The Dirty Side of the Industry: What to Know When Cleaning Optical Fibers

The cleanliness of fiber has always been a topic of primary importance in the Fiber Optic industry. From manufacturing to installation, precautions are taken along the way to keep fiber clean. With the demand and capabilities of fiber increasing, the importance of cleanliness is increasing as well, especially with the growing popularity of Dense Wavelength Division Multiplexing (DWDM) and its ability to support many wavelengths, each capable of transporting 100Gbit/s or more. A single imperfection can cause catastrophic failure, and the most common cause of loss and damage are contaminated connectors. 

Magic Dust

Have you ever wondered how is that brand new connector is dirty straight out of the packaging or how that fiber is dirty after you just cleaned it? To look at this dirty topic a little deeper, let’s think back to our school days. Most of us have seen the science experiment where the balloon attracts hair through static electricity. This is triboelectric charging, and it happens when friction occurs between the surfaces of different materials. This invisible magic trick happens every time that fibers or connectors are touched, even when you’re using that one-click or CLETO

Dust particles floating in the air are also susceptible to static charges and are commonly charged as the particles pass through an air conditioning unit. At this point, we all know opposites attract, and this can explain how that connector is somehow dirty after the dust cap was just pulled off or it was just cleaned. 

Think Small

We all know a dirty connection is bad, but it’s not always as easy as “clean and reconnect”. There is a lot happening at a microscopic level that only can be seen through a fiber scope or an end face inspection probe. With these tools we can see the fibers core that ranges 9 µm to 62.5 µm (µm=Micron/Micrometer). In comparison, a human hair is between 17 µm and 181 µm. When comparing the size of the core, which carries most of the signal, to other materials such as a hair (17-181µm), silica dust (1-100µm), or a skin flake (0.5-10µm), we can see how easy it is for the path to become obstructed. 

To go a little further, the spring in a Multi-fiber Push On (MPO) connector can exert as much as 20 N (Newtons) of force. 20 N is equal to 4.4961788774192 pounds of force. As the connectors are mated in a bulkhead, every dust particle caught in between the two connectors has that 4.5 lb. crushing it between the surfaces of each connector. This force can easily cause particles to explode into several smaller particles, and sometimes more resilient particles can even scratch, pit or even shatter the ends of fibers, making them unusable. Don’t forget that most fiber test equipment has vulnerable connectors as well. Damaging these could lead to costly repairs, equipment down time, and false results. 

ABCs

So, if static electricity is turning the fiber into a particulate magnet, attracting all the nasties we don’t want, how do we prevent these microscopic obstructions and/or damage? It’s simple, we sing the ABC’s: Always Be Cleaning. The most common method of cleaning fiber is to use 99% isopropyl alcohol (IPA) and a lint-free wipe. But there are a few things you should know about that IPA before you pick more up. IPA has hygroscopic (the characteristic of tending to absorb moisture from the air) properties. A bottle of 99.9% IPA that is opened and exposed to the air can lose 7% of its strength within 15 minutes. As IPA evaporates, it also absorbs moisture and other contaminants in the air. So, your IPA in that refillable pump bottle is no longer 99.9% IPA, but a diluted IPA contaminated with all the nasties from the air. Also, IPA doesn’t dissolve oils, instead only lifting the oils from the surface. So, without following the wet clean with a dry clean, the oils can resettle or spread. The friction of cleaning is also imparting triboelectric charging to the fiber. What a conundrum.

Dr. Frankenstein

If only we could clean fiber without turning it into a magnet or contaminating it... What, we can? Some mad scientists have developed several fiber optic cleaning solutions that can aid us in this war on grime. These products are very effective in many situations. They come in hermetically sealed pump bottles that eliminate evaporation and contamination as the cleaner is sealed inside the bottle. They also have antistatic agents that reduce the attraction of dust particles. They dry faster, reducing the chance of an arc flash in a splicer. What’s that, these solutions aren’t flammable? So that also means they’re not Hazardous Material (HAZMAT) items, which also means easier storage and cheaper shipping.