What do we mean by fibre characterisation?
Fibre characterisation is defined as conducting a comprehensive suite of tests on an installed link in order to assess its general quality, its compliance with the infrastructure specification, and its specific ability to support a particular application or applications. Fibre characterisation reveals how well the fibre will perform. This is important because, as data rates increase and systems become more complex, there are many factors that can impair system performance. Full fibre characterisation is recommended for any dark fibre contract.
Fibre characterisation should be carried out by professionals
Performing all the fibre characterisation measurements to produce accurate and reliable results is a skilled task. The analysis and interpretation of the test results in order to report on the quality of the fibre infrastructure and the ability of the link to support different applications and technologies, requires a lot of detailed knowledge and understanding.
You can learn how to carry out that testing on the Certified Fibre Characterisation Engineer course. On the CFCE course you’ll learn about these 7 measurements, how to do them, validate the results, and analyze the data to report on the quality of the fibre infrastructure and the ability of the link to support a range of applications and technologies.
Richard Ednay, OTT technical Director and developer of the globally recognised Certified Fibre Characterisation Engineer (CFCE) course, wrote the definition of fibre characterisation that is in ITU G.650.3. Beware of imitation courses. The real CFCE course is only available from OTT partners. Check with us if you are unsure.
How is fibre characterisation different from just testing fibres?
Well historically, when singlemode fibre links were commissioned it was common practice just to do insertion loss neasurements and OTDR testing to measure the losses of the installed links, usually at just two wavelengths: 1310nm and 1550nm. Hopefully the end faces of the connectors were also inspected or at least cleaned, but there wasn’t the range of automated connector inspection probes available that there are today to allow inspection of the connectors behind the patch panels. This reduced set of measurements, just ILM, OTDR and connector inspection is referred to in ITU G.650.3 as first level testing.
However, with DWDM optical networking systems and CWDM optical networking systems operating over wider wavelength ranges then the ability of the infrastructure to support these over wavelengths also needs to be verified. In addition, with data rates of 10Gb/s & 25Gb/s on direct detection systems then the dispersion characteristics of the fibre have become much more critical and additional tests are required including chromatic dispersion and polarisation mode dispersion (PMD). With PMD the performance of the fibre can vary significantly from fibre to fibre within the same cable and so it is often necessary to measure every fibre and keep detailed records of which fibres can support which date rates.
With systems using coherent detection for 100G+ then there is usually electronic dispersion compensation of CD and PMD, so the limits on CD and PMD are more relaxed. However, there have been a number of reported problems with some coherent systems that show all the signs of sensitivity to high levels of PMD that are likely to result in rapid fluctuations in the State of Polarisation, so avoiding high PMD fibres is still a good idea. The performance of these advanced systems often depends upon many characteristics of the installed link, and the design of the link is optimised based on the information from the fibre characterisation exercise. So most equipment vendors will still insist on fibre characterisation being done before they connect up their equipment. Some aspects of advanced coherent systems are also highly dependent upon the quality of the infrastructure, this is particularly the case for Raman amplifiers, so on the CFCE course you’ll also learn about what to look out for to make sure that Raman amplifiers will work effectively and give the required amount of gain.
The CFCE course is currently delivered by OTT’s training delivery partners in the UK, Ireland, USA and New Zealand. It may be possible to arrange courses onsite for company groups located in other regions. Some of their dates will be listed here. If you’d like to keep up-to-date with future dates for this course then why not follow us on your preferred social media.
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