By Jay Tourigny
Contamination is the root cause of many optical-fiber network problems. Performance often suffers when fiber connections are exposed to even the smallest amount of contamination. This does not bode well in today’s highly connected world. Every milliwatt of power and gigabit of data is critical to form a robust 5G network that can deliver faster speeds and greater bandwidth with lower latency.
So how do you ensure contaminant-free fiber connections? Do you employ the traditional method of using isopropyl alcohol (IPA) or opt for modern specially engineered cleaning fluid? Let’s look at the case for each.
To compare the different cleaning fluids, it is important first to understand the contamination encountered. Contamination comes in all guises, but the most common is simple dust. Dust-based contamination originates from two main sources, wear-debris and through the environment.
Dust created from connector-wear debris is the most common source of contamination. The contact friction generated when connectors mate creates contaminants. SC and MPO connectors have sliding housings that hold in place, using latches in the adapter. Other connector systems, like the ST, FC, and many of the hardened connector systems, have threaded metal housings and use orientation keys. All of these connectors rub together each time they mate and generate microscopic particles of dust and debris.
Another source of wear debris comes from protective end caps. End caps used on brand new jumpers and patch cords, even those straight out of the packet, are not contaminant-free. Most are not cleaned at the factor before packaging, so dust and other leftover manufacturing debris is typically trapped inside the sleeve and migrates to the endface when the endfaces are connected. Outgassed plasticizers from the protective endcaps’ plugs can also leave a haze of small droplets of oil on the endfaces.
Environmental or airborne dust is also a cause of fiber endface contamination. It can come from skin cells, hair, plant pollen, vehicle emissions, cardboard boxes and clothing lint. Ironically, it can also come from the very items used to clean the fiber endfaces. From swabs, paper-based wipes, and the cross-contaminated cleaning fluids that some installers use to clean their optical connectors can amplify the problem.
Mold release agents can also leave contaminants behind. Some fiber cable manufacturers use these to more readily remove the endface cap or housing from their molds during manufacturing. Leftover release agent inside the endcaps can transfer to the connectors.
The smallest speck of dust or bread of oil can bring a fiber network down. If not removed, the dust particles grind into the ferrule surface, resulting in scratched, pitted or scarred endfaces. Residue like oil can obscure and block or change the signal’s path. If the contamination is severe, the refraction angle can change enough that the signal is completely lost. Unless connections and splices are kept perfectly clean, problems like insertion loss (weakened signal), back-reflection (signal is diverted back to its source) or a total system shutdown are the resulted. New 5G networks with their higher frequency are more sensitive to changes of the refractive angle, making them especially vulnerable to these contaminants.
When it comes to fiber cleaning fluids two are most commonly used: IPA and engineered cleaning fluids. Let’s look at IPA first. IPA has many names and can also be listed on safety data sheets as isopropanol, rubbing alcohol, propan-2-ol, and 2-propanol or dimethyl carbinol.
So what are the benefits of IPA? Price and availability are the main advantages. It is inexpensive to make and easy to purchase from a variety of sources. Because IPA has been the “standard” cleaning fluid for fiber technicians for decades, many companies still think of IPA as the go-to fluid for cleaning fiber.
But does IPA clean effectively? Not really. IPA is hygroscopic, meaning it attracts water molecules from the air. As the IPA absorbs the water molecules, even at low relative humidity, it also picks up microscopic dust particles. This can include exhaust particles from traffic or pollen from plants, as well as all the absorbed minerals and salts. This contaminates the IPA and degrades its ability to clean.
Water trapped in the alcohol also slows the drying process. This means it evaporates slowly from the endfaces, slowing cleaning time. To speed up the drying process, some technicians may use canned air on the fiber endface, but this practice is not recommended. Canned air, or air dusters, create a static or triboelectric charge on the endface, which attracts dust. It also pushes the debris around the area on the endface being cleaned.
IPA is also highly flammable and has a high vapor pressure, making it dangerous to use in areas where there are flames or sparks. It also requires special handling and storage. Most alcohol-based cleaning fluids are regulated as hazardous materials and cannot easily be shipped by air. This makes shipping or transporting IPA to a remote jobsite problematic and expensive.
Finally, IPA is difficult to keep clean and uncontaminated between uses. It is usually not stored in hermetically sealed containers. This means the fluid is exposed to dust and humidity in the work area, which could draw in moisture and cross-contaminate the cleaning fluid. There is also the risk of accidental spillage, a dangerous hazard due to its extreme flammability, if the IPA isn’t in a sealed container.
Engineered cleaning fluids
It is fair to say that the disadvantages of IPA far outweigh the benefits. Fortunately, there are alternative fluids that fill the fiber cleaning void. Unlike IPA, a high-quality ultra-pure optical-grade fiber-optic cleaning fluids are engineered to clean better, dry more quickly, are static-dissipative, and will not leave a residue on the endface.
Wet-dry cleaning using engineered cleaning fluids is one of the most effective methods to clean fiber endfaces. Unlike IPA they are not hygroscopic and do not absorb impurities through moisture in the air. This helps prevent cross-contamination and helps ensure a better clean. Engineered fiber cleaning fluids are also static-dissipative, which helps eliminate the surface static that attracts dust to endfaces or fiber slices.Engineered cleaning fluids are also fast-drying. In fact, they are eight times faster at drying than IP, making the overall cleaning process quicker to complete. Plus, they do not leave a haze behind that can cause possible insertion loss or faulty signal transmission as they dry.
Optical-grade cleaning fluids are also non-flammable, which is a huge benefit over IPA. They can be transported with ease and stored and used without the hazards associated with IPA. Furthermore, they typically come in a hermetically sealed package. This not only keeps the fluid pure and free from any contaminant, but also helps ensure the cleaning fluid does not spill or leak if tipped over. The sealed container typically delivers the cleaning fluid in a metered dose via a dispenser cap. This also helps control fluid waste and limits installer exposure to the fluid.
Perhaps the one drawback of engineered fiber cleaning fluids when compared to the IPA is the price. When compared to each other, IPA will always be the cheaper option. However, IPA does not clean as effectively or as quickly. If fiber networks are not cleaned thoroughly, and contamination is left on the fiber endfaces, the network could be compromised, causing intermittent signal interruption or a complete network shutdown. Cleaning-related network problems usually result in costly callbacks and technicians spending more time cleaning and replacing fiber. So IPA may be a cheaper alternative, but the long-term costs are substantial.
Which one wins?
Reliable fiber networks call for reliable cleaning with the most effective cleaning fluids. To achieve the best results, avoid IPA and select an engineered cleaning fluid instead. Choose one that is fast-drying to speed the cleaning process and that will not attract moisture, and the contaminants it harbors, to the endfaces or splices. For safety and ease of transport, ensure the cleaning fluid is non-flammable and classified as non-regulated and non-hazardous. In addition, choose an engineered cleaning fluid that comes packaged in a hermetically sealed container. It will keep the cleaning fluid fresh and pure between uses and prevent spills and fluid waste.
When choosing fiber-optic cleaning fluids, tools and methods, network installers should seek the help of an experienced supplier that specializes in fiber cleaning to advise them on which cleaning process will work best for their fiber networks.
Jay Tourigny is senior vice president at MicroCare, LLC, which offers Sticklers brand fiber cleaning solutions. He has 30 years’ experience in the industry and holds numerous U.S. patents for cleaning-related products that are used in fiber-optic, medical, and precision cleaning applications.