This is part two of a three part series on fiber cleaning. For part one, click here.
From the August, 2014 Issue of Cabling Installation & Maintenance Magazine
By Sean Sheedy
Amazingly, cleaning was a problem in the earliest fiber installations, more than 40 years ago, and is still the primary operational problem in the industry today. Are we all a bit slow on the uptake here? Companies need to refocus their efforts to properly clean every endface, both sides, every time they touch their connectors.
It is absolutely essential the bare fiber be perfectly clean before inserting into a ferrule during connectorization. Here the operator is preparing to clean with a high-quality lint-free wipe that does not contain any glues or cellulose. The cleaning fluid evaporates quickly and the canister cannot be refilled, which ensures the cleaning fluid will remain pure and uncontaminated.
Cleaning tools: Good, bad, ugly
Let's take a look at the tools we give our techs. Usually it is a box of cellulose wipes and a pump bottle of isopropyl alcohol. What's wrong with these time-proven choices? Almost everything.
The lint-free wipe needs to be truly lint-free. Many wipes are made of cellulose, held together with glue (called "binders" in the paper trade). Cellulose fibers are weak and shred easily. The glues that hold the paper together are dissolved by liquids such as water and alcohol, so glue often leaches out onto fiber surfaces. So while you may have removed that pesky fingerprint from the endface, now you have left other residues on the endface that may be just as much of a problem as the original dirt.
A related issue develops when companies buy their techs high-quality wipes, but because these wipes are more expensive the operators don't dispose of them after each use. As they said in Apollo 13, "Houston, we have a problem." Wipes should never be re-used, because contamination migrates. So in this situation, the techs simply are moving the dirt from one fiber to another.
Back to the question of cleaning with alcohol: The cleanliness, performance, and packaging of the liquid used to dampen the lint-free wipe are crucial. Isopropyl alcohol (IPA) has been a very popular cleaning choice used in both the termination and splicing of fiber. It has many good characteristics; it's inexpensive, it dissipates static, it does not freeze, it's safe for people and it's very gentle.
However, the original Bell Labs specification was for water-free "reagent-grade" alcohol, which is far more pure and more expensive than the diluted isopropanol found in drug stores. IPA of this quality is far more pricy than drug-store IPA, and it also is very hard to find outside of laboratory-supply distributors. This means most alcohol being used on fiber today is not reagent grade and generally is too dirty to properly clean fiber surfaces. So if you are planning to use IPA, get high-quality, water-free IPA.
An essential element in the cleaning process is to inspect every endface, both sides, after cleaning. Here the operator has installed a new connector on the fiber-optic cable and is inspecting with a simple, handheld scope. Every technician who touches any fiber must be equipped with at least a low-power inspection scope.
In addition, today's high-powered lasers can bake trapped moisture (and other residues) left on connector surfaces. Very often this creates additional reflectivity in the network and can be blinding to the transmitting devices. For the very best results, technicians should be provided cleaning liquids in spill-proof, non-refillable containers so the pristine cleaning fluid is not contaminating with dirty packaging. Lastly, modern cleaning fluids, unlike drug-store IPA, have a very quick evaporation rate. A brisk rate of evaporation allows techs to work faster, and makes it almost impossible for any residual fluids to be trapped inside alignment sleeves or baked onto an endface.
About the Author
Sean Sheedy has worked for more than 20 years as a fiber-optic installer, troubleshooter, system designer, emergency-restoration technician inspector, project manager, sales manager, and consultant. He holds 30 industry-related certifications and is a certified instructor with The Fiber Optic Association and The Electronics Technicians Association. He has also developed and teaches fiber optic/copper communications installation and troubleshooting training courses. His experience includes work in all divisions of the military, various government agencies, federal and state prisons, as well as the commercial markets. He can be reached at firstname.lastname@example.org.