by Liam Taylor, European Business Manager, Fibre Optics, Microcare
Although invisible to the naked eye, electrostatic charge (ES) can cause havoc to a fibre network. ES attracts dust to the ceramic and composite ferrule end faces, which can negatively affect network reliability and system performance if it is not effectively removed.
Contamination on fibre optical interconnects is one of the biggest threats to a fibre optic network, particularly 5G’s sensitive technology which requires every milliwatt of power to guarantee its superfast speeds and increased data volume requirements. If connector cleaning is not performed correctly, problems such as insertion loss (weakened signal) or back-reflection (signal diverted back to its source) are common. If the contamination is severe, the light’s refraction angle can alter enough for the optic signal to be lost entirely, causing a total system shutdown.
Therefore, it is critical to implement fibre connector cleaning procedures to remove the threat of contamination, especially ES and dust, to guarantee optimal network operation, uninterrupted connectivity and high-speed operation.
Dust-based contamination originates from many sources. Airborne dust can come from dead skin, plant pollen, vehicle emissions, cardboard boxes, and clothing lint. However, the primary source of contamination is through connector wear debris.
Wear debris dust is created by contact friction as the connectors are mated. The connector slider, the retention clips inside adaptors and transceivers, and even the guide pins rubbing against each other create microscopic dust particles which, if not removed, can grind into the ferrule surface, resulting in scratched, pitted or scarred end faces.
Electrostatic charge makes dust contamination even more problematic, as it attracts dust particles to the fibre and locks it in place. Therefore, all fibre end faces, including those new and straight out of the pack, must be thoroughly cleaned during installation or maintenance operations to prevent 5G network interference or failures.
How is an Electrostatic Charge Created?
Electrostatic charge, or ‘triboelectric charging’, takes place when certain materials become electrically charged after coming into contact with a different material, and are then separated.
The most common way that ES is generated on end faces or ferrules is from contact friction. This usually happens when end faces are mated or their protective end caps are removed. It can also result from incorrect cleaning. For example, using a dry paper wipe on a ceramic end face will easily build up ES.
Because fibre end faces are made from non-conductive materials such as plastic, ceramic, glass or epoxies, they act as an electrical insulator. As a result, the static charge has no place to go and so will remain indefinitely on the end face, attracting dust unless it is removed.
Although ES is problematic for all fibre networks, the threat is increased with new 5G technology, which often uses higher fibre count cables of up to 6,912 individual fibres. These densely packed higher fibre count cables make the end face connections particularly vulnerable to contamination and are typically harder to clean if specific processes are not implemented.
The construction and material composition of 5G networks can add further complexities regarding ES and contamination. 16-fibre arrays are replacing the traditional 12-fibre arrays. These multi-fibre connectors are required to ensure there is enough bandwidth to accommodate the next generation fibre networks. The problem is that the new fibre still uses the same 2.5mm x 6.4mm standard MT ferrule footprint. They are not only more condensed but they are made from 80% glass. Although glass helps improve thermal expansion control, it also retains more static than other types of connectors, making them ‘dust magnets’.
The end face shape is another contributor to the problem. Because most fibre end faces are designed with convex configuration to reduce back reflection, ES is concentrated at the contact region of the mated connector pair, pulling dust and contamination to the very area which is most vulnerable.
Incorrect Cleaning Can Be Problematic
The products that are supposed to stop damage to the fibre can also be a contributing problem. Removing manufacturer-installed protective end caps from a new end face connector can generate static and draw in dust contamination to the end face. Also, the cleaning tools used to install or maintain the fibre network can also add to the ES problem. For example, wiping an end face with a dry wipe or cleaning stick can create contact friction. Just like rubbing a balloon on your clothing, the dry wiping action creates a triboelectric effect that is difficult to dissipate.
Another common ES contributor is rapid air movement. For example, using compressed air or canned dusters during the cleaning and drying process can cause friction and create a triboelectric charge to the end face.
