The Perfect Connection

A few years ago, a cohort and I were demonstrating fiber optic terminations in our booth at the NECA show. He came back from visiting another booth with a large twist-on wire connector, commonly called a “Wire-Nut,” the Ideal trademark for these devices. He removed a half-inch of the jacket from the middle of a short fiber optic cable, carefully inserted a loop of the exposed fiber into the wire connector and filled it with epoxy. We then demonstrated this fiber optic Wire-Nut to visitors to our booth. It caused quite a lot of interest, especially among the other vendors showing fiber optic products, until they got the joke.

The perfect fiber optic connector, in most installers opinion, would install like a Wire-Nut or at least like a crimp-on modular connector used with UTP cabling. Cut, crimp and you are through in no time at all. Unfortunately, it is not that easy.

A good fiber optic connection requires very accurate alignment of the two hair-thin glass optical fibers. They must also have very finely polished ends so they mate precisely against each other to reduce loss and back reflection. You also need the connector to hold fibers firmly, so the fiber does not move when the connector is handled during mating or de-mating.

For that reason, most connectors use some type of ferrule to align the fibers and adhesive to hold the fibers in place. Then the ferrule is polished in a two- or three-step process. It is not hard or even that time-consuming, but you do have to deal with adhesives, polishing tools and films.

There is a simpler way, but it may not be faster or cheaper. It has had a mixed reputation for performance and reliability because some suppliers have downplayed the need for proper tools and training. This way is to use what is called a “prepolished/splice” connector.

The prepolished/splice connector is similar to a normal adhesive connector, except it has already had a short piece of fiber glued in the ferrule and polished at the factory. The factory polish guarantees a good end finish and low loss and reflectance at the mating surface. Inside the connector is a mechanical splice that mates to the other end of the fiber stub. Termination requires cleaving a fiber, just like for a splice, inserting it in the connector and fixing the fiber in place.

These prepolished/splice connectors usually have a higher loss than a plain adhesive connector because they have both a mating loss plus the loss of the internal splice. They are also more expensive than simple adhesive connectors, since they involve some fairly complex processing during manufacturing.

These connectors have been disappointing to some users because they were highly oversold. They were widely touted as being faster than adhesive connectors and much cheaper because labor costs were lower. And, because the steps involved in termination were fewer than adhesive connectors, training was quicker and simpler.

None of these claims are necessarily true. Sure, each connector was much quicker compared to an individual adhesive/polish connector, but if you totalled up the time needed, including set-up and clean-up times, testing, and retermination of failures, the savings were much less than expected. Downplaying training was a big mistake, as making a good termination with these connectors requires a good cleave, which takes practice and a good cleaver.

The cleaver—a tool that scores and breaks the fiber in a controlled fashion to produce a perfect end for splicing—is the key to these connectors. A good cleave will produce good terminations. Unfortunately, most manufacturers provide a simple, inexpensive cleaver in their termination kits.

This cleaver, which looks like a stapler, can produce good cleaves if the user is skilled and experienced in its use. But, as I said, most installers do not get properly trained. Many have problems with this tool and thereby problems with terminations.

There are several ways to improve the process. One is to get properly trained and to get lots of practice. Another is to use a better cleaver. Now some manufacturers offer better cleavers—the same ones used with expensive fusion splicers. They have two advantages: not only do they produce better cleaves, but they do it with less skill required.

Sure, these cleavers cost over $1,000, but when the connectors—which cost $10 to 15 each—and the labor costs are factored in, the better cleavers pay for themselves quickly in better terminations yield. Finally, some of these connectors can be optimized using a visual fault locator (VFL), which shows how good the splice is as you are making it.

If you want to try these connections, or if you are using them with less than ideal results, make an investment in a good cleaver, a VFL and some “real” training. Real training comes from an expert who teaches termination and makes you test every connector you make in training, so you learn from your mistakes. EC

HAYES is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at


About the Author

Jim Hayes

Fiber Optics Columnist and Contributing Editor
Jim Hayes is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at .

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