INTELLIGENT BRANDS // Cabling

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In this latest whitepaper from Excel Networking, the company discusses one of the most basic and important procedures for the maintenance of fibre optic systems is to clean the fibre optic equipment.

Any contamination in the fibre connection can cause failure of the component or failure of the whole system. Even microscopic dust particles can cause a variety of problems for optical connections. In a survey carried out by Fluke Networks they claim that 85 % of the failing links can be attributed to‘ end-face contamination’.

To illustrate this it can be compared to a typical human hair which is between 50 and 75 micron. A dust particle can be as little as 9 micron and is pretty much impossible to see without a microscope. Despite this it could completely block a single mode fibre core, and if trapped between two fibre faces it can even scratch the glass, damaging the end-face. If this happens then at best it will require the careful and time consuming process of being polished out and, at worst, it will have to be replaced.

A recent incident was reported claiming that fibre cable was failing after less than 10 years of use, when it shouldn’ t degrade at all over this period of time. The first clue to the culprit of the problem was that the building and cabling infrastructure had transferred ownership on two separate occasions during this time. Each time, there was a massive opportunity to introduce contamination, which in reality is what had occurred.

There are many excellent documents which cover the correct procedure for cleaning and inspecting fibre optic end-faces, however we should always defer to the standards if they are available. In February 2010 the British Standards Institute published BS EN 61300-3-35 Examinations and Measurements- Fibre optic connector end-face visual and automated inspection. This document outlines the criteria for the number and details of the scratches and defects that can appear on the

Furthermore, with high power lasers now in use, if the contamination remains in place when the laser is turned on it can actually be burned into the end-face to such an extent that it cannot be polished out.

Whilst this may seem extreme consequences, each time you disconnect and re-connect a fibre connector problems can be re-introduced; a statement backed by a study carried out by NEMI( National Electronics Manufacturing Initiative)

The study showed that mating caused loose contaminants to spread. Through connection, a significant amount of the particles were transferred from the contaminated connector to the clean reference connector in a pattern similar to that seen on the contaminated connector.

Even the use of‘ dirty’ dust caps can have a significant impact on the‘ cleanliness’ of the fibre installation. The oil from human skin can also have a dramatic effect when viewed under a microscope.

48 INTELLIGENTCIO www. intelligentcio. com