In any mated pair of fiber optic connectors, the cleanliness of both fiber endfaces 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 which 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:

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 a 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 afterwards 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 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 time of installation.   Many of these systems are designed specifically for installation and include the capability of viewing connectors after installed into an adapter.

The point being:  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, 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 a savings.

Additional resources from the FOC team include:

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Dan Rocheleau

About Dan Rocheleau

Dan Rocheleau, Business Development, Technical Sales Dan has worked in fiber optic cable assembly since 1986: starting as a part-time line operator for a local cable production company and working his way up through to management positions in large global companies. His experience includes positions in process training, supervision, product and process engineering, quality system development and management, factory general management, global factory startups, and global project management roles. He has held several overseas positions, opening and managing factories in Mexico, India, China, and Czech Republic. He has led global project efforts in sourcing / supplier auditing, global process standardization, and global operations strategic planning. Dan’s extensive experience gives him a unique ability to relate to our customer’s needs and challenges, helping Fiber Optic Center better help our customers continue to adapt and grow in the evolving and competitive fiber cable assembly market. Follow @TermExpert_FOC