traces. What's inside it, why techs test at more than one wavelength, and how to open one free in your browser.
Step-by-step walk-through of the browser-based OTDR trace analyzer. Drop a file, read the headline numbers, work the event table, set pass/fail thresholds, and print a clean acceptance record. Includes a short video of the analyzer running on a phone in the field.
Read the how-toFiles came back with no cable ID, no Site A, no Site B — just a generic fiber ID on every one? You don't have to retest and you don't have to install anything. Fix the identifier fields and bulk-rename OTDR traces (.sor, .msor, .trc) and power-meter (.opm) files right in your browser, with find & replace across a whole job. The story behind the free File Editor & Rename Tool, and how to use it.
Read the postA long-haul build leaves you a mountain of test files — OTDR traces at every wavelength and direction, OLTS tables, inspection reports, every crew naming them differently. Drop the whole job in and get one repair verdict per fiber, an actionable repair summary, and an AI review that catches the unit errors and backwards shots before they turn into wasted truck rolls. The story behind the tool, and a real job it caught.
Read the postMeet the new Splice Matrix Builder. Read a cable stack, add the cables in and out, enter each cable's counts, and connect by count across the splice. Covers dead/XD spares, ribbon stacks, scanning a work print, and print/PNG/SVG export.
Read the how-toStep-by-step walk-through of the browser-based color chart builder. Pick a color standard, paste cable counts from a job sheet, scan a sheet with your phone, look up a single fiber, and order a printable PDF. Covers TIA-598-D, IEC 60304, and VDE 0888.
Read the how-toFiber Optic CC is gone. Here's a free browser-based fiber count chart builder — 6 to 6,912 fibers, supporting N. America, Europe, and International standards. Written for the techs who used the old app every day.
Read the postFix missing or wrong cable IDs, site names, and fiber IDs on OTDR traces. Edit the identifier fields in .sor, .msor, and .trc files, bulk-edit a whole batch at once, and save the corrected files — no native software, no signup. Runs entirely in your browser. Files never leave your device.
Open the editorDrop a .sor or .trc file and instantly see span length, total loss, reflectance, a pass/fail verdict, and a full event table identifying every splice and connector. Runs entirely in your browser. Files never leave your device.
Open the analyzerOTDR files are proprietary binaries, and parsing them yourself is a trap. Here's an API that returns span length, total loss, and the full event table as JSON from a .sor, .msor, or .trc — the same engine behind the free tools, in one HTTP call.
On a large build, acceptance review becomes its own project. An illustrative build-vs-buy scenario: a contractor who needed real-time, per-fiber results and integrated the parsing and pass/fail logic through the API instead of staffing a review team.
Read the guideA practical look at what fiber testing actually demands in the field. Why we test, what each tool is for, and when each one earns its keep. Covers VFL, light source and power meter, OLTS, OTDR, traffic identifier, and the CD/PMD measurements that only matter on long-haul.
Read the guideLoss test results (.jolts, .opm) are what data centers and hyperscalers actually save — and the one file type you can’t open in the field or report on without the vendor’s desktop software. How to read them on any device and build an acceptance report without FastReporter or a paid custom template.
Why this math matters in the field — and how one sheet of numbers separates real trouble from a problem the design baked in before anyone touched the fiber. Includes an embedded calculator with industry-standard per-wavelength attenuation; defaults to 1550 nm with 1310 / 1490 / 1625 nm under Advanced.
Read the guideChromatic Dispersion and Polarization Mode Dispersion — the two signal-distortion specs that show up on high-speed acceptance jobs and can shut a circuit down even when the loss budget looks clean. When you get asked to test them, how the tests actually work, and what you can fix on the ground versus what gets handed off. The anchor of a three-part series, with deep dives on PMD and CD to follow.
Read the overviewThe PMD half of the series. What polarization mode dispersion actually is, why fiber gets it in manufacturing and in the field, how the four common test methods work, and the cheapest-to-most-expensive order you work a failing span — walk the route, re-dress the stress, localize with a P-OTDR, then hand off.
Read the deep diveThe CD half of the series. What chromatic dispersion is, why G.652 / G.653 / G.655 behave differently, how it's tested with the phase-shift method, and the four layers where CD gets managed — including why modern coherent networks skip inline compensation and let the receiver DSP do all the work.
Read the deep diveAttenuation versus link loss, reading the manufacturer's spec on a reel of cable, OLTS bidirectional methodology, characterization records that hold up at acceptance, and the link loss math you do before you pull. With worked examples in both imperial and metric units.
Read the guideHyperscale data centers run on thousands of fiber optic cables — like a Telco CO or CATV head-end, just far larger. Counts of 1,728, 3,456, and 6,912, spliced in cabinets at up to 864 fibers a tray. What's inside one, and why the splicing and testing work is moving from rural FTTH builds to the data center.
Read the postWhat's different about 200µm fiber, what equipment you need, and what pitch correction is. Includes a side-by-side equipment table for current and older Fujikura, Sumitomo, and Inno splicers — what V-grooves and holders each one needs for 200µm work, and which ones aren't worth using for it.
Read the postWhat hollow core fiber is, why it matters, and where it's actually being deployed in 2026 — Microsoft Azure, financial services, telco trials, and hyperscaler AI interconnect. First piece in a series on the next generation of fiber. Later parts: installation, splicing, and testing.
Read the postMore guides coming. Testing procedure and hollow-core installation are next in the series.