Рефлектометр | Optical time-domain reflectometer Your Ultimate Troubleshooter | Fluke Networks


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Оптический рефлектометр (OTDR): комплексное средство устранения неполадок

Марк Маллинс

So you’ve finished your fiber cable installation and are now on to the task of certifying the cable plant using an optical loss test set (OLTS) – it’s the tool you need for Tier 1 certification and the most accurate for measuring loss to ensure application support.

Unfortunately, you find some critical fiber links that far exceed your loss budget for the application. You now need to troubleshoot those links so you can fix the problems and move on to your next job. And the faster you can locate the problems, the faster you can fix them.

Testing with OptiFiber Pro OTDR

Your OLTS can’t tell you exactly where the loss is happening along the link, and you simply don’t have the time to inspect each failed links’ connectors for contamination or try to visually locate a potential break (which could be anywhere) using a visual fault locator (VFL). But if you’ve got an optical time domain reflectometer (OTDR), you can rest assured. It is, after all, the ultimate troubleshooting tool.

Reflections Tell You More

Problems with your fiber links can be caused by microbends, kinks and breaks somewhere along the fiber, contaminated connectors, faulty fusion splices and a variety of other field termination, cable management or installation mishaps. Thankfully your OTDR has the ability to detect reflected light, or backscatter, to locate and measure the loss of any of these events. Access to this level of detail with an OTDR also arms you with a complete picture of the fiber installation and the overall quality of the workmanship.

Even if the application will only use the lower wavelength for transmission, when troubleshooting with your OTDR, it’s best to test at both the 850 and 1300nm for multimode and 1310 and 1550 for singlemode. Normally, the higher wavelength would show a lower loss, but if the fiber is stressed, the higher wavelength will show significantly higher loss, and the problem will be easier to detect.

It’s also important to troubleshoot in both directions. A mismatched splice could look like a gainer (i.e., negative loss) in one direction and show too much loss (i.e., false loss) in the other direction. But if you do a bidirectional test that averages the loss (as required in Tier 2 testing), you’ll get the actual loss. Thankfully, Fluke Networks’ OptiFiber® Pro features a built-in SmartLoop Assistant that makes bidirectional testing easy.

It’s All About the Trace

OTDR graph reflective events for tester connectors, launch cords, connectors, mechanical splices, fusion splices, miss-matched fibers etc

При поиске неисправностей с помощью OTDR вы получаете графическую сигнатуру потерь оптоволокна по всей длине. Несмотря на свою кажущуюся сложность, график OTDR точно описывает испытываемую линию, каждая ее впадина или пик свидетельствуют о соответствующем типе событий.

Experienced OTDR users will recognize reflective events for tester connectors, launch cords, connectors, mechanical splices, fusion splices, miss-matched fibers and the end of the link. Они также знают, что небольшие всплески после окончания линии — это побочные эффекты, которые не стоит брать в расчет.

Event Map view with on screen help which characterizes the actual events

Но, если вы не специалист по анализу графиков сигналов, не волнуйтесь. The OptiFiber® Pro also uses advanced logic to interpret the trace and provide an EventMap that characterizes the actual events. Любые неисправности сопровождаются красными значками, чтобы вы могли быстро обнаруживать проблемы.

Кроме того, тестер OptiFiber Pro даже предложит действия по устранению любых проблем. Для этого нужно нажать на значок помощи в нижнем левом углу схемы EventMap. Now that definitely makes for an ultimate troubleshooting tool!

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