LIAM TAYLOR CLEANING FIBRE
Fibre optics play an important part in our everyday lives, writes Liam Taylor , European Business Manager, Fibre Optics, MicroCare UK Ltd. It keeps us engaged with the modern world by quickly carrying vast amounts of information across its connections to our businesses, healthcare facilities, military operations, transportation hubs and homes. Reliable, fast connectivity is vital to these functions. Therefore, any threat to a network’s operation or bandwidth capabilities must be managed to help prevent poor performance, latent speeds or complete network shutdown. Contamination on fiber optical interconnects is one of the most common threats to a fibre optic network. There are several sources of contamination, but one of the most challenging to manage is dust. Add electrostatic charges (ES) and it exasperates the dust problem further. MANAGING THE DAMAGE: THE EFFECT OF STATIC ON FIBRE OPTICS
WHAT IS ELECTROSTATIC CHARGE? ES attracts dust and traps it on ceramic and composite ferrule end faces. The ferrules and the glass fibres within are dielectric and act like an electrical insulator that can hold that static charge for months. As a result, charged dust particles are attracted to the oppositely charged connectors. In many cases, dust sticks not only to the outer areas of the connector, but also to the ferrule apex in the contact zone, where it does the most harm. Contact friction is one of the most common ways electrostatic charges are generated on end faces or ferrules. Contact friction typically happens when end faces are mated or their protective end caps are removed. Because fibre end faces are made of non-conductive materials such as plastic, ceramic, glass, or epoxies, the static charge, also known as a triboelectric charge, does not have a path to dissipate. The dust, attracted and trapped by the ES, can change the light’s index of refraction, or the route of the signal through the fibre. This may result in insertion loss which weakens the signal, slowing down the network speed. There is also the possibility of a complete system
To further complicate matters, most fibre end faces are designed with convex geometry to reduce back reflection. Although it works well for the intended job, it encourages static charge to concentrate at the contact region of the mated connector pair. WET TO DRY WIPING When cleaning a fibre optic end face, some technicians use a dry wipe or cleaning stick, but this dry wiping action typically causes more of triboelectric charge build-up and attracts airborne dust to the connector end face. In addition, the friction of the dry wiping can also encourage the shedding of fibre particles from the wipe or stick. This will immediately bond to the area being cleaned, increasing the problem further.
shut down if the refraction angle is altered enough that no signal can be transmitted at all. The ES problem is heightened with the use of higher fibre count cable. In recent years, cables are being tightly packed with higher counts of fibres to increase bandwidth capacity and transmission speeds while maintaining a smaller footprint. As a result, typical fibre counts of 5,184, and UHCF (ultra- high-count fibre) cables of 6,912 fibres are becoming the norm. But, the higher the fibre count, the more vulnerable the fibre cable and its connections are to contamination. Connector construction and its material composition can also increase the chance of electrostatic charge problems. A good example is multi-fibre connectors. Newer 16-fibre arrays are replacing traditional 12-fibre arrays but still use the same 2.5-mm x 6.4-mm standard MT ferrule footprint. These connectors are not only denser, but they are also made from 80% glass, making the removal of dust problematic. Although glass helps improve thermal expansion control, it also retains more static than other types of connectors.
One of the best ways to combat ES buildup and remove the dust
contamination from a charged end face is to replace dry wiping with the ‘wet to dry’ cleaning method. Not only is wet to dry cleaning effective, it meets the strict industry standards upheld by industry bodies like the IEC (International Electrotechnical Commission) and iNEMI (International Electronics
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| ISSUE 30 | Q3 2022
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