Remove the Threat of Electrostatic Charge Through Cleaning
To remove any ES and contamination from the fibre end faces and connectors, they must be cleaned using the correct tools and cleaning procedures. It is also important to follow standards like those set by the International Electrotechnical Commission (IEC). The fibre end face specification 61300-3-35 helps guide the fibre optic industry in identifying the types of contaminants on end faces and on how to remove them with a recommended three-step process of inspect, clean, inspect.
Wet to Dry Cleaning
Wet to dry cleaning is the most effective way to remove contamination and disperse any ES. This can be achieved by applying a small amount of high-purity static-dissipative cleaning fluid on the corner of a dry, lint-free, high-quality optical-grade wipe. Then, starting at the wet section, slowly swipe the end face towards the dry section of the wipe.
If using a cleaning stick, wet the tip of the stick directly from the dispenser cap of the can, or touch with a cleaning wipe moistened with cleaning fluid. Then insert the stick tip into the end face to clean.
It is important not to touch the wipe or stick tip with any clothing or skin, as small amounts of fibre or skin-oil will contaminate the cleaning tool, making it ineffective. Once the cleaning process is finished, it is crucial to inspect the end face to ensure all contaminants have been removed.
Static Dissipative Cleaning Fluid
Wet to dry cleaning using a specially engineered fluid with a low surface tension provides the static charge with a path to dissipate, making it easier to wipe away end face contamination.
To further reduce contamination risk, ensure the cleaning fluid is fast drying. This is particularly important as it helps to keep ambient moisture from being attracted to the fluid, and makes the cleaning process quicker.
Make sure the cleaning fluid is contained in hermetically sealed packaging. This helps keep the fluid ultra-pure and prevents it from absorbing airborne contaminants such as moisture, microscopic dust particles, exhaust particles from traffic, or pollen from plants, all of which can degrade the cleaning fluid’s effectiveness.
Clickers and Sticks
Only use high quality sticks and ‘click-to-clean’ tools when cleaning fibre. Do not use foam swabs as they can tear, leaving debris behind. They may also generate an electrostatic charge which will attract further dust contamination to stick to the end face.
Cleaning sticks are ideal for low fibre counts or when cleaning highly contaminated end faces. If using a cleaning stick, check it has been engineered to be non-linting and that it perfectly fits the end face configuration without having to disassemble the connector or adapter. Dampen the stick with cleaning fluid before inserting into the connector, then rotate in a clockwise direction, six to eight times. Only use one stick per end face to avoid any cross-contamination.
When cleaning high-density fibre like those found in 5G networks, a click-to-clean tool is a good option as its fast, effective, and designed to clean connectors with uneven geometries and convex configurations. When using a click-to-clean tool, apply a small amount of cleaning fluid to a wipe first, then touch the tool to the dampened wipe. Insert the tool into the port or end face and push the handle until the tool is fully engaged. It is important not to spray the cleaning fluid directly onto the end face or the tool itself.
Remove the Risk of Electrostatic Charge for Reliable Networks
Keeping today’s modern networks up and running and performing as they should is critical to connectivity. The pace of 5G coverage expansion across Europe is rising and will reach 70% in 2025 (from 47% in 2021). For 5G networks to effectively handle the increased demand, network providers must ensure their fibre is installed and maintained correctly. All connections must be perfectly clean for optimal performance and reliability.
Electrostatic charge threatens fibre optic network performance as it attracts dust particles to the end faces and locks them in place. This contamination affects the core of the fibre causing insertion loss and impacting network speeds. It is, therefore, important to eliminate ES through effective cleaning tools engineered specially for fibre optic cleaning, and processes that follow regulatory standards and procedures.
Those looking for help in cleaning and removing static from their fibre-optic end faces should seek the help of an experienced supplier that specialises in fibre cleaning to advise them on which cleaning fluids, tools and methods will work best for their 5G fibre networks.