A clean sweep for 5G

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Mike Jones looks at the 5G lottery and asks: 'Are you gambling with your fibre’s performance?' 

We know 5G is coming, but are we ready? This next generation of connectivity promises increased network capability, much faster speeds, higher data volumes and improved reliability. With connected devices thought to reach 75.441 billion worldwide by 2025, 5G connectivity will be a welcome arrival. It will, however, require forward-thinking from network providers, especially when it comes to fibre performance.  

5G networks will need to handle more data to seamlessly stream demanding bandwidth. This means network infrastructure must be in place to support the billions of devices and increasing amount of data. To ensure the promised capacity of 5G, it is essential that service providers implement cleaning procedures to guarantee system performance. These practices should be used not only on new installations but also on existing infrastructure. 

 
Easing the contamination threat 
The most common threat to an optical network is contamination on the optical interconnects. As each fibre is only slightly thicker than a human hair, the smallest speck of dust is detrimental to its signal path. Any contamination found on the core of the fibre – where the signal travels through – can cause back reflection, insertion loss and equipment damage. This will become even more apparent with the deployment of 5G, as every milliwatt of power will be required for faultless connectivity. 
 
End-face contamination is defined as a removable defect that negatively impacts the performance of mated connector pairs. This can include fingerprint oils, lint, moisture, exhaust fumes or simply dust. The main cause of dust-based contamination is connector ‘wear debris’. Wear debris dust is caused by the contact friction when connectors are mated. For example, from the connector slider, the retention clips in adaptors and transceivers, and also from the guide pins. Dust particles can be ground into the ferrule surface, resulting in scratched, pitted or scarred end-faces. 
Dust can result in scratched, pitted or scarred end faces
 
Although most contaminate is just several microns in size and only visible with a microscope, it can still introduce serious problems to networks and cause complete system failure. Contamination can block the light through the fibre, changing the index of refraction. If a fibre end face is contaminated, it will change the path of the signal through the fibre. If the contamination is very severe, the refraction angle can alter enough for the signal to be completely lost. This is particularly acute in dense wavelength division multiplexed (DWDM) fibre systems where, instead of passing just one wavelength of light along a fibre, multiple separate wavelengths are passed. The higher the frequency of the light, the greater its sensitivity to changes of the refractive angle. This means that modern, faster networks, like 5G, will be more vulnerable to contamination. 
 
Why clean new infrastructure?
It would be a mistake to assume that a new cable assembly will have a pristine connector end-face free of contamination. 5G will see the installation of huge amounts of new fibre, but this may not always come pristine and ready to use straight from the box. Many moulded plastic end-caps include chemicals called ‘plasticisers’, to improve the durability of the end-cap. Unfortunately, many plasticisers outgas, leaving small oil droplets on the end-face. Some manufacturers also use mould release agents to speed the manufacturing of the tiny end-caps. These endcaps may retain some of the mould release agent on the inner surface, which can transfer onto the connector end-face. 
End-caps are never cleaned and frequently have small amounts of dust inside the sleeve that can migrate onto the end-face. In addition, putting the end-cap on at the factory and removing it by the network installer can cause wear debris. 
 
The best practice to ensure that optical connectors are delivering the designed performance, is to inspect and clean both ends of the connector pair before they are mated. 
 
Choose your tools wisely 
Ironically, the products used to clean fibre can be their Achilles’ heel. Contamination from cleaning fluid, Isopropyl alcohol (IPA) is a common problem. Because IPA absorbs moisture from the air, it is extremely hygroscopic, so will attract water molecules, contaminating the liquid and reducing its ability to clean. As the IPA absorbs the water molecules in the local humidity, it also picks up microscopic dust particles, such as exhaust particles from traffic and pollen from plants, as well as all the absorbed minerals and salts. All of these contaminants will degrade the cleaning process. 
 
IPA is also slow-drying. Water trapped in the alcohol slows the drying process. This means more time is needed to evaporate the liquid from the end-face. Some engineers may use canned air to speed the cleaning and drying of the fibre, however, this increases the static charge (attracting more dust) and pushes the debris around the area being cleaned. 
 
Additionally, IPA is classed as a Volatile Organic Compound (VOC), and therefore has environmental implications. It is highly flammable, and many government regulations will not allow it to be air shipped. This can cause problems if a technician is required to fly or travel to remote areas and needs to transport cleaning consumables to the work site. When choosing a cleaning fluid, ensure that it has been specifically engineered for fibre optic connectors. It should include the key elements of being ultra-pure, residue-free, fast-drying, nonflammable, static-dissipative and hermetically sealed to prevent contamination. Also, look for cleaning fluid that meets strict regulatory and environmental standards. A fast-drying fluid is an especially desirable characteristic, as this keeps moisture from being attracted to the end-face, and therefore minimises contamination. There are many highly effective connector cleaning products on the market that will help to make the process quick and simple. 
 
Don’t take the gamble 
An extremely important point to make is that when cleaning, always inspect, clean and reinspect all the termini on both ends of a connector pair. As already established, contaminate is miniscule and cannot be seen with the naked eye. 
 
The inspection processes help to visually distinguish any contamination that can interfere or damage the surface of the optical termini. They also can identify permanent defects like scratches and pitting, all of which will affect the signal. 

 
By proactively implementing modern cleaning and inspection procedures, it will not only save time and money, but also make a network substantially more reliable. 
 
This will help to withstand the pressure on increasing connectivity demands. When it comes to 5G networks don’t gamble on connectivity, ensure modern fibre cleaning procedures are implemented. 
 
Mike Jones is vice president (international) for MicroCare 
 
1 https://www.statista.com/statistics/471264/iotnumber-of-connected-devices-worldwide/

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