Fiber Optic Installation and Cleanliness: It Counts

In any mated pair of fiber optic connectors, the cleanliness of both fiber end faces plays a major role in the performance of the mated pair. Obviously and intuitively, anything that prevents light from passing freely from one fiber into the other (such as dirt, grime, oil, scratches, cracks & etc.) is going to reduce performance. This is well known, or at least should be, to anyone installing any part of an optical network that includes optical connector interfaces. Mating a clean ferrule end-face to a contaminated ferrule end-face can only result in two contaminated end-faces and a very good chance of permanently damaging/scarring the smooth glass end-face of both. Cleanliness, as we know, counts.  Luckily we have a library on clean fiber connections that include:

• What Causes Poor IL/RL?
• Ensuring Clean Fiber Connections
• The art of cleaning: Follow these specific cleaning techniques during fiber optic cable assembly manufacturing and installation

In nearly all installation situations—-in a patch-bay on an equipment rack, in a termination junction box, on the faceplate of electronic equipment—-access to one of the connectors of any mated pair is very limited.  If this “back-side” connector end-face is contaminated, it is very difficult (and sometimes impossible) to have access to remove the connector for cleaning. This makes it even MORE important to ensure that these connectors, when installed, are in as clean and pristine a state as possible.

To that end, when planning and purchasing cable assemblies for any installation,  it’s recommended to verify from your supplier that they provide connector end-faces that meet or exceed industry standards on end-face cleanliness (for example, IEC 61300-3-35).  If your supplier cannot ensure or suggests an increase in cost is needed in order to meet such standards, you might want to consider a new supplier—–meeting these standards is common industry practice and not difficult to achieve. Almost all manufacturers I’ve dealt with abide by such standards—certainly all the “big names” but it’s always good to include a requirement in your purchase contract or supplier drawings that such standards are adhered to.

When a manufacturer inspects an end-face, it is immediately capped afterward with a plastic dust cap, and (theoretically) this dust cap is never removed again until immediately before it is plugged into its final installation location by the installer. In theory, this ensures connectors will be sufficiently clean for installation. However, there are a number of ways in which the end-face can (and do) become contaminated along the way:

• When installing the dust cap, the manufacturer accidentally touches the end-face with the dust cap itself, leaving plastic mold-release grease or other contamination. Since the dust cap is never removed again by the manufacturer, it’s impossible to detect this.
• In some poorly designed dust caps, the interior surface dimensions are such it permits contact with the end-face it is trying to protect, usually leaving a super-contaminated end-face.
• During installation, dust caps are removed prematurely, while cables are still being organized/routed, and the end-face is exposed, and prone, to contamination.

So, even though you can have confidence that your cable assembly is providing clean end-faces, it is always highly recommended to visually inspect the connector end-faces at the installation site, immediately prior to installing into any adapters. This should be common practice by any respectable installer. There is a plethora of very good and reasonably-priced portable, lightweight inspection systems available on the market today—many of which can easily store the inspection images for documented assurance of the end-face condition immediately at the time of installation. Many of these systems are designed specifically for installation and include the capability of viewing connectors after being installed into an adapter.

The point is: If you are an installer, or planning an installation, of fiber optic cable assemblies —-keep in mind the cost and pain that can be (and almost always IS) involved in re-cleaning a connector after installation. Avoiding system testing delays, degradation of system performance, and potential connector damage is worth the small investment of the simple preventive action of inspection during installation. Having this equipment always on hand to inspect prior to ANY connector mating is necessary and will end up as savings.
 

Additional resources from the FOC team include:

• Category Resource FOC Installation Page
• View the Glossary, Acronyms, Military Specifications for Connectors
• Q&A Resource: email technical questions to AskFOC@focenter.com

Have questions about this article?

Contact FOC with questions at: (800) 473-4237 / 508-992-6464 or email: FiberOpticCenter@focenter.com and we will respond ASAP.